Fitness Folklore

They cling like spandex. Pool like sweat under the Spinning bike. Stick around like that musty odor in the locker room. They’re the long-held beliefs that have been passed down through generations of fitness buffs. “Muscle will turn into fat if you don’t use it!” “Running on a treadmill is the same as running outside!” “If you’re not sweating, you’re not working hard enough!”

But as they say, behind every cliché, stereotype and generalization is a nugget of truth, so we decided to put five of the most common myths about exercise to the test and asked a panel of exercise physiologists to set the record straight. Here’s their final verdict on this stubborn fitness folklore. As for Bigfoot, the jury is still out.

Fitness Myth 1: Muscle turns into fat if you don’t use it.

The verdict: False

“This is like saying that if you wear eye patches and you don’t use your eyes, they’ll turn into ears,” says Michele Olson, Ph.D., a principal researcher at the Auburn University Montgomery Kinesiology Laboratory in Alabama. Muscle cells and fat cells are very different, and one cannot magically morph into the other even if it might seem like that’s happening. However, the sentiment behind this statement is correct in its own way: Muscle may not “turn into” fat, but if you’re not active, your body composition can certainly shift, meaning your muscle tissue shrinks while your fat cells grow.

“If you don’t use your muscles, they will atrophy — meaning they will lose size and weight,” says Steven Loy, Ph.D., professor in the Department of Kinesiology at California State University, Northridge. And because your body likes to be in a state of homeostasis — in which it picks a weight and tries to stay there rather than fluctuating up and down — it might add some fat to compensate for that muscle loss. “Therefore, you may actually end up gaining a few pounds of fat in order to maintain your typical bodyweight,” Olson says.

So does muscle turn into fat? No. But you can gain more fat than you had been carrying previously if you stop exercising, hence the “skinny-fat” phenomenon.

Fitness Myth 2: Running on a treadmill is the same as running outside.

The verdict: False

The knee-jerk answer here is typically a negative because with outdoor running, you’re propelling yourself forward along the ground instead of the ground moving beneath your feet. Plus, there are the environmental factors to consider. “When outside, the practical interactions with the environment, such as wind and terrain, make that workout require more effort,” says James McKenzie, Ph.D., a lecturer in the Department of Human Physiology at Gonzaga University in Washington. Wind also provides resistance and cools you off, which obviously does not occur in an indoor scenario.

However, putting your treadmill on an incline of 1 or 2 percent can simulate much of the same effect as running outside, according to Wendy Repovich, Ph.D., FACSM, director of the exercise science program at Eastern Washington University. “If you work on the treadmill at a similar heart rate [like an outdoor run], your caloric cost and the intensity of the exercise will be similar,” Loy adds.

So don’t worry too much about which modality is better; they’re both good. Just pick one and get moving.

Fitness Myth 3: Machines are safer than free weights.

The verdict: False (with a little truth)

Because they’re not anchored to the ground, free weights can certainly injure you if they are dropped on your toe, chest, knee or face. In that respect, then yes, machines are safer by virtue of locking you into a set range of motion and removing some of the balance requirements of free weights.

But machines come with their own set of issues, not the least of which is adjustment failures. For example, if your seat is not adjusted to the right height and distance during leg extensions, you could strain your back or the tendons around your kneecap. “This doesn’t happen when you do a dumbbell lunge,” Olson says. “Your body naturally aligns itself with respect to the length of your femur and you can take a longer stance, which will keep the knee from tracking too far over the toe.”

In truth, both kinds of equipment are effective and plenty safe when used with conscious attention to form, function and proper adjustments.

Fitness Myth 4: If you’re not sweating, you’re not training hard enough.

The verdict: False

Perspiration is a passive process designed to keep you from getting overheated, and sweat is more a measure of the environmental dew point and humidity than exertion; otherwise, people in Miami would always be getting a “better” workout than people in Phoenix.

“A harder workout may cause more sweat, but it’s the intensity of the workout that will cause you to burn more calories,” Olson says. “When doing light exercise in a very hot room, you might drip buckets, but you won’t burn any more calories than you would doing the same workout at a comfortable temperature where you may sweat less.”

A better way to measure intensity is by monitoring your heart rate, according to Loy. Intense workouts such as Tabata, AMRAP (as many reps as possible) and other kinds of high-intensity interval training can spike your heart rate into the 90th percentile of your max, while a lower-intensity workout such as strength training or endurance cardio will hover around the 70 percent mark.

But at any intensity, some of us will sweat, others not so much. It doesn’t mean we’re not getting the same workout.

Fitness Myth 5: Cardio burns more calories than weight training.

The verdict: It’s complicated

Ultimately, it’s the intensity of an activity that determines the calories burned. For instance, during a 45- to 60-minute session of steady-state cardio, you will burn more calories during the actual session itself than you would spending the same amount of time lifting weights in a single straight-set format for something like arms or shoulders. “When you weight-train, you lift, then rest, so you aren’t burning calories the entire time,” Repovich explains.

But amp up the intensity of the lifting workout to include compound movements, large muscle groups and shortened rest intervals and the calories burned also ramps up. Now increase the weight being lifted and blend cardio bursts into the strength moves to create a circuit and the calories burned goes up again. (You can see where this is going.)

In addition, the calories burned for strength training should be accounted for over a period of at least 24 hours. “You’ll burn more calories and have more afterburn — aka, the energy expended to recover after an exercise session is complete — from lifting heavy weights,” McKenzie says. This afterburn is known as EPOC — excess post-exercise oxygen consumption — and it represents the amount of calories your body needs to recover from exercise. Two things determine a workout’s EPOC: intensity and duration because both apply stress to muscles.

To further complicate things, there is HIIT, which provides a completely different caloric burn than a steady-state cardio session. In fact, research out of Olson’s lab found that four minutes of a HIIT workout using jump squats burns the same amount of calories as walking for 20 minutes at a 4.5-mph pace.

So which burns more calories? Answer: neither. Both are equally effective and can blast tons of calories if you maintain high intensity throughout your session.