We react differently to different types of beats, even if songs are at the same tempo. – By Scott Douglas

When choosing music to work out to, most people gravitate toward faster tunes. But there’s more to how a song affects exercise than its number of beats per minute, according to a fascinating new study out of Belgium.

Writing in the online journal PLos One, researchers describe an experiment in which 18 people walked while listening to playlists created from a pool of 52 songs. At first glance, the songs seem similar, in that they all had a tempo of 130 beats per minute. The people were instructed to walk in time with the music (as well as the sound of metronomes set at 130 beats per minute), and they did so almost 90% of the time. Keying one’s stride rate to music, it appears, comes naturally to most people, so putting faster songs on playlists should induce quicker turnover than running to slower songs.

But, despite almost always syncing their stride rate to songs, the walkers moved faster (i.e., they took longer strides) when listening to some of the songs. In addition, when listening to some songs, they walked more slowly than when listening to the metronome, despite the songs and metronome playing at the same tempo.

Why the difference, if all the songs played at 130 beats per minute?

A day or two after the walking experiment, the participants again listened to the songs they had heard when walking. They rated the songs on nine binary scales, such as “good/bad,” “tender/aggressive,” “soft/loud,” and “stuttering/flowing.”

The researchers then matched these qualitative descriptions of music to the ten songs that led to the fastest walking speeds, and the ten songs that led to the slowest walking speeds. After analysing what they called the “sonic features” of these songs, the researchers came up with broad characteristics of what they called “activating music” (faster walking) and “relaxing music” (slower music).

Activating music, according to the researchers, has features such as constant loudness over several beats, little variation, a downbeat (emphasis on first and third beats in a four-beat measure), and short notes that are repeated.

Relaxing music, in contrast, has more variation, greater contrast in volume levels, longer melodic phrases, and an upbeat (emphasis on the second and fourth beats).

If you’re thinking that these findings favour, for lack of a better word, simplistic music for working out, you’re correct. As the researchers put it, “As far as genre is concerned, pop-techno is more prominent in activating excerpts, while jazz-reggae is more prominent in relaxing excerpts. In general, the relaxing excerpts contain more variance in phrasing and melody, whereas the activating excerpts have a more equalised phrasing stressing a binary structure.”