The Biggest Cardio MYTHS You Should STOP Believing.

At the end of a rough day, the rhythmic swooshing of the elliptical, whir of a bike, or patter of feet on the belt of a treadmill might sound like music to your ears—for stress relief, cardio is tops. It's also, of course, awesome for your heart (um, it's in the name), and a definite calorie burner (though you already know not to trust the calorie counter on the display). Still, while all that good stuff is true, there are a lot of fallacies running around out there, and following them may be stopping you in your fitness tracks. Here, five of the biggest cardio myths:

MYTH #1: Cardio, cardio, and more cardio is the ticket to faster weight loss.

FACT: Hours logged on those fast-paced gym machines are a sure-fire way burn down the fat—after all, it's calories in versus calories out, right? Well, yes, but... "You may lose weight faster doing cardio only, but unfortunately it's the wrong kind of weight," says Kansas City-based personal trainer Greg Justice. Cardio alone burns away both fat and muscle.  For a lasting change, you have to integrate Strength workouts into your routine. "Weight training (lifting weights) builds lean muscle mass, which elevates your metabolism and burns more fat, even when you're not exercising," says Justice. He recommends Metabolic Resistance Training, a hybrid method in which weight training is done at a fast pace, with minimal rest.

MYTH #2: If you don't have an hour to commit to the cardio gods, it's not worth it.

FACT: This is a BIG BIG LIE. All body movement has benefits in terms of calorie burn. What you can change, though, is how efficiently you burn them. "You may be able to do steady-state cardio longer, and burn more calories during that time, but the key is what happens after your workout," says Justice. "By doing high-intensity interval training [HIIT], which means you incorporate intense periods of work with short recovery, your metabolism is elevated and you'll be burning calories for up to 38 hours after your HIIT workout is completed." If you prefer to pray at the altar of the treadmill, take heart. "The American Heart Association says that doing three 20-minute sessions of cardio at a vigorous intensity [like running] is the equivalent of doing five 30-minute sessions at a moderate level [like fast walking]," says exercise scientist Wayne Westcott, Ph.D. Even 10 minutes at a high intensity is beneficial. And a recent study suggests that short, infrequent bouts of slow running can do your heart good. So no excuses that you don't have the time!

MYTH #3: Doing cardio on an empty stomach Burns maximum body fat.

FACT: This one comes from the idea that if your body doesn't have readily available food calories, it'll dip into the body's stored supply, shrinking that fat belle. Research bears out that the opposite is true: A 2011 meta-analysis concluded fat burn is consistent regardless of whether or not you've eaten before a workout. And other research shows a negative effect of muscle catabolism (a.k.a. muscle loss) from skipping a pre-workout snack. "Your body needs energy to perform and energy comes in the form of food,” says Justice. "I'm not talking about gorging yourself, but having a small snack before doing cardio can actually help you perform at a higher level."

MYTH #4: It's important to stay in the "fat-burning zone" if your aim is to burn fat.

FACT: Like a lot of fitness fallacies, this one is half true. At a lower intensity—the heart rate deemed the "fat-burning zone"—you will indeed burn a greater percentage of your calories from fat. But, as Westcott explains, it's total calories burned (those pesky calories out) that matter for weight loss. The math: If you run at seven miles per hour, you burn 25 percent of your calories from fat, while walking at half that speed burns 40 percent from fat, says Westcott, citing past research. So far, walking has an edge. However, at that seven miles-per-hour pace, let's say you'd burn about 500 calories in 30 minutes, or 125 fat calories. At the 3.5 mph walking pace, let's say you'd burn about 250 calories in the same time (and 40 percent of 250 is only 100, so the "fat-burning zone" doesn't win that race, either). Bottom line: Working out at a higher intensity equals more pounds lost.

MYTH #5: If you go for a run or a bike ride, you can skip a legs' strength workout.

FACT: Unless you're doing full-on sprints uphill or cranking the bike's resistance to the point where you can barely push the pedals (and yet you push), you ain't getting much muscle-building benefit from your workout. So while you feel like your legs and glutes did some work, in order to get the awesome metabolic gains of building up those largest muscles in your body, you have to incorporate strength moves like squats, deadlifts, and lunges.