Abstract
Much of the evidence examining temporal trends in fitness among youth has found a decrease in measures of muscular strength and muscular power over recent decades. The aim of this study was to examine trends in lower body muscular power in Spanish boys over 47 years. In 1969 140 boys (10–11 years; body mass index = 19.24, SD = 2.91 kg/m2) and in 2016, 113 boys (10–11 years; body mass index = 19.20, SD = 3.15 kg/m2) were recruited. Lower body power was assessed using the vertical jump (VJ) and standing long jump (SLJ) tests. Significant differences and a large effect size were shown between groups in the SLJ (p = 0.001; d = 0.94) and the VJ (p = 0.001; d = 0.66). SLJ data in 1969 were higher (1.52 m, SD = 0.19) when compared to the 2016 data (1.34 m, SD = 0.18). The VJ performance of the 1969 sample was also higher (25.95 cm; SD = 6.58) than the 2016 sample (21.56 cm; SD = 4.72). SLJ and VJ performance of the 2016 group decreased 11.8% and 16.9%, respectively. There were no significant differences between groups in body mass index. The results indicate a secular decline in lower body muscular power in 10–11-year-old Spanish boys with no significant changes in body mass index over the 47-year study period.
Highlights
Low levels of muscular fitness in children and adolescents are associated with poor motor competence, functional limitations and adverse health outcomes [1,2]
Sandercock and Cohen reported a decline in muscular fitness using allometric equations in 10-year-old English children from 1998 to 2014, and noted this trend was independent of secular changes in body size [5]
Body mass index (BMI) was calculated as body mass measured on an analogic scale to the nearest 0.1 kg divided by height measured on a stadiometer to the nearest 0.5 cm squared
Summary
Low levels of muscular fitness (i.e., muscular strength, muscular power and local muscular endurance) in children and adolescents are associated with poor motor competence, functional limitations and adverse health outcomes [1,2]. A recent meta-analysis concluded that poor muscular fitness was associated with lower levels of bone mineral density and self-esteem, as well as higher levels of body fat and cardiometabolic risk [1]. In support of these observations, lower handgrip levels in youth with obesity have been associated with increased cardiometabolic risk [10]. Low levels of performance on selected measures of muscular fitness, including the handgrip, push-up and long jump early in life have been found to be associated with an increased risk of metabolic syndrome later in life [11]. The long jump is a field test commonly used in youths as a general measure of lower body muscular fitness [12]
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