You are looking at 141 - 150 of 1,626 items for :

  • Sport and Exercise Science/Kinesiology x
  • Pediatric Exercise Science x
  • Refine by Access: All Content x
Clear All
Restricted access

Neuromuscular Fatigue After Long-Duration Adventure Racing in Adolescent Athletes

Anthony Birat, Yoann M. Garnier, Pierre Bourdier, Alexis Dupuy, Alexandre Dodu, Claire Grossoeuvre, Anne-Charlotte Dupont, Anthony J. Blazevich, Mélanie Rance, Claire Morel, Stéphane Nottin, and Sébastien Ratel

Purpose: To characterize the acute effects of a long-duration adventure race on knee extensor (KE) fatigue and the knee functional ratio in adolescent athletes. Methods: Twenty trained male adolescents (aged 14–17 y) performed an adventure race of 68.5 km. Maximal voluntary isometric contraction (MVIC) KE and knee flexor torques were measured before and immediately after the race. Central and peripheral components of neuromuscular fatigue were quantified from the maximal voluntary activation level and the doublet peak torque (Tw100), respectively. The peak eccentric knee flexor torque to concentric KE torque ratio was also measured to determine functional ratio. Results: The race completion time was 05:38 (00:20) hours. Significant reductions in MVICKE (−14.7%, P < .001) and MVICKF (−17.0%, P < .01) were observed after the race. Voluntary activation level decreased by 8.3% (P < .001) while Tw100 remained unchanged. Peak eccentric knee flexor torque decreased 16.0% (P < .001) while peak concentric KE torque did not change. This resulted in a significant reduction in functional ratio (−12.0%, P < .01). Conclusion: The adventure race induced a moderate fatigue, which was mainly explained by central factors without significant peripheral fatigue. However, particular attention should be paid to the knee muscular imbalance incurred by the race, which could increase the risk of ligament injury in adolescent athletes.

Restricted access

Volume 33 (2021): Issue 2 (May 2021)

Restricted access

The Effects of Exercise Serum From Prepubertal Girls and Women on In Vitro Myoblast and Osteoblast Proliferation and Differentiation

Yasmeen Mezil, Joyce Obeid, Inna Ushcatz, Sandeep Raha, and Brian W. Timmons

Purpose: In girls and women, the authors studied the effects of an acute bout of low-impact, moderate-intensity exercise serum on myoblast and osteoblast proliferation in vitro. Methods: A total of 12 pre/early pubertal girls (8–10 y old) and 12 women (20–30 y old) cycled at 60% VO2max for 1 hour followed by 1-hour recovery. Blood samples were collected at rest, mid-exercise, end of exercise, mid-recovery, and end of recovery. C2C12 myoblasts and MC3T3E1 osteoblasts were incubated with serum from each time point for 1 hour, then monitored for 24 hours (myoblasts) or 36 hours (osteoblasts) to examine proliferation. Cells were also monitored for 6 days (myoblasts) to examine myotube formation and 21 days (osteoblasts) to examine mineralization. Results: Exercise did not affect myoblast or osteoblast proliferation. Girls exhibited lower cell proliferation relative to women at end of exercise (osteoblasts, P = .041; myoblasts, P = .029) and mid-recovery (osteoblasts, P = .010). Mineralization was lower at end of recovery relative to rest (P = .014) in both girls and women. Myotube formation was not affected by exercise or group. Conclusion: The systemic environment following one acute bout of low-impact moderate-intensity exercise in girls and women does not elicit osteoblast or myoblast activity in vitro. Differences in myoblast and osteoblast proliferation between girls and women may be influenced by maturation.

Restricted access

Reciprocal Longitudinal Relationship Between Fitness, Fatness, and Metabolic Syndrome in Brazilian Children and Adolescents: A 3-Year Longitudinal Study

Cézane Priscila Reuter, Caroline Brand, João Francisco de Castro Silveira, Letícia de Borba Schneiders, Jane Dagmar Pollo Renner, Letícia Borfe, and Ryan Donald Burns

Purpose: To verify the reciprocal longitudinal relationships between cardiorespiratory fitness (CRF), percentage body fat (%body fat), and metabolic syndrome in Brazilian primary school students. Method: This longitudinal study involved 420 children and adolescents followed for 3 years (2011–2014). The continuous Metabolic Syndrome (cMetSyn) score was calculated by summing adjusted z scores of glucose, systolic blood pressure, total cholesterol/high-density lipoprotein cholesterol ratio, triglycerides, and waist circumference. The CRF was assessed using running/walking tests, and %body fat was assessed through sex-specific 2-site skinfold thickness. Cross-lagged panel models were used to analyze longitudinal reciprocal relationships between CRF and %body fat with cMetSyn. Results: Results indicated that 2011 %body fat significantly predicted both 2014 CRF scores and 2014 cMetSyn scores (P < .001); however, 2011 CRF only predicted 2014 %body fat (P < .001) but not 2014 cMetSyn (P = .103). Furthermore, 2011 cMetSyn predicted 2014 %body fat (P = .002). The model explained 36%, 48%, and 37% of the variance in 2014 CRF, %body fat, and cMetSyn, respectively. Conclusion: The results suggest a reciprocal inverse relationship between %body fat and metabolic syndrome risk and that %body fat may play a more important role in the risk of developing metabolic syndrome compared with CRF.

Restricted access

The Effect of Growth Hormone Treatment on Physical Performance Indices in Children With Idiopathic Short Stature

Adi Weinberg, Nitzan Dror, Katya Motin, Michal Pantanowitz, Dan Nemet, and Alon Eliakim

Purpose: To examine the effect of growth hormone (GH) treatment on physical performance in children with idiopathic short stature and normal GH secretion. Materials and Methods : A total of 24 children participated in the study (13 GH-treated, 11 non-treated, aged 8–13 y, 11 males and 13 females, Tanner stage 1–2). Participants performed a battery of motor skill performance tests (Eurofit), as well as the Wingate anaerobic test. Results: No statistically significant differences in any of the Eurofit physical fitness test results (eg, 20-m shuttle run 33.0 [15.1] vs 25.1 [21.0] laps in treated and nontreated participants, respectively, P = .25) or the Wingate anaerobic test were found between the groups (eg, peak power 5.0 [2.9] vs 3.9 [2.6] watts/kg in treated and nontreated participants, respectively, P = .2). Conclusions: Therapeutic usage of exogenous GH for pre and early pubertal children with idiopathic short stature and normal GH secretion was not associated with beneficial effects on physical performance indices. This suggests that the use of GH as a potential performance enhancing agent, in this age group, at least at commonly used doses, is not advantageous.

Restricted access

Leading by Example: Association Between Mother and Child Objectively Measured Physical Activity and Sedentary Behavior

Brad R. Julius, Amy M.J. O’Shea, Shelby L. Francis, Kathleen F. Janz, and Helena Laroche

Purpose: The authors examined the relationship between mother and child activity. Methods: The authors compared moderate–vigorous physical activity (MVPA) and sedentary time of low-income mothers with obesity and their 6- to 12-year-old children on week (WD) and weekend (WE) days. A total of 196 mother–child pairs wore accelerometers simultaneously for a week. Mothers completed questionnaires. Spearman correlation and multivariate regression were used. Results: WE MVPA (accelerometry) was significantly correlated between mothers with children aged 6–7 (r s = .35) and daughters (r s = .27). Self-reported maternal PA time spent with one of their children was significantly correlated with the WE MVPA of all children (r s = .21) and children aged 8–10 (r s = .22) and with the WD MVPA of all children (r s = .15), children aged 8–10 (r s = .23), aged 11–12 (r s = .52), and daughters (r s = .37), and inversely correlated to the WD sedentary time of all children (r s = −.21), children aged 8–10 (r s = −.30), aged 11–12 (r s = −.34), daughters (r s = −.26), and sons (r s = −.22). In multivariate regression, significant associations were identified between reported child–mother PA time together and child MVPA and sedentary time (accelerometry). Conclusions: Mothers may influence the PA levels of their children with the strongest associations found in children aged 6–7 and daughters. Mother–child coparticipation in PA may lead to increased child MVPA and decreased sedentary behavior.

Restricted access

Impact of COVID-19 on School-Aged Male and Female Health-Related Fitness Markers

Zachary Wahl-Alexander and Clayton L. Camic

Purpose: The purpose of this study was to examine the impact of the Coronavirus disease 2019 on male and female anthropometric variables and physical performance. Methods: This study utilized a mixed (time [PRE vs POST], gender [male vs female]) methods design to examine changes in the body mass index and physical fitness performance measures prior to and following closures. Data were collected from 264 third through eighth graders. This sample consisted of 131 males and 133 females. The data was collected through anthropometric (body mass index) and physical performance measures and was analyzed with separate 2 × 2 mixed-factorial analyses of variance (time [PRE, POST] × gender [male, female]). Results: The findings indicated both males and females exhibited mean increases in the body mass index (+10.6%; 18.8–20.8 kg·m−2, P < .001, partial η 2 = .627) and decreases in push-ups (−35.6%; 7.3–4.7 repetitions, P < .001, partial η 2 = .371), sit-ups (−19.4%; 22.7–18.3 repetitions, P < .001, partial η 2 = .420), and the Progressive Aerobic Cardiovascular Endurance Run test (−26.7%; 31.4–22.4 laps, P < .001, partial η 2 = .644) scores from PRE to POST. Conclusion: The results of this study demonstrate that both males and females exhibited significant anthropometric and physical performance losses during the Coronavirus disease 2019 shutdown.

Restricted access

Low Muscular Strength, Weight Status, and Metabolic Syndrome in Adolescents: National Health and Nutrition Examination Survey 2011–2014

Nicholas M. Pilli, Tyler J. Kybartas, Kristen M. Lagally, and Kelly R. Laurson

Purpose: To investigate the association between muscular strength and metabolic syndrome (MetS), with a specific focus on the role of weight status, using a nationally representative sample of US youth. Methods: The analysis included 409 boys and 415 girls from the 2011 to 2014 National Health and Nutrition Examination Survey between 12 and 18 years of age. The prevalence of MetS was defined using age- and sex-specific criteria for abdominal obesity, elevated triglycerides, blood pressure, fasting glucose, and low high-density lipoprotein (HDL) cholesterol. Strength was assessed via handgrip dynamometer and expressed as age- and sex-specific z scores of relative strength. Low strength was defined as a relative strength below the 25th percentile. Analyses controlled for age, sex, race/ethnicity, physical activity, and weight status. Results: The sample prevalence of MetS was approximately 5.3%. However, MetS prevalence was 18.5% in overweight/obese youth with low strength. The adjusted odds of MetS were 3.1 (95% confidence interval, 1.5–6.3, P < .001) times higher for overweight/obese youth with low strength versus sufficient strength. Conclusion: Muscular strength is predictive of adolescent MetS, specifically in those with unhealthy weight status. Approximately one in 5 overweight/obese youth with low strength had MetS. These findings highlight the relevance of muscular strength in youth cardiometabolic morbidities.

Restricted access

Carbohydrate Drink Use During 30 Minutes of Variable-Intensity Exercise Has No Effect on Exercise Performance in Premenarchal Girls

C. Eric Heidorn, Brandon J. Dykstra, Cori A. Conner, and Anthony D. Mahon

Purpose: This study examined the physiological, perceptual, and performance effects of a 6% carbohydrate (CHO) drink during variable-intensity exercise (VIE) and a postexercise test in premenarchal girls. Methods: A total of 10 girls (10.4 [0.7] y) participated in the study. VO2peak was assessed, and the girls were familiarized with VIE and performance during the first visit. The trial order (CHO and placebo) was randomly assigned for subsequent visits. The drinks were given before VIE bouts and 1-minute performance (9 mL/kg total). Two 15-minute bouts of VIE were completed (10 repeated sequences of 20%, 55%, and 95% power at VO2peak and maximal sprints) before a 1-minute performance sprint. Results: The mean power, peak power, heart rate (HR), %HRpeak, and rating of perceived exertion during VIE did not differ between trials. However, the peak power decreased, and the rating of perceived exertion increased from the first to the second bout. During the 1-minute performance, there were no differences between the trial (CHO vs placebo) for HR (190 [9] vs 189 [9] bpm), %HRpeak (97.0% [3.2%] vs 96.6% [3.0%]), rating of perceived exertion (7.8 [2.3] vs 8.1 [1.9]), peak power (238 [70] vs 235 [60] W), fatigue index (54.7% [10.0%] vs 55.9% [12.8%]), or total work (9.4 [2.6] vs 9.4 [2.1] kJ). Conclusion: CHO supplementation did not alter physiological, perceptual, or performance responses during 30 minutes of VIE or postexercise sprint performance in premenarchal girls.

Restricted access

Lifestyle Behaviors Associated With Body Fat Percent in 9- to 11-Year-Old Children

Nils Swindell, Damon Berridge, Melitta A. McNarry, Kelly A. Mackintosh, Lynne M. Boddy, Stuart J. Fairclough, and Gareth Stratton

Purpose:To examine (1) associations between body fat percent (BF) and lifestyle behaviors in children aged 9–11 years and (2) the consistency of these associations over a 10-year period. Methods: In this repeat, cross-sectional study, 15,977 children aged 9–11 years completed an anthropometric assessment and the SportsLinx Lifestyle survey between 2004 and 2013. Body fat was estimated according to the sum of the triceps and subscapular skinfold measurements. Multilevel models were utilized to examine associations between BF and responses to the lifestyle survey while controlling for known covariates. Results: Lifestyle behaviors explained 8.6% of the total variance in body fat. Specifically, negative associations were found between BF and active transport to school ( β = −0.99 [0.19], P < .001), full-fat milk (−0.07 [0.15], P < .001), and sweetened beverage consumption (−0.40 [0.15], P = .007). Relative to the reference group of ≤8:00 PM, later bedtime was positively associated with BF: 8:00 to 8:59 PM ( β = 1.60 [0.26], P < .001); 9:00 to 10:00 PM ( β = 1.04 [0.24], P < .001); ≥10:00 PM ( β = 1.18 [0.30], P < .001). Two-way interactions revealed opposing associations between BF and the consumption of low-calorie beverages for boys ( β = 0.95 [0.25], P < .001) and girls ( β = −0.85 [0.37], P = .021). There was no significant change in these associations over a 10-year period. Conclusions: In this population-level study covering a decade of data collection, lifestyle behaviors were associated with BF. Policies and interventions targeting population-level behavior change, such as active transport to school, sleep time, and consumption of full-fat milk, may offer an opportunity for improvements in BF.