Haemodynamic and metabolic responses of laboratory XXXX to near-maximal treadmill exercise.

@entity26 @entity95 @entity880
1. The haemodynamic and metabolic responses of four laboratory @entity95 to horizontal treadmill exercise at 8, 12, 16 and 20 m/min were studied. The primary haemodynamic variables measured were heart rate, cardiac output and arterial pressure. The metabolic variables measured were arteriovenous @entity26 difference, whole-body @entity26 consumption and central venous plasma @entity880 concentration. 2. Only at 8 m/min did the haemodynamic and metabolic variables reach an approximate steady state. This was the greatest speed at which aerobic exercise could be sustained for 4 min in all @entity95 . 3. As the speed of the treadmill was increased the @entity95 showed signs of exhaustion after progressively shorter periods of exercise. Exhaustion was associated with steep rises in central venous plasma @entity880 concentration. Exhaustion was also usually associated with secondary rises in systemic vascular resistance and arterial pressure, especially at 20 m/min. 4. The asymptotic (maximal) values for heart rate, cardiac index and O2 consumption were 386 beats/min, 263 ml/kg per min and 21.7 ml/kg per min, respectively. heart do not permit it to run continuously at other than a slow rate. Exhaustion is associated with increasing @entity26 debt and, especially at near-maximal rates of exercise, with intense vasoconstriction in as yet unidentified vascular beds.
