BMC Sports Science Medicine and Rehabilitation最新文献

Purpose: Performance analyses in cross-country skiing often focus on lap or terrain-level splits. However, few studies have explored micro-pacing strategies-particularly in Skiathlon, an Olympic event requiring athletes to complete both classical and freestyle techniques on the same course.

Methods: Thirteen national-level male skiers were tracked during an International Ski Federation-certified Skiathlon using GNSS and trunk-mounted sensors. Instantaneous speed profiles were analysed using one-dimensional statistical parametric mapping (SPM) to identify "race-critical clusters": contiguous intervals where speed significantly predicted section time (α = 0.05) across all eight laps (four classical, four freestyle).

Results: Freestyle laps were 4% faster than classical, with greater terrain-specific speed differences and pacing variability in classical, especially downhills. Seven race-critical clusters were identified: two uphill, four downhill, and one flat. These accounted for 11.3 s (classic) and 10.9 s (freestyle) of the time gap between the fast and slow group. In these segments, faster skiers used higher-gear sub-techniques and exhibited longer cycle lengths and/or higher frequencies (p < 0.05).

Conclusions: Within race-critical clusters, the faster skiers gained substantial time advantages. Secondary analyses showed clear differences in sub-technique selection and kinematic profiles, suggesting that technical execution plays a critical role in these performance gains. Athletes and coaches may consider integrating GNSS-based tracking, SPM, and wearable-derived technique analysis into race evaluation to move beyond traditional split times and focus training on the most decisive segments of the course.

Background: Elite athletes are highly sedentary outside of sports and must stay active after retiring to remain healthy. While sports are often recommended to improve physical activity, the effect of sport training day on daily physical activity levels in adolescent athletes is not well described. The purpose was to assess (1) physical activity (i.e., step counts and activity score [METs]) and (2) sedentary behavior (e.g., total duration and prolonged [> 1 h] bouts) in male and female adolescent athletes across different training days (i.e., competition, practice, and rest days).

Methods: Adolescent basketball and volleyball athletes wore an accelerometer continuously for 14 consecutive days while in-season. Training days (i.e., competition, practice, and rest days) were tracked for each athlete. In-person testing included anthropometrics, vertical jump height, and body composition via bioelectrical impedance.

Results: Thirty-nine athletes (15.6 ± 0.9 years; n = 24 female, n = 15 male) participated. Athletes were more physically active on competition and practice days (step count [mean ± SD]: competition: 13,021 ± 2,572, practice: 11,735 ± 1,875, rest: 6,742 ± 3,150 [p < 0.001]); activity score [METs]: competition: 35.6 ± 1.0, practice: 34.7 ± 0.9, rest: 33.0 ± 1.3 [p < 0.001]). Athletes had high total sedentary behavior across all training days (competition: 570.4 ± 89.3 min, practice: 619.5 ± 74.6 min, rest: 638.5 ± 90.8 min [p = 0.001]), but the greatest prolonged bouts of sedentary behavior on competition days (competition: 195.4 ± 100.9 min, practice: 115.9 ± 74.0 min, rest: 144.6 ± 96.2 min [p = 0.002]).

Conclusion: Adolescent athletes were highly active on competition and practice days but did not meet physical activity guidelines on rest days, achieving only ~ 6,700 steps/day. Athletes were highly sedentary across all training days, averaging ~ 10 h/day of waking sedentary behavior. Only a third met physical activity guidelines regardless of training day. Adolescent athletes are highly sedentary and many fail to meet physical activity guidelines, challenging the notion that sports alone make individuals sufficiently active.

Clinical trial number: Not applicable.

Objectives: To explore the effect of early knee symptoms on the stages of change for regular exercise among young college students and its underlying mechanism using the transtheoretical model (TTM).

Methods: Electronic questionnaires on chronic and frequent knee symptoms, four constructs of TTM for regular exercise, and other variables were designed and distributed in 2022. Valid data was analyzed for 1111 young college student using descriptive statistics, chi-square tests, independent sample t-tests, MANOVA with post-hoc, and logistic regression models.

Results: The prevalence of knee symptoms was 17.37% (95% CI: 15.21 to 19.76). The distribution of exercise stages between students with and without knee symptoms was significantly different (χ² = 13.57, p = 0.01), and the total proportion of action and maintenance in students with knee symptoms (28.50%) was relatively higher than that in those without (19.83%). MANOVA showed ten processes of change, self-efficacy, pros and cons were significantly different across stages in students with knee symptoms (Pillai's Trace = 0.618, F = 2.516, p < 0.001) and in those without (Pillai's Trace = 0.317, F = 5.993, p < 0.001), and large effects size were only found for counterconditioning (η² = 0.15), self-liberation (η² = 0.17), self-efficacy (η² = 0.15), and pros (η² = 0.14) among students with knee symptom.

Conclusion: This study implied that early knee symptoms might prompt individuals to engage in and maintain regular exercise behaviors, that specifically enhanced the power of psychological and behavioral variables, especially of self-liberation, counterconditioning, self-efficacy and pros. Insights into the different patterns of constructs of TTM for exercise behavior among students with knee symptoms would be valuable for developing interventions. However, considering the relationship was associational rather than causal, and that reverse causality was possible, that was those who exercised regularly was more aware of their symptoms.