Department of Exercise Science Assistant Professor Kylie Harmon (right) and exercise science student Rylie DiMaio review a sonogram of DiMaio’s leg muscles to provide a baseline for Harmon’s research on preserving muscle strength during immobilization.
Mind over matter.
Kylie Harmon, an assistant professor in the Department of Exercise Science in the Falk College of Sport and Human Dynamics, has always been fascinated by this deep-rooted idea that a person could control a physical condition with their mind.
More specifically, she wondered if a person could use their mind to preserve muscle mass and strength during a prolonged period of immobilization. For Harmon, turning this idea into actual research was sparked by a published study where researchers used neuromuscular electrical stimulation on muscles immobilized in a cast to preserve leg strength and mass. Surprisingly, mass was preserved, but strength was not.
Harmon’s research found that given the role of the nervous system in immobilization-induced weakness, targeted interventions may be able to preserve muscle strength but not mass, and vice versa. Though preliminary, her findings highlight the specific nature of clinical interventions and suggest that muscle strength can be independently targeted during rehabilitation.
Harmon’s innovative research, which was conducted over several months and with nearly 40 participants, was published this past spring by the peer-reviewed scientific journal Experimental Physiology.
We sat down with Harmon to learn more about her research, most surprising findings, and next steps. Here’s that discussion:
Kylie Harmon
Q: What did you learn from the previous research on this topic, and how did that frame what you wanted to accomplish with your research?
A: Those researchers saw that daily muscle stimulation helped to maintain muscle size, but didn’t impact muscle strength. In much of my work, I was using interventions that improved muscle strength but had no impact on muscle size. I had some experience with action observation and mental imagery, which are neural intervention techniques in which a person observes muscular contractions or thinks about performing muscular contractions without actually doing so. These have been shown to be effective for strength gain or preservation, as they activate the neuromuscular pathways responsible for strength production. However, they don’t impact muscle size.
So, I thought it would be interesting to directly compare these two interventions–neuromuscular electrical stimulation versus action observation + mental imagery–to see if previous findings held up. We decided to design a lower-limb immobilization study with one group performing daily action observation + mental imagery to preserve strength, and another group performing daily electrical stimulation to preserve muscle size. The goals were twofold: 1) To further demonstrate that strength and size are distinct qualities and need to be addressed with specific interventions and 2) To hopefully improve rehabilitation outcomes by preserving size and strength during immobilization.
Q: Once you established your goals, how did you determine your research methods?
A: It took several months and a lot of teamwork to determine our methods. I relied heavily on existing literature to determine how to best implement lower-limb immobilization, what leg braces to use, what joint angle to immobilize at, and how long immobilization was needed before we would observe decreases in strength and size. I reached out to authors of my favorite papers to ask them about their methodologies, such as how to design an appropriate action observation + mental imagery intervention and what stimulation devices to buy.
Once I had a good idea of the game plan, I presented the idea to my mentors and collaborators to get their feedback. Finally, we developed a sizable research team to help with the project: three Ph.D. students, three M.S. students, four physical therapy students, and five undergraduate students. It was very much a team effort!
As demonstrated by exercise science student Lydia Van Boxtel, the subjects in Kylie Harmon’s study need to learn how to use crutches after being fitted with the leg brace.
Q: Can you describe the process of gathering your data?
A: We screened 117 interested people, and when all was said and done, we had 39 individuals fully participate in the study. Prior to the immobilization week, we tested muscle strength, muscle size and the ability of their brain to activate their muscles. We then had physical therapy students fit participants with a leg brace and crutches and show them how to navigate a variety of obstacles–opening doors, using stairs, sitting and standing.
During their week on crutches, participants had to wear accelerometers around both ankles so we could ensure that they were actually using the brace and crutches when away from the lab. We gave them a shower chair to assist in bathing, as they had to keep the brace on at all times except during sleep. We asked them to track the food that they ate. We also had a member of the research team call and check in on each participant every day during the immobilization week to make sure they were complying with study protocols and weren’t running into any issues.
In addition to immobilization, one group performed daily action observation + mental imagery using a guided video and audio recording, and another group performed daily neuromuscular electrical stimulation on their thigh muscles with a stimulation device we gave them.
We had participants return to the lab for a post-testing visit and again re-tested their muscle strength, size and neuromuscular function. If they lost strength (which almost everyone did), we had them come back to the lab twice a week for lower body resistance training until they regained their strength. We didn’t want them to leave the lab with weak, small muscles because of our experiment. Not very ethical. We ensured they were recovered and published that data as well. Amazingly, no one dropped out during the leg immobilization, and we had 100% compliance.
To read the full Q&A with Harmon, visit the Falk College website.
