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Summary: The purpose of this investigation was to evaluate the effect of passive smoke inhalation on submaximal and maximal exercise performance. Eight female subjects ran on a motor driven treadmill for 20 min at 70% $$V_{O_{2\max } } $$ followed by an incremental change in grade until maximal work capacity was obtained. Each subject completed the exercise trial with and without the presence of residual cigarette smoke. Compared to the smokeless trials, the passive inhalation of smoke significantly reduced maximal oxygen uptake by 0.25 1min−1 and time to exhaustion by 2.1 min. The presence of sidestream smoke also elevated maximal R value (1.01 vs 0.93), maximal blood lactate (6.8 vs 5.5 mM), and ratings of perceived exertion (17.4 vs 16.5 units). Passive inhalation of smoke during submaximal exercise significantly elevated the CO2 output (1.68 vs 1.58 lmin−1),R values (0.91 vs 0.86), heart rate (178 vs 172 btsmin−1) and rating of perceived exertion (13.8 vs 11.8 units). These findings suggest that passive inhalation of sidestream smoke adversely affects exercise performance.

Prolactin is an important hormone during pregnancy, affecting mother, fetus, and amniotic fluid volume. Immersion is known to affect prolactin levels significantly. To determine the effect of immersion and exercise on the prolactin response during pregnancy, we examined serum prolactin levels at 15, 25, and 35 weeks' gestation and 10 weeks post partum. Twelve women completed 20 min land rest, 20 min immersion in 30° C water to the xiphoid, and 20 min exercise in the water at 60% $$\dot V_{O_2 \max } $$ Resting prolactin levels were 1.91±0.32, 4.55±0.5, and 5.85±0.27 nmol·l-1 ±standard error of the mean at 15, 25, and 35 weeks' gestation, respectively. Postpartum lactating women had a resting mean prolactin level of 3.95±1.6 versus 0.22±0.4 nmol· l-1 in non-lacting women. Prolactin levels declined significantly during immersion even after correction for dilution by plasma volume shifts. The immersion response was inversely related to the duration of pregnancy with 29%, 22%, and 12% drops during 15-, 25- and 35-week trials, respectively. Compared to rest, exercise prolactin levels remained depressed during the 15th and 25th week trials. We hypothesize that immersion in water caused prolactin levels to decline.