Cardiovascular Responses to Sustained Isometric Force Production of the Finger Flexor and Knee Extensor Muscle Groups in Weight-trained and Untrained Young Men PDF Download

Author: Brain Timothy Patrick
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ISBN:
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Languages : en
Pages : 418

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Book Description
The purpose of this study was to investigate whether the cardiovascular responses to isometric force production differed significantly between weight-trained and untrained men. Thus, the cardiovascular responses to sustained isometric force production were investigated in 17 weight-trained (age = 23.5 $pm$ 2.9 yrs.) and 17 untrained (age = 25.8 $pm$ 4.1 yrs.) healthy, young men. Systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR), and stroke volume (SV) were measured, with the subject sitting, every 30 seconds during one minute of rest, during isometric force production at 40% of maximal force production by the right finger flexors (FF) and right knee extensors (KE) to muscle fatigue, and during one minute of recovery. Moreover, mean arterial blood pressure (MAP = SBP $-$ DBP/3 + DBP), cardiac output (CO = HR $times$ SV), and total peripheral resistance (TPR = MAP/CO) were derived for each recording period. Multivariate analysis of variance (MANOVA) was used to statistically analyze the significance (p $le$.05) of the mean differences between subject groups (weight-trained and untrained) and muscle groups (finger flexors and knee extensors) for the changes in the dependent variables, from rest to 30 seconds of sustained isometric force production, and from rest to fatigue. The changes in blood pressures, HR, and SV, from rest to 30 seconds of isometric force production were not significantly different between weight-trained and untrained subjects; however, changes in CO were significantly greater while changes in TPR were significantly smaller in the weight-trained compared to the untrained men. Changes from rest to fatigue in blood pressure were not significantly different between subject groups. However, the changes in CO, from rest to fatigue, were significantly larger while the changes in TPR were significantly smaller in the weight-trained compared to the untrained subjects during both finger flexion and knee extension exercises. The differences in CO and TPR responses between subject groups might indicate differences in the neural mechanisms which regulate the cardiovascular responses to sustained isometric force production. The changes in blood pressure, HR, and CO, from rest to 30 seconds of sustained isometric force production, were significantly greater during knee extension compared to finger flexion; however, at fatigue, only the changes in HR and CO were significantly different (KE $>$ FF) between tasks. The differences between tasks in the HR and CO responses to sustained isometric force production might be due to differences in the amount of active muscle mass, and thus, differences in the blood flow requirements.