Exercise intensity and oxygen uptake kinetics in African-American and Caucasian women

Abstract

The effect of exercise intensity on the on- and off-transient kinetics of oxygen uptake (VO2) was investigated in African American (AA) and Caucasian (C) women. African American (n=7) and Caucasian (n=6) women of similar age, body mass index and weight, performed an incremental test and bouts of square-wave exercise at moderate, heavy and very heavy intensities on a cycle ergometer. Gas exchange threshold (LTGE) was lower in AA (13.6±2.3mL·kg−1min−1) than C (18.6±5.6mL·kg−1min−1). The dynamic exercise and recovery VO2 responses were characterized by mathematical models. There were no significant differences in 1) peak oxygen uptake (VO2peak) between AA (28.5±5mL kg−1min−1) and C (31.1±6.6mL kg−1min−1) and 2) VO2 kinetics at any exercise intensity. At moderate exercise, the on- and off- VO2 kinetics was described by a mono-exponential function with similar time constants τ1,on (39.4±12.5s;38.8±15s) and τ1,off (52.7±10.1s;40.7±4.4s) for AA and C, respectively. At heavy and very heavy exercise, the VO2 kinetics was described by a double-exponential function. The parameter values for heavy and very heavy exercise in the AA group were respectively: τ1,on (47.0±10.8;44.3±10s), τ2,on (289±63;219±90s), τ1,off (45.9±6.2;50.7±10s), τ2,off (259±120;243±93s) while in the C group were respectively: τ1,on (41±12;43.2±15s); τ2,on(277±81;215±36s), τ1,off (40.2±3.4;42.3±7.2s), τ2,off (215±133;228±64s). The on- and off-transients were symmetrical with respect to model order and dependent on exercise intensity regardless of race. Despite similar VO2 kinetics, LTGE and gain of the VO2 on-kinetics at moderate intensity were lower in AA than C. However, generalization to the African American and Caucasian populations is constrained by the small subject numbers.

Feasibility of a progressive protocol of high-intensity interval training for overweight/obese, sedentary African American women: a retrospective analysis

“…African American women possess lower cardiorespiratory fitness [ 14 , 15 ] and a higher prevalence of obesity [ 16 ] and insulin resistance [ 17 ] compared to their white counterparts and also tend to be less physically active [ 13 ]. To counteract the metabolic repercussions of these differences, lifestyle changes including caloric restriction and increased physical activity have been recommended [ 13 ].…”

“…For example, compared to their white counterparts, African American (AA) women are less physically active with time constraints specifically cited most frequently as the reason [ 13 ]. African American women also possess lower cardiorespiratory fitness (e.g., maximal rate of oxygen uptake and lactate threshold) [ 14 , 15 ] and a higher prevalence of obesity [ 16 ] and insulin resistance [ 17 ] compared to their white counterparts The lower oxidative capacity demonstrated by AA individuals appears to be linked to an increased percentage of type II muscle fibers [ 18 ], which are serially recruited during physical activity based on intensity of effort [ 19 ]. Interestingly, it was recently shown that 6 weeks of HIIT performed by previously-sedentary women resulted in increases in capillary density and mitochondrial content in both principal fibre types [ 20 ].…”

Gender differences inV̇O2and HR kinetics at the onset of moderate and heavy exercise intensity in adolescents

“…; Fawkner and Armstrong ; Lai et al. ). Nevertheless, in our study, τ 1 of adolescents appears closer to the adult rather than prepubertal children's response to both M and H. This could be related to the maturation level that was reported to affect V̇ O 2 kinetics (Babcock et al.…”

High-intensity interval training without weight loss improves exercise but not basal or insulin-induced metabolism in overweight/obese African American women

“…We chose this subject population because AA women have a higher incidence of obesity (39) and metabolic inflexibility (7) and lower cardiorespiratory fitness (e.g., V O 2max and LT) (40,52), peripheral insulin sensitivity, and mitochondrial capacity (17) compared with their white counterparts. AA women are also less physically active, with time constraints being the most frequently cited reason (18).…”