Strength training protects against development of muscle pain

Date: Thursday, May 5, 2022

Protective effect works through testosterone and, in male mice, also alleviates existing pain 

Strength training protects against the development of muscle pain in mice, according to a new study by researchers with University of Iowa Health Care. 

The UI team, led by Kathleen Sluka, PT, PhD, professor of physical therapy and rehabilitation sciences, found that this form of exercise produces its effect through the male hormone testosterone activating androgen receptors, and the study revealed sex differences in the effect of strength training on muscle pain. Although strength, or resistance, training prevented the development of chronic muscle pain in both male and female mice, it only alleviated existing muscle pain in male mice. 

Chronic pain is a common and costly problem in the U.S. Exercise, including resistance training, is often recommended to patients to help prevent and treat chronic pain, including low-back pain, osteoarthritis, and fibromyalgia. But while the biological mechanisms contributing to the benefits of aerobic exercise have been well studied, much less is known about how resistance training affects muscle pain. 

In the new study, the UI team, including lead author Joseph Lesnak, PT, a graduate student in Sluka’s lab, developed a new mouse model to study the effect of strength training on muscle pain. The researchers had the mice climb a ladder with small weights gently attached to their tails. They showed that this activity increased grip strength in the mice’s front paws indicating that it was an effective form of strength training.  

When mice completed eight weeks of this strength training protocol before the onset of muscle pain, both male and female mice were protected from the development of muscle pain. In contrast, when muscle pain was already established, strength training alleviated pain only in the male mice. The findings were published recently in the journal PAIN

Image of exercise weights

Blocking the effect of testosterone during resistance training eliminated the protection against muscle pain, indicating that this male hormone, which is present in both male and female mice, is required for the effect. However, blocking testosterone after the exercise-induced protection is already established did not remove the protection. 

“Our study shows that resistance training protects against development of chronic pain and does this in both male and female mice through testosterone and androgen receptor activation,” Lesnak says. “This gives a rationale for using resistance training, in addition to other forms of exercise, for both men and women to reduce and treat musculoskeletal pain. It also suggests that future studies could target androgen receptors for development of novel treatments for musculoskeletal pain.” 

In addition to Sluka and Lesnak, the UI team included Alexis Fahrion, Amber Helton, Lynn Rasmussen, Megan Andrew, Stephanie Cunard, Michaela Huey, Austin Kreber, Joseph Landon, Travis Siwiec, Kenan Todd, and Laura Frey-Law. 

The research was funded in part by grants from the National Institutes of Health.