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September 26, 2012 • Sports Medicine & Nutrition

Follow heat-acclimatization guidelines

Pushing athletes too hard in preseason practices is a recipe for disaster

By Brendon P. McDermott, PhD, ATC, University of Tennessee at Chattanooga

If there was a pill that offered your athletes protection against heat illness, and increased their performance at the same time, would administrators and coaches want it? Further, what if it were free?

Photo: Joe Mabel

A solution is available that does not involve a pill at all. Heat acclimatization offers both of these benefits among others, but many fail to take advantage of its benefits.

Establishing favorable heat acclimatization

Extreme heat increases the risk our athletes face in dealing with exertional heat illness. For example, there have been game-time temperatures for a multitude of MLB games in the triple digits. Further, Stephen Strasburg, a pitcher for the Washington Nationals, suffered heat exhaustion and had to leave a 2012 start after only three innings. Fortunately, some high schools are better prepared than ever for these extremes. Seven states use favorable heat acclimatization guidelines for football workouts. These guidelines provide the athlete with the most profound natural defense against heat illness.

Many states initiated these changes in reaction to the high school deaths from the previous two years. In 2011, there were eight high school athlete deaths in one week that were related, at least in part, to the heat. The positive spin on the result is that state high school athletic associations voted to adopt heat acclimatization guidelines, which were recommended and published in 2009 (see below). Also impressive is that some of the initial states to adopt these guidelines have a reputation of a “football is life” mentality (Texas and Georgia). This serves as an example of high-level athletics adjusting for the overall safety and well-being of student-athletes.

It seems as though many sports administrators, however, have ignored implementation of a proactive approach. As of July 1, 2012, only seven states have adopted the guidelines in full. This means high school athletes in 43 states may be unprepared to exercise in the heat during early preseason sessions. Furthermore, colleges and universities typically follow minimum standards set forth by the NCAA, which only apply to football. So, the vast majority of college athletes unlikely are to be prepared to tolerate high-demand activities in extreme heat.

Understanding acclimatization

Heat acclimatization is the body’s physiological response to gradually increasing demands. It’s possibly the most impressive adaptation the body is capable of mastering. Heat acclimatization involves increased plasma volume, increased stroke volume, increased sweat rate, lower core body temperature, and decreased heart rate. All of these positive responses improve athletic performance at the same time as contributing to a natural defense against heat illness.

Acclimatization is accomplished through the gradual introduction to environmental heat stress, along with increasing the duration and intensity of activity, and the amount of protective equipment worn during activity. A comprehensive acclimatization plan for preseason workouts should be similar. There needs to be a gradual increase in the duration and intensity of workouts for any outdoor sport when heat exposure exists. For example, do not include three sessions of three-hour practices in full pads on the first day of practice. Design initial workouts to ensure all athletes on a team achieve an adequate level of protection. Do not assume summer or off-season voluntary workouts are providing an adequate level of acclimatization. Heat acclimatization guidelines must be required for all athletes in all sports to minimize the potential for a catastrophic event.

Benefits extend beyond heat

Heat acclimatization is merely one aspect of heat illness prevention. Other factors that contribute to the onset of heat illness include dehydration, poor physical fitness, high body mass index, psychological stress, sleep loss and a warrior mentality. Many of these factors may present a short-term effect, which is limited to a particular exercise session or day. The great thing about heat acclimatization is it is intrinsic to the athlete and is guaranteed to improve performance and protect against heat illness. Cardiovascular benefits associated with heat acclimatization also helps to minimize the risk for a cardiac episode. Overall, minor alterations in the progression of team activities in hot environments protect athletes and improve performance.

Regardless of the cause of our weather extremes thus far in 2012, coaches and administrators must respond properly to weather forecasts of impending heat as preseason practice sessions begin. Heat acclimatization provides physiological protections against heat stress, which are accomplished with minimal effort by those who plan activity. This adaptation reduces risk for cardiac stress and heat illness incidence while improving performance.


Preseason heat-acclimatization guidelines

In 2009, the National Athletic Trainers’ Association published its preseason heat-acclimatization guidelines (for the 14-day heat-acclimatization period) for secondary schools, which now are being followed by seven states in the country. Here is a brief synopsis of those guidelines (for the entire report go to nata.org).

1. On the first through fifth days of practice, only have athletes participate in one practice per day.

2. Stop practice during inclement weather or heat. Resume when safe. Do not exceed three hours of practice in one day.

3. Have a three-hour recovery period between practice and a maximum one-hour walk-through during the first through fifth days of practice.

4. During the first two days of practice, only use helmets. Add shoulder pads for the third through fifth days. By the sixth day, all protective equipment may be worn and full contact can begin.

5. Double practices are allowed from Day Six to 14 but must be followed by a single practice day the next day.

6. Neither practice during a double-practice day should exceed three hours. Do not exceed five total hours of practice. Have at least a three-hour rest period in a cool environment between sessions.

7. Have an athletic trainer on site before, during and after all practices during the heat-acclimatization period.


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