By Iris Saar, M.Sc Exercise Science candidate, ACSM CPT, RRCA
Athletic performance in extreme environments
Competitive athletic events are the apex of many athletes’ professional career. Developed countries begin cultivating their athletes from a younger age through a community-based recreational sports programs and collegiate level following the school years. Out of the 600,097 high school male athletes who participate in NCAA events, (National Collegiate Athletic Association), less than 5% turn into collegiate athletes and about 1.9% reach division I participation. Female high schoolers show a slightly higher fraction of about 6.1% to collegiate level and 2.7% for division I participation (Smeyers, 2019). Those data demonstrate the fierce competition in the US to become a competitive athlete, and the accompanying intrinsic incentives to engage in high-volume training under demanding environmental conditions. A lengthy process, athletes are required and motivated to compete in various events throughout a season, often traveling globally and exposed to different ambient conditions then their home training base.
This blog post reviews strategies to prepare an athlete for the extreme environment events. Extreme conditions often include altitude, heat or cold environments and challenge the athlete to compete under risk for low oxygen tension conditions such as hypoxia, normoxia and exposure to heat or cold injuries (Powers & Howley, 2019). Studies have shown that pre-adjustment might help to enhance performance by an early adaptation, or acclimation to the target race environment; repeated exposure during training to hot conditions (≥25º Celsius) facilitates heat acclimation (HA). This enhances performance through adaptations of the cardiovascular and circulatory systems, increased plasma volume and other factors discussed later (Pryor, 2019; Powers & Howley, 2019).
An athletic event is used in this post in a retrospective - The 2019 World Athletics’ women championships marathon, held recently in September 27, 2019. The race, organized and governed by World Athletics (formerly IAAF, or International Amateur Athletic Federation), was held in Doha, Qatar. The country is geographically located on the west coast of the Persian Gulf. The topography is mainly desert, flat lands and the climate during the summer is hot and humid. The mean relative humidity in the month of September, when race is held, is amongst the height during the year averaging at 61% (Qatar Meteorology Department, access date April 15, 2020). Temperatures during the summer months (June through September) can reach 122º Fahrenheit or 50º Celsius (Crystal, J.A. & Duke, A., 2020). Not only is the climate extremely hot, but the overall air quality is unhealthy due to sand dust blowing from sand dunes into populated areas and affecting its residents’ respiratory health and causing or worsening asthma, bronchitis and pneumonia (Teather, 2013).
The criterion for selecting a physical host location for world championship athletic events is based on many factors, some are performance-based. World Athletics has a pre-defined bidding application process and hosts sites are evaluated and selected based on compliance to terms set forth in the IAAF manual (IAAF Bidding Rules 21,in force from 1 January 2019). Interestingly, the manual does include a risk assessment clause which ranges from 1 (low likelihood of risk) to 5 (almost certain risk is likely). A retrospective analysis on the environmental conditions in Doha 2019 may suggest that adjustment is needed, for some of the 30 risk factors involved in the risk assessment clause of the manual.
In order to compete in a world championship marathon, elite female marathon runners from across the globe are required to pre-qualify and maintain a consistent record of high athletic performance in the period prior to the event. The 2019 race is analyzed here due to the high number of athletes who did not finish (DNF) due to the extreme environmental conditions. The official IAAF time results, issued on September 28th, 2019 by Seiko (World Athletics championships, September 2019) recalls a temperature of 32º Celsius and 74% relative humidity at the beginning of the race. Start time was unprecedented by itself, set for 11:59pm at night in an effort to race at slightly cooler temperatures. The number of runners who did not finish (DNF) was untypically high at 30, comparing to the 40 who managed to cross the finish line. At almost equal divide between finished and DNF athletes, the significance of preparing an athlete to race in extreme conditions becomes apparent.
Acclimating an athlete may be achieved in two concurrent settings. Acclimatization is training in laboratory settings, done in closed chambers whereas acclimation is a “repeated exposure to stressful environment” (Powers & Howley, 2019), i.e. field setting. To follow the principal of specificity in training, acclimation done outdoors resembles the environment of race day and is commonly used in athletic preparations. The end product would be a higher tolerance to heat loads and enhanced performance under hot conditions, as time to exhaustion will increase.
The physiological factors improved by heat acclimation (HA) are various and include:
Lower heart rate at work: a combined end product of increases in cardiac output, athlete’s Vo2max and functional power output. Lactate accumulations and lactate turning point are also elevated post-acclimation.
Better thermoregulation (lower core temperatures): HA improves thermoregulation through affrenet feedback sent to the brain control centers, which in turn lower core temperature and regulate blood flow to the periphery (skin surface). Exercise in the heat increases the body water mass, which contributes to thermoregulation as well (Périard, 2015).
Increased plasma volume: once achieved after acclimation, it counters balance the drop in stroke volume, which tends to reduce under heat conditions when plasma concertations are low.
Earlier onset of sweating and increased rate: evaporation is a main source of cooling will enact as an efficient cooling mechanism, increased up to three times its earlier capacity.
Reduced salt loss in sweat: antidiuretic hormones will inhibit loss of electrolytes such as Sodium and Chloride in sweat evaporation, promoting skeletal muscle’s metabolism.
Reduced blood flow to skin: to enable more oxygenated blood to muscles, to allow for contractions.
Metabolism of heat shock proteins: after exposure to heat, stress proteins are synthesizes to protect cells from heat-induced damage.
Elements in training
From the broader perspective of coaching, the time of year and location of the selected target race are considered. Based upon the retrospective review of the Doha marathon, athletic preparation (coaching) should begin with the macro cycle focusing on developing aerobic capabilities, about 6 months prior to the event. The aerobic focus stems from two main factors; First, extreme heat is detrimental to aerobic-based cellular processes such as aerobic glycolysis, so training to improve aerobic might offset the predicted damage. Second, the marathon trained for is a long-term event relying almost solely on aerobic energy production and required a strong aerobic base (Powers & Howley, 2019).
The athlete in this hypothetical discussion is a well-trained healthy female, 35 years of age and injury free at the onset of the training plan. Her Vo2max is currently 45 ml/kg/min and her nutrition incorporates carbohydrates, fat and proteins. Current weekly mileage is 50 miles.
The building blocks of the athletic preparation are all represented during the 24 weeks training plan. The microcycle is 4 weeks span and the mesocycle is 7 days in length. The following elements relate to the 7-days mesoccyle. Note that all elements are greatly affected by heat and therefore should be centered during the athletic preparation.
Intensity: 1x / cycle, speed work is prescribed. This is a moderate to intermediate length event and is approximately 80% aerobic. Example: mile repeats at 85% Vo2max. Intensity levels above 40% of Vo2max are necessary to trigger HA (Powers & Howley, 2019).
Duration: marathon training required long term training bouts. Run sessions over 90 minutes and up to three hours are prescribed 1x/ cycle, in a linear and gradual increase over the microcycles.
Frequency of heat exposures: the athlete is exposed to heat and relative humidity for a minimum of 5x/ cycle run sessions during the base-building phase. This may increase to double session a day once base has been achieved and at least three weeks prior to tapering phase. Interval running sessions can be used with time for recovery measured as an index to HA. As HA can be reached between 7-14 days, initial base build is the most advantageous time to place it in.
Environmental conditions: if possible, relocating the athlete to a climate similar to race environment. Athletes who reside in colder, dry environments might have to employ laboratory settings to increase ambient heat and humidity, or use rubber suits for shorter runs. Pre-planning of the athletic preparation will lay out the optimal time for the athlete to build base, develop and peak. In the northeast, the months of July and August are hot and humid and may be an ideal training environment for HA.
Laboratory and field training: laboratory or “physiologically compensable environment” (Smoljanić et al., 2014) allow for deliberate, controlled hyperthermia. This cautious HA can fine-tune aerobic improvement and be used for detection and monitoring of physiological factors such as Vo2max, cardiac output, ventilatory rate and more. Field training, which can be utilized concurrently with lab sessions, is an independent training environment which poses uncontrolled heat exposures for the athlete. Field training will however prepare the athlete better as it is more specific to the race environment the athlete is to compete in. Additionally, it was found that running economy, and not necessarily developed aerobic abilities, improved HA when running in closed chambers (on a treadmill) (Smoljanić et al., 2014). This further emphazises the significane of field training, if aerobic fitness is key in the training plan.
Strategies for fatigue management
Exercise in the heat impairs performance and shortens the time to fatigue, especially in long term events such as the marathon. As HA increases in the 7-14 days period, it continues to be supported by the training plan, preparing the athlete to compete in the extreme environments.
Other than HA, which is the major component to handle fatigue in extreme conditions and was discussed earlier, several other strategies to manage fatigue are advised. First, hydration is critical due to the hot ambient conditions the athlete is training in. it is necessary to pre-hydrate and continue throughout the exercise bout and after. To replenish sodium and chloride lost due to high evaporation rate, the athlete’s body weight will be measured prior and post training, to determine the amount of fluid required for replenishment (Powers & Howley, 2019). Second, nutrition should have an adequate amount of carbohydrates (CHO) to provide oxygenated energy required for the higher intensities (over 60% of Vo2max) in which marathon training is performed. Third, increasing the Vo2max itself during the training plan will decrease the relative intensity in which the athlete compete in on race day, increasing the time to fatigue. Behavioral strategies such as increased motivation can arouse the central nervous , as more motor units are recruited and fatigue is delayed due to ongoing cross-bridge activity (Powers & Howley, 2019). Attentive coaching can be significant at this point of the athletic preparation.
The Doha women’s championship marathon had a high rate of DNF athlete. The environmental conditions were extremely hot and humid. While the organizers adjusted the race conditions by starting the race at 11:50pm and providing water-soaked sponges, additional water station and nutrition for the athletes, almost 50% of them DNF and some had suffered heat injuries. It is important for the coach to research their athletes’ goal race in the environmental perspective. Proper HA as a component in the training plan can establish optimal physiological adaptation and significantly assist in racing under extreme conditions such as the Doha race had. Nonetheless, athletes should be viewed individually and might not all respond to HA in an efficient and timely manner, having to be evaluated just prior to race to safely DNS (“Did not start”), if their condition poses a higher risk for injuries.
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Smoljanić, J., Morris, N. B., Dervis, S., & Jay, O. (2014). Running economy, not aerobic fitness, independently alters thermoregulatory responses during treadmill running. Journal of Applied Physiology, 117(12), 1451-1459.
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