IMPACT OF HABITUAL COCAINE SMOKING ON THE PHYSIOLOGICAL-RESPONSE TO MAXIMUM EXERCISE

Background: Habitual smoking of alkaloidal cocaine (crack) has been re ported to be associated with a number of cardiopulmonary complications that may not be clinically obvious but could potentially interfere wi th normal physiologic responses to exercise and thus impair maximum ex ercise performance. Study objective: To evaluate the impact of regular use of cocaine on maximum exercise. Design: Observational study in cr ack users and age- and gender-matched control subjects. Subjects: Thir ty-five habitual cocaine smokers (21 male and 14 female) and 29 age-ma tched sedentary control nonsmokers of cocaine (15 male and 14 female), all of whom were in good general health. Methods: In these subjects, we compared physiologic responses to symptom-limited, incremental maxi mal exercise performed on a cycle ergometer using a ramp protocol. Com parisons were made for men and women separately. Results: For both men and women, long-term cocaine smokers had a reduced aerobic capacity ( maximum oxygen consumption) compared with control nonsmokers but did n ot show evidence of ventilatory limitation, reduced gas exchange thres hold, increased physiologic dead space, or gas exchange abnormality at maximum exercise compared with the healthy control subjects. Although cocaine smokers had reduced maximum heart rates compared with control subjects, the relationship between submaximal heart rate and oxygen u ptake was normal, indicating a normal cardiovascular response pattern. However, effort perception was similar between the two groups despite the difference in heart rate at maximum exercise, suggesting the poss ibility of perceptual dysfunction for effort. Differences in aerobic c apacity between the crack users and nonusers could not be explained by differences in physical fitness or altered perception of dyspnea. Con clusion: In the subjects we studied, long-term cocaine smoking was ass ociated with reduced maximum exercise performance, probably due to poo r motivation or altered effort perception. No other identifiable physi ologic abnormality appeared to limit exercise in the habitual crack us ers.