Jul 31, 2017
Battling Back
Dr. Brendon McDermott

Return to play following an episode of exertional heat stroke should not be taken lightly. There are both physical and mental issues to address.

This article first appeared in the July/August 2017 issue of Training & Conditioning.

Consider a scenario in which you recognize an athlete is suffering exertional heat stroke (EHS). The individual has a core temperature above 104.5°F (41°C) and is experiencing central nervous system dysfunction. Immediately, you enact your emergency action plan for EHS and begin whole-body cold-water immersion. Your rapid response is effective, and the player is expected to make a full recovery. Congratulations, you just saved a life!

But your job is not done yet. After receiving treatment for EHS, it’s only a matter of time before the athlete starts asking a question that all athletic trainers are familiar with: “When can I play again?”

Unlike with a sprain, strain, or fracture, the return-to-play guidelines following EHS are not as clear cut. Incredible advances have been made in EHS prevention and treatment efforts, but the literature lags behind in terms of evidence-based recommendations for return to play after an EHS episode.

That doesn’t mean athletic trainers have to approach it blindly, though. Enough information exists to provide a sample protocol for getting athletes back to their sport after EHS-a protocol I’ve recommended to many clinicians with great success. Although it requires diligence and acute attention to how the athlete is feeling once they resume exercise, it can help ensure a safe return to activity.


When planning return to play after EHS, there are both short- and long-term medical management elements to consider. Initial recovery immediately following whole-body cooling depends on how long the athlete’s core body temperature remained above a critical threshold (104.5 to 105°F or 40.3 to 40.6°C). This length of time typically determines the extent of any cellular, organ, and system damage. Therefore, primary medical management involves eradicating any resultant conditions, such as acute kidney injury, liver failure, cardiac arrhythmia, etc. Many of these ailments call for advanced life support or monitoring, so medical transport via EMS is often required.

Once sequelae are ruled out and the athlete has medically recovered from any lingering effects of EHS, it is important to verify homeostasis. The athletic trainer should promote compliance by having the patient check in with them daily and documenting normal diet, sleep, psychological stress, social interaction, hydration, perceived confidence in return to sport, and bowel habits. To assist in information gathering, athletic trainers could also involve the patient’s coaching staff, parents (especially in high school), teachers, and friends.

This process ensures an athlete is both physically and psychologically ready to resume activity following EHS. If these habits do not return to normal after medical recovery, the patient will likely have a lack of confidence-and, therefore, increased stress or anxiety-about getting back to their sport. As with any injury or illness, keeping the patient informed throughout recovery can facilitate confidence and positive patient-centered outcomes.

The final steps for the athlete before incorporating exercise into their recovery are receiving normal labs, gaining physician clearance, and becoming educated about their predispositions for EHS. When you are able to identify contributing factors for the athlete’s original EHS, you can prevent future episodes. Common predispositions include intense exercise, illness, sleep loss, psychological stress, lack of heat acclimatization, dehydration, environmental stress, wearing protective exercise equipment, and some medications.

Verification of an athlete’s predispositions usually involves an in-depth discussion with them about the days leading up to the EHS incident. If the athlete is unable to recall details from this time period, a coach or parent may remember any unusual behavior relating to food intake, sleep, stress, etc.


Although athletes will likely want to jump right back into exercise after short-term medical management has been addressed, that’s not the recommended course of action. Instead, consensus documents from the NATA and American College of Sports Medicine suggest starting the second phase of treatment with a seven-day rest period. This allows homeostasis to continue for at least a week, ensuring full recovery prior to introducing thermoregulatory stress.

After this rest week, athletic trainers must address heat deacclimatization. We’re all familiar with heat acclimatization-the process in which the body adjusts when exposed to heat, intense exercise, protective equipment, and associated stress. While heat acclimatization takes 10 to 14 days for full physiological adaptation to occur, less is known about how long these adaptations last after the athlete deacclimatizes to heat.

Think of it like cardiovascular fitness. If an athlete who is in great shape suddenly spends 10 days without activity, they will be at a disadvantage upon return compared to their teammates who have been training consistently. The longer the athlete takes to come back, the more cardiovascular fitness will suffer. The same goes for heat deacclimatization-quickly resuming activity in the heat following EHS would be dangerous and would place the athlete at an extreme disadvantage in comparison to the rest of their team. Therefore, a gradual progression back to exercise is encouraged to help the athlete rebuild cardiovascular fitness and reacclimate to the heat over time.

Unfortunately, there is not one specific, evidence-based return-to-activity protocol after EHS. However, some initial case reports have demonstrated success. Keep in mind that any exercise plan at this stage should be discussed with the supervising physician prior to initiation.

One sample return-to-play protocol begins with light activity (less than 60 percent intensity) and heat exposure for no more than 30 minutes a day. By day five, the athlete can progress to moderate activity (less than 75 percent intensity) for up to 90 minutes in the heat. The full protocol includes 14 days of gradual increases in exercise intensity and duration.

Protective equipment onset would occur during this time, as well. As an example, a football player could start with just a helmet one day, add shoulder pads the next, and don full equipment a few days later. If no protective equipment is required, the suggested protocol lasts 12 days.

Throughout the return-to-play process, it is important to monitor the athlete and document all responses to assure safety. There are several ways to do this, the most basic of which involves heart rate assessment via a cardiotachometer or wearable technology. These devices help verify prescribed exercise intensity and track normal responses.

Intensity of exercise can be deducted using heart rate monitoring for percent of heart rate maximum. For instance, to find 60 percent intensity for a 20-year-old athlete, use this formula: (220-age) x percentage. So (220-20) x .60 = 120 beats per minute. Therefore, the athlete would stay under 120 beats per minute in a workout to meet the prescribed 60 percent intensity.

Another form of physiological monitoring that can help facilitate safe progression involves ingestible thermistors. These are pills taken five to six hours prior to activity (to assure transit beyond the stomach) that transmit a readout of intestinal temperature during exercise. Although they can be pricey-$40 to $50 per thermistor-they are reliable for monitoring core body temperature. To save on costs, clinicians can often find discounted thermistors or get signal receivers on loan by reaching out to a manufacturing company directly.

A third way to monitor and guide progression in addition to the two mentioned previously involves tracking exercise intensity from the athlete using a simple rate of perceived exertion scale. This is an important patient-centered aspect of recovery, as it considers the athletes’ feelings and confidence in returning to play.

Beyond these monitoring strategies, appropriate documentation should also be completed throughout the return-to-activity process. Athletic trainers should record as much physiological and perceptual information about the athlete as possible each day, including date, diet and hydration prior to exercise, WetBulb Globe Temperature conditions, prescribed exercise protocol, heart rate, intestinal temperature, muscle pain, rating of perceived exertion, fatigue, and any other signs or symptoms of EHS noted during exercise. This information can be used as a reference point in future EHS cases, protection against litigation, and effective communication with other medical professionals regarding return to play following EHS.

Adjustments to the exercise progression should be made according to the athlete’s recorded physiological and perceptual responses. So if they feel extra fatigue following a workout, their subsequent training session should be very light. Contrarily, if they feel energized, they could probably be accelerated in the plan.

If the athlete experiences an abnormal response or symptom onset at any point during phase two, they should take at least a full day of rest. Adjustments should then be made to the return-to-play protocol, which could include limiting exercise intensity, duration of workouts, and heat exposure, as well as expanding time between training sessions. In addition, the supervising sports medicine staff should consult with the patient’s physician for guidance and further evaluation, if necessary.


If an athlete goes through the return-to-play protocol without issue, they may be prepared to get back to activity with full heat exposure and intense exercise. But it does not hurt to do a final check. One way to determine readiness is to complete heat tolerance testing prior to full return.

The standard heat tolerance test includes the athlete walking at two miles per hour with a two percent grade in heat (104°F or 40°C with 40 percent relative humidity) for two hours while wearing shorts and a T-shirt. The athlete is deemed heat tolerant if they do not surpass a heart rate of 185 beats per minute and a rectal temperature of 101.3°F (38.5°C) during the test (rectal thermistors are commonly used throughout research protocols).

Although military settings have had good luck with this method of heat tolerance testing, its use is controversial in the literature. Some of its detractors say it is impractical because it must be conducted in an environmental chamber and does not replicate the repeated, intense exercise athletes often face. Others contend that the test simply verifies heat acclimatization, while not truly testing how the thermoregulatory system is used during heavy exercise.

Despite these critiques, the standard heat tolerance test is one of the only tools we have to determine full readiness for return to play following EHS. Athletic trainers who are interested in replicating this test in the field can do so by putting an athlete through the same walking criteria on a treadmill. Then, repeat the test with more clothing and an increasing exercise intensity at a rate sufficient to ensure at least three days with full equipment prior to return to play. Clinicians must be sure to monitor the athlete’s temperature and heart rate throughout, implementing the same thresholds of 185 beats per minute heart rate and 101.3°F (38.5°C) rectal temperature.

If the athlete cannot pass a heat tolerance test, they may be deemed heat intolerant. True heat intolerance may result from a myriad of factors, including genetic variants, previous illness, or neurologic abnormalities. In these cases, an expert should evaluate and assess the athlete to verify heat intolerance and determine a safe physical activity plan going forward.

When an athlete finally resumes activity following EHS, they should continue to be on the athletic trainer’s watch list. Further, if a specific cause of the original EHS has been identified, it should be checked regularly.

Although limited evidence exists in support of a consensus return-to-play protocol for athletes after EHS, the recommendations presented here have been successful anecdotally. Ensuring medical recovery from the initial episode, verifying homeostasis, and adhering to a gradual progression to exercise will give the athlete the best possible chance to get back to activity. With more application of this specific medical practice, we hope additional guidance will be possible in the near future.

To view the references for this article, go to: Training-Conditioning.com/References.


There have been anecdotal incidents where return to play has occurred with military, athletic, and recreational patients following exertional heat stroke (EHS). Here, I describe two of them:

An upcoming case report in the Journal of Athletic Training demonstrates the effectiveness of a gradual return to play after EHS in a 17-year-old high school football player. His sports medicine team abided by the recommendations outlined in the main article throughout recovery. Although this particular patient experienced some setbacks in his exercise progression, his athletic trainers applied basic alterations to the plan and held back where appropriate. Eventually, the athlete made a full return in 60 days.

In another case, published in a 2013 edition of Current Sports Medicine Reports, there was a triathlete who experienced an EHS episode while competing. Afterward, he did not complete a progressive return-to-play protocol. Instead, he rested for a limited time and continued training for his next event.

At his subsequent competition, this triathlete experienced another EHS incident. This time, he sought expert advice on recovery. A team of individuals helped him begin a gradual return to training that considered exercise intensity and heat acclimatization. After completing his protocol, he was able to successfully compete in future events with more knowledge of how to prevent EHS.

Brendon McDermott, PhD, ATC, is an Associate Professor in the Athletic Training Program at the University of Arkansas. He also serves on the Medical and Science Advisory Board of the Korey Stringer Institute. Dr. McDermott can be reached at: [email protected].

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