title: Gender differences in V˙O2 and HR kinetics at the onset of moderate and heavy exercise intensity in adolescents.
abstract: The majority of the studies on V˙O2 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 V˙O2 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 V˙O2 kinetics of the male group was previously analyzed (Lai et al., Appl. Physiol. Nutr. Metab. 33:107-117, 2008b). For both genders, V˙O2 and HR kinetics were described with a single exponential at M and a double exponential at H. The fundamental time constant (τ1) of V˙O2 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 (G1) 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-1W-1, respectively. The amplitude of the slow component was not significantly different between genders. The HR kinetics were significantly (τ1, 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 G1of HR was higher in females than males at M: 0.53 ± 0.11 versus 0.98 ± 0.2 bpm W-1and H: 0.40 ± 0.11 versus 0.73 ± 0.23 bpm W-1, respectively. Gender differences in the V˙O2 and HR kinetics suggest that oxygen delivery and utilization kinetics of female adolescents differ from those in male adolescents.
authors.affiliation: Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio Department of Pediatrics Cardiology, Case Western Reserve University, Cleveland, Ohio Center for Modeling Integrated Metabolic Systems, Cleveland, Ohio Department of Electrical and Computer Engineering, Old Dominion University, Norfolk, Virginia Biomedical Engineering Institute, Old Dominion University, Norfolk, Virginia nlai@odu.edu.
authors.forename: Nicola
authors.initials: N
authors.lastname: Lai
authors.affiliation: Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Martis
authors.affiliation: Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Belfiori
authors.affiliation: Center for Modeling Integrated Metabolic Systems, Cleveland, Ohio.
authors.forename: Fatima
authors.initials: F
authors.lastname: Tolentino-Silva
authors.affiliation: Department of Pediatrics Cardiology, Case Western Reserve University, Cleveland, Ohio Rainbow Babies and Children's Hospital, Cleveland, Ohio.
authors.forename: Melita M
authors.initials: MM
authors.lastname: Nasca
authors.affiliation: Department of Pediatrics Cardiology, Case Western Reserve University, Cleveland, Ohio Rainbow Babies and Children's Hospital, Cleveland, Ohio.
authors.forename: James
authors.initials: J
authors.lastname: Strainic
authors.affiliation: Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio Department of Pediatrics Cardiology, Case Western Reserve University, Cleveland, Ohio Center for Modeling Integrated Metabolic Systems, Cleveland, Ohio Rainbow Babies and Children's Hospital, Cleveland, Ohio.
authors.forename: Marco E
authors.initials: ME
authors.lastname: Cabrera
keywords: African American; adolescents; exercise; heart rate; kinetics; modeling; pulmonary O2 uptake