Gender differences in [Formula: see text] and HR kinetics at the onset of moderate and heavy exercise intensity in adolescents

The majority of the studies on [Formula: see text] kinetics in pediatric populations investigated gender differences in prepubertal children during submaximal intensity exercise, but studies are lacking in adolescents. The purpose of this study was to test the hypothesis that gender differences exist in the [Formula: see text] and heart rate (HR) kinetic responses to moderate (M) and heavy (H) intensity exercise in adolescents. Twenty‐one healthy African‐American adolescents (9 males, 15.8 ± 1.1 year; 12 females, 15.7 ± 1 year) performed constant work load exercise on a cycle ergometer at M and H. The [Formula: see text] kinetics of the male group was previously analyzed (Lai et al., Appl. Physiol. Nutr. Metab. 33:107–117, 2008b). For both genders, [Formula: see text] and HR kinetics were described with a single exponential at M and a double exponential at H. The fundamental time constant (τ (1)) of [Formula: see text] was significantly higher in female than male at M (45 ± 7 vs. 36 ± 11 sec, P < 0.01) and H (41 ± 8 vs. 29 ± 9 sec, P < 0.01), respectively. The functional gain (G(1)) was not statistically different between gender at M and statistically higher in females than males at H: 9.7 ± 1.2 versus 10.9 ± 1.3 mL min(−1) W(−1), respectively. The amplitude of the slow component was not significantly different between genders. The HR kinetics were significantly (τ (1), P < 0.01) slower in females than males at M (61 ± 16 sec vs. 45 ± 20 sec, P < 0.01) and H (42 ± 10 sec vs. 30 ± 8 sec, P = 0.03). The G(1) of HR was higher in females than males at M: 0.53 ± 0.11 versus 0.98 ± 0.2 bpm W(−1) and H: 0.40 ± 0.11 versus 0.73 ± 0.23 bpm W(−1), respectively. Gender differences in the [Formula: see text] and HR kinetics suggest that oxygen delivery and utilization kinetics of female adolescents differ from those in male adolescents.