Being sensible when it comes to your workout is key to avoiding many common problems associated with exercise. Overtraining or underusing muscles can wreak havoc on the body, weakening the immune system and leaving you feeling fatigued and out of sorts.Key ways to avoid difficulties are to start out slowly and to build strength, stamina and endurance gradually. It is also important to vary your routine to include activities that work all muscle groups.Strength imbalances, muscle strains, and wear and tear on the joints can result from following the same movement pattern over and over again and using the muscles unevenly. For example, your right arm may be much stronger than your left. As a result, with certain exercises, the stronger limb continues to work harder, putting it at risk for injury, while the weaker limb stays weaker.Strength imbalances can occur between the upper and lower body, the right and left sides, or frontal muscles and posterior muscles. We put more weight on one leg when standing and push to a greater degree of force with one leg than the other while walking, climbing stairs or using cardio equipment.For a day, pay attention to your patterns of movement and body positioning, and when possible, vary them. Muscle co-contractions, or involuntary tightness, occur when we are under physical or emotional stress, so counteract these with movements that are opposite in nature.Work these muscles together to avoid imbalances:Abdominals and lower back: Most people work the abs but forget to give equal time to strengthening the lower back muscles. The abs and lower back work together to help support your spinal column and provide a strong base from which movements can be performed in a safer and more natural manner.Calf muscles and anterior lower leg muscles: The calves are typically strong muscles, activated with each step you take and bearing a significant amount of your body weight. Many people insist on overworking the calves with heel raises and other exercises in an attempt to increase their size. With overtraining comes Achilles tendon problems, tightness, cramping, inflexibility and increased risk of injury.The anterior lower leg muscles are used to a lesser degree. So, to avoid shin splints, condition them properly as well as stretching after exercise, and above all, avoid doing too much too soon or switching from one activity to another without easing into it. Suddenly going from walking or running on a flat surface to walking up hills, for example, or increasing the incline on a treadmill too drastically can result in shin splints.Stronger quadriceps (front thigh), hip flexors and weaker hamstrings (back of the thigh), glutes: Be sure to incorporate as many exercises to target the hamstrings, hip and buttocks as you do to work the frontal thigh muscles.