Effects of hypoxic exercise conditioning on work capacity, lactate, hypoxanthine and hormonal factors in men

The effects of docosahexaenoic acid supplementation and exercise on growth hormone and insulin-like growth factor I serum levels during chronic hypoxia in rats

BACKGROUND

In this study we examined the effects of docosahexaenoic acid (DHA) on growth hormone (GH), insulin-like growth factor I (IGF-I) and insulin-like growth factor binding protein-3 (IGFBP-3) in response to chronic hypoxia and exercise training in hypoxic conditions.

METHODS

Thirty-five rats were divided into five groups; control group (C), hypoxia group (H), hypoxia-exercise group (HE), hypoxia-docosahexaenoic acid group (HD), hypoxia-exercise-docosahexaenoic acid group (HED). A treadmill exercise was performed as 30 m/min for 20 min/day, 5 days per week for 28 days at level grade for the exercising groups (HE and HED). DHA was given to the HD and HED groups every day orally (36 mg/kg). The animals, except for the C group, were exposed to hypoxia for 28 days.

RESULTS

Serum levels of GH and IGF-I in the H group decreased after chronic hypoxia (p<0.001). GH and IGF-I in the HD group also decreased compared with the C group (p<0.05, p<0.01, respectively). GH in C group did not show significant difference compared with the HE and HED groups. Decreased serum level of IGF-I was observed for the HED group (p<0.05).

CONCLUSIONS

According to our findings, chronic hypoxia exposure decreases serum levels of GH, and IGF-I and exercise training have a slightly positive effect on GH/IGF-I axis during hypoxia. In addition, DHA supplementation slightly increases GH and IGF-I serum levels in hypoxic conditions. However, this effect on GH/IGF-I axis during hypoxia is not strong compared with exercise. Therefore, we concluded that exercise and/or DHA supplementation does not have additional positive effect on these hormones in hypoxic conditions.

Influence of moderate altitude on blood lactate and heart rate in a standardized exercise test in healthy volunteers

Nineteen healthy volunteers were exposed to a standardized exercise test at sea level (SLa), at an altitude of 1700 m before (1700a) and after a moderate 10-day mountain training (1700b), with a final control four weeks later at sea level (SLb). Vital signs, blood lactate and arterial oxygen saturation were determined prior, during or after the exercise test. Whereas systolic blood pressure and heart rate at rest did not change substantially, diastolic blood pressure decreased at the final control (SLb, p<0.05) and oxygen saturation was significantly lower at 1700 m (1700a, 1700b, p<0.01). Lactate at rest increased from 1.16 (SLa) to 1.97 (1700a) mmol/l after acute exposure followed by a slight reduction after adaptation (p<0.05). The mean maximum lactate levels were as follows: 6.03, 10.56, 6.22 and 8.75 (p<0.01). The mean maximum performance increased during the study (225.6, 223.3, 231.6, 248.1 Watt, p<0.01). Lactate versus workload curves did not show a marked shift to the right. No significant changes of maximum heart rates during the exercise test were found. In conclusion, a sojourn at 1700 m provokes an increase of lactate levels with subsequent reduction after acclimatization and has a significant positive impact on the mean maximum performance after moderate mountain training.

Effects of long-term hypoxia and hypoxic exercise on brain monoamine levels in rat

This study clarified the effects of long-term hypoxia and hypoxic exercise on monoamines in the whole brain, and in four specific regions of the rat brain. The male Wistar rat progenitors (P1 group) were randomly assigned to three groups: hypoxia (16.0% oxygen) and exercise (MHE-P1), hypoxia and sedentary (MHS-P1), normoxia and sedentary (MNS-P1). The male children of P1 (the first generation of hypoxic rats; F1) were randomly divided into two groups: hypoxia and exercise (MHE-F1) and hypoxic sedentary (MHS-F1). The monoamines of whole brain were measured in P1 males, and monoamines of cerebellum, frontal lobe, striatum and hippocampus were measured in F1 males. The monoamine levels of MHE-P1 were significantly lower than those of MHS-P1 and MNS-P1. No significant difference was found in monoamine levels between MHS-P1 and MNS-P1. Epinephrine, norepinephrine, and dopamine levels of the MHE-F1 group significantly decreased in the frontal lobe, cerebellum and striatum, compare with the other groups (hypoxic and sedentary; normoxic and sedentary, respectively). These monoamines in the hippocampus were not influenced by the hypoxia or hypoxic exercise conditions. This study suggests that long-term hypoxic exercise decreased monoamine levels in whole brain, and that sensitivity to hypoxia and hypoxic exercise differed according to brain region.