The duration of a sprint activity is normally no longer than two to three minutes (i.e., ≤ 200-meter swim, 800-meter run, one-kilometer bicycling time trial, or 1500-meter speed skating trial), and sprinting relies heavily on energy produced from the ATP-PC system Anaerobic Glycolysis. The underlying concept of speed as it pertains to the athletic population is sprinting. Can you name a sport that solely involves speed in a straight line from start to finish? Obviously, track sprinters come to mind. Beyond that, there isn’t much that directly relate. The exception might be baseball and softball players running to first base.
A.) LINEAR SPEED
i.e., Starting out of the block greatly depends on the athlete’s muscular strength and they can get up to nearly 1/3 of their top speed. At this point, it is the greatest force in acceleration. The biomechanical constructs underlying sprinting in the acceleration phase have the body tilted forward to direct ground reaction forces more horizontally. During this initial phase a shin angle of 45 degrees with a forward leaning torso will occur. Arm swing plays a vital role in the acceleration phase and subsequent phases of sprinting in stabilizing the torso and creating vertical propulsion. Arm swing serves to counterbalance the rotational momentum created by the leg swing.
By steps 10-12 the athlete is at 80-85% of their top speed. During the max velocity maintenance phase of a sprint, once they get rolling the force on the ground, is applying that force at the time available. The force in the ground becomes a motion- based mechanism where the athlete forces their limbs as a “punch” into the ground. Typically, at top speed, an athlete’s force into the ground peaks at 3- 5x their body weight. Ground contact time is determined by 3 main factors:
- The ability to apply force to the ground very quickly (power).
- The stiffness of the leg at the moment of foot strike (a stiffer leg can capture more “free” energy from the ground and then reuse it).
- Biomechanical characteristics such as the position of the foot in relation to the center of gravity at foot strike (a foot that lands in front of the body’s center of gravity acts as a brake and thus increases ground contact time)
B.) MULTI-DIRECTIONAL SPEED
Most athletic competitions require multi-directional movements and skills. In order to perform better, actions performed laterally, backward and forward are dependent upon the unpredictability of an opponent or the need to reposition yourself to complete a required task. Sport specific situations in field sports are complex and dynamic in terms of movement. The kinetic chain is required to accelerate, decelerate, and execute while reacting to stimuli and mentally processing predetermined patterns. Agility and change of direction have the common component of decision making. Decision making can be predetermined as in change of direction or reactive to stimuli in accordance to the definition of agility.
The underlying biomechanical components of these entities have a connection to the concept of speed as well as an interdependent connection. Agility, which comprises a rapid whole-body movement with a change of velocity or direction in a response to a stimulus has a connection to velocity. The connection to velocity can be either an increase or decrease in speed. The increase in velocity is predicated upon acceleration of the kinetic chain.
A second component associated with agility and change of direction is deceleration. Deceleration is not a prevalent component of in-line sprinting as these sports allow for the kinetic chain to slow down (decelerate) gradually. Whereas in court and field sports deceleration occurs very rapidly. Deceleration in terms of agility and change of direction typically occurs at a very rapid rate with a change of direction and reacceleration to be occurring immediately thereafter. Proper joint angles, leg kinematics, and muscle tension is imperative in deceleration and the resistance of forward momentum. A shortened gait cycle occurs in this process to absorb eccentric forces, ground contact of the landing leg occurs ahead of body’s center of mass differing this component from acceleration and ground contact occurs with dorsiflexion of the ankle and entire foot as the heel creates a braking action.
A final component associated with agility and change of direction is the transition from deceleration to re-acceleration and (position) of the trunk. Controlling the trunk in deceleration and reorientation of the trunk with a change in vector allows for a much more effective re-acceleration. After completion of deceleration, a reorientation of the body’s center of gravity and upper extremities will be required to accelerate with the appropriate body lean in the new intended direction. A low center of mass assists in this process allowing for center of gravity to be directed effectively. Arm action in both deceleration, reorientation, and into reacceleration should be powerful to facilitate leg drive.