THE RELATIONSHIP BETWEEN THE PRESSOR RESPONSE TO INVOLUNTARY ISOMETRIC-EXERCISE AND THE CONTRACTILE PROTEIN PROFILE OF THE ACTIVE MUSCLE INMAN

The present investigation examined the relationship between the presse r response during electrically evoked isometric ankle plantar flexion and the contractile protein profile of the active muscle in seven youn g men [mean (SD) age, 26 (6) years] and five older men [70 (4) years]. Muscle biopsy samples were taken from lateral gastrocnemius (LG) and soleus (SOL) of each subject. These were analysed for isomyosin compos ition using non-denaturing pyrophosphate poly acrylamide gel electroph oresis. The degree of association was examined between the cardiovascu lar changes and the fast isomyosin content of LG and SOL individually and in combination (SOL/LG). In the total subject group there was no a ssociation between the heart rate response or the change in systolic b lood pressure (BP) and the fast isomyosin composition. However, the ch ange in diastolic BP was significantly associated with the fast isomyo sin composition of SOL/LG (Delta diastolicBP = 0.31 + 0.045% FM SOL/LG , r = 0.65, P = 0.029). These findings suggest that the magnitude of t he peripheral reflex mediated presser response to isometric exercise a nd the fast isomyosin content of the active muscle are related.