Oxygen Uptake Kinetics in Trained Female Adolescents

Abstract

Little evidence exists with regard to the effect that exercise training has upon oxygen uptake kinetics in female adolescents. PURPOSE: The aim of the study was to compare VO2 and muscle deoxygenation kinetics in a group of trained (Tr) and untrained (Utr) female adolescents. METHODS: Twelve trained (6.4 ± 0.9 years training, 10.3 ± 1.4 months per year training, 5.2 ± 2.0 hours per week) adolescent female soccer players (Age: 14.6 ± 0.7 years) were compared to a group (n=8) of recreationally active adolescent girls (Age: 15.1 ± 0.6 years) of similar maturity status. Subjects underwent two, 6-min exercise transitions at a workload equivalent to 80% of lactate threshold from a 3-min baseline of 10W. All subjects had a passive rest period of 45-min between each square-wave transition. Breath-by-breath oxygen uptake and muscle deoxygenation (deoxyhaemoglobin signal from near infrared spectroscopy) were measured throughout the square wave transitions and were modeled via a monoexponential decay with a delay relative to the start of exercise. RESULTS: Peak VO2 was significantly (p<0.05) greater in the Tr compared to the Utr (Tr: 43.2 ± 3.2 mL·kg-1min-1 vs. Utr: 34.6 ± 4.0 mL·kg-1min-1). The time constant of the VO2 on-kinetics was significantly (p<0.05) faster in the Tr compared to the Utr (Tr: 26.3 ± 6.9 s vs. Utr: 35.1 ± 11.5 s). There was no inter-group difference in the time constant for muscle deoxygenation kinetics (Tr: 8.54 ± 3.0 s vs. Utr: 12.4 ± 8.3 s). CONCLUSION: The evidence from the present study suggests that exercise training and/or genetic self-selection results in faster on-kinetics in trained adolescent females. The lack of difference in muscle deoxygenation kinetics suggests that cardiovascular and peripheral adaptations were similarly responsible for the faster on-kinetics noted in the trained adolescent females.