Jumping Rope, Cognition, Height, BMI, and Scientific Rigor

Does jumping rope help teens with obesity? We’re honestly not too sure. But a study that suggests it might is certainly stimulating some excellent dialogue between scholars. And it points to some surprising questions. For instance: does jumping rope for 75 minutes, twice a week over 12 weeks make teens grow taller? Think better? Become leaner?

The data from a 2018 study say maybe so.

The Original Study

Jen-Hao Liu and colleagues studied this 12-week program in 70 teens with obesity. They randomly assigned half of the kids to the program of jumping rope twice a week. The other half were wait-listed for the program. The primary objective was to study the effect on specific measures of cognitive function. Secondary objectives were effects on BMI and fitness.

At the end of the program, the investigators did find an effect on cognition. They also found an effect on BMI and fitness. All good news.

However . . .

When a group of other researchers led by Keisuke Ejima read this paper, the effects on obesity seemed extraordinary. So they requested the raw data to take a closer look. The journal, Psychology of Sport and Exercise, supported the request and the authors graciously shared their data.

Ejima et al found several anomalies and suggested that the original authors re-examine their findings and address a series of questions. And so they did. They confirmed some issues, found some others, and ultimately reconfirmed their original conclusions.

One of the interesting points was that the data showed teens in the exercise group had more growth in height than the control group. It’s not clear whether this is a real effect of the intervention or just a spurious finding, But it does catch our eye. The original authors note that it might be spurious, but also that it might be plausible. Fair enough.

Transparency and Rigor

The real point here, though, is the transparency, rigor, and collegial dialogue of this process. Dr. Ejima told us:

We both respected each other, and had a good communication. It served not only to improve this specific study, but also to demonstrate how to improve science by transparent conversation even after publication. I’m also impressed because the journal editor kindly encouraged us to publish our commentary when we first contacted him.

In other words, this is a model for promoting both scientific rigor and constructive dialogue between scholars. Well done.

Click here for the study, here for the subsequent analysis by Ejima et al, and here for the response.

Jumping Rope, photograph © Ken Walton / flickr

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October 26, 2019