Background/Objectives: The present study aimed to compare the improvement in lower-extremities local muscular endurance following moderate-intensity resistance exercise performed either as two sets to momentary failure or as four repetition-matched non failure sets. Methods: Fifteen physical education students (10 males, 5 females; age: 21.9 ± 3.1 years, body mass: 71.2 ± 11.4 kg, height: 1.74 ± 0.08 m) completed a counterbalanced within-participant unilateral trial comparing two resistance training conditions: failure (two sets performed to momentary failure with one lower extremity) and non-failure (the same total number of repetitions distributed across four sets with the contralateral extremity). Both conditions involved leg press exercise at 50% of their one repetition maximum (1RM), performed three times per week for four weeks. Local muscular endurance, leg-press 1RM, quadriceps cross-sectional area (CSA), and body composition were assessed before and after training. Results: Absolute and relative muscular endurance increased significantly after training in both lower extremities (Failure: 105.9 ± 57.54%; 56 ± 44.57%, p < 0.001; Non-failure: 76.7 ± 42.10%; 33.9 ± 30.75%, p < 0.001, respectively), with significant differences between them (p < 0.05, ηp2 = 0.458 and 0.322, respectively). Leg press 1RM and quadriceps CSA increased significantly (Failure: 20 ± 14.21%; 11.2 ± 7.33%, p < 0.001; Non-failure: 20.5 ± 9.92%; 10.7 ± 6.10%, p < 0.001, respectively), with no significant differences between conditions (p > 0.05). Conclusions: Training to momentary failure elicited significantly greater increases in local muscular endurance than the repetition-matched non-failure protocol. However, these results suggest that repetition-matched, non-failure protocols offer an effective alternative for improving local muscular endurance, while producing increases in maximum strength and muscle size, with no statistically significant differences between conditions, in young, physically active adults without systematic resistance training experience.
Background: Body composition may be associated with the expression of cardiorespiratory fitness, particularly when peak oxygen uptake (VO2peak) is normalized to body mass or lean mass. This exploratory, cross-sectional, single-center study primarily examined associations between body composition and absolute, body-mass-normalized, and lean-mass-normalized VO2peak. Secondarily, we compared male and female CrossFit® participants and tested whether the between-sex difference in VO2peak varied by expression method. Methods: Fifteen trained CrossFit® participants recruited from a single affiliate were included, comprising 9 males (30.0 ± 4.2 years; 82.6 ± 4.0 kg; 176.3 ± 4.2 cm; mean ± SD) and 6 females (36.3 ± 6.6 years; 58.7 ± 3.4 kg; 158.3 ± 5.1 cm). Participants underwent dual-energy X-ray absorptiometry and an incremental treadmill test to volitional exhaustion with breath-by-breath gas analysis. Sex differences were assessed using Welch’s independent-samples t-test, and associations using Pearson and sex-adjusted partial correlations, with false discovery rate correction. A log-scale linear mixed-effects model with participant as a random intercept was used to test the sex × VO2peak-expression interaction. Results: Males presented greater total and lower-limb lean mass and lower body fat percentage than females. Absolute VO2peak was ~61% greater in males (4.1 ± 0.5 vs. 2.5 ± 0.4 L·min−1), whereas the difference was reduced to ~15% when normalized to body mass and ~5% when normalized to lean mass. The sex × expression interaction was significant (p < 0.001), indicating that the magnitude of the between-sex difference was not constant across expression methods. Absolute VO2peak was strongly associated with total lean mass (r = 0.908), lower-limb lean mass (r = 0.879) and body mass (r = 0.891; all pFDR < 0.001). Body-mass-normalized VO2peak was inversely associated with body fat percentage (r = −0.555) and positively associated with total lean mass (r = 0.558; both pFDR = 0.044). None of the sex-adjusted associations remained significant after FDR correction. Conclusions: Body composition was associated with aerobic fitness expression in CrossFit® participants, with lean mass related to absolute VO2peak and adiposity to body-mass-normalized VO2peak. The significant sex × expression interaction showed that the between-sex difference depended on the scaling method.
Clinical assessment commonly relies on physiological variables interpreted as isolated values or against population-derived thresholds. Although indispensable, these approaches provide limited information about regulatory flexibility, inter-system coordination, and recovery after stress. Physiological signals contain structured fluctuations across multiple temporal scales that reflect dynamic regulation and interactions among organ systems. This article proposes adaptive physiological reconfiguration as an integrative framework for interpreting disease-related changes in physiological dynamics. We hypothesize that disease-related vulnerability is associated with a reduced capacity of physiological systems to reconfigure signal dynamics and inter-system relationships appropriately across changing functional states and to restore a context-appropriate organization after perturbation. Heart rate variability provides a conceptual starting point, while network physiology extends this perspective toward multisystem regulation. Continuous multimodal monitoring and artificial intelligence may support the characterization of these dynamics but cannot establish causality. The framework generates testable predictions: dynamic and multisystem features should provide reproducible information beyond corresponding mean values and isolated signals, while recovery trajectories should help characterize physiological resilience. These hypotheses require standardized measurement, external validation, and prospective evaluation.
Background/Objectives: Valsartan/sacubitril improves outcomes in heart failure, but its effects on cardiac performance in chronic hypertension remain unclear. We investigated the effects of chronic valsartan/sacubitril treatment on hemodynamics, cardiac morphology and function, coronary perfusion pressure, and left ventricular responses in spontaneously hypertensive rats (SHR). Methods: Thirty-two male SHR were assigned to Vehicle, Valsartan, Valsartan/Hydrochlorothiazide, or Valsartan/Sacubitril groups (n = 8) and treated for 12 weeks. Hemodynamic and echocardiographic parameters were assessed at 18 and 30 weeks of age. At 30 weeks, isolated-heart responses to progressive increases in coronary flow and to β-adrenergic stimulation were evaluated using the Langendorff technique. Results: All pharmacological treatments reduced blood pressure versus Vehicle, with no additional reduction from combination therapy compared with Valsartan alone. Echocardiographic parameters showed time-related changes without treatment-specific effects. At the highest coronary flow levels, Valsartan/Sacubitril preserved left ventricular pressure and showed greater dP/dtmax and more negative dP/dtmin values than all other groups. β-Adrenergic responsiveness also differed among groups, particularly at higher agonist doses. Conclusions: In SHR, all pharmacological treatments reduced blood pressure to a similar extent, with no additional reduction when valsartan was combined with hydrochlorothiazide or sacubitril. In the isolated heart, however, only valsartan/sacubitril maintained left ventricular contractile performance.
Purpose: This exploratory cross-sectional study examined associations between generalized joint hypermobility (GJH), physical performance, and ankle mobility in physically active young adults. Methods: Forty university students (28 males and 12 females) from Korea National University of Transportation were recruited by convenience sampling. GJH was assessed using the Beighton Scoring System (BSS), and outcomes included handgrip strength (HGS), countermovement jump (CMJ), and passive ankle range of motion (ROM). Pearson correlations, GJH–NGJH group comparisons, and exploratory sex-stratified analyses were performed. All p values were unadjusted and interpreted as nominal. Results: BSS score showed a positive association with left ankle dorsiflexion ROM at the unadjusted significance level (r = 0.322, 95% CI [0.012, 0.576], unadjusted p = 0.043); this association did not meet the Bonferroni-adjusted threshold for seven principal correlations, whereas no significant associations were observed with HGS, CMJ, or other ankle-ROM outcomes. No significant differences were found between GJH and NGJH groups. Males showed higher absolute HGS and CMJ, whereas females showed greater left ankle dorsiflexion ROM (p = 0.045). Sex-stratified correlations were not statistically significant, and no significant sex difference in correlation coefficients was detected. Conclusions: No statistically significant associations were detected between BSS scores and HGS or CMJ performance. The nominal association with left ankle dorsiflexion should be interpreted cautiously and considered hypothesis-generating.
