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When it comes to your body, knowledge is power. Literally. The better you understand your muscles and what they're capable of, the more you can do with them, whether you're acing a serve or turning heads at the pub.
But when there are about 650 muscles, and millions of individual fibers, to get intimate with, it's more than a little daunting. So we're going to keep it simple. Here's the least you need to know to get the most from your muscles.
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Let's start with the 101. You have three types of muscles: the cardiac muscle found in your ticker, the smooth muscle that lines such organs as your stomach and esophagus, and skeletal muscle, which attaches to your bones via tendons.
Skeletal muscles are the ones you use to suck in your stomach at the beach or load a new plasma TV into your carÃ¢â‚¬”in other words, the kind that you're most aware of as you go about your day. They make up 30 to 40 percent of your body mass and are largely voluntary, meaning you make them moveÃ¢â‚¬”minus the occasional involuntary blip when someone scares the crap out of you.
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How many muscle fibers you have was determined by the time you dumped your middle-school boyfriend. "The number may increase early in life, but it becomes set at puberty," says C. David Geier Jr., M.D., director of sports medicine at the Medical University of South Carolina.
What you can control: how big the fibers get, which determines how tight and strong you look.
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When you cut your finger, your body heals, but it often overcompensates by leaving a scab. Something similar happens with your muscles. Hoisting a barbellÃ¢â‚¬”or a babyÃ¢â‚¬”can cause microscopic tears in the fibers.
As a result, your muscles send a signal to nearby cells to swoop in. The cells trigger the formation of proteins at the "boo-boo" site, and that increases the size of the muscle. After weeks of dedication to a solid workout, you'll see results.
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All muscle fibers are not created equal. Slow-twitch fibers are like your mom's speed-walking club: They're perfect for endurance but don't pack a lot of power. Fast-twitch fibers do the opposite: They offer bursts of rapid-fire energy, but only for a short time.
Your genes control how much of one type or the other you have. If you're looking to jack up your endurance for a marathon, hone your slow-twitchers by lifting 2 to 3 sets with lighter weights, eking out 12 to 15 reps, suggests Jason Conviser, Ph.D., an exercise physiologist at the Center for Partnership Medicine at Northwestern Memorial Hospital in Chicago.
If you want to improve your 5K kick, try cranking out 2 to 3 sets of 6 to 8 reps at a heavier weight.
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When you fire a power-punch in kickboxing class, your brain sends a signal down a nerve cell, telling certain muscle fibers in your arms, back, core, and legs to contract.
After a series of microscopic chemical reactions Ã¢â‚¬” bam! Ã¢â‚¬” you deliver the KO blow. As you practice, your brain and muscles learn to communicate more efficiently and you become more coordinated.
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In 2007, researchers found that when healthy men and women spent 4 weeks visualizing themselves lifting weights, their actual strength went up 4 percent — without their hoisting a single dumbbell.
By comparison, a group that actually strength trained gained 5 percent, and a control group that did nothing lost 0.2 percent. The deal: Thinking about exercises may help bolster the pathways between your brain and your brawn — so, while your muscles haven't gotten much stronger, your cranium has perfected how the muscles execute the movement. The happy conclusion is that if you can't fit "gym" on your to-do list, thinking about exercise is an okay stopgap.
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For the last time, weight lifting will not turn you into a raging green superhero. It's just not in your blood. "Testosterone helps men gain bulk," says Suzanne Meth, M.S., C.S.C.S., a manager at Equinox Fitness in New York City.
When men lift weights, the hormone causes their muscle fibers to grow. Since we have 20 to 30 percent less testosterone than guys do, we gain strength without the heft. Your chances of getting scary big? Nearly zilch. Even if you have more T than average, to Hulk up you'd have to quit your job, spend 24/7 eating and working out in a very specific way, and slather on buckets of baby oil.
When researchers compared the muscle strength of men and women, they found that men were about 50 percent stronger than women. But when they factored in body weight and muscle weight, they discovered that, on a muscle-for-muscle basis, women are just as strong as men, according to Wayne Westcott, Ph.D., C.S.C.S., fitness-research director at South Shore YMCA in Quincy, Massachusetts.
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It's the width of your shoulders, says Lou Schuler, coauthor of The New Rules of Lifting for Women. Schuler says there's generally not a lot of fat around a woman's deltoids, so muscle growth there is more defined under your skin. Major plus: Wider shoulders make your waist appear smaller Ã¢â‚¬” so, yeah, it's all good.
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For decades scientists thought the burning sensation was a result of your body's producing lactic acid to slow you down when you're going too hard. Seemed logical, until last year, when researchers at the University of California, Berkeley discovered the real reason your muscles burn. Turns out that although the burning is caused by lactic acid, it's not your body putting the breaks on your workout.
The acid actually is a main source of fuel for your muscles. When you push yourself, your muscles convert glucose from food into lactic acid, which is moved via proteins to the mitochondria, your muscles' energy factories. The more you work out, the more efficiently your body uses lactate as fuel — which means you can go longer and harder. Love the burn. Eat right for your muscles—Download the 12 Best Foods For Your Abs List!