The Influence of Biological Maturation on Fat and Carbohydrate Metabolism during Exercise in Males

Abstract

This study examined substrate use during exercise in early-pubertal (EP), mid-pubertal (MP), late-pubertal (LP), and young-adult (YA) males. Fuel use was calculated using the RER and VO2 response during cycling exercise at 30 to 70% of VO2speak. Significant group by intensity interactions were found for lactate, RER, percent CHO, and fat use, in addition to fat and CHO oxidation rates, which suggest a maturation effect on substrate use during exercise. While significance was not achieved at all intensities, post hoc analyses revealed greater fat use, lower CHO use, and lower lactate concentrations in EP and MP compared to LP or YA. No differences were noted between EP and MP or LP and YA at any intensity, suggesting the development of an adult-like metabolic profile occurs between mid- to late-puberty and is complete by the end of puberty.

The Influence of Maturation on the Oxygen Uptake Efficiency Slope

“…As exercise intensity increases, so does the relative contribution of carbohydrate to energy expenditure, which is reflected in increasing RER values. This relationship is consistent in both adults and children; however, lower RER values for a given submaximal relative exercise intensity are reported for children (14) and relative fat and carbohydrate usage has been demonstrated to be affected by maturation through early puberty to adolescence (73).…”

“…Lower carbohydrate utilization in children could also be explained by children's decreased capacity to utilize carbohydrate sources, as lower concentrations of an important glycolytic enzyme, phosphofructose kinase, were observed in boys compared to men (35), but this finding is not universally supported in the literature (43). Consistent with the lower submaximal exercise RER values, blood lactate concentrations for a given exercise intensity are lower in children as well (54); Lower RER values are also observed in children compared to adults (73), and as such should be considered when evaluating maximal exercise response criteria between the two populations.…”

“…Forty three male subjects from a previous study at the Ball State Human Performance Laboratory formed half of the subject pool (73). Additional subjects , a range typical for children of this cohort and recreationally active adults (12,21).…”

“…Other factors that influence the RER response to exercise include aerobic fitness (25,27), prior exercise (4), and maturation (14,73).…”

Sport Nutrition and Youth

“…However, increasing muscle glycogen stores through CHO loading may benefit male adolescents during the later stages of puberty (Tanner stage 4 and 5) when the metabolic profile is similar to that of adult men (Riddell et al 2008;Stephens et al 2006;Timmons et al 2007a). Furthermore, as noted in section 4, training resulted in an increased capacity to store and use glycogen in boys (Eriksson et al 1973); thus, young athletes who train regularly may exhibit an ability to increase their glycogen stores through CHO loading, with potential effects on performance.…”