Acute effect of cigarette smoking on physiologic response to graded exercise

To assess the acute effect of cigarette smoking on physiologic response to graded exercise, eight physical education students were tested. The protocol included running on a treadmill for 5-min periods at the speed of 6, 8, 10, and 12 km/h. Each subject performed the exercise twice 1 week apart, once after abstaining from smoking for 24 h and once immediately after smoking two cigarettes. The following measurements were performed at each work load: HR, oxygen consumption, tidal volume, breathing frequency, pulmonary ventilation, and blood lactate. Running velocity corresponding to 4 mM lactate and to 170 HR were calculated. The average HR was higher after smoking at rest and at all work loads tested (P less than 0.05). The average VO2 was lower after smoking at all work loads above 6 km/h (P less than 0.05), and VE/VO2 was significantly higher (P less than 0.001) during smoking at all work loads above 6 km/h. No changes were found in the other parameters measured. No difference was found in the calculated work load corresponding to 4 mM blood lactate or 170 HR. It is concluded that although the acute effect of smoking two cigarettes by subjects accustomed to smoking does not dramatically affect their work capacity, it does significantly change their physiologic response, manifested by a higher HR, lower VO2, and lower breathing efficiency.