Supplementation with eicosapentaenoic acid-rich fish oil improves exercise economy and reduces perceived exertion during submaximal steady-state exercise in normal healthy untrained men.

Based on the effects of n-3 polyunsaturated fatty acids (PUFA) such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) on reduction of blood viscosity, we theorized that PUFA could improve aerobic performance by increasing oxygen supply to tissues. Twenty male subjects were randomly divided into two groups (n = 10): a fish oil group (FG) and a control (CG). Maximal oxygen uptake and oxygen uptake during submaximal exercise were measured using a cycle ergometer. For 8 weeks, the FG then ingested capsules containing 3.6 g/day of EPA-rich fish oil, while the CG took 3.6 g/day of a medium-chain triglyceride. After supplementation, erythrocyte EPA and DHA in the FG were significantly increased. In the FG, a negative linear correlation was detected in the change between erythrocyte EPA and whole oxygen uptake during submaximal exercise pre- and post-supplementation. The present study showed that EPA-rich fish oil supplementation improves exercise economy in humans.

Altitude training and haemoglobin mass from the optimised carbon monoxide rebreathing method determined by a meta-analysis.

OBJECTIVE: To characterise the time course of changes in haemoglobin mass (Hbmass) in response to altitude exposure. METHODS: This meta-analysis uses raw data from 17 studies that used carbon monoxide rebreathing to determine Hbmass prealtitude, during altitude and postaltitude. Seven studies were classic altitude training, eight were live high train low (LHTL) and two mixed classic and LHTL. Separate linear-mixed models were fitted to the data from the 17 studies and the resultant estimates of the effects of altitude used in a random effects meta-analysis to obtain an overall estimate of the effect of altitude, with separate analyses during altitude and postaltitude. In addition, within-subject differences from the prealtitude phase for altitude participant and all the data on control participants were used to estimate the analytical SD. The 'true' between-subject response to altitude was estimated from the within-subject differences on altitude participants, between the prealtitude and during-altitude phases, together with the estimated analytical SD. RESULTS: During-altitude Hbmass was estimated to increase by ∼1.1%/100 h for LHTL and classic altitude. Postaltitude Hbmass was estimated to be 3.3% higher than prealtitude values for up to 20 days. The within-subject SD was constant at ∼2% for up to 7 days between observations, indicative of analytical error. A 95% prediction interval for the 'true' response of an athlete exposed to 300 h of altitude was estimated to be 1.1-6%. CONCLUSIONS: Camps as short as 2 weeks of classic and LHTL altitude will quite likely increase Hbmass and most athletes can expect benefit.

Increased hemoglobin mass and VO2max with 10 h nightly simulated altitude at 3000 m.

PURPOSE: To quantify the changes of hemoglobin mass (Hbmass) and maximum oxygen consumption (VO2max) after 22 days training at 1300-1800 m combined with nightly exposure to 3000-m simulated altitude. We hypothesized that with simulated 3000-m altitude, an adequate beneficial dose could be as little as 10 h/24 h. METHODS: Fourteen male collegiate runners were equally divided into 2 groups: altitude (ALT) and control (CON). Both groups spent 22 days at 1300-1800 m. ALT spent 10 h/night for 21 nights in simulated altitude (3000 m), and CON stayed at 1300 m. VO2max and Hbmass were measured twice before and once after the intervention. Blood was collected for assessment of percent reticulocytes (%retics), serum erythropoietin (EPO), ferritin, and soluble transferrin receptor (sTfR) concentrations. RESULTS: Compared with CON there was an almost certain increase in absolute VO2max (8.6%, 90% confidence interval 4.8-12.6%) and a likely increase in absolute Hbmass (3.5%; 0.9-6.2%) at postintervention. The %retics were at least very likely higher in ALT than in CON throughout the 21 nights, and sTfR was also very likely higher in the ALT group until day 17. EPO of ALT was likely higher than that of CON on days 1 and 5 at altitude, whereas serum ferritin was likely lower in ALT than CON for most of the intervention. CONCLUSIONS: Together the combination of the natural and simulated altitude was a sufficient total dose of hypoxia to increase both Hbmass and VO2max.

Increase in serum growth hormone induced by electrical stimulation of muscle combined with blood flow restriction.

The purpose of this study was to investigate the role of muscle metaboreflex on exercise-induced growth hormone (GH) secretion. In order to accumulate metabolites within exercised muscle with minimized central motor activity, electromyostimulation (EMS) was performed combined with blood flow restriction (BFR). Seven men performed one-legged isometric knee extension evoked by EMS (frequency, 20 Hz; pulse duration, 400 µs; on-off ratio, 3-1 s). Just before the exercise, proximal portion of either a stimulated thigh (ST) or a non-stimulated thigh (NT) was compressed at 150 mmHg with an air-pressure cuff for the purpose of BFR. The compression was kept throughout the exercise session, and was released 2 min after the end of the exercise. Two exercise sessions (ST(BFR), BFR for ST; NT(BFR), BFR for NT) were separated by 1 week. ST(BFR) was aimed to accumulate metabolites within exercised muscle, whereas NT(BFR) was aimed to match mechanical stress with ST(BFR) without accumulating metabolites. Blood samples for hormonal measurements were taken from the antecubital vein before and after the exercise. Blood lactate increased immediately after the exercise in the NT(BFR), whereas it increased after the cuff deflation in the ST(BFR), suggesting that locally produced metabolites were retained and accumulated within the exercised muscle in the ST(BFR). Although serum cortisol and plasma noradrenaline increased in a similar manner in two conditions, serum immunoreactive GH (irGH) increased only in the ST(BFR). These results suggest that muscle metaboreflex plays an important role in the exercise-induced GH secretion, at least in terms of irGH secretion.

Cross-transfer effects of resistance training with blood flow restriction.

PURPOSE: This study investigated whether muscle hypertrophy-promoting effects are cross-transferred in resistance training with blood flow restriction, which has been shown to evoke strong endocrine activation. METHODS: Fifteen untrained men were randomly assigned into the occlusive training group (OCC, N = 8) and the normal training group (NOR, N = 7). Both groups performed the same unilateral arm exercise (arm curl) at 50% of one-repetition maximum (1RM) without occlusion (three sets, 10 repetitions). Either the dominant or nondominant arm was randomly chosen to be trained (OCC-T, NOR-T) or to serve as a control (OCC-C, NOR-C). After the arm exercise, OCC performed leg exercise with blood flow restriction (30% of 1RM, three sets, 15-30 repetitions), whereas NOR performed the same leg exercise without occlusion. The training session was performed twice a week for 10 wk. In a separate set of experiments, acute changes in blood hormone concentrations were measured after the same leg exercises with (N = 5) and without (N = 5) occlusion. RESULTS: Cross-sectional area (CSA) and isometric torque of elbow flexor muscles increased significantly in OCC-T, whereas no significant changes were observed in OCC-C, NOR-T, and NOR-C. CSA and isometric torque of thigh muscles increased significantly in OCC, whereas no significant changes were observed in NOR. Noradrenaline concentration showed a significantly larger increase after leg exercise with occlusion than after exercises without occlusion, though growth hormone and testosterone concentrations did not show significant differences between these two types of exercises. CONCLUSION: The results indicate that low-intensity resistance training increases muscular size and strength when combined with resistance exercise with blood flow restriction for other muscle groups. It was suggested that any circulating factor(s) was involved in this remote effect of exercise on muscular size.