Thursday, December 11, 2014

Altitude Acclimation: Potential Application for Improved Exercise Economy

The "big three" determinants of endurance exercise performance are VO2max, pH threshold (sustainable pace) & exercise economy. We could also include anaerobic capacity and maximal speed/power as components that could determine the outcome of a sprint finish.

The importance of running economy has been documented many times, and is often regarded as a strong predictor of performance, especially between individuals with similar VO2max values (Saunders et al. 2004; Daniels 1985).

I've written on training for economy in the past. Training strategies such as hill sprints, resistance training, plyometrics or high intensity intervals have all shown improvements in economy.  In two studies, Saunders et al. (2004, 2009)  have also shown improvements in running economy following altitude acclimation. A study by Czuba et al. (2014) produced similar results in elite level biathletes and Latshang et al. in mountaineers (2013).

Potential mechanisms? Stays at altitude are not likely to result in improved power or stiffness of the muscle tendon system...

But, remember those uncoupling proteins? Perhaps altitude exposure down-regulates uncoupling protein gene expression, decreasing # of those uncoupling proteins (Levett et al., 2012). This would help maintain that H+ gradient between the intermembrane space and mitochondrial matrix - ensuring that more H+ is available to "run" ATPase. Or perhaps an increase in economy, measured by O2 consumption, is due to a change in substrate utilization. Utilizing more glucose and fewer fatty acids would decrease O2 cost, but net energy cost may or may not change (Shaw et al., 2014). This change could potentially be detrimental to endurance performance as endogenous CHO stores are limited.

So, really we need more research to evaluate changes in uncoupling proteins and energy cost, independent of O2 uptake.

An inverse relationship between economy and VO2max has been documented (Hunter et al., 2005). But, could altitude exposure provide a pathway to increasing or preserving VO2max while also improving economy?

References

Czuba, M., Maszczyk, A., Gerasimuk, D., Roczniok, R., Fidos-Czuba, O., Zajac, A., . . . Langfort, J. (2014). The Effects of Hypobaric Hypoxia on Erythropoiesis, Maximal Oxygen Uptake and Energy Cost of Exercise Under Normoxia in Elite Biathletes. J Sports Sci Med, 13(4), 912-920.

Hunter, G. R., Bamman, M. M., Larson-Meyer, D. E., Joanisse, D. R., McCarthy, J. P., Blaudeau, T. E., & Newcomer, B. R. (2005). Inverse relationship between exercise economy and oxidative capacity in muscle. Eur J Appl Physiol, 94(5-6), 558-568.


Latshang, T. D., Turk, A. J., Hess, T., Schoch, O. D., Bosch, M. M., Barthelmes, D., . . . Bloch, K. E. (2013). Acclimatization improves submaximal exercise economy at 5533 m. Scand J Med Sci Sports, 23(4), 458-467.


Levett, D. Z., Radford, E. J., Menassa, D. A., Graber, E. F., Morash, A. J., Hoppeler, H., . . . Murray, A. J. (2012). Acclimatization of skeletal muscle mitochondria to high-altitude hypoxia during an ascent of Everest. FASEB J, 26(4), 1431-1441.


Saunders, P. U., Telford, R. D., Pyne, D. B., Cunningham, R. B., Gore, C. J., Hahn, A. G., & Hawley, J. A. (2004). Improved running economy in elite runners after 20 days of simulated moderate-altitude exposure. J Appl Physiol (1985), 96(3), 931-937.


Saunders, P. U., Telford, R. D., Pyne, D. B., Hahn, A. G., & Gore, C. J. (2009). Improved running economy and increased hemoglobin mass in elite runners after extended moderate altitude exposure. J Sci Med Sport, 12(1), 67-72.


Shaw, A. J., Ingham, S. A., & Folland, J. P. (2014). The valid measurement of running economy in runners. Med Sci Sports Exerc, 46(10), 1968-1973.

No comments:

Post a Comment