Long-Term Alterations in Pulmonary V˙O2 and Muscle Deoxygenation On-Kinetics During Heavy-Intensity Exercise in Competitive Youth Cyclists: A Cohort Study

Purpose : The aim of this investigation was to assess alterations of pulmonary oxygen uptake ( ) and muscle deoxygenation on-kinetics during heavy-intensity cycling in youth cyclists over a period of 15 months. Methods : Eleven cyclists (initial age, 14.3 [1.6] y; peak , 62.2 [4.5] mL·min −1 ·kg −1 ) visited the laboratory twice on 3 occasions within 15 months. Participants performed an incremental ramp exercise test and a constant workrate test within the heavy-intensity domain during the first visit and second visit, respectively. Subsequently, parameter estimates of the and muscle deoxygenation on-kinetics were determined with mono-exponential models. Results : The phase II time constant decreased from occasion 1 (34 [4] s) to occasion 2 (30 [4] s, P = .005) and 3 (28 [4] s, P = .010). However, no significant alteration was observed between occasions 2 and 3 ( P = .565). The slow component amplitude either expressed in absolute values (ie, L·min −1 ) or relative to end exercise (ie, %) showed no significant changes throughout the study ( P = .972 and .996). Furthermore, the muscle deoxygenation on-kinetic mean response time showed no significant changes throughout the study (18 [8], 18 [3], and 16 [5] s for occasions 1, 2, and 3, respectively; P = .279). Conclusion : These results indicate proportional enhancements of local muscle oxygen distribution and utilization, which both contributed to the speeding of the on-kinetics herein.