The effect of the growth spurt on strength, power, speed and agility training in boys during mid-adolescence

Abstract

Four physical and motor fitness components are essential to excel in sport, namely muscle strength, speed, agility and explosive power. Size and performance differences which are associated with variation in biological maturation can contribute to performance differences during the adolescence period in boys. This period of rapid growth is also associated with a higher injury risk and temporary awkwardness. The aim of this study was twofold, firstly to determine to what extent speed and agility, and secondly strength and power are influenced by the growth spurt during mid-adolescence and whether negative influences of the growth spurt such as injuries and late development can be overcome by training during this period. The study formed part of two-year longitudinal research design based on a sample of convenience (N=68) consisting of boys in their grade 8 year with a mean age of 13.68 years ± SD at baseline measurements. A two-group pre-test post-test design was followed, where the experimental group (EG) of sport participants (n=47) was subjected to a strength, speed, power and agility sports training programme for the first six-months of every year and compared to a control group (CG) (n=39) of non-sport participants who was not exposed to any training programme. The experimental group and control group were also subdivided into three growth development groups, late developers (LD), early developers (ED) and typical developers (TD). Both the EG and CG underwent a fitness evaluation twice annually, representing a baseline and three additional time point measurements over the two-year period. This protocol consisted of thirteen tests including four anthropometric tests (stature, mass, sitting height and sitting height ratio, and fat percentage) and nine physical and motor fitness tests (10- and 40-meter speed, agility t-test, shuttle runs, vertical jump, horizontal jump, squats, sit-ups and seven-stage abdominal strength). The data was analysed by “Statistica for Windows” (StatSoft, 2015) and SAS 9.3 Level TS L1MO (2000–2010). Data was analysed descriptively while Spearman rank order correlations were done to determine relationships between changes in anthropometric and physical and motor fitness measurements. A hierarchical linear model was used to analyse the differences in growth and fitness among the three measuring points. Practical significance of differences was determined according to Cohen’s d-value 0.25 (small), 0.55 (medium), and 0.85 (large) (Cohen, 1992). The results revealed significant increases in height and weight in all the groups during every six-month period (p<0.05). Speed and agility increased nonlinearly (p<0.05) in both groups. Moderate correlations were found between changes in speed and agility and anthropometric measurements confirming an interrelationship during mid-adolescence between these variables. Both the EG and CG showed negative effects of growth on the development of speed and agility. Results indicated that the training programme had a positive effect on strength and power of TD and ED, with little or no effect on LD who had not reached their peak height velocity (PHV) yet. It is concluded from this study that the growth spurt influences the development of motor fitness capabilities such as speed, agility, strength and power in mid-adolescent boys at different stages of growth differently but that participation in a training programme can counter the negative effects of the growth spurt while also providing additional fitness benefits