Article

Muscle Activation and Strength in Squat and Bulgarian Squat on Stable and Unstable Surface

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Abstract

The aim of the study was to compare muscle activity using the same relative resistance in squats and Bulgarian squats on stable and unstable surface. Muscle strength and activity were assessed by 6-repetition maximum and concomitant surface electromyography. A cohort of 15 resistance-trained males performed the exercises on the floor or a foam cushion in randomized order. The muscle activity was greater in biceps femoris (63-77%, p<0.01) and core muscle external obliques (58-62%, p<0.05) for the Bulgarian squat compared to regular squats, but lower for rectus femoris (16-21%, p<0.05). Only Bulgarian squat showed differences concerning the surface, e. g. the unstable surface reduced the activation of erector spinae (10%, p<0.05) and biceps femoris (10%, p<0.05) compared to a stable surface. There were similar activations in the vasti muscles and rectus abdominis between the different exercises (p=0.313-0.995). Unstable surfaces resulted in a load decrement of 7% and 10% compared to stable surfaces (p<0.001). In conclusion, the squat was somewhat favorable for the activation of agonists, whereas Bulgarian squat was advantageous for the antagonist and somewhat for core muscles. Bulgarian- and regular squats complement each other, and it may be useful to include both in a periodized resistance training program.

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... In squats, greater (4,6) or similar (2,34,38,43) sEMG amplitude in the core muscle has been demonstrated using an unstable surface compared with a stable surface (2,4,34,43). However, performing squats on balance discs, BOSU balls, or wobble boards (major stability requirements) exceeds the stability requirements in sports or daily-living activities. ...
... In squats, greater (4,6) or similar (2,34,38,43) sEMG amplitude in the core muscle has been demonstrated using an unstable surface compared with a stable surface (2,4,34,43). However, performing squats on balance discs, BOSU balls, or wobble boards (major stability requirements) exceeds the stability requirements in sports or daily-living activities. ...
... However, only a limited number of studies have compared core muscle sEMG amplitude in free-weight exercises with training machines (4,38). Furthermore, it is generally accepted that large stability requirements in resistance exercises (i.e., using unstable surfaces) reduce the force output significantly and to a greater extent than moderate stability requirements (2,5,8,33). External loading is of significant interest for morphological adaptations (16,22). ...
Article
Saeterbakken, AH, Stien, N, Pedersen, H, and Andersen, V. Core muscle activation in three lower extremity with different stability requirements. J Strength Cond Res XX(X): 000-000, 2019-The aim of the study was to compare core muscle surface electromyography (sEMG) during 3-repetition maximum (3RM) and the sEMG amplitude in the turnover from the descending to ascending phase in leg press, free-weight squats, and squats using the Smith machine. Nineteen women with 4.5 (±2.0) years of resistance training were recruited. After one familiarization session, the subjects performed 3RM in randomized order measuring electromyographic activity in the rectus abdominis, external oblique, and erector spinae. The exercises with the lowest stability requirements (leg press) demonstrated 17-59% and 17-42% lower core muscle sEMG amplitude than free weights and the Smith machine, respectively. No statistically significant differences were observed between the Smith machine and free weights. No statistically significant differences in turnover sEMG amplitude in the rectus abdominis between the exercises was observed, but lower sEMG amplitude was observed in external oblique and erector spinae in leg press compared with the other exercises. The 3RM loads in leg press were 54 and 47% greater than squats using the Smith machine and free weights, with 5% greater loads with the Smith machine than with free weights. In conclusion, lower mean and turnover core muscle sEMG amplitude were observed with the leg press but greater 3RM loads compared with squats with the Smith machine and free weights. The authors recommend that resistance-trained individuals use squats to include the core muscles in the kinetic chain, but there is no evidence that greater stability requirements (free weights instead of the Smith machine) will result in greater core muscle sEMG amplitude.
... Different approaches have recently been proposed to increase core muscle activation during traditional resistance exercises. One of those is to perform exercises unilaterally instead of bilaterally (1,2,8,13,14). Theoretically, when per- forming an exercise unilaterally, the contralateral side has to increase muscle activation to avoid postural sway due to the increased torque in the trunk created by the external load. ...
... In contrast to our hypothesis, there were no differences between exercise and side in the lower erector spinae when analyzing the whole set or different phases of the movement. Earlier studies have found differences in the lower back muscles when comparing unilateral and bilateral exercises (1,2,13). They have, however, used different location of the electrodes. ...
... Because the external load is identical in both conditions, the demand for extension and stabilization would be similar, which could explain the lack of difference in muscle activation between both exercises. Furthermore, the lack of significant difference in neuro- muscular activity of the external oblique is also in contrast with our hypotheses and to earlier studies examining core muscle activation during unilateral and bilateral executions of strength exercises of the leg, shoulder, and chest muscles (1,13,14). These previous studies demonstrated an increased activation of the contralateral side when performing the exercise unilaterally instead of bilaterally. ...
Article
The aim of the study was to compare the electromyographic activity of rectus abdominis, oblique external, lower and upper erector spinae at both sides of the truncus in one- and two-armed kettlebell swing. Sixteen healthy men performed ten repetitions of both exercises using a 16 kg kettlebell in randomized order. For upper erector spinae, the activation of the contralateral side during one-armed swing was 24% greater than the ipsilateral side during one-armed (p < 0.001) and 11% greater than two-armed swing (p = 0.026). Further, the activation in two-armed swing was 12 - 16% greater than for the ipsilateral side in one-armed swing (p < 0.001). For rectus abdominis; however, 42% lower activation of the contralateral side was observed during one-armed swing compared to ipsilateral sides during two-armed swing (p = 0.038), and 48% compared to the ipsilateral side during one-armed swing (p = 0.044). Comparing the different phases of the swing, most differences in the upper erector spinae were found in the lower parts of the movement while for the rectus abdominis the differences were found during the hip extension. In contrast, similar muscle activity in lower erector spinae and external oblique between the different conditions were observed (p = 0.055 - 0.969). In conclusion, performing the kettlebell swing with one arm resulted in greater neuromuscular activity for the contralateral side of the upper erector spinae and ipsilateral side of the rectus abdominis, and lower activation of the opposite side of the respective muscles.
... [10][11][12] Yet, few studies exist that have compared force output and muscle activity between bilateral and unilateral squats. [12][13][14][15][16] In addition, these studies comparing bilateral with unilateral squats have used different protocols for both conditions (split legs and rear foot elevated) and different loads between bilateral and unilateral squats, and neither of these studies compared unilateral squats without any support on the rear leg with bilateral squats. During modified squats (i.e. ...
... This is also visible in lesser EMG activity of the vastus medialis during the ascending phase in the unilateral squats with the foot backwards. The speculation is supported by previous studies 15,35 examining the effects of greater stability requirement (i.e. reduced base of support or unstable surfaces). ...
... Previous studies have demonstrated decreased prime mover activations if the muscle or muscle groups have both to stabilize and maximize force production compared to more stable exercises. 15,35 Finally, McCurdy et al. 16 used females in contrast to present study. ...
Article
Purpose/background: Bilateral squats are commonly used in lower body strength training programs, while unilateral squats are mainly used as additional or rehabilitative exercises. Little has been reported regarding the kinetics, kinematics and muscle activation in unilateral squats in comparison to bilateral squats. Therefore, the purpose of this study was to compare muscle activity, kinetics, and barbell kinematics between unilateral and bilateral squats with the same external load per leg in experienced resistance-trained participants. Methods: Fourteen resistance-trained males (age 23 ± 4years, body mass 80.5 ± 8.5kg and height 1.81 ± 0.06m) participated. Barbell kinematics and surface electromyography (EMG) activity of eleven muscles were measured during the descending and ascending phase of each repetition of the squat exercises. Results: Total lifting time was longer and average and peak velocity were lower for the bilateral squat (p<0.001). Furthermore, higher muscle activity was found in the three quadriceps muscles, biceps femoris (ascending phase) and the erector spinae (ascending phase) in the bilateral squat, while greater activation for the semitendinosis (descending phase) (p=0.003) was observed for the unilateral squat with foot forwards. In the ascending phase, the prime movers showed increased muscle activity with repetition from repetition 1 to 4 (p≤0.034). Conclusions: Unilateral squats with the same external load per leg produced greater peak vertical ground reaction forces than bilateral squats, as well as higher barbell velocity, which is associated with strength development and rate of force development, respectively. The authors suggest using unilateral rather than bilateral squats for people with low back pain and those enrolled in rehabilitation programs after ACL ruptures, as unilateral squats are performed with small loads (28 vs. 135 kg) but achieve similar magnitude of muscle activity in the hamstring, calf, hip and abdominal muscles and create less load on the spine. Level of evidence: 1b.
... The unstable Bulgarian squat and the regular back squat over six maximum repetitions were the free-weight exercises with the highest EMG activity (~210% MVIC) [30]. ...
... All parts of the feet are in contact with the floor. This exercise may vary depending on specific protocols (e.g., back squat on unstable surfaces, on Smith machine, different loads, or half-squat) [28,30,38,44,48,53,69,74,77,83]. ...
... Then, the barbell is placed behind the neck. The aim of the exercise is to lower the load by squatting with the front leg [30]. ...
Article
Full-text available
The aim of this study was to systematically review the current literature on the electromyographic (EMG) activity of six core muscles (the rectus abdominis, the internal and external oblique, the transversus abdominis, the lumbar multifidus, and the erector spinae) during core physical fitness exercises in healthy adults. A systematic review of the literature was conducted on the Cochrane, EBSCO, PubMed, Scopus, and Web of Science electronic databases for studies from January 2012 to March 2020. The Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines were used. The inclusion criteria were as follows: a) the full text available in English; b) a cross-sectional or longitudinal (experimental or cohorts) study design; c) the reporting of electromyographic activity as a percentage of maximum voluntary contraction (% MVIC), millivolts or microvolts; d) an analysis of the rectus abdominis (RA), transversus abdominis (TA), lumbar multifidus (MUL), erector spinae (ES), and the internal (IO) or external oblique (EO); e) an analysis of physical fitness exercises for core training; and f) healthy adult participants. The main findings indicate that the greatest activity of the RA, EO, and ES muscles was found in free-weight exercises. The greatest IO activity was observed in core stability exercises, while traditional exercises showed the greatest MUL activation. However, a lack of research regarding TA activation during core physical fitness exercises was revealed, in addition to a lack of consistency between the studies when applying methods to measure EMG activity.
... In this vein, a progression in load has been the ideal strategy for increasing muscular demands, but, in recent years, unstable environments have also been used with similar purposes [2][3][4]. Thus, different unstable devices have been used to enhance the effects of several exercises on muscle activation, force production, motor control, and consequently, athletic performance [1,5,6]. The design of these devices is intended to alter the relationship between the base of support, the body's spatial position, and the athlete's ability to maintain balance during the execution of a task. ...
... Which muscles are more demanded, and which are worked less when squatting? To address these questions, several studies have been conducted to assess the impact of instability on muscle activation during the execution of a squat [2,3,6,9,10]. As examined by Behm and Anderson [1], several authors have reported decrements of muscle activity of the primary squat movers under unstable conditions [3,6]. ...
... To address these questions, several studies have been conducted to assess the impact of instability on muscle activation during the execution of a squat [2,3,6,9,10]. As examined by Behm and Anderson [1], several authors have reported decrements of muscle activity of the primary squat movers under unstable conditions [3,6]. Specifically, McBride et al. [3] showed higher muscle activity of the vastus lateralis and biceps femoris under stable conditions (floor vs inflated disc) in three different loaded-squats in recreationally resistance-trained men, and Andersen et al. [6] found non-significant differences between stable and unstable squat conditions (foam) in the rectus femoris and both vastus muscles in males with a background in strength training. ...
Article
Full-text available
This study aimed to understand the acute responses on the muscular activity of primary movers during the execution of a half-squat under different unstable devices. Fourteen male and female high-standard track and field athletes were voluntarily recruited. A repeated measures design was used to establish the differences between muscle activity of the primary movers, the body centre of mass acceleration and the OMNI-Perceived Exertion Scale for Resistance Exercise (OMNI-Res) in a half-squat under four different stability conditions (floor, foam, BOSU-up and BOSU-down). A significant correlation was found between the highest performance limb muscle activity and body centre of mass acceleration for half-squat floor (r = 0.446, p = 0.003), foam (r = 0.322, p = 0.038), BOSU-up (r = 0.500, p = 0.001), and BOSU-down (r = 0.495, p = 0.001) exercises. For the exercise condition, the half-squat BOSU-up and BOSU-down significantly increased the muscle activity compared to half-squat floor (vastus medialis: p = 0.020, d = 0.56; vastus lateralis: p = 0.006, d = 0.75; biceps femoris: p = 0.000-0.006, d = 1.23-1.00) and half-squat foam (vastus medialis: p = 0.005-0.006, d = 0.60-1.00; vastus lateralis: p = 0.014, d = 0.67; biceps femoris: p = 0.002, d = 1.00) activities. This study contributes to improving the understanding of instability training, providing data about the acute muscular responses that an athlete experiences under varied stability conditions. The perturbation offered by the two BOSU conditions was revealed as the most demanding for the sample of athletes, followed by foam and floor executions.
... Cosio-Lima et al. 's study [15] showed that after 5 weeks of sit-up and back extension unstable training (Swiss ball) in untrained college women, muscle activity of rectus abdominis and erector spinae significantly increased compared to that of a control group. Furthermore, some evidence of this has been found in lower body exercises such as standard lunges [16] and Bulgarian squats [17]. Concretely, performing standard lunges and Bulgarian squats involves the activation of the gluteus maximus and medius, vastus medialis, vastus lateralis, rectus femoris, biceps femoris, semitendinosus, and gastrocnemius [18,19]. ...
... Regarding the effects of unstable conditions in the lower body, only Andersen et al. [17] examined the effect of performing a standardized Bulgarian squat (6-RM loaded) under stable (front leg on the floor) and unstable (front leg on a foam cushion) conditions on the hip and thigh muscles of healthy trained participants. Bulgarian squats significantly increased the activation of biceps femoris under stable conditions compared to those under unstable conditions (stable vs. unstable: 215.5 ± 106.7% MVIC vs. 193.3 ...
... For the biceps femoris, the activation was moderate; in the gluteus medius, the activation was high; and in the vastus medialis and vastus lateralis, the activation was very high among the conditions. As reported in previous studies, the vastus medialis and lateralis achieved a higher, but non-significant, very-high activation during a 6-RM Bulgarian squat compared to the unstable Bulgarian squat [17]. The study conducted by Mausehund et al. [54], in healthy and moderate strengthtrained students, indicated that the activation of the vastus lateralis was higher, but not significant, for the 6-RM Bulgarian squat than for the 6-RM split squat and single-leg squat, even though both exercises registered a very high level of activity. ...
Article
Full-text available
Practitioners of strength and conditioning are increasingly using vibration and unstable environments to enhance training effects. However, little evidence has been found comparing the use of suspension devices and vibratory platforms used in the Bulgarian squat. The purpose of this cross-sectional study was to examine the effect of suspension devices (TRX ®), unstable surfaces (BOSU ®), and vibration plates on muscle activity and force during the Bulgarian squat. Twenty physically active male students (age = 24.40 ± 3.63 years) performed a set of five repetitions of Bulgarian squats, suspended lunges, suspended lunges-BOSU, suspended lunges-Vibro30, and suspended lunges-Vibro40 (vibration 30 Hz or 40 Hz and 4 mm of amplitude). A randomized within-subject design was used to compare leg muscle activity, vertical ground reaction forces, and force exerted on the strap across the five exercises. Results showed no significant differences in muscle activity between the Bulgarian squat and suspended lunge (p = 0.109, d = 2.84). However, the suspended lunge significantly decreased muscle activation compared to the suspended lunge-BOSU (p = 0.012, d = 0.47), suspended lunge-Vibro30 (p = 0.001, d = 1.26), and suspended lunge-Vibro40 (p = 0.000, d = 1.51). Likewise, the Bulgarian squat achieved lower activity than the suspended lunge-Vibro40 (p = 0.010, d = 0.96). The force on the strap significantly decreased in the suspended lunge-BOSU compared to the suspended lunge-Vibro30 (p = 0.009, d = 0.56). The suspended lunge achieved higher front leg force production than the Bulgarian squat (p = 0.006, d = 0.48). In conclusion, leaning the rear leg on a suspension device does not provoke an increase in the activation of the front leg during the Bulgarian squat but increases the vertical ground reaction forces. Thus, the use of unstable surfaces or vibration plates for the front leg increased muscular activity when performing a suspended lunge.
... In its purest form, instability integrated via training unilaterally appears to increase activation of antagonist musculature (V. Andersen et al., 2014), which could be interesting for similarity during a skiing turn (Hintermeister et al., 1995). However, some investigations have reported reduced muscular activation of the agonist (i.e., increasing the relative contribution of the antagonist) (McBride, Cormie, & Deane, 2006), and almost all studies report impaired force production relative to the stable alternative (V. ...
... However, some investigations have reported reduced muscular activation of the agonist (i.e., increasing the relative contribution of the antagonist) (McBride, Cormie, & Deane, 2006), and almost all studies report impaired force production relative to the stable alternative (V. Andersen et al., 2014;Behm, Anderson, & Curnew, 2002;Drinkwater, Pritchett, & Behm, 2007;McBride et al., 2006). ...
Thesis
Full-text available
The literature characterizing force production during skiing, and the associated capacities of skiers, is complicated to synthesize due to ageing results or relatively unspecific assessments. The overarching aim of this doctoral thesis was to clarify the importance of force-output for skiing and of specific force-production capacities for different disciplines. The thesis comprised two themes: 1) characterizing the force-output of skiers (N=15) on a giant-slalom course using kinematic and kinetic data from a global positioning system and boot-mounted force-platforms, respectively; and 2) measurement of dynamic and isometric force, the effect of countermovement on force production at different velocities, and specific strength-endurance across disciplines, and performance levels, in national skiers (N=31) and sprinters (N=30, for comparisons). The conclusions from Theme 1 were that radial force-output applied to turn the skis was linked with performance (R2=0.31–0.68, p<.032), and depended on both total magnitude and the ability to apply the force effectively (β=0.63–1.00, p<.001). A high total force magnitude was associated to high force production by both the outside and inside limbs (β=0.92–1.00 and 0.631–0.811, respectively, p<.001). For Theme 2, athletes from speed and technical disciplines displayed different dynamic and isometric force qualities, with the former showing superior dynamic force at low velocities (ω2=0.17, p<.001) and in isometric conditions (ω2=0.16–0.22, p<.003). Overall, performance was linked with a more force-dominant profile (ω2=0.34; r=-0.60– -0.67, p<.001) and increased rate of force development characteristics (r=-0.50– -0.82, p<.048). Robust associations existed between maximum isometric force and speed discipline performance (r=-0.88, p<.001), but tended to be for technical athletes (r=-0.49, p=.052). Force production at moderate velocities did not separate disciplines, nor was it associated with performance. Variability in the shift of mechanical characteristics and inverse correlations between force augmentation at different velocities (rs=-0.74, p<.001) indicated countermovement effect depended on extension velocity. Skiers exhibited a smaller countermovement effect at low velocities (rrb=-0.68, p<.001), with the opposite observation for sprinters (rrb=0.43, p=.008). ‘Moderate’ velocities failed to differentiate groups. Better skiers produced greater force at low speeds with a smaller countermovement effect, which supports the existence of velocity-specific strength qualities. The ski-specific strength-endurance assessment yielded some discriminative results, but, due to interactions between the test settings and real athlete capacities, the principal value of this section was to direct future protocol design. This thesis generally supports the assertion that force output during skiing is partly limited by force production capacities. On snow, both high force-output capacity and effectiveness of application were associated with performance. Off snow, better-ranked athletes possessed the highest capacity for specific force-production capabilities. High-level skiers appear to display a dominance of force-production at low speeds and in isometric conditions compared to other sports.
... The sling exercise is an active neuromuscular control technique performed using a dangling rope and appropriate auxiliary devices. It reduces the pressure on the joints by pulling the weight, and simultaneously stimulates the muscles suppressed by pain to facilitate reactivation of the muscles [5]. While performing the sling exercise, the position of the suspension point can be changed for active involvement in the exercise, while minimizing the patient's pain. ...
... Therefore, exercising in an unstable environment is an effective method to increase the activation of the rectus femoris. These results are consistent with the findings of Andersen et al. [5], who reported that the activation of the rectus femoris increased during BSS in an unstable environment with a foam cushion, compared to BSS under a stable environment. In addition, this is also consistent with the result by Roelants et al. [6], who reported that activation of rectus femoris was significantly increased during the single-leg squat compared to the double-leg squat. ...
Article
Full-text available
Exercising in an unstable environment, such as with the use of a sling, improves neuromuscular adaptation by providing effective training stimuli. Moreover, whole body vibration has been used to restore the physical function of patients with nervous system and musculoskeletal disorders. However, there have been few studies on the most appropriate exercise method of combining unstable surface and WBV. The purpose of this study was to investigate the effect of a sling and sonic vibration stimulation on muscle activation while performing a Bulgarian split squat (BSS). Twenty male subjects (age 25.95 ± 2.42 years old, height: 172.59 ± 5.56 cm, weight: 77.74 ± 10.82 kg) participated in the study. The participants randomly performed five types of BS using a sling and sonic vibration (BSS–0 Hz, BSS–4 Hz, BSS–8 Hz, BSS–12 Hz, BSS–20 Hz, and BSS–30 Hz). Each condition was repeated five times. A 60-s break was given for each condition to minimize muscle fatigue. We measured the muscular activities in the gluteus medius, biceps femoris, rectus femoris, vastus medialis, and vastus lateralis. It was observed that muscle activation increased during exercise conditions that provided a sling and sonic vibration in all muscles. In particular, the highest activation appeared in the condition wherein a vibration of 30 Hz was provided. Our results show that the sling exercise combined with a sonic vibration of 30 Hz during the BSS has positive effects on lower limb muscle activity.
... The present findings suggested no differences in the level of muscle activation when performing a double-leg squat on a stable compared to an unstable surface. These results are in line with previous studies (Andersen et al., 2014;Anderson and Behm, 2005;McBride et al., 2006;Saeterbakken and Fimland, 2013;Wahl and Behm, 2008). Wahl and Behm (2008) reported no significant differences in the lower limb muscles activation when squatting on different unstable surfaces (ie, a BOSU, a Swiss ball, a wobble board etc.). ...
... Wahl and Behm (2008) reported no significant differences in the lower limb muscles activation when squatting on different unstable surfaces (ie, a BOSU, a Swiss ball, a wobble board etc.). Andersen et al. (2014) showed no differences in muscle activation during a double-leg squat on stable and unstable surfaces (cushion foam). On the other hand, Anderson and Behm (2005) found increased truck muscles activation (i.e. ...
Article
Full-text available
The aim of this study was to perform an electromyography comparison of three commonly used lower limb injury prevention exercises: a single-leg squat on a bench (SLSB), a double-leg squat (DLS) and a double-leg squat on a BOSU® balance trainer (DLSB). After determining the maximum isometric voluntary contraction of the hamstring and quadriceps, eight female athletes performed 3 repetitions of each exercise, while electromyography activity of the biceps femoris (BF), semitendinosus (ST), vastus lateralis (VL) and vastus medialis (VM) was monitored. Comparisons between exercises revealed higher activation in BF (descending phase: p = 0.016, d = 1.36; ascending phase: p = 0.046, d = 1.11), ST (descending phase: p = 0.04, d = 1.87; ascending phase: p = 0.04, d = 1.87), VL (ascending phase: p = 0.04, d = 1.17) and VM (descending phase: p = 0.05, d = 1.11; ascending phase: p = 0.021, d = 1.133) muscles for the SLSB compared to the DLSQ. Furthermore, higher muscular activation of the ST (ascending phase: p = 0.01, d = 1.51; descending phase: p = 0.09, d = 0.96) and VM (ascending phase: p = 0.065, d = 1.03; descending phase: p = 0.062, d = 1.05) during the SLSB with respect to the DLSB was observed. In conclusion, the SLSB elicits higher neuromuscular activation in both hamstring and quadriceps muscles compared to the other two analysed exercises. Additionally, the higher muscle activation of both medial muscles (ST and VM) during the SLSB suggests that single leg squatting exercises may enhance lower limb medial to lateral balance, and improve knee stability in the frontal plane.
... In its purest form, instability integrated via training unilaterally appears to increase activation of antagonist musculature (V. Andersen et al., 2014), which could be interesting for similarity during a skiing turn (Hintermeister et al., 1995). However, some investigations have reported reduced muscular activation of the agonist (i.e., increasing the relative contribution of the antagonist) (McBride, Cormie, & Deane, 2006), and almost all studies report impaired force production relative to the stable alternative (V. ...
... However, some investigations have reported reduced muscular activation of the agonist (i.e., increasing the relative contribution of the antagonist) (McBride, Cormie, & Deane, 2006), and almost all studies report impaired force production relative to the stable alternative (V. Andersen et al., 2014;Behm, Anderson, & Curnew, 2002;Drinkwater, Pritchett, & Behm, 2007;McBride et al., 2006). ...
Thesis
Full-text available
The literature characterizing force production during skiing, and the associated capacities of skiers, is complicated to synthesize due to aging results or relatively unspecific assessments. The overarching aim of this doctoral thesis was to clarify the importance of force output for skiing and of specific force-production capacities for different ski disciplines. The thesis comprised two themes: 1) characterizing the force output of skiers (N=15) on a giant-slalom course using kinematic and kinetic data from a global positioning system and boot-mounted force-platforms, respectively; and 2) measurement of dynamic and isometric force, the effect of countermovement on force production at different velocities, and specific strength-endurance across disciplines, and performance levels, in national skiers (N=31). The conclusions from Theme 1 were that radial force output applied to turn the skis was linked with performance (r=0.55– 0.72, p<.032) and depended on both total magnitude and the ability to apply the force effectively (β=0.64–1.00, p<.001). Higher total force was associated with a greater output of the outside limb and a smaller difference between the limbs (β=0.92–1.00 and -0.65– - 0.92, respectively, p<.001). For Theme 2, athletes from speed and technical disciplines displayed different dynamic and isometric force qualities, with the former showing superior dynamic force at low velocities (ω2=0.17, p<.001) and in isometric conditions (ω2=0.16–0.22, p<.003). Overall, performance was linked with a more force-dominant profile (ω2=0.34; r=0.60–0.67, p<.001) and increased rate of force development characteristics (r=-0.50– -0.82, p<.048). Robust associations existed between maximum isometric force and speed discipline performance (r=-0.88, p<.001), and a trend for higher values in better technical athletes (r=-0.49, p=.052). Force production at moderate velocities did not separate disciplines, nor was it associated with performance. Variability in the shift of mechanical characteristics and inverse correlations between force augmentation at different velocities (rs=-0.74, p<.001) indicated countermovement effect depended on extension velocity. Skiers exhibited a smaller countermovement effect at low velocities (rrb=-0.68, p<.001), with the opposite observation for sprinters (rrb=0.43, p=.008). ‘Moderate’ velocities failed to differentiate groups. Better skiers produced greater force at low speeds with a smaller countermovement effect, which supports velocity-specific strength qualities. The ski-specific strength-endurance assessment yielded some discriminative results, but, due to difficulties selecting and assessing the relevant capacities, the principal value of this section lies in direct future protocol design. This thesis generally supports the assertion that force-production capacities partly limit force output during skiing. On snow, both high force-output capacity and effectiveness of application were associated with performance. Off snow, better-ranked athletes possessed the highest capacity for specific force-production capabilities. High-level skiers appear to display a dominance of force production at low speeds and in isometric conditions compared to other sports, which should be considered in their testing and training.
... Neuromuscular differences have been reported between bilateral and unilateral movements (1,24). This is attributed to the greater stability requirements of the unilateral exercise and the neuromuscular control required for efficient performance (24). ...
... An advantage of unilateral exercises may be in the development of coordination and stabilizer musculature that may not be sufficiently stimulated in stable, bilateral movements (24). For example, decreasing the stability of an exercise can result in increased balance requirements, antagonist recruitment and cocontraction, and trunk/hip activation levels (1,5,30). In addition, unilateral exercises require a lower total external load that would be valuable in unloading anatomical structures such as the spine (17,27). ...
Article
Appleby, BB, Cormack, SJ, and Newton, RU. Specificity and transfer of lower-body strength: Influence of bilateral or unilateral lower-body resistance training. J Strength Cond Res 33(2): 318-326, 2019-To examine the development of lower-body strength using either bilateral or unilateral resistance training. Developmental rugby players (n = 33; mean training age = 5.4 ± 2.9 years; 1 repetition maximum [1RM] 90° squat = 178 ± 27 kg) completed an 18-week randomized controlled training design (bilateral group [BIL], n = 13; unilateral group [UNI], n = 10; comparison, n = 10). The 8-week training phase involved 2 lower-body, volume-load matched resistance sessions per week (6-8 sets × 4-8 reps at 45-88% 1RM), differing only in the prescription of a bilateral (back squat) or unilateral (step-up) resistance exercise. Maximum strength was assessed by a randomized order of 1RM back squat and step-up testing and analyzed for within- and between-group differences using effect sizes (ES ± 90% confidence limits [CL]). Both training groups showed practically important improvements in their trained exercise (ES ± 90% CL: BIL = 0.67 ± 0.48; UNI = 0.74 ± 0.38) with transfer to their nontrained resistance exercise (BIL step-up = 0.27 ± 0.39: UNI squat = 0.42 ± 0.39). The difference between groups in adaptation of squat strength was unclear (BIL ES = -0.34 ± 0.55), while the UNI group showed an advantage in step-up training (ES = 0.41 ± 0.36). The results demonstrate that practically important increases in lower-body strength can be achieved using bilateral or unilateral resistance training and development of that strength may be expressed in the movement not trained, supporting the transfer of strength training between exercises of similar joint movements and muscles. Coaches may choose to incorporate unilateral strength training where the prescription of bilateral training may be inhibited.
... Neuromuscular differences have been reported between bilateral and unilateral movements (1,24). This is attributed to the greater stability requirements of the unilateral exercise and the neuromuscular control required for efficient performance (24). ...
... An advantage of unilateral exercises may be in the development of coordination and stabilizer musculature that may not be sufficiently stimulated in stable, bilateral movements (24). For example, decreasing the stability of an exercise can result in increased balance requirements, antagonist recruitment and cocontraction, and trunk/hip activation levels (1,5,30). In addition, unilateral exercises require a lower total external load that would be valuable in unloading anatomical structures such as the spine (17,27). ...
Article
Appleby, BB, Cormack, SJ, and Newton, RU. Unilateral and bilateral lower-body resistance training does not transfer equally to sprint and change of direction performance. J Strength Cond Res XX(X): 000-000, 2018-Given maximal strength can be developed using bilateral or unilateral resistance training, the purpose of this study was to determine the magnitude of transfer of unilateral or bilateral resistance training to sprint and change of direction (COD) performance. Thirty-three trained participants (average training age = 5.4 ± 2.9 years and 1 repetition maximum [1RM] 90° squat = 177.6 ± 26.7 kg) completed either a bilateral group (BIL, n = 13), unilateral (UNI, n = 10), or comparison (COM, n = 10) 18-week randomized controlled training design. Training involved 2 lower-body, volume-load-matched resistance sessions per week (6-8 sets × 4-8 reps at 45-88% 1RM), differing only in the prescription of a bilateral (squat) or unilateral (step-up) resistance exercise. Strength was assessed through 1RM squat and step-up, in addition to 20-m sprint and a customized 50° COD test. The effect size statistic ± 90% confidence limit (ES ± CL) was calculated to examine the magnitude of difference within and between groups at each time point. BIL and UNI groups improved their trained and nontrained strength exercise with an unclear difference in adaptation of squat strength (ES = -0.34 + 0.55). Both groups improved 20-m sprint (ES: BIL = -0.38 ± 0.49 and UNI = -0.31 ± 0.31); however, the difference between the groups was unclear (ES = 0.07 ± 0.58). Although both groups had meaningful improvements in COD performance, bilateral resistance training had a greater transfer to COD performance than unilateral resistance training (between-groups ES = 0.59 ± 0.64). Both bilateral and unilateral training improved maximal lower-body strength and sprint acceleration. However, the BIL group demonstrated superior improvements in COD performance. This finding potentially highlights the importance of targeting the underlying physiological stimulus that drives adaptation and not exercise selection based on movement specificity of the target performance.
... The participants started with a standardized, progressive, specific warm-up protocol according to Saeterbakken and Fimland [20]. After a general warm-up on a treadmill or cycle, the protocol consisted of 15 repetitions at 30%, 10 repetitions at 50%, and 6 repetitions at 80% of the participants' self-reported 6-RM loads in squatting. ...
... Using a self-paced but controlled tempo, the participants lowered themselves to 80˚knee flexion (180˚fully extended knee) measured with a protractor (femur-fibula). When the participants had the correct knee angle, a horizontal elastic band was adjusted [20,21]. The participants had to touch the band (mid-thigh) in every repetition before starting the concentric phase. ...
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Although several studies have examined the effects of performing resistance training with different percentages of one-repetition maximum (1-RM), little is known of the neuromuscular effects and kinematics of lifting low to heavy loads with maximal movement velocity. The aim of this study is to compare muscle activation and kinematics in free-weight back squats with different loads. Thirteen resistance-training males (aged 24.2 ± 2.0 years, body mass 81.5 ± 9.1 kg, height 1.78 ± 0.06 m) with 6 ± 3 years of resistance-training experience conducted squats with 30%–100% of 1-RM. Barbell kinematics and electromyographic (EMG) activity of the vastus lateralis, vastus medialis, rectus femoris, semitendinosus, biceps femoris, and gluteus maximus were measured in the upward phase of each load. With increasing loads, the barbell velocity decreased, the upward phase duration increased, and the peak velocity occurred later. The muscle activation in all muscles increased with increasing loads but was not linear. In general, similar muscle activation in the prime movers was observed for loads between 40% and 60% of 1-RM and between 70% and 90% of 1-RM, with 100% of 1-RM being superior to the other loads when the loads were lifted at maximal intended velocity. However, the timing of maximal muscle activations was not affected by the different loadings for the quadriceps, but the timing was sequential and independent of loading (rectus femoris before vastus medial before vastus lateral). Maximal activation in the gluteus and semitendinosus increased with increasing loads. This means that for muscle activation, maximal lifting velocity may compensate for increased loads, which may allow resistance-trained athletes and individuals in rehabilitation to avoid heavy loads but still get the same muscle activation.
... The analysis of the exercises executed in instability has been carried out through muscular activation [26][27][28][29][30][31][32][33] and very few studies have looked at in-depth performance variables, such as power or speed [20,24,25,34]. It has been observed that performing exercises in unstable conditions meant a significant increase in the activation of the central musculature [35] and further improvements in activation comparing unstable push-ups with standard push-ups [36]. Furthermore, using suspended push-ups caused greater activation in the main motor musculature, such as the pectoralis major, the deltoid anterior, and the brachial triceps in comparison with traditional push-ups [31], and the stabilizing musculature [37]. ...
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(I) Training in unstable conditions, with different elements, platforms, or situations, has been used because there is a significant increase in muscle activation, balance, proprioception, and even sports performance. However, it is not known how the devices used are classified according to performance variables, nor the differences according to instability experience. (II) This study aims to analyze the differences in power and speed in push-ups with different situations of instability in trained and untrained male subjects. Power and speed in push-up exercises were analyzed in26 untrained and 25 trained participants in 6 different situations (one stable and five unstable)(1) stable (PS), (2) monopodal (PM), (3) rings (PR), (4) TRX®(PT), (5) hands-on Bosu®(PH) (6) feet on Bosu®(PF). The variables were analyzed using a linear position transducer. (III) The best data were evidenced with PS, followed by PR, PM, PT, PH and PF. The trained subjects obtained better results in all the conditions analyzed in mean and maximum power and speed values (p< 0.001). The decrease in these variables was significantly greater in the untrained subjects than in the trained subjects in the PR situation (8% and 18% respectively). In PF there were differences between groups(p< 0.001), reaching between 32–46% in all variables. The difference between the two groups was notable, varying between 12–58%. (IV) The results showed a negative and progressive influence of instability on power and speed in push-ups. This suggests that instability should be adapted to the subject’s experience and is not advisable in untrained subjects who wish to improve power.
... Research from Lockie et al. (2018) suggest that Bulgarian split squat is associated with sprinting due to the activation of the muscle groups and the hip hinge which is very similar to the movement when sprinting. Moreover, Andersen et al. (2014) suggests that Bulgarian split squat is an effective exercise which can be included in a training programme for football players not only for its strength and power benefits however, Bulgarian split squat as well as lunging exercises have been found to be very effective for improving aspects of football such as balance, flexibility as well as trunk stabilization (Lockie et al. 2014). ...
Article
Power it vital in football as it is utilized for the main movement patterns of the sport, which include sprinting and jumping, where these two happen very frequently and improvements in both can influence the overall performance. Therefore, this study is aimed to examine the influence of resistance training on power development in the lower extremity in relation to enhancing countermovement jump height as well as improving 10 and 20m sprint performance. Male youth elite football players (n=15, age =14.5±1.5, height =164±16.3, body mass =51±14.9) participated in this study over 8 weeks, attending 2 hourly sessions a week. Each session included a dynamic warm up, several resistance training exercises including, back squat, front squat, trap bar deadlift, behind neck push press, clean pull, jump squats, Nordics, lunges with dumbbells and Bulgarian split squat as well as stretches and conditioning work such as balance and trunk. Participants were tested through countermovement jump height for lateral and bi-lateral, as well as 10- and 20-meter sprint times prior, mid and after the training programme. There was a significant improvement in the countermovement jump height for both lateral and bi-lateral. Bi-lateral performance resulted in a significant improvement over the course of 8 weeks (CMJ - Pre. 24.5±3.99cm, Mid. 26.9±4.82cm, and Post. 28.4±4.56cm) (p = 0.05). There was also a significant improvement in the lateral for both left and right legged countermovement jump. ((Left) Pre = 15.64±2.62cm, mid = 16.9±2.24cm and post = 17.7±2.10cm (p = 0.025)) ((Right) Pre =14.5±2.82cm, mid =15.5±2.6cm and post =17±2.27cm (p =0.013)). However, there was no significant difference in both 10 and 20m sprints. (10m Pre =2.036±0.091s and post = 2.030667±0.098s (p = 0.620)) and 20m (pre =3.562±0.2s and post =3.5293±0.21s (p= 0.928)). Therefore, the conclusion for this study is that 8 weeks twice a week resistance training program has a significant improvement in jumping performance for both unilateral and bi-lateral however, not the sprinting performance including 10 and 20m.
... In support of training specificity, single leg exercises would seem appropriate given running and jumping are mostly unilateral performances. Conversely, bilateral exercises would seem to lack the sport-specific advantage of unilateral exercises whose less stable nature requires heightened neuromuscular coactivation and stabilization (1,6). However, the less stable nature of unilateral exercises limits the use of large external loads, which are vital in the development of maximal strength (6,26). ...
Article
Abstract Appleby, BB, Newton, RU, and Cormack, SJ. Kinetics and kinematics of the squat and step-up in well-trained rugby players. J Strength Cond Res XX(X): 000–000, 2018—The purpose of this study was to compare and contrast the kinetics and kinematics of squat and step-up performance in well-trained athletes. Triaxial ground reaction force (GRF) and 3D kinematic data were collected in 4 maximal effort repetitions each at 70, 80, and 90% of 1 repetition maximum (1RM) of squat and step-up. The difference in concentric phase kinetics and kinematics between the squat and step-up was compared using effect sizes (ES ± 90% confidence limits [CLs]) classified as: less than 0.2 as trivial; 0.2–0.6 as small; 0.6–1.2 as moderate; and 1.2–2.0 as large. Where the 90% CL crossed negative and positive 0.2 values, the effect was considered “unclear.n Ground reaction force was higher for the step-up than squat at all relative intensities per leg (peak GRF ES: 2.56 ± 0.19 to 2.70 ± 0.37; average GRF ES: 1.45 ± 0.27 to 1.48 ± 0.29). Per leg, the difference in concentric impulse favored the step-up compared with squat at 70% 1RM (ES = 0.71 ± 0.40) and 80% 1RM (ES = 0.30 ± 0.41) but was unclear at 90% 1RM (ES = −0.25 ± 0.47). The squat peak velocity was greater compared with step-up at all intensities (ES = −1.74 ± 0.48 to −1.33 ± 0.48). Despite a lower external load and a single base of support, per leg, the step-up produced comparable GRF because the squat suggesting overload provided by the step-up is sufficient for maximal strength development. Future research may investigate the efficacy of the step-up in a training intervention for the development of lower-body strength.
... The initial starting position ( Figure 2) consisted of advancing one leg while the back leg was placed on an elevated surface of 50 cm. The players then had to flex the forward knee while keeping the trunk straight [38]. ...
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This study aimed to study the coactivation patterns of the hamstring and quadriceps muscle groups during submaximal strength exercises commonly used in injury prevention in soccer without the use of maximum voluntary isometric contraction testing. This was used to compare: (i) the inter-limb differences in muscle activation; (ii) the intra-muscular group activation pattern and (iii) the activation pattern during different phases of the exercise. Muscle activation was recorded by surface electromyography in 19 elite, male, youth soccer players. Participants performed the following: Bulgarian squat, lunge and squat. Electrical activity was recorded for the rectus femoris, vastus medialis, vastus lateralis, biceps femoris and semitendinosus. No significant inter-limb differences were found (F1, 13 = 619; p = 0.82; η2 = 0.045). Significant differences were found in the muscle activation between individual muscles within the quadriceps and hamstrings muscle group for each of the exercises: Bulgarian squat (F1,18 = 331: p < 0.001; η2 = 0.80), lunge (F4,72 = 114.5; p < 0.001; η2 = 0.86) and squat (F1,16 = 247.31; p < 0.001; η2 = 0.93). Differences were found between the different phases of each of the exercises (F2,26 = 52.27; p = 0.02; η2 = 0.80). The existence of an activation pattern of each of the muscles in the three proposed exercises could be used for muscle assessment and as a tool for reconditioning post-injury.
... The lack of differences for the external oblique was in line with our previous study on the Russian swing [2] but not with previous strength exercise studies on the squat, row, and shoulder press [1,3,[16][17][18]. These studies examined more traditional exercises and generally showed that unilateral execution increased the trunk muscle activation on the contralateral side compared to bilateral execution. ...
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The aim of the study was to compare the one-armed vs. two-armed American kettlebell swing on trunk muscle activation. Fifteen resistance-trained men performed ten repetitions of both exercises using a 14-kg kettlebell. Surface EMG from the erector spinae, rectus abdominis and external oblique muscles were collected on both sides of the trunk. The erector spinae activation during the one-armed swing was 14–25% higher on the contralateral compared to the ipsilateral side in both exercises (Cohen’s d effect size [ES]=0.41–0.71, p ˂ 0.001–0.034). Further, the contralateral side was 14% more activated during the two-armed swing compared to the ipsilateral side during the one-armed swing (ES=0.43, p=0.009). For the rectus abdominis muscle, the two-armed swing induced higher activation of the rectus abdominis compared to the one-armed swing on both the contralateral (40%, ES=0.48, p=0.040) and ipsilateral side (59%, ES=0.83, p=0.002). There were no differences for the external oblique muscle (p=0.495–0.662). In conclusion, the trunk activation patterns of the two exercises were different, which could be explained by different biomechanics in the two exercises, and could thus have complimentary effects. We recommend that both unilateral and bilateral execution of the American kettlebell swing is included over time.
... Commonly used compound resisted hip extension exercises are the squat, deadlift, and hip thrust. Furthermore, to optimize the activation of specific muscles or for the purpose of variation in a periodized resistance training program, it is common to perform different variations of the same exercise (1)(2)(3). This can be done, for example, by moving the placement of the load horizontally (e.g., front squat vs back squat) relative to the axis of rotation (e.g., the hip joint). ...
Article
The aim of the study was to compare the muscle activation level of the gluteus maximus, biceps femoris and erector spinae in the hip thrust, barbell deadlift and hex bar deadlift; each of which are compound resisted hip-extension exercises. After two familiarization sessions, 13 resistance-trained men performed a 1-RM in all three exercises in one session, in randomized and counterbalanced order. The whole ascending movement (concentric phase), as well as its lower and upper part (whole movement divided in two), were analyzed. The hip thrust induced greater activation of the gluteus maximus compared to the hex bar deadlift in the whole (16%, p=0.025) and the upper part (26%, p=0.015) of the movement. For the whole movement, the biceps femoris was more activated during barbell deadlift compared to both the hex bar deadlift (28%, p<0.001) and hip thrust (20%, p=0.005). In the lower part of the movement, biceps femoris activation was respectively 48% and 26% higher for the barbell deadlift (p<0.001) and hex bar deadlift (p=0.049) compared to hip thrust. Biceps femoris activation in the upper part of the movement was 39% higher for the barbell deadlift compared to the hex bar deadlift (p=0.001) and 34% higher for the hip thrust compared to the hex bar deadlift (p=0.002). No differences were displayed for erector spinae activation (p=0.312-0.859). In conclusion, the barbell deadlift was clearly superior in activating the biceps femoris compared to the hex bar deadlift and hip thrust, whereas the hip thrust provided the highest gluteus maximus activation.
... Assim como todo agachamento, os principais músculos responsáveis pelo movimento são o quadríceps e glúteo máximo. Entretanto, em comparação ao agachamento, essa variação permite maior ativação de glúteo máximo (86) , glúteo médio (87) e isquiotibiais (87,88) . Porém, menor ativação do quadríceps (87) . ...
... Using a self-paced, but controlled tempo, the participants lowered themselves to 80° knee flexion (180° fully extended knee) measured with a protractor (femur -fibula). When the participant had the correct knee angle, a horizontal elastic band was adjusted (4,25). The participants had to touch the band (mid-thigh) in every repetition before starting the concentric phase. ...
Article
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The purpose of the study was to compare kinematic muscle activation when performing 6-RM squats using constant (free weights) or variable resistance (free weights + elastic bands). Twenty recreationally trained females were recruited with 4.6±2.1 years of resistance training experience and a relative strength (6-RM/body mass) of 1.1. After a familiarization session identifying the 6-RM loads, the participants performed 6-RM squats using constant and variable resistance in a randomized order. The total resistance in the variable resistance group was similar to the constant resistance in the pre-sticking region (98%), but greater in the sticking region (105%) and the post-sticking region (113%). In addition, the pre-sticking barbell velocity was 21.0% greater using variable than constant resistance, but 22.8% lower in the post-sticking region. No significant differences in muscle EMG activity, time occurrence and vertical displacement between the squat modalities were observed, except for higher barbell displacement post-sticking using variable resistance. It was concluded that, due to differences in total resistance in the different regions performing variable compared to constant resistance, greater barbell velocity was observed in the pre-sticking region and lower resistance was observed in the post-sticking region. However, the extra resistance in the sticking and post-sticking regions during the variable resistance modality did not cause increased muscle activity. When performing squats with heavy resistance, the authors recommend using variable resistance, but we suggest increasing the percentage resistance from the elastic bands or using chains.
... To facilitate the understanding of the neuromuscular demands imposed by multi-joint resistance training exercises many studies examine joint-level kinematics and kinetics (1,3,5,9,(13)(14)(15). The majority of these studies use an inverse dynamics approach to calculate the net internal joint moments (NJM), because NJM provide useful insights about the mechanical demands exhibited by particular muscle groups that act across the respective joint for which the NJM is calculated. ...
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Kipp, K, Kim, H, and Wolf, WI. Muscle forces during the squat, split squat, and step-up across a range of external loads in college-aged men. J Strength Cond Res XX(X): 000-000, 2020-Knowledge about the load-dependent demand placed on muscles during resistance training exercises is important for injury prevention and sports performance training programs. The purpose of this study was to investigate the effect of external load on lower extremity muscle forces during 3 common resistance training exercises. Nine healthy subjects performed 4 sets of the squat (SQ), split squat (SS), and step-up (SU) exercises each with 0, 25, 50, and 75% of body mass as additional load. Motion capture and force plate data were used to estimate individual muscle forces of 11 lower extremity muscles through static optimization. The results suggest load-dependent increases in muscle forces for the m. gluteus maximus, m. gluteus medius, vastus lateralis, m. vastus medius, m. vastus intermedius, m. semitendinosus, m. semimembranosus, m. biceps femoris long head, m. soleus, m. gastrocnemius lateralis, and m. gastrocnemius medialis during the execution of all 3 exercises. In addition, load-dependent increases in m. gluteus maximus, vastus lateralis, m. vastus medius, m. vastus intermedius, and m. biceps femoris long head forces were often more pronounced during the SS and SU than the SQ across the range of loads used in this study. These results suggest that the mechanical demands imposed by resistance training exercises scale with external load and that the extent of that scaling depends on the specific exercise.
... Another contributing factor for the improved cycling time trial performance in AUL group might be an enhanced body stabilization during force production. Existing literature suggests differences regarding neuromuscular activation between unilateral and bilateral resistance exercise, induced by increased stability requirements and neuromuscular control during unilateral exercise (7,25,47). Abt et al. (4) suggested that a strong and stable core musculature may promote torso stabilization within the saddle and maintenance of lower extremity alignment, which may contribute to efficient force generation in the pedal stroke, in particular during prolonged cycling. ...
Article
Ji, S, Donath, L, and Wahl, P. Effects of alternating unilateral vs. bilateral resistance training on sprint and endurance cycling performance in trained endurance athletes: A 3-armed, randomized, controlled, pilot trial. J Strength Cond Res XX(X): 000-000, 2021-Traditional preparatory resistance training for cyclists mainly relies on simultaneous bilateral movement patterns. This lack of movement specificity may impede transfer effects to specific aerobic and anaerobic requirements on the bike. Hence, this study investigated the effects of resistance training in alternating unilateral vs. simultaneous bilateral movement pattern on strength and anaerobic as well as aerobic cycling performance indices. Twenty-four trained triathletes and cyclists (age: 31.1 ± 8.1 years; V[Combining Dot Above]O2max: 57.6 ± 7.1 ml·min-1·kg-1) were randomly assigned to either an alternating unilateral (AUL), a simultaneous bilateral (BIL) training group or a control group (CON). Ten weeks of resistance training (4 × 4-10 repetition maximum) were completed by both training groups, although CON maintained their usual training regimen without resistance training. Maximal strength was tested during isometric leg extension, leg curl, and leg press in both unilateral and bilateral conditions. To compare the transfer effects of the training groups, determinants of cycling performance and time to exhaustion at 105% of the estimated anaerobic threshold were examined. Maximal leg strength notably increased in both training groups (BIL: ∼28%; AUL: ∼27%; p < 0.01) but not in CON (∼6%; p > 0.54). A significant improvement in cycling time trial performance was also observed in both training groups (AUL: 67%; BIL: 43%; p < 0.05) but not for CON (37%; p = 0.43). Bilateral group exhibited an improved cycling economy at submaximal intensities (∼8%; p < 0.05) but no changes occurred in AUL and CON (∼3%; p > 0.24). While sprint cycling performance decreased in CON (peak power: -6%; acceleration index: -15%; p < 0.05), improvement in favor of AUL was observed for acceleration abilities during maximal sprinting (20%; d = 0.5). Our pilot data underpin the importance of resistance training independent of its specific movement pattern both for improving the endurance cycling performance and maximal leg strength. Further research should corroborate our preliminary findings on whether sprint cycling benefits favorably from AUL resistance training.
... However, in the emergence of movement patterns, the central region has an important place in the emergence of every movement. In studies on squat movement, biceps femoris muscle is active at the level of 63-77%, while the external oblique muscles inside the core muscles become active at the level of 58-62% during squat movement (32). In another study, they stated that during the 6repetations back squat, the erector spine and external oblique muscles actively performed the movement during the squat movement (33). ...
... Although studies have shown the effectiveness of squatting exercises, there is a lack of evidence to demonstrate, comparatively, the effectiveness of different adaptations in the decrease of dynamic valgus. [28][29][30] . Thus, the objective of the study was to identify the efficacy of different adaptations of the squatting exercise in minimizing the immediate dynamic valgus by analyzing the projection angle in the frontal plane (PAPF) of the knee. ...
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Closed kinetic chain exercises have been employed in rehabilitation and muscle strengthening programs, such as squatting. During the movement of the squat dynamic valgus, a change that affects all kinematics of the lower limb, tends to become exacerbated, necessitating adaptations in order to minimize the biomechanical disorder. Although studies have shown the effectiveness of squatting exercises, there is a lack of evidence to demonstrate, comparatively, the effectiveness of different adaptations in the decrease of dynamic valgus. The objective of the study was to evaluate to identify the efficacy of different adaptations in squatting exercise in the reduction of dynamic valgus. Therefore, study volunteers (n = 30) performed three types of squats: free squatting, squatting with elastic band and squatting with verbal command. The dynamic valgus wasmeasured by the knee frontal plane projection angle during the squatting movements, through captured images and analyzed by the software Tracker and ImageJ. Despite more cases in women, in both sexes, free squatting presented greater cases of medicalization of the knee than in comparison to the other two adaptations. Although both squat adaptations presented positive results, only squatting with verbal command showed a significant reduction of the dynamic valgus pointing out that this is the best adaptation treated. Keywords: Genu Valgum. Exercise Therapy. Motor Activity. Resumo Exercícios de cadeia cinética fechada vêm sendo empregados em programas de reabilitação e fortalecimento muscular, como é o caso do agachamento. Durante o movimento de agachamento o valgo dinâmico, alteração que afeta toda cinemática do membro inferior, tende a se tornar exacerbado, sendo necessárias adaptações com o intuito de minimizar o distúrbio biomecânico. Embora estudos tenham mostrado a eficácia dos exercícios de agachamento, faltam evidências que demonstrem, comparativamente, a efetividade de diferentes adaptações na minimização do valgo dinâmico. O objetivo do estudo foi identificar a eficácia de diferentes adaptações na execução do exercício de agachamento na redução do valgo dinâmico. Para tanto, os voluntários do estudo (n=30) três tipos de agachamentos: agachamento livre, agachamento com banda elástica e agachamento com comando verbal. O valgo dinâmico foi mensurado mediante o ângulo de projeção no plano frontal do joelho durante os movimentos de agachamento, através de imagens capturadas e posteriormente analisadas pelos softwares Tracker e ImageJ. Apesar de mais casos em mulheres, em ambos os sexos, o agachamento livre apresentou maiores casos de medicalização do joelho do que nas outras duas adaptações. Embora ambas adaptações de agachamento apresentaram resultados positivos, apenas o agachamento com comando verbal apresentou redução significativa do valgo dinâmico, apontando ser esta a melhor adaptação tratada. Palavras-chaves: Geno Valgo. Terapia por Exercício. Atividade Motora.
... In addition, Flanagan and Salem (2008) found that as experienced lifters performed sets with 25-100% of their BS 3-RM, hip joint mechanics demonstrated a larger increase than knee joint mechanics. Although no previous studies compared RME between different resistance training exercises, some studies support the finding that increases in hip demands are more prominent during unilateral than bi-lateral exercises (Andersen et al., 2014;McCurdy et al., 2018;Schellenberg et al., 2015Schellenberg et al., , 2017. For example, McCurdy et al. (2010) found higher gluteus medius and hamstring EMG during a modified single leg squat than during a two-legged squat. ...
Article
The purpose of this study was to investigate the relative muscular effort (RME) of the hip and knee extensor and ankle plantarflexor muscle groups during the back squat (BS) and split squat (SS) exercises across four external load conditions. Motion capture and force plate data were collected as participants performed the BS and SS at 0%, 25%, 50%, and 75% of their body-mass. These data were used to calculate net joint moments (NJM) at the hip, knee, and ankle of the front leg during the SS and the matched leg during the BS. A musculoskeletal model, which accounted for force-length-velocity properties of 52 muscles, was used to estimate the maximal possible NJM (NJMmax) of the hip and knee extensor and ankle plantarflexor muscle groups. RME was calculated as the ratio between NJM and NJMmax, and compared across exercises and loads. The results indicated that while hip extensor RME increased across all loads, the increases in hip extensor RME were disproportionately greater during the SS at loads of 50% and 75%. Knee extensor RME increased linearly across loads and did not differ between exercises. These results provide coaches and athletes with detailed information about how to optimise resistance training specificity.
... In summary, almost all the studies found the major activity on the anterior thigh muscles, which are involved in the knee extension and are part of the quadriceps (vastus lateralis, vastus medialis, and rectus femoris), with the highest activation observed on the vastus lateralis. Only Andersen et al. (2014) and Gullet et al. (2009), reported higher activation levels on the hamstrings than on the quadriceps, in the front squat and high-bar squat, respectively. These uneven results may be due to the secondary function of the hamstrings as hip extensors (Netter, 1999). ...
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The squat is one of the most commonly used resistance exercises for performance and health due to its biomechanical and neuromuscular similarities to a wide range of athletic and everyday activities. There is a large number of squat variations (based on the descent depth, width of the stance, bar placement) with significant biomechanical and neuromuscular differences between them. The aim of this study was to systematically review the scientific literature to gather data on the muscular activation of the lower limb during different variants of the squat exercise. High-bar squat (full range of motion, to parallel and partial range of motion), low-bar squat, front squat, overhead squat and guided squat on Smith machine were included in the analysis. 30 articles met the inclusion criteria and were reviewed. Quality of the included studies was analysed with the PEDro scale. Main findings were that in the squat exercise activation of the knee-extensors is predominant. However, different activation patterns were observed with different distances between the feet, different depths, hips rotation or flexion, intensities. For instance, low-bar squat involves a greater hip hinge and thus, provokes major activation on the hip-extensors than other squat variations. It is worth highlighting that similar activation patterns were observed between the front squat and the high-bar squat. The variation with least activation was the guided squat. The evidence presented in this study may help the strength and conditioning professionals and practitioners with the exercise selection depending on the muscular targets and the individual characteristics of the athlete. Keywords: Electromyographic activity; Resistance exercise; Quadriceps; Gluteus; Hamstrings; Calves.
... kg) caused the higher activity of the vastus lateralis (Lawrence et al., 2018). However, since the relative loads used in the two exercises were identical, the load should not affect the outcome (Andersen et al., 2014;Saeterbakken and Fimland, 2013). Alternatively, since the exercises were performed unilaterally, a higher EMG amplitude of the vastus lateralis could have been produced to stabilize the knee joint while performing the leg press. ...
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Resistance-training exercises can be classified as either single-or multi-joint exercises and differences in surface electromyography (EMG) amplitude between the two training methods may identify which muscles can benefit from either training modality. This study aimed to compare the surface EMG amplitude of five hip-and knee extensors during one multi-joint (leg press) and two single joint exercises (knee extension and kickback). Fifteen resistance trained men completed one familiarization session to determine their unilateral six repetitions maximum (6RM) in the three exercises. During the following experimental session, EMG amplitudes of the vastus lateralis, vastus medialis, rectus femoris, gluteus maximus and biceps femoris of the left leg were measured while performing three repetitions on their respective 6RM loads. The multi-joint exercise leg press produced higher EMG amplitude of the vastus lateralis (ES = 0.92, p = 0.003) than the single-joint exercise knee extension, whereas the rectus femoris demonstrated higher EMG amplitude during the knee extension (ES = 0.93, p = 0.005). The biceps femoris EMG amplitude was higher during the single-joint exercise kickback compared to the leg press (ES = 2.27, p < 0.001), while no significant differences in gluteus maximus (ES = 0.08, p = 0.898) or vastus medialis (ES = 0.056, p = 0.025 were observed between exercises. The difference in EMG amplitude between single-and multi-joint exercises appears to vary depending on the specific exercises and the muscle groups tested. Leg press is a viable and time-efficient option for targeting several hip-and knee extensors during resistance training of the lower limbs, but the single-joint exercises may be preferable for targeting the rectus femoris and biceps femoris.
... While these exercises can improve physical fitness in recreationally trained individuals [3][4][5][6], the controversy still exists about their effectiveness for improvement of neuromuscular performance in athletes. Discrepancies can be mainly observed in acute and/or adaptive changes in muscle strength and power, as well as electromyographic (EMG) muscle activity in response to exercises performed under unstable conditions [7][8][9][10][11][12][13][14][15][16][17][18]. For instance, one of the former studies revealed that unstable surface training using inflatable balance discs attenuates an improvement in athlete's performance [19]. ...
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This study evaluates the effect of 8 weeks of the stable and unstable resistance training on muscle power. Thirty-three healthy men recreationally trained in resistance exercises, randomly assigned into two groups, performed resistance exercises either under stable or unstable conditions for 8 weeks (three sessions per week). Before and after 4 and 8 weeks of the training, they underwent squats and chest presses on either a stable surface or on a BOSU ball and a Swiss ball respectively with increasing weights up to at least 85% 1RM. Results showed significant improvements of mean power during chest presses on a Swiss ball at weights up to 60.7% 1RM after 4 and 8 weeks of the instability resistance training. Mean power increased significantly also during squats on a BOSU ball at weights up to 48.1% 1RM after 4 but not 8 weeks of instability resistance training. However, there were no significant changes in mean power during bench presses and squats on a stable support surface after the same training. These findings indicate that there is no cross effect of instability resistance training on power produced under stable conditions. This confirms and complies with the principle for specificity of training.
... It was already proved that power production in stable conditions is different from the power that is produced in unstable conditions [58]. Plus, training in unstable conditions result in a load decrement compared to training in stable conditions [59] and, for this reason, the back squat is a good exercise to apply the progressive overload principle to continually increase muscle size with resistance training [60]. Moreover, the back squat is an exercise that is performed in the sagittal plane while the act of skating is performed more on the frontal plane and there must be a specific strength program regarding the movement patterns that must be developed to notice any force-vector transference effect. ...
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Objectives The purposes of this review are: (i) to summarize the scientific literature regarding the anthropometric profile of artistic roller and figure skaters by skating discipline, skating level and gender; (ii) to summarize the scientific literature regarding the physical qualities of artistic roller and figure skaters by skating discipline, skating level and gender to provide relevant recommendations for both coaches and practitioners. News The analysis of the current literature demonstrates that elite skaters have high levels of aerobic power, agility, and strength compared to their non-elite counterparts. Moreover, elite skaters have significant asymmetries between limbs that might result in future injuries. Male skaters that participate in pairs disciplines have greater anthropometric measurements such as body mass, body height and arm span compared to those that participate in single disciplines. Freestyle skaters jump higher and have better levels of agility than synchronized skaters. Freestyle skaters and pairs skaters are amongst those who have better levels of flexibility. Prospects and projects This study is a narrative review which analyzed studies that investigated how body composition and physical qualities affect sports performance in artistic roller and figure skaters, based on their skating level and skating discipline. Conclusion This review can be a useful tool for coaches because it can help them to identify athletes with relevant morphological characteristics for any discipline of the artistic roller and figure skating. Furthermore, this review can help coaches build specific strength and conditioning programs for artistic skaters bearing in mind the athletes’ discipline and their level.
... The head extension will also increase the instability of the body. Although the unstable body state is more conducive to muscle exercise [33], it increases the risk of falling. Therefore, in squat training, an upward head gaze may not be a good choice for people with musculoskeletal diseases. ...
Running after childbirth, specifically how or when to return, is a hot topic in the field of physical therapy and on social media; however, there are significant gaps in the literature supporting when and how to safely initiate running postpartum. During pregnancy and following childbirth (both vaginal and cesarean), the body undergoes changes that may impact strength, neuromuscular control, endurance, and the ability to withstand the high-impact forces and repetitive nature of running. Many mothers experience new or worsened symptoms of musculoskeletal or pelvic floor dysfunction following pregnancy and childbirth and require physical therapy to normalize function. After most major injuries, it is common to participate in formalized rehabilitation; however, this is not the norm for athletes returning to running postchildbirth. Because of lack of evidence, many runners and clinicians struggle to develop appropriate rehabilitation progressions for return to running after childbirth. Pelvic and sports physical therapists must understand biomechanical features of running gait and safely progress strength, endurance, and neuromuscular control of the kinetic chain when guiding a runner back to running. This clinical commentary builds on existing guidelines, research, and expert opinion to propose a 4-phase rehabilitation framework to help runners initiate and progress running after childbirth. The result is an in-depth exercise prescription (intensity, frequency, type), examples of exercises (hip, abdominal, pelvic floor, and foot), running progression, and progression goals to prepare runners for symptom-free running after childbirth (see Video, Supplemental Digital Content 1, available at: http://links.lww.com/JWHPT/A58, where authors provide more insight on this return to running framework).
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Introduction and Aim: The results of the research show that the results of squat exercise affect the sprint performance and the results are different. For this reason, our aim in the study is to investigate the effect of Bulgarian split squat exercise, which is a squat type, on the sprint performance of 20 meters.Method: 10 sedanters who had a mean age of 20 ± 198 years, a mean height of 175,4 ± 5,35, a mean weight of 66,42 ± 7,68 and a BMI of 21,52 ± 1,37, from Manisa Celal Bayar University Faculty of Sports Sciences voluntarily participated in the study. Given the exercise protocol, participants were warmed up by low tempo jogging for 5 minutes. After the rests, participants participated in Bulgarian squat exercises in the form of 5-8 repetitions at 60-80 % of 1 RM. After each Bulgarian split squat, a 4-minute rest was given and then two 20-meter sprint tests were performed (STAE). After each sprint was given a 3-minute rest. The same group performed two 20-meter sprint tests 72 hours later without Bulgarian split squat exercise (STWE). The best score was taken from two sprint tests. The sprint performance after exercise was compared with the sprint performance without exercise. The data were analysed using the repeated measures method in the SPSS program.Findings and Conclusion: No significant difference was found (p>0.05) between the exercise types when the data obtained were compared. The reason for this is thought to be the fact that the subjects participating in the study were sedentary and in addition, the exercise caused fatigue on the subjects.
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The purpose of this study was to investigate the effect of different hip joint postures on electromyographic activity of selected lower limb muscles during squat's movement. Electromyographic activity of selected lower limb muscles of 15 healthy male students was recorded while performing a squat with neutral, 15°, 30°, 45° external and internal rotation of the hip. Friedman's nonparametric test was used to compare muscle activation at different angles of the hip rotation and the Wilcoxon test was used to determine within-group differences. The results of this study showed no significant difference in the activity of Vastus medialis (p = 0.052), Vastus lateralis (p = 0.102) and tensor fasciae lata (p = 0.193) in squat between different hip joint angles, but Significant differences were observed in gluteus medius muscle activation (p = 0.001) and biceps femoris (p = 0.015) in squat between different hip joint angles. Also, the results of this study showed that gluteus medius to tensor fascia lata activation ratio was significant in squat between different hip joint angles. squat with the external hip angles can be considered as an effective method to increase gluteus medius activation and gluteus medius to the tensor fasciae latae activation ratio. On the other hand, 45 ° external and 30 ° internal hip angles can be considered as an effective method to increase the biceps femoris activation.
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This study aimed to study the co-activation of hamstring-quadriceps muscles during submaximal strength exercises without the use of maximum voluntary isometric contraction testing and compare (i) the inter-limb differences in muscle activation, (ii) the intra-muscular group activation pattern, and (iii) the activation during different phases of the exercise. Muscle activation was recorded by surface electromyography of 19 elite male youth players. Participants performed five repetitions of the Bulgarian squat, lunge and the squat with an external load of 10 kg. Electrical activity was recorded for the rectus femoris, vastus medialis, vastus lateralis, biceps femoris and semitendinosus. No significant inter-limb differences were found (F1, 13=619; p=0.82; partial η2=0.045). Significant differences were found in the muscle activation between different muscles within the muscle group (quadriceps and hamstrings) for each of the exercises : Bulgarian squat (F1,18=331: p<0.001; partial η2=0.80), lunge (F4,72=114.5; p<0.001; partial η2=0.86) and squat (F1,16=247.31; p<0.001; partial η2=0.93).Differences were found between the concentric, isometric and eccentric phases of each of the exercises (F2, 26=52.27; p=0.02; partial η2=0.80). The existence of an activation pattern of each of the muscles in the three proposed exercises could be used for muscle assessment and as a tool for injury recovery.
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PURPOSE: The purpose of this study was to compare thigh muscle activities and muscle co-activation when performing squats, wall squats, and Spanish squats on stable and unstable ground.METHODS: Twenty-two healthy male subjects (age: 22.50±2.70 years, height: 178.72±6.04 cm, mass: 76.50±6.80 kg, body mass index: 24.00±2.10 kg/m2, and Godin activity questionnaire: 56.30±24.10) voluntarily participated in the study. All of the participants performed three different squat exercises on the floor and the BOSU ball with an electromyograph attached to each participant’s quadriceps (rectus femoris, RF; vastus lateralis, VL; and vastus medialis, VM) and hamstrings (biceps femoris, BF; semitendinosus, ST; and semimembranosus, SM). Repeated measures of analysis of variance were utilized to compare muscle activity during the three squats exercises by floor type.RESULTS: RF (p<.001, η2=.689), VL (p<.001, η2=.622), and VM (p=.002, η2=.375) showed significant differences between exercises. Spanish squats yielded greater BF activity than did wall squats (p=.018, η2=.269). ST yielded greater muscle activity with the BOSU ball than on the floor (p=.018, η2=.269). Finally, there was a significant ground exercise interaction effect on the co-activation, showing greater muscle co-activation with Spanish squats on the BOSU ball compared to squats, squats on the BOSU ball, and wall squat on the BOSU ball.CONCLUSIONS: The findings of this study indicate that Spanish squats could be an effective exercise option for the facilitation of RF, VL, VM, and BF muscle activation. In particular, performing Spanish squats on an unstable surface could be useful for patients who need to improve their quadriceps muscle activation.
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Exercises can be categorized into either unilateral or bilateral movements. Despite the topic popularity, the answer to the question as to which (unilateral or bilateral) is superior for a certain athletic performance enhancement remains unclear. To compare the effect of unilateral and bilateral resistance training interventions on measures of athletic performance. Keywords related with unilateral, bilateral and performance were used to search in the Web of Science, PubMed databases, and Google Scholar and ResearchGate™ websites. 6365 articles were initially identified, 14 met the inclusion criteria and were included in the final analysis, with overall article quality being deemed moderate. The quantitative analysis comprised 392 subjects (aged: 16 to 26 years). Sub-group analysis showed that unilateral exercise resistance training resulted in a large effect in improving unilateral jump performance compared to bilateral training (ES = 0.89 [0.52, 1.26]). In contrast, bilateral exercise resistance training showed a small effect in improving bilateral strength compared to unilateral (ES = -0.43 [-0.71, -0.14]). Non-significant differences were found in improving unilateral strength (ES = 0.26 [-0.03, 0.55]), bilateral jump performance (ES = -0.04 [-0.31, 0.23]), change of direction (COD) (ES = 0.31 [-0.01, 0.63]) and speed (ES = -0.12 [-0.46, 0.21]) performance. Unilateral resistance training exercises should be chosen for improving unilateral jumping performance, and bilateral resistance training exercises should be chosen for improving bilateral strength performance.
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BACKGROUND: Compensating unstable situations is an important functional capability to maintain joint stability, to compensate perturbations and to prevent (re-)injury. Therefore, reduced maximum strength and altered neuromuscular activity are expected by inducing instability to load test situations. Possible effects are not clear for induced instability during maximum legpress tests in healthy individuals. OBJECTIVE: To compare isokinetic legpress (LP) strength and lower-leg muscle activity using stable (S) and unstable (UN) footplates. METHODS: 16 males (28 ± 4 yrs, 179 ± 7 cm, 75 ± 8 kg) performed five maximum LP in concentric (CON) and eccentric (ECC) mode. The maximum force (Fmax) and muscle activity were measured under conditions of S and UN footplates. The tested muscles comprised of the tibialis anterior (TA), peroneus longus (PL) and soleus (SOL) and their activity were quantified against the MVIC of each muscle respectively. RESULTS: The main finding revealed a significant reduction in Fmax under UN condition: 11.9 ± 11.3% in CON and 23.5 ± 47.8% in ECC (P< 0.05). Significant findings were also noted regarding the RMS derived values of the EMG of PL and TA. CONCLUSION: Unstable LP reduced force generation and increased the activity of PL and TA muscles which confirmed greater neuromuscular effort to compensate instability. This may have some implications for resistance testing and training coupled with an unstable base in the prevention and rehabilitation of injury to the neuromusculoskeletal system.
Article
Squats are considered a useful basic exercise for trunk muscle activation. To gain knowledge about trunk muscle activity patterns depending on the barbell position in beginners, we examined squats with low weights in the back, front, and overhead position. Methods: Twelve healthy adults (6 women/6 men, age: 29.1 (SD 8.0) y, height: 173.4 (6.9) cm, body mass: 70.1 (9.1) kg) randomly performed the three barbell squats in normal and in forefoot standing. Surface electromyography from external (EO) and internal oblique, rectus abdominis, and erector spinae (ES) was recorded. The centre of pressure path length (CoP) and the motion of the lumbar spine were captured. Results: The overhead squat revealed the highest percent muscle activity, where EO (p = 0.009) and ES (p = 0.03) showed the greatest activity. Forefoot standing did not change overall trunk muscle activities (.05< Hedges' g <.29, 0.17 < p < 0.95) although longer CoP path length (.45 < g < 1.3, p < 0.05) was measured. Conclusions: Squat exercises with low weight are useful to activate trunk muscles. Activity increases with the difficulty of the squat by frontal or overhead loading, but not by standing on the forefoot. The low weighted squat can target well core muscle activity in training with beginners or in rehabilitation.
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Nowadays alternative strength training methods and alternative sport equipment are widely spread in recreation and elite sport. We can see BOSU, Dynair, TRX etc. exercises both in the gym and in the training of elite athletes. Training with these accessories is called functional training. Our aim is to show the effect of unstable load exercise for the skeletal muscles, which has not yet been broadly examined through scientific means. Exercise with chains as unstable load caused significant changes in the observed muscle activity compared to the classic barbell. In case of unstable loads we measured significantly higher activity in the skeletal muscles. These significant changes were detected in the deltoid muscles, pectoral muscles, abdominal muscles and spinal erectors. Coaches and trainers can adapt these results into the training of elite and recreation athletes. Manapság a szabadidősport és az élsport világában is széles körben elterjedtek a különböző alternatív erőfejlesztő eljárások, sporteszközök. Bosu labdával, Dynair párnával, TRX felfüggesztéses eszközzel stb. kondicionáló termekbe vagy sportági edzésekre látogatva gyakorta találkozunk. Ezen eszközökkel történő edzéseket leggyakrabban a ”funkcionális edzés” kategóriájába sorolják. A funkcionális edzés kifejezés pontos fogalmi meghatározása mellett, bemutatunk egy eddig tudományosan nemzetközileg is kevésbé vizsgált, a mozgatórendszer számára instabil terhelést jelentő sporteszközt. A teherláncokkal történő erőfejlesztő gyakorlatok vizsgálata során jelentős különbségeket mértünk a hagyományos erősítő gyakorlatokhoz képest. Az instabil súllyal történő lökés gyakorlat esetében szignifikánsan magasabb izomaktivitást regisztráltunk, mint az ugyanakkora tömegű, de klasszikus súllyal történő végrehajtás esetében. A mért különbségek a mozgást létrehozó izmokon kívül (m. deltoideus, m. pectoralis major), a stabil egyensúlyi helyzet megtartásáért felelős törzs izmok (m. rectus abdominis, m. erector spinae) esetében is jelentősek voltak. Az eredményeket a gyakorló edzők mellett, az elméleti szakemberek is sikerrel adaptálhatják a sportolók, élsportolók felkészítési folyamatában, de akár a szabadidősport világában is.
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Background and purpose: WHILE THE POPULARITY OF INSTABILITY RESISTANCE TRAINING (RESISTANCE TRAINING THAT INVOLVES THE USE OF UNSTABLE SURFACES AND DEVICES: IRT) is evident in fitness training facilities, its effectiveness for optimal sport performance training has been questioned. The purpose of this clinical commentary is to explore the resistance training literature, which implements the use of unstable surfaces and devices to determine the suitability of IRT for rehabilitation. Description of topic and related evidence: The criticism of IRT for athletic conditioning is based on the findings of impaired kinetic measures such as force, power and movement velocity during a bout of IRT compared to traditional resistance training with more stable surfaces or devices. However, these deficits occur concurrently with minimal changes or in some cases increases in trunk and limb muscle activation. Compared to the kinetic deficits that are reported during unstable resistance exercises, the relatively greater trunk muscle activation indicates a greater stabilizing function for the muscles. IRT exercises can also provide training adaptations for coordination and other motor control issues, which may be more important for low back pain rehabilitation than strength or power enhancements. Relation to clinical practice: Improvements in postural stability from balance training without resistance can improve force output which can then lead to a training progression involving an amalgamation of balance and IRT leading to higher load traditional resistance training.
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In this study we investigated if the occurrence of the sticking region was a result of diminishing potentiation (coinciding delayed muscle activation) or the result of a mechanically poor region in which the muscles can produce less force. A regular one-repetition maximum (1RM) free-weight bench press was compared with isometric bench presses performed at 12 different positions. A lower force at the sticking region compared to the other regions in the isometric bench presses would confirm the mechanically-poor-position hypothesis. Twelve resistance-trained males (age 21.7 ± 1.3 years, mass 78 ± 5.8 kg, height 1.81 ± 0.05 m) were tested in 1RM and in isometric contractions in bench press in 12 different positions, indicated by the vertical distance between barbell and sternum, covering the whole range of motion during the concentric phase. Barbell kinematics and muscle activity were registered. In both types of executions a region of lower force output was observed, which supports the mechanically-poor-position hypothesis. Electromyographic activity of four muscles showed the same pattern in the isometric and 1RM attempts. It was concluded that diminishing effect potentiation could not explain the existence of the sticking region.
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Little is known about the effect of performing common resistance exercises standing compared to seated and unilaterally compared to bilaterally on muscle activation of the core. Thus, the purpose of this study was to compare the electromyographic activity (EMG) of the superficial core muscles (i.e. rectus abdominis, external oblique and erector spinae) between seated, standing, bilateral and unilateral dumbbell shoulder presses. 15 healthy males performed five repetitions at 80% of one-repetition maximum of the exercises in randomized order. Results were analyzed with a two-way analysis of variance and a Bonferroni post hoc test. The position × exercise interaction was significantly different for rectus abdominis (P = 0.016), but not for external oblique (P = 0.100) and erector spinae (P = 0.151). The following EMG results were observed: For rectus abdominis: ~49% lower in seated bilateral versus unilateral (P < 0.001), similar in standing bilateral versus unilateral (P = 0.408), ~81% lower in bilateral seated versus standing (P < 0.001), ~59% lower in unilateral seated versus standing (P < 0.001); For external oblique: ~81% lower in seated bilateral versus unilateral (P < 0.001), ~68% lower in standing bilateral than unilateral (P < 0.001), ~58% lower in bilateral seated versus standing (P < 0.001), ~28% lower in unilateral seated versus standing (P = 0.002); For erector spinae: similar in seated bilateral versus unilateral (P = 0.737), ~18% lower in standing bilateral versus unilateral (P = 0.001), similar in seated versus standing bilateral (P = 0.480) and unilateral (P = 0.690). In conclusion, to enhance neuromuscular activation of the superficial core muscles, standing exercises should be used instead of seated exercises, and unilateral exercises should be used instead of bilateral exercises.
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The aim of this study was to examine the effects of a stable surface (bench) vs. an unstable surface (Swiss ball) on muscle activation when performing the dumbbell chest press and shoulder press. Sixteen healthy men (24.19 +/- 2.17 years) performed 1 repetition maximum (1RM) tests for the chest press and shoulder press on a stable surface. A minimum of 48 hours post 1RM, subjects returned to perform 3 consecutive repetitions each of the chest press and shoulder press at 80% 1RM under 4 different randomized conditions (chest press on bench, chest press on Swiss ball, shoulder press on bench, shoulder press on Swiss ball). Electromyography was used to assess muscle activation of the anterior deltoid, pectoralis major, and rectus abdominus. The results revealed no significant difference in muscle activation between surface types for either exercise. This suggests that using an unstable surface neither improves nor impairs muscle activation under the current conditions. Coaches and other practitioners can expect similar muscle activation when using a Swiss ball vs. a bench.
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To compare EMG activity of selected hip and knee muscle groups in female athletes performing a modified single-leg squat and the 2-leg squat using the same relative intensity. Eleven Division I female athletes from a variety of sports (soccer, softball, and track) completed the study. EMG measurements were taken as the subjects completed 3 parallel repetitions at 85% of their 3-repetition maximum on each exercise. Mean and mean peak EMG data from the gluteus medius, hamstrings, and quadriceps and the quadriceps:hamstrings EMG ratio were compared between the 2 exercises. Statistically higher mean (P < .01) and mean peak (P < .05) gluteus medius and mean and mean peak (P < .01) hamstring EMG activity occurred during the modified single-leg squat. The 2-leg squat produced higher mean and mean peak (P < .05) quadriceps activity and a higher quadriceps:hamstrings EMG ratio (P < .01). Muscle-recruitment patterns appear to differ between the 2 types of squat exercises when performed at the same relative intensity by female athletes.
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Previously we have conducted a randomised controlled trial (RCT) to evaluate the effect of a brief cognitive behavioural program with a vocational approach aiming to return disability pensioners with back pain to work, as compared to no intervention. One year after the intervention, 10 participants (22%) who received the program and 5 (11%) in the control group reported to have entered a return to work process. The aims of this study were to evaluate long-term effects of the intervention, and compare this effect to 2 reference populations not participating in the original trial. Three groups of disability pensioners were investigated: 1) Disability pensioners having back pain (n = 89) previously participating in the RCT (randomized to either a brief cognitive behavioural intervention or to a control group), 2) 342 disability pensioners having back pain, but refusing to participate in the study and 3) 449 disability pensioners having other musculoskeletal disorders than back pain. Primary outcome was return to work, defined as a reduction in payment of disability pension. Only 2 of 89 (2.3%) participants from the RCT had reduced disability pension at 3-years follow-up, both from the control group. None of the participants that had been in a process of returning to work after 1 year had actually gained employment at 3-years follow-up. In the 2 groups not participating in the previous RCT, only 4 (1.2%) and 8 (1.6%) had returned to work after 3 years respectively. The number of pensioners who returned to work was negligible in all groups regardless of having participated in a cognitive behavioural intervention or not.
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To compare core muscle activity during resistance exercises performed on stable ground vs. the BOSU Balance Trainer. Twelve trained men performed the back squat, dead lift, overhead press, and curl lifts. The activity of the rectus abdominis, external oblique abdominis, transversus abdominis/internal oblique abdominis, and erector spinae muscles was assessed. Subjects performed each lift under three separate conditions including standing on stable ground with 50% of a 1-RM, standing on a BOSU Balance Trainer with 50% of a 1-RM, and standing on stable ground with 75% of a 1-RM. Significant differences were noted between the stable 75% of 1-RM and BOSU 50% of 1-RM conditions for the rectus abdominis during the overhead press and transversus abdominis/internal oblique abdominis during the overhead press and curl (P < .05). Conversely, there were no significant differences between the stable 75% of 1-RM and BOSU 50% of 1-RM conditions for the external obliques and erector spinae across all lifts examined. Furthermore, there were no significant differences between the BOSU 50% of 1-RM and stable 50% of 1-RM conditions across all muscles and lifts examined. The current study did not demonstrate any advantage in utilizing the BOSU Balance Trainer. Therefore, fitness trainers should be advised that each of the aforementioned lifts can be performed while standing on stable ground without losing the potential core muscle training benefits.
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The objective of this study was to determine differences in isometric force output, muscle activation (interpolated twitch technique), and electromyographic activity of the quadriceps, plantar flexors (PF), and their antagonists under stable and unstable conditions. Instability in subjects was introduced by making them perform contractions while seated on a "Swiss ball." Eight male subjects performed unilateral leg extensor (LE) and PF contractions while seated on a bench (LE), chair (PF), or a ball. Unstable LE and PF forces were 70.5 and 20.2% less than their stable counterparts, respectively. Unstable quadriceps and PF activation averaged 44.3 and 2.9% less than activation under stable conditions. Unstable antagonist/agonist ratios were 40.2 and 30.7% greater than stable ratios in the LE and PF protocols, respectively. The greater decrements with LE can be attributed to the instability of only 2 points of floor contact, rather than 3 points of floor contact as with the PF. Swiss balls may permit a strength training adaptation of the limbs, if instability is moderate, allowing the production of overload forces.
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The most predominant literature regarding balance has emphasised the physiological mechanisms controlling stability. Topics range from extrinsic factors (environment) to intrinsic factors (i.e. muscle coordination, vestibular response). Balance is achieved through an interaction of central anticipatory and reflexive actions as well as the active and passive restraints imposed by the muscular system. However, less research has attempted to document the effects of balance on performance measures (i.e. force, power). Furthermore, short- and long-term adaptations to unstable environments need more substantial research. While force and other performance measures can be adversely affected by a lack of balance, the transferability of instability training to activities of daily living and sport is not precisely known. The applicability of instability and resistance training using unstable platforms or implements may have strong relevance in a rehabilitative or athletic setting. Therefore, a comprehensive review of the literature in this area may possibly be of benefit to practitioners who deal with the general population, athletes or persons debilitated by balance and/or stability disabilities.
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The objective of this study was to determine differences in electromyographic (EMG) activity of the soleus (SOL), vastus lateralis (VL), biceps femoris (BF), abdominal stabilizers (AS), upper lumbar erector spinae (ULES), and lumbo-sacral erector spinae (LSES) muscles while performing squats of varied stability and resistance. Stability was altered by doing the squat movement on a Smith machine, a free squat, and while standing on two balance discs. Fourteen male subjects performed the movements. Activities of the SOL, AS, ULES, and LSES were highest during the unstable squat and lowest with the Smith machine protocol (p < 0.05). Increased EMG activity of these muscles may be attributed to their postural and stabilization role. Furthermore, EMG activity was higher during concentric contractions compared to eccentric contractions. Performing squats on unstable surfaces may permit a training adaptation of the trunk muscles responsible for supporting the spinal column (i.e., erector spinae) as well as the muscles most responsible for maintaining posture (i.e., SOL).
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It has been shown in classical strength training studies using high loads that improvements in rate of force development are mainly due to adaptations in the intramuscular coordination. Adaptations following sensorimotor training were also characterized by improvements in the rate of force development during maximum voluntary isometric contraction. The purpose of the present study was to investigate neuromuscular adaptations of combined sensorimotor and classical strength training. Eighteen subjects were randomly assigned to two groups. Group 1 (SMT-HST) had to perform a period of sensorimotor training at first and a high-intensity strength training afterwards. Group 2 (HST-SMT) performed the high intensity strength training at first and the sensorimotor training after. Maximum voluntary isometric contraction and neuromuscular activation were measured at three occasions: Before training, after the first, and after the second period. The results after the first period confirmed the positive effects of both training regimen on rate of force development (13 % [SMT-HST] and 27 % [HST-SMT], p < 0.05) and on maximum strength (9 % [HST-SMT] and 12 % [SMT-HST], p < 0.05) during maximum voluntary contraction. Improvements caused by sensorimotor training could only be achieved, when it was performed at first. It is supposed that classical strength training with high loads basically improves the mechanical efficiency of the effectors, whereas sensorimotor training alters the afferent input on the central nervous system. In combination, the sensorimotor training can have preconditioning effects on the strength training. A combination of both training methods can thus be recommended, if the sensorimotor training is performed at first.
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There are many instances in daily life and sport in which force must be exerted when an individual performing the task is in an unstable condition. Instability can decrease the externally-measured force output of a muscle while maintaining high muscle activation. The high muscle activation of limbs and trunk when unstable can be attributed to the increased stabilization functions. The increased stress associated with instability has been postulated to promote greater neuromuscular adaptations, such as decreased co-contractions, improved coordination, and confidence in performing a skill. In addition, high muscle activation with less stress on joints and muscles could also be beneficial for general musculoskeletal health and rehabilitation. However, the lower force output may be detrimental to absolute strength gains when resistance training. Furthermore, other studies have reported increased co-contractions with unstable training. The positive effects of instability resistance training on sports performance have yet to be quantified. The examination of the literature suggests that when implementing a resistance training program for musculoskeletal health or rehabilitation, both stable and unstable exercises should be included to ensure an emphasis on both higher force (stable) and balance (unstable) stressors to the neuromuscular system.
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High-resistance strength training (HRST) is one of the most widely practiced forms of physical activity, which is used to enhance athletic performance, augment musculo-skeletal health and alter body aesthetics. Chronic exposure to this type of activity produces marked increases in muscular strength, which are attributed to a range of neurological and morphological adaptations. This review assesses the evidence for these adaptations, their interplay and contribution to enhanced strength and the methodologies employed. The primary morphological adaptations involve an increase in the cross-sectional area of the whole muscle and individual muscle fibres, which is due to an increase in myofibrillar size and number. Satellite cells are activated in the very early stages of training; their proliferation and later fusion with existing fibres appears to be intimately involved in the hypertrophy response. Other possible morphological adaptations include hyperplasia, changes in fibre type, muscle architecture, myofilament density and the structure of connective tissue and tendons. Indirect evidence for neurological adaptations, which encompasses learning and coordination, comes from the specificity of the training adaptation, transfer of unilateral training to the contralateral limb and imagined contractions. The apparent rise in whole-muscle specific tension has been primarily used as evidence for neurological adaptations; however, morphological factors (e.g. preferential hypertrophy of type 2 fibres, increased angle of fibre pennation, increase in radiological density) are also likely to contribute to this phenomenon. Changes in inter-muscular coordination appear critical. Adaptations in agonist muscle activation, as assessed by electromyography, tetanic stimulation and the twitch interpolation technique, suggest small, but significant increases. Enhanced firing frequency and spinal reflexes most likely explain this improvement, although there is contrary evidence suggesting no change in cortical or corticospinal excitability. The gains in strength with HRST are undoubtedly due to a wide combination of neurological and morphological factors. Whilst the neurological factors may make their greatest contribution during the early stages of a training programme, hypertrophic processes also commence at the onset of training.
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Strength training is an important component in sports training and rehabilitation. Quantification of the dose-response relationships between training variables and the outcome is fundamental for the proper prescription of resistance training. The purpose of this comprehensive review was to identify dose-response relationships for the development of muscle hypertrophy by calculating the magnitudes and rates of increases in muscle cross-sectional area induced by varying levels of frequency, intensity and volume, as well as by different modes of strength training. Computer searches in the databases MEDLINE, SportDiscus® and CJNAHL® were performed as well as hand searches of relevant journals, books and reference lists. The analysis was limited to the quadriceps femoris and the elbow flexors, since these were the only muscle groups that allowed for evaluations of dose-response trends. The modes of strength training were classified as dynamic external resistance (including free weights and weight machines), accommodating resistance (e.g. isokinetic and semi-isokinetic devices) and isometric resistance. The subcategories related to the types of muscle actions used. The results demonstrate that given sufficient frequency, intensity and volume of work, all three types of muscle actions can induce significant hypertrophy at an impressive rate and that, at present, there is insufficient evidence for the superiority of any mode and/or type of muscle action over other modes and types of training. Tentative dose-response relationships for each variable are outlined, based on the available evidence, and interactions between variables are discussed. In addition, recommendations for training and suggestions for further research are given.
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The purpose of this study was to investigate the effectiveness of instability training in the recruitment of core stabilizing muscles during dynamic multijoint movement. Surface electromyography (EMG) was measured from 6 muscles (latissimus dorsi, rectus abdominus, internal obliques, erector spinae, and soleus) while subjects performed a 9.1-kg bench press on stable and unstable surfaces. There were 4 exercises in total: (a) stable surfaces for shoulders and feet, (b) upper-body instability, (c) lower-body instability, and (d) dual instability. Five seconds of EMG were recorded during each bench press and were subsequently smoothed with root mean squares calculated for the entire time-series. A repeated-measures analysis of variance (ANOVA) was used to test overall differences between exercise conditions for each muscle. Paired equal variance t-tests with a stepwise Bonferroni correction for multiple contrasts (alpha = 0.05/total number of contrasts) were performed for muscles with significant repeated-measures ANOVA results. The results show significant increases in EMG with increasing instability. Specifically, the dual instability bench press resulted in the greatest mean muscle activation of the 3 stability conditions, with single instability conditions being significantly greater than the stable condition. This pattern of results is consistent with the position that performing the bench press in a progressively unstable environment may be an effective method to increase activation of the core stabilizing musculature, while the upper- and lower-body stabilizers can be activated differentially depending on the mode of instability.
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This brief review examines some of the methods used to infer central control strategies from surface electromyogram (EMG) recordings. Among the many uses of the surface EMG in studying the neural control of movement, the review critically evaluates only some of the applications. The focus is on the relations between global features of the surface EMG and the underlying physiological processes. Because direct measurements of motor unit activation are not available and many factors can influence the signal, these relations are frequently misinterpreted. These errors are compounded by the counterintuitive effects that some system parameters can have on the EMG signal. The phenomenon of crosstalk is used as an example of these problems. The review describes the limitations of techniques used to infer the level of muscle activation, the type of motor unit recruited, the upper limit of motor unit recruitment, the average discharge rate, and the degree of synchronization between motor units. Although the global surface EMG is a useful measure of muscle activation and assessment, there are limits to the information that can be extracted from this signal.
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The objective of this study was to measure the electromyographic (EMG) activity of the soleus, bicep femoris, rectus femoris, lower abdominal, and lumbosacral erector spinae (LSES) muscles with a variety of (a) instability devices, (b) stable and unstable (Dyna Disc) exercises, and (c) a fatiguing exercise in 16 highly conditioned individuals. The device protocol had participants assume standing and squatting postures while balancing on a variety of unstable platforms (Dyna Disc, BOSU ball, wobble board, and a Swiss ball) and a stable floor. The exercise protocol had subjects performing, static front lunges, static side lunges, 1-leg hip extensions, 1-leg reaches, and calf raises on a floor or an unstable Dyna Disc. For the fatigue experiment, a wall sit position was undertaken under stable and unstable (BOSU ball) conditions. Results for the device experiment demonstrated increased activity for all muscles when standing on a Swiss ball and all muscles other than the rectus femoris when standing on a wobble board. Only lower abdominals and soleus EMG activity increased while squatting on a Swiss ball and wobble board. Devices such as the Dyna Disc and BOSU ball did not exhibit significant differences in muscle activation under any conditions, except the LSES in the standing Dyna Disc conditions. During the exercise protocol, there were no significant changes in muscle activity between stable and unstable (Dyna Disc) conditions. With the fatigue protocol, soleus EMG activity was 51% greater with a stable base. These results indicate that the use of moderately unstable training devices (i.e., Dyna Disc, BOSU ball) did not provide sufficient challenges to the neuromuscular system in highly resistance-trained individuals. Since highly trained individuals may already possess enhanced stability from the use of dynamic free weights, a greater degree of instability may be necessary.
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High-resistance strength training (HRST) is one of the most widely practiced forms of physical activity, which is used to enhance athletic performance, augment musculo-skeletal health and alter body aesthetics. Chronic exposure to this type of activity produces marked increases in muscular strength, which are attributed to a range of neurological and morphological adaptations. This review assesses the evidence for these adaptations, their interplay and contribution to enhanced strength and the methodologies employed. The primary morphological adaptations involve an increase in the cross-sectional area of the whole muscle and individual muscle fibres, which is due to an increase in myofibrillar size and number. Satellite cells are activated in the very early stages of training; their proliferation and later fusion with existing fibres appears to be intimately involved in the hypertrophy response. Other possible morphological adaptations include hyperplasia, changes in fibre type, muscle architecture, myofilament density and the structure of connective tissue and tendons. Indirect evidence for neurological adaptations, which encompasses learning and coordination, comes from the specificity of the training adaptation, transfer of unilateral training to the contralateral limb and imagined contractions. The apparent rise in whole-muscle specific tension has been primarily used as evidence for neurological adaptations; however, morphological factors (e.g. preferential hypertrophy of type 2 fibres, increased angle of fibre pennation, increase in radiological density) are also likely to contribute to this phenomenon. Changes in inter-muscular coordination appear critical. Adaptations in agonist muscle activation, as assessed by electromyography, tetanic stimulation and the twitch interpolation technique, suggest small, but significant increases. Enhanced firing frequency and spinal reflexes most likely explain this improvement, although there is contrary evidence suggesting no change in cortical or corticospinal excitability. The gains in strength with HRST are undoubtedly due to a wide combination of neurological and morphological factors. Whilst the neurological factors may make their greatest contribution during the early stages of a training programme, hypertrophic processes also commence at the onset of training.
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SUMMARY In order to stimulate further adaptation toward specific training goals, progressive resistance training (RT) protocols are necessary. The optimal characteristics of strength-specific programs include the use of concentric (CON), eccentric (ECC), and isometric muscle actions and the performance of bilateral and unilateral single- and multiple-joint exercises. In addition, it is recommended that strength programs sequence exercises to optimize the preservation of exercise intensity (large before small muscle group exercises, multiple-joint exercises before single-joint exercises, and higher-intensity before lower-intensity exercises). For novice (untrained individuals with no RT experience or who have not trained for several years) training, it is recommended that loads correspond to a repetition range of an 8-12 repetition maximum (RM). For intermediate (individuals with approximately 6 months of consistent RT experience) to advanced (individuals with years of RT experience) training, it is recommended that individuals use a wider loading range from 1 to 12 RM in a periodized fashion with eventual emphasis on heavy loading (1-6 RM) using 3- to 5-min rest periods between sets performed at a moderate contraction velocity (1-2 s CON; 1-2 s ECC). When training at a specific RM load, it is recommended that 2-10% increase in load be applied when the individual can perform the current workload for one to two repetitions over the desired number. The recommendation for training frequency is 2-3 dIwkj1 for novice training, 3-4 dIwkj1 for intermediate training, and 4-5 dIwkj1 for advanced training. Similar program designs are recom- mended for hypertrophy training with respect to exercise selection and frequency. For loading, it is recommended that loads corresponding to 1-12 RM be used in periodized fashion with emphasis on the 6-12 RM zone using 1- to 2-min rest periods between sets at a moderate velocity. Higher volume, multiple-set programs are recommended for maximizing hypertrophy. Progression in power training entails two general loading strategies: 1) strength training and 2) use of light loads (0-60% of 1 RM for lower body exercises; 30-60% of 1 RM for upper body exercises) performed at a fast contraction velocity with 3-5 min of rest between sets for multiple sets per exercise (three to five sets). It is also recommended that emphasis be placed on multiple-joint exercises especially those involving the total body. For local muscular endurance training, it is recommended that light to moderate loads (40-60% of 1 RM) be performed for high repetitions (915) using short rest periods (G90 s). In the interpretation of this position stand as with prior ones, recommendations should be applied in context and should be contingent upon an individual's target goals, physical capacity, and training
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The squat is a closed-chain lower body exercise commonly performed by many athletes. Muscle activity has been examined during partial and parallel squats in male weightlifters, but not in male and female runners. Therefore, this study measured muscle activity with surface electromyography (EMG) during partial and parallel squats in 20 Division I collegiate cross-country runners (10 males and 10 females) in a randomized crossover design. We hypothesized the parallel squat would increase extensor muscle activitation (i.e., hamstrings and erector spinae). Furthermore, we sought to determine if changes in muscle activity were different between males and females. Participants performed 6 repetitions using their 10 repetition maximum loads for each condition during EMG testing. EMG was performed on the right rectus femoris, biceps femoris, lumbar erector spinae, and lateral head of the gastrocnemius. Rectus femoris activity (0.18±0.01 vs. 0.14±0.01 mV) and erector spinae activity (0.16±0.01 vs. 0.13±0.01 mV) were significantly higher (p<0.05) during the parallel squat than during the partial squat condition. This increase in muscle activity may be attributed to greater ranges of motion at the hip and knee joints. Biceps femoris and gastrocnemius activity were similar between conditions. No significant differences existed between males and females (squat condition x gender; p>0.05). During preliminary isokinetic testing, both male and female runners demonstrated deficient hamstrings-to-quadriceps ratios, which would not likely improve by performing parallel squats based on our EMG findings. Despite the reduced load of the parallel squat, rectus femoris and erector spinae activity were elevated. Thus, parallel squats may help runners to train muscles vital for uphill running and correct posture, while preventing injury by using lighter weights through a larger range of motion.
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The purpose of the study was to compare six-repetition maximum (6-RM) loads and muscle activity in bench press on three surfaces, namely stable bench, balance cushion and Swiss ball. 16 healthy, resistance-trained males (age 22.5±2.0 years, stature 1.82±6.6 m, and body mass 82.0±7.8 kg) volunteered for three habituation/strength testing sessions, and one experimental session. In randomized order on the three surfaces, 6-RM strength and electromyographic activity of pectoralis major, deltoid anterior, biceps brachii, triceps brachii, rectus abdominis, oblique external and erector spinae were assed. Relative to stable bench, the 6-RM strength was ∼93% for balance cushion (P≤0.001) and ∼92% for Swiss ball (P=0.008); the pectoralis major EMG activity was ∼90% using the balance cushion (P=0.080) and ∼81% using Swiss ball (P=0.006); the triceps EMG was ∼79% using the balance cushion (P=0.028) and ∼69% using the Swiss ball (P=0.002). Relative to balance cushion, the EMG activity in pectoralis, triceps and erector spinae using Swiss ball was ∼89% (P=0.016), ∼88% (P=0.014) and ∼80% (P=0.020), respectively. In rectus abdominis, the EMG activity relative to Swiss ball was ∼69% using stable bench (P=0.042) and ∼65% using the balance cushion (P=0.046). Similar EMG activities between stable and unstable surfaces were observed for deltoid anterior, biceps brachii and oblique external. In conclusion, stable bench press had greater 6-RM strength and triceps and pectoralis EMG activity compared to the unstable surfaces. These findings have implications for athletic training and rehabilitation, as they demonstrate an inferior effect of unstable surfaces on muscle activation of prime movers and strength in bench press. If an unstable surface in bench press is desirable, a balance cushion should be chosen instead of a Swiss ball.
Article
The purpose of the study was to compare force output and muscle activity of leg and trunk muscles in isometric squats executed on stable surface (i.e. floor), power board, BOSU ball and balance cone. Fifteen healthy males (23.3 ± 2.7 years, mass: 80.5 ± 8.5 kg, height: 1.81 ± 0.09 m) volunteered. The force output and electromyographic (EMG) activities of the rectus femoris, vastus medialis, vastus lateralis, biceps femoris, soleus, rectus abdominis, oblique external and erector spinae were assessed. The order of the surfaces was randomized. One familiarization session was executed prior to the experimental test. Compared to stable surface (749 ± 222 N), the force output using power board was similar (-7%, P = 0.320), but lower for BOSU ball (-19%, P = 0.003) and balance cone (-24%, P ≤ 0.001). The force output using BOSU ball and balance cone was ∼13% (P = 0.037) and ∼18% (P = 0.001) less than the power board. There were similar EMG activities between the surfaces in all muscles except for rectus femoris, in which stable squat provided greater EMG activity than the other exercises (P = 0.004 - 0.030). Lower EMG activity was observed in rectus femoris using balance cone compared to BOSU ball (P = 0.030). In conclusion, increasing the instability of the surface during maximum effort isometric squats usually maintains the muscle activity of lower limb and superficial trunk muscles although the force output is reduced. This suggests that unstable surfaces in the squat may be beneficial in rehabilitation and as a part of periodized training programs, as similar muscle activity can be achieved with reduced loads.
Article
Unilateral and bilateral lower-body heavy resistance exercises (HREs) are used for strength training. Little research has examined whether muscle activation and testosterone (TES) responses differ between these exercises. Our purpose was to compare the effects of unilateral and bilateral lower-body HRE on muscle activity using surface electromyography (sEMG) and TES concentrations. Ten resistance-trained, college-aged male athletes (football, track and field) completed 5 testing sessions in which bilateral (back squat [BS]) and unilateral (pitcher squat [PS]) exercises were performed using a counterbalanced design. Sessions 1 and 2 determined estimated maximum strength (10 repetition maximum [10RM]) in the BS and PS. During testing session 3, muscle activation (sEMG) was measured in the right vastus lateralis, biceps femoris, gluteus maximus, and erector spinae (ES) during both BS and PS (stance leg) exercises. In sessions 4 and 5, total TES concentrations (nanomoles per liter) were measured via blood draws at baseline (preexercise), 0, 5, 10, 15, and 30 minutes postexercise after 4 sets of 10 repetitions at the 10RM. Separate repeated-measures analyses of variance examined differences in sEMG and TES between BS and PS (p < 0.05). The sEMG amplitudes were similar (p = 0.80) for BS (0.22 ± 0.06 mV) and PS (0.20 ± 0.07 mV). The TES responses were also similar (p = 0.15) between BS (21.8 ± 6.9 nmol·L(-1)) and PS (26.2 ± 10.1 nmol·L(-1)). The similar lower limb and back sEMG and TES responses may indicate that the neuromuscular and hormonal demands were comparable for both the BS and PS exercises despite the absolute work being less in the PS. The PS exercise may be an effective method for including unilateral exercise into lower-body resistance training when designing training programs for ground-based activities.
Article
The optimal volume of resistance exercise to prescribe for trained individuals is unclear. The purpose of this study was to randomly assign resistance trained individuals to 6-weeks of squat exercise, prescribed at 80% of a 1 repetition-maximum (1-RM), using either one, four, or eight sets of repetitions to failure performed twice per week. Participants then performed the same peaking program for 4-weeks. Squat 1-RM, quadriceps muscle activation, and contractile rate of force development (RFD) were measured before, during, and after the training program. 32 resistance-trained male participants completed the 10-week program. Squat 1-RM was significantly increased for all groups after 6 and 10-weeks of training (P < 0.05). The 8-set group was significantly stronger than the 1-set group after 3-weeks of training (7.9% difference, P < 0.05), and remained stronger after 6 and 10-weeks of training (P < 0.05). Peak muscle activation did not change during the study. Early (30, 50 ms) and peak RFD was significantly decreased for all groups after 6 and 10-weeks of training (P < 0.05). Peak isometric force output did not change for any group. The results of this study support resistance exercise prescription in excess of 4-sets (i.e. 8-sets) for faster and greater strength gains as compared to 1-set training. Common neuromuscular changes are attributed to high intensity squats (80% 1-RM) combined with a repetition to failure prescription. This prescription may not be useful for sports application owing to decreased early and peak RFD. Individual responsiveness to 1-set of training should be evaluated in the first 3-weeks of training.
Article
The objective of this study was to compare the production of force and paraspinal muscle activity between deadlifts carried out in a standard way and with different instability devices (Bosu and T-Bow). Deadlifts involve the performance of muscle activities with dynamic and isometric characteristics. Thirty-one subjects participated voluntarily in the study. Initially, they performed an isometric test for 5 seconds in each condition. After that, they performed a set of 5 repetitions with 70% of the maximum isometric force obtained in each one of the previously evaluated conditions. During the isometric tests, records of electromyographic activity and force production were obtained, whereas during the dynamic tests, only the electromyographic activity was registered. The subjects produced more force and muscle activity on the stable surface than under the other conditions during the isometric test (p < 0.05), and the same differences in muscle activity were observed during the dynamic test (p < 0.05). These data show that the performance of deadlifts under stable conditions favors a higher production of maximum strength and muscle activity. Therefore, we conclude that the use of instability devices in deadlift training does not increase performance, nor does it provide greater activation of the paraspinal muscles, leading us to question their value in the performance of other types of exercises.
Article
The purpose of this investigation was to determine the effect of stable and unstable conditions on one repetition maximum strength and muscle activity during dynamic squatting using absolute and relative loading. Ten recreationally weight-trained males participated in this study (age = 24.1 +/- 2.0 y, height = 178.0 +/- 5.6 cm, body mass = 83.7 +/- 13.4 kg, 1RM/body mass = 1.53 +/- 0.31), which involved two laboratory sessions separated by 1 wk. Linear position transducers were used to track bar displacement while subjects stood on a force plate for all trials. Vastus lateralis (VL), biceps femoris (BF) and erector spinae (L1) muscle activity (average integrated EMG [IEMG]) was also recorded during all trials. During the first session subjects complete a one repetition maximum test in a stable dynamic squat (S1RM = 128.0 +/- 31.4 kg) and an unstable dynamic squat (U1RM = 83.8 +/- 17.3 kg) in a randomized order with a 30-min rest period between conditions. The second session consisted of the performance of three trials each for 12 different conditions (unstable and stable squats using three different absolute loads [six conditions] and unstable and stable squats using three different relative loads [six conditions]). Results revealed a statistically significant difference between S1RM and U1RM values (P < or = .05). The stable trials resulted in the same or a significantly higher value for VL, BF and L1 muscle activity in comparison with the unstable trials for all twelve conditions. Unstable squatting is of equal or less (depending on the loading condition) benefit to improving or maximizing muscle activity during resistance exercise.
Article
In an attempt to mimic everyday activities that are performed in 3-dimensional environments, exercise programs have been designed to integrate training of the trunk muscles with training of the extremities. Many believe that the most effective way to recruit the core stabilizing muscles is to execute traditional exercise movements on unstable surfaces. However, physical activity is rarely performed with a stable load on an unstable surface; usually, the surface is stable, and the external resistance is not. The purpose of this study was to evaluate muscle activity of the prime movers and core stabilizers while lifting stable and unstable loads on stable and unstable surfaces during the seated overhead shoulder press exercise. Thirty resistance-trained subjects performed the shoulder press exercise for 3 sets of 3 repetitions under 2 load (barbell and dumbbell) and 2 surface (exercise bench and Swiss ball) conditions at a 10 repetition maximum relative intensity. Surface electromyography (EMG) measured muscle activity for 8 muscles (anterior deltoid, middle deltoid, trapezius, triceps brachii, rectus abdominis, external obliques, and upper and lower erector spinae). The average root mean square of the EMG signal was calculated for each condition. The results showed that as the instability of the exercise condition increased, the external load decreased. Triceps activation increased with external resistance, where the barbell/bench condition had the greatest EMG activation and the dumbbell/Swiss ball condition had the least. The upper erector spinae had greater muscle activation when performing the barbell presses on the Swiss ball vs. the bench. The findings provide little support for training with a lighter load using unstable loads or unstable surfaces.
Article
The purpose of this experiment was to determine whether free weight or Smith machine squats were optimal for activating the prime movers of the legs and the stabilizers of the legs and the trunk. Six healthy participants performed 1 set of 8 repetitions (using a weight they could lift 8 times, i.e., 8RM, or 8 repetition maximum) for each of the free weight squat and Smith machine squat in a randomized order with a minimum of 3 days between sessions, while electromyographic (EMG) activity of the tibialis anterior, gastrocnemius, vastus medialis, vastus lateralis, biceps femoris, lumbar erector spinae, and rectus abdominus were simultaneously measured. Electromyographic activity was significantly higher by 34, 26, and 49 in the gastrocnemius, biceps femoris, and vastus medialis, respectively, during the free weight squat compared to the Smith machine squat (p < 0.05). There were no significant differences between free weight and Smith machine squat for any of the other muscles; however, the EMG averaged over all muscles during the free weight squat was 43% higher when compared to the Smith machine squat (p < 0.05). The free weight squat may be more beneficial than the Smith machine squat for individuals who are looking to strengthen plantar flexors, knee flexors, and knee extensors.
Article
Many strength trainers believe that varying the stance width during the back squat can target specific muscles of the thigh. The aim of the present work was to test this theory measuring the activation of 8 thigh muscles while performing back squats at 3 stance widths and with 3 different bar loads. Six experienced lifters performed 3 sets of 10 repetitions of squats, each one with a different stance width, using 3 resistances: no load, 30% of 1-repetition maximum (1RM), and 70% 1RM. Sets were separated by 6 minutes of rest. Electromyographic (EMG) surface electrodes were placed on the vastus medialis, vastus lateralis, rectus femoris, semitendinosus, biceps femoris, gluteus maximus, gluteus medium, and adductor maior. Analysis of variance and Scheffè post hoc tests indicated a significant difference in EMG activity only for the gluteus maximus; in particular, there was a higher electrical activity of this muscle when back squats were performed at the maximum stance widths at 0 and 70% 1RM. There were no significant differences concerning the EMG activity of the other analyzed muscles. These findings suggest that a large width is necessary for a greater activation of the gluteus maximus during back squats.
Article
This study evaluated the biceps femoris (BF), rectus femoris (RF), and vastus lateralis (VL) activation and activation ratios of a variety of resistance training exercises characterized by knee extension, and determined if subject strength or gender affects these variables. The exercises evaluated included the leg extension, squat, deadlift, lunge, and step up. Subjects included 20 athletes and recreationally active college students. Electromyography (EMG) of the muscles expressed as a percentage of maximum voluntary isometric contraction (MVIC), as well as the BF to RF and BF to VL EMG ratio, were determined for each exercise. There was no significant interaction between gender and exercise type for the RMS EMG of the BF (p = 0.67), RF (p = 0.53), or VL (p = 0.06). Main effects were found for the RMS EMG of the BF (p = 0.00), RF (p = 0.00), and VL (p = 0.00), as well as the RMS EMG of the BF to RF activation ratio (p = 0.00) and BF to VL activation ratios (p = 0.003), between exercises. Peak RMS EMG was also assessed. Post hoc analysis identified specific differences in muscle activation and ratios between exercises. Clinicians should consider the magnitude of muscle activation and activation ratios when prescribing hamstring and quadriceps exercises.
Article
Eleven male subjects went through heavy resistance strength training 3 times a week for 16 weeks. The training program consisted mainly of dynamic exercise for the knee extensor muscles with loads of 80%-120% of one maximum repetition in the squat lift. The investigation was undertaken to examine effects of strength training on neuromuscular performance both in voluntary and reflex contractions with special interest in their possible relationships. In addition to a large (P less than 0.001) increase in maximal isometric force and a more (P less than 0.05) economical activation of the knee extensor muscles, significant (P less than 0.05) improvements were noted in isometric force-time parameters, which were related (P less than 0.05) to the increase in the fast-twitch/slow-twitch (FT/ST) muscle fiber area ratio. No changes were observed in reflex time components, but the relative change in reflex electromechanical delay (EMD) was related (P less than 0.05) to the relative change in the FT/ST area ratio. A significant (P less than 0.05) decrease in the peak-to-peak amplitude of the reflex electromyogram (EMG), was noted during the training, and a decrease (P less than 0.05) in reflex EMG/force ratio was related (P less than 0.02) to the change in maximal integrated electromyogram (iEMG)/force ratio of the voluntary contraction. The decrease of reflex EMG may indicate a change in sensitivity of the muscle spindle. The interrelationship between the changes in EMG/force ratios of the reflex and voluntary contractions suggests that the mechanical response of individual muscle fibers of the respective motor units has improved.
Article
The knowledge of surface electromyography (SEMG) and the number of applications have increased considerably during the past ten years. However, most methodological developments have taken place locally, resulting in different methodologies among the different groups of users.A specific objective of the European concerted action SENIAM (surface EMG for a non-invasive assessment of muscles) was, besides creating more collaboration among the various European groups, to develop recommendations on sensors, sensor placement, signal processing and modeling. This paper will present the process and the results of the development of the recommendations for the SEMG sensors and sensor placement procedures. Execution of the SENIAM sensor tasks, in the period 1996-1999, has been handled in a number of partly parallel and partly sequential activities. A literature scan was carried out on the use of sensors and sensor placement procedures in European laboratories. In total, 144 peer-reviewed papers were scanned on the applied SEMG sensor properties and sensor placement procedures. This showed a large variability of methodology as well as a rather insufficient description. A special workshop provided an overview on the scientific and clinical knowledge of the effects of sensor properties and sensor placement procedures on the SEMG characteristics. Based on the inventory, the results of the topical workshop and generally accepted state-of-the-art knowledge, a first proposal for sensors and sensor placement procedures was defined. Besides containing a general procedure and recommendations for sensor placement, this was worked out in detail for 27 different muscles. This proposal was evaluated in several European laboratories with respect to technical and practical aspects and also sent to all members of the SENIAM club (>100 members) together with a questionnaire to obtain their comments. Based on this evaluation the final recommendations of SENIAM were made and published (SENIAM 8: European recommendations for surface electromyography, 1999), both as a booklet and as a CD-ROM. In this way a common body of knowledge has been created on SEMG sensors and sensor placement properties as well as practical guidelines for the proper use of SEMG.
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The purpose of this study was to compare pure eccentric and concentric strength training regarding possible specific effects of muscle action type on neuromuscular parameters, such as a decreased inhibition during maximal voluntary eccentric actions. Two groups of young healthy adult men performed 10 weeks of either eccentric or concentric unilateral isokinetic knee extensor training at 90 degrees.s(-1), 4 sets of 10 maximal efforts, 3 days a week. Knee extensor torque and surface EMG from the quadriceps and hamstring muscle groups were collected and quantified in a window between 30 and 70 degrees knee angle (range of motion 90-5 degrees ) during maximal voluntary eccentric and concentric knee extensor actions at 30, 90, and 270 degrees.s(-1). Changes in strength of the trained legs revealed more signs of specificity related to velocity and contraction type after eccentric than concentric training. No major training effects were present in eccentric to concentric ratios of agonist EMG or in relative antagonist (hamstring) activation. Thus, for the trained leg, the muscle action type and speed specific changes in maximal voluntary eccentric strength could not be related to any effects on neural mechanisms, such as a selective increase in muscle activation during eccentric actions. Interestingly, with both types of training there were specific cross-education effects, that is, action type and velocity specific increases in strength occurred in the contralateral, untrained, leg, accompanied by a specific increase in eccentric to concentric EMG ratio after eccentric training.
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The purpose of this study was to compare the effects of short-term unilateral resistance training (UL) and bilateral resistance training (BL) with free weights on several tests of unilateral and bilateral lower-body strength and power in men and women. Thirty-eight untrained men and women (mean body mass 78.3 +/- 21.47 kg; age 20.74 +/- 2.6 years) completed the study. The groups trained 2 days per week for 8 weeks with free weights and 2 days per week for 5 of the 8 weeks with plyometric drills. The resistance-training program consisted of a progression from 3 sets of 15 repetitions at 50% of the subject's predicted 1 repetition maximum (1RM) to 6 sets of 5 repetitions at 87% 1RM. Training volume and intensity were equal for each group. The free-weight squat was used to measure unilateral and bilateral strength. Power was measured by the Magaria-Kalamen stair-climb test and the unilateral and bilateral vertical jump test. Analysis of covariance was used to analyze differences between men and women and the interaction of group and gender. Pretest scores were used as the covariate. The UL group improved more than the BL group on the unilateral vertical jump height (p = 0.001) and relative power (p = 0.013). After adjusting for pretest differences, the improved scores on all tests, except for the unilateral squat, were similar between the men and the women. No significant interactions on all tests were found for the men or women comparison between training groups. These results indicate that UL and BL are equally effective for early phase improvement of unilateral and bilateral leg strength and power in untrained men and women.
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This review focuses on methods for extracting information from the surface EMG recorded in dynamic contractions. It examines the techniques, requirements, and limitations associated with detecting the timing of muscle activation, assessing the modulation of signal amplitude, performing EMG spectral analysis, and estimating conduction velocity. The conclusion is that interpretation of the surface EMG in dynamic tasks requires caution.
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The objective of this study was to determine differences in electromyographic (EMG) activity of prime mover and abdominal muscles while performing squats, push ups, and double leg lowering with a swiss ball. Twelve healthy subjects performed the movements. There was no difference between the surface conditions for muscle activity during the squat exercise; however, individuals had lower perceived exertion for the swiss ball squat. Activity of the triceps and abdominals was highest performing push ups on the swiss ball, whereas the activity of rectus abdominus (RA) only increased during double leg lowering on the swiss ball. Perceived exertion was highest for the push up and leg-lowering exercise performed on the swiss ball. Increased RA activity during double leg lowering can be attributed to its role as a hip flexor, whereas the lack of a rotation aspect to the task prevented increased oblique muscle activity. The swiss ball appears to only increase muscle activity during exercises where the unstable surface is the primary base of support.
Article
The purpose of this study was to assess the effect of stable vs. unstable conditions on force output and muscle activity during an isometric squat. Nine men involved in recreational resistance training participated in the investigation by completing a single testing session. Within this session subjects performed isometric squats either while standing directly on the force plate (stable condition, S) or while standing on inflatable balls placed on top of the force plate (unstable condition, U). Electromyography (EMG) was recorded during both conditions from the vastus lateralis (VL), vastus medialis (VM), biceps femoris (BF), and medial gastrocnemius (G) muscles. Results indicated peak force (PF) and rate of force development (RFD) were significantly lower, 45.6% and 40.5% respectively, in the U vs. S condition (p < or = 0.05). Average integrated EMG values for the VL and VM were significantly higher in the S vs. U condition. VL and VM muscle activity was 37.3% and 34.4% less in U in comparison to S. No significant differences were observed in muscle activity of the BF or G between U and S. The primary finding in this investigation is that isometric squatting in an unstable condition significantly reduces peak force, rate of force development, and agonist muscle activity with no change in antagonist or synergist muscle activity. In terms of providing a stimulus for strength gain no discernable benefit of performing a resistance exercise in an unstable condition was observed in the current study.