To date, investigators have not examined physiological responses to prolonged upper-body exercise. Knowledge of the feasibility of performing this type of exercise and the elicited responses could have application in designing continuous training programs for upper-body muscle groups. Nine males, with a peak oxygen uptake (means +/- SD) of 49 +/- 7 for cycle (CY) and 35 +/- 6 ml X min-1 X kg-1 for arm crank (AC) exercise, completed four 60-min exercise tests. The subjects performed AC and CY exercise at the same absolute (ABS) oxygen uptake (1.6 1 X min-1) and at the same relative (REL) percent of ergometer-specific peak oxygen uptake (60%). During the ABS tests, AC exercise elicited significantly (P less than 0.05) greater heart rate (HR), ventilatory equivalent of oxygen (VE X VO2(-1), blood lactate (La), and percent decrease in plasma volume (PV) than CY exercise. During the REL tests, HR was lower and VE X VO2(-1) was higher for AC than CY exercise; there were no differences between AC and CY exercise in La or PV responses. These data demonstrate that upper-body exercise can be performed for 60 min at a relative intensity which might be sufficient to elicit a cardiovascular training effect. However, because heart rates are lower during upper-than lower-body exercise at the same relative intensity, exercise prescriptions based on heart rate alone may need to be modified for upper-body exercise.