Eccentric Exercise & Antioxidant Supplementation
Eccentric exercise is defined as the lengthening of the muscle while contracting, or opposing action that shortens the muscle. Slowing down the elongation of the muscle process is said to lead to an ability to build stronger muscles. Furthermore, it advances the process of muscle repair and increases metabolic rate. It is also shown to benefit lipid profile and insulin sensitivity.
In fact, research shows that an acute bout of eccentric exercise leads to insulin resistance that can last up to four days. Consequently, to further the benefits of eccentric exercise, athletes have supplemented with antioxidants during HIIT. Supplementing with antioxidants is controversial as it is said to prevent physiological training-induced adaptations.
A team of researchers out of a University in Greece set out to determine the minimum duration of eccentric exercise required to produce metabolic change. They also wanted to know if supplementing antioxidants during training interferes with physiological adaptation.
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The subjects in this study were a group of 16 healthy young men, who exercised 2-3 times a week on average. They were randomized into two groups: a control group and a vitamins group (both n=8). Participants in the vitamin group received one tablet of vitamin C and one of vitamin E a day for 9 weeks. The control group received a placebo pill in the same frequency and duration.
Before the study, participants had their muscle function measurements and blood drawn. After 5 weeks, the participants began their eccentric exercise training sessions. They trained 2 sessions per week for the remainder of the study. Blood samples and physiologic measurements were performed at week 0 and each week after exercise was introduced. Vitamin concentration levels, insulin and glucose measurements, lipids and lipoproteins were also measured.
In terms of vitamin concentration, plasma ascorbic acid increased in the vitamin group by 22.7% after 4 weeks of taking the vitamin supplements. In terms of muscle function, peak torque was also increased in both the vitamin and control group after 5 weeks of eccentric muscle training. There was no significant difference between the two groups.
Neither the eccentric exercise or vitamin supplementation effected plasma glucose and insulin concentration. However, for both the control and the vitamin group, there was a significant time effect on lipid and lipoprotein levels.
Specifically, plasma triglycerides and total cholesterol levels were significantly lower than baseline, while low-density lipoprotein levels saw a 10% reduction. Hence, results show that there was no effect of the antioxidant supplementation on plasma glucose and insulin concentration, in response to the supplementation or the eccentric training.
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In this study, four weeks of eccentric exercise training proved beneficial for lipid profiles, even while supplementing with antioxidants thought to suppress the effects. There were improvements on a weekly basis, improving muscle function, plasma glucose, and insulin concentration levels. In addition, 3 weeks of eccentric exercise training were needed before significant reductions in plasma triglycerides, total cholesterol, and low-density lipoprotein was seen.
Therefore, the results of this study prove a model for the design of future physical activity and training programs that aim to know the minimum duration of eccentric exercise needed to improve metabolic fitness and effect lipid profile.
Deli, C., Fatouros, I., Jamurtas, A., Koutedakis, Y., Theodorou, A., Tsiokanos, A., & Yfanti, C. (2017). “Chronic Eccentric Exercise and Antioxidant Supplementation: Effects on Lipid Profile and Insulin Sensitivity.” Journal of Sports Science and Medicine, 16, 375-382. You Might Like: