We examined the oxygen uptake (VO2) and carbon dioxide output (VCO2) during completion of a circuit developed for testing fire fighters and related performance time to laboratory measures of fitness. Twenty-two healthy university students (ten women) were trained in the tasks then performed the circuit as quickly as possible. Breath-by-breath gas exchange and heart rate were continuously measured with a portable system. Median circuit time was 6:13 (min:s, 25-75% = 5:46-6:42) for men and 7:25 (25-75% = 6:49-10:21) for 8 women finishers (P = 0.023), and VO2 averaged 68 and 64% VO2max for the men and women during the circuit. Both men and women had high respiratory exchange ratios (>1.0) suggesting marked anaerobic energy contribution. Physiological variables associated with circuit time were assessed by backward stepwise regression yielding a significant model that included only peak work rate during arm cranking exercise as a function of circuit completion time across men and women combined (P < 0.001). For men, but especially for women, the time required for the simulated victim drag (68.2 kg mannequin) was positively correlated with total time to complete the other circuit elements (r = 0.51, r = 0.96 respectively). The simple correlation between circuit time and VO2max (mL/kg/min) revealed poor relationships for men (r = -0.37, P > 0.05) and women (r = 0.20, P > 0.05). These data demonstrated that upper body fitness as reflected by peak work rate during arm cranking correlated with total circuit time for the men and women in our population sample.

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Measurement of the CD4 lymphocyte count is widely used as a prognostic marker and guide for the institution of antiretroviral therapy in patients infected with HIV (human immunodeficiency virus). CD4 counts are known to fluctuate with strenuous physical activity and diurnal variation but there is no information on the effects of rest or normal daily activity. We investigated the effects of rest on the absolute CD4 lymphocyte count in 20 healthy laboratory workers. Blood samples were obtained in 20 subjects upon arrival in the laboratory (CD4 0), following 30 and 60 min rest (CD4 30 and CD4 60 respectively) and 8 h into a normal working day (CD4 8). A significant decrease in the CD4 lymphocyte count was observed following 60 min rest; mean CD4 count at 0 min 1060 x 10(6)/L, mean CD4 count at 60 min 660 x 10(6)/L (P = 0.0017). These results demonstrate a significant effect of rest on CD4 lymphocyte counts in healthy volunteers. This biological variation may be important in HIV-infected patients and needs to be addressed by further studies.

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