Peak blood lactate and blood lactate vs. workload during acclimatization to 5,050 m and in deacclimatization

Abstract

Peak blood lactate ([Labl]peak) and blood lactate concentration ([Labl]) vs. workload (W) relationships during acclimatization to altitude and in the deacclimatization were evaluated in 10 Caucasian lowlanders at sea level (SL0); after approximately 1 wk (Alt1wk), 3 wk (Alt3wk), and 5 wk (Alt5wk) at 5,050 m; and weekly during the first 5 wk after return to sea level (SL1wk-SL5wk). Incremental bicycle ergometer exercises (30 W added every 4 min up to exhaustion) were performed. At Alt1wk and at Alt5wk, the experiments were repeated in hypobaric normoxia (Alt1wk-O2 and Alt5wk-O2). [Labl] was determined at rest and during the last approximately 30 s of each W. [Labl]peak was taken as the highest [Labl] during recovery. Acid-base status (pH and concentration of HCO-3 in arterialized capillary blood) was determined at rest. Mean [Labl]peak values were 11.5 (SL0), 8.0 (Alt1wk), 6.4 (Alt3wk), 6.3 (Alt5wk), 8.0 (SL1wk), 9.4 (SL2wk), 10.8 (SL3wk), 11.3 (SL4wk), and 11.6 (SL5wk) mM. At Alt1wk-O2 and Alt5wk-O2, peak W increased, compared with Alt1wk and Alt5wk, whereas no changes were observed for [Labl]peak. [Labl] vs. W was shifted to the left (i.e., higher [Labl] values were found for the same W) at Alt1wk compared with SL0 and partially shifted back to the right (i.e., lower [Labl] values were found for the same W) at Alt3wk and Alt5wk. At Alt1wk-O2 and Alt5wk-O2, [Labl] vs. W values were superimposed on that at SL0. At SL1wk-SL5wk, [Labl] vs. W values were shifted to the right compared with that at SL0. At Alt1wk, a condition of respiratory alkalosis was found, which was only partially compensated for during acclimatization. At SL1wk, the acid-base status was back to normal. We conclude that 1) the reduced [Labl]peak at altitude is still present for 2-3 wk after return from altitude; is not attributable to reduced peak W nor to hypoxia per se, nor to a reduced buffer capacity; alternatively, it could be related to some central determinants of fatigue. 2) The [Labl] vs. W leftward shift at altitude was due to hypoxia per se. 3) The factor(s) responsible for the [Labl] vs. W partial rightward shift during acclimatization could still be effective during the first weeks after return to sea level.

Acid?base balance at exercise in normoxia and in chronic hypoxia. Revisiting the "lactate paradox"

“…Despite the recovery of a large fraction of the pre-exposure working capacity, the LP is only scarcely or partially influenced by acute normoxia as shown initially by Edwards (1936) in an acclimatized Caucasian subject and subsequently confirmed by Cerretelli (1976b) in Caucasians and altitude Sherpas sojourning for up to 6-8 weeks at the base camp of Mt. Everest (5400 m) or above, by Grassi et al (1996) on Caucasians at 5050 m after 4 weeks of exposure and by Kayser et al (1996) in native Bolivian Mestizos at $4000 m.…”

“…Revisiting the so-called lactate paradox Resting blood lactate concentration ([La b ] rest ) was shown to be unchanged or only slightly increased after a prolonged (3 weeks to 3 years) sojourn at altitude (between 3800 and 6140 m) both in acclimatized Caucasians (Edwards 1936;Cerretelli 1976b;Bender et al 1989;Grassi et al 1996Grassi et al , 2001Van Hall et al 2001) or Chinese Han subjects (Ge et al 1994) and in altitude natives comprising Quechua from Chile (Edwards 1936), Sherpas of Nepal and Peruvian Indians (Cerretelli 1976a;Cerretelli et al 1982), Tibetans (Ge et al 1994) and Bolivian Mestizos . In the course of exercise, peak [La b ] is lower in chronic than in acute hypoxia (Bender et al 1989;Grassi et al 1996;Gladden 1996).…”

“…In the course of exercise, peak [La b ] is lower in chronic than in acute hypoxia (Bender et al 1989;Grassi et al 1996;Gladden 1996). At 4300 m and identical workloads or _ V V O 2 levels, the decrease is found both at submaximal and maximal exercise intensities (Fig.…”

Limiting factors to oxygen transport on Mount Everest 30�years after: a critique of Paolo Cerretelli?s contribution to the study of altitude physiology

“…A reduction in chronic hypoxia of the maximal rate at which lactate can be accumulated in blood, corresponding to the maximal lactic power (Margaria et al 1964) was demonstrated (Grassi et al 1995). The progressive reversibility of the lactate paradox phenomenon upon return to sea level as acclimatisation is lost was also demonstrated (Grassi et al 1996). A lower maximal blood lactate concentration in chronic hypoxia was documented also after supramaximal exercise of 30 s duration, but not of 10 s duration (Grassi et al 2001).…”

Exercise intolerance at high altitude (5050m): Critical power and W′

“…This reflects, in part at least, a limitation to muscle O 2 delivery and/or utilization rates consequent to the low arterial O 2 content and reductions in maximal cardiac output (Q T ), stroke volume (SV) and heart rate (HR) (Vogel et al, 1974) and maximal muscle blood flow (Q M ) (Calbet et al, 2003;Lundby et al, 2006). Furthermore, as the lactate threshold (or gas exchange threshold, GET) is also reduced at HA, at least acutely (Grassi et al, 1996;Myers et al, 2008), the metabolic stress associated with a particular supra-GET work rate (WR) is functionally elevated. For exercise at sea-level (SL), WRs that lie immediately above GET are relatively sustainable asV O 2 and the elevated blood lactate and proton concentrations ([L − ], [H + ]) are each able to stabilize (Poole et al, 1988;Whipp, 1994).…”