Objective This study aimed to investigate the acute and prolonged effects of anodal tDCS at different intensities applied over the primary motor cortex (M1) on knee muscular endurance. Methods Seventy healthy adults were randomized into four groups (1 mA, 2 mA, 3 mA, and sham) and received 10 sessions of 20 min tDCS over 4 weeks. The endurance index (EI), calculated as the ratio of work output during the last five to the first five of 15 maximal isokinetic contractions, was assessed at baseline (T0), immediately after the first session (T1), 24 h after the 10th session (T2), and at 1-week follow-up (T3). Results Among the 70 healthy participants, a non-linear dose-response pattern was observed. Only 2 mA tDCS produced significant enhancements in endurance, specifically for left knee flexion, outperforming sham stimulation at T1 and both sham and 3 mA stimulation at T2. Notably, 1 mA and 3 mA showed negligible or attenuated efficacy. Conclusions These findings underscore that tDCS-induced endurance gains are contingent upon optimized intensity and hemispheric targeting, rather than simply applying higher currents. The observed non-linear behavioral response pattern warrants further investigation with neurophysiological measures to elucidate the underlying cortical excitability dynamics.
Background The assessment of muscle oxygenation during isokinetic testing has gained increasing interest by use of near-infrared spectroscopy (NIRS). However, it remains unclear whether muscle oxygenation responses differ according to muscle strength level. Objective This study aimed to investigate changes in quadriceps muscle oxygen saturation (SmO 2 ) and total haemoglobin (tHb) during isokinetic maximal testing at different angular velocities. Methods Forty-six participants were divided into moderate (n = 23) and high strength groups (n = 23) based on normalized peak moment of the knee extensors at 60°/s. SmO 2 and tHb were measured using NIRS at rest, during isokinetic testing at 60°/s and 180°/s, and during recovery on dominant leg. A mixed-design ANOVA was used to examine group, time, and interaction effects. Results Significant main effects of time were found for SmO 2 (p < 0.001) and tHb (p = 0.012), indicating dynamic changes across the protocol. However, no significant group or group × time interaction effects were observed (p > 0.05). Correlation analyses showed moderate associations between tHb and isokinetic strength parameters at 180°/s; however, these were based on pooled data. Conclusions Isokinetic testing at different velocities resulted in significant changes in SmO 2 and tHb, whereas muscle strength level did not significantly influence these responses.
Background Although inter-limb asymmetry is widely investigated, its task-specific nature during multidirectional speed tests remains unclear. The aim of this study was to evaluate the task-specific nature of asymmetry by examining the directional and ordinal consistencies across three common running-based field tests (5-0-5 agility test, 90° change of direction [COD] test, and curve sprint test [CST]). Methods Forty-four elite male youth soccer players (age: 17.7 ± 0.8 years) performed the 5-0-5, 90° COD, and CST on both legs. Inter-limb asymmetry was calculated using performance differentials with limb dominance determined based on the faster limb. Cohen's Kappa ( k ) and Spearman's rank-order correlation (rho) were used to assess the directional and ordinal agreement between the tests. Results Mean asymmetry magnitudes were relatively small (CST: 3.45 ± 2.63%; 5-0-5 and 90° COD: 2.62 ± 2.27%). A perfect directional ( k = 1.00, p < 0.001) and ordinal (rho=1.000, p < 0.001) agreement was found between the 5-0-5 and 90° COD tasks. In contrast, no significant agreements were observed between the CST and 5-0-5 and 90° COD tests ( k = 0.05, p = 0.70). Notably, 51.2% of the players exhibited a total shift in the direction of limb dominance when transitioning from the sharp cuts (i.e., 5-0-5 and 90° COD) to the curve sprint. Conclusion Inter-limb asymmetry is a highly task-specific trait. Linear-based COD tests (5-0-5 and 90° COD) provide similar information regarding asymmetry profiling. However, curve sprinting presents a distinctly independent asymmetry profile. In addition to COD tasks, practitioners may incorporate the CST as a separate assessment tool to profile asymmetry, given its task-specific nature.
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.
