August 17, 2017

Exercise in Heat and Humidity in the Midwest

Author: Diem Gray

By Motion Physical Therapist: Dr. Michelle Steege PT, DPT 

Exercising in the summer can mean putting up with hot and humid weather, especially when you reside in the Midwest. This can impact your success and put you at risk for heat related illness. There are a number of factors that affect exhaustion during exercise in the heat including duration and intensity of exercise, an individual’s acclimation, physical conditioning, hydration status, personal factors (health history, medications, recent illness), supplements, and sleep (Armstrong, Casa and Millard-Stafford). Energy is also depleted faster in hotter conditions (Armstrong, Casa and Millard-Stafford).

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Exertional hyperthermia occurs at an internal temperature of 104° F. This can occur when muscle generated heat accumulates faster than heat dissipated through sweating and skin blood flow (Armstrong, Casa and Millard-Stafford). As internal temperature rises, skin blood flow is in competition with the metabolic demands of active muscle (Gonzalez-Alonso, Crandall and Johnson). Initially muscle blood flow is not impaired, but skin blood flow is affected which increases internal body temperature (Gonzalez-Alonso, Crandall and Johnson). It’s a vicious cycle!

Sweating is an important part of thermoregulation and the primary mechanism of heat dissipation (Thein), but too much sweating can have negative effects on the body. “Excessive sweating also results in salt loss, which has been implicated in exercise associated muscle cramps” (Armstrong, Casa and Millard-Stafford). “If fluids lost through sweating are not replaced, the ensuing dehydration brings into play further problems of cardiovascular control”, leading to decreased muscle and skin perfusion (Gonzalez-Alonso, Crandall and Johnson).

While there are risks associated with exercising in the heat, it can be done with caution! Slow acclimatization is the best option for exercising in heat.  “Acclimatization requires gradually increasing the duration and intensity of exercise during the initial 10-14 days of heat exposure, although maximal protection may take up to 12 weeks” (Armstrong, Casa and Millard-Stafford). Hydration is also very important. In addition to water, electrolytes need to be consumed to offset sweat-sodium loss. Weighing oneself before and after a run or activity can provide information on the amount of sweat loss and help to determine the amount of fluids needed for recovery over the rest of the day or prior to your next training session. 16-20 oz of fluids should be consumed per pound of body weight lost (Bergeron).

About Dr. Michelle Steege, PT, DPT:

Dr. Michelle Steege, PT, DPT

Dr. Michelle Steege, PT, DPT

Michelle is passionate about the profession of physical therapy, which allows her to help people return to the activities they love. Her experience in a hospital-based outpatient orthopedic setting has given her the opportunity to treat a variety of orthopedic conditions and sports injuries. Michelle began her orthopedic residency at Motion in 2017, further advancing her knowledge in the world of physical therapy. She also has training in instrument-assisted soft tissue mobilization (IASTM) and running analysis.

Michelle earned her undergraduate degree from the University of Wisconsin – Eau Claire in exercise science. She then attended the University of Texas Southwestern Medical Center in Dallas where she earned her doctorate in physical therapy.

In her free time, Michelle enjoys being outdoors—running, biking, hiking, kayaking, and spending time at the cabin in northern Wisconsin.

Works Cited

Armstrong, Lawrence E, et al. “Exertional Heat Illness during Training and Competition.” Medicine & Science In Sports & Exercise (2007): 556-572.
Bergeron, Michael. “Heat Stress and Thermal Strain Challenges in Running.” Journal of Sports and Orthopaedic Physical Therapy 44.10 (2014): 831-838.
Gonzalez-Alonso, Jose, Craig G Crandall and John M. Johnson. “The cardiovascular challenge of exercising in the heat.” The Journal of Physiology 586.1 (2008): 45-53.
Thein, Lori A. “Environmental Conditions Affecting the Athlete.” Journal of Sports and Orthopaedic Physical Therapy 21.3 (1995): 158-171.