Force Production In Track and Field
Track and field performance relies on applying maximum force from optimal positions. The dynamic movements require stable posture while being acted upon by outside forces. Stability requires a low center of mass within the horizontal base of support.
Efficient dynamic movements direct force through the center of mass during displacement; otherwise, rotational imbalances can disturb stability. The maximum force is generated when all available joints are activated during movement. Movement should start with large muscles and proximal joints that can overcome inertia more effectively. Ending a skill with smaller muscles and distal joints requires fine motor movements that contribute to the finishing velocity.
Technical movements in track and field have overlapping actions with an efficient well-timed motion from stable positions to maximize performance.
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 in track and field can take .3 seconds or longer during different motions; most field events take under .18 seconds to execute (Zatsiorsky & Kraemer, 2006). Therefore, maximal force over a long duration is not as beneficial as early rates of force development under 250 milliseconds.
|Long Jump||.10–.12 seconds|
|Shot Put||.15–.18 seconds|
|High Jump||.17–.18 seconds|
Sprinting and Force Production
All sprinters and field event athletes require a combination of strength, speed, and technique. In the sprints, jumps, and javelin, the rate of force development should be the primary training focus and, to a lesser extent, maximal force. According to Bosch (2015), explosive events, like sprinting, “seek to improve the ratio between force production and speed of muscle action (force times speed of muscle action = power)” (p. 63).
The block start and acceleration phase of a race propels the athlete forward and upward. Forces are generated horizontally (forward) toward the finish line and vertically (upward) to counteract gravity.
Acceleration training is closely associated with horizontal force development, whereas maximum velocity training is associated with vertical force development.
Sprinters transition from more horizontal and less vertical to a more vertical extension during the later phases of the sprint movement. Horizontal forces create greater acceleration during the start of the race to overcome inertia. Vertical forces are more prevalent during the later stages of the short sprint races; runners generate large ground forces that direct the athlete forward and upward.
According to Bosch (2015), explosive events, such as sprinting, “seek to improve the ratio between force production and speed of muscle action (force times speed of muscle action = power)” (p. 63).
Sprinting and Opposing Forces
The motor patterns in sprint mechanics require rapid muscle contractions that produce high levels of force during the cyclical motion of sprinting. The running movement is a repetitive action combining opposing forces, including intensity/relaxation, extension/flexion, speed/strength, and action/reaction of ground forces.
Speed development trains muscular coordination. Intramuscular coordination develops the neuromuscular system by increasing motor neurons' firing rate and frequency for greater force production in track and field's speed and power events. Intermuscular coordination improves the technical properties of running mechanics, allowing more cooperation between agonist and antagonist muscles.
Throwing and Force Production
In the circle, throwing events, strength, speed, and technique 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. In the shot put, discus and hammer, increasing the rate of force production and maximum muscle contraction force will improve athletic performance.
In the throwing events, a long pull on the implement is important, applying force over a long period. “There is a significant correlation between the distance of force application (pull) and the throwing distance. A larger distance of force application will result in a longer path of acceleration, leading to a higher release velocity” (Liebenberg, Zelezny, Ihalainen & Bartonietz, 2016, p. 59).
In the throwing events, when implements of different mass are thrown, the force production changes. Less force is required with lighter implements, but greater acceleration speed is possible. With heavier implements, more force is required to accelerate the object, even though acceleration is not as rapid. Heavier implements require high levels of force production but produce lower velocity levels when compared to the standard weight implement.
The shot put requires near maximal force and high rates of force development for maximum performance. Training for the shot put often requires a more balanced approach concerning the rate of force development and maximal force outputs.
Jumping and Force Production
Another important factor is how much force is rapidly applied over a distance. In the long jump, for example, during the takeoff, the jumper applies force rapidly as the body moves past the takeoff leg, displacing the body forward and upward; applying force into the ground over a large distance but quickly (approximately 100 milliseconds) will maximize jumping distance.
Plyometrics and Force
Plyometrics not only improves the rate of force production and maximal force, but it is also used as skill-specific development in many track and field events, especially the sprints, jumps and throws.
Plyometric exercises can have horizontal or vertical components. Horizontal movements improve acceleration, long jumping, triple jumping, discus throwing, shot putting, and javelin throwing. Vertical movements improve maximal velocity, high jumping, and pole vaulting. Complex exercises can combine both horizontal and vertical movements to improve force production in track and field
Mechanisms of Force Production
Force is the ability to accelerate mass characterized by magnitude and direction. Force developed within the body is known as internal force. The force between an athlete and an outside influence, such as an object, is an external force.
The force generated during a muscle contraction depends on two main factors; motor unit activation and muscle structure. Maximal force is achieved when the highest number of motor neurons are recruited along with the firing rates at a high frequency with synchronized activity. The contractile properties of the muscle, the arrangement of muscle fibers, the type of muscle fibers, and the attachment location of muscles all influence contraction strength and force production (Enoka, 2015).
Types of Force Generation
There are two ways to increase force in muscle contraction; increase the rate of force production or increase maximal force output. The time available for force development is an extremely important factor to consider when selecting training elements in a program. In most sports skills, the time to produce maximal force is greater than the time available to execute the final movement; therefore, the rate of force development is more important than maximal force.
Rate of Force Development
Since the sports movements occur so rapidly, the force required to execute the skill must be accomplished quickly. Resistance determines the acceleration; greater acceleration is possible with lighter resistance. However, it is difficult to exert high levels of force in very fast movements if resistance is too low.
How rapidly force can be developed is a combination of speed and resistance.
Maximum contraction speed and maximum contraction strength are on the opposite ends of the force-velocity spectrum. The ability to achieve maximal force and maximal velocity cannot be achieved at the same time during a single movement. Therefore, it is important to train elements with velocity and resistance.
The force/velocity curve is based on the inverse relationship between force and velocity. As force (resistance) increases, velocity decreases; velocity can be increased with less resistance, but less force is generated.
Maximal Force Production
Maximal force production is the greatest force a muscle or group of muscles can produce independent of time. The amount of resistance used in an exercise determines the training response. Maximal force output is attained by training with heavy resistance at lower velocities. Zatsiorsky and Kraemer (2006), stated: “motion velocity decreases as external resistance (load) increases” (p. 29).
Speed is an important component of the rate of force development; however, improvements in strength will also increase how fast 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 focus because the rate of force development is more critical than maximal force.
Force and Time
According to Zatsiorsky and Kraemer (2006), “maximum force is attained when velocity is small; inversely, maximum velocity is attained when external resistance is close to zero (p.29).
Movements that have too little resistance cannot generate high levels of force, and movements that have too much resistance will generate high levels of force but too slowly to be effective. The ideal training movements develop the optimal amount of force by combining resistance and speed. Each track and field event will have a different optimal combination of resistance and speed.
Force Production and Impulse
Although maximal force generation is independent of time, speed should be a major consideration when training with heavy loads. Focusing on the impulse (force times time) in high intensity resistance exercises will have a greater transfer of training effect than maximal force development independent of time.
Increasing the ability to generate greater force in a short time will increase the impulse. Impulse is the most relevant rate of force development measure in dynamic functional activities (Maffiuletti, et al. 2016).
When training with maximum loads, the force application against resistance should be performed as quickly as possible while maintaining technique (Bompa, 2015).
In addition to the amount of force, “equally important is the time of force application. Impulse = change in momentum = average force times time during which force acts” (Liebenberg, Zelezny, Ihalainen & Bartonietz, 2016, p. 59).
The greatest impulse is generated by large forces applied over a long distance in a short period of time.
Neural Factors and Force Production
The nervous system coordinates the body’s movements along with the muscles. Thus, the nervous system components are in control of muscle activity and force production in track and field events. Neural factors related to speed development include the recruitment and firing rate of motor units (intramuscular coordination), intermuscular coordination, and reflex innervation. The distribution of muscle fiber types, muscle cross-sections, elasticity, muscle length, and energy within muscle cells will determine force production (Stein & Elliott, 1998).
Changes in the frequency of motor unit activation and the number of motor units engaged will determine force production.
The article "Muscles and Nervous System: Keeping the Body Moving" (Glicksman, 2016) compares the nervous system to a military operation, stating:
The nervous system is organized like a military operation in that a general and his staff must receive information from the reconnaissance team about where the enemy is located and what it is doing. This information is used by headquarters to help make decisions about strategy and to formulate the orders being sent out to the troops. But things don’t end there. Headquarters has to constantly be kept informed of what is going on in the field so it can adjust to an ever-changing situation.
Similarly, the body’s nervous system is divided into the central and peripheral nervous systems. The peripheral nerves have sensory neurons bundled within them that send information about what is going on inside and outside the body to headquarters. They also have motor neurons bundled within them, which take the orders from headquarters and tell the muscles what to do. The central nervous system, consisting of the brain and the spinal cord, is the headquarters where the sensory information is received, analyzed, and compared with other information. Then orders are sent out to perform coordinated actions that are purposeful, and goal directed.
In general, the spinal cord organizes the sensory messages that it receives from the peripheral nerves and sends them to the brain. It also organizes the motor messages from the brain and sends them to the various regions of the body by way of the peripheral nerves.
Summation of Forces
Summation of forces is a specific pattern of body movements with optimal timing when combined will generate ideal force. The sequence of force production in track and field events begins with movements from larger, slower proximal muscle groups and finishes with smaller, faster distal muscle groups. Peak force reached at the optimal time requires synchronization.
The techniques used in track and field are designed to maximize force by combining different movement patterns into an efficient complex skill which optimizes the summation of forces. The continuous flow of movement creates a summation of forces by adding all the body systems together, resulting in larger force production during the complex skill.
Throwing and Summation of Forces
In the throwing events, kinetic energy is generated by elasticity from a large mass to a smaller mass. The larger mass of the legs and torso will generate speed into the smaller mass of the arm and hand; the larger mass will accelerate, creating greater speed through the hand, resulting in maximum release velocity. The release velocity is a result of the summation of forces during the technical execution of the throw.
Release speed is developed in the throwing events by using event specific speed training and explosive movements focusing on a high rate of force development.
Force Development and Strength
“One may argue that the rate of force development is as important as, or more important than, maximum force production (i.e., maximum strength). Thus, rate of force development is an important characteristic to measure” (Stone, Stone & Sands, 2009, p. 170).
The Science and Practice of Strength Training states, “to enhance rate of force development, exercises with maximally fast burst of muscle action against high loads are used” (Zatsiorsky & Kraemer, 2006, p. 157). Using high levels of resistance will require less velocity, but the rate of force production is near maximal because the movement is performed as fast as possible.
Power production requires high resistance exercises that facilitate the rate of production. Training to improve the ratio between force production and the speed of muscle actions are important to develop power (Bosch, 2015).
Specific strength training can improve individual aspects of the complex technical requirements in track and field. Creating a link between the force produced by the muscle fibers and the exercise movement will result in greater transfer to the competition event. Force can be accelerated to exert the highest rate of force production at the right time in a movement. Bosch (2015) stated the “optimal adaptation occurs in the part of the force/velocity curve that is relevant to the sporting movement” (p.185).
Using explosive efforts and maximal efforts that require high rates of force in minimal time will produce force at a faster rate and have a greater transfer effect for competition events.
Event Specific Training and Force
Body positions change during the execution of a technique. Muscles produce counterbalance movements in different directions to execute a skill correctly. The changes in position can impact the magnitude of force an athlete can produce.
It is important to mindful of the rhythm and timing of the competition movement when executing exercises for event specific maximal force or event specific rate of force production in track and field events and training.
Lower velocity event specific training can develop the strength that is directly applicable to the competition event. Event specific movements with higher rates of force production will improve the precise speed qualities needed for an event.
Rate of Force and Performance
The rate of force production in track and field events improvements as a result of training power (speed and strength). Direct links to performance improvements in the speed and power events in track and field have been correlated to the rate of force development (Maffiuletti et al. 2016).
According to Verkhoshansky and Verkhoshansky (2011), “the capacity to express power produced by the speed of movements and by the force of overcoming external resistance” will improve performance (p. 29).
Generating peak levels of force in less time will improve power output in explosive efforts. Resistance training is a known method to increase the rate of force development in elite athletes.
Training speed (reactive strength), a combination of speed and strength (power), and strength (maximal strength) will improve force development. All three methods are beneficial for speed and power athletes, but each track and field event will have different requirements.
Each event will have a different combination of force and velocity along the force-velocity continuum that is optimal to maximize performance. Finding the right blend of the three methods for force production in specific track and field events within each training cycle will depend on the event requirements and athlete-specific needs.
Bosch (2015) stated, “the greater the speed of muscle action, the less force the muscle fiber can produce” (p.185). Understanding that lower weight moved quickly will improve velocity and lifting heavier weights will result in a greater force that will help coaches design a proper training system for optimal force development.
Olympic lifting exercises can facilitate the rate of force production and maximal force. Lighter resistance at 30-50% will improve the rate of force development, while heavy resistance over 85% will increase the ability to generate maximal force. Olympic lifting movements performed at 70-80% can increase the rate of force production while generating high levels of force output.
Potentiation and Force Production
Warm-up protocols including the use of Post-activation Potentiation (PAP), found increases in muscle temperature improved the rate of force development, and increased velocity in the muscle fibers (Coop, 2010).
Training activities before the competition movements that include sport-specific drills, strength training, and other types of warm-up activities can increase performance if fatigue does not occur.
PAP is described as “the phenomenon of acutely enhanced motor performance induced by preliminary performed muscular efforts at maximal or near-maximal intensity” (Issurin & Thome, 2019, p. 367). PAP provides a preloaded stimulus, a recovery period followed by the execution of the primary activity.
Elite sprinters have shown an increase in speed by performing strength training before competition. Studies on elite sprinters using high intensity squats with low repetitions (1-4) with 3–5-minute recovery between sets and 12-20 minutes of recovery before the competition movement improved speed in shorter sprint races (Coop, 2010).
Speed and power track and field events performance relies on applying maximum force from optimal positions. The dynamic movements require a stable posture while being acted upon by outside forces. Stability requires a low center of mass within the horizontal base of support. For the speed and power track and field events, the technical movements have overlapping actions with an efficient well-timed motion from stable positions to maximize performance.
Combining exercises into a complex can activate more muscle fibers and take advantage of the stretch shortening cycle mechanisms. Based on numerous studies cited by Stone, Stone, and Sands, an intense lifting exercise followed by an explosive exercise that involves the stretch shortening cycle can maximize muscle activation and generate more force (Stone, Stone & Sands, 2009).
Track and Field and Force Production Review
The amount of force and how quickly it is developed are two important in speed and power. For the speed and power track and field events, maximal force production that are over a long duration is not as beneficial as early rates of force development under 250 milliseconds.
Event specific exercises, strength development and speed training can improve the rate of force development and maximal force. The timing and purpose of the movements must be considered before implementing any type of exercise into a program.