Breathing pattern during exercise in young Black and Caucasian subjects

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 (V̇(E)), its components, frequency (f) and tidal volume (V(T)), 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 < 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 < 0.05). V̇(E), mixed expired O₂ and CO₂, V(T), f, and inspiratory (T(I)), expiratory (T(E)), and total respiratory cycle (T(T)) 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. V̇(E) was higher in Blacks at all work loads and reached significance (P < 0.05) at 0.6 and 1.5 W/kg. V̇(E)/V̇(O₂) was also higher throughout exercise, reaching singificance (P < 0.01) at 1.2, 1.5, and 1.8 W/kg. The Black subjects attained any given level of V̇(E) with a higher f (P < 0.001) and lower V(T). T(I) and T(E) were shortened proportionately so that T(I)/T(T) 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.