As measured in healthy sedentary individuals
Disorders in the metabolism of glucose and lipids have reached an epidemic dimension. Important reasons for this tremendous problem are overweight and a lack of exercise. There are plenty of data verifying a positive effect of exercise on glucose and lipid metabolism. However, no data are available on different ways of training, e.g. the comparison of hiking uphill versus hiking downhill. H. Drexel and colleagues found that in healthy sedentary individuals hiking downhill improves glucose tolerance more than hiking uphill.
The positive influence of exercise on reducing blood glucose is well known. There are, however, two different ways by which skeletal muscle can be exercised: concentric and eccentric muscle work. Concentric muscle work is defined as active shortening of muscles, e.g. by stepping upwards, whereas eccentric muscle work is defined as active resistance to stretching, e.g. by stepping downwards. Although the effects of exercise (i.e. the combination of concentric and eccentric muscle contraction) on glucose metabolism have been well established, there are no data on the specific metabolic effects of concentric versus eccentric muscle work in humans. "Our study, therefore, represents a completely new approach to evaluate the effects of different types of exercise!" outlined H. Drexel.
Forty-five healthy sedentary volunteers were recruited through the media. They were allocated randomly to two groups, one beginning with 2 months of concentric, the other with 2 months of eccentric exercise, followed by a cross-over period for further 2 months (Figure 1). By this design, every participant performed both ways of exercise in the course of the study. Participants were advised to exercise from 3 to 5 times a week. The exercise comprised a steady uphill/downhill hike over a difference in altitude of 600 meters. For the opposite way, a cable car was used.
At the beginning of the study and after each exercise period of 2 months a full metabolic profile (glucose levels and different lipid parameters) and an oral glucose tolerance test, which measures the cabability of the body to remove orally administred glucose out of the blood over a period of two hours, were obtained.
Compared to the beginning of the study, the blood glucose was removed much faster in the group of participants after hiking downhill. In medical terms, the area under the glucose curve illustrating the levels of blood glucose after 1 and 2 hours after glucose intake was improved by only 9.4% along with hiking uphill, but by highly significant 25.0% along with hiking downhill (Figure 2).
Hiking downhill improves glucose tolerance more than hiking uphill
In healthy sedentary individuals eccentric muscle training (hiking downhill) improves glucose tolerance more than concentric muscle training (hiking uphill). H. Drexel concluded: "Because many diabetic individuals are not able to perform concentric muscle exercise due to their age or concomitant diseases, eccentric muscle exercise should be tested as an alternative exercise modality for diabetic patients."
Source: Eurekalert & othersLast reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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