Abstract BACKGROUND: Isokinetic dynamometry is widely used to assess muscle fatigability, particularly in athletes, due to its high reproducibility and sensitivity. However, the clinical and practical relevance of fatigability parameters remains debated, especially regarding their added value compared to simpler strength indicators. Objectives: The objectives of this study were to determine (1) the redundancy of measured knee extensor fatigability parameters, (2) the feasibility of predicting them from the best repetition (BR 1 ), and (3) the relationship between initial strength and fatigability. Methods: 189 healthy male volunteers (sedentary to elite athletes) performed 30 maximal concentric knee flexions-extensions at 180°.s −1 . Pearson correlations, linear regressions, and k-fold cross-validation (k = 10) assessed parameter relationships and derived predictive equations. Results: Very strong correlations (PCC > 0.80) linked BR 1 to most fatigability parameters, indicating high redundancy. Predictive equations based on BR 1 accurately estimated total/partial sums (R 2 > 0.95, ICC > 0.90). Moreover, stronger individuals exhibited steeper performance declines (PCC < −0.80 between BR 1 and slope of the regression of the performance). Conclusions: Fatigability parameters offer limited added value, as they are highly redundant with BR 1 . Simplified BR 1 -based protocols suffice for clinical use, while full isokinetic testing remains essential for elite athletes or (neuro)muscular pathology requiring precision.
Background Whole-body vibration training (WBVT) stimulates muscles via mechanical oscillations to induce involuntary contractions, offering an alternative for those unable to engage in conventional voluntary resistance exercise. Since blood flow restriction (BFR) promotes adaptations through metabolic stress, combining it with WBVT may potentiate muscular adaptations. Objectives To determine whether muscle strength and hypertrophy adaptations from WBVT could be enhanced when performed under BFR conditions. Methods We searched nine databases (PubMed, Embase, Scopus, Web of Science, Cochrane Library, CNKI, Wanfang, VIP, and CBM) from inception through 25 May 2026. Randomized controlled trials (RCTs) comparing WBVT-BFR with WBVT alone in healthy participants were included. Risk of bias was assessed using the Cochrane RoB 2.0 tool. Meta-analyses were conducted using standardized mean differences (SMD) with 95% confidence intervals (CIs), and overall certainty of evidence was evaluated using GRADE. Results Five RCTs (total n = 153; WBVT-BFR: n = 75; WBVT: n = 78) were included. Pooled analysis demonstrated a significant effect favoring WBVT-BFR for muscle strength (SMD=0.32; 95% CI, 0.03 to 0.61; p = 0.03) with low heterogeneity (I 2 =14%; p = 0.32). For muscle hypertrophy, the pooled effect reached marginal significance (SMD=0.41; 95% CI, −0.01 to 0.83; p = 0.05), with no significant heterogeneity (I 2 =0%; p = 0.60). However, leave-one-out sensitivity analyses revealed that findings for both outcomes were not robust and were heavily influenced by individual studies. Consequently, the overall certainty of evidence for both outcomes was rated as very low. Conclusions The current evidence regarding the superiority of WBVT-BFR over WBVT alone for enhancing both muscle strength and hypertrophy remains inconclusive. Although initial analyses showed a small advantage for strength and a marginal effect for hypertrophy, sensitivity testing revealed both findings were fragile. Consequently, these results must be interpreted with strict caution due to the high risk of bias and very low certainty of the available evidence.
Abstract Objectives To investigate the acute effects of two pre-activation protocols combining blood-flow restriction (BFR) with acute countermovement jump (CMJ) exercise on post-activation potentiation (PAP), to clarify their time-course characteristics and identify the optimal potentiation window, and to elucidate the underlying physiological mechanisms regarding the balance between neuromuscular potentiation and metabolic fatigue induced by different occlusion patterns. Materials and methods Eighteen healthy male track-and-field athletes specializing in sprint and jump events participated in this study, which utilized a randomized, crossover, repeated-measures design. Kinetic data were collected using a Kistler 3D force plate at baseline and at 0, 4, 8, 12, and 16 min post-stimulus following two distinct protocols executed at 50% arterial occlusion pressure: (1) a continuous protocol, involving one set of five CMJs with BFR maintained during 60-s rest intervals; and (2) an intermittent protocol, involving one set of five CMJs with BFR released during rest intervals. The PAP effect was evaluated based on jump height, peak power, peak vertical ground reaction force (vGRF), and the average rate of force development (RFD). Results Two-way repeated-measures ANOVA revealed significant protocol × time interaction effects for all kinetic variables ( P = 0.001; η p 2 = 0.73–0.81). Compared to the continuous protocol, the intermittent protocol yielded a significantly higher main effect for jump height (mean difference: 0.14 m, 95% CI: 0.13 to 0.16 m; P = 0.001; η p 2 = 0.79) and peak power (mean difference: 12.68 W·kg −1 , 95% CI: 12.16 to 13.08 W·kg −1 ; P = 0.001; η p 2 = 0.76). In the continuous protocol, all kinetic parameters across the 0 to 16-min time points were significantly reduced relative to baseline ( P < 0.05; η p 2 = 0.72–0.75), demonstrating immediate and sustained performance inhibition. Conversely, jump height, peak power, peak VGRF, and average RFD in the intermittent protocol were significantly increased at 0, 4, and 8 min compared to baseline values ( P < 0.05; η p 2 = 0.65–0.77), with peak enhancements manifesting between 4 and 8 min before returning to baseline at 12 min ( P < 0.05). Conclusion The results indicate that the acute intermittent BFR pre-activation protocol successfully induces post-activation potentiation, effectively enhancing CMJ height and explosive power. Conversely, the continuous protocol fails to elicit PAP and instead exerts an acute inhibitory effect due to prolonged occlusion and accumulated fatigue. The optimal temporal window to exploit the PAP effect induced by the intermittent protocol is within 8 min post-stimulus.
Background This cross-sectional study aimed to investigate how different hip abduction angles influence hip abduction torque and muscle activation of the gluteus medius (Gmed) and tensor fasciae latae (TFL) during side-lying hip abduction in individuals with Gmed weakness. Methods Twenty-five individuals with Gmed weakness participated in this study. Participants performed isometric hip abduction in a side-lying position at four joint angles (−15°, 0°, 15°, and 30°). Hip abduction torque was measured using an isokinetic dynamometer, while surface electromyography was used to simultaneously record Gmed and TFL muscle activities. The Gmed/TFL activity ratio was calculated to examine relative activation patterns. Hip abduction torque was normalized to body weight. Results Peak hip abduction torque was greatest at −15°, followed by 0°, 15°, and 30°. Electromyographic analysis showed that Gmed activity was greater at −15° and 0° than at 30°, whereas TFL activity was lowest at 30°. Although no significant pairwise differences were detected, the Gmed/TFL activity ratio tended to increase with increasing hip abduction angle, reaching its highest value at 30°. Conclusion Hip abduction angle influences hip abduction torque and muscle activation during side-lying hip abduction in individuals with Gmed weakness. A more adducted starting position was associated with greater torque, whereas a more abducted position showed lower TFL activity and higher Gmed/TFL ratios; thus, hip abduction angle may be considered in rehabilitation, with caution.
Introduction: This exploratory study examined how eccentric braking characteristics (braking rate of force development (RFD) and braking force impulse (FI) relate to push-off force distribution and jump height during bilateral and unilateral countermovement jumps (CMJ). Methods Data from 206 physically active individuals (basketball players and students) were retrospectively analyzed. Hierarchical multiple regression models predicted jump height, with sex and training status entered as covariates, followed by braking RFD and braking FI, and finally the early-to-late push-off FI ratio. Additional models examined whether braking variables predicted the FI ratio. Results In bilateral CMJ, braking variables and the FI ratio significantly improved model fit beyond sex and training status, with the FI ratio emerging as a strong independent predictor of jump height (lower early-to-late push-off FI ratio: β = −0.367, p < 0.001). Braking FI was positively associated with jump height (β = 0.165, p = 0.003), and braking RFD also showed a positive independent association in the final model (β = 0.197, p < 0.001). In unilateral CMJ, the FI ratio similarly predicted jump height (lower ratio: β = −0.311, p < 0.001), whereas braking RFD was not independently associated and braking FI showed a modest positive effect (β = 0.154, p = 0.009). Braking RFD positively predicted the FI ratio in both jump tasks, indicating an association with a more early-loaded push-off profile. Conclusion Jump height was consistently related to push-off force distribution, with relatively greater late-phase FI (i.e., a lower early-to-late ratio) associated with superior performance. Braking FI showed modest positive associations with jump height, whereas braking RFD primarily influenced push-off force distribution and displayed task-dependent relevance for performance.
Background There is limited knowledge about the relationships between concentric and eccentric lower-limb strength and sprint, change-of-direction (CoD), and forward or lateral jump performance in elite youth soccer players. Objective This study investigated the associations between knee strength and sprinting, CoD, and single-leg jump performance in youth soccer players (mean age = 16 years; n = 41). Methods Maximal isokinetic knee extension and flexion strength (60°/s and 180°/s) and Nordic hamstring strength were assessed and correlated with single-leg forward hop and side-bounce distance, 10 m and 30 m sprint times, and 90° and 180° CoD test times. Results Pearson correlations revealed task- and leg-specific relationships. Stronger knee extensors at 60°/s were associated with faster 90° CoD performance, whereas stronger knee flexors and higher flexion-to-extension ratios at 180°/s were linked to faster 10 m and 30 m sprints. When the right leg acted as the inside turning leg, greater knee flexor strength (180°/s) was related to slower 180° CoD performance but faster 10 m and 30 m sprint times. When the right leg acted as the outside leg: (i) higher flexion-to-extension ratios (60°/s) corresponded to slower 90° CoD performance; (ii) stronger knee flexors (180°/s) with slower 180° CoD; and (iii) higher strength ratios at 180°/s with slower 90° and 180° CoD performance. No significant associations were found for the left leg or single-leg jump tests. Conclusions These findings highlight the movement- and limb-specific nature of lower-limb strength contributions in youth soccer players. Overall, hamstring strength supported sprint performance, whereas quadriceps strength underpinned CoD ability.
This study aimed to investigate the relationship between the break-point angle (BPA) measured with the Nordic Angle app and absolute and relative eccentric knee flexion peak torques. Twenty-one male participants performed Nordic hamstring exercise (NHE) trials to determine their BPA, followed by absolute eccentric knee flexion strength testing. Absolute eccentric knee flexion peak torque was divided by body weight to calculate relative eccentric knee flexion peak torque. No Pearson correlation was observed between BPA and absolute eccentric knee flexion peak torque ( r p = −0.05, p = 0.85). Conversely, the Pearson correlation between BPA and relative eccentric knee flexion peak torque was significant ( r p = −0.54, p < 0.05). BPA measured with the Nordic Angle application was associated with relative eccentric knee flexor peak torque. As this study did not include a clinical population nor investigate hamstring injury incidence, clinical implications should be interpreted cautiously, and future research is required to determine whether BPA can predict hamstring injury risk.
Background Glenohumeral internal rotation range of motion deficit (GIRD) is linked to shoulder strength in the glenohumeral (GH) joint and to increased risk of throwing-related injuries. In adolescent overhead athletes, GIRD ≥25° has been associated with a four-fold higher risk of upper-extremity injury. However, from a functional perspective relevant to overhead throwing, the extent to which GIRD is related to the dynamic strength of the shoulder rotators has not been investigated. Objective This study compared internal rotation (IR) and external rotation (ER) torque between adolescent baseball athletes with and without GIRD, and examined factors associated with concentric and eccentric IR/ER torque, including GH joint range of motion (ROM). Method Eighty male adolescent baseball athletes participated. IR, ER, total rotational ROM, and GIRD were measured. Concentric and eccentric torque of IR and ER, as well as functional strength ratios, were assessed. Group differences were analyzed with independent t-tests, correlations with Pearson's coefficients, and predictors with Stepwise multiple regression analysis. Results Concentric IR and ER torques were significantly lower in the GIRD group than in the non-GIRD group (mean differences: 4.6% and 6.9% body weight, respectively; p < 0.05). Concentric torques showed poor to fair correlations with GH joint rotational ROM, particularly reduced IR ROM and increased GIRD. Eccentric torques did not differ significantly between groups. Regression analysis identified IR ROM and GIRD as significant predictors of concentric torque, while antagonist exhibited the greatest relative influence on the agonist. Conclusions Concentric shoulder strength (IR and ER torques) is reduced in adolescent baseball athletes with GIRD and is significantly associated with IR ROM loss. IR ROM and GIRD were key predictors of concentric torque, while antagonist strength exerted the greatest relative influence on agonist function. In contrast, eccentric torques showed no group differences or meaningful correlation with GH joint ROM.
Background This study aimed to examine how muscle strength and balance in adolescent recreational football players were affected by FIFA 11+ (11+). Study design: Randomized controlled study. Methods The research comprised 24 football players from a team in an amateur league(age: 16.3 ± 0.8 years; height: 176.9 ± 7.3 cm; body mass: 67.3 ± 8.7 kg; BMI: 21.4 ± 1.9 kg/m 2 ). The experimental group (N = 13) had three applications of the 11 + each week for nine weeks. The usual warm-up was continued by the control group (N = 11). The footballers underwent isokinetic and Star Excursion Balance Tests (SEBT) both before and after an intervention. Results Prior to the intervention, the experimental group's right hamstring-to-quadriceps (H/Q) strength ratio at 60 °/sec was significantly higher than that of the control group (p = 0032). Following the intervention, there was no difference between the groups (p > 0,05). After training at 240 °/sec, only the left quadriceps peak torque value of the experimental group was significantly higher compared to the control group (101.2 ± 21.4 vs. 85.8 ± 10.7 Nm, p = 0.042). In the comparisons of the groups after the intervention, the experimental group in SEBT was found to be significantly higher (85.4 ± 9.9 vs. 78.0 ± 6.7 cm, p = 0.040) in the right anteromedial aspect while there were no differences between the groups in the other aspects (p > 0,05). In SEBT, assessments of the within-groups before and after the intervention revealed a significant difference in nearly every aspect between the control group and the experimental group (p < 0,05). Conclusion The FIFA 11 + program appears to be more effective in improving dynamic balance than isokinetic muscle strength in adolescent amateur soccer players. These findings suggest that while FIFA 11 + may enhance neuromuscular control, additional strength-focused training may be required to elicit substantial strength gains in this population. Clinical relevance FIFA11 + is a widely used programme on adolescent football players, and understanding effects on balance and muscle strength can help to understand efficiency of the programme for injury prevention at early ages.
Background Although subjects with forward head/rounded shoulders posture (FHRSP) may exhibit changes in scapular position and periscapular muscle strength relative to normal subjects, few studies have investigated this. Objective We compared scapular position and periscapular muscle strength between subjects with and without FHRSP. Methods In total, 50 subjects with FHRSP and 50 normal subjects were included. The craniovertebral angle (CVA) and rounded shoulder angle (RSA) were measured to determine FHRSP. To compare scapular position, scapular protraction, elevation, upward rotation, and anterior tilt were measured. To compare periscapular muscle strength, the strengths of the upper trapezius, middle trapezius, lower trapezius, and serratus anterior were measured using an isometric hand-held dynamometer. Results Relative to normal subjects, those with FHRSP had elevated, protracted, and anteriorly tilted scapulae and significantly weaker middle trapezius, lower trapezius, and serratus anterior (p<0.05). Both CVA and RSA showed negative correlations with protraction, anterior tilt of the scapula; they showed moderate positive correlations with scapular elevation. The strengths of the middle trapezius, lower trapezius, and serratus anterior muscles were moderately correlated with CVA and RSA (p<0.05). Conclusions Relative to normal subjects, those with FHRSP exhibited changes in scapular position and periscapular muscle deficits. This information will be useful for designing exercise programs for individuals with FHRSP.
Background Although an imbalance between the thoracic and lumbar erector spinae muscle activity is known to contribute to spinal dysfunction, the factors influencing this muscle balance, particularly thoracic extension mobility, remain unclear. Objectives This study investigated the associations of thoracic kyphosis and thoracic extension mobility with erector spinae muscle activity and muscle balance. Method Ninety-four healthy participants underwent measurements of thoracic kyphosis angle, thoracic extension angle, and erector spinae muscle activity (longissimus thoracis, iliocostalis lumborum pars thoracis, and iliocostalis lumborum pars lumborum). Muscle balance was assessed using the ratios of longissimus thoracis to iliocostalis lumborum pars lumborum and iliocostalis lumborum pars thoracis to iliocostalis lumborum pars lumborum. Regression analyses were conducted with erector spinae muscle activities and their ratios as independent variables, and thoracic kyphosis and thoracic extension as dependent variables. Results Regression analyses showed that the ratio of longissimus thoracis to iliocostalis lumborum pars lumborum and the activity of the iliocostalis lumborum pars thoracis significantly predicted thoracic extension mobility (adjusted R 2 = 0.14, p < 0.001), while the activity of the iliocostalis lumborum pars lumborum significantly predicted thoracic kyphosis (adjusted R 2 = 0.04, p = 0.026). Conclusions These findings suggest that the assessment and intervention of thoracic extension mobility may be significantly associated with the erector spinae muscle balance during trunk extension exercises.
Abstract Purpose This study evaluated the construct validity of the inertial-load protocol, the New Power Bike Test (NPBT), by comparing it with the Wingate Anaerobic Test (WAnT) and examining its correlation with criterion measures, including Vertical Jump (VJ) and Isokinetic Leg Strength (ILS). Methods Thirty-seven healthy adults performed the standard 30-s WAnT and the NPBT (four 4-s maximal accelerations against inertial resistance) in a randomized and counterbalanced crossover design. Data were analyzed using paired t-tests with Cohen's d effect sizes, Pearson and Spearman rank correlations with 95% confidence intervals, Bland–Altman analysis, and Williams’ test for comparing dependent overlapping correlation coefficients. Results The NPBT produced significantly higher mean peak power (976.18 W; 11.47 W·kg −1 ) than the WAnT (705.67 W; 8.34 W·kg −1 ). Also, the NPBT demonstrated significant correlations with both VJ ( r = 0.666 to 0.766, p < 0.001) and ILS ( r = 0.638 to 0.861, p < 0.001). In contrast, the WAnT showed weak associations with VJ and inconsistent relationships with ILS ( r = 0.240 to 0.663). Bland–Altman analysis confirmed that the protocols are not interchangeable at the individual level (bias = 270.52 W; 95% LoA: −193.02 to 734.05 W). Williams’ test showed that NRPP correlated significantly more strongly than WRPP with all five criterion variables (all p ≤ 0.031). Conclusion The NPBT and WAnT are not interchangeable assessment tools. The NPBT provides greater concurrent validity for evaluating instantaneous peak neuromuscular power, likely due to its ability to facilitate force-velocity auto-optimization and specifically target the phosphagen energy system. The WAnT remains appropriate for assessing anaerobic capacity and fatigue tolerance.
Background When the hamstring muscles are tight, the risk of injury during physical activity increases, prompting the frequent use of active interventions, such as stretching, in clinical settings. However, most previous proprioceptive neuromuscular facilitation (PNF) stretching studies have been conducted at the end-range of motion, which does not correspond with the point of maximal force output according to the length-tension relationship. The purpose of this study was to compare the effects of PNF stretching performed at the mid-range, where optimal force production is theoretically possible, with those performed at the end-range. Additionally, it aimed to investigate whether flexibility gains differed according to the degree of hamstring tightness.Methods Hamstring tightness was evaluated using the active knee extension (AKE) test. Participants were categorized into severe and mild tightness groups. PNF stretching was performed at either 100% of maximal range of motion (MaxROM) or 50% MaxROM. Flexibility changes were assessed post-intervention using the AKE test.Results In the severe hamstring tightness group, significant flexibility improvements were observed after PNF stretching at both 100% and 50% MaxROM. In contrast, the mild hamstring tightness group showed significant improvement only at 100% MaxROM.Conclusions The effectiveness of PNF stretching in increasing flexibility varies according to joint position (100% vs. 50% MaxROM) and the initial severity of tightness. Notably, individuals with severe tightness experienced significant gains even at mid-range, suggesting that mid-range PNF stretching may serve as a viable alternative for patients who experience discomfort or pain at maximal ranges.
Purpose Subjects (n = 45) did two high-intensity interval training (HIIT) workouts on a cycle ergometer to assess intermittent palm cooling's influence on this exercise mode. Workouts included three 20-s sprints separated by two minutes of active recovery and were done either with, or without, palm cooling (PC, no PC) in a randomized order. Dependent variable data were assessed with 2-factor ANOVAs, with repeated measures per independent variable. A Bonferroni correction (alpha = 0.05/6 = 0.0083) mitigated the Type I error risk based on the number of dependent variables analyzed. Significant dependent variables were assessed with pairwise comparisons to identify the source of the differences. Results Palm temperature (PT) and thermal flux (FLX) each had significant two-way interactions; the latter dependent variable saw PC > no PC at multiple times during and after workouts. Peak power, as an absolute (PP), and relative to body mass (PP/KG), value had significant two-way interactions, with PC > no PC for the second and third sprints as identified with pairwise comparisons. Inter-treatment PP and PP/KG differences likely benefitted from PC's significantly higher FLX values. Conclusions Exercise with repetitive bursts of supramaximal activity may benefit from intermittent PC to abate body heat accrual.
Background This meta-analysis evaluated isokinetic strength profiles in soccer players, focusing on the hamstring-to-quadriceps (H/Q) ratio across three field positions.Objective To assess positional differences in isokinetic strength and hamstring-to-quadriceps (H/Q) ratios based on the categorization structure that permits comparative evaluation (DEF-MID-ATT).Methods Included were studies that reported quadriceps and hamstring peak torque and H/Q ratios at 60 degrees/s and 180 degrees/s. Three positional pairs were compared: (1) defenders vs. midfielders, (2) defenders vs. attackers, and (3) midfielders vs. attackers.Results Defenders maintained superior quadriceps and hamstring strength over both midfielders and attackers. They also maintained higher H/Q conventional and functional ratios than midfielders. Attackers displayed moderately stronger hamstrings than midfielders.Conclusions Defenders' greater quadriceps and hamstring strength (particularly versus midfielders) likely reflects the mechanical demands associated with their field roles. These findings suggest that position-specific strength profiling may help guide training targets and reference values in soccer.
Objective: This study investigates the effects of quadriceps isometric contraction training (QICT) on the symptoms, postural control, and movement ability of elderly women with knee osteoarthritis (KOA). Methods: Forty-two older women with KOA were randomly divided into an experimental group (n = 21) and a control group (n = 21). All participants received the same health education for 16 weeks. The experimental group underwent QICT five times per week (contraction and relaxation for 5 s each, 30 repetitions per set, 10 sets, with a 30-s rest between sets). Assessments of KOA symptoms, postural control, and movement ability were performed at baseline and after the 16-week intervention. Results: 1) At the 16th week compared to baseline: The experimental group showed a 27.1% reduction in pain, a 13.8% reduction in stiffness, and a 15.7% reduction in functional impairment scores. The body sway index on a firm surface with eyes closed decreased by 14.3%. The knee extension peak torque at 180 degrees/s increased by 31.6%, and the angle difference in the knee flexion proprioception test (30 degrees) decreased by 24.5%. The 6MWT distance increased by 11.9%, and the time for the TUG decreased by 12.9% (P < 0.05). 2) At the 16th week, group comparisons showed that the experimental group had significantly lower pain scores, body sway index on a firm surface with eyes closed, and angle difference in the knee flexion proprioception test (30 degrees) (P < 0.05), and significantly higher knee extension peak torque at 180 degrees/s and 6MWT distance compared to the control group (P < 0.05). Conclusion: Quadriceps isometric contraction training can significantly improve pain, stiffness, functional impairment, static balance ability, knee extension strength, and 6-min walk distance in older women with KOA, as well as enhance knee flexion proprioception. These results indicate that 16-week QICT is a safe and economical non-pharmacological intervention that can effectively improve the clinical symptoms and functional status of older women with KOA, providing a feasible treatment option for community and outpatient rehabilitation. Notably, the 31.6% increase in knee extensor peak torque (180 degrees/s) exceeds the MCID (20%) for older adults with KOA, reflecting significant clinical benefits.
Background The gluteus maximus (GM) and biceps femoris (BF) play important roles in maintaining the stability and mobility of the hip joint during various bridge exercises. The bases of support (BOS) during bridge exercises might have different effects on the muscle activities of the lower extremities. Objective This study aimed to examine the activation of the GM, BF, and multifidus (MF) muscles and the GM/BF and MF/BF ratios during bridge exercises with three different BOS in healthy individuals. Methods Twenty healthy individuals participated using surface electromyography of the GM, BF, and MF muscles. The participants were asked to perform bridge exercises in a randomized order: conventional bridge exercise (BE), bridge exercise on a Togu (BET), and bridge exercise on a foam roller (BEF). Results The muscle activation of the GM was significantly different among the three conditions (BE, BET, BEF) (adjusted p-value [Padj] < 0.01). The GM muscle showed higher activity with BEF compared to BE and BET (Padj < 0.01). The BF showed a significant decrease in BET and BEF compared to BE. The ratios of GM/BF and MF/BF showed a significant increase in BEF compared to BE (Padj < 0.01). Conclusion The BEF is recommended to selectively increase the GM activity and improve the GM/BF and MF/BF ratios.
Background: The push-up is a widely used closed kinetic chain exercise that promotes shoulder joint stability through muscle cocontraction. However, how wrist and hand configurations modulate activation of key scapulothoracic and glenohumeral stabilizers (e.g., serratus anterior) remains insufficiently characterized in healthy adults, limiting mechanism-based exercise prescription. Objective: This study examined how variations in wrist rotation, hand position, and humeral rotation during standardized push-ups affect upper-extremity muscle activation. Electromyographic (EMG) activity of the lower trapezius, upper trapezius, biceps brachii, triceps brachii, pectoralis major, and serratus anterior was measured to assess activation patterns. Findings may inform exercise prescription and rehabilitation using modified push-ups. Methods: Thirty-one healthy young male participants (23.65 +/- 0.49 years) performed push-ups under 11 conditions combining hand position (medial, neutral, lateral), forearm rotation (pronation, supination), and shoulder rotation (internal, external). Surface EMG recorded the activity of six muscles, normalized to maximum voluntary isometric contraction (%MVIC). Group differences were tested with one-way repeated-measures ANOVA with sphericity assessment and Huynh-Feldt correction; Bonferroni-adjusted post-hoc tests and partial eta(2) were reported (alpha=0.05)Results Repeated measures ANOVA showed significant effects of hand position on the lower trapezius (p = 0.01, eta(2) = 0.088), upper trapezius (p = 0.002, eta(2) = 0.13), biceps brachii (p = 0.003, eta(2) = 0.132), and serratus anterior (p < 0.001, eta(2) = 0.215). Serratus anterior exhibited the greatest activation with lateral hand placement. No significant differences were found in the triceps brachii and pectoralis major. Conclusions: Adjusting hand and wrist positions during push-ups can selectively activate the serratus anterior, offering practical implications for rehabilitation and conditioning programs targeting scapular stability.
Introduction Jaboticaba berries have demonstrated high antioxidant activity with potential health benefits. However, their functional properties have not been specifically investigated in relation to exercise performance in trained individuals. Purpose This study aimed to examine the effect of jaboticaba berry juice (JBJ) intake on resistance exercise-induced muscle fatigue. Methods Twenty trained participants consumed 250 mL of jaboticaba berry juice (JBJ; 1300 mg total polyphenols) or a fruit-flavored placebo (PLA) for three days before and on the day of testing. They performed 6 & times; 10 maximal voluntary isokinetic contractions (MVIC) of the elbow flexors and 15 & times; 10 of the knee extensors. MVIC, as an indicator of muscle fatigue development, and total work (TW) were evaluated during the resistance exercise protocol. Results Exercise significantly reduced MVIC (p < 0.001) in both upper and lower limbs. JBJ intake attenuated the reduction in MVIC, reflecting a mitigation of muscle fatigue development, in the elbow flexors (p = 0.049) and knee extensors (p = 0.047) only in males, and improved TW performance (p = 0.004) in JBJ compared with PLA. Conclusion Consumption of jaboticaba berry polyphenols attenuated resistance exercise-induced muscle fatigue development in trained males and improved total work.
