For runners, cyclists, and multisport athletes it is extremely common to develop human movement dysfunction as a result of training. The human body attempts to adapt to your training stimulus but often this training creates muscle imbalances. The muscle imbalance I am referring to is different than the traditional concept of muscle imbalance, when one muscle increases its strength when compared to its opposing muscle (e.g. quadriceps verses hamstring strength). The muscle imbalance will develop "tightness" in a group of muscles which in turn causes the opposing muscle group to "shut off" or to become "weaker". During training and competition, muscles are placed under repetitive stress. In an effort to adapt to this stress many muscles tend to "tighten" up. For example the hip flexors (i.e. rectus abdominis) accelerate hip flexion during running and cycling, because of the constant pattern of overuse the hip flexors become "tight". Not only does this create a loss of range of motion at the hip but this "tightness" creates a unique phenomenon in the body causing the hip extensors to be "shut off" or "weak". This is very common in distance athletes creating muscle imbalances often leading to overuse injuries throughout the body. As an athlete's hip flexors become increasingly "tight" the opposite muscle, gluteus maximus, has a difficult time trying to maximally fire to develop hip extension. Like two ropes pulling on each side of the pelvis, if one is pulling too much this will ultimately cause a shift in the athlete's pelvis leading to changes in static (i.e. standing) and dynamic posture (I.e. running or cycling posture). This posture change can lead to pain from the feet to the back to the neck.

The lower body muscles that commonly become "tight" are the back extensors, hip flexors, adductors, and portions of the hamstring and calf muscles. As a result of these "tight" muscles their opposing muscle groups become "weak" which includes the deep core musculature (i.e. transverse abdominis, internal obliques), gluteus maximus and medius, hip abductors, and anterior lower leg muscles. Experts call this dysfunction the "Lower Crossed Syndrome (LCS)", primarily referring to tight hip flexors causing "weak" gluts and tight low back muscles causing a "weak" core.

The negative effects of the LCS can be first reduced through increasing one's flexibility of the "tight" muscles. Participating in habitual stretching of the low back, hip flexors, adductors, hamstrings, and calf musculature will begin to restore function. A kneeling hip flexor stretch would be a great place to start. Second is to work on proper posture and to strengthen the "weak" muscles. Of particular importance is to strengthen the core, particularly the transverse abdominis and other trunk flexors. In addition the gluts need to be reactivated. One exercise that may help is the "bridge". Lying on your back with your knees bent and feet flat, tighten your core (pulling your belly button in) and squeezing your gluts, lift your hips off the ground until your hips are level with your knees and shoulders. Many variations of this exercise can be done. Squeezing a ball between your knees, lifting one leg off the ground at time, or for advanced work, place an exercise ball under your feet. By challenging your balance during this bridging exercise you develop strength in all directions. When combining flexibility for the "tight" and strengthening the "weak" you will be able to reduce you likelihood of overuse injuries and ultimately increase your performance.