A 20-minute treadmill walk briefly increases bowel sounds in 21 healthy adults

Bowel sounds are an established, non-invasive indicator of gut motility ^[12]. "Bowel sounds have been used as indirect measurements of gut motility since the early 1900s," the team wrote in the Scientific Reports paper, which was led by physical therapist Kento Katagiri ^[6][1]. The paper also explains where the noise comes from: "The bowel sound is produced by the turbulence caused by gut motility during the movement of liquids and gases through the intestinal tract" ^[7].

The protocol is simple, and its choices are defensible. Recordings were made at least two hours after eating, to minimize the effect of food intake ^[3]. The 3,000 steps in 20 minutes come to about 150 steps a minute ^[13]. Each volunteer's post-walk recording was compared with their own resting baseline ^[14]. That design removes differences between people in how noisy their guts are from the comparison.

The response was brief. All three measures rose for one to two minutes after the walk ^[5]. ScienceAlert's account does not report how large the increases were. The researchers suggest the rise may reflect changes in gut motility, possibly more peristalsis, the wave-like contractions that move food along the digestive tract ^[16].

The readout is imperfect. The stethoscope can also pick up gut sounds that do not reflect motility ^[10]. Posture is a second confound. The researchers also discuss the effect of simply moving from lying down to standing ^[11]. Separating that from the walk would take a comparison session with the same change of position and no walking.

The team offers two ideas for why walking would have this effect. One is autonomic: parasympathetic nervous activity rises directly after exercise and could stimulate motility ^[17]. The other is mechanical. Earlier work found that whole-body vibration relieves constipation, and the up-and-down and side-to-side motion of walking might trigger local reflexes in the gut ^[18]. Both explanations remain speculative, according to ScienceAlert, and the researchers say further studies are needed to test them ^[19].

"Walking can serve as an effective, immediate tool for stimulating bowel function," said senior author Yohei Otaka, a rehabilitation physician ^[15]. The data support "immediate". "Effective" goes beyond them, to people with constipation, whom the study did not include ^[9]. The evidence linking regular exercise to lower constipation risk comes from comparing active and sedentary people ^[8]. In my view this study supplies a plausible first link between the two: a change in the gut within minutes of a walk ^[5].