New research has found that a 30-minute bout of exercise reduces a defensive physiological response known as the startle reflex. The study, published in the journal Depression & Anxiety, suggests that exercise can help reduce anxiety.

“We were interested in this topic because we would like to develop anxiolytic treatments. Exercise seemed a promising intervention to decrease anxiety,” said study author Tiffany R. Lago (@tlagomd), a psychiatry research fellow at the National Institute of Mental Health.

Though previous research has found that exercise can reduce anxiety, those studies relied on subjective self-reported surveys. So the researchers turned to an objective measure of fear and anxiety known as the Neutral-Predictable-Unpredictable threat test.

The participants received uncomfortable but not painful electrical shocks on their left forearm. The shocks were sometimes administered at predictable intervals but other times were administered unpredictably. During the test, the researchers used recording electrodes to measure participants’ eyeblink startle response.

The study of 34 adults found that spending 30 minutes on an exercise bike reduced the startle reflex during periods of unpredictable threat.

The findings suggest that “for all people, regardless of fitness level/sex/age, even one bout of exercise can affect how the brain handles unpredictable threat/ anxiety,” Lago told PsyPost. “Exercise seems to be a safe, inexpensive intervention that can decrease anxiety.”

“This study is in healthy volunteers. We will need to address if the effects are the same, or potentially even greater, in anxiety patients,” she noted.

The study, “Exercise decreases defensive responses to unpredictable, but not predictable, threat“, was authored by Tiffany R. Lago, Abigail Hsiung, Brooks P. Leitner, Courtney J. Duckworth, Kong Y. Chen, Monique Ernst, and Christian Grillon.