Background: Single bouts of muscle damaging eccentric exercise (EE) affect glucose metabolism negatively while single bouts of concentric (CE) and not muscle damaging eccentric exercise have positive acute short-term effects on glucose metabolism. It has been proposed that long-term endurance EE might be more effective in improving glucose metabolism than long-term CE when adjusted for energy expenditure. This would imply that adaptations of glucose metabolism are dependent on the type of exercise. Interleukin-6 (IL-6) released from the exercising muscles may be involved in and could therefore explain acute adaptations on glucose metabolism. The aim of the study was to investigate the effects of a single bout of CE and a single bout of EE inducing no or just mild muscle damage, matched for energy expenditure, on glucose metabolism.
Methods: 7 healthy but sedentary female participants (age 20.7 ± 2.9 years; BMI 22.45 ± 1.66 kg m(-2); VO2peak 39.0 ± 4.5 ml kg(-1) min(-1)) took part in a randomized cross over trial consisting of 1 h uphill (CE) respectively downhill (EE) walking on a treadmill. Venous blood samples were drawn before, directly after and 24 h after exercise. An oral glucose tolerance test (OGTT) was performed before and 24 h after exercise.
Results: CE and EE lead to comparable changes of glucose tolerance (area under the curve of the OGTT) (-16.0 ± 25.81 vs. -6.3 ± 45.26 mg dl(-1) h(-1), p = 1.000) and HOMA insulin resistance (-0.16 ± 1.53 vs. -0.08 ± 0.75, p = 0.753). Compared to baseline, IL-6 concentration increased significantly immediately after EE (1.07 ± 0.67 vs. 1.32 ± 0.60 pg ml(-1), p = 0.028) and tended to increase immediately after CE (0.75 ± 0.29 vs. 1.03 ± 0.21 pg ml(-1), p = 0.058). TNF-α concentration decreased significantly immediately after EE (1.47 ± 0.19 vs. 1.06 ± 0.29 pg ml(-1), p = 0.046) but not after CE (1.27 ± 0.43 vs. 1.24 ± 0.43 pg ml(-1), p = 0.686) compared to baseline.
Conclusions: Acute effects of a single bout of exercise inducing no or just mild muscle damage on glucose tolerance and insulin resistance seem to be primarily energy expenditure dependent whereas acute anti-inflammatory activity induced by a single bout of exercise appears to be rather exercise type dependent.
Trial registration: NCT01890876, clinicaltrials.gov, https://clinicaltrials.gov/.
Keywords: Concentric exercise; Eccentric exercise; Glucose metabolism; Interleukin 6; Tumor necrosis factor alpha.