Heart rate in caged Macaca fascicularis. Effects of short-term physical exercise.

Electrocardiograms were recorded hourly for five days in 16 caged Macaca fascicularis by means of a miniaturized ECG transmitter connected to two chest leads. The lowest heart rates were 135 +/- 35 (mean +/- SD, n= 31) beats/min at 5 a.m., and the highest were 192 +/- 22 (n = 29) beats/min at 3 p.m. Sinus arrhythmia was common. Eight of the animals were trained to exercise in a specially designed enclosed treadmill; their heart rates were recorded daily during two 10-min periods of running at 3.4 km/h. Transfer of the monkeys (n k0) to the treadmill increased heart rate from 186 +/- 24 to 228 +/- 23 beats/min; exercise further increased it to 271 +/- 8 beats/min.