Acute Effects Of Concentric And Eccentric Exercise On Glucose Metabolism And Interleukin-6 Concentra

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Acute effects of concentric and eccentric exercise on glucose metabolism and interleukin-6 concentration in healthy males

Acute muscle-damaging eccentric exercise (EE) negatively affects glucose metabolism. On the other hand, long-term eccentric endurance exercise seems to result in equal or superior positive effects on glucose metabolism compared to concentric endurance exercise. However, it is not known if acute non-muscle-damaging EE will have the same positive effects on glucose metabolism as acute concentric exercise (CE). Interleukin-6 (IL-6) released from the exercising muscles may be involved in the acute adaptations of glucose metabolism after CE and non-muscle-damaging EE. The aim of this study was to assess acute effects of uphill walking (CE) and non-muscle-damaging downhill walking (EE) on glucose metabolism and IL-6 secretion. Seven sedentary non-smoking, healthy males participated in a crossover trial consisting of a 1 h uphill (CE) and a 1 h downhill (EE) walking block on a treadmill. Venous blood samples were drawn before (pre), directly after (acute) and 24 h after (post) exercise. An oral glucose tolerance test (OGTT) was performed before and 24 h after exercise. Glucose tolerance after 1 and 2 hours significantly improved 24 hours after CE (-10.12±3.22%: P=0.039; -13.40±8.24%: P=0.028). After EE only the 1-hour value was improved (-5.03±5.48%: P=0.043). Acute IL-6 concentration rose significantly after CE but not after EE. We conclude that both a single bout of CE and a single bout of non-muscle-damaging EE elicit positive changes in glucose tolerance even in young, healthy subjects. Our experiment indicates that the overall metabolic cost is a major trigger for acute adaptations of glucose tolerance after exercise, but only the IL-6 production during EE was closely related to changes in glycaemic control.

Our results are not in line with the long-term results of Drexel et al. [1], who reported an equal or even slightly higher effectiveness of EE in improving glucose tolerance compared to CE despite the lower metabolic cost of EE. In our experiment CE improved glucose metabolism more effectively than EE despite lower metabolic cost of downhill walking. Johnson et al. [31] concluded that VO2 of downhill walking at the same velocity and opposite slope (in our experiment +16% and -16%) is approximately 0.5*VO2 of uphill walking. The myokine IL-6 is considered as an energy sensor of the muscle [19, 32] and the acute rise of IL-6 was significantly higher directly after CE compared to EE. Thus, the overall metabolic cost is assumed to be the major trigger for IL-6 release and the related metabolic adaptations to exercise.