Influence of instruction on evaluation of repeated muscular endurance

This study was done to examine the influence of instructions on the evaluation of rhythmic repeated muscular endurance, that is, the ability to continue muscle-power exertion at a regular interval. 15 healthy young male adults performed maximal repeated rhythmic grips for 6 min. under the following three instruction conditions: (1) "Squeeze freely during the 2-sec. interval," (2) "Squeeze quickly and then relax," and (3) "Squeeze quickly and then hold the exertion for 1 sec." Time to peak force was slower in Condition 1 than in Condition 2. A decline in exertion of force was found for all conditions after 1 min. The decline in rate of the peak values in Conditions 1 and 3 was about 10 to 15% larger than that of Condition 2. In conclusion, proper instructions are necessary, even for a short 2-sec. interval, when evaluating muscular endurance with repeated rhythmic grips. Condition 2 instruction may be most effective.