Electromyogram median power frequency in dynamic exercise at medium exercise intensities.
The electromyogram (EMG) median power frequency of the calf muscles was investigated during an exhausting treadmill exercise and a 20-min recovery 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. In contrast, EMG median power frequency in isometric contractions of the same muscles decreased by 7% for the soleus muscle and 16 to 18% for gastrocnemius muscles immediately after the exercise. During the recovery period the isometric median power frequency 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 investigation at a steeper gradient gave evidence that two types of exhaustion can be distinguished during dynamic exercise; exhaustion at lower exercise intensities without a decrease in frequency during exercise and exhaustion at high intensities accompanied by a decline of frequency. The reason for this difference remains unclear.
Ament
W
W
Centre for Biomedical Technology, Faculty of Medicine, University of Groningen, The Netherlands.
Bonga
G J
GJ
Hof
A L
AL
Verkerke
G J
GJ
D000328:Adult; D004562:Electrocardiography; D004576:Electromyography / Q000592:standards*; D015444:Exercise / Q000502:physiology*; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology; D012420:Running