1. You chug a ton of water before you work out.
You know you need to keep the water coming on days when you work out. But if you down a whole liter of water before a workout, it will sit in your stomach and could lead to nausea and cramping that makes you want to cut your workout short, says Amanda Foti, a registered dietitian from Selvera, a nutritional counseling company based in New York City. Drink a few sips before your workout (especially if it’s first thing in the morning), and bring a water bottle to the gym to sip while you sweat. Just don’t force it down.
2. You sweat on an empty stomach. Your car doesn’t run on an empty tank and neither do you. When you eat carbohydrates in particular, your body turns the food into fuel that your muscles store and release when you exercise, Foti says. Eat a small snack — like a low-fat Greek or regular yogurt, a low-fiber granola bar, whole-grain toast with a schmear of peanut butter, or a handful of trail mix — about 20 to 30 minutes before a workout to help you burn and use that stored fuel efficiently. If you work out so early in the morning that breakfast feels like a midnight snack, go for the bare minimum: a piece of fruit.
3. You eat a Thanksgiving-size meal before your workout. While it might seem like a good idea to fuel up, then work off those seconds (and thirds) at the gym, digestion is hard work in and of itself: It drains your body of the energy it needs to pick things up and put things down at the gym. Plus fullness + treadmill = nausea. If you work out in the evening, do it after a snack (see above) but before dinner, Foti says.
4. You lose sleep to hit the gym. When you skimp on sleep, your body has to work extra hard to keep things like your nervous system running smoothly, says Kelvin Gary, certified head trainer and performance coach and owner of Body Space Fitness in NYC. This elevates your heart rate and tires you out even before you add weight lifting and cardio to the mix. And if you do power through? Lack of sleep can impact your ability to balance, focus, and burn calories efficiently, meaning you probably won’t work as hard as you usually do. Instead of going through your workout like a zombie, sleep in and go to the gym later.
5. You overdo it on the coffee. If you’re used to drinking coffee, an eight-ounce cup of it can help you stay hydrated and boost your energy so you can work out for longer or at a higher intensity than you would without the caffeine boost, Foti says. However, people who don’t regularly drink coffee or drink too much (Put. Down. The. Trenta.) could experience some icky digestive side effects, like the urge to sprint to the bathroom in the middle of class.
6. You eat a bowl of high-fiber cereal right before. Because you digest high-fiber foods slowly, it takes especially long for your body to turn the food into energy, Foti says. And while fiber can help you feel full longer, it won’t help you if your goal is to turn food into fuel ASAP and get through your workout. If you’re not used to eating loads of fiber, you can bank on bloating and gas and an all-around uncomfortable workout. If you must fiber up, Foti says to go in for the kill two to three hours before your workout.
7. You don’t set a goal or make a plan to reach it. You don’t have to be training for a marathon to set a fitness goal: Goals give your workouts purpose and direction, so you can focus on exercises that deliver the results you’re looking for, Gary says. For example, if your goal is to lose weight, you might want skip the treadmill and opt for squats with an overhead press. The efficient move activates multiple large muscle groups and builds lean muscle mass that amps up your calorie burn at rest. If you’re not sure where to start (besides the empty treadmill), check out CosmoBody, the new fitness video channel.
9. You go to drunch or happy hour before the gym. Is it OK to drink just a little bit before you hit the gym? Common sense says that it’s hard to stop at one mimosa and that workouts where you feel even a little bit tipsy are dangerous. Plus, who wants to waste a perfectly good buzz on a workout? Terrible idea.
10. You skip the stretch. Dynamic stretches (like lunges and high knee grabs) increase the temperature and blood flow in your muscles. This reduces your risk of injury and increases your flexibility so you can do the actual workout more effectively, Gary says. Stretch for up to five minutes — you’re done when you start to sweat or feel your heart rate go up.