Training for Speed

The ability to reach maximum speed as quickly as possible from a stationary or partially moving posture is the definition of speed.  This is called acceleration.  The key is to hold that pace as long as possible and to minimize the slowing due to fatigue, friction and air resistance.  Muscles with a high percentage of fast twitch fibers exert quicker, more powerful contractions.  Individuals born with a higher percentage of fast twitch fibers in the muscles involved in sprinting have a higher speed potential than those born with a preponderance of slow-twitch fiber which is more suitable for cross country, marathon running and other sports requiring high aerobic endurance.  Inherited percentages of fiber type are similar in both men and women.  Although the theory that slow-twitch fibers can be changed into fast twitch fibers in controversial, new evidence suggests that prolonged high-intensity training may produce that effect and improve the ratio of fast twitch to slow twitch fibers.  The right kind of high intensity (heavy load) will recruit and train the fast twitch fibers and aid in the improvement of acceleration and speed.  It is the intensity (load) not speed that activates fast-twitch muscle fibers.  Postural muscles such as the soleus are composed mostly of slow twitch fibers whereas large locomotion muscles such as the quadriceps contain a mixture of both fiber types, which permits both jogging, a low power output activity, and sprinting, a high power output activity.  Body fat is important in speed.  6-10% for men and 12-17% for women is desirable.  Excess body fat can negatively affect both acceleration and speed.  Muscle balance can affect speed.  The prime movers in sprinting are the knee extensors, hip extensors and ankle plantar flexors.  Comparing the strength and power of left limbs to right limbs, agonists to antagonists, upper body to lower body and strength to total body weight provided valuable information and imbalance usually exists between the knee extensors and the flexors.  An even greater imbalance is often found between the posterior leg compartment muscles (plantar flexors) and the anterior compartment muscles (dorsi flexors).  A strength imbalance between two opposing muscle groups, such as the quadriceps (agonists) and the hamstring (antagonists) also produce serious limitations.  The strength of the hamstring muscle group is a sprinters weakest link.  It should be improved to 70-90 percent of the strength of the quadriceps groups.  A minimum of 70 percent is recommended for the prevention of injury.  Ideally, leg extension and leg curl scores should be the same.

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