Physiological Effects of Altitude on Outdoor Pursuits Casey McCauley ESS 777 Fall 2008
Factors to Consider • Mazzeo (2008) indicated two main factors which need to be considered when investigating the effects of altitude on athletic performance • These two factors are: • Degree or extent of hypoxia incurred • Intensity of the exercise bout • Necessary adjustments to these stressors need to be made by the central nervous system (CNS) and endocrine system
Physiological Responses • The CNS and endocrine system are responsible for such responses such as: • Increased cardiac output • As a result of increased heart rate and stroke volume • Increased arterial/venous difference • (a-v)O2 difference • Occurs as a result of increased muscle blood flow and oxygen extraction • Subudhi, A., Roach, R.,(2008) and Mazzeo, R.(2008) all indicate similar physiological responses to altitude.
Anaerobic Performance • Lundby et al. (2007) has indicated that no changes in Anaerobic performance occurs at altitude due to the nature of the immediate energy systems not requiring oxygen
Aerobic or Endurance Performance • Subudhi and Roach (2008) indicated that endurance performance at altitude can be confusing for athletes. • The data show a high degree of individuality and a more curvilinear relationship. • Past investigations have suggested a 1% decrement in VO2max for every 100 meters above 1500 meters. • Subudhi and Roach (2008) state that hypoxia exerts a wide array of systemic effects throughout the body with no definitive factor that can be manipulated to reduce the effects of altitude on endurance performance.
Endurance Performance • Rusko et al. (2004) indicated benefits to a “live high, train low” strategy for endurance athletes. • However, the authors concluded that although data exists supporting the strategy there is no definitive protocol which elicits optimum performance • This supports the idea of individuality in regard to acclimitization. • Rusko et al. (2004) also indicated controversial studies exist investigating the benefit of a “live high, train low” training strategy on sea level performances • Most studies appeared to be controversial in the results which showed benefits and no changes.
Endurance Performance • The idea of the “live high, train low” strategy is to induce some physiological changes, namely increased blood cell volume for increased oxygen carrying capacity. • Rusko et al. (2004) suggest a minimum amount of time for the “live high, train low” effect of altitude to take place. The authors state that at least 12 hours a day for at least 3 weeks at an altitude or simulated altitude of 2100 to 2500 meters.
Exercise Economy • Altitude has been reported to effect muscle mechanical efficiency • The result of altered muscle metabolic substrate utilization and its effect on the anatomical/physiological adaptation to high altitude. • Lundby et al. (2007) indicated no change in mechanical muscle efficiency during whole body exercise at altitudes up to 4300 meters. • This data is congruent with related research literature which has been conducted. • However, the authors admit that limitations within the study may affect the results. Especially other factors that were not examined such as muscle fiber recruitment, muscle acidosis, and muscle temperature.
Effects of Altitude on Specific Sports • Ingjer and Myhre (1992) suggested that elite cross country skiers benefit from altitude training. • The most significant finding the authors present was that skiers with initial low hemoglobin and hematocrit values experienced the greatest increases when training at altitude. • The authors also found that the increase in blood lactate concentration during a submaximal exercise test was significantly lower after training at altitude than before.
Effects of Altitude on Specific Sports • Makowski et al. (2006) found that exposure to cold and hypoxia elevate basal metabolic rate and exercise energy expenditure of skiing. • Chapman et al. (2007) surmised that a marathoner looking to add altitude training to their peak performance plans, residence at an altitude of 2000 to 2500 meters, a minimum of 20 hours per day, for 4 weeks, appears to hold the greatest potential for performance enhancement • The authors suggest that a “live high, train low” strategy could induce a 5% benefit in the marathon which translates to roughly a 8.5 minute savings in finishing time.
Effects of Altitude on Specific Sports • Hahn and Gore (2001) also found that reception to a “live high, train low” strategy is highly individual amongst elite level cyclists. • However, for those individuals that were receptive, data showed small improvements of up to 1% in events lasting approximately 45 seconds to 14 minutes.
Altitude Illnesses • Burtscher (2005) investigated the effects of training at altitude and some of the associated risks. • Acute mountain sickness (AMS), high-altitude cerebral edema (HACE), and high-altitude pulmonary edema (HAPE) are major are rare but severe life threatening illnesses. • Only individuals spending time at significantly high altitudes are at risk • Preventive measures like pre-acclimitization, slow ascent to altitude, sufficient intake of fluid and carbohydrates, and avoidance of alcohol and nicotine should be considered.
Summary • Altitude certainly has significant influence on outdoor pursuits • Specific physiological adaptations occur in response to exposure to altitude and these adaptations occur over time resulting in acclimitization • Certain training strategies can be devised for athletes looking to use altitude as a training tool to enhance performance. However, strategies should consider individual differences among athletes when devising a “live high, train low” plan. • Adhering to the suggested minimum values in order to obtain optimum adaptation is recommended • Altitude illness is apparent and a risk but mainly for individuals spending significant time at extremely high altitude or those not adhering to acclimitization recommendations.