Red Blood Cell Volume and the Capacity for Exercise at Moderate to High Altitude

Abstract

Hypoxia-stimulated erythropoiesis, such as that observed when red blood cell volume (RCV) increases in response to high-altitude exposure, is well understood while the physiological importance is not. Maximal exercise tests are often performed in hypoxic conditions following some form of RCV manipulation in an attempt to elucidate oxygen transport limitations at moderate to high altitudes. Such attempts, however, have not made clear the extent to which RCV is of benefit to exercise at such elevations. Changes in RCV at sea level clearly have a direct influence on maximal exercise capacity. Nonetheless, at elevations above 3000 m, the evidence is not that clear. Certain studies demonstrate either a direct benefit or decrement to exercise capacity in response to an increase or decrease, respectively, in RCV whereas other studies report negligible effects of RCV manipulation on exercise capacity. Adding to the uncertainty regarding the importance of RCV at high altitude is the observation that Andean and Tibetan high-altitude natives exhibit similar exercise capacities at high altitude (3900 m) even though Andean natives often present with a higher percent haematocrit (Hct) when compared with both lowland natives and Tibetans. The current review summarizes past literature that has examined the effect of RCV changes on maximal exercise capacity at moderate to high altitudes, and discusses the explanation elucidating these seemingly paradoxical observations. DOI: https://doi.org/10.2165/11632440-000000000-00000Posted at the Zurich Open Repository and Archive, University of Zurich ZORA URL: https://doi.org/10.5167/uzh-69166 Accepted Version Originally published at: Jacobs, Robert A; Lundby, Carsten; Robach, Paul; Gassmann, Max (2012). Red blood cell volume and the capacity for exercise at moderate to high altitude. Sports Medicine, 42 (8) clear. Certain studies demonstrate either a direct benefit or decrement to exercise capacity in 34 response to an increase or decrease, respectively, in RCV; whereas, other studies report Andean natives often present with a higher percent hematocrit (Htc) when compared to both 39 lowland natives and Tibetans. The current review summarizes past literature that has examined 40 the effect of RCV changes on maximal exercise capacity at moderate to high altitudes, and 41 discusses the explanation elucidating these seemingly paradoxical observations.

Relationship between excessive erythrocytosis and acute mountain sickness: a field study

“…We also observed that the HCT had a more extensive elevation in the 24-h group, while the RBC count had a slight reduction, which would indicate that the individuals had suffered transient hemodilution upon acute high-altitude exposure, which was conflicted with the view that acute pachyhemia occurs upon exposure to high altitude. Nevertheless, the re-exposure group had the highest RBC count, which was in agreement with several studies on migration and natives of high altitude [ 1 , 3 , 4 , 15 ].…”

Twenty‐eight days at 3454‐m altitude diminishes respiratory capacity but enhances efficiency in human skeletal muscle mitochondria

“…These data suggest that the importance of mitochondrial parameters on exercise performance shift from a primary significance of respiratory capacity (13) to one of efficiency when going from normoxic to hypoxic exercise. The efficiency of cellular oxygen utilization becomes paramount because of the increasing diffusion limitations of oxygen transport that parallel the increase in elevation (34) vs. the convective limitation in oxygen delivery near sea level (35).…”

Mitochondrial function in human skeletal muscle following high‐altitude exposure

“…Approximately 14 days was previously determined appropriate to spend at moderate altitude prior to a competition in order to enhance exercise capacity along with the improvement in oxygen‐carrying capacity (Schuler et al 2007). As elevation increases, at somewhere between 3500 and 4500 m and above, the diffusive limitations of oxygen transport negate improvements in oxygen‐carrying capacity (Robach et al 2008; Jacobs et al 2012). Thus, maintaining mitochondrial capacity, as is presented in the present study, or even enhancing mitochondrial capacity (Vogt et al 2001; Schmutz et al 2010; Vogt & Hoppeler, 2010) may be necessary in order to maintain, or improve, exercise capacity.…”

“…Determinants of exercise performance change as elevation increases, shifting from more convective limitations of oxygen transport and peripheral origin of fatigue at lower elevations to diffusive limitations of oxygen and centrally mediated origin of fatigue at higher elevations (Amann et al 2007;Robach et al 2008;Jacobs et al 2012). Approximately 14 days was previously determined appropriate to spend at moderate altitude prior to a competition in order to enhance exercise capacity along with the improvement in oxygen-carrying capacity (Schuler et al 2007).…”