Digital Track and Field’s free educational series of articles will provide important information for coaches on force development including training to improve initial force development and how to develop high rates of force.
Track and Field Events and Force Development
All sprinters and field event athletes require a combination of strength, speed and power. In the sprints, jumps and javelin speed and power should be the primary training focus and to a lesser extent muscular strength. In the circle throwing events strength, speed and power are all important elements of the training program. Higher levels of strength are required in the circle throwing events when compared to the other speed and power events.
|Track and Field Event||Time to Execute Final Phase|
|Sprint (max velocity)||.08 – .10 seconds|
|Long Jump||.11 – .12 seconds|
|Javelin||.16 – .18 seconds|
|Shot Put||.15 – .18 seconds|
|High Jump||.17 – .18 seconds|
3 Ways to Increase the Rate of Force Production
Faster muscle contractions (speed and power)
Stronger muscle contractions (strength and power)
Optimize the stretch shortening cycle (reactive strength)
Rate of Force Development
Force is the ability to accelerate mass characterized by magnitude and direction. How rapidly force can be developed is a combination of speed and resistance. The rate of force development is speed and strength of the muscle contractile tissue to contract which results in force.
Training focused on the speed of the muscle contraction and the force generated by the muscle contraction will improve the rate of force development. This accomplished by two training methods: training to develop faster muscle contractions and training to develop more powerful muscle contractions.
Maximum contraction speed and maximum contraction strength are on the opposite ends of the force-velocity spectrum.The ability to achieve maximal force and the greatest velocity with the same movement is not possible at the same time. Therefore, it is important to train elements of strength, speed and power (combining strength and speed) since high levels of force and velocity are both needed in track and field. Each event will have a different combination of force and velocity along the force-velocity continuum that is optimal to maximize performance.
Stretch Shortening Cycle and Muscles
The neuromuscular system must create a well-timed movement pattern maximizing muscle activation to develop the largest force in a short amount of time. The stretch shortening cycle is a mechanism that can be trained to improve this movement pattern.
The stretch shortening cycle is an active prestretch (eccentric contraction) of the muscles, followed by a delay (amortization phase), then a rapid shortening of the muscle (concentric contraction).
First, the muscles and tendons are stiffened and stabilized preparing the muscles for impact. Next, during the eccentric phase, the muscles are lengthened upon impact, then there is a slight delay or amortization. Finally, during the concentric phase, the muscles contract and are shortened to produce movement. If timed right, the force generated by the contraction is greater than the resting muscle contraction.
The muscles reaction to the prestretch is the elastic response. During the eccentric phase, the muscles lengthen, muscles can produce greater force when stretched just before a contraction by storing elastic energy that is converted during the concentric phase of movement resulting in greater force production. The force of the contraction is correlated to the length of the muscle during the eccentric phase just before contracting.
The connective tissue in tendons and to a lesser extent muscles can withstand extremely large loads of tension during the eccentric phase and have elasticity that store energy that is converted during the concentric phase to produce force. Energy is stored and recoiled in the muscles and tendons producing high levels of force. The elasticity of the muscles and tendons play important part in force application. Tendons primarily store the energy because tendons are stiffer which takes greater energy to stretch yielding a greater return when uncoiled. Muscles can easily stretch, however, if a muscle is activated force production can be greatly increased.
The length of time between the start of the eccentric contraction to the start of the and concentric phase of the muscle is called the amortization phase. The amortization phase should be optimized, with a short eccentric phase and a very rapid concentric phase.
In the long jump, the amortization phase occurs when the plant foot touches the board until the takeoff movement begins as the athlete’s body is displaced over the board.
The coupling time occurs when the joints in the body pause very briefly and switch from lengthening to shortening creating on isometric muscle contraction.
The active state is a period of time to develop force during the eccentric phase and amortization phase of the stretch shortening cycle. The active state produces more muscle activation engaging more cross bridges in the sarcomeres allowing more time for force to be developed and generate larger force outputs.
The stretch shortening cycle generates additional force during the concentric phase of the muscle contraction.
The Force-Length Relationship involves how muscle tension varies based different muscle lengths along with other variables including muscle fiber types, tendon components, tension potential and force output.
The Force-Time Relationship is the delay in muscle tension between the electrical signal to create tension to peak muscle tension. During the delay (active state), tension is built up. The length of time to develop tension depends on the muscle fiber type, movement requirements and effort (voluntary and involuntary). Training can shorten the delay which allows for quicker rate of force development speed.
Peak Force and Time
Peak force can be developed in as little as 100 milliseconds for explosive movements or over one second for maximal strength efforts.
Athletes want to minimize landing (eccentric) deceleration and maximize takeoff (concentric) acceleration.
Increasing the rate of force production and maximal force (to a certain level) will improve athletic performance in the speed and power events.
Since speed and power events occur so rapidly, the force required to execute the skill must be accomplished quickly. The time to reach maximal force production can take .3 seconds or longer on average during different motions, most track and field events take under .18 seconds to execute.
Speed is an important component for the rate of force development, however improvements in strength will also increase how fast a mass can be moved. Since strength can increase the force of the muscle contraction, careful attention is required to train this ability, but it should not be the main focus because the rate of force development is more critical than maximal force.