Chronobiological case study on cardiac responses during aerobic exercise

Abstract

50% HR reserve aerobic exercise on a bicycle ergometer was carried out for 20 min each time by a slightly obese male aged 70 years old from October, 1998 to August, 2000 at 8:00 AM (Mor. Ex.) or 17:00 PM (Even. Ex.). The same exercise was carried out at random times during the day from January to March, 2000. The following five indicators were measured: the heart rate in the first minute of exercise, the time until the attainment of the target heart rate, the loaded power at the time of attaining the target heart rate, the energy consumption during exercise, and RPE on the Borg Scale. The effects of Jet lag were also observed three times during that period. The following results were obtained. I. The changes in indicators with the progress of exercise; 1. The heart rate after the first minute of exercise was increased in the Mor. Ex. 2. The time until attainment of the target heart rate was shortened in the Mor. Ex., but it was unchanged in the Even. Ex. 3. The loaded power at the time when the target heart rate was attained decreased in the Mor. Ex., but it was unchanged in the Even. Ex. 4. Energy consumption decreased in the Mor. Ex., and increased in the Even. Ex. 5. The RPE decreased in the Mor. Ex., but increased in the Even. Ex. The abovementioned changes were not due to seasonal variations. II. The effects of exercise became stable at and after six months in the Mor. Ex., and nine months in the Even. Ex. III. The differences between Mor. Ex., and Even. Ex. in all the indicators were significant. IV. The coefficient of correlation between the energy consumption and heart rate at the end of the first minute of exercise was significantly inverse. V. Energy consumption during exercise increased from 8:00 AM and left the range of morning response at 9:30 AM and entered the range of evening response on and after 11:00 AM. It decreased for a short time after lunch. VI. The effect of Jet lag was observed as a lowering of energy consumption during exercise in the Even. Ex., and two or four days were required for recovery.