What Does Running Sprints Do for Your Body?
Sprinting is controlled anaerobically, or without the use of oxygen. Unlike aerobic training, anaerobic exercise relies predominantly on the metabolic chemicals for energy. This form of training has a number of beneficial adaptations to the human body. Many of these adaptations are in direct contrast to those associated with aerobic training, while others occur in both methods.
Sprinting requires the application of speed and power over short distances. Among the initial adaptations to running sprints are those in the central nervous system. The body responds to the increased demand for power by recruiting more motor units, increasing the firing rate and improving the timing of motor unit responses during high-speed muscular contractions. Many of these responses occur within the brain and are then transmitted through the spinal cord and to the muscles through muscle spindles and the Golgi tendon organs.
Sprinting promotes the development of type II muscular fibers, or those that are responsible for quick, powerful muscle contractions. Distance runners, on the other hand, tend to develop more type I fibers -- which do not contract with the same force as type II fibers, but fatigue less quickly. Sprinting also promotes more hypertrophy, or increases in the size of the muscle fiber, in the muscles in the legs.
Connective Tissue Adaptations
Both sprinting and distance running provide benefits to bones and tissues. Like muscles, bones respond to overload by increasing in size and density. The hypertrophy that occurs with sprinting also increases force exerted on the bones. The bones respond by increasing in mass to help provide support and structure to the muscles. Tendons, ligaments, fascia and cartilage all increase in size and help absorb the shock of muscle forces as a result of sprinting.
One of the more overlooked aspects of training is the effects on hormones. Short-term, high-intensity training such as sprinting promotes increases in testosterone, insulin, insulin-like growth factors and growth hormone. Elevated levels of these hormones eventually result in increased muscular size and strength gains, and subsequently allow the body to exert more force and effort during workouts.
Short-term cardiorespiratory effects from sprinting include increased cardiac output, stroke volume, heart rate, oxygen uptake, systolic blood pressure and blood flow to muscles. Long-term effects from anaerobic training are not as prevalent as those in aerobic training, although sprinting helps promote increased anaerobic power, or the ability to produce power without the use of oxygen.
- Essentials of Straining Training and Conditioning (3rd Ed.); Thomas R. Baechle and Roger W. Earle
- Physiology of Sports and Exercise (3rd Ed.); Jack H. Wilmore and David L. Costill
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