Maintaining proper form is one of the many steps in order to perfectly perform a certain technique. Correct form in weight training improves strength, muscle tone, and maintaining a healthy weight. Proper form will prevent any strains or fractures.[6] When the exercise becomes difficult towards the end of a set, there is a temptation to cheat, i.e., to use poor form to recruit other muscle groups to assist the effort. Avoid heavy weight and keep the number of repetitions to a minimum. This may shift the effort to weaker muscles that cannot handle the weight. For example, the squat and the deadlift are used to exercise the largest muscles in the body—the leg and buttock muscles—so they require substantial weight. Beginners are tempted to round their back while performing these exercises. The relaxation of the spinal erectors which allows the lower back to round can cause shearing in the vertebrae of the lumbar spine, potentially damaging the spinal discs.
Of the three, protein will of course play the most important role in the muscle building process (like calories, it’s one our required “supplies”), although fat and carbs will still be important for other reasons which range from optimizing hormone production (e.g. testosterone, the muscle building hormone) to enhancing training performance and recovery.

In fact, in one new study comparing the effects of aerobic exercise versus resistance training on the psychological health of obese adolescents, researchers found that people in the resistance group experienced significantly greater self-esteem and perceived strength over four weeks. But what’s most interesting is that the feeling of getting stronger — rather than any measurable gains — was all it took to give them a boost.

McArdle’s disease is a myopathic disorder associated with fatigue and contractile dysfunction as a result of alterations in the release of glucose from glycogen (via defects in myophosphorylase enzyme function) resulting in an inability to conduct high intensity work as easily.[548] Creatine is thought to be therapeutic because beyond the general strength enhancing properties of creatine, people with McArdle’s disease have an upregulation of phosphofructokinase (PFK) enzyme activity [570] and increasing phosphocreatine storages suppresses the activity of this enzyme.[571]

Using too much weight, too soon; always start lower than your expected ability and work your way up that first workout. If your form suffers, you are swinging the weight, or using momentum, this indicates you may be using too much weight. Greater momentum increases the potential for injury and reduces the effectiveness to the muscle group being targeted.