INFLUENCE OF 2 DIFFERENT LIGHT INTENSITIES DURING DAYTIME ON ENDURANCE PERFORMANCE OF HANDGRIP EXERCISE

The effect of two different light intensities (dim, 50 lux and bright, 5,000 lux) on handgrip exercise in a climatic chamber (26 degrees C, 60% relative humidity) were studied in eight female subjects, aged 20- 24 years. The subjects were in either the dim or bright light from 100 0 hours to 1800 hours. They were then in 50 lux from 1800 hours to 220 0 hours in complete darkness from 2200 hours to 0600 hours (sleep), an d again in 50 lux from 0600 hours to 0800 hours. They were instructed to perform handgrip exercise with a hand ergometer until the occurrenc e of exhaustion from 0600 hours. The influence of dim and bright inten sities during the previous daytime on the number of contractions was c ompared. The main findings were firstly that the mean number of contra ctions was 766.63 SEM 43.28 in nim and 864.5 SEM 54.76 in bright inten sities (P < 0.01), and secondly that rectal temperatures were slightly but significantly lower in the bright than in the dim intensities. Th e reason for the reduced number of contractions in dim was discussed i n terms of the establishment of a higher set-point in the core tempera ture in dim.