Regulation of haemoglobin concentration at high altitude

On the mechanisms of stress-induced human spleen contraction: training for a higher blood oxygen-carrying capacity

Despite its comparatively limited size in humans, spleen has been shown able to expel red-blood cells in the circulation and thus augment blood oxygen-carrying capacity under certain physiologic conditions. In the present state-of-the-art review, the short- and long-term regulation of spleen volume will be discussed. With regards to the physiological mechanism underlying spleen contraction, sympathetic activation stands as the prime contributor to the response. A dose-dependent relationship between specific interventions of apnea, exercise and hypoxia (imposed separately or in combination) and spleen contraction alleges to the trainability of the spleen organ. The trainability of the spleen is further substantiated by virtue of cross-sectional and longitudinal studies reporting robust increases in both organ volume at rest and subsequent spleen contraction. Alternative ways to assess the relationship between hematologic gains and the magnitude of spleen contraction (i.e., the reduction of spleen volume) will be presented herein. In extension of changes in the conventional measures of hemoglobin concentration and hematocrit, assessment of hemoglobin mass and total blood volume using the (safe, low-cost and time-efficient) CO-rebreathing technique could deepen scientific knowledge on the efficiency of human spleen contraction.

High-level performances following low altitude training and tapering in warm environments in elite racewalkers

Current guidelines for prolonged altitude exposure suggest altitude levels ranging from 2000 to 2500 m to optimize an increase in total hemoglobin mass (Hbmass). However, natural low altitude locations (<2000 m) remain popular, highlighting the interest to investigate any possible benefit of low altitude camps for endurance athletes. Ten elite racewalkers (4 women and 6 men) underwent a 4-week "live high-train high" (LHTH) camp at an altitude of 1720 m (PIO2 = 121 mmHg; 20.1°C; 67% relative humidity [RH]), followed by a 3-week tapering phase (20 m; PIO2 = 150 mmHg; 28.3°C; 53% RH) in preparation for the World Athletics Championships (WC). Venous blood samples were withdrawn weekly during the entire observation period. In addition, blood volumes were determined weekly by carbon monoxide rebreathing during altitude exposure and 2 weeks after return to sea level. High-level performances were achieved at the WC (five placings among the Top 10 WC races and three all-time career personal bests). A slight but significant increase in absolute (+1.7%, p = 0.03) and relative Hbmass (+2.3%, p = 0.02) was observed after 4-week LHTH. In addition, as usually observed during LHTH protocols, weekly training distance (+28%, p = 0.02) and duration (+30%, p = 0.04) significantly increased during altitude compared to the pre-LHTH period. Therefore, although direct causation cannot be inferred, these results suggest that the combination of increased training load at low altitudes with a subsequent tapering period in a warm environment is a suitable competition-preparation strategy for elite endurance athletes.

Evaluation of dietary composition between hemoglobin categories, total body iron content and adherence to multi-micronutrients in preschooler residents of the highlands of Puno, Peru

BACKGROUND

The anemia prevalence is higher in highlands populations. It is assumed that iron deficiency anemia (IDA) in children is mainly due to low dietary intake. However, other suggest that high prevalence of anemia is due to an inappropriate hemoglobin (Hb) adjustment for altitude.

MATERIALS AND METHODS

Cross-sectional study conducted in 338 preschoolers (PSC) from Puno-Peru. Hb was measured in whole blood, and ferritin, Soluble transferrin receptor, and Interleukin 6 in serum.The dietary iron intake was assessed by 24-h dietary recall, using NutriCap Software. Hb concentration was assessed as adjusted or unadjusted for altitude.

RESULTS

With unadjusted Hb, the anemia prevalence was 4.7%, whereas after Hb correction, the prevalence raised-up to 65.6% (p < 0.001). Reciprocally, erythrocytosis proportion decreased from 20.35 to 0.30% (p < 0.001). Total Body Iron (TBI) showed that 7.44% had ID and 0.32% had IDA. PSC with normal unadjusted Hb levels have more protein and micronutrients intake than anemic ones. PSC with erythrocytosis consumed less fat, and more niacin and ascorbic acid than anemics. Total iron intake was lower in anemic than the other groups, but without statistical significance due to the standard deviation of the data in a small number of anemic PSC (n = 16). TBI, unadjusted Hb, and adjusted Hb were not different between groups consuming or not multimicronutrients.

CONCLUSIONS

The consumption of iron and iron status in children who live at high altitude is adequate, and that anemia could be due to other micronutrient deficiencies and/or that the adjustment of Hb by altitude is inappropriate.