University of Puget Sound Students Take a Plunge for Science

Students

Chris Nicol ’24 researches the effect of cold water on the mammalian dive reflex

Chris Nicol ’24 was freediving for lobsters off the coast of San Diego, Calif., when he realized that the cold water was impacting how long he could hold his breath. As an exercise science major with a minor in neuroscience and an emphasis in bioethics at University of Puget Sound, he was intrigued and wanted to know what was causing it. He wanted to know if water temperature was a factor in the strength of the mammalian dive reflex, so he decided to find out.

“When your skin comes in contact with water, it sends a signal to your brain stem, which then sends a signal to the rest of your body to lower your heart rate, lower your cardiac output, and increase your blood pressure,” Nicol says. “That brings more oxygenated blood from your periphery to your core to conserve oxygen so you can survive longer underwater. It's most prominently seen in sea mammals like whales, dolphins, and seals, but all mammals have this reflex.”

Working with his faculty advisor, Assistant Professor of Exercise Science Kirsten Coffman, to design a study as part of Puget Sound’s summer research program. Using the exercise science lab in Weyerhaeuser Hall, Nicol first takes each subject’s vitals to get a baseline for their health, including a breath-holding test and a lung function test. Then, participants step into a large tub of water, which is heated to either a pleasant 98 degrees or a brisk 65 degrees Fahrenheit. While in the tub, the subjects are hooked up to several sensors and a mouthpiece so Nicol can monitor their oxygen and carbon dioxide levels, respiratory rate, heart rate, and core temperature. Finally, Nicol has his subjects hold their breath again. Over the course of three visits, Nicol can see in the data how each subject reacted to the different water temperatures.

“What we're seeing is that cold water elicits a much stronger dive reflex, and so the heart rate goes up, because they're like, ‘Wow, it's cold,’ and then they start holding their breath. Almost right away, their heart rate drops by almost 20 beats per minute as their body works to conserve oxygen. It's a much sharper drop in the cold water compared to the warm water, which is really interesting,” Nicol says.

Chris Nicol ’24 uses the exercise science lab at University of Puget Sound to explore how cold water impacts the mammalian dive reflex in his subjects.

A native of California, Nicol first visited Puget Sound when visiting his brother, Ethan Nicol ’22, for weekend ski trips in the Cascade Mountains. He fell in love with the campus and decided to enroll. His experience breaking his hip twice while playing soccer and suffering multiple concussions as an athlete and outdoors enthusiast cemented his desire to study the human body.

“Being close to the mountains was important to me when choosing a school, but I was surprised by how many opportunities there were for undergraduate research. I know that my professors want to see me succeed and that with my degree, I’ll be able to go into the medical field and start a career.”