This study was investigated the effects on functional recovery of eccentric exercise-induced muscle damage by phonophoresis transdermal permeation of piroxicam gel and observed the change of amplitude at muscle action potential. Through eccentric exercise-induced muscle damage, performed healthy men and women take eccentric resistance exercise and measured action, potentials. The subjects were divided into three groups of four men each 24 hour, 48 hour, 72 hour. The results of this were as follows: 1. Change of maximal action potential at maximal voluntary contraction : The phonophoresis group was increase more than control group and gel group. 2. Change of average action potential at maximal voluntary contraction : The gel group was increase more than control group and phonophoresis group. 3. Change of maximal action potential at pain subthreshold voluntary contraction : The phonophoresis group was increase more significantly than control group and gel group. 4. Change of average action potential at pain subthreshold voluntary contraction : The phonophoresis group was increase more significantly than control group and gel group. In conclusion, the change of muscle action potential amplitude by eccentric exercise-induced muscle damage showed that the phonophoresis by pulsed ultrasound of piroxicam gel was improved the recovery of muscle function.