Continuous intramuscular pH measurement during the recovery from brief, maximal exercise in man

Muscle pH and temperature were measured before, and continuously for 30 min after, a 30-s maximal sprint exercise in ten subjects. These measurements were made with a needle-tipped pH electrode and a thermocouple placed in vastus lateralis. Venous blood samples were collected for pH, lactate and catecholamine estimations and measurements were also made of the arterial blood pressure and heart rate. The muscle and venous pH decreased from 7.17 +/- 0.01 (mean +/- SEM) and 7.39 +/- 0.01 to 6.57 +/- 0.04 and 7.04 +/- 0.03, respectively, in response to the exercise. No significant recovery occurred in either pH measurement for 10 min, after which muscle pH increased to 7.03 +/- 0.03 and venous pH to 7.29 +/- 0.01 by 30 min. Muscle temperature increased by 2.1 degrees C with exercise and also failed to return to pre-exercise values by 30 min. Blood lactate concentration increased from 0.75 +/- 0.04 mmol l-1 before exercise to a peak value of 15.76 +/- 0.35 mmol l-1 5 min after completion of the exercise, and then declined slowly to 10.30 +/- 0.61 mmol l-1 by 30 min. Arterial blood pressure increased transiently with exercise but recovered rapidly, whereas the exercise-induced tachycardia was sustained throughout the recovery period. The recovery from the metabolic and cardiovascular responses to maximal sprint exercise in man is incomplete 30 min after cessation of the exercise.