The purpose of this study was to examine the individual differences in relative grip-strengthendurance (RGE) variables and relations between force, endurance time and level of subjective musclefatigue sensation (SMS) of RGE. Endurance time and SMS during grip-strength exertion using various relative demand values to the maximal grip-strength-value (MAX) were analyzed. Subjects were 23 healthy adults (male 10 and female 13) . Four demand values of 25, 35, 50 and 75% were selected as relative demand values to MAX. The grip-strength-exertion value was input into a personal computer using the system of grip-strength with a strain-gauge (Yagami : ED-D 100 R) . The results are summarized as follows:
1) Muscle group related to grip-strength exertion recovered up to about 60% of initial within 10-15 sec after grip-strength exertion stopped regardless of the degree of relative demand values.
2) The SMS in any relative demand values reached a peak after continuing relative demand values became impossible, and the tendency is stronger with a higher demand value.
3) With about 25% relative demand values, physiological muscle fatigue and SMS advanced at almost the same time, and the grip-strength exertion was possible for a little while after the SMS reached a peak.
4) With the lower relative demand values under 50%, the influence of SMS appeared stronger by extending the endurance time and the decline-delay of grip-strength-exertion.
5) With relative demand values over 50%, continuing relative demand values became impossible within a short time, and the peak SMS appeared earlier than that of relative demand values. On the other hand, the continuing the lower relative demand values was possible to some extent, and individual differences in the continuance and peak arrival-times of SMS were large.