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 (t1/2) was calculated for V̇O2, V̇CO2, Ve and HR. Smoking abstinence was associated with t1/2 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
