Oxygen uptake during running as related to body mass in circumpubertal boys: a longitudinal study

Summary

To investigate the effect of endurance training on physiological characteristics during circumpubertal growth, eight young runners (mean starting age 12 years) were studied every 6 months for 8 years. Four other boys served as untrained controls. Oxygen uptake ($\dot V$ O ₂) and blood lactate concentrations were measured during submaximal and maximal treadmill running. The data were aligned with each individual's age of peak height velocity. The maximal oxygen uptake ($\dot V$ O _2max; ml · kg⁻¹ · min⁻¹) decreased with growth in the untrained group but remained almost constant in the training group. The oxygen cost of running at 15 km · h⁻¹ ($\dot V$ O ₂₁₅, ml · kg⁻¹ · min⁻¹) was persistently lower in the trained group but decreased similarly with age in both groups. The development of$\dot V$ O _2max and$\dot V$ O ₂₁₅ (1 · min⁻¹) was related to each individual's increase in body mass so that power functions were obtained. The mean body mass scaling factor was 0.78 (SEM 0.07) and 1.01 (SEM 0.04) for$\dot V$ O _2max and 0.75 (SEM 0.09) and 0.75 (SEM 0.02) for$\dot V$ O ₂₁₅ in the untrained and trained groups, respectively. Therefore, expressed as ml · kg^−0.75 · min⁻¹,$\dot V$ O ₂₁₅ was unchanged in both groups and$\dot V$ O _2max increased only in the trained group. The running velocity corresponding to 4 mmol · 1⁻¹ of blood lactate (ν _la4) increased only in the trained group. Blood lactate concentration at exhaustion remained constant in both groups over the years studied. In conclusion, recent and the present findings would suggest that changes in the oxygen cost of running and$\dot V$ O _2max (ml · kg⁻¹ · min⁻¹) during growth may mainly be due to an overestimation of the body mass dependency of$\dot V$ O ₀₂ during running. The$\dot V$ O ₂ determined during treadmill running may be better related to kg^0.75 than to kg¹.