ELECTROMYOGRAM MEDIAN POWER FREQUENCY IN DYNAMIC EXERCISE AT MEDIUM EXERCISE INTENSITIES

The electromyogram (EMG) median power Frequency of the calf muscles wa s investigated during an exhausting treadmill exercise and a 20-min re covery period. The exercise was an uphill run at a speed of 5 km . h(- 1) and a gradient of 20%. During exercise there was no decrease of EMG median power frequency. Tn contrast, EMG median power frequency in is ometric contractions of the same muscles decreased by 7% for the soleu s muscle and 16 to 18% for gastrocnemius muscles immediately after the exercise, During the recovery period the isometric median power Frequ ency of the gastrocnemius muscles increased to pre-exercise levels in about 5 min. The isometric median power frequency of the soleus muscle also increased but had not reached pre-exercise values by 20 min. The observations from this study and from a previous uphill treadmill inv estigation at a steeper gradient ga-cre evidence that two types of exh austion can be distinguished during dynamic exercise; exhaustion at lo wer exercise intensities without a decrease in frequency during exerci se and exhaustion at high intensities accompanied by a decline of freq uency. The reason for this difference remains unclear.