1. Lifting too much weight too soon.
This generally applies to newbies. The risk of torn ligaments, tendonitis, joint arthritis, and stress fractures, to name a few, is increasing. The more weight you lift, the greater the risk. If your muscles are properly stretched/warmed up, you won’t get hurt. Lifting weights is the only way to increase your strength and build some mass, but you’ll do more harm than good if you lift much more weight than your muscles can handle.
How heavy is too heavy?
If you can’t finish the set with good form, cut back on the weight.
2. Not stretching before and after a workout.
Don’t stretch your muscles by the time you get to the gym. Do it after heating. Stretching the muscles improves the range of motion of the joints. When muscle tissues are too tight, a small tear could occur if you force a joint to move through its full range of motion. Warming up and stretching can prevent this from happening.
3. Not warming up before and cooling down after a workout.
Stretching is not warming up. It is very important that you warm up before stretching. It is not a good idea to stretch before the muscles are warm enough. Rotate your joints (from your toes to your fingers) followed by at least five minutes of aerobic activity. For each weight-bearing exercise, perform one or two sets of exercises with a lighter weight to warm up your muscles.
4. Do not exercise within the target heart range.
To get the maximum benefits from cardiovascular exercise, you should exercise within your target heart zone three to four times per week. Exercising at this level promotes weight loss and burns fat. Reduces the risk of coronary heart disease, obesity, and other health-related effects. Doing cardio at least 3 times a week also helps lift your spirits. If you’re a beginner, start in a lower target heart zone (perhaps 50% of your maximum heart rate). As your fitness improves, exercise at a higher intensity of 60 to 90 percent of your maximum heart rate.
5. Running too far too soon.
Be moderate. Run too far and you can injure yourself and lose motivation. To gauge your fitness level, use X miles per minute instead of X miles per hour. A beginner will run 10 to 15 minutes per mile. A world class trained male athlete could run a mile in 6 minutes.