Mindlessly moving those dumbbells around is a start, says Perkins, but you’ll see better results faster—and avoid injury—if you avoid these 6 common strength-training mistakes:

  1. Your alignment is totally out of whack. “One incorrect body alignment point could mean the difference between a successful strength-training session that provides results and one that causes injury,” says Perkins. Luckily there’s an easy way to nail your form. These 5 body-positioning tips will set you up for success with any exercise—squats, biceps curls, etc.—that you’re doing. “Each step builds upon the next so that when you end up at the shoulders, your entire body is in proper alignment,” says Perkins. Try it: 1. Keep your feet flexed with your arches lifted. (You can achieve this by pressing into the outer edge of your feet.) 2. Press your knees outward. 3. Contract your butt muscles. 4. “Brace” your core: You can achieve this by contracting your torso in the manner that you would if you were anticipating a punch in the tummy. 5. Roll your shoulders back and down so that they move towards your hips. MORE: 3 Moves To Sculpt Shapelier Shoulders
  2. You’re not properly fueling before you lift. No Fuel = no energy = not a successful work out. “It’s important to have protein and carbohydrates on board to fuel your muscles and stabilize you blood sugar before your work out,” says Perkins. Exercise on empty too long, and eventually your body will begin to break down your lean tissue for fuel, moving you away from your goals. For optimum energy, Perkins suggests eating a meal (350 to 420 calories) 2 to 3 hours before you strength train, and grabbing a snack (around 200 calories) 30 to 60 minutes beforehand if it’s been more than a few hours since you last ate. Try this: Meal = Chicken (3-4 oz.), sweet potato (4 oz.), and ½ of an avocado. (Protein, carb, and healthy fat) Snack = String cheese and ⅓ cup of quick cook oatmeal. (Protein/fat and carb) MORE: 3 New Walking Workouts That Blast Fat
  3. And you’re not refueling after. Most women either don’t refuel at all, or wait too long. “There is a critical window to meet within 30 to 45 minutes of your workout,” says Perkins. “Every time you strength train, your workout causes microtraumas, or tiny tears, in the muscle tissue. When the muscle heals, it becomes thicker and stronger, and your muscles need protein and carbs in order to repair that ‘damage.’ If you don’t feed you body properly, your muscles will be unable to repair themselves, leading to chronic muscle soreness and less gains in lean tissue, slowing your results.” Perkins suggests aiming for roughly 10 to 15 grams of protein and 15 to 20 grams of carbs after a moderate workout (say, 2 hardcooked eggs and a small apple) and roughly 18 to 24 grams of protein and 24 to 30 grams of carbs if you really pushed it (try a smoothie with little pineapple and mango and a scoop of protein powder—here’s how to find the best protein powder for your needs).
  4. You’re stopping too soon. “The last two reps are the most important of every set; this is where you create real change in your body and where you create that microtrauma within the muscle that causes your body to rebuild more lean mass,” says Perkins. “So you really want those last few reps to be almost impossible to do with good form.” If you’re stopping before you reach that point, or you’re hitting those last few reps and not feeling much, your workout isn’t doing much. Increase the weight, the rep count, or both.  [block:bean=mkt-book-flexblock-lifttogetlean]5. You’re not using the proper weight. Most women are either lifting too much or too little weight. To determine how much weight you should be using, it all comes down to—you guessed it—the quality of those last 2 reps of every set. “The last two reps of each set must be a little bit sloppy compared to the first. This means the weight is perfect. If all the reps in your set are easy, you won’t be stressing the muscle enough to create the micro-damage that creates change in the muscle,” says Perkins. So, remember: Last 2 reps are easy = Increase weight More than the last 2 reps feel challenging = Decrease weight  MORE: 6 Ways To Make Your Workouts Less Miserable6. You’re not pushing hard enough. “Most women don’t fatigue their system enough to create change,” says Perkins.  “You need to work that point where you eventually say, ‘Whoa, I’m tired!’ " If your legs and arms feel heavy or shaky at the end of your routine—especially going up stairs or when you bend to pick things up—that’s a good sign. “And if you’re sore afterward, definitely allow two days of recovery before you strength train again,” says Perkins. After all, you earned it.