The Biomechanics of Sprinting
Understanding the biomechanics of sprint running form is essential to successful sprint performance. Biomechanical variables influencing sprinting include reaction time, technique, force production, neural factors, and muscle structure. The electrical activity produced by skeletal muscles also influences sprinting. Thomas (2017) found that maximal running speeds in sprint events are achieved by creating a high force output, which means creating a high vertical ground reaction force over short contact times. Type II muscle fibers in the leg muscles and a heavy reliance on anaerobic metabolism also contribute to max running speeds.
An athlete’s ability to react to the sound of the starter’s gun and push their feet and legs from the starting block, is essential to a sprint performance. This is the time from hearing “go” until the onset of electrical activity and then force production by the muscle. The faster this electrical activity begins in every muscle, the better the neuromuscular performance contributing to overall performance.
Reaction time is highly genetic but can typically improve, as it is derived from stimulation and adrenaline. Mental training and focus, as well as overspeed training, have resulted in reaction time improvements in some athletes.
The production of force varies by muscle and the time in which that muscle is activated within the duration of your sprint. For example, your gluteus maximus reaches peak power output and electrical activity within the first 100 milliseconds at the start phase and decreases in activity throughout the rest of the sprint.
The joint and muscle activity occurring in your leg during the start of a sprint show improved performance enhancement of elite sprinters compared with beginners. Elite sprinters exert greater force production at the start of their race as compared to less skilled sprinters.
Technique is a sprinter’s ability to accelerate by increasing stride length and stride rate after the initial start phase of a race. High muscle electric activity during the acceleration phase implies that a sprinter may reach their maximum neural activity during the acceleration phase, and subsequently declines.
A sprint run requires a complex sequence of continued muscle activation through the entire body, and a sprinter’s ability to perfect their technique through training will enhance performance.
The central nervous system regulates muscle force by changing the number of available motor units. Additionally, the motoneuron firing rates impact force production. This is where we get into slow (type I) and fast (type II) muscle fibers and motor units, relating to their contraction time and fatigue resistance. The force for contraction on muscle fibers during a sprint occurs over a very short period. Continued sprint training will increase your fast twitch fibers, enhancing performance.
Related Article: Agility & Weightlifting for Sprinters
A sprinter eventually reaches the constant phase of their sprint in which you’re not beginning to incline, accelerate, or decline in speed at the end of the race. A sprinter can reach their supramaximal speed due to factors such as tailwind or sprinting on a downhill.
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Thompson, M.A. (2017). Physiological and Biomechanical Mechanisms of Distance
Specific Human Running Performance.” Integrative and Comparative Biology, 57, 2, 293–300.