Tuesday, June 7, 2016

Exercise as Therapy: Dyslipidemia

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           Dyslipidemia is a group of disorders of lipoprotein metabolism entailing elevated blood levels of certain forms of cholesterol and triglyceride. Primary dyslipidemia is caused by environmental and genetic factors are by far the most frequent, accounting for 98% of all cases. Isolated hypercholesterolemia and combined dyslipidemia are the most frequent types of dyslipidemia, and are due to excessive intake of fat in most people. These types of dyslipidemia entail an elevated risk of atherosclerosis. Isolated hypercholesterolemia is characterized by elevation of only low-density lipoprotein (LDL) cholesterol, while combined dyslipidemia is characterized by elevated triglyceride, elevated LDL, intermediate-density lipoprotein (IDL) and very low-density lipoprotein (VLDL) cholesterol and lowered high-density lipoprotein (HDL) cholesterol. When the concentration of LDL is high, the particles are pressed into the intima where they are oxidized and taken up by macrophages. This leads to the formation of fat lesions and subsequently to atherosclerosis with intra- and extracellular cholesterol deposition, fibrosis, cell death and actual occlusive disease. Triglyceride elevation with a concomitant slight cholesterol elevation also entails elevation of IDL and VLDL particles in the blood. These particles are trapped in the intima, possibly even more easily than LDL particles, and thereby also promote the development of atherosclerosis. The low concentration of HDL particles probably entails that the removal of cholesterol from the blood is reduced, thereby indirectly enhancing atherosclerosis.1

Evidence for Physical Training
           The effect of physical activity on HDL is clinically relevant, although it is smaller than the effect that can be achieved through the use of lipid-lowering drugs. Exercise enhances the ability of the muscles to burn fat to a greater extent instead of glycogen. This is mediated by activation of a number of enzymes in the skeletal muscles necessary for lipid metabolism. There are no general contraindications, but the training should take into account comorbidities. Patients with CHD should retains from intensive exercise. Patients with hypertension should perform strength conditioning with light weight and a low contraction rate.1

Type and Amount of Training
The amount of physical training should be high, but the intensity can be either moderate or high. Aerobic exercise consisting 4 to 6 days a week for at least 30 minutes a session at moderate to vigorous intensity physical activity, with an expenditure of at least 200 kcals/day. It has been indicated that greater benefits are achieved when the duration of physical activity is lengthened to 60 to 90 minutes daily, and that 60 or more minutes of daily physical activity is recommended from the American Association of Clinical Endocrinologists’ for weight loss or weight loss maintenance. Daily physical activity goals can be met in a single session or in multiple sessions throughout the day by breaking activity up.2

1Pedersen, B.K., & Saltin, B. (2006). Evidence for prescribing exercise as therapy in chronic disease. Scandinavian Journal of Medicine & Science in Sports, (16)S1, 3-63. doi:10.1111/j.1600-0838.2006.00520.x

2 Jelliner, P.S., Smith, D.A., Mehta, A.E., Ganda, O., Handelsman, Y., Rodbard, H.W., Shepard, M.D., & Seibel, J.A. (2012). American Association of Clinical Endocrinologists’ guidelines for management of dyslipidemia and prevention of atherosclerosis. Endocrine Practice, (18)S1, 1-78.

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