Friday, June 28, 2013

The 4-Minute Workout: Reality or overly ambitious research conclusion?

A lot more people, including myself, are talking about minimalist training for endurance sports. I wrote in a previous blog how I adapted and successfully used high-intensity intervals to structure my training to post a Boston marathon qualifying time.

An eye-catching article ran in the New York Times’ wellness blog a couple weeks back with the headline “The 4-Minute Workout.” It opened by saying, “Thanks to an ingratiating new study, we may finally be closer to answering that ever-popular question regarding our health and fitness: How little exercise can I get away with?”

With more and more people feeling the time squeeze, and with increasing evidence pointing to the negative health consequences of sedentary lifestyles, this is a valid question. The article went on to reference the positive findings of a recent study published in the journal PLoS ONE, which showed that a single bout of four minutes at 90% of maximum heart rate performed three times a week elicited similar improvements in VO2max, blood pressure and fasting glucose to that of a four by four minute protocol. 

This sounds great! Why don’t we all just cut down on our training time?

I’m not one to shy away from pointing out the shortcomings when it comes to the media accurately reporting on scientific research. But this time it’s a classic case of the researchers overgeneralizing the research findings beyond the studied population. (There is also a pretty big glaring overreach by the NY Times article – both exercise protocols included a 10 minute warm up and 5 minute cool down. So, if you’re really looking at TOTAL TIME for the workout, it would be 19 minutes, NOT 4 minutes.)

Let’s take a closer look.

In the methods section, the authors describe the study participants:
“Twenty-six inactive but otherwise healthy overweight men [my emphasis] (BMI: 25–30, age: 35–45 years) were recruited for this investigation at St. Olav's hospital, Trondheim, Norway (study period: 05.01.2009–03.04.2009).”
**Note the subjects were exclusively young/middle-aged MEN.**

Later, in the discussion section where the authors interpreted the study results, they say:
“The present study demonstrates that a relatively intense stimulus administered only once and for a relatively short duration can substantially improve VO2max and work economy. A single bout of 4-minute interval training three times per week will not solve all lifestyle-related problems for people already obese or overweight, and it is not the only solution for inactive persons with a BMI below 25. However, brief interval training can have a central role in public health and lifestyle medicine initiatives, in addition to changes in nutrition and other, less intense physical activity [my emphasis].”
**Despite the known hormonal differences between men and women when it comes to responding to high intensity training, the authors still apply their findings to ALL individuals, rather than to just MEN, which was the study population.**

The study did include a section on limitations, but failed to mention anything on this, and later concluded:
“Our study demonstrated that slightly overweight and healthy individuals [my emphasis] only required brief, duration bouts of exercise with good effort three times a week, to produce large increases in VO2max and work economy and reduce blood pressure and fasting glucose levels.”
As researchers (and I include myself in this statement) we have an obligation to accurately describe and communicate a study’s findings. When this fails to happen, misinformation is only compounded down the line (especially in the popular media), which doesn’t help matters for the average American trying to make heads or tails of what they should be doing.

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