Effects of Strength Training on Sleep Parameters of Adolescents: A Randomized Controlled Trial.

ABSTRACT: Santiago, LCS, Lyra, MJ, Germano-Soares, AH, Lins-Filho, OL, Queiroz, DR, Prazeres, TMP, Mello, MT, Pedrosa, RP, Falcão, APST, and Santos, MAM. Effects of strength training on sleep parameters of adolescents: a randomized controlled trial. J Strength Cond Res 36(5): 1222-1227, 2022-This study aimed to examine the effects of 12 weeks of strength training (ST) on sleep quality and daytime sleepiness in adolescents with sleep complaints. Thirty adolescents were randomly assigned to 2 groups: ST group (ST, n = 18) and control group (CG, n = 12). Anthropometric, body composition, one-repetition maximum test, and sleep parameters (Pittsburgh Sleep Quality Index [PSQI] and Epworth Sleepiness Scale [ESS]) were evaluated. Training consisted of 55 min·d-1 (3 times a week, for 12 weeks), 3 sets of 10-12 repetitions with a 1-minute rest interval between sets and exercises. Baseline and postintervention differences were analyzed using Generalized Estimating Equations and the effect size (ES) with Cohen's d coefficient. Significance was set at (p < 0.05). After 12 weeks of ST, a significant decrease in the PSQI score (7.3 ± 0.7 vs. 5.1 ± 0.6; ES = 4.10) was observed in the ST group, but not in the CG (6.3 ± 0.8 vs. 7.4 ± 0.7; ES = 1.53). A significant decrease in ESS score was found in the ST group (10.1 ± 0.7 vs. 8.2 ± 0.7; ES = 3.08), without differences in the CG (10.7 ± 0.8 vs. 11.0 ± 0.7; ES = 0.56). The ST group presented increased total sleep duration (h·min-1) (6.2 ± 0.2 vs. 6.9 ± 0.2; ES = 3.60), but not the CG (7.0 ± 0.2 vs. 6.8 ± 0.1; ES = 1.32). Individual analyses showed ≈67% of adolescents experienced a reduction in PSQI (8.3; confidence interval [CI] 95% 6.8-10.1) and ESS (8.3; CI 95% 6.7-9.9) scores after ST, whereas only ≈17% of control subjects presented reduced scores (PSQI [11.1; CI 95% 9.5-12.9] and ESS [11.0; CI 95% 9.4-12.6]). Strength training improved sleep quality and increased total sleep duration.

The influence of anthropometric variables, body composition, propulsive force and maturation on 50m freestyle swimming performance in junior swimmers: An allometric approach.

The purpose of the current article was to use allometric models to identify the best body size descriptors and other anthropometric variables, body composition, and offset maturity that might be associated with the youngsters' 50m personal-best (PB) swim speeds (m·s-1). Eighty-five competitive swimmers (male, n=50; 13.5±1.8 y; female, n=35; 12.6±1.8 y) participated in this study. Height, body mass, sitting height, arm span, skinfolds, arm muscle area (AMA), and maturity offset were assessed. Swimming performance was taken as the PB time recorded in competition, and the propulsive force of their arm (PFA) was assessed by the tied swimming test. The multiplicative allometric model relating 50m PB swim speeds (m·s-1) to all the predictor variables found percentage body fat as a negative [(BF%) ß= -.121±.036; P=0.001], and PFA (PFA ß=.108±.033; P=0.001) and the girl's arm span (ß=.850±.301; P=0.006), all log-transformed, as positive significant predictors of log-transformed swim speed. The adjusted coefficient of determination, Radj2 was 54.8% with the log-transformed error ratio being 0.094 or 9.8%, having taken antilogs. The study revealed, using an allometric approach, that body fatness and PFA were significant contributors to 50m freestyle swim performance in young swimmers.

Anthropometric variables, propulsive force and biological maturation: A mediation analysis in young swimmers.

Youth swimming performance may be influenced by anthropometric and body composition factors during growth. Propulsive force of the arm (PFA) is highly related to swimming performance as 85-90% of the propulsive power comes from the arms. The current study analyzed the mediating effect of biological maturation on the relationship between anthropometric variables and body composition with PFA in young swimmers. A total of 128 swimmers [boys: n = 53, age = 13.6 (1.8) y; girls: n = 75, age = 12.5 (1.8) y] were evaluated. Propulsive force of the arm was estimated by the tethered swimming test. Anthropometric characteristics (body mass, stature, sitting height, arm span, arm muscle area, %body fat, and fat-free mass) were evaluated. Biological maturation was estimated by the age of peak height velocity. Mediation analyses were performed using the Preacher and Hayes bootstrapping method, adjusted for chronological age and sex. All anthropometric and body composition variables, except %body fat, were positively associated with PFA, being mediated by biological maturation. Indirect effects and 95% confidence intervals were: body mass [.20 (.09-.34)], stature [.22 (.11-.43)], arm span [0.17 (.05-.31)], arm muscle area [.74 (.38-1.19)] and fat free-mass [.17 (.05-.34)]. In conclusion, biological maturation mediated the positive associations between body size and composition and PFA in young swimmers.

The importance of body weight status on motor competence development: From preschool to middle childhood.

We evaluated the association between weight status and motor competence from preschool age (3-5 years of age) until middle childhood (7-9 years of age). Longitudinal study with three to five-year-old preschool children (n = 1155) enrolled in public and private preschools in Recife, Brazil. Children were followed twice (2010, 2012, and 2014) for four years. Köperkoordinationstest für kinder (KTK) assessed the children's motor competence (KTK Motor Quotient). Weight status (underweight, normal weight, overweight, and obesity) was classified according to the children's sex and age. Preschool children with normal weight exhibited higher motor competence at 5-7 years of age compared to preschool children with overweight (+3.73 MQ, P = .03) and obesity (+5.09 MQ, P < .01). Preschool children with normal weight presented higher motor competence at 7-9 years of age compared to their peers with overweight (+6.00 MQ, P = .03) and obesity (+5.88 MQ, P = .01). Children with normal weight at 5-7 years of age presented higher motor competence at 7-9 years of age compared to their peers with overweight (+3.33 MQ, P = .02) and obesity (+4.00 MQ, P = .02). Independent of the childhood phase and extension of the period evaluated (2- or 4-year period), children who had excessive weight (overweight or obesity) and changed their weight status to underweight or normal weight presented similar motor competence compared to children who continued underweight or normal weight. Weight status already at preschool age is an important predictor of the children's motor competence until middle childhood. Interventions improving the children's weight status, already at preschool age, might impact their motor competence development positively.

Association between sports participation, motor competence and weight status: A longitudinal study.

OBJECTIVES: The aim of this study was to investigate if baseline motor competence, weight status and sports participation in early childhood predict sports participation two years later. DESIGN: longitudinal study. METHODS: In 2010, motor competence (object control and locomotor skills), weight status and sports participation were assessed in 292 children between three and five years-of-age. In 2012, sports participation was re-evaluated in 206 of the original 292 children. Logistic regression was implemented to examine if initial sports participation, motor competence and weight status would predict sports participation two years later. RESULTS: In the final model, sports participation in 2010 (OR=9.68, CI: 3.46 to 27.13) and locomotor skills (OR=1.21, CI: 1.01 to 1.46) significantly predicted sports participation after two years. CONCLUSIONS: These results suggest that initial sports participation and more advanced locomotor skills in preschool years may be important to promote continued participation in sports across childhood.