Relating cardiorespiratory responses to work rate during incremental ramp exercise on treadmill in children and adolescents: sex and age differences

Purpose Evaluation of cardiopulmonary exercise testing (CPET) slopes such as d H R / d W R t o t (cardiac/skeletal muscle function) and d V ˙ O 2 / d W R t o t (O 2 delivery/utilization), using treadmill protocols is limited because the difficulties in measuring the total work rate ( W R t o t ). To overcome this limitation, we proposed a new method in quantifying W R t o t to determine CPET slopes. Methods CPET’s were performed by healthy patients, ( n = 674, 9–18 year) 300 female (F) and 374 male (M), using an incremental ramp protocol on a treadmill. For this protocol, a quantitative relationship based on biomechanical principles of human locomotion, was used to quantify the W R t o t of the subject. CPET slopes were determined by linear regression of the data recorded until the gas exchange threshold occurred. Results The method to estimate W R t o t was substantiated by verifying that: d V ˙ O 2 / d W R t o t for treadmill exercise corresponded to an efficiency of muscular work similar to that of cycle ergometer; d V ˙ O 2 / d W R t o t (mL min −1 W −1 ) was invariant with age and greater in M than F older than 12 years old (13–14 years: 9.6 ± 1.5(F) vs. 10.5 ± 1.8(M); 15–16 years: 9.7 ± 1.7(F) vs. 10.6 ± 2.2(M); 17–18 years: 9.6 ± 1.7(F) vs. 11.0 ± 2.3(M), p