Force, endurance time, and cardiovascular responses in voluntary isometric contractions of different muscle groups.
A study was made to reinvestigate the general validity of the force/endurance relation of isometric contractions. Relative force development, mean bioelectrical muscle activity and circulatory responses (blood pressure, interbeat interval) during isometric contractions of different muscle groups were compared. 6 men performed maximum isometric contractions of foot plantar- and dorsalflexors and hand flexors lasting 10 minutes. The hydrostatic blood pressure was varied by placing subject's arms and legs in two different positions, high and low. 9 Women performed plantarflexion and dorsalflexion with maximum strength and at constant load of 60% MVC to exhaustion. The results confirm that the force/endurance relationship during isometric exercise is not a biological constant, applicable for all muscles. The fibre composition of the muscle and the blood pressure varied by different hydrostatic components are discussed as factors causing differences in force/endurance relationship.
Central Institute of Occupational Medicine of the GDR Berlin.
H
H
Rehfeldt
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G
Caffier
H
H
Kramer
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G
Küchler
D000328:Adult; D001132:Arm / Q000502:physiology; D001794:Blood Pressure; D004562:Electrocardiography; D004576:Electromyography; D005260:Female; D005528:Foot / Q000502:physiology; D006439:Hemodynamics; D006801:Humans; D007537:Isometric Contraction; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction; D009132:Muscles / Q000502:physiology*; D010807:Physical Endurance