Strength training for 1h in humans : effect on the motor performance of normal upper extremities

It has been found that one session of intense muscle strength training decreases muscle strength temporarily and causes neuromuscular fatigue in the trained muscles, but little attention has been given to the effects of neuromuscular fatigue on the other components of motor performance. The purpose of this study was to examine in normal healthy volunteers the effects of a 1-h strength training session on the motor performance of the upper extremity, including reaction time, speed of movement, tapping speed and coordination. Group of 30 healthy female volunteers, aged 29-47 years, were randomly divided into sub-groups, (A and B, n = 15 per group). Both groups first completed a set of motor performance tests on 3 consecutive days. On the 4th day, group A carried out a 1-h muscle strength training session of the upper extremities. Isometric muscle strengths and electromyogram (EMG) data were recorded before the training session. Immediately after the training session the same recordings were repeated, and additional motor performance tests were also performed. Group B carried out only the motor performance tests. The groups exchanged programmes the following week. The 1-h strength training session decreased the isometric muscle strength of wrist flexion by 18% (P < 0.001) and extension by 18% (P < 0.001) in group A, while in group B flexion strength decreased by 19% (P < 0.001) and extension strength by 17% (P < 0.001). All the measured EMG activations also decreased in both groups. There were no statistically significant differences in the results of the motor performance tests between the mean values of the three baseline measurements and the values recorded after the training session. The result was surprising, but straightforward; neuromuscular fatigue induced by a 1-h strength training session of the upper extremities had no effect on the motor performance functions of the hand, as indicated by reaction times, speed of movement, tapping speed and coordination, in these normal healthy female volunteers.