Duration Of Aerobic Exercise Research Articles

Increase of LDL susceptibility to oxidation occurring after intense, long duration aerobic exercise

The effect of heavy, long duration aerobic exercise on low density lipoprotein (LDL) susceptibility to oxidation and on distribution of LDL subfractions was studied. Six well-trained runners, previously fasted, ran continuously for 4 h. Controlled intake of liquid and food was permitted during exercise. Total plasma and LDL triglyceride increased significantly. LDL susceptibility to oxidation, measured as conjugated dienes formation, was modified significantly ( P < 0.05) after running (14% reduction in lag phase time, and 8% increase in maximal curve slope). The percentage of electronegative LDL form (named LDLB) also increased significantly ( P < 0.05) after exercise both basally (from 7.3% to 11%) and after 2h of induced oxidation (from 40.6% to 52.3%). Neither LDL susceptibility to oxidation nor increase of LDLB was statistically associated with food consumed during the race or modifications of triglycerides suggesting that this effect was due to exercise rather than food-related. The pattern of LDL subfractions was type A in all athletes before and after running. The oxidative LDL changes, seen in exercise conditions similar to those of hard training or competition, demonstrated an unfavourable effect of very intense exercise on lipoprotein metabolism.

Postexertional hypotension: A brief review

A statistically and clinically significant reduction in arterial pressure occurs following a single bout of low intensity, short duration aerobic exercise in individuals with hypertension. The reduction in arterial pressure is most often associated with a decrease in total peripheral resistance, peripheral sympathetic nerve activity, and plasma norepinephrine concentration; however, cardiac output is often elevated without a change in heart rate. The purpose of this article is to review the literature and propose a model that analyzes the components contributing to the postexercise reduction in arterial pressure. The model implicates an attenuated vascular response to catecholamine stimulation and an enhanced inhibitory cardiopulmonary reflex response. Recent evidence has shown that a single bout of dynamic exercise significantly attenuated the vasoconstrictor response to phenylephrine in an isolated aortic ring preparation and in the intact conscious rabbit and rat. This suggests that the ability of the ...

Effects of acute exercise on cardiovascular reactivity.

Although exercise may modulate cardiovascular reactivity to stress, its acute effects have not been studied extensively. The purpose of this study was to examine over time the acute effects of different durations of aerobic exercise on cardiovascular reactivity to stressors. Twenty-four sedentary men underwent minimal exercise, 1 or 2 hr of stationary cycling at 55% VO2max. Heart rate, blood pressure, and blood catecholamines were measured during cold pressor, Stroop, and public speech tasks 1, 3, and 24 hr after exercise. One or two hours of exercise attenuated blood pressure responses to stress. The attenuation was evident 3 hr following exercise and was most apparent on the cold pressor task. These effects were independent of epinephrine level and stress appraisal. The role of central sympathetic processes in the effects of exercise and methodologic implications are discussed.