Background: Neuromuscular electrical stimulation (NMES) has been noted as an effective pre-conditioning intervention for an increase of the rate of development (RFD). However, it is unknown whether NMES increases muscle flexibility. Therefore, the purpose of this study was to investigate whether neuromuscular electrical stimulation (NMES) at 20% of maximal voluntary isometric contraction (MVIC) torque level for 5 seconds used as a warm-up is effective for improving the range of motion (ROM) following increased tolerance for muscle extensibility with/without alteration of the MTU stiffness.   Methods and Results: Maximum ROM and ROM with standardized torque (30N) were measured in both legs in thirteen healthy males before and after NMES intervention at a 20% MVIC level for 5 seconds. The maximum ROM increased after intervention compared with before intervention on the NMES side, while it was not changed on the non-NMES side. In addition, there were no significant differences in the ROM with standardized torque in any measurements.  Conclusion: It is concluded that NMES at 20% MVIC for 5 seconds could be effective for improving ROM following an increased tolerance for muscle extensibility without alteration of the MTU stiffness.