title: Acute effects of marihuana smoking on maximal exercise performance.
abstract: To evaluate the effects of marihuana smoking on exercise performance, 12 healthy young subjects did progressive exercise testing on an ergocycle to exhaustion under two conditions: non-smoking (control) and 10 min after smoking a marihuana cigarette (containing 1.7% of delta-9-tetra-hydro-cannabinol) of 7 mg X kg-1 body weight. Heart rate, arterial blood pressure, minute ventilation (VE), breathing rate (fb), oxygen uptake (VO2), and carbon dioxide output (VCO2) were measured before, during, and for 4 min after the exercise. Tidal volume was calculated from VE X fb-1. The exercise duration was also measured. Forced expiratory volume (FEV1) was measured: before smoking (rest); before exercise (10 min after smoking); and after exercise. Carboxyhemoglobin levels were measured before and 10 min after smoking in four subjects. Marihuana smoking reduced exercise duration (16.1 +/- 4.0 to 15.1 +/- 3.3 min, P less than 0.05). At peak exercise performance, there were no differences in VO2, VCO2, heart rate, and VE between the two experimental conditions. Marihuana induced tachycardia at preexercise (94.3 +/- 13.3 beats X min-1 to 119.0 +/- 18.0, P less than 0.01) that was sustained up to 80% of maximum effort and during the recovery period. After marihuana, VE, VO2 and VCO2 were increased above control from 50% of maximum effort to the end of the test. Marihuana induced a bronchodilation (FEV1 from 4.28 +/- 1.00 to 4.43 +/- 1.031, P less than 0.0) that was still present after exercise. Exercise induced a bronchodilation in the control condition but not in the marihuana smoking condition.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000328:Adult; D001794:Blood Pressure; D001980:Bronchi / Q000503:physiopathology; D002245:Carbon Dioxide / Q000378:metabolism; D004108:Dilatation, Pathologic / Q000209:etiology; D004734:Energy Metabolism; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D002189:Marijuana Abuse / Q000150:complications / Q000503:physiopathology*; D010101:Oxygen Consumption; D005082:Physical Exertion; D012129:Respiratory Function Tests; D013610:Tachycardia / Q000209:etiology; D014938:Work Capacity Evaluation
chemical_list: D002245:Carbon Dioxide