In a 115-Person Plank Study, Being Cheered On Cost Partners 31 Seconds

Online plank partners held the position longer than people planking alone, by 78.8 seconds in a 2013 Michigan State University study, but weaker partners who were encouraged by the stronger player held it 31.14 seconds less than those who weren’t. The cheering made their result worse.

What did Irwin, Feltz and Kerr actually run?

Irwin, Feltz and Kerr recruited 115 people, online and from the Michigan State campus, and had each play, in a laboratory, an exercise video game that required five abdominal planks, each held for as long as possible. That was Time 1. Everyone then did the five planks again (Time 2) under one of three conditions: alone, with an Internet partner who stayed silent, or with an Internet partner who gave verbal encouragement.

The task was built so that the pair’s result equalled the result of the weaker member. This is the setup behind the Köhler effect, named for the German psychologist who first saw it: the less capable member of a group works harder when the group’s outcome is only as good as their own. If the term is new, the Köhler effect, defined covers where it comes from.

The numbers, as the authors report them: 80 people exercised in online teams and 35 alone. Team members lasted 78.8 seconds longer (P<.001). Within the teams, those whose stronger partner encouraged them (n=55) did worse than those whose partner stayed quiet (n=25), by a mean of 31.14 seconds. Self-efficacy, enjoyment and intention to exercise again did not move.

Why would cheering backfire?

The authors’ explanation is careful. Encouragement from the stronger member can reduce the boost “especially if one perceives such comments being directed at someone other than themselves.” Put plainly, when the strong player is praising the group, the weak link may hear that the group is fine and relax. When nothing is said, the weaker player has only the silent comparison with a better partner, and that comparison is the engine.

That reading is the authors’ and mine together, and it is a hypothesis about mechanism. The abstract does not show the mechanism being measured.

Is a wake-up witness a plank partner?

Not quite, and the difference matters. A person watching your wake-up video is not a stronger player whose speed caps yours. The study’s penalty applies to a conjunctive task, where the group score is its weakest score. Waking up is closer to a solo task with an audience.

Still, the finding carries one transferable caution. In this one setup, the pressure came from the other person’s visible standard rather than their warmth, and the same may hold for witnesses. A friend who texts “you’ve got this!” at 5:50 a.m. may be adding comfort rather than force. A friend who simply sees whether you showed up leaves the standard intact.

Three limits, stated before anyone leans on this. The sample was 115 people in a laboratory, doing one exercise for a few minutes. The abstract covers a single session, not weeks of habit. And the finding concerns one direction of encouragement, stronger to weaker, so it says nothing about a friend cheering you after you succeed.

What would a sensible witness do with this?

Don’t tell them to stop caring. Ask them to separate two jobs: noticing, which is the part that carried the effect, and cheering, which can wait until the thing is done. If you’re setting up a witness, how to ask someone to be your accountability witness is a practical script, and you can add one line to it: “Tell me afterwards, not during.”

DontSnooze is built around a witness who sees the outcome rather than cheering the attempt, which suits this finding by coincidence; the plank study never tested it, and the app can’t stop a friend from texting encouragement on the side. The practical summary is short: save the praise for after.

FAQ

Did the 2013 plank study test alarms or waking up? No. Participants held abdominal planks in an exercise video game in a laboratory. Any link to waking up is the writer’s analogy, not a finding.

How large was the encouragement penalty? The abstract reports a mean difference of 31.14 seconds in exercise duration between partners who received verbal encouragement (n=55) and those who did not (n=25).

Does the study say encouragement is bad? Only for one setup: a stronger partner encouraging the weaker one in a task where the pair’s score equals the weaker member’s. Encouragement did not change self-efficacy, enjoyment or exercise intention in either direction.

Where can the original be read? Irwin BC, Feltz DL, Kerr NL. Silence is golden: effect of encouragement in motivating the weak link in an online exercise video game. Journal of Medical Internet Research, 2013;15(6):e104. doi:10.2196/jmir.2551.