​1. Drink Too Much Water

You may think you'll hydrate your body before a sweat-it-out session, but in reality, drinking more than two glasses of water before hitting the gym could do more harm than help. All that H2O mixed with sprints and jumps could cause cramps, nausea, and in rare cases, a condition called hyponatremia, where your blood gets diluted and your body's sodium ion levels drop too low. The result? Loss of energy, cramps, and severe weakness.

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2. Eat Before a Workout (Versus After)

When you eat right before a gym sesh, you don't give your body enough time to digest the food, and that could make you throw up. And if your meal was spicy, that could lead to acid reflux or heartburn during your workout. Experts agree it's best to save that meal for after your workout, when your body needs the nutrition and can digest food well.

3. Take a Painkiller

What's that headache or sore muscle pill got to do with your treadmill, you ask? For one, most painkillers are muscle relaxants, so taking one before your workout means you won't be getting the best out of your session. But even more serious is this: popping an anti-inflammatory pill like ibuprofen before exercising could cause injury to the small intestine, found studies.

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4. Drink Alcohol

Yes, even that glass of wine at lunch. Alcohol can lower your blood-sugar levels, and cause dehydration in many people. And a combo of booze and exercise could lead to severe shakiness and weakness...and a sub par workout.

5. Static Stretching

That basically means stretching muscles while the body is at rest (for instance, touching your toes and holding for a few seconds). A few years ago, this was the recommended warm-up, but a slew of recent studies say a static stretch does more harm than help. In fact, doing it before your workout could actually make you slow and weak. Stretching is still important, of course, but save it for after your workout,

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