[Hematological variations with submaximal long-term physical exercise].

The purpose of this study was to determine the effects of cold stress on routine hematologic parameters when subjects are submitted on long-lasting exercise. Eight male subjects, aged 22.7 +/- 1.3 years with a peak oxygen consumption of 54.3 +/- 5.2 mL/kg/min performed, respectively at 20 degrees C and 0 degrees C, a two-hour submaximal cyclergometry at an intensity of 40% of that performed during a previous exhaustive test. A 21-gauge catheter was inserted into an ante cubital vein for collection of the blood samples. Platelets and WBC count was significantly (p less than 0.05) increased during exercise in both 20 degrees C and 0 degrees C environmental temperatures. A slight but not statistically significant increase of RBC, Hb and Hct and a plasma concentration during cold exposure was observed. Indices are unchanged in both experiments. The findings of this study suggest that physical exercise is a major factor inducing hypervolemia and that low thermal environment does not appear to be an effective factor influencing hematologic variables during exercise.