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effect of altitude on lactate threshold

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  • Stéphane Beroud
    Dear all, In assessing lactate curve on uphill cross-country ski practitioners (age between 16 and 25) at 2800 meters above sea level, I was very surprised to
    Message 1 of 2 , Dec 1, 2004
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      Dear all,
      In assessing lactate curve on uphill cross-country ski practitioners (age between 16 and 25) at 2800 meters above sea level, I was very surprised to see that their Lactate-against-HR anaerobic threshold (beaver method) is lag to the right against the same protocol at 0 meter of altitude. These athletes are trained, altitude exposition was acute (up and down in the same day and 0 meter test 1 week after), 2800 meter assessment room was warm and hydrated. According with many authors, we found that the power at this threshold was decreased, the basal level and the blood lactate concentration at wich this threshold is set were increased, basal heart rate and heart rate for the same power were increased but no one described this lag (see figure below). One author (last JEP conference) found the same effect as us but she doesn’t make any explanation. Regarding metabolism, in lack of oxygen we should have onset of anaerobic metabolism that would start earlier but for us there is no trend of that. Is there physiological explanation of this phenomenon? Because as we choose the HR at this threshold to train these athletes, if we are out of basal comprehension we could train them at too high level to support training charge and moreover without any expected effect on their performance. Thanks a lot to give me your opinion.
      Best regards
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      Dr Stéphane Béroud
      Médecin Attaché
      Recherche clinique
      05 62 17 49 66
      Stephane.Beroud@...
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      Dr Stéphane Béroud

      Médecin Attaché

      Recherche clinique

      05 62 17 49 66

      Stephane.Beroud@...

      MEDES-IMPS

      BP 4404

      31 405 Toulouse  Cedex 4

      +33562174950

      fax:+33562174951

       

    • Dr. Anup Adhikari
      Dear Dr. Beroud , I would like to add a little bit to your discussion on effect of altitude on lactate threshold. At 2000m altitude , a small change occurs
      Message 2 of 2 , Dec 13, 2004
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        Dear  Dr. Beroud ,

        I would like  to add a little bit to your discussion on effect of altitude on lactate threshold.

        At 2000m altitude , a small change occurs in hemoglobin percentage saturation with oxygen and PO2 reduced o about 78mmHg. But hemoglobin remain 90% satured with oxygen due to S-shaped oxyhemoglobin dissociation curve. This relatively small arterial saturation exerts little effect on mild exercise at 2000m altitude. But if the exercise is more than the maximum, performance may l deteriorate.

        Hyperventilation at high altitude increases the alveolar PO2 but reduces the PCO2. alveolar PCO2 ma drop as low as 10mmHg during prolong stay at high altitude. This decrease of PCO2 results increase of pH resulting body fluid more alkaline . Hence, a general depression in maximum lactate concentration become apparent during maximum exercise at high altitude more than 4000m.

         

        This  is well known that on immediate exposure  to high altitude , a given submaximal load  increases blood lactate concentration more than the value obtained at sea level .  This might be due to more  dependence on anaerobic glycolysis with altitude hypoxia. But it is interesting that  the same submaximal and maximal exercise with large muscle groups after several weeks of hypoxic exposure produces lower lactate level, despite a lack of increase in either VO2max or regional blood flow in active tissues. The question arises concerning  this apparent physiological contradiction is  termed as lactate paradox. Thus the lactate paradox raise the question that how is lactate accumulation reduced without a concomitant increase in tissue oxygenation, when the hypoximia associated  with high altitude should promote lactate accumulation ( McArdle et al 2001).

         

        Bender et al ( 1989 ) revealed that the lactate paradox is due to reduced release of glucose mobilizing hormone epinephrine during chronic high altitude exposure. Glucose is the source of anaerobic energy and lactate formation . Hence , reduction in glucose mobilization  blunts the capacity for lactate  formation ( Mcardle et al 2001 ). Activation of  the glycolytic patway can be inhibited by the reduction of intracellular ADP during long term altitude exposure to high altitude . In addition to that , depressed lactate formation during maximal exercise may partly reflect an overall reduced central nervous system drive, which would blunt the capacity for all out physical effort ( Kayser et al 1993, Mazzeo et 1994 ). According to Kayser et al (1993) decreased buffering capacity accompanied by high altitude acclimatization is not apparently related to the reduction of lactate accumulation in blood  at high altitude.

        I think before final commencement more studies are to be required.

         

         

        Anup Adhikari, M.Sc, Ph.D

        Exercise Physiologist  and Level 2 Kinanthropometrist ( ISAK)

        Bangladesh Institute of Sports ( BKSP),

        Zirani, Savar, Dhaka

        Bangladesh

        e-mail: dranupadhikari@...

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