Four fitness myths to avoid in the gym

The first of April is all about getting pranked but in the health and fitness business, it can be tough to sort the science from the swindle. Here are four myths to bust before you head to the gym:

Stretching before a workout prevents injuries. Not true. What does help your workout is a short warm-up to improve blood flow and muscle contraction. Warm-up can also improve your psychological state. A good warm-up involves exercising all of the major muscle groups for ten minutes or so at an intensity that is not fatiguing.

And speaking of exercise intensity... 220 minus your age to compute your maximum heart rate is a lot of baloney too. How this works (if you are 40, for example) is to subtract 40 from 220 and then assume that 180 is the maximal number of times your heart can beat per minute. You are then supposed to multiply 180 by various decimals to determine your exercise target heart rate. The “220 minus your age” equation was developed by Stanford professor, William Haskell in 1970 to get a handle on how hard patients with heart disease could exercise. It is not very helpful for the general population. Instead, use the talk test during activities like biking and running. If you can just about maintain a conversation, you’re probably exercising at a moderate intensity which is perfect for most readers of this column. Get as many minutes of that intensity

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into your day as you can even if it means breaking them up into multiple bouts throughout the day.

One myth that makes me laugh is the one from women who won’t weight train because they don’t want to bulk up. Gurrrrl, I’m in the gym regularly, eating a protein-rich diet, and I’ve got testosterone going for me and even I can’t bulk up! It’s not going to happen for you either just because you did a few planks. What might happen within a few hours of a hard workout is something called “reactive hyperemia”. This is nothing more than a temporary increase in blood flow to your muscles. It is not the same thing as protein synthesis. It might make your clothes feel snug for a few hours but it’s no reason to avoid the important health benefits of weight training.

Finally, my favorite myth of all: The personal trainer who tells his client that they weigh more now because they’ve gained muscle mass. Fat chance. Real lean body mass takes months to accrue. It is a function of consistent training, a high-energy diet, rest, and good genetic luck. If you weigh in differently after a few sessions with your trainer, the fluctuation is due to water, not fat turning into muscle either.

The benefits of exercise take time. Why waste it on fitness fairy tales? Avoid these myths and hire a trainer. A good one will ensure that you’re making the best use of your time.

Dr. Berger is an exercise physiologist with Arizona State University.

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