Running, on the other hand, is more of a ballistic action with the body continually launching its weight from one leg to the other. The speed at which someone runs is directly linked to the stride frequency to stride length relationship. For example, when comparing novice to elite sprinters, studies have shown that elite sprinters achieve greater stride length and can increase it further up to about 45m from a static start of a race. Compare this to novice sprinters who peak their stride length around the 25m mark of a race from a static start.
When comparing novice to elite stride frequency, elite sprinters can achieve faster slightly higher frequencies (~5/second) and maintain that pace for a longer period of time compared to novices. When you think about the mechanics behind sprinting, it is easy to understand that a sprinter that has a high turnover stride (stride frequency) and is pushing off for more power (stride length) will elicit a greater speed.
One thing to understand, however, is that due to varying leg lengths amongst different individuals, stride length is difficult at times to train. Stride frequency, however, can be trained effectively to increase running speed.
Sprinting Performance and Stride Analysis
Below is a summarized list of the major muscular requirements during sprinting:
1. As the back (recovery) leg swings forward, eccentric knee flexion controls its forward momentum, prepares it for an efficient foot strike.
2. Muscle action then shifts from eccentric to concentric action and continues to the support phase (leg beneath center of gravity) which transfers power to the leg.
3. During the ground support phase, the high joint angle at the planted foot allows for stored elastic energy. Eccentric knee extensor activity also allows the quads to store and recover elastic energy.
4. There is a triple extension from the ankle, knee, and hip all at once allowing for propulsion and drive forward.
To maximize sprinting speed, I have listed a few training goals below that can help in running efficiency:
Minimize Braking - By aiming to plant the supporting foot directly beneath the center of gravity and maximizing the backward velocity of that leg during the propulsion phase will minimize the braking effect of forward momentum.
Fast Foot Strike - By increasing stride frequency and backward propulsion, you minimize the amount of time the foot has contact with the ground, therefore minimizing the braking effect of forward momentum.
Strengthen the Hamstrings - Eccentric knee flexor strength is the most important aspect limiting recovery of the leg as it swings forward.