There's not much we could do without our muscles -- swallow, breathe, move at all [1] . Yet despite how essential muscles are to our survival, there's still a lot we don't know about them and how they work. Here are six fun facts you may not have known about your muscles.




There isn't just ONE strongest muscle in your body.


tongue


You've probably heard that your tongue is the strongest muscle, and while it is certainly impressive -- with its "combination of elasticity and forcefulness" -- LiveScience explains that there are too many different ways to measure strength to crown any one muscle strongest[2] . The calf muscle, for example, is actually the muscle that exerts the most force, while the jaw muscle exerts the most pressure. And the gluteus maximus is the biggest muscle in the human body.




Muscles grow while you sleep.


muscles sleep

All that work you put in at the gym pays off after you hit the hay. In the deep and restorative stages of sleep[3] , the muscles relax and blood flow to the muscles increase. Hormones that fuel muscle development are released[4] and tissues grow and repair, according to the National Sleep Foundation. Without enough deep sleep, don't expect to see results at the gym.




Muscles make 85 percent of your body heat.


body heat


When muscles contract, they give off heat -- enough of it to account for most of what keeps you warm and toasty, according to the National Cancer Institute. Muscles are also at work when we shiver[5] : When the skin receptors send "brr" signals, the brain triggers some rapid-fire, involuntary muscle contractions -- those shivers -- to heat things back up.




It's easier to gain muscle than lose it.


gain muscle


Fall of the wagon, and you'll probably only lose half your bulk. That's because it seems to take twice as long to lose new muscle[6] as it does to build it. One study found that new exercisers gained 47 percent more strength in two months of weight training. Then, after two months of taking it easy, they only lost 23 percent of that strength, Fitness magazine reported.




Muscle burns more calories than fat.


muscle burns calories


Your resting metabolic rate -- the number of calories you burn each day without doing a dang thing -- is intricately linked with your body composition. Muscle is more "metabolically active" than fat[7] , meaning it naturally burns more calories when you're at rest. However, it's not enough to make the pounds just melt away. One pound of muscle at rest only burns six calories in an entire day, compared to the two calories a day burned by a pound of fat, the LA Times reported.




Muscle tissue makes up 35 to 40 percent of your body weight.


muscle tissue


There are three types of muscle tissue -- skeletal, cardiac and smooth, and about 650 layers of skeletal muscle[8] in the body.



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  • The Lunk


    <strong>The look:</strong> More muscles from head to toe than between the ears. Tank tops required, short shorts preferred. <strong>The workout:</strong> Lifting free weights impossible for anyone else to pick up or hogging the bench press. <strong>The mantra:</strong> <a href="http://www.youtube.com/watch?v=q7gzmoqmL7g" target="_blank">"I pick things up and put them down"</a> -- but only communicates in grunts.




  • The Beauty Queen


    <strong>The look:</strong> More makeup than you'd wear on your wedding day. Ponytail optional. <strong>The workout:</strong> StairMaster <strong>The mantra:</strong> <a href="http://www.huffingtonpost.com/2013/07/19/worst-fitness-quotes_n_3618176.html" target="_blank">"I don't sweat, I sparkle."</a>




  • The Nudist


    <strong>The look: </strong>Shirtless on the treadmill, maybe even barefoot. Naked in the locker room long enough to make everyone else uncomfortable -- and that's <em>before</em> they start talking to you. <strong>The workout:</strong> Abductor and adductor machines <strong>The mantra:</strong> "Well, as Marilyn always said, '<a href="http://www.brainyquote.com/quotes/quotes/m/marilynmon116142.html" target="_blank">The body is meant to be seen</a>, not all covered up!'"




  • The Talk Show Host


    <strong>The look:</strong> Serious chatter. Will be accompanied by guest. May sometimes resort to cell phone. <strong>The workout:</strong> The only thing getting a real workout is that mouth. <strong>The mantra:</strong> "And then <em>she</em> said..."




  • The Tenant


    <strong>The look:</strong> Like they own the place. The tenant uses three towels, two lockers and a whole bench in the locker room. He or she spreads shower supplies, hair accessories and makeup on every available inch of counter space. May be seen eating takeout in locker room. <strong>The workout</strong>: Stretching perpendicularly to everyone else on the mats <strong>The mantra:</strong> "Mi casa es... mi casa."




  • The Couch Potato


    <strong>The look:</strong> Zoned out on a treadmill in front of a TV or on an elliptical with a month's worth of US Weekly <strong>The workout:</strong> Does turning pages count? <strong>The mantra:</strong> "What channel is 'Friends' on?"




  • The Mayor


    <strong>The look: </strong>High-fives trainers and instructors, introduces himself to new faces, has his name on his locker and the rules about cutting locks left overnight don't apply. <strong>The workout:</strong> You mean, the gym <em>isn't</em> just for socializing? <strong>The mantra:</strong> "You come here often?"




  • The Forgetful


    <strong>The look:</strong> Flip flops, jeans, non-jog bra -- whatever the missing element is, it's clear <em>some</em> crucial piece of gym gear just didn't make it into his or her bag this morning. <strong>The workout:</strong> You'll know you've encountered a Forgetful when she's squeezing in next to you at Zumba five minutes after class started. <strong>The mantra:</strong> "I know it's in here somewhere..."




  • The Lunch-Breaker


    <strong>The look:</strong> Business casual. <strong>The workout:</strong> Anything that can be done in 10 minutes flat -- or less -- without mussing up the hair. <strong>The mantra:</strong> <a href="http://www.goodreads.com/quotes/28440-the-greatest-wealth-is-health" target="_blank">"The greatest wealth is health."</a>