The lack of influence of reactive hyperemia on exhausting rhythmic or static exercise.

Muller (1958) and Nukada (1955) claimed that the performance of exhausting exercise can be greatly prolonged if the exercise is begun at the start of reactive hyperemia. They reported that arrest of the circulation for 10 min immediately before beginning rhythmic exercise had increased the endurance time nearly 7-fold. We have repeated Muller's and Nukada's experiments. In one series we used rhythmic exercises on a bicycle ergometer, and in another sustained contractions on a hand-grip dynamometer. Our results failed to support those of the above authors. The endurance times for rhythmic and static exercise were unaltered by previous arrest of the circulation.

Experiments on the liberation of phosphate from the muscles of the human forearm during vigorous exercise and on the action of sodium phosphate on forearm muscle blood vessels.

1. During vigorous sustained or rhythmic exercise of the forearm muscles, plasma phosphate in the venous effluent from the active muscles increased by about 20%.2. The forearm muscles liberate phosphate during vigorous activity. This confirms observations made by Hilton & Vrbová (1970) on fast muscles in the cat.3. Infusions of sodium phosphate into the brachial artery which raised plasma phosphate in the venous effluent from the resting muscles by 400% had no effect upon the rate of the forearm blood flow.4. These results do not suggest that the liberation of phosphate plays any significant part in mediating the vasodilatation accompanying vigorous exercise of the muscles in the forearm.

The effect of tiring the forearm muscles in different ways on venous blood pH, pco2 and standard bicarbonate.

1. The changes in venous blood pH, p(CO2) and standard bicarbonate caused by tiring the forearm by (a) rhythmic work with free circulation, (b) rhythmic work with ischaemic circulation, were determined using the Astrup apparatus.2. For rhythmic work, opening and shutting the hand as quickly as possible for 2 min, the averaged results on six subjects were: pH fell 0.19 units; p(CO2) (after full oxygenation of venous blood) rose 52 mm Hg; standard bicarbonate fell 2.9 m-equiv/l.3. For rhythmic work during ischaemia and accompanied by pain, the averaged results on six subjects were: pH fell 0.19 units; p(CO2) (after full oxygenation of venous blood) rose 26 mm Hg; standard bicarbonate fell 6.3 m-equiv/l.4. These results are compared with those obtained in an earlier investigation on the effect of strong hand grips for 1 min.