1. The response of plasma noradrenaline, arterial blood pressure and heart rate to sustained handgrip at 30% of maximal voluntary contraction was studied in patients with long-term juvenile-onset-type diabetes mellitus and healthy subjects of comparable age. 2. There was no significant difference between the intensity and duration of handgrip in diabetic patients and healthy subjects. 3. Sustained handgrip produced an increase in plasma concentration of noradrenaline both in diabetic and healthy subjects but the response in the diabetic subjects was significantly less. 4. The increase in systolic blood pressure during handgrip was significantly greater in diabetic subjects than in normal subjects. The increases in diastolic and mean blood pressure did not differ significantly. 5. The increase in heart rate during handgrip was greater in healthy subjects than in diabetic subjects. The response was smaller in diabetic patients with retinopathy than in the patients without retinopathy. 6. The sustained handgrip test may be useful for the diagnosis of abnormal sympathetic nervous system and haemodynamic responsiveness in diabetic patients.
1. Plasma catecholamine, haemodynamic and metabolic responses to sustained isometric exercise were studied in eight healthy subjects, who maintained handgrip at the 30% level of maximal voluntary contraction (MVC) for as long as possible. 2. The sustained handgrip was accompanied by a significant increase in plasma noradrenaline (NA) and adrenaline (A) concentrations. 3. The increase in plasma NA during handgrip was greater than that associated with heavy dynamic work involving large muscle groups. 4. The results suggest that the known haemodynamic responses to static effort are related to a powerful activation of the adrenergic system, which may result from a reflex mechanism initiated in the exercising muscles.