Impact of habitual cocaine smoking on the physiologic response to maximum exercise.
BACKGROUND
Habitual smoking of alkaloidal cocaine (crack) has been reported to be associated with a number of cardiopulmonary complications that may not be clinically obvious but could potentially interfere with normal physiologic responses to exercise and thus impair maximum exercise performance.


OBJECTIVE
To evaluate the impact of regular use of cocaine on maximum exercise.


METHODS
Observational study in crack users and age- and gender-matched control subjects.


METHODS
Thirty-five habitual cocaine smokers (21 male and 14 female) and 29 age-matched 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 maximal exercise performed on a cycle ergometer using a ramp protocol. Comparisons 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 not show evidence of ventilatory limitation, reduced gas exchange threshold, 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 uptake 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 possibility of perceptual dysfunction for effort. Differences in aerobic capacity between the crack users and nonusers could not be explained by differences in physical fitness or altered perception of dyspnea.


CONCLUSIONS
In the subjects we studied, long-term cocaine smoking was associated with reduced maximum exercise performance, probably due to poor motivation or altered effort perception. No other identifiable physiologic abnormality appeared to limit exercise in the habitual crack users.
Marques-Magallanes
J A
JA
Department of Medicine, UCLA School of Medicine, Los Angeles, CA 90095-1690, USA.
Koyal
S N
SN
Cooper
C B
CB
Kleerup
E C
EC
Tashkin
D P
DP
D000328:Adult; D015308:Anaerobic Threshold / Q000502:physiology; D002245:Carbon Dioxide / Q000097:blood; D016022:Case-Control Studies; D016578:Crack Cocaine; D004417:Dyspnea / Q000503:physiopathology; D005080:Exercise Test; D005260:Female; D006321:Heart / Q000503:physiopathology; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008168:Lung / Q000503:physiopathology; D008297:Male; D008451:Maximal Voluntary Ventilation / Q000502:physiology; D008875:Middle Aged; D009042:Motivation; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption / Q000502:physiology; D010465:Perception; D005082:Physical Exertion / Q000502:physiology*; D010809:Physical Fitness; D011659:Pulmonary Gas Exchange / Q000502:physiology; D012119:Respiration / Q000502:physiology; D012126:Respiratory Dead Space / Q000502:physiology; D012737:Sex Factors; D019966:Substance-Related Disorders / Q000503:physiopathology*
D016578:Crack Cocaine; D002245:Carbon Dioxide; D010100:Oxygen