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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...
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Context 1
... TLS and MSLS. 15 The final ground electrode was placed on the tibial tuberosity. Before EMG analysis, the subject abducted the thigh while standing to detect the presence of gluteus medius activity, flexed the knee to detect hamstring activity, and extended the knee to detect quadriceps activ- ity and ensure that excessive noise (3 mV) did not occur. A marker was inserted into the raw sEMG signal to designate the beginning, point of full flexion, and end of each squat. Eighty-five percent of the subject’s 3RM on the TLS and MSLS was used for the TLS and MSLS EMG test. The subjects completed 3 repetitions on the TLS and MSLS during 1 session in randomized order with a 5-minute rest between exercise tests to determine the EMG recruitment levels. After a proper warm-up and dynamic stretches, 2 warm-up sets were completed using light loads. The MSLS EMG tests were performed while standing on a force plate (Zelocity, Scottsdale, AZ) to determine the percentage of the resistance supported on each leg. The audio feedback monitor was used to help subjects attain the parallel squat position. To reproduce natural technique that would be executed during training, the subjects performed the repetitions at their own pace. During video analysis, the cameras were positioned 90° to the sagittal and frontal planes while aligned with the bar and dominant leg. Video and EMG data could not be synchronized for analysis. The digitized points for the sagittal plane included passive reflective ball markers that were placed on the dorsal aspect of the fifth metatarsal, lateral malleolus, fibular head, femoral condyle, greater tro- chanter of the femur, iliac crest, and the lateral aspect of the barbell. The frontal- plane points included the midpoint between malleoli, below the tibial tuberosity, and the anterosuperior iliac spine prominence. For each view, manual digitizing was performed for 6 frames with automatic digitization for the following frames. Maximum angles of trunk inclination and dynamic knee valgum were identified for each trial under each condition and then averaged for analysis. Trunk inclination was measured as the angle of the segment from the iliac crest to the end of the bar as it deviated from the sagittal plane, and knee valgum was defined as the deviated angle in the frontal plane using the segment from the midmalleoli to the patella. For EMG collection the gain was set at 500 with a common-mode rejection ratio of 110 dB. Raw-data acquisition occurred with a bandwidth setting of 10 to 500 Hz. The location of muscle activation was determined first using the Hodges and Bui 16 detection algorithm. The raw signal was then smoothed using the root mean square with a 50-millisecond window. A linear-envelope technique for each muscle yielded the mean electrical activity. The mean peak electrical activity was derived by a linear envelope of 0.25 seconds surrounding the peak mV activity (0.125 seconds above and below) for each repetition and was calculated from the mean peak scores of the 3 repetitions for each muscle. Mean EMG was calculated by averaging the 3 mean EMG scores during each repetition. The dependent variables analyzed were the mean and mean peak EMG levels of the gluteus medius, quadriceps (isolation of rectus femoris), and hamstrings (isolation of biceps femoris) and the mean quadriceps-to-hamstrings ratio. Initial descriptive analysis of the data for the 11 participants indicated violations of the assumption of normally distributed data for each of the variables. A visual inspection of stem- and-leaf graphs indicated a bimodal distribution that was consistent across each of the variables. The population distribution of the paired differences was sym- metric, so the data were analyzed using nonparametric Wilcoxon signed rank tests for matched pairs. Each Wilcoxon test paired data for the MSLS with the TLS for each of the muscle areas measured. Tests provided z -score and probability values for interpretation. Paired t tests were used to compare differences in maximum dynamic trunk inclination and knee-valgum angle with significance set at P = .05. EMG scores were not normalized due to the within-subject analysis because each muscle group’s EMG data were compared between the MSLS and TLS, which was performed at the same relative intensity in the same session. Reported EMG activity indicated different hip and knee muscle-activation patterns for the TLS and the MSLS (Table 1). Statistically significant increases in muscle activation from the TLS to the MSLS were found for mean gluteus medius ( P < .01), mean peak gluteus medius ( P < .05), mean hamstring ( P < .01), and mean peak hamstring ( P < .01). For the TLS there was a statistically significant increase in activation (over the MSLS) for mean quadriceps ( P < .05), mean peak quadriceps, and the mean quadriceps:hamstring (Q:H) EMG ( P < .01). The median differ- ences in the mean scores (average of 3 repetitions) from the MSLS to the TLS are shown in Figure 3, which shows that the MSLS produced higher demands on the gluteus medius and hamstring while the TLS required increased activity from the quadriceps. The mean Q:H EMG ratio for the TLS (4.87) was significantly higher than for the MSLS (1.67; P < .01). Maximum trunk inclination was significantly higher during the TLS (40.65° ± 7.0° vs 33.68° ± 7.6°; P < .05), and maximum knee-valgum angle was significantly higher during the MSLS (29.4° ± 7.4° vs 21.9° ± 6.9°; P < .01). The findings of our study revealed that higher hamstring and lower quadriceps activity occurred during the MSLS than when performing the TLS at the same relative intensity. During a squat motion, higher hamstring and lower quadriceps activity are suggested to occur with greater hip flexion because of an increase in the moment of force at the hip and a decrease at the knee. 17 In our study mean maximum trunk inclination on the TLS (40.65°), calculated from the 3 repetitions, was greater than the trunk inclination on the MSLS (33.68°). The results from our study indicated that the greater hip flexion during the TLS had minimal effect on hamstring activity. The results are in agreement with those of Caterisano et al, 7 who found no significant change in hamstring activity as the depth of a squat increased along with increased hip flexion. The reduced base of support during the MSLS appeared to have a greater effect on hamstring activity than an increase in trunk inclination during the TLS. The gluteus maximus and trunk musculature may be most active to support the load as trunk inclination increased during the TLS. Greater hip and trunk flexion during a TLS are typically related to less anterior translation of the knee to position the mass over the base of support. To control for possible differences in the movement patterns and moments of force at each joint between the 2 types of squat, the subjects practiced performing the MSLS with the lead knee positioned above the toes similar to the degree of anterior translation of the knee performed during the TLS. Although several investigations have determined that muscle activity is high in selected lower body muscle groups during the SLS and step-ups, 10–12 low hamstring activity has been found relative to quadriceps activity. 1,2,10–12,18 In contrast to our study, the subjects in those studies performed a body-weight SLS, and Ayotte et al 10 also allowed the subjects to support the body with a hand on a wall during several unilateral weight-bearing exercises. Subjects in the study by Ayotte et al 10 produced 9% to 15% MVIC hamstring activity and 55% to 66% MVIC in the quadriceps, resulting in EMG amplitude Q:H ratios between 4 and 6. However, Youdas et al 19 reported higher hamstring activity relative to quadriceps activity in men (2.52 H:Q ratio) and women (0.71 H:Q ratio) during unstable SLS using body-weight resistance than when performing the SLS squat on a stable surface, 2.25 and 0.62 H:Q ratio, respectively. This previous study suggested that highly unstable squats stimulate an increase in hamstring activity. Our findings also indicated that the moderately unstable MSLS produced a relatively low ratio (1.67) of Q:H recruit- ment, possibly resulting from the reduced mediolateral base of support and the relatively high resistance. Besier et al 20 found that hamstring-activation patterns occurred during sidestepping and crossover maneuvers to counter varus/valgus and internal/external moments at the knee. In our study higher maximum knee-valgus angles occurred during the MSLS. In addition, we observed several abrupt reversals in movement toward knee varus and valgus directions during each repetition of the MSLS. Thus, biceps femoris activation could have occurred to provide eccentric support during the return from the valgus position. Besier et al 20 concluded that the biceps femoris is active to resist knee internal-rotation moments and produce knee external rotation. Although not measured in our study, knee internal rotation is common during knee-valgus motion 20 and likely occurred during the MSLS. We speculated that biceps femoris recruitment was needed to resist knee internal rota- tion and produce knee external rotation. Further studies are needed to determine specific activation patterns of all 3 hamstrings with analysis of knee varus/valgus and internal/external rotation motions during the MSLS and TLS. Several studies have reported high quadriceps and low hamstring activation during the TLS. 7,8,21 Yamashita 22 suggested that low hamstring activation is caused by the inhibition of the muscle during its role as an antagonist with simultaneous hip and knee extension. The mean Q:H EMG ratio found in our study during the TLS (4.87) is similar to results in those previous studies. 7,8,21 The higher quadriceps activity during the TLS is likely a result of the ability to support a portion of the load on the trail leg to assist knee flexion and extension during the MSLS. Higher ...
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Citations
... Closed kinetic exercises are similar to many functional movements and have been suggested for rehabilitation exercises because they result in a reduced shear force on the knee joint compared with open kinetic exercises [12]. In addition, closed kinetic exercises demonstrated significantly greater GM activity than open kinetic exercises [13]. ...
... Performance of single-legged squats are extensively investigated as an exercise for knee injury prevention or rehabilitation exercise. 32,[34][35][36][37][38][39] The present data corroborate previous studies in showing highly increased levels of quadriceps activity for all balance devices, compared to single-leg stance, but a more moderate increase in mean peak hamstring activity. Although the increase in hamstring activity relative to single-leg stance was significant for the Airex and the floor, single-leg squat on BOSU still required larger levels of hamstring activation compared to the less demanding devices. ...
Background
In injury prevention or rehabilitation programs, exercises that facilitate enhanced hamstring activity may be beneficial when aiming to enhance knee joint stability during movements in sports with higher risk of acute knee injury. Information about neuromuscular activation of the hamstring muscles in commonly used exercises may improve exercise selection and progression in programs for knee injury prevention or rehabilitation.
Purpose
To investigate (1) how balance devices with progressing degrees of instability influence the activity of muscles controlling the knee joint in typical balance exercises with different demands on postural control, and (2) if any between-sex differences exist.
Study design
Cross-sectional study.
Methods
Twenty habitually active healthy adults (11 males) participated in this cross-sectional study. Single-leg stance, single-leg squat and single-leg landing were performed on the floor and two different balance devices imposing various levels of challenge to postural control. Three-dimensional motion analysis was used to obtain hip and knee joint angles, and as primary outcomes, and peak normalized EMG activity from the hamstrings and quadriceps muscles was measured for comparison between exercises.
Results
The more challenging in terms of maintaining stable balance the devices were, the higher hamstring muscle activity levels were observed. There was a clear progression across balance devices from single-leg stance to single-leg squat and further to single-leg landing displaying increasing hamstring activity levels. The change in medial hamstring activity across all devices when changing from single-leg squat to single-leg landing was significantly higher for the female participants than for the males reaching a higher level of activity.
Conclusion
The muscle activity of the hamstrings and quadriceps increased when the motor task was more dynamic. Specifically, single-leg landings were effective in increasing the hamstring muscle activity over the single-leg stance to single-leg squat exercises, and muscle activity was significantly increased with the most unstable device. Increases in hamstring muscle activation was greater in female subjects than males with increasing instability of the balance devices.
Trial identifier
Not registered.
Level of evidence
3
... In addition, there are concerns over the effectiveness of the squat, a bilateral exercise, in sports that require brief temporary weight support with only a unilateral lower extremity. Thus, there are current discussions regarding whether unilateral exercises may be efficient alternatives to bilateral exercises [7,8], and various unilateral exercises have been introduced to compensate for such limitations [9]. ...
... Unilateral squats also possess distinctive characteristics from the conventional DLBS for strength or hypertrophic training effect on the knee and hip extensors. In particular, the dominantly trained muscles differ among the unilateral and bilateral squat variations (8,9,16,18,23). Concerning this issue, most studies have used electromyography (EMG) to determine which muscle particularly contributes in RFESS (1,2,8,14,23). Some of these studies compared DLBS and RFESS and reported that the RFESS was more hip extensor-dominant than the DLBS (2,8,18), but other studies did not find evidence to support this hypothesis (9,14). ...
... In particular, the dominantly trained muscles differ among the unilateral and bilateral squat variations (8,9,16,18,23). Concerning this issue, most studies have used electromyography (EMG) to determine which muscle particularly contributes in RFESS (1,2,8,14,23). Some of these studies compared DLBS and RFESS and reported that the RFESS was more hip extensor-dominant than the DLBS (2,8,18), but other studies did not find evidence to support this hypothesis (9,14). ...
... Another explanation for the enhanced hip extension moment in the RFESS is the effect of the "rear leg-derived resistive moment (RRM)" on the hip extensors of the front leg. In the RFESS, a certain degree of the upward GRF is applied to the rear foot (23), which leads to the exertion of hip flexion moment in the rear limb. Given the Newton's third law of rotational motion, when some moment is exerted to one segment, then simultaneously opposite moment is exerted to the other segment. ...
Arakawa, H, Mori, M, and Tanimoto, M. Greater hip moments in rear-foot-elevated split squats than in conventional back squats with the same relative intensity of loads. J Strength Cond Res XX(X): 000-000, 2022-Rear-foot-elevated split squat (RFESS) is often performed as an alternative to conventional double-leg back squat (DLBS). This study aimed to compare 3-dimensional joint kinetics of DLBS and RFESS using the same relative intensity of loads. Eight male college rugby players performed 3 repetitions of DLBS and RFESS at 10-repetition-maximum (RM) loading. Before testing, both exercises were incorporated into the subjects' training program with a progressive increase in loads for 4 months. A 3-dimensional optical motion capture system and force platform were used for data collection. The 3-dimensional moments at the knee and hip joints in each of the 3 axes were calculated based on the inverse dynamic procedure. p values < 0.05 were considered statistically significant. The hip extension moment was 44% greater in the RFESS than in the DLBS at the bottom position (p < 0.01) and 47% greater for the peak value (p < 0.01) on harmonic averages. The hip abduction and external rotation moments at the bottom position were also greater in the RFESS than in the DLBS. The findings suggest that the magnitude of hip extension moment per leg in DLBS tends to be restricted to less than that expected from the given strength level. In conclusion, the mechanical contribution of hip extensors per leg can be greater in RFESS than in DLBS when using respective 10RM loads, even if the absolute load is smaller and the trunk is more upright in RFESS.
... However, a drawback of this exercise is the potential pain that it causes in athletes and non-athletes with trunk or knee problems [4]. It is not effective in sport situations requiring weight support on one side of the lower extremity either transiently or during a set period of time (such as sprint running, jumping or directional shift) [5,6], therefore, in such situations, unilateral exercises (such as lunge, single-leg squat, split squat, Bulgarian split squat (BSS) and step up) have been introduced as an alternative [4,7]. ...
... Bulgarian Split Squat is a unilateral exercise for muscle strengthening in the lower extremity with similarities to Split Squat (SS). To perform the BSS, the posterior foot gains support from a stable structure positioned at the back of the body and the anterior foot moves to a comfortable position to achieve balance, and the methods similar to that in SS are followed [6,13]. According to a previous study [5], BSS allows 85% of power on the anterior lower extremity because of which it can be used as an alternative to the conventional squat exercise. ...
... As the concentric phase was repeated, the peak EMG values of the rectus femoris and hamstring muscles were identified, and the mean peak values were used for 1 sec. [8] The dependent variables analyzed were the mean peak EMG levels of the quadriceps (separation of rectus femoris), and hamstrings (separation of biceps femoris) and the mean H: Q ratio [6]. ...
... Adicionalmente, Kornecki y Zschorlich (1994) observaron que los ejercicios de predominio unilateral requieren mayor participación y activación de musculatura estabilizadora que los bilaterales. Otros estudios (Boren, et al., 2011;Ebben, et al., 2009;McCurdy et al., 2010) que compararon ejercicios de estocadas, subidas al banco y sentadillas mediante electromiografía también reportaron que los ejercicios de predominio unilateral, además de producir una mayor activación de la musculatura estabilizadora, requieren mayor actividad del músculo glúteo medio, de vital importancia para la estabilización de rodilla y el control del movimiento. Esta necesidad de estabilizar para ejecutar resultaría en una menor actividad de la musculatura movilizadora principal. ...
Sprint speed and vertical jumping ability are fundamental requirements to reach high performance in soccer. There is controversy about the type of resistance exercise (bilateral or unilateral) that allows greater transfer to these gestures. The aim of this study was to compare the effect of strength training using squats vs lunges on vertical jump speed and 20-meter linear sprint in youth soccer players. Seventy-nine subjects randomly divided into three groups participated in the study: lunge training (GE) (n = 28; age = 16.5 ± 1.2 years); squat training (GS) (n = 24; age = 16.3 ± 1.4 years) and control group (GC) (n = 27; age = 16.5 ± 1.2 years). GE and GS performed strength training twice a week during 12 weeks. Before and after the intervention, all subjects were tested for maximum speed at CMJ and linear sprint of 20m. All three groups significantly improved performance (p < .05) in the 20m sprint, with the improvement being significantly greater in the experimental groups compared to GC (p < .05), with no differences between the former. No significant improvement in maximum speed at CMJ was verified for either group. Both bilateral and predominantly unilateral strength training appear to be beneficial for the improvement of sprint speed performance in youth soccer players, with no significant differences between them.
... The bilateral nature and large muscle mass recruited in these exercises allow the use of heavy absolute loads to elicit high relative intensities (i.e., > 85% 1-RM). Compound (i.e., multijoint) BL movements are advantageous over isolated, single joint lifts as they have larger gross motor unit recruitment (17)(18) and utilize different muscle groups simultaneously, producing acute hormonal responses associated with increased strength (19)(20). In contrast to BL, unilateral resistance training (UL) isolates one side of the body (17). ...
... Compound (i.e., multijoint) BL movements are advantageous over isolated, single joint lifts as they have larger gross motor unit recruitment (17)(18) and utilize different muscle groups simultaneously, producing acute hormonal responses associated with increased strength (19)(20). In contrast to BL, unilateral resistance training (UL) isolates one side of the body (17). Examples of UL resistance exercises include the Bulgarian split squat, single leg Romanian deadlift, and single arm dumbbell press. ...
... previously compared the effect of UL versus BL RT on lower body power during both UL and BL jump performance. Untrained participants completing eight-weeks of plyometric training plus either UL or BL RT improved similarly in the bilateral VJ, while UL participants showed greater improvement in the unilateral VJ(17). Gonzallo and colleagues (56) compared the effects of combining plyometric training with UL versus BL RT on performance measures in basketball players, and showed greater improvements in single-leg power output and agility following UL. ...
Purpose: To examine the effects of unilateral resistance training on lower body power, muscular strength, and measures of core stability in resistance-trained college students. Methods: Participants (N=22; mean age= 19.86 ± 0.9 years) underwent 10 sessions of either unilateral (UL) or bilateral (BL) resistance training on three non-consecutive days per week for three weeks. Pre and post training outcome measures included one repetition maximum (1-RM) leg press for lower body strength, standing vertical jump (VJ) for lower body power, and double leg lowering (DLL), hip abduction isometric strength (HAIS), and Sorensen (SOR) tests for core stability. Results: There was a significant (p≤ 0.05) main effect of time across all variables, such that both groups improved scores on 1-RM leg press, VJ, DLL, HAIS, and SOR. Additionally, the magnitude of improvement (Cohen’s d) was larger in UL for all variables except VJ, which was larger in the BL group. Conclusion: This study adds to the growing body of literature investigating the effects of UL resistance training in athletic populations. Similar improvements following UL or BL resistance training suggest that both methods can effectively enhance strength, power, and core stability. UL training may potentially yield greater improvement of core stability variables.
... Adicionalmente, Kornecki y Zschorlich (1994) observaron que los ejercicios de predominio unilateral requieren mayor participación y activación de musculatura estabilizadora que los bilaterales. Otros estudios (Boren, et al., 2011;Ebben, et al., 2009;McCurdy et al., 2010) que compararon ejercicios de estocadas, subidas al banco y sentadillas mediante electromiografía también reportaron que los ejercicios de predominio unilateral, además de producir una mayor activación de la musculatura estabilizadora, requieren mayor actividad del músculo glúteo medio, de vital importancia para la estabilización de rodilla y el control del movimiento. Esta necesidad de estabilizar para ejecutar resultaría en una menor actividad de la musculatura movilizadora principal. ...
La velocidad de sprint y la capacidad de salto vertical son requisitos fundamentales para alcanzar el alto rendimiento en fútbol. Existe controversia sobre el tipo de ejercicio de fuerza (bilateral o unilateral) que permite mayor transferencia a estos gestos. El objetivo del presente estudio fue comparar el efecto del entrenamiento de fuerza utilizando sentadillas vs estocadas sobre la velocidad de salto vertical y el sprint lineal en 20 metros en jugadores de fútbol juvenil. Participaron en el estudio 79 sujetos divididos aleatoriamente en tres grupos: entrenamiento con estocadas (GE) (n = 28; edad = 16,5 ± 1,2 años); entrenamiento con sentadillas (GS) (n = 24; edad = 16,3 ± 1,4 años) y grupo control (GC) (n = 27; edad = 16,5 ± 1,2 años). GE y GS realizaron entrenamiento de fuerza dos veces por semana. Previo y posterior a la intervención, todos los sujetos fueron testeados en velocidad máxima en CMJ y sprint lineal de 20m. Todos los grupos mejoraron significativamente el rendimiento (p < ,05) en el sprint en 20 m, verificándose una diferencia significativa entre los grupos experimentales y GC (p < ,05), sin diferencias entre los primeros. No se verificó una mejora significativa en la velocidad máxima en CMJ para ninguno de los grupos. Tanto el entrenamiento de fuerza bilateral como predominantemente unilateral parecen ser beneficiosos para la mejora del rendimiento en velocidad de desplazamiento horizontal en jugadores de fútbol de categoría juvenil.
... Including both in training is important to provide differences in demands and subsequent adaptations. Specifically, the wide medial-lateral stance target activation of the sagittal plane musculature while the SSJ narrow base of support activates the musculature involved in frontal plane control to a greater degree (25,26). Added loads to the body weight during jump performance using these different bases of support to assess optimum loads used in training to improve power performance (21) further challenges jump execution. ...
... The CMJ is bilateral while the SSJ is utilized to create primarily a unilateral-based, loading condition similar to those encountered in many sport actions and is specifically used to improve frontal plane control (27). The greater demand in the frontal plane during exercise with a split-squat-jump stance is evident with the narrow base of support and is supported by greater muscle activation in the trunk, hip and knee that control motion in the frontal plane (24,25). Even with these differences between jump types, there appeared to be no difference in the ability to execute the jumps as it was rare for participants to lose balance requiring to dismiss and repeat the trial. ...
The purpose of this study was to determine the relative and absolute reliability using PUSH Pro Band 2.0 IMU to measure peak velocity and power during the countermovement (CMJ) and split-squat jump (SSJ). Twenty-three resistance trained males and females completed the study. After a familiarization session, each subject completed 2 identical sessions separated by a minimum of 72 hours that included 4 loads during the CMJ (body weight, body weight plus 20, 40 and 60%) and SSJ (body weight, body weight plus 15, 30 and 45%). In each session, 3 repetitions were completed at each load in randomized order with 3 minutes rest between sets and 5 minutes rest between jump types. Dumbbells held to the side were used to add load. A waist belt was worn that contained the accelerometer. High relative (intra-class coefficient ranging from 0.86-0.99) and absolute (coefficient of variation ranging from 1.7-8.0%) reliability were found for all measures of peak velocity and power during the CMJ and SSJ. The PUSH device produced highly reliable measures of jump performance across all loads between trials and across sessions.
... This experimental test was not used for the comparison of muscle activity levels between the muscles. An amplitude comparison of the signals from a given muscle was conducted between the two exercise tasks within an individual in the same session, strictly under the same experimental conditions, and without altering the EMG electrodes 21,22 . The average value used for analysis (μV-s) was calculated and averaged over the three complete swings during the exercise task, and the mean values were used for analysis 23 . ...
Perturbation exercises enhance lower limb and trunk muscles, and adding swing perturbation while loading during exercise might improve muscle activation or strength. This study aimed to check variations in trunk and lower limb muscle activity during conventional isometric squats, and whether it will change with or without swing using the Hammerobics-synchronized squat method. Twelve healthy men participated in this study. Activities for the abductor hallucis, tibialis anterior, tibialis posterior, peroneus longus, rectus femoris, biceps femoris long head, semitendinosus, gluteus maximus, multifidus, and internal oblique muscles were measured using surface electromyography during a Hammerobics-synchronized squat and conventional isometric squat. Muscle activities were statistically compared between squat methods. Hammerobics-synchronized squats significantly activated the abductor hallucis, tibialis anterior, tibialis posterior, peroneus longus, semitendinosus, and multifidus muscles, in both phases, compared with the conventional isometric squats. The Hammerobics-synchronized squat exercise can be considered for trunk and foot stability exercise.
