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Rey, E, Costa, PB, Corredoira, FJ, and Sal de Rellan Guerra, A. Effects of age on physical match performance in professional soccer players. J Strength Cond Res XX(X): 000-000, 2019-This study aimed to evaluate the effects of age using a large-scale analysis of match physical performance in professional soccer players. A total of 10,739 individual match observations were undertaken on outfield players competing in the first and second divisions of the Spanish soccer professional leagues during the 2017-2018 season, using a computerized tracking system (TRACAB, Chyronhego, New York, USA). The players were classified into five positions and into 5 age groups (

The purpose of this study was to investigate the acute effects of multi-joint resistance exercises (MJRE) with blood flow restriction on hormonal responses. Ten men participated in the study and underwent two experimental protocols in random order: four sets (30, 15, 15, and 15 reps, respectively) of MJRE (half squat and horizontal chest press) were performed with 20% of 1RM and a rest time between sets of 30 s, combined with intermittent blood flow restriction (LI + BFR protocol); and four sets (8, 8, 8, 20 reps, respectively) of the same MJRE performed with 75% of 1RM load (HI protocol), with a 90 s rest between the first three sets and 30 s between the third to the fourth set. Blood samples were collected before (PRE), immediately after (POST), and 15 min after the performance of MJRE (POST15). A time effect was observed for growth hormone (GH) and insulin-like-growth-factor-1-binding-protein-3 (IGFPB-3), but no protocol effects or interactions between protocol and times were observed (p > 0.05). There was no effect of either protocol or time (p > 0.05) on total testosterone, free testosterone, or cortisol concentrations. However, significant (p < 0.05) increases were observed in the GH serum concentrations of 2072.73% and 2278.5%, HI, and LI + BFR protocols, respectively, from the PRE to POST15 test. In addition, there was an increase of 15.30% and 13.29% in the IGFPB-3 concentrations (p < 0.05) from PRE to POST0 times for HI and LI + BFR protocols, respectively. Furthermore, there was a decrease of −6.17% and −11.54%, p = 0.00, between the times POST0 to POST15 in the IGFPB-3 for the HI and LI + BFR protocols, respectively. It is concluded that multi-joint resistance exercises combined with intermittent blood flow restriction seemed to promote acute hormonal responses in a manner similar to traditional exercise with high loads. Future studies may investigate whether chronic use of LI + BFR with MJRE may promote muscle hypertrophy.

BACKGROUND: Squats are considered one of the main exercises for the lower limbs and are used in resistance training under different contexts, including rehabilitation and sports performance. OBJECTIVE: To compare the EMG activity of different muscles in back squat and lunge exercises in trained women. METHODS: Ten healthy women experienced in resistance training performed back squat and lunge exercises on a Smith machine (total work: 70% of 1RM, 1 set, 10 repetitions and 2-s/2-s of execution speed) with an interval of 20-min between exercises. Both exercises were standardized in relation to the trunk inclination and were performed with an erect trunk parallel to the cursor of the guided bar. RESULTS: The EMG activity of the vastus medialis (VM), vastus lateralis (VL), biceps femoris (BF), and gluteus maximus (GM) were analyzed. There were no significant differences in the EMG activity of the VM, VL, and BF muscles between the back squat and lunge exercises (P> 0.05); however, GM activation was greater during the lunge exercise (effect size = 1.15; P= 0.001). CONCLUSIONS: Lunges were more effective in recruiting the GM when compared to back squats. However, both exercises can be recommended when the goal is knee extensor and flexor muscle activity.

Choe, KH, Coburn, JW, Costa, PB, and Pamukoff, DN. Hip and knee kinetics during a back-squat and deadlift. J Strength Cond Res 35(5): 1364-1371, 2021-The back-squat and deadlift are performed to improve hip and knee extensor function. The purpose of this study was to compare lower extremity joint kinetics (peak net joint moments [NJMs] and positive joint work [PJW]) between the back-squat and deadlift. Twenty-eight resistance-trained subjects (17 men: 23.7 ± 4.3 years, 1.76 ± 0.09 m, 78.11 ± 10.91 kg; 11 women: 23.0 ± 1.9 years, 1.66 ± 0.06 m, 65.36 ± 7.84 kg) were recruited. One repetition maximum (1RM) testing and biomechanical analyses occurred on separate days. Three-dimensional biomechanics of the back-squat and deadlift were recorded at 70 and 85% 1RM for each exercise. The deadlift demonstrated larger hip extensor NJM than the back-squat {3.59 (95% confidence interval [CI]: 3.30-3.88) vs. 2.98 (95% CI: 2.72-3.23) Nm·kg-1, d = 0.81, p < 0.001}. However, the back-squat had a larger knee extensor NJM compared with the deadlift (2.14 [95% CI: 1.88-2.40] vs. 1.18 [95% CI: 0.99-1.37] Nm·kg-1, d = 1.44 p < 0.001). More knee PJW was performed during the back-squat compared with the deadlift (1.85 [95% CI: 1.60-2.09] vs. 0.46 [95% CI: 0.35-0.58] J·kg-1, d = 2.10, p < 0.001). However, there was more hip PJW during the deadlift compared with the back-squat (3.22 [95% CI: 2.97-3.47] vs. 2.37 [95% CI: 2.21-2.54] J·kg-1, d = 1.30, p < 0.001). Larger hip extensor NJM and PJW during the deadlift suggest that individuals targeting their hip extensors may yield greater benefit from the deadlift compared with the back-squat. However, larger knee extensor NJM and PJW during the back-squat suggest that individuals targeting their knee extensor muscles may benefit from incorporating the back-squat compared with the deadlift.

The aim of this study was to assess the effects of plyometric training with an agility ladder on components of physical fitness in youth soccer players. A total of twenty male under-13 soccer players were randomly assigned to a plyometric training group with an agility ladder (n=10) or a control group (n=10). Before and after training intervention linear sprint test (5 m, 10 m, 20 m), vertical jump ability (squat jump, countermovement jump and countermovement jump with arms), agility test, and slalom dribble test were assessed. The plyometric training with agility ladder was applied two times per week over six weeks. Data were analyzed using linear mixed model. The plyometric training group showed significant improvements (p0.05). The between-group analysis showed significant differences in countermovement jump with arms (p=0.03), but no significant differences (p>0.05) were found in squat jump, countermovement jump, sprint, agility test, and slalom dribble test. In conclusion, the short-term plyometric training with agility ladder seems to be ineffective and not time-efficient to improve physical fitness in youth soccer players. However, the interpretation of these results must be understood within the sample size limitations.

Apoptosis is a specific form of programmed cell death that plays an important role in tissue homeostasis and also occurs during aging. In addition, exercise training may alter apoptosis-related signaling in muscles, including the cardiac muscle. However, the effects of high-intensity interval training (HIIT) on apoptosis markers in the heart have not yet been studied. Thus, the aim of the present study was to investigate the effects of HIIT on Bcl-2 and Bax expression protein levels in young and old cardiac muscles. Four and 24-month old C57BL/6J mice were used as our young adult and old groups, respectively. Animals were randomly assigned to four groups: young control (YC), young trained (YT), old control (OC), and old trained (OT). The trained groups performed HIIT 5 sessions per week for 4 weeks. RNA extraction and synthesis of cDNA was performed, and Bax and Bcl2 heart gene levels were determined by RT-PCR analysis. Training induced significant increases in Bcl-2 gene expression in YT group comparing to the YC group (p = 0.010) and in OT group comparing to OC group (p = 0.002). Training induced non-significant decrease (p > 0.05) in Bax gene expression and in Bax/Bcl-2 ratio in YT group comparing to the YC group and in OT group comparing to OC group. Aging showed no significant effect in Bcl-2 gene expression, Bax gene expression, and Bax/Bcl-2 ratio in CY group comparing to the OC group and in YT group comparing to OT group (p > 0.05). In conclusion, 4 weeks of HIIT increased Bcl-2 level for young and old heart muscles, and no effect of aging was revealed, indicating that HIIT ameliorated anti-apoptotic signaling in the young and old heart of mice.

This study evaluated the effects of age on physical and technical game performance for different positions in professional basketball players. In this cross-sectional study, a total of 25,523 individual match observations were undertaken on players from the 2018-19 NBA season. The players were classified into four age groups (19-22 years, 23-25 years, 26-29 years, and 30-42 years). Differences in physical and technical match performance were analysed for the following variables: distance covered, average speed, minutes played, points scored and playing efficiency. The results showed that players older than 30 covered shorter distance and had lower average speed than younger players, that guards and forwards older than 26 played more minutes per game than younger ones, and that guards older than 26 scored more points and were more efficient than younger one, while centres age 23-25 scored more points per games than centres older than 30. In conclusion, physical performance declined with age, and while playing time and technical performance generally remained stable or increased, especially for guards. However, there was some evidence of decline for centres.

The aim of this study was to analyse the effect of the score-line on the internal and external load in soccer small-sided games (SSGs). Thirty male semi-professional soccer players particip...

Individuals with lower-limb amputations may have a significant strength deficit. This deficit may be related to the stump length and can lead to changes in gait, reduced energy efficiency, walking resistance, altered joint load, and increased risk of osteoarthritis and chronic low back pain. This systematic review used the Preferred Reporting Items for Systematic Reviews and Meta-Analyzes (PRISMA) guidelines to examine the effects of resistance training in lower limb amputees. Interventions with resistance training and other training methods were sufficient to achieve muscle strength gain in muscles of the lower limbs, improved balance, and improvements in gait pattern and speed when walking. However, it was impossible to determine from the results whether resistance training was mainly responsible for these benefits or even whether the positive effects presented would be observed with only this training method. When combined with other exercises, interventions with resistance training made possible gains for this population. Accordingly, it is noteworthy that the main finding of this systematic review is that the effects may be different according to the level of amputation, with mainly transtibial and transfemoral amputations studied.

Introduction: It is common for postmenopausal women to receive a vitamin D supplementation prescription to assist in preventing future falls and to maintain bone health. However, the association between vitamin D supplementation and physical fitness components has not been studied in older women with diabetes. Objective: We examined the influence of 12 months of vitamin D supplementation on the components of physical fitness in postmenopausal women with type 2 diabetes mellitus (T2DM). Methods: Thirty-five postmenopausal women (62.48 ± 7.67 years, 154.6 ± 5.11 cm, 73.93 ± 15.43 kg, 31.13 ± 5.82 BMI) with a diagnosis of T2DM participated in this longitudinal study where participants were supplemented with 1000 IU/day of vitamin D over 12 months. Subjects performed fasting blood samples, anthropometric assessments, body composition, clinical exams, and physical tests at 6-month intervals (P0, P6, and P12). Results and Conclusion: Vitamin D supplementation alone was effective in postmenopausal women in increasing serum vitamin D levels, altering muscle strength levels, promoting improvements in muscle function, as well as preventing and controlling fragility caused by T2DM and aging.

The aim of this study was to compare the effectiveness of acute of contract–relax (CR) and contract–relax–antagonist–contraction (CRAC) targeting the quadriceps, hamstrings, anterior tibialis, and calf muscles and warm-up without stretching on medio-lateral (ML) and antero-posterior (AP) dynamic balance control in healthy young men applied by a physiotherapist in comparison to a control intervention without stretching. Twenty healthy young men between the age of 18 and 25 performed three interventions in randomized days after standard warm-up: CR intervention, CRAC intervention, and control intervention. ML and AP dynamic balance control was carried out before (Pre) and immediately after (Post) each intervention. Antero-posterior sway (AP sway) and medio-lateral sway (ML sway) under vision and no vision condition were analyzed by posturography. CRAC intervention improved significantly ML dynamic balance control by decreasing ML sway (vision, p = 0.006 and no vision, p

The aim of this study was to determine the effects of 2 different repeated-sprint ability (RSA) training frequencies (2 RSA sessions per week [RSA2D] or 1 RSA session [RSA1D]) under volume-equated conditions on sprint and RSA performance in under-15 (U15) soccer players. Twenty-seven youth male soccer players (age: 12.29±0.47 years; height: 158.35±10.86 cm; weight: 45.08±8.05 kg) were randomly assigned to RSA2D (n=14) or RSA1D (n=13) groups. The players performed the same RSA training for 6 weeks, and only the training frequency differed between the groups. Before and after the training period, 5 m sprint, 10 m sprint, 20 m sprint and the RSA test were assessed. No significant time × group interactions were observed (p>0.05). Within-group analysis showed significant improvements in 20 m sprint (p=0.046, partial eta squared [ηp2 ] = 0.150, large) and RSA average time (p=0.001, ηp2 =0.438, large), fastest time (p=0.012, ηp2 =0.229, large), and total time (p=0.001, ηp2 =0.438, large) from pre-test to post-test in RSA1D and RSA2D groups. However, no significant pre-post changes (p>0.05) were found in 5 m and 10 m sprint tests. In the between-group analysis, there were no significant differences between RSA1D and RSA2D groups in any variable. In conclusion, the current findings suggest that 6 weeks of RSA training 1 or 2 times per week in addition to typical soccer training produced significant and similar improvements in sprint and RSA performances. This information could be useful for coaches when planning training sessions during congested fixtures of soccer competitions or in periods when the emphasis should be placed on other physical qualities.

PURPOSE Obesity influences gait and muscle function, which may contribute to knee osteoarthritis. This study aimed 1) to compare gait biomechanics and quadriceps function between individuals with and without obesity and 2) to examine the association between quadriceps function and gait biomechanics. METHODS Forty-eight individuals with and 48 without obesity participated and were matched on age and sex. Gait biomechanics at standardized and self-selected speeds were used to assess peak vertical ground reaction force (vGRF), vertical loading rate (vLR), internal knee extension moment (KEM), peak knee flexion angle (KFA), knee flexion excursion (KFE), and knee joint stiffness. Quadriceps function was assessed using peak isometric strength (peak torque), early (RTD100) and late (RTD200) rate of torque development (RTD), and vastus lateralis cross-sectional area (CSA) and echo intensity (EI). RESULTS When normalized to fat-free mass, individuals with obesity had lower RTD100 (P = 0.04) and RTD200 (P = 0.02) but higher vastus lateralis CSA (P < 0.01) and EI (P < 0.01) compared with normal weight controls. The group-speed interaction was significant for normalized vGRF (P < 0.01), normalized vLR (P = 0.02), normalized KEM (P = 0.03), and normalized knee joint stiffness (P = 0.02). Post hoc analyses indicate a smaller normalized vGRF and normalized KEM, and lower knee joint stiffness in individuals with obesity compared with normal weight controls at self-selected speed. There were main effects of speed for all kinematic and kinetic variables, and body mass index group for all absolute kinetic variables as well as normalized vGRF (all P < 0.001). A lower vastus lateralis EI (P = 0.04) and greater RTD100 (P < 0.01) were associated with a larger KEM in individuals with obesity. CONCLUSION Individuals with obesity have quadriceps dysfunction that is weakly associated with KEM during walking. Exercise interventions that improve quadriceps function may improve walking mechanics.

Bagley, JR, Burghardt, KJ, McManus, R, Howlett, B, Costa, PB, Coburn, JW, Arevalo, JA, Malek, MH, and Galpin, AJ. Epigenetic responses to acute resistance exercise in trained vs. sedentary men. J Strength Cond Res 34(6): 1574-1580, 2020-Acute resistance exercise (RE) alters DNA methylation, an epigenetic process that influences gene expression and regulates skeletal muscle adaptation. This aspect of cellular remodeling is poorly understood, especially in resistance-trained (RT) individuals. The study purpose was to examine DNA methylation in response to acute RE in RT and sedentary (SED) young men, specifically targeting genes responsible for metabolic, inflammatory, and hypertrophic muscle adaptations. Vastus lateralis biopsies were performed before (baseline), 30 minutes after, and 4 hours after an acute RE bout (3 × 10 repetitions at 70% 1 repetition maximum [1RM] leg press and leg extension) in 11 RT (mean ± SEM: age = 26.1 ± 1.0 years; body mass = 84.3 ± 0.2 kg; leg press 1RM = 412.6 ± 25.9 kg) and 8 SED (age = 22.9 ± 1.1 years; body mass = 75.6 ± 0.3 kg; leg press 1RM = 164.8 ± 22.5 kg) men. DNA methylation was analyzed through methylation sensitive high-resolution melting using real-time polymerase chain reaction. Separate 2 (group) × 3 (time) repeated-measures analyses of variance and analyses of covariance were performed to examine changes in DNA methylation for each target gene. Results showed that acute RE (a) hypomethylated LINE-1 (measure of global methylation) in RT but not SED, (b) hypermethylated metabolic genes (GPAM and SREBF2) in RT, while lowering SREBF2 methylation in SED, and (c) did not affect methylation of genes associated with inflammation (IL-6 and TNF-α) or hypertrophy (mTOR and AKT1). However, basal IL-6 and TNF-α were lower in SED compared with RT. These findings indicate the same RE stimulus can illicit different epigenetic responses in RT vs. SED men and provides a molecular mechanism underpinning the need for differential training stimuli based on subject training backgrounds.

Madoni, SN, Costa, PB, Coburn, JW, and Galpin, AJ. Effects of foam rolling on range of motion, peak torque, muscle activation, and the hamstrings-to-quadriceps strength ratios. J Strength Cond Res 32(7): 1821-1830, 2018-To examine the effects of foam rolling (FR) on range of motion (ROM), peak torque (PT), hamstrings-to-quadriceps (H:Q) ratios, and muscle activation. Twenty-two recreationally active women (mean age ± SD = 21.55 ± 1.82 years, 161.91 ± 6.58 cm, 61.47 ± 10.54 kg) volunteered for this study. Participants performed pre- and posttests analyzing PT and surface electromyography (EMG) of their dominant limb, completing maximal knee extension and flexion at 3 different velocities. Participants foam rolled the hamstrings muscles or sat for the control condition between the pre- and posttests. Hamstrings ROM increased in the FR condition from (mean ± SE) 123.23 ± 3.49 to 126.41 ± 3.62° (p0.001) and decreased in the control condition from 118.82 ± 4.25 to 117.95 ± 4.29° (p = 0.013). Concentric hamstrings PT and conventional H:Q ratios decreased after both conditions, with smaller decreases after FR (p ≤ 0.05). No significant changes were found for eccentric hamstrings PT, eccentric hamstrings EMG, or functional H:Q ratios (p0.05). Foam rolling resulted in greater changes in hamstrings ROM without creating a deficit in PT or muscle activation when compared with the control group. When compared with other methods of stretching, FR may be beneficial in increasing ROM without decreasing functional H:Q ratios.

Background: A new fitness trend incorporates stability exercises that challenges trunk muscles and introduces crawling as an exercise, but has yet to be investigated for muscle activity. Purpose: To compare the effects of static (STA), stationary (STN), and traveling (TRV) trunk exercises on muscle activation of the rectus abdominis, rectus femoris, external oblique, and erector spinae using surface electromyography (EMG). Methods: Seventeen recreationally active women (mean age ± SD = 22.4 ± 2.4 years, body mass 62.9 ± 6.9 kg, height 165.1 ± 5.8 cm) and twenty-three men (23.6 ±3.9 years, 83.2 ±17.1 kg, 177.1 ± 9.1 cm) volunteered to participate in this study. Subjects performed maximal voluntary contractions for normalization of each muscle’s EMG activity. They then performed the three exercises in random order for thirty seconds each with a two-minute rest in between. Results: For the rectus abdominis, STA was significantly lower than STN (P = 0.003) and TRV (P = 0.001). For the external oblique, STA was significantly lower than STN (P = 0.001) and TRV (P = 0.001) and STN was significantly greater than TRV (P = 0.009). For the erector spinae and rectus femoris, STA was significantly lower than STN (P = 0.001) and TRV (P = 0.001) Conclusions: There was greater muscle activation in all muscles tested in the stationary and traveling exercises versus the static. Strength and conditioning coaches and allied health professionals could potentially use stationary and traveling forms of trunk stabilization exercises as a viable strategy to increase muscle activation.

The aim of this study was to examine changes in muscle contractile properties across a microcycle of training in professional soccer players during the in-season period. Nineteen professional soccer players were assessed with tensiomyography (TMG) on the biceps femoris and rectus femoris before and after 5 training sessions of an in-season microcycle. Training load was quantified during each training session. Significant differences were observed in training load variables across different training sessions, with the last training session prior to match day showing the lowest values for all training load variables. Significant pre- to post-session increases were observed in muscle stiffness of the rectus femoris and biceps femoris during the first four training sessions (effect size range, 0.5 to 0.9). However, no significant differences were observed in muscle contraction time and contraction velocity from pre- to post-session. In addition, repeated measures correlation analysis revealed significant relationships between absolute change in muscle stiffness of the rectus femoris and training duration, high-speed distance covered during training, and training average distance. The current study shows that players are physically taxed on their muscular stiffness by the training load. Post-session muscular stiffness assessment should be recommended to determine neuromuscular status and readiness in professional soccer players during the competitive season.

Summary Objective Muscle stretching is plenty used prior to training and competition. Considering the importance of balance control in performance, muscle stretching is expected to have positive effects on balance. However, there is a lack of studies investigating the effects of contract-relax proprioceptive neuromuscular facilitation (CR PNF) stretching on balance control. The purpose of this study was to investigate the effects of CR PNF stretching on static postural balance. Methods Fourteen subjects were tested before and after a 5-minute cycle warm-up followed by 10 minutes of CR PNF stretching (stretching condition) and the same cycle warm-up with 10-minute rest periods (control condition). The four muscle groups stretched were the quadriceps, hamstrings, anterior tibialis, and calf muscles of both legs in an alternating manner. Postural balance was assessed in a bipedal static stance before and after each condition with eyes opened (EO) and eyes closed (EC). Results No significant interactions for any postural parameters. However, there was a significant main effect of condition for sway area (P 0.05). Conclusion It appears that the stretching and control conditions impaired static balance control by increasing postural sway. CR PNF stretching was unable to compensate for the warm-up and its effects of induced alteration in postural balance.

Ultrasound muscle images have been extensively used as tools for investigating, diagnosing and monitoring thigh muscles. However, there is a lack of information examining ultrasound reliability of quadriceps and hamstrings images for research and clinical use. Objectives: To determine the reliability of muscle thickness (MT), echo intensity (EI) and cross sectional area (CSA) of quadriceps and hamstrings muscle groups. Methods: Single transverse images of the rectus femoris (RF), vastus intermedius (VI), vastus medialis (VM), vastus lateralis (VL), biceps femoris long head (BFlh), semitendinosus (ST), and semimembranosus (SM) muscles were scanned in the right and left legs of ten healthy collegiate men (age 23.4 ± 2.2 yrs, mass 71.7 ± 11.7 kg, height 1.73 ± 0.06 m) between two sessions with one day interval. Intraclass correlation coefficients (ICCs), standard error of measurement (SEM), and minimum difference to be considered “real” (MD) were measured for MT, EI, and CSA. Results: A range of 0.97-0.99, 0.83-0.88, and 0.86-0.97 (ICC); 0.72-1.38, 2.73-3.41, and 0.36-1.04 (SEM); and 2.01-3.82, 7.56-9.46, and 0.99-2.89 (MD) were found for quadriceps muscles, and 0.93-0.99, 0.74-0.90, and 0.89-0.96 (ICC); 0.73-1.94, 3.29-4.98, and 0.69-1.08 (SEM); and 2.03-5.38, 9.13-13.81, and 1.91-2.98 (MD) were found for hamstrings muscles. Conclusions: These results suggest that ultrasound imaging of both quadriceps and hamstrings muscle architecture is a reliable technique for assessing thigh musculoskeletal tissue. The anatomical sites, as well as ultrasound adjustments, images, and results utilized here may assist future researchers and clinicians as reference tools when measuring quadriceps and hamstrings musculature.

Monteiro, ER, Costa, PB, Corrêa Neto, VG, Hoogenboom, BJ, Steele, J, and da Silva Novaes, J. Posterior thigh foam rolling increases knee extension fatigue and passive shoulder range-of-motion. J Strength Cond Res 33(4): 987-994, 2019-The purpose of this study was to analyze the acute effects of different foam rolling (FR) volumes on knee extensors fatigue and shoulder passive range-of-motion (PROM). Twelve recreationally active women were recruited for participation in 2 experiments separated by 3 weeks, and the same subjects performed all procedures in each experiment. In experiment 1, subjects performed 3 sets of knee extensions using a predetermined 10 repetition maximum load to momentary concentric failure: control condition (CG) with passive rest and 2 FR conditions for the hamstrings using 2 volumes (60 and 120 seconds; FR60 and FR120, respectively). Experiment 2 consisted of 2 shoulder flexion and extension baseline PROM tests. Following baseline measures, subjects performed a single 60-second bout of FR on the hamstrings. Outcome PROM measures were measured through manual goniometry immediately (post-0), 10 minutes (post-10), 20 minutes (post-20), 30 minutes (post-30), 24 hours (post-24), and 48 hours (post-48) after the intervention to assess the effects on PROM over an extended period. Fatigue index indicated significantly greater fatigue resistance for CG when compared with FR60 (p = 0.035; [INCREMENT]% = 6.49) and FR120 (p = 0.002; [INCREMENT]% = 9.27), and there were no significant differences between FR60 and FR120 (p = 0.513; [INCREMENT]% = 2.78). Shoulder flexion PROM increased in post-0 as compared to baseline 1 (p = 0.002; d = 1.58), baseline 2 (p < 0.001; d = 1.92), and baseline higher measurement (p < 0.001; d = 1.59) and remained increased for post-10 as compared to baseline 2 (p = 0.017; d = 1.55). Shoulder extension PROM increased in post-0 as compared to baseline 1 (p < 0.001; d = 2.61), baseline 2 (p < 0.001; d = 2.83), and baseline higher measurement (p < 0.001; d = 2.59) and remained increased for post-10 as compared to baseline 1 (p < 0.001; d = 1.93), baseline 2 (p < 0.001; d = 2.16), and baseline higher measurement (p < 0.001; d = 1.91) and post-20 as compared to baseline 1 (p = 0.008; d = 1.58), baseline 2 (p = 0.001; d = 1.85), and baseline higher measurement (p = 0.011; d = 1.55). Foam rolling volumes equal to or greater than 60 seconds are detrimental to the ability to continually produce force in the lower extremity and should not be applied to the hamstrings muscle group between sets of knee extensions. PROM results indicate that FR applied to the hamstrings demonstrates an increase in both shoulder flexion and extension PROM. This work may have important clinical (rehabilitation) implications, as it demonstrates global effects of FR on functional outcomes.

Background: The effects of proprioceptive neuromuscular facilitation (PNF) stretching on muscle imbalance are not fully understood. The aim of this study was to examine the acute effects of PNF stretching on knee extension and flexion peak torque (PT), as well as the conventional and functional hamstrings to quadriceps (H:Q) ratios. Methods: Fifteen men (age = 22 &plusmn, 1 years, body mass = 76 &plusmn, 12 kg, height = 176 &plusmn, 7 cm) and fifteen women (age = 22 &plusmn, 2 years, body mass = 63 &plusmn, 8 kg, height = 161 &plusmn, 5 cm) performed concentric quadriceps and hamstrings, and eccentric hamstrings muscle actions at different angular velocities (60, 180, and 300&deg, &middot, s&minus, 1 concentric, 60 and 180&deg, 1 eccentric) before and after a bout of PNF stretching, and a control condition. Results: Neither PNF or control conditions affected concentric PT or H:Q ratios (p &gt, 0.05), apart from knee extension at 60&deg, 1 in men (p = 0.001). However, there was a reduction in hamstrings eccentric PT in both control and PNF conditions for men and women (p = 0.003). Conclusions: PNF stretching of the hamstrings may not adversely affect the H:Q ratios, and consequently not negatively affect injury risk associated with muscular strength imbalances.

BACKGROUND The present study examined the acute effects of hamstrings stretching and fatigue on knee extension and flexion peak torque (PT), hamstrings to quadriceps (H:Q) ratio, and postural stability. METHODS Seventeen women (mean±SD age=21.8±2.1 years; body mass=63.0±10.5 kg; height=164.7±6.2 cm) and eighteen men (25.8±4.6 years; 83.6±13.2 kg; 175.3±6.0 cm) took part in three laboratory visits. The first visit was a familiarization session, and the subsequent two visits were randomly assigned as a control or stretching condition. For the testing visits, subjects performed a postural stability assessment, stretched (or sat quietly during the control condition), performed a 50-repetition unilateral isokinetic fatigue protocol, and repeated the postural stability assessment. RESULTS There were no significant differences between control and stretching conditions for initial quadriceps and hamstrings PT, initial H:Q ratio, quadriceps and hamstrings PT fatigue indexes, H:Q ratio Fatigue Index, rating of perceived exertion (RPE), or postural stability (P>0.05). When analyzing 5 intervals of 10 repetitions, significant declines in quadriceps PT were found in all intervals for both conditions (P

The effects of low-intensity resistance exercise (RE) combined with blood flow restriction (BFR) on blood pressure (BP) are an important factor to be considered because of the acute responses imposed by training. The aim of this study was to compare the hypotensive effect of RE performed with and without BFR in normotensive young subjects. After 1 repetition maximum (1RM) tests, 24 men (21.79 ± 3.21 years; 1.72 ± 0.06 m; 69.49 ± 9.80 kg) performed the following 4 experimental protocols in a randomized order: (a) high-intensity RE at 80% of 1RM (HI), (b) low-intensity RE at 20% of 1RM (LI), (c) low-intensity RE at 20% of 1RM combined with partial BFR (LI + BFR), and (d) control. Analysis of systolic blood pressure (SBP) and diastolic blood pressure (DBP) was conducted over a 60-minute period. The 3 RE protocols resulted in hypotensive SBP (HI = -3.8%, LI = -3.3%, LI + BFR = -5.5%) responses during the 60 minutes (p ≤ 0.05). The LI + BFR protocol promoted hypotensive (-11.5%) responses in DBP during the 60 minutes (p ≤ 0.05), and both the HI and LI + BFR protocols resulted in mean blood pressure (MBP) hypotension between 30 (-7.0%, -7.7%) and 60 minutes (-3.6%, -8.8%), respectively. In conclusion, postexercise hypotension may occur after all 3 exercise protocols with greater reductions in SBP after HI and LI + BFR, in DBP after LI + BFR, and in MBP after HI and LI + BFR protocols.

Large imbalances between limbs are common and potentially dangerous, yet few studies have simultaneously examined performance and physiological asymmetries. The current study examined the associations between lower-limb dominance, drop-jumping kinematics, maximal strength, and myosin heavy-chain (MHC) fiber type in the vastus lateralis.Thirteen resistance-trained men (age, 24.3 ± 2.7 yr; height, 181.4 ± 6.6 cm; mass, 87.7 ± 11.3 kg) identified their dominant (DOM) and nondominant (ND) limb, performed drop jumps (30 cm) and maximal knee extensions (1-repetition maximum, or 1RM), and provided biopsies from both vastus lateralis muscles for single-fiber (109 ± 36 per limb per person) MHC fiber-type identification (FT%).All participants selected "right" as the "preferred kicking limb" (DOM). DOM displayed a trend for a greater eccentric knee angular velocity (EKV; P = 0.083) and a significantly greater concentric knee angular velocity (CKVl P = 0.002) during drop jump. DOM also tended to be stronger than ND (64.3 ± 11.3 vs 61.0 ± 8.8 kg, P = 0.063). Slow-twitch (MHC I) fibers were more prevalent in DOM (P0.025), whereas ND contained more fast-twitch (MHC IIa; P0.025). No correlations existed between categories (jumping, 1RM, and FT%). Asymmetries of5% were present in 6 of 12 participants for EKV, 2 of 12 for CKV, 6 of 13 for 1RM, 12 of 13 for MHC I, and 11 of 13 for MHC IIa. However, only a single participant expressed asymmetries of5% in all dependent variables (EKV, CKV, 1RM, MHC I, and MHC IIa).Several statistically and clinically relevant asymmetries were identified. The FT% differences between lower limbs were large and common. The findings also seem to conclude that DOM was stronger, moved faster, and contained more MHC I. However, only 23% of participants actually displayed that result. This highlights the need to analyze and report both group and individual data, particularly when interpreting findings across multiple related, but not necessarily causal, measurements.

Rey, E, Padron-Cabo, A, Costa, PB, and Barcala-Furelos, R. Effects of foam rolling as a recovery tool in professional soccer players. J Strength Cond Res 33(8): 2194-2201, 2019-Foam rolling (FR) is a common strategy used after training and competition by players. However, no previous studies have assessed the effectiveness of FR as a recovery tool in sports populations. The aim of this study was to examine the effectiveness of FR (20 minutes of FR exercises on quadriceps, hamstrings, adductors, gluteals, and gastrocnemius) and passive recovery (20 minutes sit on a bench) interventions performed immediately after a training session on Total Quality Recovery (TQR), perceived muscle soreness, jump performance, agility, sprint, and flexibility 24 hours after the training. During 2 experimental sessions, 18 professional soccer players (age 26.6 ± 3.3 years; height: 180.2 ± 4.5 cm; body mass: 75.8 ± 4.7 kg) participated in a randomized fully controlled trial design. The first session was designed to collect the pretest values of each variable. After baseline measurements, the players performed a standardized soccer training. At the end of training unit, all the players were randomly assigned to the FR recovery group and the passive recovery group. A second experimental session was conducted to obtain the posttest values. Results from the between-group analyses showed that FR had a large effect on the recovery in agility (effect sizes [ES] = 1.06), TQR (ES = 1.08), and perceived muscle soreness (ES = 1.02) in comparison with the passive recovery group at 24 hours after training. Thus, it is recommended that soccer coaches and physical trainers working with high-level players use a structured recovery session lasting from 15 to 20 minutes based on FR exercises that could be implemented at the end of a training session to enhance recovery between training loads.

Walking is not only important to assist in performing daily tasks, but also to gain cardiovascular benefits. Further research on walking is needed to examine the physiological responses to improve health and reduce the risks of cardiovascular disease. The purpose of this study was to compare the energy expenditure (EE) during and after walking exercise with versus without hand-held weights (HHW). Nineteen sedentary women (mean±standard deviation; age, 21±2.7 years, height, 163.1±6.3 cm; body mass, 66.6± 15.1 kg; body fat %, 30.6%± 7.43%; body mass index, 25.5± 5.7 kg/m2) volunteered walking with versus without 1.36 kg of HHW in two randomized sessions. The study consisted of 30 min of exercise followed b silent sitting for 30 min. The range of motion was set at elbow flexion at 90° while arms were alternated 30.48 cm forward and backward. 1% incline was set for the treadmill grade and speed was controlled to a moderate level of 40%-59% of heart rate reserve. During the 30-min exercise no significant differences were found between the conditions (P> 0.05). The physiological responses were significantly greater directly after exercise compared with baseline as determined from pairwise comparisons collapsed across conditions (P≤ 0.05). Walking with HHW was not substantial enough to raise EE beyond normal walking and led to an increased effort level. Additionally, the moderate intensity of walking was not enough to sustain EE at a surpassing level directly after the exercise.

Ruas, CV, Brown, LE, Lima, CD, Costa, PB, and Pinto, RS. Effect of three different muscle action training protocols on knee strength ratios and performance. J Strength Cond Res 32(8): 2154-2165, 2018-Hamstring to quadriceps (H:Q) ratios are often used to assess strength imbalances. The aims of this study were to compare 3 different muscle action training protocols on H:Q strength balance and functional performance. Forty untrained men (age: 22.87 ± 2.28 years, mass: 70.66 ± 11.049 kg, ht: 174.29 ± 6.90 cm) performed 6 weeks of training on an isokinetic dynamometer. They were randomly assigned to one of 4 groups; concentric quadriceps and concentric hamstring (CON/CON), eccentric quadriceps and eccentric hamstring (ECC/ECC), concentric quadriceps and eccentric hamstring (CON/ECC), or no training. Mixed Factor analyses of variance were used to compare interactions for variables pretest and posttest between groups (p ≤ 0.05). The ECC/ECC group showed significant increases in H:Q functional ratio (pre = 0.73 ± 0.092, post = 0.87 ± 0.098), ECC peak torque (PT) (pre = 226.44 ± 67.80 N·m, post = 331.74 ± 54.44 N·m), isometric PT (IPT) (pre = 173.69 ± 41.41 N·m, post = 203.091 ± 30.82 N·m), countermovement jump (CMJ) (pre = 52.73 ± 6.95 cm, post = 58.16 ± 6.10 cm), and drop jump (DJ) (pre = 52.91 ± 6.080 cm, post = 58.20 ± 7.72 cm), whereas the CON/CON group increased the rate of torque development (pre = 152.19 ± 65.0074 N·m·s, post = 225.26 ± 88.80 N·m·s). There were no differences between groups for CON PT, squat jump, conventional ratio or 40 m sprint. Our findings suggest that ECC/ECC training may be the most effective at increasing functional H:Q strength ratios, as well as ECC PT, IPT, CMJ, and DJ performance. Eccentric training increases ECC PT, thereby increasing the functional H:Q ratio. Eccentric training also improves vertical jumping involving ECC actions. CON/CON training may be more effective at increasing explosive muscle strength.

This study aimed to examine the acute effects of dynamic stretching on concentric leg extensor and flexor peak torque, eccentric leg flexor peak torque, and the conventional and functional hamstring-quadriceps (H:Q) ratios.Twenty-one women (mean ± SD age = 20.6 ± 2.0 yr, body mass = 64.5 ± 9.3 kg, height = 164.7 ± 6.5 cm) performed maximal voluntary isokinetic leg extension, flexion, and eccentric hamstring muscle actions at the angular velocities of 60°·s and 180°·s before and after a bout of dynamic hamstring and quadriceps stretching as well as a control condition.Leg flexion peak torque decreased under both control (mean ± SE for 60°s = 75.8 ± 4.0 to 72.4 ± 3.7 N·m, 180°·s = 62.1 ± 3.2 to 59.1 ± 3.1 N·m) and stretching (60°·s = 73.1 ± 3.9 to 65.8 ± 3.3 N·m, 180°·s = 61.2 ± 3.3 to 54.7 ± 2.6 N·m) conditions, whereas eccentric hamstring peak torque decreased only after the stretching (60°·s = 87.3 ± 5.1 to 73.3 ± 3.6 N·m, 180°·s = 89.2 ± 4.4 to 77.0 ± 3.4 N·m) intervention (P ≤ 0.05). Stretching also caused a decrease in conventional H:Q (60°·s = 0.58 ± 0.02 to 0.54 ± 0.02, 180°·s = 0.67 ± 0.02 to 0.61 ± 0.03) and functional H:Q ratios (60°·s = 0.69 ± 0.03 to 0.60 ± 0.03, 180°·s = 1.00 ± 0.06 to 0.60 ± 0.03) (P ≤ 0.05).Because dynamic stretching reduced concentric and eccentric hamstring strength as well as the conventional and functional H:Q ratios, fitness and allied-health professionals may need to be cautious when recommending dynamic rather than static stretching to maintain muscle force.

Background: Aerial fitness is quickly gaining popularity, however, little is known regarding the physiological demands of aerial athletes. The purpose of the study was to examine contralateral muscle imbalances, compare dominant versus non-dominant hamstrings-to-quadriceps (H:Q) ratios, and to establish a physiological profile of recreational aerial athletes. Methods: Thirteen aerialist women visited a local aerial studio to participate in a data collection session to examine isometric levels of upper and lower body strength, muscle endurance, flexibility, balance, and cardiovascular fitness. Results: No significant differences were found between dominant and non-dominant hand grip strength (p = 0.077), dominant and non-dominant isometric knee flexion (p = 0.483), dominant and non-dominant isometric knee extension (p = 0.152), or dominant and non-dominant isometric H:Q ratios (p = 0.102). In addition, no significant difference was found between isometric dominant H:Q ratio and the widely-used value of 0.60 (p = 0.139). However, isometric non-dominant H:Q ratio was significantly lower than the 0.60 criterion (p = 0.004). Aerial athletes demonstrated to have excellent flexibility, balance, cardiorespiratory fitness, and average strength. Conclusions: Aerial fitness may be another recreational activity that could be used to maintain higher levels of flexibility, balance, cardiorespiratory fitness, and strength. Aerialists may want to consider focusing on strengthening the lower body and balancing the hamstrings and quadriceps muscle strength.

The purpose of this study was to examine the effects of 2 different types of protein supplementation on thigh muscle cross-sectional area (CSA), blood markers, muscular strength, endurance, and body composition after 8 weeks of low- or moderate-volume resistance training in healthy, recreationally trained, college-aged men. One hundred and six men were randomized into 5 groups: low-volume resistance training with bioenhanced whey protein (BWPLV; n = 22), moderate-volume resistance training with BWP (BWPMV; n = 20), moderate-volume resistance training with standard whey protein (SWPMV; n = 22), moderate-volume resistance training with a placebo (PLA; n = 21), or moderate-volume resistance training with no supplementation (CON; n = 21). Except for CON, all groups consumed 1 shake before and after each exercise session and one each on the nontraining day. The BWPLV, BWPMV, and SWPMV groups received approximately 20 g of whey protein per shake, whereas the BWP groups received 5 g of additional polyethylene glycosylated (PEG) leucine. Resistance training sessions were performed 3 times per week for 8 weeks. There were no interactions (p > 0.05) for muscle strength and endurance variables, body composition, muscle CSA, and safety blood markers, but the main effects for training were observed (p ≤ 0.05). However, the Albumin:Globulin ratio for SWPMV was lower (p = 0.037) than BWPLV and BWPMV. Relative protein intake (PROREL) indicated a significant interaction (p < 0.001) with no differences across groups at pre; however, BWPLV, BWPMV, and SWPMV had a greater intake than did PLA or CON at post (p < 0.001). This study indicated that 8 weeks of resistance training improved muscle performance and size similarly among groups regardless of supplementation.

The reliability of the interpolated twitch technique during submaximal and maximal isometric muscle actions. J Strength Cond Res 27(10): 2909-2913, 2013-The purpose of this study was to examine the test-retest reliability of the percent voluntary activation (%VA) vs. force relationships. Fourteen healthy men (mean ± SD age = 21 ± 2.6 years) and 8 women (age = 21 ± 1.8 years) completed 4 maximal voluntary contractions (MVCs) and 9 randomly ordered submaximal isometric plantar flexions from 10 to 100% of the MVC. Transcutaneous electrical stimuli were delivered to the tibial nerve using a high-voltage constant-current stimulator (DS7AH; Digitimer, Herthfordshire, United Kingdom). The %VA was calculated for each maximal and submaximal MVC. Paired-samples t-tests were used to quantify systematic variability, whereas the intraclass correlation coefficients (ICCs), standard error of the mean (%SEM), and minimum differences (%MD; expressed as a percentage of the means) were used for test-retest reliability. Systematic variability was not present at any of the contraction intensities (p > 0.05). The ICCs ranged from 0.52 to 0.84, whereas the %SEM ranged from 6.75 to 38.45%, and the %MD ranged from 18.71 to 106.58%. The ICCs were ≥0.74 at contraction intensities ranging from 40 to 100% MVC (6.75-16.78% SEM), whereas the ICCs were ≤0.65 (20.95-38.45% SEM) for the contraction intensities ≤30% MVC. Although not statistically tested, the ICCs tended to be higher, whereas the %SEMs lower for contractions ≥40% MVC. Future research using %VA during submaximal contraction intensities to predict a true maximal force may want to exclude contraction intensities

The purpose of this study was to examine the effects of a doublet stimulus evoked during isometric submaximal contractions on the electromechanical delay (EMD). Twenty-three healthy individuals performed isometric step contractions ranging from 10 to 70% maximal voluntary contraction (MVC) with a doublet stimulus applied during the contractions. A 2-way repeated-measures analysis of variance (gender [male vs. female] x contraction intensity [10% vs. 20% vs. 30% vs. 40% vs. 50% vs. 60% vs. 70% MVC]) was used to analyze the EMD. The EMD at 10% was significantly less than at 30% (p = 0.022), 40% (p = 0.044), 50% (p = 0.012), 60% (p = 0.041), and 70% MVC (p < 0.001). In addition, the EMD at 70% MVC was significantly higher than at 20% (p = 0.002), 30% (p = 0.006), 40% (p = 0.009), and 50% MVC (p = 0.021). The EMD is the time difference between muscle activation and the onset of muscle force production, with the stretching of the series elastic component (SEC) as the major contributor. A doublet stimulus applied during an isometric contraction minimizes the effects of the SEC during the interpolated twitch technique. Therefore, when the SEC is minimized, the EMD may be lengthened because of mechanisms associated with the excitation-contraction coupling at higher contraction intensities. The EMD measurement, produced with a doublet stimulus, could potentially be a useful tool to examine the effects of fatigue, exercise, stretching, and so on, on the excitation-contraction coupling during various force levels. However, future research is needed to further elucidate the mechanisms that result in a lengthening of the EMD under these conditions

The purpose of this study was to examine the effects of dynamic stretching on the passive biomechanical properties and isometric muscle strength of the knee flexors. Fourteen healthy men (mean ± s: age = 24 ± 3 years) performed passive range of motion assessments and isometric maximal voluntary contractions of the knee flexors at knee joint angles of 35°, 50°, 65°, 80°, and 95° below full knee extension before and after dynamic stretching. In addition, electromyographic amplitude was recorded from the biceps femoris during the maximal voluntary contractions. Passive stiffness and passive resistive torque were measured during pre- and post-dynamic stretching. The dynamic stretching included the participant extending their right leg outwards to the end range motion and pulling their leg back towards the body while seated in the isokinetic dynamometer for four 30-s bouts with 20-s rest between bouts. Passive range of motion increased while passive stiffness and passive resistive torque decreased following dynamic stretching. Peak torque decreased at knee joint angles of 65° and 80° below full extension, while electromyographic amplitude decreased following dynamic stretching. Dynamic stretching resulted in changes to passive stiffness and passive resistive torque that are typically reported following static stretching, however, there were decreases in peak torque at two of the knee joint angles.

We compared starters and non-starters for various isokinetic strength variables in elite women's soccer players. A convenience sample of 10 starters (mean ± s; age = 20 ± 2 years; height = 170 ± 4 cm; body mass = 65 ± 5 kg) and 7 non-starters (age = 20 ± 1 years; height = 164 ± 3 cm; body mass = 63 ± 4 kg) performed maximal voluntary muscle actions of the leg extensors (concentric) and flexors (eccentric) on an isokinetic dynamometer in order to measure concentric peak torque for the leg extensors, eccentric peak torque for the leg flexors, and the functional hamstrings:quadriceps (H:Q) ratio at 1.047 rad · s(-1) and 4.189 rad · s(-1) concentric peak torque for the leg extensors was not different between starters and non-starters. However, it was greater at 1.047 rad · s(-1) than at 4.189 rad · s(-1) in both groups. Eccentric peak torque for the leg flexors was greater for the starters versus non-starters at 4.189 rad · s(-1). Eccentric strength of the leg flexors at fast movement velocities may be used as an effective physiological profile and may discriminate between playing status in elite women's soccer players.

Munger, CN, Archer, DC, Leyva, WD, Wong, MA, Coburn, JW, Costa, PB, and Brown, LE. Acute effects of eccentric overload on concentric front squat performance. J Strength Cond Res 31(5): 1192-1197, 2017-Eccentric overload is used to enhance performance. The purpose of this study was to investigate the acute effects of eccentric overload on concentric front squat performance. Twenty resistance-trained men (age = 23.80 ± 1.82 years, height = 176.95 ± 5.21 cm, mass = 83.49 ± 10.43 kg, 1 repetition maximum [1RM] front squat = 131.02 ± 21.32 kg) volunteered. A dynamic warm-up and warm-up sets of front squat were performed. Eccentric hooks were added to the barbell. They descended for 3 seconds, until eccentric hooks released, and performed the concentric phase as fast as possible. There were 3 randomly ordered conditions with the concentric phase always at 90% 1RM and the eccentric phase at 105, 110, and 120% of 1RM. Two repetitions were performed for each condition. A repeated measures analysis of variance was used to determine differences. For peak velocity, there were main effects for time and condition (p < 0.05), where post (1.01 ± 0.10 m·s) was greater than pre (0.96 ± 0.11 m·s) and 120% (1.03 ± 1.11 m·s) was greater than 105% (0.99 ± 0.13 m·s). For peak power, there was a main effect for condition where 120% (2,225.00 ± 432.37 W) was greater than 105% (2,021.84 ± 563.53 W). For peak ground reaction force, there were main effects for time and condition, where post was greater than pre and 120% was greater than 105%. For the rate of force development, there was no interaction or main effects. Eccentric overload enhanced concentric velocity and power; therefore, it can be used by strength coaches and athletes during the power phase of a training program. It can also be used to prescribe supramaximal loads and could be a tool to supplement the clean exercise because the front squat is a precursor.

Malyszek, KK, Harmon, RA, Dunnick, DD, Costa, PB, Coburn, JW, and Brown, LE. Comparison of olympic and hexagonal barbells with midthigh pull, deadlift, and countermovement jump. J Strength Cond Res 31(1): 140-145, 2017-Those training for strength and power commonly use different bars and different lifts. The hexagonal barbell (HBar) and Olympic barbell (OBar) are frequently used training implements, and the midthigh pull (MTP) and deadlift (DL) are 2 popular exercises. Therefore, the purpose of this study was to compare force between an HBar and OBar for a MTP, DL, and countermovement jump (CMJ). Twenty resistance-trained men (age = 24.05 ± 2.09 years, ht = 178.07 ± 7.05 cm, mass = 91.42 ± 14.44 kg) volunteered to participate and performed MTP and DL using both bars and a CMJ. Joint angles were recorded for all pulls and the bottom position of the CMJ. Peak ground reaction force (PGRF) was greater in the MTP (3,186.88 ± 543.53 N) than DL (2,501.15 ± 404.04 N) but not different between bars. Midthigh pull joint angles were more extended than DL, and the strongest correlations between isometric and dynamic performance were seen between DL PGRF and CMJ impulse (OBar r = 0.85; HBar r = 0.84). These findings are likely because of the different anatomical characteristics between the MTP and DL and the similarity in joint angles between the DL and CMJ. Therefore, the DL may be an optimal choice for athletes in jump-dependent sports, regardless of bar.

This study examined the acute effects of passive stretching on electromechanical delay (EMD), peak twitch force (PTF), rate of force development (RFD), and peak-to-peak M-wave (PPM) for the soleus muscle during evoked isometric plantar flexion muscle actions. Fourteen men (mean age ± SD = 21.2 ± 2.4 years; body mass = 80.0 ± 14.9 kg; height = 176.9 ± 7.2 cm) and 20 women (20.9 ± 2.5 years; 61.3 ± 8.9 kg; 165.3 ± 7.5 cm) volunteered for the study. Five single-square, supramaximal transcutaneous electrical stimuli (each separated by 5 s) were delivered to the tibial nerve before and after passive stretching. A time × gender interaction was observed for EMD, and the post hoc dependent-samples t tests indicated that EMD increased 4% for the women (p = .023), but not for the men (p = .191). There were no other stretching-related changes for PTF, RFD, or p-p M-wave for either the men or women (p > .05). These findings tentatively suggested that mechanical factors related to the stiffness of the muscle-tendon unit may contribute to the explanation for why stretching caused an acute increase in the EMD during evoked twitches in the women, but not in the men.

The purpose of this study was to examine the acute effects of 3 different stretching methods combined with a warm-up protocol on vertical jump performance. Sixteen young tennis players (14.5 ± 2.8 years; 175 ± 5.6 cm; 64.0 ± 11.1 kg) were randomly assigned to 4 different experimental conditions on 4 successive days. Each session consisted of a general and specific warm-up, with 5 minutes of running followed by 10 jumps, accompanied by one of the subsequent conditions: (a) Control Condition (CC)-5 minutes of passive rest; (b) Passive Stretching Condition (PSC)-5 minutes of passive static stretching; (c) Active Stretching Condition (ASC)-5 minutes of active static stretching; and (d) Dynamic Stretching Condition (DC)-5 minutes of dynamic stretching. After each intervention, the subjects performed 3 squat jumps (SJs) and 3 countermovement jumps (CMJs), which were measured electronically. For the SJ, 1-way repeated measures analysis of variance (CC × PSC × ASC × DC) revealed significant decreases for ASC (28.7 ± 4.7 cm; p = 0.01) and PSC (28.7 ± 4.3 cm; p = 0.02) conditions when compared with CC (29.9 ± 5.0 cm). For CMJs, there were no significant decreases (p > 0.05) when all stretching conditions were compared with the CC. Significant increases in SJ performance were observed when comparing the DC (29.6 ± 4.9 cm; p = 0.02) with PSC (28.7 ± 4.3 cm). Significant increases in CMJ performance were observed when comparing the conditions ASC (34.0 ± 6.0 cm; p = 0.04) and DC (33.7 ± 5.5 cm; p = 0.03) with PSC (32.6 ± 5.5 cm). A dynamic stretching intervention appears to be more suitable for use as part of a warm-up in young athletes.

The purpose of the present study was to examine the time course of passive range of motion (PROM), passive torque (PASTQ), and musculo-tendinous stiffness (MTS) responses during constant-angle (CA) and constant-torque (CT) stretching of the leg flexors. Eleven healthy men [mean ± standard deviation (SD): age = 21.5 ± 2.3 years] performed 16 30-s bouts of CA and CT stretching of the leg flexors. PROM, PASTQ , and MTS were measured during stretches 1, 2, 4, 8, and 16. For PROM and PASTQ , there were no differences between CA and CT stretching treatments (P > 0.05); however, there were stretch-related differences (P < 0.001). PROM increased following one 30-s bout of stretching (collapsed across CA and CT stretching) with additional increases up to 8 min of stretching. PASTQ decreased following one 30-s bout of stretching (collapsed across CA and CT stretching) and continued to decrease up to 4 min of stretching. In contrast, only the CT stretching treatment resulted in changes to MTS (P < 0.001). MTS decreased after one 30-s bout of CT stretching, with subsequent decreases in MTS up to 6 min of stretching. These results suggested that CT stretching may be more appropriate than a stretch held at a constant muscle length for decreasing MTS.

Recent evidence has shown acute static stretching may decrease hamstring-to-quadriceps (H:Q) ratios. However, the effects of static stretching on the functional H:Q ratio, which uses eccentric hamstrings muscle actions, have not been investigated. This study examined the acute effects of hamstrings and quadriceps static stretching on leg extensor and flexor concentric peak torque (PT), leg flexor eccentric PT, and the conventional and functional H:Q ratios. Twenty-two women (mean ± SD age=20.6 ± 1.9 years; body mass=64.6 ± 9.1 kg; height=164.5 ± 6.4 cm) performed three maximal voluntary unilateral isokinetic leg extension, flexion, and eccentric hamstring muscle actions at the angular velocities of 60 and 180°/s before and after a bout of hamstrings, quadriceps, and combined hamstrings and quadriceps static stretching, and a control condition. Two-way repeated measures ANOVAs (time × condition) were used to analyze the leg extension, flexion, and eccentric PT as well as the conventional and functional H:Q ratios. Results indicated that when collapsed across velocity, hamstrings-only stretching decreased the conventional ratios (P

The present study examined the viscoelastic creep responses in vivo during repeated constant-torque stretches in human skeletal muscle. Twelve healthy participants completed four consecutive 30-s constant-torque passive stretches of the right plantar flexor muscles. Position and surface electromyographic (EMG) amplitude values were quantified at every 5-s period and the percent change in position was quantified for each 5-s epoch relative to the total increase in ankle joint position for each stretch. In addition, the absolute changes in position were plotted on a logarithmic time scale and fit with a linear regression line to examine both the rate of increase (slope) and the overall increase in position over the entire stretch (y-intercept). The percent change and slope were similar (P>0.05) over all four stretches, with the majority of increases in position occurring within the initial 15-20 s of each stretch (84%). Absolute ankle joint position and the y-intercept increased (P 0.05) after the third stretch. In addition, EMG amplitude values did not change (P>0.05) during or between each 30-s stretch. These data indicate that the amount and rate of viscoelastic creep were similar during practical durations of constant-torque stretching despite no change in ankle joint position following three 30-s stretches.

The purpose of the present study was to examine musculotendinous stiffness (MTS) and ankle joint range of motion (ROM) in men and women after an acute bout of passive stretching. Thirteen men (mean ± SD age = 21 ± 2 years; body mass = 79 ± 15 kg; and height = 177 ± 7 cm) and 19 women (21 ± 3 years; 61 ± 9 kg; 165 ± 8 cm) completed stretch tolerance tests to determine MTS and ROM before and after a stretching protocol that consisted of 9 repetitions of passive, constant-torque stretching. The women were all tested during menses. Each repetition was held for 135 seconds. The results indicated that ROM increased after the stretching for the women (means ± SD pre to post: 109.39° ± 10.16° to 116.63° ± 9.63°; p ≤ 0.05) but not for the men (111.79° ± 6.84° to 113.93° ± 8.15°; p > 0.05). There were no stretching-induced changes in MTS (women's pre to postchange in MTS: -0.35 ± 0.38; men's MTS: +0.17 ± 0.40; p > 0.05), but MTS was higher for the men than for the women (MTS: 1.34 ± 0.41 vs. 0.97 ± 0.38; p ≤ 0.05). electromyographic amplitude for the soleus and medial gastrocnemius during the stretching tests was unchanged from pre to poststretching (p > 0.05); however, it increased with joint angle during the passive movements (p ≤ 0.05). Passively stretching the calf muscles increased stretch tolerance in women but not in men. But the stretching may not have affected the viscoelastic properties of the muscles. Practitioners may want to consider the possible gender differences in passive stretching responses and that increases in ROM may not always reflect decreases in MTS.

It is generally recommended that exercises involving large muscle groups be placed at the beginning of a training session. However, methodological training studies manipulating exercise order and the investigation of its influence on strength have not been conducted. Therefore, the purpose of this study was to examine the influence of exercise order on strength in untrained young men after 8 weeks of training. Prior to the training program, participants were randomly assigned to three groups. One group began with large and progressed toward small muscle group exercises (G1) while another performed the opposite order (G2). The third group did not exercise and served as a control (CG). Training frequency was three sessions per week with at least 48h of rest between sessions for a total of 24 sessions in the 8-week period. One repetition maximum (1RM) was assessed for all exercises at baseline and after 8 weeks of training. Both G1 and G2 resulted in significant increases of 16.3-77.8% in 1RM compared to baseline (p