Høydehustrening kan virke mot sin hensikt

I denne studien utført ved Karolinska Institutet i Stockholm, ble forsøkspersonene plassert i et lavtrykks-kammer som etterligner forholdene under trening ved store høyder, eller såkalt høydehus-trening. Man målte forskjellige indikatorer for oksidativ treningseffekt, eller tilpasninger for bedre arbeidsevne ved oksygenmangel - meget viktig for utholdenhetsutøvere. Intensiteten var 65% av VO2max og studien varte i 4 uker. Resultatene var forbløffende. For enkelte indikatorer var det store forbedringer etter treningsprogrammet under normalt trykk, mens de samme indikatorene var nesten uendret under lavt trykk! Vi kan konkludere ut fra resultatene av denne studien at høydehus-trening hemmer optimal utvikling av oksidativ kapasitet i musklene, og derfor bør brukes med måtehold eller kun i korte faser.

Acta Physiol (Oxf). 2007 May 22;

Quantitative and qualitative adaptation of human skeletal muscle mitochondria to hypoxic compared with normoxic training at the same relative work rate.

Bakkman L, Sahlin K, Holmberg HC, Tonkonogi M.

Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden.

Aim: To investigate if training during hypoxia (H) improves the adaptation of muscle oxidative function compared with normoxic (N) training performed at the same relative intensity. Method: Eight untrained volunteers performed one-legged cycle training during 4 weeks in a low-pressure chamber. One leg was trained under N conditions and the other leg under hypobaric hypoxia (526 mmHg) at the same relative intensity as during N (65% of maximal power output, W(max)). Muscle biopsies were taken from vastus lateralis before and after the training period. Muscle samples were analysed for the activities of oxidative enzymes [citrate synthase (CS) and cytochrome c oxidase (COX)] and mitochondrial respiratory function. Results: W(max) increased with more than 30% over the training period during both N and H. CS activity increased significantly after training during N conditions (+20.8%, P < 0.05) but remained unchanged after H training (+4.5%, ns) with a significant difference between conditions (P < 0.05 H vs. N). COX activity was not significantly changed by training and was not different between exercise conditions [+14.6 (N) vs. -2.3% (H), ns]. Maximal ADP stimulated respiration (state 3) expressed per weight of muscle tended to increase after N (+31.2%, P < 0.08) but not after H training (+3.2%, ns). No changes were found in state four respiration, respiratory control index, P/O ratio, mitochondrial Ca(2+) resistance and apparent Km for oxygen. Conclusion: The training-induced increase in muscle oxidative function observed during N was abolished during H. Altitude training may thus be disadvantageous for adaptation of muscle oxidative function.