Skeletal maturity and oxygen uptake in youth soccer controlling for concurrent size descriptors

Interrelationships among skeletal maturity status, body size, ventilator thresholds (VT) and peak oxygen uptake (VO2peak) were considered in 47 adolescent male soccer players aged 12.5-15.4 years. Body mass, stature, and the triceps and subscapular skinfolds were measured. The latter were used to estimate fat mass and fat-free mass. Skeletal age was assessed with the Fels method. VO2peak and VO2 at the first (VT1) and second (VT2) ventilatory thresholds were determined during an incremental maximal exercise test on a motorized treadmill. Ratio standards and allometric models were used in the analysis. Scaling exponents suggested linearity for all combinations between size descriptors and physiological variables, except between log-transformed values of VT1 and body mass (mL·kg-0.801·min, 95%CI: 0.649 to 0.952). Early maturing players attained greater values than players classified as "on-time" in skeletal maturity for the three ventilatory parameters expressed in absolute terms (d ranged from 0.65 to 0.71). The differences were attenuated after normalizing for mass descriptors using ratio standards and scaled variables (d ranged from 0.00 to 0.31). The results suggested significant variability between maturity groups when moving from VT1 to maximal metabolic conditions expressed by unit of stature (VT1: t = -2.413, p = 0.02, d = 0.60; VT2: t = -2.488, p = 0.02, d = 0.65; VO2peak: t = -2.475, p = 0.02, d = 0.65). Skeletal maturity status and associated variation in overall body size affects VT1, VT2 and VO2peak. The observed scaling of ventilatory outputs for body size may be related to the better running economy and smaller body size of average maturing athletes.