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Interset Stretching vs. Traditional Strength Training: Effects on Muscle Strength and Size in Untrained Individuals
Abstract
This study compared the effects of 8 weeks of traditional strength training (TST) and inter-set stretching (ISS) combined with TST on muscular adaptations. Twenty-nine sedentary, healthy adults were randomly assigned to either the TST (n=17; 28.0±6.4 years) or ISS (n=12; 26.8±6.1 years) group. Both groups performed six strength exercises encompassing the whole body (bench press, elbow extension, seated rows, biceps curl, knee extension and knee flexion) performing 4 sets of 8 to 12 repetitions maximum with 90-seconds rest between sets. However, the ISS group performed static passive stretching, at maximum amplitude, for 30 seconds between sets. Both groups performed training sessions twice a week on nonconsecutive days. Muscle strength (i.e. one repetition maximum or 1RM) and hypertrophy (i.e. muscle thickness [MT] via ultrasonography) were measured at pre-test and after 8-wks of training. Both groups increased 1RM bench-press (p≤0.0001): ISS (23.4%, CIdiff: 4.3kg to 11.1kg) and TST (22.2%, CIdiff: 5.2kg to 10.9kg) and 1RM knee extension (p≤0.0001): ISS (25.5%, CIdiff: 5.6kg to 15.0kg) and TST (20.6%, CIdiff: 4.4kg to 12.3kg). Both groups increased biceps brachii (BIMT), triceps brachii (TRMT) and rectus femoris (RFMT) Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation
... However, it is important to note that this was a conference presentation and never published in a peerreviewed journal. The only published study on ISS and hypertrophy by Evangelista et al. 2019 found that an inclusion of a static stretch in the inter-set rest period increased select muscle thickness sites untrained individuals [10]. Nonetheless, considering that untrained cannot be applied to trained populations. ...
... Regarding strength adaptations, previous literature on maximum strength performance with the addition of ISS is sparse. While adding static stretching to dynamic RT has shown to acutely decreases performance parameters, chronically it seems to provide similar or even greater strength adaptations [10,15,16]. Evangelista et al. 2019 were the only group to combine stretching in the inter-set rest period. ...
... Evangelista et al. 2019 were the only group to combine stretching in the inter-set rest period. They reported similar adaptations for 1RM between ISS and traditional RT [TR] in untrained individuals using a static stretch after 16 training sessions [10]. Similarly, while strength endurance is acutely negatively impacted by ISS [17,18], ence with ISS compared to TR on an 8RM test for 6 exercises coverto scrutinize the similar strength adaptations induced by ISS in chronic studies due to the lack of empirical evidence. ...
The study examined the effects of adding a loaded stretch in the inter- set rest period (ISS) compared to traditional resistance training (TR) on muscular adaptations in resistance-trained males. Twenty-six subjects were randomly assigned into two groups (ISS: n=12; TR: n=14) and underwent an 8-week training regimen. Subjects in ISS underwent an additional loaded stretch for 30s at 15% of their working load from the prior set during the inter-set rest periods. Muscle thickness of the Pectoralis Major at the belly (BMT) and lateral (LMT) portions, 1RM and repetitions-to-failure (RTF) on the bench press exercise were measured at baseline and post 8-weeks of training. Additionally, volume load and perceptual parameters for exertion and recovery were measured. Both groups had similar total volume load and average perceptual parameters (p>0.05). There was a main time effect (p < 0.01) for all but one dependent variable indicating that both groups responded similarly across time [(∆BMT: ISS=2.7±1.7 mm; TR=3.0±2.2 mm), (∆LMT: ISS=3.2±1.6 mm; TR=2.8±1.7 mm, (∆1RM: ISS=6.6±3.8 kg; TR=7.5±5.7 kg;). Repetitions-to-failure did not change in either group (∆RTF: ISS=0.0±2.1 repetitions; TR=0.0±2.3 repetitions, p>0.05). Our results suggest that addition of a loaded ISS does not affect muscular adaptations either positively or negatively in resistance-trained males.
... In this sense, two recent studies investigated the effects of performing SS during the RT inter-set rest period [15,16]. One found a significant increase in the muscle thickness of the vastus lateralis, but with no additional effect on hypertrophy of rectus femoris and upper-limb muscles, and strength performance [16], while the other noticed benefits for strength and flexibility [15]. ...
... In this sense, two recent studies investigated the effects of performing SS during the RT inter-set rest period [15,16]. One found a significant increase in the muscle thickness of the vastus lateralis, but with no additional effect on hypertrophy of rectus femoris and upper-limb muscles, and strength performance [16], while the other noticed benefits for strength and flexibility [15]. Notably, there is no consensus on the effects of the combination of RT and SS interventions, with potential benefits for adding SS during the RT inter-set rest period [9,15,16], however, further studies are required [8]. ...
... One found a significant increase in the muscle thickness of the vastus lateralis, but with no additional effect on hypertrophy of rectus femoris and upper-limb muscles, and strength performance [16], while the other noticed benefits for strength and flexibility [15]. Notably, there is no consensus on the effects of the combination of RT and SS interventions, with potential benefits for adding SS during the RT inter-set rest period [9,15,16], however, further studies are required [8]. In addition, it has been observed that the changes in muscle hypertrophy occur in a heterogeneous way along the muscle length after both RT [17], and SS training programs [18]. ...
Performing static stretching (SS) during resistance training (RT) rest periods is posited to potentiate muscular adaptations, but the literature is scarce on the topic. Thus, the purpose of this study was to investigate the effects of adding inter-set SS to a lower-limb flywheel RT program on joint flexibility, muscular strength, and regional hypertrophy. Sixteen untrained male adults (21 ± 1 y) completed the study, where they performed progressive flywheel bilateral squatting twice a week for 5 weeks. One leg of each participant was randomly allocated to perform SS during the inter-set rest period (RT+SS), while the other leg served as control (RT only). Before and after the intervention, knee flexion range of motion; knee extension isometric, concentric, and eccentric peak torque; 1-repetition maximum; and muscle thickness of the lower-limb muscles were assessed. Following the training period, additional effects were observed for the inter-set SS side on increasing joint flexibility (p<0.05), whereas the average increase in strength measures was 5.3% for the control side, and 10.1% for the inter-set SS side, however, SS intervention induced significantly greater gains only for knee extension isometric strength, but not for dynamic 1-RM, concentric, and eccentric tests. Hamstrings and gluteus maximus did not hypertrophy with training; increases quadriceps muscle thickness depended on the site/portion analyzed, but no significant difference was observed between legs (average: RT=7.3%, RT+SS=8.0%). The results indicate that adding inter-set SS to RT may provide large gains in flexibility, slightly benefits for muscular strength (especially for isometric action), but do not impact muscle hypertrophy in untrained young men.
... These measurements were subsequently equated to obtain the body mass index (BMI) in kg.m −2 . Muscle thickness and body fat percentage measurements were performed using BodyMetrix Pro (IntelaMetrix Inc., Livermore, CA, USA), following the recommendations suggested by Evangelista et al. [29]. Fat percentage was automatically calculated from Body View Professional software (IntelaMetrix Inc., Livermore, CA, USA) [30]. ...
... Our findings also showed that IPC significantly increased repetition performance on the 30STS test when compared to the SHAM and CON protocols. The 30STS is a commonly used test to assess lower limb strength in elderly people [29,40]. In addition, the 30STS test is associated with levels of dynamic balance and cardiorespiratory endurance, and therefore represents the functional capacity of the elderly [40]. ...
Background:
Aging decreases some capacities in older adults, sarcopenia being one of the common processes that occur and that interfered with strength capacity. The present study aimed to verify the acute effect of IPC on isometric handgrip strength and functional capacity in active elderly women.
Methods:
In a single-blind, placebo-controlled design, 16 active elderly women (68.1 ± 7.6 years) were randomly performed on three separate occasions a series of tests: (1) alone (control, CON); (2) after IPC (3 cycles of 5-min compression/5-min reperfusion at 15 mmHg above systolic blood pressure, IPC); and (3) after placebo compressions (SHAM). Testing included a handgrip isometric strength test (HIST) and three functional tests (FT): 30 s sit and stand up from a chair (30STS), get up and go time (TUG), and 6 min walk distance test (6MWT).
Results:
HIST significantly increased in IPC (29.3 ± 6.9 kgf) compared to CON (27.3 ± 7.1 kgf; 7.1% difference; p = 0.01), but not in SHAM (27.7 ± 7.9; 5.5%; p = 0.16). The 30STS increased in IPC (20.1 ± 4.1 repetitions) compared to SHAM (18.5 ± 3.5 repetitions; 8.7%; p = 0.01) and CON (18.5 ± 3.9 repetitions; 8.6%; p = 0.01). TUG was significantly lower in IPC (5.70 ± 1.35 s) compared to SHAM (6.14 ± 1.37 s; -7.2%; p = 0.01), but not CON (5.91 ± 1.45 s; -3.7%; p = 0.24). The 6MWT significantly increased in IPC (611.5 ± 93.8 m) compared to CON (546.1 ± 80.5 m; 12%; p = 0.02), but not in SHAM (598.7 ± 67.6 m; 2.1%; p = 0.85).
Conclusions:
These data suggest that IPC can promote acute improvements in handgrip strength and functional capacity in active elderly women.
... In an effort to provide additional insights on the topic, several studies have endeavoured to determine how stretch training impacts hypertrophy in conjunction with regimented resistance training (Evangelista et al., 2019;Ferreira-Júnior et al., 2019;Kubo, Kanehisa, & Fukunaga, 2002b;Moriggi Junior, Berton, Souza, Chacon-Mikahil, & Cavaglieri, 2017;Silva et al., 2014; Table 3). For example, Moriggi Junior et al. ...
... Evangelista et al.(2019) recently compared the effects of an 8-week traditional whole body resistance training programme (6 exercises, 4 × 8-12 repetitions, 2 sessions/week) to the same protocol employing interset-stretch training (30 s of passive stretching during each 90 s interset-rest period) on muscular adaptations in men without experience on resistance training. Results showed that MT increased similarly between conditions for the biceps brachii, triceps brachii and rectus femoris.Alternatively, significantly greater increases in vastus lateralis MT were observed favouring the interset-stretch training group.Notably, both studies that showed an hypertrophic effect employed stretching in the interset-rest period(Evangelista et al., 2019;Silva et al., 2014), while those that did not observe a positive effect involved performing stretching immediately before resistance exer-cise (Ferreira-Júnior et al., 2019; Moriggi Junior et al., 2017) or away from the resistance training session time period ...
Stretch training is widely used in a variety of fitness-related capacities such as increasing joint range of motion, preventing contractures, and alleviating injuries. Moreover, some researches indicate that stretch training may induce muscle hypertrophy; however, studies on the topic have been primarily relegated to animal and in vitro models. The purpose of this brief review was to evaluate whether stretch training is a viable strategy to induce muscle hypertrophy in humans. An extensive literature search was performed using PubMed/MEDLINE, SciELO, and Scopus databases, using terms related to stretching and muscle hypertrophy. Only human trials that evaluated changes in measures of muscle size or architecture following training protocols that it was performed stretching exercises were selected for inclusion. Of the 10 studies identified, 3 observed some significantly positive effects of stretch training on muscle structure. Intriguingly, in these studies, the stretching was carried out with an apparatus that aided in its performance, or with an external overload. In all studies the subjects performed stretching at their own self-determined range-of-motion, no effect was observed. Of the 5 available studies that integrated stretching into a resistance-training program, 2 applied the stretching in the interset-rest period and were the ones that showed enhanced muscle growth. In conclusion, passive, low-intensity stretch does not appear to confer beneficial changes in muscle size and architecture; alternatively, albeit limited evidence suggests that when stretching is done with a certain degree of tensile strain (particularly when loaded, or added between active muscle contractions) may elicit muscle hypertrophy.
... The practice of RT can improve flexibility (Potier et al., 2009) especially with the inclusion of stretching exercises (Junior et al., 2017); however, there is limited evidence regarding the use of stretching during RT. Several studies have investigated the acute and chronic responses of agonist muscle stretching on strength, flexibility, hypertrophy, total training volume (TTV), and metabolic stress (Souza et al., 2013;Junior et al., 2017;Evangelista et al., 2019;Marin et al., 2019). Miranda et al. (2015) evaluated the effect of antagonist (pectoralis major) muscle stretching, performed during the interset rest period, on seated row performance in resistance trained men. ...
Background: Bilateral squat exercise is widely used in resistance training (RT) programs to increase lower limb strength and muscle mass, but this exercise does not result in significant hypertrophy of the hamstrings. It has been speculated that stretching between sets with a certain degree of tension results in muscle hypertrophy, while acute stretching could decrease performance during maximal contractions. Objective: This study investigated the acute effects of hamstring stretching before bilateral squatting on muscle thickness (MT), electromyography (EMG), and total training volume (TTV) on exercise performance. Methods: Fourteen resistance-trained young men, with ∼7.5 years of RT experience, performed the 10 repetition maximum (RM) for the barbell squat in two sessions (test–retest) separated by period after 48 h. Participants engaged in two resistance exercise conditions separated by a 1 week recovery interval: one session employed hamstrings stretching and the other did not include hamstrings stretching. Before and after each resistance exercise session, the thickness of the quadriceps muscles and biceps femoris long head were obtained by ultrasound imaging. Moreover, the EMG amplitudes for the quadriceps muscles, biceps femoris, and iliocostalis muscles were recorded during back squat performance. The TTV was also evaluated for each exercise session. Results: A significant increase in MT was observed after every set in both conditions for the evaluated quadriceps muscles (all p < 0.05), while for the biceps femoris, this effect was found only in the stretching condition (p < 0.05). EMG activity increased in the rectus femoris, vastus lateralis, and vastus medialis for the stretching condition. For the non-stretching condition, activity only increased in the vastus lateralis and medialis. There was no difference in EMG activity for the biceps femoris and iliocostalis in both conditions. Conclusion: Stretching the hamstrings immediately before each set of the back squat can be used to acutely increase biceps femoris thickness without impairing squat performance.
Treatment strategies and training regimens, which induce longitudinal muscle growth and increase the muscles’ length range of active force exertion, are important to improve muscle function and to reduce muscle strain injuries in clinical populations and in athletes with limited muscle extensibility. Animal studies have shown several specific loading strategies resulting in longitudinal muscle fiber growth by addition of sarcomeres in series. Currently, such strategies are also applied to humans in order to induce similar adaptations. However, there is no clear scientific evidence that specific strategies result in longitudinal growth of human muscles. Therefore, the question remains what triggers longitudinal muscle growth in humans. The aim of this review was to identify strategies that induce longitudinal human muscle growth. For this purpose, literature was reviewed and summarized with regard to the following topics: (1) Key determinants of typical muscle length and the length range of active force exertion; (2) Information on typical muscle growth and the effects of mechanical loading on growth and adaptation of muscle and tendinous tissues in healthy animals and humans; (3) The current knowledge and research gaps on the regulation of longitudinal muscle growth; and (4) Potential strategies to induce longitudinal muscle growth. The following potential strategies and important aspects that may positively affect longitudinal muscle growth were deduced: (1) Muscle length at which the loading is performed seems to be decisive, i.e., greater elongations after active or passive mechanical loading at long muscle length are expected; (2) Concentric, isometric and eccentric exercises may induce longitudinal muscle growth by stimulating different muscular adaptations (i.e., increases in fiber cross-sectional area and/or fiber length). Mechanical loading intensity also plays an important role. All three training strategies may increase tendon stiffness, but whether and how these changes may influence muscle growth remains to be elucidated. (3) The approach to combine stretching with activation seems promising (e.g., static stretching and electrical stimulation, loaded inter-set stretching) and warrants further research. Finally, our work shows the need for detailed investigation of the mechanisms of growth of pennate muscles, as those may longitudinally grow by both trophy and addition of sarcomeres in series.
Objective: To analyze the effects of whole body electrostimulation (WB-EMS) with body weight training on functional fitness and body composition of older men.
Methods: Twenty physically inactive older men were randomized into: Control group (control), performed the body weight exercise training wearing electrostimulation clothing, but without receiving electrical current stimuli ( n = 10), and body weight associated with whole body electrostimulation group (BW+WB-EMS), performed the body weight exercise training wearing electrostimulation clothing plus whole body electrostimulation ( n = 10). The training sessions were performed twice a week for 6 weeks and included eight exercises using body weight, performed in two sets of eight repetitions. Physical function was assessed using a battery composed of seven tests, six derived from the Senior fitness test and a handgrip strength test. We also measured the muscle thickness (MT) of the biceps and triceps brachii and vastus lateralis.
Results: The BW+WB-EMS group presented increased ( p < 0.05) performance in the 30-s chair stand test (10.2 ± 3.3 vs. 13.8 ± 5.0 reps), arm curl (16.6 ± 3.9 vs. 19.9 ± 6.1 reps), 6-min walk test (402 ± 96 vs. 500 ± 104 m), and handgrip strength test (30 ± 11 vs. 32 ± 11 kgf). The BW+WB-EMS group also presented increased MT ( p < 0.05) in the biceps brachii (17.7 ± 3.0 vs. 21.4 ± 3.4 mm), triceps brachial (14.7 ± 3.6 vs. 17.5 ± 4.1 mm), and vastus lateralis muscles (15.1 ± 2.6 vs. 18.6 ± 4.3 mm). Moderate correlations were found in arm curl ( p = 0.011, r = 0.552) but not handgrip strength ( p = 0.053, r = 0.439) with changes in the biceps MT. Moderate changes in the 6-min walk distance were significantly correlated with changes in vastus lateralis MT ( p = 0.036, r = 0.471). There was a moderate correlation between the changes in the 30-s chair stand test ( p = 0.006, r = 0.589) and changes in the vastus lateralis MT. Furthermore, although a moderate correlation ( r = 0.438) was found between triceps MT and handgrip strength no significant difference ( p = 0.053) was reported. Additionally, there were no statistical differences in any parameters for the control group.
Conclusion: WB-EMS with body weight training increased functional fitness, MT, and lean mass, and decreased body fat in physically inactive older men.
Introduction
There are few studies on the effectiveness of training models with high volume sets per session in particular muscle groups.
Objective
The aim of the study was to investigate the effects of different resistance training (RT) repetitions with equalized volumes on muscle adaptations.
Methods
This study used an experimental design in which forty-seven volunteers underwent 8 weeks of RT after having been distributed randomly into three groups: ten sets of three maximum repetitions (10x3), three sets of ten maximum repetitions (3x10) and five sets of six maximum repetitions (5x6) for each muscular group per training session. Maximum strength (1RM test) and muscle thickness (MT) were evaluated as outcomes.
Results
A significant main effect (p=0.001) of time on maximum strength was observed for the three groups, but no significance was observed (p>0.05) in time x group interactions. A significant main effect (p=0.001) of time was observed on MT for biceps, triceps and vastus lateralis, without significant differences for time x group interactions. Significant correlations were found between maximum strength and muscle thickness after general statistical analyses for all protocols.
Conclusion
Improvements in maximum strength and muscle thickness are similar when repetition volumes are equalized through the number of series and repetitions. Level of evidence I; Therapeutic studies, investigation of treatment results.
This study investigated the acute effects of inter-set static stretching (ISS) during resistance exercise (RE) on the subsequent neuromuscular and metabolic responses. Twelve resistance-trained men performed three different knee extension RE protocols comprised of seven sets of 10 repetitions in a counterbalanced fashion. The three protocols were: 1) ISS (subjects performed 25 sec of quadriceps stretching between sets during 40 sec rest interval); 2) control (CON, subject passively rested between sets for 40 sec); 3) traditional (TRA, subject passively rested between sets for 120 sec). Total work was lower (p < 0.05) in ISS than CON and TRA (p <0.05). The fatigue index was greater (p < 0.05) in ISS compared with CON and TRA. ISS also resulted in lower (p < 0.05) electromyography (EMG) amplitude during the 6th and 7th sets compared with TRA. Additionally, EMG frequency was lower (p < 0.05) from the 3rd to 5th sets during ISS compared to CON, and from the 3rd to 7th sets compared to TRA. Muscle swelling and blood lactate similarly increased (p > 0.05) in response to all protocols. These results indicate that ISS negatively impacts neuromuscular performance, and does not increase the metabolic stress compared to passive rest intervals.
This investigation compared the effect of high-volume (VOL) versus high-intensity (INT) resistance training on stimulating changes in muscle size and strength in resistance-trained men. Following a 2-week preparatory phase, participants were randomly assigned to either a high-volume (VOL; n = 14, 4 × 10-12 repetitions with ~70% of one repetition maximum [1RM], 1-min rest intervals) or a high-intensity (INT; n = 15, 4 × 3-5 repetitions with ~90% of 1RM, 3-min rest intervals) training group for 8 weeks. Pre- and posttraining assessments included lean tissue mass via dual energy x-ray absorptiometry, muscle cross-sectional area and thickness of the vastus lateralis (VL), rectus femoris (RF), pectoralis major, and triceps brachii muscles via ultrasound images, and 1RM strength in the back squat and bench press (BP) exercises. Blood samples were collected at baseline, immediately post, 30 min post, and 60 min postexercise at week 3 (WK3) and week 10 (WK10) to assess the serum testosterone, growth hormone (GH), insulin-like growth factor-1 (IGF1), cortisol, and insulin concentrations. Compared to VOL, greater improvements (P < 0.05) in lean arm mass (5.2 ± 2.9% vs. 2.2 ± 5.6%) and 1RM BP (14.8 ± 9.7% vs. 6.9 ± 9.0%) were observed for INT. Compared to INT, area under the curve analysis revealed greater (P < 0.05) GH and cortisol responses for VOL at WK3 and cortisol only at WK10. Compared to WK3, the GH and cortisol responses were attenuated (P < 0.05) for VOL at WK10, while the IGF1 response was reduced (P < 0.05) for INT. It appears that high-intensity resistance training stimulates greater improvements in some measures of strength and hypertrophy in resistance-trained men during a short-term training period.
© 2015 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society.
The purpose of this study was to investigate the time course of hypertrophic adaptations in both the upper arm and trunk muscles following high-intensity bench press training. Seven previously untrained young men (aged 25 ± 3 years) performed free-weight bench press training 3 days (Monday, Wednesday and Friday) per week for 24 weeks. Training intensity and volume were set at 75% of one repetition maximum (1-RM) and 30 repetitions (3 sets of 10 repetitions, with 2-3 min of rest between sets), respectively. Muscle thickness (MTH) was measured using B-mode ultrasound at three sites: the biceps and triceps brachii and the pectoralis major. Measurements were taken a week prior to the start of training, before the training session on every Monday and 3 days after the final training session. Pairwise comparisons from baseline revealed that pectoralis major MTH significantly increased after week-1 (p = 0.002), triceps MTH increased after week-5 (p = 0.001) and 1-RM strength increased after week-3 (p = 0.001) while no changes were observed in the biceps MTH from baseline. Significant muscle hypertrophy was observed earlier in the chest compared to that of the triceps. Our results indicate that the time course of the muscle hypertrophic response differs between the upper arm and chest.
Adequate levels of strength and flexibility are important for the promotion and maintenance of health and functional autonomy as well as safe and effective sports participation. The aim of the present study was to analyze the effects of 8 weeks of strength training with or without inter-set static stretching on strength, flexibility and hormonal adaptations of trained men. Sixteen trained men were randomly divided into 2 groups: the static stretching group (SSG) and passive interval group (PIG). All participants performed 24 training sessions 3 times a week. The test and retest of 8RM, strength, flexibility, cortisol and growth hormone concentration in pre and post test conditions were also evaluated. To compare the differences between and within groups in pre- and post-training tests, ANOVA with repeated measures was performed (SSGpre x SSGpost; PIGpre x PIGpost; SSGpost x PIGpost). An alpha level of p<0.05 was considered statistically significant for all comparisons. Both groups showed significant increases in strength (SSGpre vs. SSGpost; PIGpre vs. PIGpost) in the same exercises for leg extension (LE) and Low Row (LR). Specifically, in the SSG group, the parameters for LE were (p = 0.0015 and ES = 2.28 - Large), and the parameters for LR were (p = 0.002 and ES = 1.95 - Large). Moreover, in the PIG group, the parameters for LE were (p = 0.009 and ES = 1.95 - Large), and the parameters for LR were (p = 0.0001 and ES = 2.88 - Large). No differences were found between the groups (SSGpost vs. PIGpost). Both groups showed significant increases in flexibility but in different joints (SSGpre vs. SSGpost; PIGpre vs. PIGpost). In the SSG group, only three joints showed significant increases in flexibility: shoulder extension (p = 0.004 and ES = 1.76 - Large), torso flexion (p = 0.002 and ES = 2.36 - Large), and hip flexion (p = 0.001 and ES = 1.79 -Large). In the PIG group, only three joints showed increases in flexibility: horizontal shoulder abduction (p = 0.003 and ES = 2.07 - Large), hip flexion (p = 0.001 and ES = 2.39 - Large), and hip extension (p = 0.02 and ES = 1.79 - Large). In-between group analyses (SSGpost x PIGpost) revealed differences in two joints: shoulder extension (p = 0.001) and horizontal shoulder abduction (p = 0.001). Hormonal profiles showed no significant differences in cortisol secretion or growth hormone concentration. In conclusion, both studied strength protocols (with and without inter-set static stretching) resulted in flexibility and strength gains without an effect on the anabolic and catabolic hormonal profile.
The relative merits of the separate and combined uses of stretch and electrical stimulation at 10 Hz in influencing the rates of protein synthesis in vivo, proteolysis, and the growth of the extensor digitorum longus muscle have been investigated after 3 days in the rabbit. Continuous electrical stimulation failed to change muscle protein turnover or growth. Static stretch caused significant adaptive growth, with increases in c-fos, c-jun, and insulin-like growth factor I (IGF-I; 12-fold) mRNA levels, and protein (19%), RNA (128%), and DNA (45%) contents. Both the fractional (138%) and total (191%) rates of protein synthesis increased with stretch, correlating with increased ribosomal capacities. Combining stretch and electrical stimulation increased the mRNA concentration of IGF-I (40-fold). The adaptive growth was greater (35%), with massive increases in the nucleic acids (185 and 300%), ribosomal capacities (230%), and the rates of protein synthesis (345 and 450%). Large increases (i.e., 200-400%) in cathepsins B and L and dipeptidyl aminopeptidase I activities during stretch, with or without stimulation, suggest a role for these enzymes in tissue remodeling during muscle hypertrophy.
We examined the effect of an isolated bout of maximal tolerated passive stretch on fractional muscle protein synthetic rate in human soleus muscle. Eight healthy males performed two separate trials with the same leg: one session of passive stretch and one of intermittent active isometric contraction at a force equivalent to that which occurred during the passive stretch trial. This force was approximately 40% of maximum voluntary contraction force and produced volitional fatigue in approximately 27 min. Intermittent passive stretch, for the same duration, elicited a 6.1 degrees increase in joint angle (P<.0005) with silent electromyography. Fractional protein synthetic rate from experimental and control soleus in each trial was assessed from biopsy samples over the period 10-22 hr postexercise by the incorporation rate of L-[1-13C] leucine into muscle. Protein synthesis was elevated in the soleus of the exercised leg following the active contraction trial by 49% (P<.05) but not following the passive stretch trial. Results indicate that a single bout of maximal passive stretch does not significantly elevate fractional muscle protein synthetic rate in humans and thus suggests that muscle stretch per se is not the stimulus for the muscle hypertrophy that occurs with resistance training.
To determine the effectiveness of a muscle strengthening program compared to a stretching program in women with fibromyalgia (FM).
Sixty-eight women with FM were randomly assigned to a 12 week, twice weekly exercise program consisting of either muscle strengthening or stretching. Outcome measures included muscle strength (main outcome variable), flexibility, weight, body fat, tender point count, and disease and symptom severity scales.
No statistically significant differences between groups were found on independent t tests. Paired t tests revealed twice the number of significant improvements in the strengthening group compared to the stretching group. Effect size scores indicated that the magnitude of change was generally greater in the strengthening group than the stretching group.
Patients with FM can engage in a specially tailored muscle strengthening program and experience an improvement in overall disease activity, without a significant exercise induced flare in pain. Flexibility training alone also results in overall improvements, albeit of a lesser degree.
The aim of the present study was to determine the effect of stretching applied every 3 days to the soleus muscle immobilized in the shortened position on muscle fiber morphology. Eighteen 16-week-old Wistar rats were used and divided into three groups of 6 animals each: a) the left soleus muscle was immobilized in the shortened position for 3 weeks; b) during immobilization, the soleus was stretched for 40 min every 3 days; c) the non-immobilized soleus was only stretched. Left and right soleus muscles were examined. One portion of the soleus was frozen for histology and muscle fiber area evaluation, while the other portion was used to identify the number and length of serial sarcomeres. Immobilized muscles (group A) showed a significant decrease in weight (44 +/- 6%), length (19 +/- 7%), serial sarcomere number (23 +/- 15%), and fiber area (37 +/- 31%) compared to the contralateral muscles (P < 0.05, paired Student t-test). The immobilized and stretched soleus (group B) showed a similar reduction but milder muscle fiber atrophy compared to the only immobilized group (22 +/- 40 vs 37 +/- 31%, respectively; P < 0.001, ANOVA test). Muscles submitted only to stretching (group C) significantly increased the length (5 +/- 2%), serial sarcomere number (4 +/- 4%), and fiber area (16 +/- 44%) compared to the contralateral muscles (P < 0.05, paired Student t-test). In conclusion, stretching applied every 3 days to immobilized muscles did not prevent the muscle shortening, but reduced muscle atrophy. Stretching sessions induced hypertrophic effects in the control muscles. These results support the use of muscle stretching in sports and rehabilitation.
Akt/protein kinase B is a serine/threonine kinase that has emerged as a critical signaling component for mediating numerous cellular responses. Contractile activity has recently been demonstrated to stimulate Akt signaling in skeletal muscle. Whether physiological exercise in vivo activates Akt is controversial, and the initiating factors that result in the stimulation of Akt during contractile activity are unknown. In the current study, we demonstrate that treadmill running exercise of rats using two different protocols (intermediate high or high-intensity exhaustive exercise) significantly increases Akt activity and phosphorylation in skeletal muscle composed of various fiber types. To determine if Akt activation during contractile activity is triggered by mechanical forces applied to the skeletal muscle, isolated skeletal muscles were incubated and passively stretched. Passive stretch for 10 min significantly increased Akt activity (2-fold) in the fast-twitch extensor digitorum longus (EDL) muscle. However, stretch had no effect on Akt in the slow-twitch soleus muscle, although there was a robust phosphorylation of the stress-activated protein kinase p38. Similar to contraction, stretch-induced Akt activation in the EDL was fully inhibited in the presence of the phosphatidylinositol 3-kinase inhibitor wortmannin, whereas glycogen synthase kinase-3 (GSK3) phosphorylation was only partially inhibited. Stretch did not cause dephosphorylation of glycogen synthase on GSK3-targeted sites in the absence or presence of wortmannin. We conclude that physiological exercise in vivo activates Akt in multiple skeletal muscle fiber types and that mechanical tension may be a part of the mechanism by which contraction activates Akt in fast-twitch muscles.
This study compared adaptations in fascicle lengths, pennation angles, and muscle thickness of the lateral and medial gastrocnemii in response to 6 weeks of stretch training. The nondominant plantar flexors of 11 males were stretched five times per week for 6 weeks and compared with the contralateral leg and a nonstretched control group of 10 males. During stretch training, instantaneous electromyography was utilized to ensure passive muscle stretch. At baseline, week three, week six and 1 week after the conclusion of stretch training, ultrasound was used to measure fascicle lengths, pennation angles, muscle thickness of the lateral gastrocnemius and medial gastrocnemius, and Achilles tendon thickness and length. Plantar flexion torque was measured, and voluntary activation was assessed. Muscle thickness increased 5.6% after 6 weeks of stretch training (P=.009). The fascicles in the lateral gastrocnemius lengthened to a greater extent than the medial. Overall, fascicles lengthened 25% (P<.001) in the muscle tendon junction and 5.1% (P<.001) in the muscle belly. Pennation angles were unchanged in the medial gastrocnemius but decreased in the lateral gastrocnemius 7.1% (P=.02). There was no change in maximal voluntary contraction, voluntary activation, tendon length, or thickness. This study demonstrates that stretch training is a viable modality to alter muscle architecture of the human gastrocnemius through lengthening of muscle fascicles, decreasing pennation angles, and increasing muscle thickness, albeit adaptations are unequal between the lateral and medial heads.
Purpose:
This randomized controlled trial compared the effects of resistance training (RT) and RT with instability (RTI) on the timed up and go test (TUG), on-medication Unified Parkinson's Disease Rating Scale motor subscale score (UPDRS-III), Montreal Cognitive Assessment (MoCA) score, Parkinson's Disease Questionnaire (PDQ-39) score, and muscle strength in the leg-press exercise (one repetition maximum [1RM]) of patients with Parkinson's disease (PD).
Methods:
Thirty-nine patients with moderate to severe PD were randomly assigned to a non-exercising control group (C), RT group, and RTI group. The RT and RTI groups performed progressive resistance training twice a week for 12 weeks. However, only the RTI group used high motor complexity exercises (i.e., progressive resistance training with unstable devices), for example, half-squat exercise on the BOSU® device. The primary outcome was mobility (TUG). Secondary outcomes were on-medication motor signs (UPDRS-III), cognitive impairment (MoCA), quality of life (PDQ-39), and muscle strength (1RM).
Results:
There were no differences between RTI and RT groups for any of the outcomes at post-training (P>0.05). However, there were differences between RTI and C groups in the TUG, MoCa, and muscle strength values at post-training (P<0.05). Only the RTI group improved the TUG (-1.9 seconds), UPDRS-III score (-4.5 score), MoCA score (6.0 score), and PDQ-39 score (-5.2 score) from pre to post-training (P<0.001). Muscle strength improved for both training groups (P<0.001). No adverse events were reported during the trial.
Conclusions:
Both training protocols improved muscle strength, but only RTI improved the mobility, motor signs, cognitive impairment, and quality of life, likely due to the usage of high motor complexity exercises. Thus, RTI may be recommended as an innovative adjunct therapeutic intervention for patients with PD.
The aim of this study was to investigate the acute effects of static and dynamic stretching on explosive power, flexibility and sprinting ability of adolescent boys and girls and report possible gender interactions. Forty-seven active adolescent boys and girls were randomly tested following static and dynamic stretching of 40 s on quadriceps, hamstrings, hip extensors and plantar flexors; no stretching was performed at the control condition. Pre- and post-treatment tests examined the effects of stretching on 20 m sprint run (20 m), countermovement jump height (CMJ) and sit and reach flexibility test (SR). In terms of performance static stretching hindered 20 m and CMJ in boys and girls by 2.5% and 6.3% respectively. Dynamic stretching had no effect on 20m in boys and girls but impaired CMJ by 2.2%. In terms of flexibility both static and dynamic stretching improved performance with static stretching being more beneficial (12.1%) compared to dynamic (6.5%). No gender interaction was found. It can therefore be concluded that static stretching significantly negates sprinting performance and explosive power in adolescent boys and girls, whereas dynamic stretching deteriorates explosive power and has no effect on sprinting performance. This diversity of effects denotes that the mode of stretching used in adolescent boys and girls should be task specific.
THE TIME THAT A MUSCLE IS UNDER TENSION DURING RESISTANCE STRENGTH TRAINING IS THOUGHT IMPORTANT IN MAXIMIZING THE HYPERTROPHIC RESPONSE OF SKELETAL MUSCLE. IMPLEMENTING STRETCHING IN BETWEEN SETS MAY INCREASE THE HYPERTROPHIC EFFECT BY ADDING TO TOTAL SESSION TIME UNDER TENSION AND AS SUCH INCREASE THE EFFECT OF VARIOUS NEUROMECHANICAL AND METABOLIC STIMULI THAT ARE THOUGHT IMPORTANT TO HYPERTROPHIC ADAPTATION. THIS REVIEW WILL EXPLORE THIS CONTENTION BY BRIEFLY DISCUSSING THEMES AROUND STRETCH AND RESTRICTED BLOOD FLOW, HORMONE RELEASE, SIGNALING PATHWAYS, STRETCH ACTIVATION CHANNELS, STRETCH-INDUCED HYPERTROPHY, AND STRENGTH AND POWER PERFORMANCE.
We applied a meta-analytical approach to derive a robust estimate of the acute effects of pre-exercise static stretching (SS) on strength, power, and explosive muscular performance. A computerized search of articles published between 1966 and December 2010 was performed using PubMed, SCOPUS, and Web of Science databases. A total of 104 studies yielding 61 data points for strength, 12 data points for power, and 57 data points for explosive performance met our inclusion criteria. The pooled estimate of the acute effects of SS on strength, power, and explosive performance, expressed in standardized units as well as in percentages, were -0.10 [95% confidence interval (CI): -0.15 to -0.04], -0.04 (95% CI: -0.16 to 0.08), and -0.03 (95% CI: -0.07 to 0.01), or -5.4% (95% CI: -6.6% to -4.2%), -1.9% (95% CI: -4.0% to 0.2%), and -2.0% (95% CI: -2.8% to -1.3%). These effects were not related to subject's age, gender, or fitness level; however, they were more pronounced in isometric vs dynamic tests, and were related to the total duration of stretch, with the smallest negative acute effects being observed with stretch duration of ≤45 s. We conclude that the usage of SS as the sole activity during warm-up routine should generally be avoided.
Static stretch is commonly used to prevent contracture and to improve joint mobility. However, it is unclear whether the components of the muscle-tendon unit are affected by a static stretch training program. This study investigated the effect of a four-week static stretch training program on the viscoelastic properties of the muscle-tendon unit and muscle. The subjects comprised 18 male participants (mean age 21.4 ± 1.7 years). The range of motion (ROM), passive torque, myotendinous junction (MTJ) displacement and, muscle fascicle length of the gastrocnemius muscle were assessed using both ultrasonography and a dynamometer while the ankle was passively dorsiflexed. After the initial test, the participants were assigned either to a group that stretched for 4 weeks (N = 9) or to a control group (N = 9). The tests were repeated after the static stretch training program. The ROM and MTJ displacement significantly increased, and the passive torque at 30° significantly decreased, in the stretching group after the study period. However, there was no significant increase in muscle fascicle length. These results suggest that a 4-week static stretch training program changes the flexibility of the overall MTU without causing concomitant changes in muscle fascicle length.
The purpose of this study was to examine the strength and flexibility gains after isolated or simultaneous strength and flexibility training after 16 weeks. Eighty sedentary women were randomly assigned to 1 of 4 groups: strength training (ST; n = 20), flexibility training (FLEX) (n = 20), combination of both (ST + FLEX; n = 20) and control group (CG; n = 20). All the groups performed pre and posttraining sit and reach test to verify the flexibility level and 10RM test for leg press and bench press exercises. The training protocol for all groups, except for the CG, included 3 weekly sessions, in alternated days, totaling 48 sessions. Strength training was composed of 8 exercises for upper and lower body, executed in 3 sets of periodized training. The flexibility training was composed of static stretching exercises that involved upper and lower body. Results showed that ST (30 ± 2.0 to 36 ± 3.0 cm), ST + FLEX (31 ± 1.0 to 42 ± 4.0 cm), and FLEX (32 ± 3.0 to 43 ± 2.0 cm) significantly increased in flexibility in relation to baseline and to CG (30 ± 2.0 to 30 ± 2.0 cm); however, no significant differences were observed between the treatment conditions. Strength tests demonstrated that ST and ST + FLEX significantly increased 10RM when compared to baseline, FLEX, and the CG. In conclusion, short-term strength training increases flexibility and strength in sedentary adult women. Strength training may contribute to the development and maintenance of flexibility even without the inclusion of additional stretching, but strength and flexibility can be prescribed together to get optimal improvements in flexibility.
This study was undertaken to examine the role of interset stretching on the time course of acceleration portion AP and mean velocity profile during the concentric phase of 2 bench-press sets with a submaximal load (60% of the 1 repetition maximum). Twenty-five college students carried out, in 3 different days, 2 consecutive bench-press sets leading to failure, performing between sets static stretching, ballistic stretching, or no stretching. Acceleration portion and lifting velocity patterns of the concentric phase were not altered during the second set, regardless of the stretching treatment performed. However, when velocity was expressed in absolute terms, static stretching reduced significantly (p <0.05) the average lifting velocity during the second set compared to the first one. Therefore, if maintenance of a high absolute velocity over consecutive sets is important for training-related adaptations, static stretching should be avoided or replaced by ballistic stretching.
This study investigated differences in lower-body strength improvements when using standard progressive resistance training (WT) vs. the same progressive resistance training combined with static stretching exercises (WT + ST). Thirty-two college students (16 women and 16 men) were pair matched according to sex and knee extension 1 repetition maximum (1RM). One person from each pair was randomly assigned to WT and the other to WT + ST. WT did 3 sets of 6 repetitions of knee extension, knee flexion, and leg press 3 days per week for 8 weeks with weekly increases in the weight lifted. The WT + ST group performed the same lifting program as the WT group along with static stretching exercises designed to stretch the hip, thigh, and calf muscle groups. Stretching exercise sessions were done twice a week for 30 minutes during the 8-week period. WT significantly (p < 0.05) improved their knee flexion, knee extension, and leg press 1RM by 12, 14, and 9%, respectively. WT + ST, on the other hand, significantly (p < 0.05) improved their knee flexion, knee extension, and leg press 1RM by 16, 27, and 31, respectively. In addition, the WT + ST group had significantly greater knee extension and leg press gains (p < 0.05) than the WT group. Based on results of this study, it is recommended that to maximize strength gains in the early phase of training, novice lifters should include static stretching exercises to their resistance training programs.
Muscle protein synthesis is increased after exercise, but evidence is now accruing that during muscular activity it is suppressed. In life, muscles are subjected to shortening forces due to contraction, but may also be subject to stretching forces during lengthening. It would be biologically inefficient if contraction and stretch have different effects on muscle protein turnover, but little is known about the metabolic effects of stretch. To investigate this, we assessed myofibrillar and sarcoplasmic protein synthesis (MPS, SPS, respectively) by incorporation of [1-13C]proline (using gas chromatography-mass spectrometry) and anabolic signalling (by phospho-immunoblotting and kinase assays) in cultured L6 skeletal muscle cells during 30 min of cyclic stretch and over 30 min intervals for up to 120 min afterwards. SPS was unaffected, whereas MPS was suppressed by 40 +/- 0.03% during stretch, before returning to basal rates by 90-20 min afterwards. Paradoxically, stretch stimulated anabolic signalling with peak values after 2-30 min: e.g. focal adhesion kinase (FAK Tyr576/577; +28 +/- 6%), protein kinase B activity (Akt; +113 +/- 31%), p70S6K1 (ribosomal S6 kinase Thr389; 25 +/- 5%), 4E binding protein 1 (4EBP1 Thr37/46; 14 +/- 3%), eukaryotic elongation factor 2 (eEF2 Thr56; -47 +/- 4%), extracellular regulated protein kinase 1/2 (ERK1/2 Tyr202/204; +65% +/- 9%), eukaryotic initiation factor 2alpha (eIF2alpha Ser51; -20 +/- 5%, P < 0.05) and eukaryotic initiation factor 4E (eIF4E Ser209; +33 +/- 10%, P < 0.05). After stretch, except for Akt activity, stimulatory phosphorylations were sustained: e.g. FAK (+26 +/- 11%) for > or =30 min, eEF2 for > or =60 min (peak -45 +/- 4%), 4EBP1 for > or =90 min (+33 +/- 5%), and p70S6K1 remained elevated throughout (peak +64 +/- 7%). Adenosine monophosphate-activated protein kinase (AMPK) phosphorylation was unchanged throughout. We report for the first time that acute cyclic stretch specifically suppresses MPS, despite increases in activity/phosphorylation of elements thought to increase anabolism.
1. Twenty-five minute daily muscle stretching, perpendicular to the fibre direction of the adductor muscles without movement of the hip, was performed in patients with osteoarthritis of the hip.
2. Before and after treatment hip abduction was measured and muscle biopsies were taken for analysis of fibre cross-sectional areas of type 1 and type 2 fibres as well as adenosine 5′-triphosphate, creatine phosphate and glycogen contents.
3. From the results it is concluded that passive muscle stretching leads to a significant increase in hip abduction of 8.3° (P < 0.05). There was also a significant increase of type 1 and type 2 fibre cross-sectional area and of glycogen content after the treatment period (P < 0.05), but the concentrations of adenosine 5′-triphosphate and creatine phosphate did not change significantly.
In the anterior latissimus dorsi muscle of the chicken hypertrophy was obtained by stretching, whether the muscle was innervated or not. The teres minor muscle, which was stretched at the same time, also hypertrophied; the posterior latissimus dorsi muscle, consisting of red and white fibers, did not change significantly in weight, but its position in the body is such that it was not stretched adequately.The rate of certain histological changes which accompany hypertrophy keeps pace with the rate of the hypertrophy. These changes include enlargement of nuclei, nuclear proliferation, and invasion with subsequent splitting of the units producing fibers of varying diameters. ATPase differentiation of fibers weakens when hypertrophy exceeds 35–40%, producing muscle fibers exhibiting, in general, a homochromatic, light ATPase response. The amount of hypertrophy and hyperplasia is proportional to the degree of stretch.Excluding an increase caused by fibers splitting, fiber counts of complete cross sections of anterior latissimus dorsi muscles taken at intervals after the onset of stretch showed a steady increase in the total number of fibers. This began promptly under extensive stretch, much later under mild stretch. The presence of new fibers appeared to be a function of both time and the amount of hypertrophy; the degree of hypertrophy had to be at least 70%. The increase in total fibers lagged behind the number of small fibers interpreted as “new.” The fate of many of the new fibers is not known but a sufficient number matured in the 8 wk of the experiment to produce the increase in total number.
Skeletal muscle growth induced by passive stretch was characterized in chicken wing muscles. Within 24 h after installing the stretch apparatus on the birds, the sarcomere length of the stretched patagialis was 40% greater than control. This was accompanied by increasing muscle wet weight, protein content, DNA and RNA concentrations. Sarcomere length returned to near control values by 3 days, but muscle wet weight and protein content continued to increase through 10 days. DNA and RNA concentrations reached a peak after 5-7 days and began to decline. Histological examination after 7 days revealed no change in the concentration of nuclei inside the basement membrane surrounding the muscle fibers, but the concentration of nuclei outside the basement membrane had increased. Therefore, the ratio of protein to DNA can be a poor index of muscle fiber DNA unit size. Additionally, no evidence of new muscle fiber formation was found. Electron microscopy demonstrated that passive stretch destroyed sarcomere registration between adjacent myofibrils. We concluded that passive stretch is a powerful inducer of muscle growth.
A new model of stretch-induced growth is evaluated in four chicken wing muscles stretched to different extents by a spring-loaded tubular assembly. Muscles grew in length and cross section in proportion to the extent to which they were stretched. Longitudinal growth was essentially completed within 1 wk, while muscles grew in cross section through at least 5 wk of stretch. The muscles were neither denervated nor immobilized, and muscle activity as measured by EMG was not increased. Oxidative enzyme activities increased substantially with stretch in the patagialis (PAT), a twitch muscle, but were relatively unchanged in the slow-tonic anterior latissimus dorsi (ALD). Stretch altered mitochondrial enzyme proportions in the PAT, but had little effect in the ALD. Capillary density was unchanged with stretch in the PAT, but decreased in the ALD. Capillary density was unchanged with stretch in the PAT, but decreased in the ALD. Capillary-to-fiber ratio, however, increased in both muscles. We conclude that muscles grow and adapt enzymatically due to stretch, but that these responses are dissimilar in twitch and tonic muscles.
Intermittent stretch of the anterior latissimus dorsi (ALD) muscle produces fiber hypertrophy without fiber hyperplasia (J. Appl. Physiol. 74: 1893-1898, 1993). This study was undertaken to determine if a progressive increase in load and duration of stretch would induce extremely large muscle fiber areas or if the fibers would reach a critical size before the onset of fiber hyperplasia. Weights ranging from 10 to 35% of the bird's mass were attached to the right wing of 26 adult quail while the left wing served as the intra-animal control. The stretch protocol was as follows: day 1 (10% wt), days 2 and 3 (rest), day 4 (15% wt), days 5-7 (rest), day 8 (20% wt), days 9 and 10 (rest), days 11-14 (25% wt), days 15 and 16 (rest), and days 17-38 (35% wt). Birds were killed after 12, 16, 20, 24, and 28 days of stretch not including rest days. Muscle mass increased 174% (12 days), 196% (16 days), 225% (20 days), 264% (24 days), and 318% (28 days). Muscle length increased 60% (12 days), 34% (16 days), 59% (20 days), 50% (24 days), and 51% (28 days). Mean fiber area increased 111% (12 days), 142% (16 days), 75% (20 days), 90% (24 days), and 39% (28 days). Fiber number, which was measured histologically, increased significantly by 82% only in the 28 days of stretch group. The percentage of slow tonic fibers did not change for any of the time points examined.(ABSTRACT TRUNCATED AT 250 WORDS)
The present study examined whether resistance and stretching training programmes altered the viscoelastic properties of human tendon structures in vivo. Eight subjects completed 8 weeks (4 days per week) of resistance training which consisted of unilateral plantar flexion at 70 % of one repetition maximum with 10 repetitions per set (5 sets per day). They performed resistance training (RT) on one side and resistance training and static stretching training (RST; 10 min per day, 7 days per week) on the other side. Before and after training, the elongation of the tendon structures in the medial gastrocnemius muscle was directly measured using ultrasonography, while the subjects performed ramp isometric plantar flexion up to the voluntary maximum, followed by a ramp relaxation. The relationship between estimated muscle force (F(m)) and tendon elongation (L) was fitted to a linear regression, the slope of which was defined as stiffness. The hysteresis was calculated as the ratio of the area within the F(m)-L loop to the area beneath the load portion of the curve. The stiffness increased significantly by 18.8 +/- 10.4 % for RT and 15.3 +/- 9.3 % for RST. There was no significant difference in the relative increase of stiffness between RT and RST. The hysteresis, on the other hand, decreased 17 +/- 20 % for RST, but was unchanged for RT. These results suggested that the resistance training increased the stiffness of tendon structures as well as muscle strength and size, and the stretching training affected the viscosity of tendon structures but not the elasticity.
Adaptations of arm and thigh muscle hypertrophy to different long-term periodized resistance training programs and the influence of upper body resistance training were examined.
Eighty-five untrained women (mean age = 23.1 +/- 3.5 yr) started in one of the following groups: total-body training [TP, N = 18 (3-8 RM training range) and TH, N = 21 (8-12 RM training range)], upper-body training [UP, N = 21 (3-8 RM training range) and UH, N = 19, (8-12 RM training range)], or a control group (CON, N = 6). Training took place on three alternating days per week for 24 wk. Assessments of body composition, muscular performance, and muscle cross-sectional area (CSA) via magnetic resonance imaging (MRI) were determined pretraining (T1), and after 12 (T2) and 24 wk (T3) of training.
Arm CSA increased at T2 (approximately 11%) and T3 (approximately 6%) in all training groups and thigh CSA increased at T2 (approximately 3%) and T3 (approximately 4.5%) only in TP and TH. Squat one-repetition maximum (1 RM) increased at T2 (approximately 24%) and T3 (approximately 11.5%) only in TP and TH and all training groups increased 1 RM bench press at T2 (approximately 16.5%) and T3 (approximately 12.4%). Peak power produced during loaded jump squats increased from T1 to T3 only in TP (12%) and TH (7%). Peak power during the ballistic bench press increased at T2 only in TP and increased from T1 to T3 in all training groups.
Training specificity was supported (as sole upper-body training did not influence lower-body musculature) along with the inclusion of heavier loading ranges in a periodized resistance-training program. This may be advantageous in a total conditioning program directed at development of muscle tissue mass in young women.
This study investigated the influence of static stretching exercises on specific exercise performances.
Thirty-eight volunteers participated in this study. The stretching group (STR) consisted of 8 males and 11 females whose activity was limited to a 10-wk, 40-min, 3-d.wk(-1) static stretching routine designed to stretch all the major muscle groups in the lower extremity. The control group (CON) consisted of 8 males and 11 females who did not participate in any kind of regular exercise routine during the study. Each subject was measured before and after for flexibility, power (20-m sprint, standing long jump, vertical jump), strength (knee flexion and knee extension one-repetition maximum (1RM)), and strength endurance (number of repetitions at 60% of 1RM for both knee flexion and knee extension).
STR had significant average improvements (P < 0.05) for flexibility (18.1%), standing long jump (2.3%), vertical jump (6.7%), 20-m sprint (1.3%), knee flexion 1RM (15.3%), knee extension 1RM (32.4%), knee flexion endurance (30.4%) and knee extension endurance (28.5%). The control group showed no improvement.
This study suggests that chronic static stretching exercises by themselves can improve specific exercise performances. It is possible that persons who are unable to participate in traditional strength training activities may be able to experience gains through stretching, which would allow them to transition into a more traditional exercise regimen.
The extent to which factors associated with muscle contraction activate Akt remains unclear. This study examined the influences of mechanical (active and passive tension), neural (activation frequency), and metabolic (glycogen depletion) factors on Akt activation during in situ contractions.
Muscle length was modified to produce comparable active contractile forces in three protocols, despite a twofold difference in stimulation frequency (15 vs 30 Hz); a fourth protocol used 30-Hz stimulation at optimal length to produce greater active forces. Two protocols were performed at optimal length, using 15- or 30-Hz stimulation (15 Hz opt and 30 H zopt, respectively). Two other protocols used 30-Hz stimulation at shortened or lengthened positions (30 Hz sub and 30 Hz supra, respectively).
The principal finding was that the 30-Hz opt protocol induced significantly greater Akt phosphorylation (approximately threefold relative to control) than did the other protocols, suggesting that activation of this signaling pathway is most sensitive to active tension. This result could not be attributed to differences in glycogen depletion, stimulation frequency, or fatigue. Despite producing the lowest force-time integral, the 30-Hz supra protocol, which had the greatest passive tension, exhibited a greater degree of Akt phosphorylation than did the 15-Hz opt and 30-Hz sub protocols. Although these differences were not significant, they suggest a possible secondary role for passive tension, which may interact with active tension in activating the Akt signaling pathway.
Akt activation seems more sensitive to active contractile tension than to passive tension. Activation frequency seems to play no role in the phosphorylation of Akt.
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