The effects of strength training on arterial structure and function in middle-aged and older adults
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The effects of strength training on arterial stiffness in middle-aged and older adults were comprehensively assessed in central and peripheral arteries using the ultrasound derived method, pulse wave velocity (PWV) and wave reflection techniques. The latter two methods, which have the most clinical utility, were quantified with an automatic medical device designed to reduce the subject testing time and investigator measurement variability. Validation of the automatic medical device with respect to criterion methods, its test-retest reliability and sensitivity to detect change following strength training were confirmed. After a 13 week, whole body strength training program performed three times per week, central arterial stiffness, as measured by the ultrasound derived method at the carotid artery, increased 17% (P<0.05) and was associated with a significant increase in relative wall thickness. Wave reflection, as measured by carotid vii augmentation index, and carotid-femoral PWV was not increased. These data suggest that in older adults, strength training may increase age-related central arterial stiffness, but that the stiffening of the elastic arteries may be localized to the most proximal portions where buffering of cardiac pulsations is highest. Unlike the carotid artery, the femoral artery adapted to the strength training stimuli with a 15% decrease (P=0.10) in stiffness and significant decrease in relative wall thickness. There was a trend for femoral-ankle PWV to decrease as well. This suggests that the muscular peripheral arteries may not be subjected to the same mechanical and/or physiological stimuli resulting from strength training as the carotid artery. Despite the increase in central arterial stiffness with strength training, there was no increase in left ventricular hypertrophy, loss of left ventricular diastolic function or decrease in cardiovagal baroreflex sensitivity, all of which are associated with arterial stiffness. Although the increase in central arterial stiffness with strength training did not affect these clinically relevant outcomes, it may be that a longer intervention period is needed for these changes to occur.