Eccentric endurance exercise economically improves metabolic and inflammatory risk factors

Introduction: Exercise is a cornerstone of cardiovascular prevention. Because many individuals are not willing or not able to perform regular exercise, new methods of exercise (like eccentric exercise) are necessary. Eccentric endurance exercise is supposed to be less strenuous than concentric exercise but its effects on glucose and lipid metabolism in relation to energy expenditure are unclear. Methods: We randomly allocated 45 healthy sedentary individuals to one of two groups, each hiking upwards or downwards for 2 months, with a crossover for a further 2 months; for the opposite way, a cable car was used. The difference in altitude was 540 metres; the distance was covered between three and five times a week. Energy expenditure was assessed for each hiking period. Results: Both eccentric and concentric endurance exercise improved glucose tolerance vs. baseline (by 4.1%, p=0.136; 6.2%, p=0.023, respectively). Of note, adjustment for energy expenditure per exercise unit (127 +/- 22kcal/unit with eccentric and 442 +/- 78kcal/unit with concentric exercise) revealed a significantly greater improvement of glucose tolerance per kilocalorie spent by eccentric than by concentric exercise (4-times more economical; 0.1123mg h/dl/kcal vs. 0.0245mg h/dl/kcal; p=0.038). Also the decrease of low-density lipoprotein (LDL) cholesterol per kilocalorie spent was significantly stronger with eccentric exercise (0.0982mg/dl/kcal vs. 0.0346mg/dl/kcal, p=0.014). Serum levels of C-reactive protein and creatine kinase activity were reduced in both groups. Conclusion: Eccentric endurance exercise economically improves glucose tolerance and LDL cholesterol. It therefore is a promising new exercise modality for individuals who are not able to participate in more strenuous exercise regimens.