Muscles flex and tendons tighten as the runner’s body pushes itself up a hill, paces over the pavement, and tilts to the curve of the track. Last year, more than 18 million runners crossed the finish lines in races across the country, but what was going on inside their heads? Researchers from California State University wanted to find out, so they conducted the first experiment to systematically collect the thoughts of runners in the act.

The “think aloud” study, published in the International Journal of Sport and Exercise Psychology, recorded the thoughts of 10 long-distance runners — six men and four women — between the ages of 29 and 52. The participants were chosen because they had a mix of running experience between three to 30 years and were in the middle of training for a half-marathon or longer distance.

First, each runner was asked to practice by running on a treadmill while they voiced their thoughts out loud. Next, they were fitted with recording equipment and directed to run a seven-mile route on the road. Throughout the run, the participants kept an open dialogue with their recorder.

Afterward, researchers had 18 hours' worth of recording, which was transcribed and categorized into three distinct groups: pace and distance, pain and discomfort, and the running environment. Most of their thoughts fell under the pace and distance category, including: “downhill,” “don’t kill yourself,” “just cruise,” “lean and steady,” “make it a long stride,” “2 miles to go,” and “6.50 miles, that’s alright.”

However, 32 percent of all thoughts had to do with the pain and discomfort they were experiencing. Thoughts included: “My hips are a little tight,” “I’m stiff,” “my feet, my ankles, just killing me this morning,” and then a little cruder: “Hill, you’re a bitch,” “God damn it,” “mother eff-er,” “breathe,” “try to relax,” “that sucked, but it’s going to be an awesome run on the way back.”

Lastly, 28 percent of their thoughts had to do with the environment they were running in. Some thoughts included: “I need it to start raining,” “it’s hot,” “it’s really hot,” “oh my gosh, that’s gorgeous,” “it’s so beautiful,” “hope I don’t see any snakes,” “this is such a fu**ing busy street. I hate it.”

If you’re a runner, you may have experienced some of these thoughts yourself. Long-distance runners can spend hours at a time out on a route or track. Some of life’s most difficult dilemmas and deep thoughts can unravel within the long stretches of alone time. Researchers believe the study participants didn’t reveal their personal thoughts because they may have been censoring themselves knowing they were wearing a recorder.

Source: Samson A, Simpson D, Kamphoff C, and Langlier A. Think aloud: An examination of distance runners’ thought processes. International Journal of Sport and Exercise Psychology. 2015.