Effects of Different Light Source Color Temperatures during Physical Exercise on Human EEG and Subjective Evaluation

Abstract

This study examined the effects of the color temperature of lighting on spontaneous electroencephalographic (EEG) activity and subjective evaluation under physical exercise. Participants (n=10) were asked to (a) sit quietly for 45-min rest, (b) carry out successive exercise bouts of 50 W and 100 W on a cycle ergometer for 14 mins, and (c) sit quietly for a 21-min recovery period. EEGs and subjective evaluation were carried out during the last 6 min of the adaptation period, immediately after exercise, and at the 7.5-min and 15-min stages of the recovery period after exercise. The experiments were conducted in a lighting laboratory controlled at a temperature of 25°C and a relative humidity of 50–60%. The illuminance condition was maintained at 1000 lx and combined with three different color temperature conditions (3000 K, 5000 K and 7000 K) for a total of three lighting environments. The results of the EEG recording at Pz showed that the Alpha Attenuation Coefficient (AAC) was more increased at higher color temperatures after exercise than at lower temperatures, and the speeds of recovery at Fz, Cz, and Pz were slower during the 7000 K condition. The changes in AAC were most remarkable at Pz. After exercise, the level of “sleepiness” at the lower color temperature (3000 K) was significantly higher than those at the higher color temperatures (5000 K and 7000 K) (P<0.05), and the level of “relaxation” at the higher color temperature (7000 K) was significantly lower than those at the lower color temperatures (3000 K and 5000 K) (P<0.01). In contrast, the level of “concentration” at the lower color temperature (3000 K) was significantly lower than those at the higher color temperature (5000 K and 7000 K) (P<0.01). The level of “fatigue” was the highest at 7000 K compared with those at 5000 K and 3000 K (P<0.05). The highest level of “motivation” was found at 5000 K. Both “fatigue” and “motivation” showed a significant interaction between color temperature and exercise. These results suggest that the color temperature of 5000 K is more comfortable and advantageous for physical exercise and that the lower color temperature of 3000 K is beneficial for rest and fatigue recovery after exercise.The above results indicate that muscle activity under photic stimulation has effects on AAC and subjective evaluation; that is, the color temperature of fluorescent lamps and the exercise have an obvious effect on AAC and subjective evaluation, as predicted based on the increase of cortical arousal level.