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Introduction: Large increases in joint range of motion (ROM) have been reported after eccentric resistance training; however, limited data exist describing the associated mechanisms or potential cross-education effects in the contralateral limb. Therefore, the effects of a 6-wk isokinetic eccentric plantarflexor training program were examined in 26 participants. Methods: Before and after the training program, dorsiflexion ROM, plantarflexor strength, and muscle-tendon unit (MTU) morphology and mechanics were measured in control (n = 13) and experimental (n = 13) young adult groups. Training consisted of 5 sets of 12 maximal isokinetic eccentric plantarflexor contractions twice weekly on the right limb. Results: Significant ( P < 0.05) increases in dorsiflexion ROM (4.0-9.5°), stretch tolerance (40.3-95.9%), passive elastic energy storage (47.5-161.3%), and isometric (38.1-40.6%) and eccentric (46.7-67.0%) peak plantarflexor torques were detected in both trained and contralateral limbs in the experimental group. Significant increases in gastrocnemiusmedialis and soleus thickness (5.4-6.1%), gastrocnemius medialis fascicle length (7.6 ± 8.5%), passive plantarflexor MTU stiffness (30.1 ± 35.5%), and Achilles tendon stiffness (5.3 ± 4.9%) were observed in the trained limb only. Significant correlations were detected between the changes in trained and contralateral limbs for dorsiflexion ROM (r = 0.59) and both isometric (r = 0.79) and eccentric (r = 0.73) peak torques. No significant changes in any metric were detected in the control group. Conclusions: Large ROM increases in the trained limb were associated with neurological, mechanical, and structural adaptations, with evidence of a cross-education effect in the contralateral limb being primarily driven by neurological adaptation (stretch tolerance). The large improvements in ROM, muscle size, and strength confirm that isokinetic eccentric training is a highly effective training tool, with potential for use in athletic and clinical populations where MTU function is impaired and current therapies are ineffective. [ABSTRACT FROM AUTHOR]

Different methods can be used to assess muscle hypertrophy, but the effects of training on regional changes in muscle size can be detected only using direct muscle measurements such as muscle thickness, cross-sectional area, or volume. Importantly, muscle size increases vary across regions within and between muscles after resistance training programs (i.e., heterogeneous, or nonuniform, muscle hypertrophy). Muscle architectural changes, including fascicle length and pennation angle, after resistance and stretch training programs are also region-specific. In this paper, we show that the literature indicates that a single-site measure of muscle shape does not properly capture the effects achieved after exercise training interventions and that conclusions concerning the magnitude of muscle adaptations can vary substantially depending on the muscle site to be examined. Thus, we propose that measurements of muscle size and architecture should be completed at multiple sites across regions between the agonist muscles within a muscle group and along the length of the muscles to provide an adequate picture of training effects. [ABSTRACT FROM AUTHOR]

The aim of this study was to examine the concurrent effects of maturity status and recovery delay after a standardized dynamic warm-up on vertical jump performance. Thirteen prepubertal boys (9.4 ± 1.1 years) and 12 postpubertal boys (16.6 ± 0.8 years) were tested on squat jump (SJ) and drop jump from 30 cm (DJ30) before and after a standardized, 8-minute, dynamic warm-up, including low-intensity, nonspecific dynamic exercises progressing to maximal, specific exercises, over 6 separate occasions. In each session, subjects jumped at 0, 1.5, 3, 5, 7, or 10 minutes after warm-up in a randomized order. Measurements included SJ height, DJ30 height, ground contact time (GCT), and reactive strength index (RSI) from DJ30. The results revealed no significant recovery time x maturity group interaction effects for SJ height (p = 0.36), DJ30 height (p = 0.45), GCT (p = 0.75), or RSI (p = 0.09), meaning that maturity status did not have a significant effect on changes in vertical jump performance after the warm-up. However, there were significant time effects for SJ height, DJ30 height, and RSI (p < 0.001 for all), with DJ30 height and RSI increasing significantly by 16.9% at 1.5 minutes (p < 0.001) and SJ height increasing significantly by 12.0% until 3 minutes after the warm-up (p < 0.001). To conclude, the standardized dynamic warm-up had beneficial effects on vertical jump performance within the first 3 minutes after completion of the intervention. However, vertical jump performance after the warm-up was not dependent on the children's maturity status. [ABSTRACT FROM AUTHOR]

Dunn, EC, Humberstone, CE, Franchini, E, Iredale, KF, and Blazevich, AJ. Relationships between punch impact force and upper- and lower-body muscular strength and power in highly trained amateur boxers. J Strength Cond Res 36(4): 1019-1025, 2022-This study examined the relationship between upper- and lower-body strength and power characteristics and punch performance in 28 highly trained male amateur boxers. Punch performance was assessed with a custom-built punch integrator using a 3-minute maximal effort punch test that contained straight- and bent-arm punches from the lead and rear hands. Peak punch force and force-time variables including impulse and rate of force development (RFD; calculated to various points) were assessed. Force, power, and RFD of the upper and lower body were assessed with countermovement bench throw, isometric bench push, countermovement jump (CMJ), and isometric midthigh pull (IMTP) tests. Correlation and regression analyses revealed significant (p < 0.05) relationships between peak punch force and forces measured in CMJ and IMTP tests. In addition, peak punch force was moderately and significantly correlated to body mass, but RFD in the lower body was not. Moreover, no meaningful relationships between punch performance characteristics and any upper-body strength or power parameter were identified. The results of this study show that lower-body strength but not RFD had a moderate to strong positive and significant correlation to peak punch force production. Although upper-body strength and power are expected to be important in boxing, they did not discriminate between boxers who punched with higher or lower peak force nor were they correlated to peak punch force. Training that improves lower-body strength without increasing total body mass (to maintain weight category) may positively influence punch capacity in highly trained amateur boxers. [ABSTRACT FROM AUTHOR]

Neuromuscular electrical stimulation (NMES) applied to skeletal muscles is an effective rehabilitation and exercise training modality. However, the relatively low muscle force and rapid muscle fatigue induced by NMES limit the stimulus provided to the neuromuscular system and subsequent adaptations. We hypothesize that adaptations to NMES will be enhanced by the use of specific stimulation protocols and adjuvant interventions. [ABSTRACT FROM AUTHOR]

While increased lower-limb force production during kayaking has been shown to be related to increased boat velocity, poor relationships between maximal deadlift test performances and 200-m race time have been observed previously. This discrepancy may result from either a lack of movement pattern or temporal force production specificity between the test and kayak paddling. The isometric midthigh pull (MTP) test is commonly used in strength testing and quantifies temporal and peak force production, with the lower limbs positioned in a more kayak-specific manner than the deadlift test. Midthigh pull force data collected from 11 high-level kayak athletes were analyzed for both reliability and correlations with 200-m race time and deadlift isoinertial strength 3 repetition maximum (3RM). Strong consideration was given to the collection, processing, and analysis of the MTP data, which markedly affected the study results. Correlations between race time and MTP peak force and rates of force development were poor to moderate (r = −0.49 to 0.07). Strong to very strong relationships (r = 0.66–0.79) were found between forces developed early in the MTP (<0.15 seconds) and deadlift 3RM strength tests but were poor for later time-specific force development (r ≤ 0.12). However, poor reliability was found for force measured up to ≤0.25 seconds from the point of force onset (intraclass correlation coefficient >0.8). Owing to the relatively weak relationships with 200-m race time, and the large variability of the data, it may not be wise to include the MTP in the testing and training of 200-m kayak athletes. [ABSTRACT FROM AUTHOR]

One of the best strategies for healthy brain aging is regular aerobic exercise. Commonly studied "anti-aging" compounds may mimic some effects of exercise on the brain, but novel approaches that target energy-sensing pathways similar to exercise probably will be more effective in this context. We review evidence in support of this hypothesis by focusing on biological hallmarks of brain aging. [ABSTRACT FROM AUTHOR]

Supplemental digital content is available in the text. Purpose: Resistance exercise increases blood flow, induces osmotic and hydrostatic fluid shifts during and immediately after exercise, and may trigger inflammatory responses for several days in the working muscle. The resultant muscle swelling can subsequently affect muscle size and quality assessments. However, the effects of muscle swelling on x-ray attenuation of adipose estimate errors are unknown. Methods: Peripheral quantitative computed tomography (pQCT) and ultrasonography were used to assess muscle and adipose tissue properties of both upper arms before, 24, 48, and 72 h after unilateral resistance exercise. Recreationally active participants (n = 17) completed the exercise while their contralateral limb served as a control. Results: Resistance exercise resulted in a significant increase in pQCT-derived muscle cross-sectional area (includes intermuscular adipose tissue [IMAT] area), muscle area (excludes IMAT area) and IMAT area, and ultrasound-derived muscle thickness at 24, 48, and 72 h. A significant decrease in pQCT-derived muscle density was also detected as well as an increase in ultrasound-derived echo intensity at 48 and 72 h. The changes in muscle area, IMAT area, and muscle density were significantly correlated with changes in echo intensity, whereas the changes in muscle cross-sectional area and IMAT area were significantly correlated with changes in muscle thickness. Conclusion: Unaccustomed resistance exercise can cause errors in pQCT- and ultrasound-based muscle and adipose estimates for at least 72 h. These errors are the result of muscle swelling likely caused by muscle blood flow and inflammation-dependent fluid shifts in muscle. These findings may have implications for measurements in other inflammatory conditions. [ABSTRACT FROM AUTHOR]

Supplemental digital content is available in the text. Purpose: To assess the repeatability of, and measurement agreement between, four sonographic techniques used to quantify biceps femoris long head (BFlh) architecture: (i) static-image with linear extrapolation; extended field-of-view (EFOV) with linear ultrasound probe path (linear-EFOV), using either (ii) straight or (iii) segmented analyses; and (iv) EFOV with nonlinear probe path and segmented analysis (nonlinear-EFOV) to follow the complex fascicle trajectories. Methods: Twenty individuals (24.4 ± 5.7 yr; 175 ± 0.8 cm; 73 ± 9.0 kg) without history of hamstrings strain injury were tested in two sessions separated by 1 h. An ultrasound scanner coupled with 6-cm linear probe was used to assess BFlh architecture in B-mode. Results: The ultrasound probe was positioned at 52.0% ± 5.0% of femur length and 57.0% ± 6.0% of BFlh length. We found an acceptable repeatability when assessing BFlh fascicle length (ICC3,k = 0.86–0.95; SEM = 1.9–3.2 mm) and angle (ICC3,k = 0.86–0.97; SEM = 0.8°–1.1o) using all sonographic techniques. However, the nonlinear-EFOV technique showed the highest repeatability (fascicle length ICC3,k = 0.95; fascicle angle, ICC3,k = 0.97). The static-image technique, which estimated 35.4% ± 7.0% of the fascicle length, overestimated fascicle length (8%–11%) and underestimated fascicle angle (8%–9%) compared with EFOV techniques. Also, the rank order of individuals varied by approximately 15% between static-image and nonlinear-EFOV (segmented) when assessing the fascicle length. Conclusions: Although all techniques showed good repeatability, absolute errors were observed using static-image (7.9 ± 6.1 mm for fascicle length) and linear-EFOV (between 3.7 ± 3.0 and 4.2 ± 3.7 mm), probably because the complex fascicle trajectories were not followed. The rank order of individuals for fascicle length and angle were also different between static-image and nonlinear-EFOV, so different muscle function and injury risk estimates could likely be made when using this technique. [ABSTRACT FROM AUTHOR]

Introduction: Muscle force production is usually impaired in people with spinal cord injury (SCI). The use of high-intensity neuromuscular electrical stimulation (NMES) strength training can help promote metabolically active lean muscle mass and, thus, increase muscle mass and improve physical health and quality of life (QoL). Nonetheless, NMES is usually used at low-stimulation intensities, and there is limited evidence on the effects of high-intensity NMES strength training into improving muscle force and mass, symptoms of spasticity, or physical health and QoL in people with SCI. Methods: Five individuals with chronic SCI completed five 10-repetition sets of high-intensity knee extension NMES strength training sessions for 12 wk in both quadriceps muscles. Quadriceps femoris (QF) knee extensor torque was measured on a dynamometer, and cross-sectional area (CSAQF) was measured with extended field-of-view ultrasonography. Venous blood samples were collected for blood lipid profiling and C-reactive protein analyses. The Spinal Cord Injury Spasticity Evaluation Tool was used to assess symptoms of spasticity, and the QoL index SCI version III was used for QoL measures. Results: QF tetanic knee extensor torque increased on average by 35% (2%–92%), and CSAQF increased by 47% (14%–145%). A significant increase in the HDL/LDL cholesterol ratio (P < 0.001) and a mean significant improvement of 4.8% ± 2.3% (absolute value = 0.26) in the Spinal Cord Injury Spasticity Evaluation Tool score was observed, whereas QoL showed a near-significant improvement in the health and functioning domain (15.0 ± 4.2 and 17.3 ± 5.1; P = 0.07). Conclusions: High-intensity NMES strength training in people with SCI may improve muscle strength, mass, physical health, and QoL. However, replication of these results is necessary before clinical implementation. [ABSTRACT FROM AUTHOR]

Supplemental digital content is available in the text. Purpose: This study aimed to examine the effects of static and dynamic stretching routines performed as part of a comprehensive warm-up on flexibility and sprint running, jumping, and change of direction tests in team sport athletes. Methods: A randomized, controlled, crossover study design with experimenter blinding was conducted. On separate days, 20 male team sport athletes completed a comprehensive warm-up routine. After a low-intensity warm-up, a 5-s static stretch (5S), a 30-s static stretch (30S; 3 × 10-s stretches), a 5-repetition (per muscle group) dynamic stretch (DYN), or a no-stretch (NS) protocol was completed; stretches were done on seven lower body and two upper body regions. This was followed by test-specific practice progressing to maximum intensity. A comprehensive test battery assessing intervention effect expectations as well as flexibility, vertical jump, sprint running, and change of direction outcomes was then completed in a random order. Results: There were no effects of stretch condition on test performances. Before the study, 18/20 participants nominated DYN as the most likely to improve performance and 15/20 nominated NS as least likely. Immediately before testing, NS was rated less “effective” (4.0 ± 2.2 on a 10-point scale) than 5S, 30S, and DYN (5.3–6.4). Nonetheless, these ratings were not related to test performances. Conclusion: Participants felt they were more likely to perform well when stretching was performed as part of the warm-up, irrespective of stretch type. However, no effect of muscle stretching was observed on flexibility and physical function compared with no stretching. On the basis of the current evidence, the inclusion of short durations of either static or dynamic stretching is unlikely to affect sprint running, jumping, or change of direction performance when performed as part of a comprehensive physical preparation routine. [ABSTRACT FROM AUTHOR]

The article presents a study to compare the results of effects of compound and complex resistance training on several physiological factors among healthy men including performance of high-speed movement, strength and composition of the muscles. Several exercises that young men performed includes bench press, machine box squats and jumping exercises.

A single bout of eccentric exercise confers a protective effect against muscle damage and soreness in subsequent eccentric exercise bouts, but the mechanisms underpinning this effect are unclear. Purpose: This study compared vastus lateralis (VL) muscle-tendon behavior between two eccentric cycling bouts to test the hypothesis that muscle-tendon behavior would be different between bouts andwould be associated with the protective effect. Methods: Eleven untrained men (27.1 ± 7.0 yr) performed two bouts of eccentric cycling (ECC1 and ECC2) separated by 2 wk for 10 min at 65% of maximal concentric workload (191.9 ± 44.2 W) each. Muscle soreness (by visual analog scale) and maximal voluntary isometric contraction (MVC) torque of the knee extensors were assessed before and 1-2 d after exercise. Using ultrasonography, VL fascicle length and angle changes during cycling were assessed, and tendinous tissue (TT) length changes were estimated. VL EMG amplitude, crank torque, and knee joint angles were measured during cycling. Results: Soreness was greater (P G 0.0001) after ECC1 than ECC2, although MVC changes were not different between bouts (P = 0.47). No significant differences in peak EMG amplitude (normalized to EMG during MVC), crank peak torque, or knee angleswere evident between bouts. However, fascicle elongation was 16%less during ECC2 than ECC1 (P G 0.01), indicating less fascicle strain in ECC2. Maximum TT length occurred at a smaller knee joint angle during ECC2 than ECC1 (P = 0.055). Conclusion: These results suggest that a lesser fascicle elongation and earlier TT elongation were associated with reduced muscle soreness after ECC2 than ECC1; thus, changes in muscle-tendon behavior may be an important mechanism underpinning the protective effect. [ABSTRACT FROM AUTHOR]

The article discusses research which was conducted to investigate differences in the effects a 30 second and 60 second period of static muscle stretching had on vertical jump performance and power output. Researchers evaluated both stretching routines in 16 male subjects. They found that 60 second stretching resulted in a lower jump height and peak power output and that the effect of a 30 second stretching routine had negligible effects.

The article discusses research which was conducted to investigate the effect variable resistance exercise conducted during a warm up routine had on free weight resistance maximal squat performance. Researchers evaluated 16 recreationally active men between the ages of 26 and 33. They found that variable resistance exercise during warm up potentiated the neuromuscular system and enhanced maximal squat lifting performance.

Purpose: Eccentric cycling is an exercise modality that could elicit multiple health benefits with low metabolic cost, but unaccustomed performance results in significant muscle damage. It is not known whether muscle damage is attenuated when eccentric cycling is repeated; thus, this study compared metabolic and muscle damage responses to concentric (CONC) and two consecutive eccentric (ECC1 and ECC2) cycling bouts. Methods: Ten men (28 ± 8 yr) performed each cycling bout for 30 min at 60% of the maximal concentric power output at 60 rpm, with 2 wk between bouts. HR, oxygen consumption (V⋅O2), blood lactate (BLa), RPE, and muscle activity (EMG) data were collected during cycling. Maximal voluntary isometric knee extensor (MVC) strength, squat (SJ), countermovement jump (CMJ) height, muscle soreness indicators, and plasma creatine kinase (CK) activity were measured before, immediately after, and 1-4 d after exercise. Results: Average HR, V⋅O2, BLa, and RPE were lower (P < 0.05) during ECC1 than CONC, and EMG amplitude was also lower during ECC1 than CONC. Decreases in MVC, CMJ, and SJ and the increase in muscle soreness were greater (P x0003C; 0.05) after ECC1 than CONC. Increases in creatine kinase were minimal after all bouts. When comparing ECC1 and ECC2, HR and BLa were lower (P < 0.05) during ECC2 than ECC1, and decreases in MVC, CMJ, and SJ and the increase in muscle soreness were greater (P < 0.05) after ECC1 than ECC2. After ECC2, MVC, CMJ, and SJ did not change and no muscle soreness was developed. Conclusions: Eccentric cycling was less metabolically demanding than concentric cycling, and HR and BLa were further reduced during ECC2. Muscle damage is minimal after ECC2 and should not influence the choice to undertake eccentric cycling training. [ABSTRACT FROM AUTHOR]

The article reports on research which was conducted to investigate the effect acute static stretching had on maximal muscle performance. Researchers performed a database search and evaluated 106 articles related to static stretch and muscle performance. They found that the detrimental effects of static stretch are mainly limited to longer durations (>60 s), which may not be typically used during preexereise routines in clinical, healthy, or athletic populations. They concluded that shorter durations of stretch (<60 s) can be performed in a preexercise routine without compromising maximal muscle performance.

Alcaraz, PE, Perez-Gomez, J, Chavarrias, M, and Blazevich, AJ. Similarity in adaptations to high-resistance circuit vs. traditional strength training in resistance-trained men. J Strength Cond Res 25(9): 2519-2527, 2011-To compare the effects of 8 weeks of high-resistance circuit (HRC) training (3-6 sets of 6 exercises, 6 repetition maximum [RM], ~35-second interset recovery) and traditional strength (TS) training (3-6 sets of 6 exercises, 6RM, 3-minute interset recovery) on physical performance parameters and body composition, 33 healthy men were randomly assigned to HRC, TS, or a control group. Training consisted of weight lifting 3 times a week for 8 weeks. Before and after the training, 1RM strength on bench press and half squat exercises, bench press peak power output, and body composition (dual x-ray absorptiometry ) were determined. Shuttle run and 30-second Wingate tests were also completed. Upper limb (UL) and lower limb 1RM increased equally after both TS and HRC training. The UL peak power at various loads was significantly higher at posttraining for both groups (p <= 0.01). Shuttle-run performance was significantly better after both HRC and TS training, however peak cycling power increased only in TS training (p <= 0.05). Significant decreases were found in % body fat in the HRC group only; HRC and TS training both resulted in an increased lean but not bone mass. The HRC training was as effective as TS for improving weight lifting 1RM and peak power, shuttle-run performance and lean mass. Thus, HRC training promoted a similar strength-mass adaptation as traditional training while using a shorter training session duration. [ABSTRACT FROM AUTHOR]

The article compared physical performance parameters and cardiovascular load during heavy-resistance circuit training to the responses during a traditional, passive rest strength training set. The data confirmed that the maximum and average bar velocity and power and the number of repetitions was the same. The average heart rate was greater in the heavy-resistance circuit compared to the training set.

This study examined the effect of contrast water therapy (CWT) on the physiological and functional symptoms of delayed onset muscle soreness (DOMS) following DOMS-inducing leg press exercise. Thirteen recreational athletes performed 2 experimental trials separated by 6 weeks in a randomized crossover design. On each occasion, subjects performed a DOMS-inducing leg press protocol consisting of 5 X 10 eccentric contractions (180 seconds recovery between sets) at 140% of 1 repetition maximum (1RM). This was followed by a 15-minute recovery period incorporating either CWT or no intervention, passive recovery (PAS). Creatine kinase concentration (CK), perceived pain, thigh volume, isometric squat strength, and weighted jump squat performance were measured prior to the eccentric exercise, immediately post recovery, and 24, 48, and 72 hours post recovery. Isometric force production was not reduced below baseline measures throughout the 72-hour data collection period following CWT (∼4-10%). However, following PAS, isometric force production (mean ± SD) was 14.8 ± 11.4% below baseline immediately post recovery (p > 0.05), 20.8 ± 15.6% 24 hours post recovery (p > 0.05), and 22.5 ± 12.3% 48 hours post recovery (p > 0.05). Peak power produced during the jump squat was significantly reduced (p > 0.05) following both PAS (20.9 ± 13.4%) and CWT (12.8 ± 8.0%), with the mean reduction in power for PAS being marginally (not significantly) greater than for CWT (effect size = 0.76). Thigh volume measured immediately following CWT was significantly less than PAS. No significant differences in the changes in CK were found; in addition, there were no significant (p > 0.01) differences in perceived pain between treatments. Contrast water therapy was associated with a smaller reduction, and faster restoration, of strength and power measured by isometric force and jump squat production following DOMS-inducing leg press exercise when compared to PAS. Therefore, CWT seems to be effective in reducing and improving the recovery of functional deficiencies that result from DOMS, as opposed to passive recovery. [ABSTRACT FROM AUTHOR]

To better understand the reliability of unfamiliar multijoint strength tests, 16 resistance-trained men performed maximum velocity uni- (1 leg [1L]) and bilateral (2 legs [2L]) lifts on an unfamiliar semiprone leg squat machine with loads equivalent to 40 and 70% of maximum isometric force on 2 separate occasions. Peak force was highly reproducible between testing occasions at the heavy load under both uni- and bilateral conditions (intraclass correlation coefficient [ICC]1L70% = 0.91, ICC2L70% = 0.92), was slightly reduced in the light load bilateral condition (ICC2L40% = 0.85), and was significantly (p < 0.05) reduced in the light load unilateral condition (ICC1L40% = 0.57). Test reliability was not related to total load lifted (2L 70% > 1L 70% > 2L 40% > 1L 40%) or to the peak force developed during the tests (2L 70% > 1L 70% 5 2L 40% > 1L 40%), but it was somewhat related to the time taken to attain peak force (2L 70% = 1L 70% > 2L 40% > 1L 40%). To obtain reliable strength data from athletes, more familiarization seems to be needed when they perform modified versions of common multijoint strength tests, or unfamiliar strength tests, under light load, unilateral conditions. The marked differences in reliability resulting from variation in loading conditions suggests that the reliability of a test needs to be reestablished when it is modified, before it is used to assess athlete/subject strength performance. [ABSTRACT FROM AUTHOR]

This study examined the effects of supplementation with either creatine monohydrate powder in solution (CP) or a widely available creatine serum (CS) on performance in a repeated maximal sprint cycling test (10 X 6 seconds, 24-second passive rest between sprints). Using a randomized, double-blind, crossover design, 11 competitive male athletes supplemented with creatine in 2 forms according to the manufacturer's recommendations on 2 separate occasions. The 2 supplementation protocols were (a) 20 g-day-1 X 6 days of creatine powder in solution plus a placebo serum (CP) or (b) 5 ml-day-1 X 6 days of creatine serum plus a placebo powder (CS). Subjects completed 2 familiarization trials before the 6-day supplementation period. A repeated maximal sprint cycling test was performed prior to and immediately postsupplementation. A 7-week washout period separated the 2 supplementation protocols. Subjects' total work (9.6%) and peak power (3.4%) in the cycle sprint improved significantly (p < 0.05) after loading with CP, but there was little change after loading with CS. The present data support previous research findings showing an ergo-genic effect of CP supplementation but indicate that supplementation with CS does not affect sprint cycling performance. Although the levels of creatine in each formulation were not determined, a substantial conversion of creatine into creatinine has been reported in many formulations and may explain the present findings. [ABSTRACT FROM AUTHOR]

Purpose: Recently, it has been suggested that a cellular pathway composed of integrin, integrin-linked kinase (ILK), rapamycin-insensitive companion of mTOR (RICTOR), and Akt may facilitate long-term structural and functional adaptations associated with exercise, independent of the mTORC1 pathway. Therefore, we examined changes in integrin-ILK-RICTOR-Akt protein in vastus lateralis (VL) before and after 8 wk of eccentric cycling training (ECC), which was expected to increase muscle function and VL cross-sectional area (CSA)., Methods: Eleven men (23 ± 4 yr) completed 24 sessions of ECC with progressive increases in intensity and duration, resulting in a twofold increase in work from the first three (75.4 ± 14.1 kJ) to the last three sessions (150.7 ± 28.4 kJ). Outcome measures included lower limb lean mass, VL CSA, static strength, and peak and average cycling power output. These measures and VL samples were taken before and 4-5 d after the last training session., Results: Significant (P < 0.05) increases in integrin-β1 (1.64-fold) and RICTOR (2.99-fold) protein as well as the phosphorylated-to-total ILK ratio (1.70-fold) were found, but integrin-α7 and Akt did not change. Increases in lower limb, thigh, and trunk lean mass (2.8%-5.3%, P < 0.05) and CSA (13.3% ± 9.0%, P < 0.001) were observed. Static strength (18.1% ± 10.8%) and both peak (8.6% ± 10.5%) and average power output (7.4% ± 8.3%) also increased (P < 0.05). However, no significant correlations were found between the magnitude of increases in protein and the magnitude of increases in CSA, static strength, or power output., Conclusions: In addition to increased muscle mass, strength, and power, we demonstrate that ECC increases integrin-β1 and RICTOR total protein and p-ILK/t-ILK, which may play a role in protection against muscle damage as well as anabolic signaling to induce muscle adaptations., (Copyright © 2021 by the American College of Sports Medicine.)

Prolonged static muscle stretching transiently reduces maximal muscle force, and this force loss has a strong neural component. In this review, we discuss the evidence suggesting that stretching reduces the motoneuron's ability to amplify excitatory drive. We propose a hypothetical model in which stretching causes physiological relaxation, reducing the brainstem-derived neuromodulatory drive necessary to maximize motoneuron discharge rates., (Copyright © 2021 by the American College of Sports Medicine.)

Purpose: This study examined changes in the muscle size, muscle architecture, strength, and sprint/jump performances of concurrently training athletes during 5 wk of "altered" resistance training (RT)., Methods: Eight female and 15 male athletes performed 4 wk of sprint, jump, and resistance training in addition to their sports training (standardization) before adopting one of three different programs for 5 wk: 1) squat lift training (SQ, N = 8) with sprint/jump training; 2) forward hack squat training (FHS, N = 7) with sprint/jump training; or 3) sprint/jump training only (SJ, N = 8). Muscle size, fascicle angle, and fascicle length of the vastus lateralis (VL) and rectus femoris (RF) muscles (using ultrasound procedures) as well as 20-m sprint run, vertical jump, and strength performance changes were examined., Results: A small increase in VL fascicle angle in SQ and FHS was statistically different to the decrease in SJ subjects (P < 0.05 at distal, P < 0.1 at proximal). VL fascicle length increased for SJ only (P < 0.05 at distal, P < 0.1 at proximal) and increased in RF in SQ subjects (P < 0.05). Muscle thickness of VL and RF increased in all training groups (P < 0.05) but only at proximal sites. There were no between-group differences in squat, forward hack squat, or isokinetic strength performances, or in sprint or jump performances, despite improvements in some of the tests across the groups., Conclusions: Significant muscle size and architectural adaptations can occur in concurrently training athletes in response to a 5-wk training program. These adaptations were possibly associated with the force and velocity characteristics of the training exercises but not the movement patterns. Factors other than, or in addition to, muscle architecture must mediate changes in strength, sprint, and jump performance.