We studied the effects of two different light conditions on handgrip exercise in a climatic chamber (26°C, 60% RH) with 8 female subjects, aged 20-24 years. The subjects were either in the dim light condition of 50 Lux ("Dim") or in the bright conditions of 5,000 Lux ("Bright") from 10 : 00 h to 18 : 00 h, in 50 Lux from 18 : 00 h to 22 : 00 h, in complete darkness from 22 : 00 h to 6 : 00 h (Sleep) and again in 50 Lux from 6 : 00 h to 6 : 30 h, they were instructed to perform handgrip exercise with a handergometer until the occurrence of exhaustion. The probable influences of "Dim" and "Bright" light conditions during the previous daytime from 10 : 00 h to 18 : 00 h on the number of contractions with the usage of a handergometer were compared.
　The main findings were summarized as follows ; 1) The number of contractions was 767±43 (mean±SEM) in "Dim" and 865±55 in "Bright", which was significantly different (P<0.01) 2) Rectal temperatures were significantly lower mostly in "Bright" than in "Dim" 3) Salivary lactic acid concentration examined immediately after having got up at 6 : 00 h was 5.0±0.95 mg/dl in "Dim" and 4.03±0.79 mg/dl in "Bright", which was significantly different (P<0.05). These findings were discussed in terms of circadian and thermal physiology.

DESCENTE SPORTS SCIENCE Vol.17/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE