ABSTRACT
The changes in serum lipid levels caused by continuous, long-term exertion are mainly due to increased energy needs in working muscles. Changes in blood triglyceride content during prolonged exercise reflect the enhanced utilization of fatty acids as energy substrates. The fatty acids originate from the adipose tissue after the hydrolysis of triglycerides by hormone-sensitive lipase which is activated by enhanced catecholamines during prolonged exercise. Serum free fatty acids have aroused interest because artificially, with heparin-raised free fatty acids, have been reported to have a sparing effect on the muscle glycogen depletion during prolonged exercise. The alterations in the serum total cholesterol concentrations during the exercise of even relatively long duration are usually small. If the serum cholesterol is followed for some days after a strenuous, long-term exertion, a significant reduction in total cholesterol is obtained. During severe prolonged exertion serum phospholipids have also been shown to decrease considerably from the fasting values.
