From EAS Sports Nutrition :
Sin #1: Too much, too soon
"If women want their arms smaller, their abs smaller, or their thighs smaller, they typically will work those muscles every time they work out," says Melyssa St. Michael, a personal trainer and director of UltraFit Human Performance. But you need 72 hours to go through one metabolic cycle, which promotes healing of the tissue that was torn during your workouts. If you're training the same muscle group every day, your body won't have a chance to recover, slowing progress and leaving yourself open to injury. If you're a beginner, train your full body two to three times per week. Once you can do this with no soreness, train your upper body one day, your lower body on the second day, and take a day off on the third day..
Sin #2: Going cold
Going into your workout cold is a big no-no. Warming up lubricates the joints by thinning the synovial fluid that buffers them, which will give you a better range of motion and put you at a lower risk of injury. Brad Schoenfeld, a personal trainer and author of Look Great Naked and Look Great Sleeveless, suggests warming up with five to 10 minutes of a cardiovascular exercise at 50 to 60 percent of your maximal heart rate. If you're weight training, you can warm up by doing one to two lighter sets of each exercise before piling on the weights.
Sin #3: Not getting enough Z's
When you sleep your body releases growth hormones and repairs the trauma done to the muscles during the day. If you don't get enough sleep, you don't go into the repair and renew cycle that your body hits at its third to fourth hour of slumber. Everyone's a little different, but you should log in a minimum of six hours of snooze time per night. To get the best sleep, keep your room dark and cool, and use a noise generator, such as a fan, if your environment is noisy. Try to go to bed and get up at the same time every day.
Sin #4: Eating like a bird
Many women starve themselves and overexercise, according to St. Michael. But if you don't eat enough during the day, your body goes into starvation mode and slows down its metabolism, making it even harder to lose weight.
When you exercise intensely, your metabolism revs up for up to 46 hours after you've finished exercising-and this is when the greatest fat-burning effect takes place. But if you don't get enough calories for fuel, you can't exercise intensely enough to make this happen. Check out the sidebar to find out how many calories you should be getting every day.
Sin #5: Skipping the stretch
As we get older our muscles lose some of their elasticity, and as a result we lose flexibility. "That can cause postural problems and cause us to be more prone to straining a muscle," says Cedric Bryant, Ph.D., chief exercise physiologist for the American Council on Exercise. Stretching twice during your workout is optimal. By stretching after your warm-up you can prepare your muscles for exercise. And by stretching following your workout, while the muscles are warm, you'll improve your flexibility. For best results, hold each stretch for at least 10 seconds.
Sin #6: Ignoring the negative
If you focus on lifting a weight-the concentric or positive component-and then just let it fall back into place, your sin is in neglecting the negative. The process of letting the weight back down is called the eccentric component, and it's at least as important as the concentric component for stimulating muscular development. Ignore it and you'll only get half the results. In addition, there's a much greater probability of injury when you let gravity pull the weight down-this places the joints at a high potential for pulls and tears. Schoenfeld suggests lowering the weight twice as slowly as you lift it.
Sin #7: Not understanding your exercises
Admit it-sometimes you see someone doing an exercise you've never seen and say to yourself, "That looks cool! I think I'll try it." But not understanding the exercises you're doing is one of our deadly workout sins.
"It's important to understand what your goal is, and how the exercises are going to get you to that goal," St. Michael says. For example, many women do leg presses hoping to make their legs smaller. However, leg presses are a multi-joint exercise that tends to be a mass-builder for legs. On the other hand, single-joint movements such as leg extensions and leg curls concentrate on smaller muscle groups and lend themselves to a smaller, leaner look.
To learn which exercises will get you to your goal, consult a professional. You can hire a personal trainer, or the on-site trainers in your gym may be able to help you.
Sin #8: Having an "all or nothing" mentality
Your New Year's resolution is to start an exercise program, and you begin with a bang, working out like a demon every day. But then life happens - you catch a cold, or things get crazy at work, or you go on a vacation-and you miss a few days or weeks at the gym.
That's not the sin. The sin is having the attitude that because you let your exercise regimen slide, you may as well give it up for good. After all, exercise is only good if you keep at it, and if you skip it you've lost everything you've worked for, right?
"That's really not the case," St. Michael says. "Something is better than nothing, and even if you only exercise once a week for a month because you're on vacation, that's still four days of exercising. Keep in mind that this is a long term goal."
Sin #9: Getting stuck in a rut
When it comes to exercise, variety is the spice of life. "When you do, say, a shoulder exercise, you're training many of the fibers of the shoulder muscles, but not all of them," Schoenfeld says. "To work out all of the fibers in a muscle, you need to use different movements-using different angles or even just changing your grip on the weights."
This goes for cardio as well as weight training. "When you use the same exercise over and over, it's a repetitive motion task, just like typing at your keyboard, which can produce carpal tunnel syndrome," Schoenfeld says. So falling into a cardio rut ups your chances for injury.
Mixing up your workout also combats boredom-always a handy excuse for skipping the gym. Schoenfeld likes to change his routine from session to session, but he suggests giving your routine an overhaul at least once every six weeks.
Sin #10: Swinging weights
The ABCs of lifting weights are "Always Be in Control." When you use momentum to swing the weights around, you're not targeting the muscle that the exercise is meant for. Worse, Schoenfeld says, you're increasing your chances of injury. To squash this sin, make sure your lower back is tight and the only thing that's moving is the joint (or joints) related to the exercise you're doing.
Sin #11: Being too lightweight
You may think that if you lift too much weight, you'll bulk up to Schwarzeneggerian proportions. But it just isn't so. "Women don't have anywhere near enough testosterone to produce significant muscle growth," Schoenfeld says. If you want to get a good workout, you need to tax your muscles. "You should not be at the end of a set able to do five more reps," Schoenfeld says. According to Bryant, if you're using the right amount of weight, you should be able to perorm at least eight reps, but not more than 15, before your muscles are fatigued.
Sin #12: Nixing the H2O
When you exercise, you increase your metabolism and create heat. "If you don't consume sufficient amounts of fluids to maintain your hydration status, your body will conserve fluids, so you won't sweat as soon or as much," Bryant says. "As a result, you won't dissipate adequate amounts of that heat."
Do you want to drink water before, during or after exercise? The answer is all of the above. Down 16 ounces before working out, 4 to 6 ounces every 15 to 20 minutes during your workout, and then top it off with even more water after you're done exercising.