Cardiovascular, respiratory, and metabolic responses to upper body exercise.

Many studies have suggested that arm exercise, particularly in the supine position or with arms elevated, is more stressful than leg exercise. Arm exercise at a given workload is typified by cardiac output and oxygen consumption values slightly higher and heart rate, blood pressure, ventilatory and blood lactic acid responses that are significantly higher than those observed during leg exercise. Part of the increased physiological stress during arm exercise may be due to sluggish kinetics of oxidative metabolism and increased glycolysis leading to lactic acid production and accumulation in blood. This physiological state would lead to a cardiovascular and respiratory pressor effect. The limitations of VO2 adjustment in the arms are not due to cardiac or muscle blood flow limitations as these are quick to adjust and reach higher absolute levels than during leg exercise. Specific arm training increases the VO2 adjustment, and the physiological values in these subjects during arm exercise are similar to those observed during leg exercise.