Persistence of the Lactate Paradox over 8 Weeks at 3800 m

Abstract

The arterial blood lactate [La] response to exercise increases in acute hypoxia, but returns to near the normoxic (sea level, SL) response after 2 to 5 weeks of altitude acclimatization. Recently, it has been suggested that this gradual return to the SL response in [La], known as the lactate paradox (LP), unexpectedly disappears after 8 to 9 weeks at altitude. We tested this idea by recording the [La] response to exercise every 2 weeks over 8 weeks at altitude. Five normal, fit SL-residents were studied at SL and 3,800 m (Pbar = 485 torr) in both normoxia (PIO2 = 150 torr) and hypoxia (PIO2 = 91 torr approximately air at 3,800 m). Arterial [La] and blood gas values were determined at rest and during cycle exercise at the same absolute workloads (0, 25, 50, 75, 90, and 100% of initial SL-VO2Max) and exercise duration (4, 4, 4, 2, 1.5, and 0.75 min, respectively) at each time point. [La] curves were elevated in acute hypoxia at SL (p < 0.01) and at 3,800 m fell progressively toward the SL-normoxic curve (p < 0.01). On the same days, [La] responses in acute normoxia showed essentially no changes over time and were similar to initial SL normoxic responses. We also measured arterial catecholamine levels at each load and found a close relationship to [La] over time, supporting a role for adrenergic influence on [La]. In summary, extending the time at this altitude to 8 weeks produced no evidence for reversal of the LP, consistent with prior data obtained over shorter periods of altitude residence.

Sea‐level haemoglobin concentration is associated with greater exercise capacity in Tibetan males at 4200 m

“…Comparing the highest and lowest values of each variable in the 21 Tibetans examined here,V O 2 peak /kg would differ by ß4 ml kg −1 min −1 over the range of P aCO 2 , by ß10 ml kg −1 min −1 over the range of QT/kg, and by ß16 ml kg −1 min −1 over the range of DM/kg. In contrast to the ß30% increase in power output on breathing pure O 2 observed among European subjects acclimatized to 4200-4300 m (Reeves et al 1992;Pronk et al 2003), the Tibetans (n = 21) and Han Chinese (n = 8) exhibited only a 10% increase in maximal power output.…”

“…Supplemental (100%) O 2 given during exercise increases peak work rate in Tibetans by only a third of that seen in Caucasian lowlanders acclimatized to 4200-4300 m altitude (Reeves et al 1992;Pronk et al 2003), with no difference between high-and low- [Hb] groups. This may represent reduced mitochondrial content as an adaptation to chronically reduced O 2 availability and is consistent with the well-known plasticity of mitochondria with training and detraining even at sea level.…”

Muscle intracellular oxygenation during exercise: optimization for oxygen transport, metabolism, and adaptive change

“…In normal natives living at about 4,000 m above sea level, breathing 55% O 2 resulted in no increase in _ VO 2 max above that found on the same day breathing ambient air (Wagner et al 2002). Even acclimatized lowlanders will normalize _ VO 2 max when exercising breathing 100% O 2 at altitude (Pronk et al 2003) eliminating the roughly 30% loss of _ VO 2 max associated with an altitude of 4,000 m. This finding suggests that, like sedentary subjects at sea level, metabolic capacity in Andean high altitude natives has been reduced so that it runs maximally even in hypoxia. One can argue that this conserves energy that would be otherwise required to maintain higher metabolic capacity than can be utilized in the absence of enough O 2 .…”

Lactate Metabolism at High Altitude

“…The study of Pronk et al (2003) suffers from a poor methodological design. First, only four sea-level residents of mixed gender participated in the study.…”

“…Other studies that do not observe a lactate paradox are not mentioned. The senior author on the paper of Pronk et al (2003) is even the first or a co-author on two of these papers. (Beatty et al, 2002;Calbet et al, 2003;Dempsey et al, 1972;Klausen et al, 1966;Lundby & van Hall, 2002;Wagner et al, 2002).…”