Purpose This doctoral dissertation purposed 1) to examine effects of short-term supplementation with alpha-ketoglutaric acid (-KG) and 5-hydroxymethylfurfural (5-HMF) on exercise performance, oxidative stress and antioxidant levels in hot and cold environmental conditions (Study I), and 2) to evaluate effects of eccentric exercise training at low and moderate altitudes on exercise performance, oxidative stress levels and antioxidant status in pre-diabetic men (Study II).
Methods Study I: during a 5-weeks period, seven male young and well-trained participants performed 5 incremental treadmill tests to exhaustion under different temperature conditions (normal: 20C, cold: +7C, heat: +33C) and with different nutritional supplements (placebo or -KG and 5-HMF) prior to the tests applying a randomized cross over design. The first test was performed under normal temperature, the second and fourth under cold and the third and fifth test under heat conditions. Study II: in this non-randomised crossover trial, five pre-diabetic men conducted 9 downhill walking sessions (3 days/week, 3 consecutive weeks) at low altitude (from 1360 to 850 m) and one year later at moderate altitude (from 2447 to 2000 m). Exercise testing and the determination of parameters of oxidative stress and antioxidant capacity were performed pre- and post-training. Reactive oxygen metabolites and the biological antioxidant activity in blood samples from both studies were determined (Free Carpe Diem, Diacron International) before and after each exercise test.
Results Study I indicated that diacron reactive oxygen metabolites (dROMs) and maximal exercise performance remained unchanged in cold and hot conditions with and without short-term antioxidant supplementation. The biological antioxidant activity of plasma (BAP) was increased in both the cold with placebo (p = 0.040) and the cold with supplementation of -KG and 5-HMF (p = 0.008) compared to baseline without difference between conditions. Study II demonstrated that BAP increased after eccentric training at moderate altitude (p < 0.001) whereas dROMs remained unchanged. Also the BAP/dROMs ratio increased only after training at moderate altitude (p = 0.009). Maximum power output (Pmax) was enhanced after training at low altitude and the changes were significantly related to baseline BAP/dROMs ratio (r = 0.90, p = 0.037). No fasting plasma glucose improvement after exercise training was observed.
Conclusions Study I: it was concluded that short bouts of intense exercise in the heat or the cold seems not to generate significant oxidative stress in well-trained subjects and therefore pre-treatment with antioxidants may not have beneficial effects. In Study II, eccentric exercise training in pre-diabetic men improved performance only when performed at low altitude and these improvements were positively related to the baseline BAP/dROMs ratio. In contrast, three weeks of eccentric exercise training increased BAP levels and the BAP/dROMs ratio only at moderate altitude without improving performance. Thus, one might speculate that the BAP/dROMs ratio has to develop before performance improvements will occur at moderate altitude.