Tahsin Khataei, a graduate researcher in the lab of Christopher Benson, MD, says that although the mental and physical health benefits of routine exercise is widely known, many do not participate in regular exercise regimens.

“One reason for this is that exercise, especially high-intensity exercise, is often accompanied by muscle pain and fatigue—felt to be brought on by the acidic buildup of lactate and protons,” Khataei said.

Khataei is first author on a recent study published in the American Physiology Society’s Journal of Applied Physiology (JAP), which suggests acid-sensing ion channels (ASICs) within sensory neurons detect the chemical changes in muscles during high-intensity interval training (HIIT). HIIT is characterized by short bursts of anaerobic  exercise followed by lighter periods of recovery. Khataei measured the pinching force applied to the gastrocnemius muscle before a mouse model would withdraw its leg. He compared wild mice models to mice models that lacked the ASIC3 gene, a subunit of the ASICs family.

“Whereas wild-type mice showed increased muscle pain (hyperalgesia) immediately after exhaustive exercise, mice that lacked the ASIC3 gene experiences no such hyperalgesia,” Khataei said. “In addition, we found that HIIT lowered the level of ASICs in the muscle sensory neurons, and this correlated with decreased pain perception after exercise.”

Mice with decreased ASICs also improved exercise performance, which suggests the diminishment of ASICs can lower pain perception during high intensity exercise.

Previously, Khataei published a study in Medicine & Science in Sports & Exercise, and found HIIT decreased ASICs and improved exercise performance. This work led to a travel award, allowing Khatei to present these findings at the American College of Sports Medicine (ACSM) meeting in the fall of 2018. This funding also allowed Khataei to further his research, to discover the novel mechanistic insight into exercise-induced muscle pain, and publish the recent study in JAP. Khataei will complete his PhD at the University of Iowa in the fall of 2022.

“In particular, our results may have important implications for some clinical conditions, such as chronic fatigue and fibromyalgia, in which exercise-mediated pain can deter even the simplest activities of daily living,” Khataei said.