Cardiovascular responses in black and white males during exercise

Abstract

Previous investigations have shown blacks to have a significantly lower resting heart rate (HR) compared with whites. Our purpose was to determine if this difference exists during submaximal exercise and to compare other cardiovascular responses during submaximal exercise in black and white males. Sixteen black and 16 white males matched on age, body surface area, and maximal O2 consumption exercised at 0, 50, and 100 W on a cycle ergometer. HR, O2 consumption, and cardiac output via CO2 rebreathing were measured at rest and at each work rate. Stroke volume was then calculated. O2 consumption was not significantly different between blacks and whites at rest or at work rates of 0, 50, or 100 W. Cardiac output increased from rest with 0, 50, and 100 W work for both blacks and whites (6.1 to 13.0, 14.4, and 16.9 l/min and 5.7 to 12.2, 14.3, and 16.3 l/min, respectively). The differences in cardiac output between blacks and whites at rest and all work rates were not statistically significant. At rest and work rates of 0, 50, and 100 W, HR was significantly lower in blacks compared with whites (71, 99, 108, and 119 beats/min vs. 80, 107, 114, and 127 beats/min, respectively). The lower HR in blacks compared with whites was accompanied by a trend toward a higher stroke volume at rest and work rates of 0, 50, and 100 W (85.2, 130.3, 134.7, and 142.9 ml vs. 72.5, 114.9, 126.4, and 127.4 ml, respectively). No differences in resting blood pressures were found.(ABSTRACT TRUNCATED AT 250 WORDS)

Estimating stroke volume from oxygen pulse during exercise

“…Linear regression applied to a-vO 2 D ic reveals that this parameter increased linearly throughout exercise, with a slope of (0.86 ± 0.03 ml/100 ml)%W max and an intercept of 6.8 ± 0.2 ml/100 ml (r 2 = 0.98 and p < 0.01). The increase in CO ic per litre increase in V O 2 was on average 5.1 ± 0.3 l min −1 , in good agreement with previous published data (Berry et al 1993, Crisafulli et al 2005, 2006a, Lewis et al 1983, Proctor et al 1998. Obviously, a-vO 2 D est showed a perfect linear increase, with a slope of (0.89 ml/100 ml)%W max .…”

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

“…Therefore, it is possible that central and peripheral factors related to the ability of the cardiovascular and skeletal muscle systems to deliver oxygen to mitochondria may have influenced the dynamics of the VO 2 recovery (Berry et al 1993; Hunter et al 2001; Roy et al 2006; Vehrs et al 2006). While a reduced VO 2peak found in African American women compared to Caucasian women was correlated with a lower hemoglobin content and aerobic capacity in the African Americans (Hunter et al 2001; Roy et al 2006), a different study (Berry et al 1993) found no racial difference in the cardiac output response to exercise while heart rate was lower in African Americans than in Caucasians. However, there is no clear evidence of racial group differences in exercise performance as measured by maximal aerobic power (Boulay et al 1988; di Prampero and Cerretelli 1969).…”

“…While few studies have investigated VO 2 kinetics in women (Regensteiner et al 1998; Stathokostas et al 2009), even less attention has been given to potential VO 2 kinetics differences between African American and Caucasian women. In the African American population, the characterization of on- and off- kinetics was obtained only in male adolescents (Lai et al, 2008) while other studies investigated racial differences in a) muscle oxidative capacity in women (Hickner et al, 2001; Hunter et al 2001; Roy et al 2006; Sirikul et al 2006); and b) cardiovascular response in children of both sexes (Trowbridge et al 1997) and in adult males (Berry et al 1993; Vehrs et al 2006). The maximal oxygen consumption (VO 2max ) observed in healthy children (Trowbridge et al 1997) and women (Hunter et al 2001; Roy et al 2006; Sirikul et al 2006) was lower in African Americans than in Caucasians regardless of the level of physical activity.…”

“…Neither lactate threshold nor the effect of exercise intensity on VO 2 kinetics was investigated in any of these studies (Berry et al 1993; Chitwood et al, 1996; Cortright et al, 2006; Hickner et al, 2003; Hunter et al 2001; Roy et al 2006; Sirikul et al 2006; Vehrs et al 2006; Suminski et al, 2000). Lactate or gas exchange threshold (LT GE ) is often used in combination with VO 2max measurement to characterize aerobic fitness and endurance performance.…”