Effects of isometric exercise versus electrical muscle stimulation on serum enzymes, plasma lactate and peak torque levels in males
Hodgkinson, J. Ross
Master of Science
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The purpose of the study was to examine the effects of electrical muscle stimulation (EMS) and isometric exercise (IE) on peak torque, plasma lactate and serum enzymes. The subjects were 14 male volunteers aged 22-41. The subjects were randomly assigned to either the EMS group (Stayodyn EMS/plus stimulator; bipolar technique of the quadriceps; 50 pulse/sec; pulse width of 200 /isec; 2 sec ramp and 8 sec maximum /lO sec rest for 45 trials) and the IE group (Kin-Com); 10 sec maximal voluntary contraction /lO sec rest for 45 trials). The subjects performed both tests on two alternate weekends. The peak torque value was measured for each contraction for both tests. Blood samples were taken from the antecubital vein prior to testing and at 5 minute, 1 hour and 24 hours post exercise to determine plasma lactate concentrations (HLA), serum creatine kinase (CPK), serum aspartate aminotransferase (AST), and serum lactate dehydrogenase (LDH) activities. The enzymes and HLA were analyzed using an Abbott VP Bichromatic Analyzer. The results indicated that: (a) peak torque produced by IE was significantly greater (P<0.05) than that produced by the EMS/plus stimulator; (b) both exercise modes produced significant increases (P<0.05) in HLA concentrations 5 minutes post exercise, with the increase in HLA concentration of the IE group being significantly greater (P<0.05) than that of the EMS group; (c) both exercise modes resulted in significant increases (P<0.05) in serum CPK activity 24 hours post exercise, with the increase in serum CPK activity of the IE group being significantly greater (P^O.05) than that of the EMS group; (d) both exercise modes resulted in significant increases (P<0.05)in serum AST activity 24 hours post exercise, with the increase in serum AST activity of the IE group being significantly greater (P<0.05) than that of the EMS group; (e) neither IE nor EMS resulted in a significant increase (P>0.05) in serum LDH activity. It was concluded that both IE and EMS can produce an acute exercise response. The significant difference (P<0.05) in peak torque, HLA, serum CPK and AST between the two groups would suggest that the exercise stress of the IE group was greater and therefore, the intensity of the exercise was greater than that of the EMS. The significantly lower (P<0.05) torque values in the EMS group may have been due to: (a) "failed force outputs", due to the inability to activate all of the motor axons of a large muscle group; (b) "accommodation" to the electrical stimulator output; (c) motivational factors, which may include the inability to tolerate the electrical current, by some subjects. Whether the increased acute exercise response demonstrated by the IE group would result in significant improvements in strength or endurance over the EMS group, would require a comparison over an extended training program.