Performing too many isolation exercises and not enough compound exercises. Compound exercises are defined as those that work more than one muscle group, while isolation exercises work only one muscle group. For example, a biceps curl works only the biceps, making it an isolation exercises. Squats are a compound exercise, since the work the quadriceps and the glutes. Both types of exercises have valid purposes. However, focusing primarily on isolation exercises can mean a greater number of total exercises in order to work each muscle group, making for a long and tedious workout. This can lead to an overworked body and a burned out exerciser.
Using a weight that is too light. Making this mistake will result in not providing the body with enough of a challenge to see steady progress. Using weights that are heavy enough so you can only perform 15 or fewer repetitions will adequately work all your muscle fibers and give you results that show. Your body may be capable of lifting more weight than you realize. Increase the weight you use often, using a great deal of caution to maintain proper form at all times.
Not using a full range of motion. I once observed a young woman in the gym squatting with a barbell on her shoulders. On each repetition she only lowered her body three to four inches toward the floor. Chances are, the barbell was too heavy for her. Had she decreased the weight and lowered her body in each squat until her thighs were parallel to the floor she would have better hit her lower body muscles and seen greater progress. A poor range of motion is often see exercises such as bench press and bicep curls, where people tend to use too much weight to complete the entire movement. While using the heaviest weight you safely can is beneficial, if the weight prevents you from completing the entire movement you will be denying yourself maximum results.
Take some time to review your workouts and see if you are making any of these common strength training mistakes. By avoiding these mistakes you can save yourself time and have results that others will notice.