Purpose: Peripheral and central factors play important roles in the reduction of motor performance following damaging eccentric exercise and delayed onset muscle soreness (DOMS). Following this regime, contralateral limbs could also be affected; however, the factors involved remain inconclusive. The purpose of this study was to distinguish the peripheral and central factors following eccentric contraction and DOMS of the plantar flexors in treated and contralateral homologous limbs. Methods: Ten males (BMI = 25.08 ± 1.69kgm-2; age = 28.70 ± 4.24 years) were randomly assigned to experimental (DOM) or control (CON) groups. The DOM group performed a damaging eccentric exercise, while the CON group rested. Plasma creatine kinase (CK), pain rating scale (PRS), muscle stiffness, maximal voluntary contraction (MVC), and neural voluntary activation (VA) were measured before, after 10 min, and after 24, 48, and 72 hr on treated and contralateral limbs. Results: Following exercise, CK increased until after 48 hr, while PRS increased until after 72 hr compared to the CON group. Importantly, MVC was reduced at all time points, with the greatest reduction observed after 24 hr (-16%), while VA was affected until after 48 hr, with the greatest reduction at after 10 min (-7%). Interestingly, a "cross-over effect" was observed in contralateral limbs when PRS, MVC, and VA were negatively affected following the same pattern (time line) as treated limbs (-13% peak MVC reduction; -3.5% peak VA reduction). Conclusion: These findings suggest a substantial central contribution to the reduction in force immediately following eccentric exercise and to a lesser extent during the latter part of DOMS in both treated and contralateral limbs.
Purpose: The present study examined whether groups of children with different physical fitness and fitness enjoyment profiles could be identified and, if so, whether the different groups varied from one another in terms of organized sports participation. Method: Five hundred and fifty-eight 8-11-year-olds (56.99% boys) participated in this cross-sectional study. Physical fitness and fitness enjoyment were assessed with seven items from a standardized test battery and a pictorial scale containing pictures referring to the enjoyment in those seven physical fitness tests, respectively. To examine whether groups with different fitness and enjoyment profiles could be identified, we conducted cluster analyses based on children's standardized physical fitness and fitness enjoyment scores. A two-way ANCOVA (sex*cluster) was conducted to investigate differences in weekly organized sports participation among each of the identified groups while controlling for age. Results: Cluster analyses revealed two groups with aligned levels of physical fitness and fitness enjoyment (i.e., relatively low-low and relatively high-high) and two groups with unaligned levels (i.e., relatively low-moderate and relatively high-moderate), respectively. Both groups with relatively high fitness scores were found to spend significantly more time in organized sports (M = 2.01 h and 2.29 h, respectively) than the two groups with relatively low fitness scores (M = 1.08 h and 0.98 h, respectively), irrespective of their enjoyment levels. Conclusion: Increasing physical fitness levels (especially among those children with suboptimal enjoyment levels) may lead to increased organized sports participation, while increased organized sports participation in its turn may lead to higher fitness levels. As such, participation in sports programs should be promoted in children of all age groups.
Purpose: Variability in accelerometry-data processing decisions limited data comparability across studies. We aimed to examine different accelerometry-data processing rules: varying bout lengths and allowance of 0- and 2-min interruptions on the total and bout-accumulated time spent in moderate-to-vigorous physical activity (MVPA) and sedentary behavior estimates, and describe the distribution of activity time based on counts per min (CPM) in granular categories. Method: Using the Singapore Health 2 survey, this study included 746 adults (41.8% women, median age 45.0 years) who provided valid ActiGraph GT3X+ accelerometer-data (≥4 valid days with ≥10-h/day). Quantile regression analysis adjusting for accelerometry daily wear time, age, and gender was performed to calculate the median and interquartile range of accelerometry estimates. Results: Median MVPA time accumulated in bouts of 1-min versus bouts of 10-min was 39.2 min/day and 6.0 min/day, respectively. MVPA time was higher when considering a 2-min interruption (range: 1.8-39.2 min/day) compared to 0-min interruption (range: 0-35.5 min/day) across bout lengths of 1- to 15-min. Participants were sedentary (≤100 CPM) for a daily median of 7.6 h/day. Median activities min/day on the lower-intensity activity spectrum (100-2499 CPM) decreased from 63.4 to 4.6 min/day, while on the higher-intensity activity spectrum (≥2500 CPM) was ≤2.9 min/day. Men generally spent more time in MVPA than women. Conclusions: This study highlights the differences in accelerometry estimates based on data processing decisions, and the importance of quantifying accelerometry-based activity time across the granular intensity spectrum. More studies are warranted to understand the determinants and health impact of these behaviors.