Female endurance runners – what should you be considering?

Carrie is a 35-year-old busy mother of three.  In addition to her part time job as a dental hygienist, she is usually busy shuffling her elementary age kiddos to and from school, play dates, and sports. Despite her hectic schedule, she makes a conscious effort to eat healthy, drink plenty of water and exercise. In fact, Carrie has been an avid long-distance runner over the past 5 years and generally runs 10-15 miles at least 4 days per week. 

Over the past 6 months, Carrie has noticed that she is feeling more fatigued throughout the day, especially when running. She isn’t able to maintain the same speed and distance as she had in the past and her menstrual cycle has been significantly more spaced out and sporadic.

Carrie is exhibiting some tell-tale signs of low energy availability and menstrual dysfunction, which female endurance runners are predisposed to. She may also be at risk for reduced bone density or osteoporosis, which occurs when there is thinning or weakening of the bones. Low energy availability, menstrual dysfunction, and low bone mineral density is often referred to as the female athlete triad (FAT).¹

For female endurance runners, it is vital that they have an appropriate caloric intake. That means the amount of calories consumed should not be lower than the amount of calories used with exercise and other daily activities. The average non-pregnant female between 20-75 years old typically requires 1,800-2,400 calories per day depending on her level of activity.² The U.S. Department of Agriculture and U.S. Department of Health and Human Services has a table outlining the adequate caloric intake in the Dietary Guidelines for Americans. The link can be found in the references, and I would highly recommend comparing to where you are falling with your nutrition intake.

Inadequate caloric intake can have other consequences beside the usual fatigue. These include negatively impacting metabolism, creation of protein within the body (important for building muscle), immune system health, and cardiovascular health. Reduced nutrition can also result in decreased production of vital hormones, including estrogen and progesterone. A reduction in these hormones can further contribute to menstrual dysfunction and decreased bone health. Estrogen is vital to maintain the strength of bones and reduce risk of fracture. Unfortunately, women are often prescribed contraception for irregular menstrual cycles; however, “research has shown that contraceptives mask the real issue” of low energy availability.¹ 

Inadequate caloric intake can also increase risk for musculoskeletal injury. In fact, a study performed on ninety healthy adult females who ran a minimum of 20 miles per week and ranged in age from 18-53 years old found that those injured consumed significantly less fat and an overall lower percentage of total calories from fat as compared to non-injured runners. The injured women also consumed lower levels of fat-soluble vitamins A and K. It was found that daily fat intake was the “single best dietary predictor of injury”.³

Overall, if you are an endurance runner, please keep in mind that you need to take care of your body. Emphasizing ample caloric intake and an overall balanced breakdown of nutrition, including fat, protein, and carbohydrates, is going to be very important to keep you healthy and running for many more miles!

If you are noticing increased fatigue, abnormal menstrual cycles, or an increase in injuries, there are qualified healthcare professionals that can help ensure your overall health. If you are experiencing increased fatigue and/or an abnormal menstrual cycle, consult your physician. Don’t just settle for the birth control option! Also, be sure to address your nutrition needs either with a registered dietician or nutritionist who specializes in running and not just good ole weight loss solutions. If you are experiencing a running related injury, please seek out a physical therapist to reduce pain, improve your running ability, and reduce risk of re-injury. 

Written by Jordan Schmidt, PT, DPT

Reference List:

1. Rothschild, C., & Schellhase, K. (2020). Considerations for the Adult Female Endurance Runner: A Survey Analysis. Journal of Women's Health Physical Therapy, 44(1), 3-8.
2. S. Department of Agriculture and U.S. Department of Health and Human Services. Dietary Guidelines for Americans, 2020-2025. 9th Edition. December 2020. Available at DietaryGuidelines.gov.
3. Gerlach, K. E., Burton, H. W., Dorn, J. M., Leddy, J. J., & Horvath, P. J. (2008). Fat intake and injury in female runners. Journal of the International Society of Sports Nutrition, 5, 1. https://doi.org/10.1186/1550-2783-5-1