J.P. Hyatt: Looking at Athletics Through the Prism of Physiology
.jpg "J.P. Hyatt, PhD, offers advice to his students in the lab")
While other Winter Olympics TV viewers will be mesmerized by the number of triple axles a skater performs or how far a ski jumper can fly through the air, J. P. Hyatt, PhD, expects to be absorbed by slow and fast twitches.
That’s not some new entry into the Olympics, but the makeup of skeletal muscles that will be on display.
All muscles involved in movement are a combination of fibers that are either slow or fast twitch, depending on whether the athlete is a sprinter, for example, or a long distance runner. But there are the rare exceptions that make Olympic history: Hyatt still can’t get over the 1980 Olympic performance of American Eric Heiden, who won all the men’s speed skating races - five gold medals. “He won in all distances, sprint to endurance, and from a muscle perspective, that is theoretically impossible.”
Hyatt knows something about muscles. With an undergraduate degree from Occidental College, a masters degree from the University of Massachusetts, Amherst in exercise science/kinesiology and a PhD in Molecular, Cellular, and Integrative Physiology from UCLA, Hyatt’s expertise is, in part, in the physiology of skeletal muscle and how it adapts to exercise. He and his laboratory are housed in the Department of Human Science in the School of Nursing & Health Studies at Georgetown University Medical Center.
He studies just how it is that a muscle gains bulk and strength from exercise. Hyatt says that relative to other body cells, muscle cells are huge, and have hundreds, if not thousands, of nuclei (most cells have one). Each nucleus is responsible for a certain volume of muscle fiber, so if the muscle is being exercised and needs to hypertrophy (grow bigger), more nuclei are needed. Hyatt investigates cells, or satellite cells, that reside within muscle that participate in this process. Specifically, biochemical growth factors will turn on genes within the satellite cells that stimulate their division and, ultimately, fusion with the muscle fiber. The addition of new nuclei to the fiber’s existing nuclear population through this process translates to a greater fiber volume and, hence, bigger muscles.
Once inside, nuclei in the muscle fibers then produce more actin and myosin proteins, along with other structural proteins, which allow the muscle to contract more forcefully. The action of these two proteins is what the experts call twitch tension. Parallel responses will occur simultaneously such as augmenting mitochondrial volume, to produce more energy, and a growing of the vascular network within the muscle to match the increasing demands for oxygen.
When exercise ceases and the muscle atrophies due to periods of inactivity, nuclei in the muscle get selectively removed.
Hyatt says that genetics play a big part in whether a person has predominantly fast or slow twitch muscles, although training is obviously important because muscle can adapt to where it is pushed. “Your sport essentially picks you,” he says, noting his past in competitive cycling. “If your muscles contain predominantly fast or slow twitch fibers, then you will be naturally better at sprinting or marathons, respectively.”
Which is why he looks forward to seeing the Olympics. “I look at the athletes from a perspective of both applied and basic physiology. I like to see who is in what position in which sports,” he says. “For example, the breakman in a two-man bob sled has to have strength, power, and speed to help push the sled at the start, while the front man must also have finely coordinated movements to steer the sled.
“There is technique and style, for sure,” Hyatt says. “But I can’t help but be impressed by the muscles at work; they’re really the main “player” in all sports whether you need leg strength for speed skating or finely coordinated movements when shooting a rifle in the biathlon.”
By Renee Twombly, GUMC Communications
