Smoking Effect on Exercise Response Kinetics of Oxygen Uptake and Related Variables

Abstract

The effects of smoking on the kinetics of oxygen uptake (V̇O₂), carbon dioxide production (V̇O₂), ventilation (Ve) and heart rate (HR) in the transition from rest to steady-state submaximal exercise was investigated in 6 female and 4 male smokers (32 ± 8 yrs). The subjects underwent two counter-balanced treadmill tests at 60% of their maximal V̇O₂, lasting 10 min each: one following a 24-hr smoking abstinence, and one immediately after smoking three cigarettes without prior abstinence. Physiological variables were measured at rest and every 30 sec throughout each test. The time required for a given variable to rise from its respective resting baseline to half of its steady-state value (t_1/2) was calculated for V̇O₂, V̇CO₂, Ve and HR. Smoking abstinence was associated with t_1/2 values of 32 ± 8, 42± 12, 43 ± 10, and 30 ± 9 sec for V̇O₂, V̇CO₂, Ve, and HR, respectively. Smoking significantly (p < 0.01) lengthened those values to 51 ± 12, 58 ± 11, 54 ± 8, and 41 ± 10 sec. Concurrently, smoking raised the baseline (resting) values of HR (p < 0.01) and of Ve, V̇CO₂, O₂ pulse (O₂P), and both systolic and diastolic blood pressures (p < 0.05). During steady-state exercise only HR values were elevated by smoking (p < 0.01), while O₂P values were lowered (p < 0.05). These findings indicate that smoking considerably retards physiological responses to sub-maximal exercise.

Key words

Exercise - smoking - oxygen uptake kinetics - half time response - ventilation - heart rate