Muscular hypertrophy depends on metabolic exhaustion as well as mechanical load on the muscle. Mechanical tension seems to be the crucial factor to stimulate protein synthesis. The present meta-analysis was conducted to determine whether stretching can generate adequate mechanical tension to induce muscle hypertrophy. We used PubMed, Web of Science, and Scopus to search for literature examining the effects of long-term stretching on muscle mass, muscle cross-sectional area, fiber cross-sectional area, and fiber number. Since there was no sufficient number of studies investigating long-lasting stretching in humans, we only included original animal studies in the current meta-analysis. Precisely, we identified 16 studies meeting the inclusion criteria (e. g. stretching of at least 15 min per day). The 16 studies yielded 39 data points for muscle mass, 11 data points for muscle cross-sectional area, 20 data points for fiber cross-sectional area, and 10 data points for fiber number. Across all designs and categories, statistically significant increases were found for muscle mass (d = 8.51; 95% CI 7.11–9.91), muscle cross-sectional area (d = 7.91; 95% CI 5.75–10.08), fiber cross-sectional area (d = 5.81; 95% CI 4.32–7.31), and fiber number (d = 4.62; 95% CI 2.54–6.71). The findings show an (almost) continuous positive effect of long-term stretching on the listed parameters, so that it can be assumed that stretch training with adequate intensity and duration leads to hypertrophy and hyperplasia, at least in animal studies. A general transferability to humans—certainly with limited effectiveness—can be hypothesized but requires further research and training studies.
This study compared the effects of offset loading (OSL) versus traditional loading (TDL) in the bench press exercise on pectoral muscle thickness and bench press strength over a 4-week mesocycle. Methods: Twenty male participants aged 18–45 years with at least 5 years of bench press experience and a bench press one-repetition maximum equal to or greater than their body mass were randomly assigned to OSL and TDL groups. Before and after the 4-week mesocycle, pectoral muscle thickness was assessed via ultrasonography and muscle strength was assessed by bench press one-repetition maximum. Effects were explored with two-way mixed ANOVA and non-clinical magnitude-based inferences. Results: No group-by-time interaction was detected for any variable (P > 0.05). When compared to small magnitudes, the pectoralis major muscle thickness changes were likely greater in OSL compared to TDL for the dominant (ES = 0.70; 87% likely greater) and nondominant pectoralis (ES = 0.77; 91% likely greater) as well as the sum of both pectorals (ES = 0.80; 92% likely greater). Similarly, a likely greater effect for absolute (ES = 0.57; 82% likely) and relative (ES = 0.67; 85% likely) bench press strength was seen with OSL. Conclusion: Magnitude-based inferences interpreted here support the notion that OSL may be an advantageous training modality to enhance pectoral muscle thickness and bench press strength.
The present study examined the effects of a reciprocal, slow velocity forearm flexion and extension task on fatigue-induced changes in isokinetic torque, agonist and antagonist muscle activation, and coactivation ratios at slow and moderate velocities.
Nine women (mean ± SD: age = 21.0 ± 1.7 years; body mass = 68.1 ± 8.2 kg; height = 167.4 ± 7.2 cm) completed pre-testing for forearm flexion and extension isokinetic peak torque at 60 and 180°/s, a fatiguing task of 50 maximal, reciprocal, isokinetic muscle actions at 60°/s, and post-testing. The amplitude (AMP) of the electromyographic (EMG) signals from the biceps and triceps were simultaneously recorded. Torque and EMG AMP were normalized to the corresponding values from the pre-testing peak torque movements. Repeated measures ANOVAs and pairwise comparisons were used to identify mean changes in torque, EMG AMP, and coactivation ratios.
The torque analyses indicated significant decreases from pre- to post-testing for forearm flexion (14.1% ± 5.0%; P < 0.001) and extension (25.4% ± 12.2%; P < 0.001) at 60°. At 180°/s there was a significant decrease, collapsed across the forearm movements (24.7% ± 11.7%; P < 0.001). For EMG AMP and coactivation ratios, there were no changes (P > 0.05) from pre- to post-testing for either velocity or movement.
The torque responses were velocity-specific, with greater fatigability exhibited for forearm extension versus flexion at 60°/s, but no differences at 180°/s. The parallel EMG AMP responses between the agonist and antagonist muscles for both velocities supported the lack of fatigue-induced changes in coactivation ratios. Thus, our results demonstrated that fatigue-induced decreases in torque were not attributable to increases in antagonist activation or coactivation.
Countermovement vertical jump testing has become a staple in athlete assessment protocols. As the popularity of jump testing has grown, a need and interest has also grown in identifying the factors that underpin high-level outputs. As jump height alone as a variable in evaluating vertical jump performance has been questioned in athletic populations, other variables such as the reactive strength index modified (RSIm) allow for not only evaluating the outcome, but the strategy used in obtaining that outcome.
Thus, the purpose of this investigation was to examine the differences in high and low vertical jump performances, as determined by the RSIm in female collegiate athletes.
Thirty NCAA Division I female volleyball and basketball athletes performed countermovement vertical jump trials on a force platform. The sample was then broken into two groups as determined by median RSIm values. Independent sample t-test were then used to compare groups.
High RSIm group displayed greater jump heights (P < 0.05). Additionally, the high performing group displayed lower eccentric duration times (P < 0.05). No differences between groups were seen in kinetic variables.
The high performing group displayed faster eccentric times which translated to lower values in time to take-off though not statistical significant. The higher RSIm values appear to be a result of both greater jump heights and reduced time to take off. Thus, focus being placed on the speed of the movement during training would be of benefit in improving RSIm values.
The aims of this study were (a) to investigate the effects of a unilateral training program in reducing inter-limb asymmetry in male soccer players; (b) to explore such effects on measures of physical performance and unilateral inter-limb asymmetry. Twenty-four soccer players, randomly assigned to a 6-week unilateral strength and power training (UNI) (n = 12) or a control group (CON) (n = 12), performed single countermovement jump (SLCMJ), single leg broad jump (SLBJ), single leg drop jump (SLDJ), 10-m sprint, and 505 change of direction (COD) speed test. Raw jump scores revealed small to large improvements in SLCMJ, SLBJ, and SLDJ reactive strength index (RSI) (g = 0.46 to 1.66) in the UNI group, whereas negligible changes were found in the CON group (g = − 0.31 to 0.33). Asymmetry indexes showed a moderate significant reduction in the SLDJ (RSI) and in the SLDJ stiffness (K) (g = 1.00 to 1.11) in the UNI group. The between-group comparison indicated a significant change in the SLDJ (RSI) and in the SLDJ (K) (g = 1.01 to 1.07) in favour of the UNI group. Thus, a unilateral training program seems to be able to reduce between-limb imbalances and foster improvements in jump performance, without any detrimental effects on linear or COD speed times. Given the importance of these physical characteristics for soccer, it is suggested that unilateral strength and power training are incorporated into strength training routines for players of all levels.
The present study investigates the association between subjective wellness symptoms, and categorical point-of-care (POC) blood biomarkers of the free oxygen radical test (FORT), and systemic inflammation through high sensitivity C-reactive protein (Hs-CRP), in English Premier League footballers. Data from 38 male professional elite athletes (Mean Age = 25.8, SD = 4.4) from the English Premier League were included in the study, with a total of 674 individual testing records collected over an entire Premier League season. A player wellness questionnaire, along with fasted and rested point-of-care blood biomarker testing were collected weekly across the season. The wellness questionnaire collected subjective symptoms of illness and fatigue, while FORT and Hs-CRP were assessed through point-of-care analysis to highlight periods of excessive hydroperoxide production and systemic inflammation. Using a chi square goodness of fit model, results showed that there was a significant association between the frequency of symptoms logged and categorical POC blood biomarker data of FORT and HsCRP (P < 0.01). Of the records demonstrating normal levels of Hs-CRP and FORT concentrations, 27% logged symptoms with an average of 1.5 symptoms reported per answered record. Comparatively, excessive biomarker values demonstrated 55% of records having symptoms logged, averaging 2.4 symptoms reported per record.
The purpose of this study was to monitor the Indian national rowing team’s training regime and the changes that occur in the rowers’ body composition, muscle cell damage, and training load markers during the phases of preparation for an international competition.
Ten male and 9 female elite rowers from the national team underwent anthropometric assessment and blood tests during 17 weeks of training, at the end of general preparation (W4), preparation (W10), and pre-competition (W17) phase. Body fat% and somatotype were determined by Siri’s equation and Heath-Carter manual, respectively. Assessments of blood biomarkers included measures of creatine phosphokinase (CPK), lactate dehydrogenase (LDH), urea, uric acid, testosterone, and cortisol concentration.
Changes in variables were estimated by repeated-measures ANOVA. Body fat% (P < 0.001; male: d = − 2.03; female: d = − 2.89) and endomorph (P < 0.05; male: d = − 2.05; female: d = − 0.68) decreased significantly at pre-competition, whereas weight, mesomorph, and ectomorph remained unchanged throughout training. Urea (male: d = − 1.47; female: d = − 1.46) and uric acid (male: d = − 0.74; female: d = − 1.71) showed a significant decrease at pre-competition phase in both groups. CPK concentration significantly (P < 0.05) decreased at preparation (d = − 1.05) and increased during pre-competition (d = − 1.28) in male rowers. LDH showed significant increase (P < 0.01) at preparation (male: d = 1.17; female: d = 2.02) and pre-competition (male: d = 1.28; female: d = 2.09) than base preparation. Whereas, no significant changes were observed in cortisol, testosterone, or T/C ratio in subsequent measurements. Significant correlation (P < 0.05) was found between LDH and T/C ratio with rowing timing in male rowers. The 2000 m rowing timing also showed a significant improvement at W17 compared to W4 (male: d = − 1.25; female: d = − 0.94).
In conclusion, our results showed that rowers encounter more muscle damage and less protein catabolism during training season. Additionally, it is evidenced that rowing performance improved and biochemical markers—particularly enzymes—altered largely with altered training load rather than anabolic or catabolic hormone concentration in rowers.
This study investigated the optimal total sleep duration per day required by collegiate athletes to maintain the physical and mental health-related quality of life (HRQOL), compared with non-athlete students.
In this cross-sectional study, a questionnaire survey was conducted to assess demographic variables, lifestyle and sleep habits, and HRQOL in 392 collegiate students (non-athletes, n = 174; athletes, n = 218). Physical component summary (PCS) and mental component summary (MCS) were assessed using the short-form-8 health survey. Participants with both good PCS and MCS were defined as having a good HRQOL. To confirm an association between the total sleep duration per day and good HRQOL, logistic regression analyses were conducted in non-athlete students and collegiate athletes separately. Subsequently, receiver-operating curve (ROC) analyses were performed for the detection of the cut-off point of total sleep duration per day sufficient to maintain a good HRQOL.
The average total sleep duration per day was 7 h 19 min for collegiate athletes, and 78.9% of them had a worse PCS. The cut-off point of total sleep duration per day to maintain good HRQOL for collegiate athletes was 7.92 h (area under ROC, 0.64; P = 0.038; sensitivity, 75.4%; specificity, 57.9%), which was longer than 6.79 h for non-athlete students.
Collegiate athletes required longer nocturnal sleep than non-athlete students. Nevertheless, their habitual nocturnal sleep duration was shorter compared to their optimal duration; around 70% of them faced chronic insufficient sleep. Improving sleep habits and sleep education is important in maintaining their good health-related quality of life.
Exercise intensity is usually prescribed based on a metabolic marker, such as maximum oxygen uptake or maximal lactate steady state. Those markers, however, face some difficulties regarding their practical applicability to the general population. The critical speed emerges as an alternative parameter to determine aerobic exercise intensities through maximal tests using ergometers or field tests, demanding few resources. We evaluated the fidelity of test to predict critical speed and if this parameter could be used to prescribe intensity in aerobic exercise. One hundred recreational runners performed the T10 test and a conventional critical speed test to define running speeds. Out of them, 44 runners proceed continuous and interval races. The critical speed assessed from T10 test was then compared to critical speed measured by three maximal runs in the track field (1200 m, 2400 m, and 3600 m). We found a strong correlation (r = 0.91) and did not find statistical differences (t = 1.8, P = 0.90) between critical speed assessed by T10 (3.89 ± 0.49 m/s) and field-test (3.85 ± 0.51 m/s). T10 is also better associated with running and interval running speeds than metabolic markers. T10 test can be used as a valid alternative method to assess critical speed and to prescribe runs.
Insoles with various wedges have effects on the biomechanical aspects of human movement. The aim of the present study was to investigate the immediate effects of 9 insoles while running on the myoelectric activity of selected trunk muscles. The conditions were no wedge, posterior, anterior, medial, lateral, posterior-medial, posterior-lateral, anterior-medial, and anterior-lateral. Muscles included were rectus abdominis, external oblique, internal oblique, latissimus dorsi, thoracic erector spinae, lumbar erector spinae, multifidus, and quadratus lumborum during running.
Twenty-five (n = 25) able-bodied males participated in this quasi-experimental study. Repeated measures analysis of variance test was used to compare dependent variables among various insole wedges.
Significant differences (P = 0.001) in normalized mean amplitude index between the following wedge conditions were measured while running: posterior-lateral/medial (5.67 ± 1.01 vs. 4.73 ± 1.09) and posterior-lateral/anterior-medial (5.67 ± 1.01 vs. 4.52 ± 1.20) for the internal oblique muscle along with posterior-lateral/anterior (11.44 ± 2.42 vs. 9.26 ± 2.35) for the lumbar erector spinae muscle. Similarly, normalized peak amplitude index differences in the medial/anterior-lateral (9.79 ± 3.33 21 vs.12.03 ± 3.16) and lateral/anterior-medial (11.6 ± 2.56 vs. 9.25 ± 2.38) for the internal oblique muscle and posterior-lateral/anterior-medial (9.58 ± 2.26 vs. 8.78 ± 2.15) for the quadratus lumborum muscle were measured. In contrast, no significant difference was observed for the median frequency index among various insole wedges during running (P > 0.0014).
Decreased activity in the medial wedged conditions may have important negative consequences for the spine, pelvis, and dynamic core. These results provide insights into the effect of various orthotic designs on the EMG activity of central core muscles. Higher activation in an anterior-lateral wedge and lower activation in a medial wedge for core muscles can have clinical relevance, where there is a need to increase, or avoid decrease, core muscle activity.
This study aimed to compare the physical attributes of male and female Volleyball and Beach Volleyball athletes.
Fifty-five athletes from Volleyball (Male, n = 19, age 27.3 ± 6.1 years, body mass 93.2 ± 9.9 kg, and height 196.8 ± 7.4 cm and Female, n = 16, age 28.0 ± 5.6 years, body mass 76.9 ± 8.8 kg, and height 179.9 ± 5.8 cm) and Beach Volleyball (Male, n = 10, age 26.8 ± 3.4 years, body mass 92.9 ± 9.9 kg, and height 195.3 ± 7.9 cm and Female, n= 10, age 31.1 ± 6.2 years, body mass 74.6 ± 8.5 kg, and height 180.9 ± 6.0 cm) participated in the study. All tests were performed in a single visit to the laboratory in the following order: body composition, vertical jump (squat and countermovement jump), isokinetic (knees and shoulders), and cardiopulmonary exercise testing. All variables were analyzed using a two-way ANOVA (Sex and Sport factors) for independent groups.
Beach Volleyball athletes presented lower body fat (P = 0.03; ES = 0.32) and higher maximal cardiorespiratory variables (VO2, HR, and vVO2max). Only flexion bilateral difference (knee) at 60°/s was affected by sex (P = 0.002; ES = 0.63). For shoulders, only dominant external/internal rotation ratio presented a significant interaction for sport and sex (P = 0.05; ES = 0.28). Regarding vertical jumps, Volleyball male players presented a greater elastic index than BV male players (P = 0.002, ES = 0.67).
Beach Volleyball players are thinner and have better cardiorespiratory fitness than Volleyball players. Also, they presented less use of elastic properties for vertical jumping and have a greater muscle imbalance in the hamstrings than Volleyball players.