Mind & Body

3 Things Gym Class Got Wrong

Gym class, PE, phys ed, nerd punishment hour — whatever you call it, chances are it doesn't bring back happy memories. For the less athletic (or more musically gifted, am I right?) among us, it was an especially tortuous chunk of the school day. Well, it should be a relief to know that a lot of the things they challenged you to do were flat-out wrong. Exercise science has moved on, and left some gym-class staples in the dust.


If you were a student in the U.S. at any point between 1966 and 2012, you probably remember the Presidential Physical Fitness Test. It was originally designed to ensure young Americans were ready for the physical demands of military service, but if you ask most kids, it was really designed to highlight the stark divide between the jocks and everybody else.

The test changed with almost every administration, but one long-standing component was the sit-up: a test of abdominal strength that eventually gave way to the gentler curl-up, or crunch. Unfortunately, all of these exercises have proven to be a back-injury risk and an inefficient way to build your abs, to boot. According to a 2005 study, 56 percent of soldiers who sustained injuries during the Army Physical Fitness Test did so while doing sit-ups. That's because they put a dangerous amount of compressive force on the spine, which can lead to bulging and herniated discs.

What to do instead: To build stronger core muscles, most fitness experts now advise doing stabilizing exercises like planks. To do one, start by getting in a push-up position on the floor. With your arms either outstretched with your hands on the floor or bent 90 degrees with your elbows on the floor, keep your body in a straight line, tighten your muscles, and see how long you can hold that position. Start at 30 seconds, and try to work your way up to two minutes.

Static Stretching

In most gym classes, the first thing the teacher had you do every day was stretch. You'd roll your neck, touch your toes, and pull your elbow across your chest, holding each pose for 20 seconds or more. The idea was that holding a stretch like that would help warm up your muscles and reduce your risk of injury once you started the day's rousing game of pickleball (who chooses these sports?).

But in the early 2010s, research started to show that static stretching before athletic activity actually makes you weaker, without substantially reducing your risk of injury. In 2013, a huge review of the research found that static stretching reduces strength in the stretched muscle by more than five percent, power by two percent, and explosive performance — the kind you need to serve a tennis ball or block a basketball shot — by nearly three percent.

What to do instead: If you're getting ready for a workout, experts recommend dynamic stretching over static stretching. Dynamic stretching keeps the muscles in motion — think jumping jacks, straight-leg kicks, and lunges, which better prepare your body for its upcoming workout. Static stretching isn't useless, however. Once your body is warmed up after exercising, holding a few stretches for 90 seconds or less can help boost your flexibility over time.

Related Video: Why Is It So Hard to Start Working Out?

Body Mass Index (BMI)

Survivors of high school gym class are full of stories about callous teachers announcing their body mass index (BMI), a rough measure of body fat and general health, to the entire class. BMI is a simple height to weight ratio, and was (and is) used to tell where a person falls on the spectrum from underweight to obese. Many schools assess their students' BMIs to keep tabs on their health.

But a growing body of research is showing that BMI is a lousy indicator of health. That's especially true when you use it alone, as schools often do. That's because weight is made up of fat and muscle, so particularly athletic or muscular people might have overweight BMIs while normal-weight individuals with a dangerous amount of belly fat might be marked as perfectly healthy.

In 2016, UCLA researchers published a study finding that 47 percent of people with overweight BMIs and 29 percent of people with obese BMIs were healthy according to five of six other accepted metrics, such as blood pressure and cholesterol. At the same time, 31 percent of people with normal-weight BMIs were considered unhealthy by two or more of those metrics.

What to do instead: Research is showing that your waist-to-hip ratio may be a better health measure than your BMI. Measuring your body-fat percentage is also useful, especially if you're tracking weight loss.

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For more science-based fitness tips, check out "Bigger Leaner Stronger: The Simple Science of Building The Ultimate Male Body" or "Thinner Leaner Stronger: The Simple Science Of Building The Ultimate Female Body" by fitness expert Michael Matthews. We handpick reading recommendations we think you may like. If you choose to make a purchase through that link, Curiosity will get a share of the sale.

Written by Ashley Hamer November 27, 2017

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