Logically, leg muscles appear to be the most important muscle in any sort of running. However, they cannot function to the greatest extent without equal strength in the upper body and lower body. Balancing of muscles, buildup of lactic acid, and a strong core can all combine to drastically improve speed and running form.
In the late 1990s, the majority of olympic sprinters neglected the importance of upper body strength. Only a select few athletes including gold medalist, Linford Christie, added full body circuit work into their conditioning. Upper body buildup is immeasurably beneficial, at a certain level, there can be little to no improvements once form is perfected. Optimizing biomechanics is the next level in improvement and upper and lower body strength must be balanced in order to maintain terminal velocity. In a Runner’s World Article, Jonathon Beverly stated, “The body is all connected and balanced on top of itself…If you throw off that balance at the top, the supporting structures need to work harder to keep your body upright before they begin the task of pushing you forward”. The benefits of upper body strength in sprinting allows not only a satisfactory body but longer endurance in form preservation.
In longer sprint-events the final stretch of the race relies on the maintenance of form for a greater margin. In the homestretch of a 400m race, lactic acid builds up through the entire body and can be a major issue in gradual deceleration. If the lower body can control and resist the lactic acid but the upper body cannot, balance is broken and form deteriorates. Without core strength or back strength, the upper torso will either gain a forward lean or backward lean. Forward lean can result in a reduction of force towards the ground causing the athlete to drop relaxation of the muscles and lose overall speed. The most important portion of the race relies merely on the strength and conditioning of the athlete in all portions of the body. Sprinting requires strength in nearly every area and aspect of the body.