Physical activity and plasma lipids.

The classification and metabolism of lipoproteins and their relation to the risk of coronary heart disease are briefly discussed. Cross-sectional studies indicate that people who practice endurance training tend to have higher levels of HDL, but lower plasma concentrations of VLDL, LDL and triglycerides than physically inactive persons of the same age and sex. A similar picture has emerged from longitudinal studies. The effects of physical training on the level of total cholesterol is less certain (but probably also less important since the essential part of plasma cholesterol is present in lipoproteins--LDL and HDL--which are considered to have antagonistic functions in the development of atherosclerosis). Forced training of rats resulted in a lowering of total concentrations of cholesterol (although there are some negative reports) and triglycerides, increased activity of lipoprotein lipase in the muscle, increased activity of the plasma enzyme LCAT (lecithin: cholesterol acyltransferase) and increased excretion of bile acids in the faeces. In human subjects who practice endurance training a similar increase in activity of the above enzymes has been demonstrated and this may be the basis for the effect of training on lipoprotein concentrations in plasma. It is concluded that physical activity of endurance type appears to have a favourable effect on the pattern of lipoproteins in the plasma (rise in HDL, fall in VLDL and LDL), and that consequently such training may have significance for the prevention of coronary heart disease.