Journal of Applied Physiology, Vol 62, Issue 6 2220-2223, Copyright © 1987 by American Physiological Society
Breathing pattern during exercise in young black and Caucasian subjects
F. J. Cerny
Lung volumes in sex-, age-, height-, and weight-matched Black subjects are
10-15% lower than those in Caucasians. To determine whether this decreased
lung volume affected the ventilatory adaptation to exercise, minute
ventilation (VE), its components, frequency (f) and tidal volume (VT), and
breathing pattern were observed during incremental cycle-ergometer
exercise. Eighteen Caucasian (age 8-30 yr) and 14 Black (age 8-25 yr)
subjects were studied. Vital capacity (VC) was lower (P less than 0.001) in
the Black subjects [90.6 +/- 8.6 (SD) vs. 112.9 +/- 9.9% predicted],
whereas functional residual capacity/total lung capacity was higher (P less
than 0.05). VE, mixed expired O2 and CO2, VT, f, and inspiratory (TI),
expiratory (TE), and total respiratory cycle (TT) duration were measured
during the last 30 s of each 2-min load. Statistical comparisons with
increasing power output were made at rest and from 0.6 to 2.4 W/kg in
0.3-W/kg increments. VE was higher in Blacks at all work loads and reached
significance (P less than 0.05) at 0.6 and 1.5 W/kg. VE/VO2 was also higher
throughout exercise, reaching significance (P less than 0.01) at 1.2, 1.5,
and 1.8 W/kg. The Black subjects attained any given level of VE with a
higher f (P less than 0.001) and lower VT. TI and TE were shortened
proportionately so that TI/TT was not different. Differences in lung volume
and the ventilatory response to exercise in these Black and Caucasian
subjects suggest differences in the respiratory pressure-volume
relationships or that the Black subjects may breathe higher on their
pressure-volume curve.
