Scandinavian Journal of Medicine & Science in Sports最新文献

Static stretching immediately affects various neuromusculoskeletal components. Among quadriceps muscles, only the rectus femoris (RF) is stretched by hip extension and knee flexion. The aim of this study was to investigate the motor unit (MU) firing behaviors of two synergistic muscles after selective static stretching on only one side. Fourteen males (23.7 ± 2.4 years) performed knee extension tasks before and after the intervention: static stretching or control conditions. The static stretching protocol consisted of passive hip joint extension and knee joint flexion as selective stretching of the RF for 1 min, repeated for 6 sets, while a 6-min rest was applied as the control condition. MU firings of RF and the vastus lateralis (VL) were detected using high-density surface electromyography, and the MU recruitment threshold and firing rate were calculated during ramp-up contraction to 35% of maximal voluntary contraction. RF stiffness, evaluated by shear wave elastography, was significantly reduced after static stretching, and not VL stiffness (interaction: p = 0.037). There were main effects of time, but no interaction in the MU recruitment threshold of RF (p = 0.282), firing rates of either muscle (RF: p = 0.363, VL: p = 0.557), or maximal strength (p = 0.362), suggesting that these variables were changed after both conditions. However, an interaction was noted in the recruitment threshold of VL (p = 0.018), indicating that the decline in recruitment threshold of VL was greater in the static stretching (from 24.9 ± 6.3 to 21.7 ± 6.1 %MVC) than in the control condition (from 24.4 ± 6.7 to 22.3 ± 6.1 %MVC). These findings suggest that reducing muscle stiffness by static stretching in one muscle can enhance MU recruitment in the other synergist while the change was slightly small.

Physiological resilience has recently been recognized as an additional factor that influences endurance exercise performance. It has thus been incorporated into a modified, contemporary version of "the Joyner model" which acknowledges that start-line values of V̇O₂max, efficiency or economy, and metabolic thresholds are prone to deterioration, often with appreciable interindividual variability, during prolonged endurance exercise. The physiological underpinnings of resilience are elusive and sports physiologists are presently concerned with developing practical testing protocols which reflect an athlete's resilience characteristics. It is also important to consider why some athletes are more resilient than others and whether resilience can be enhanced-and, if so, which training programs or specific training sessions might stimulate its development. While data are scant, the available evidence suggests that training consistency and the accumulation of relatively large volumes of training over the longer-term (i.e., several years) might promote resilience. The inclusion of regular prolonged exercise sessions within a training program, especially when these include bouts of high-intensity exercise at race pace or above or a progressive increase in intensity in the face of developing fatigue, might also represent an effective means of enhancing resilience. Finally, resistance training, especially heavy strength and plyometric training, appears to have positive effects on resilience. Considerations of training for resilience, alongside other more established physiological determinants of performance, will likely be important in the long-term development of successful endurance athletes.

Subjective well-being (SWB), including cognitive and affective components, may be influenced by the management of type 1 diabetes mellitus (T1DM). Physical fitness and adherence to physical activity (PA) are associated with better glycaemic stability and diabetes management. However, the relationship with SWB is not yet understood. The aim of the study was to determine the relationship between physical fitness, PA, and SWB over two years in youths with T1DM. This longitudinal study involved 83 participants (aged 6-18 years; 44.6% girls) from the Diactive-1 Cohort. Physical fitness was assessed by spirometry (peak oxygen consumption) and dynamometry (handgrip strength). PA domains were measured using triaxial accelerometers, whereas the number of days participating in muscle-strengthening activities was assessed using a question. The Cuestionario Único de Bienestar Escolar was used to determine SWB. Glycaemic stability was determined when glycosylated hemoglobin < 7%, coefficient of variability ≤ 36%, and time-in-range target > 70% were met. The linear mixed models used considered three assessments and subject variability, showing significant associations between overall physical fitness (unstandardized beta coefficient [B] = 1.778, 95% confidence interval [CI] 0.413-3.158; p = 0.012) and total PA (B = 0.034, 95% CI 0.005-0.063; p = 0.020) with SWB. Although time did not moderate the association with physical fitness (p = 0.116), this was true for PA only in the second year (p = 0.020). In contrast, glycaemic stability did not moderate the associations (p > 0.05). In conclusion, physical fitness and PA are associated with greater SWB in young people with T1DM, which may play a role in the psychological aspects of disease management.

Combining aerobic and strength training may attenuate neuromuscular adaptations, particularly when both target the same muscle group. This study assessed whether separating the training modalities by muscle groups mitigates this interference. Ninety-six participants (56 males and 40 females) completed a 12-week intervention, divided into three groups: (1) LHLS (lower-body high-intensity interval (HIIT) and strength training), (2) LHUS (lower-body HIIT and upper-body strength training), and (3) LSUS (lower- and upper-body strength training). Maximal (1RM) and explosive strength were assessed using load-velocity profiling, with mean propulsive velocity (MPV) at 30%, 50%, 70%, and 90% of 1RM as a measure of explosive strength. Muscle cross-sectional area (CSA) of the M. vastus lateralis and M. pectoralis major was measured using panoramic ultrasound. Lower-body adaptations were compared between LHLS and LSUS, and upper-body adaptations were compared between LHUS and LSUS. MPV at 70% and 90% of 1RM for the squat (LHLS and LSUS) and bench press (LHUS and LSUS) showed improvements (p < 0.050), with no significant between-group differences. Squat 1RM improved in both LHLS and LSUS, and bench press 1RM increased in both LHUS and LSUS (all p < 0.001). M. vastus lateralis CSA increased in LHLS (p = 0.029) but not in LSUS, whereas M. pectoralis major CSA increased in both LHUS and LSUS (p < 0.001), with no between-group differences. No sex-based differences were observed. Concurrent aerobic and strength training does not impair explosive strength, maximal strength, or muscle hypertrophy, regardless of whether the same or separate muscle groups are targeted.