Who is a better athlete - your average body-builder or Michael Jordan? Many people can lift heavy objects, but they are not good athletes. Why? Because they lack speed, power or the ability to change direction on a dime.
Having power means an athlete can generate maximum strength in the shortest period of time. An athlete can be exceptionally strong, but lack significant explosive power if they are unable to apply their strength rapidly. Thus, athletes and strength/conditioning coaches should have a basic understanding of the relationship between the force of movement and the velocity of movement.
The Force-Velocity Relationship
Traditional strength training focuses on absolute force and motion, but does not influence the speed of force generation. In contrast, power training aims to reduce the time it takes to apply a set amount of force. This relationship between force and velocity and its effect on power explains why an athlete can be exceptionally strong, but lack significant power if they are unable to apply much of their strength over a short period of time. Think of a strong but slow, lumbering person and compare them to a cat-like, quick person. Who is the better athlete?
Power is related to force and time by this formula:
Similar to fine-motor-control training, the ideal force for generating power is when load is at approximately 30 percent of a one-repetition maximum (1-RM).1-3 Thus, the goal of power training is to increase the rate of force production. The main method to achieve this is plyometrics. Plyometric drills are both quick and powerful. They use a pre-stretch that involves the stretch-shortening cycle.4 Plyometric exercises usually involve jumping or upper-body drills using medicine balls and sometimes a rebounder.
The essence of plyometrics is that it involves exercise with the time spent on the ground minimized and the distance jumped maximized. This involves training both shock-absorption ability upon landing and spring or elastic recoil ability when jumping. If slow, static movements are emphasized, then dynamic stability, ability to change direction, and speed will not improve.
A myth about plyometrics is that the exercises are dangerous. The image of a person performing box squats and letting the knees pass forward of the toes during high-impact training has given all of plyometrics a bad name. However, if proper technique is emphasized and load remains low, plyometrics offers an unparalleled way to train the motor system to simultaneously enhance joint stability and power. This has been demonstrated in the rehabilitation of athletes following ACL injury.5
To absorb shock requires the skill of deceleration. To be able to spring requires the ability to change direction. Plyometrics is generally thought of as jumping or bounding training. The concept can be applied to agility work as well. Lateral running exercises such as the 20-yard shuttle drill or three-cone drill require tremendous power. In the 20-yard shuttle, an individual comes to a complete stop and changes directions twice while accelerating maximally between stops. This timed test is a functional power drill. The three-cone drill requires a smoother deceleration and control of one's center of mass (i.e., dynamic balance) combined with rapid acceleration. In both cases, deceleration, acceleration and change of direction are emphasized, making these ideal functional training exercises for sport.
Agility Tests and Training
According to Balyi, a key time for motor development for children is between the ages of 9 and 12.6-7 At this time, children are developmentally ready to acquire general overall sports skills that are the basis for healthy athletic development. This is the biological time before the maximum growth spurt during which there is a window of accelerated adaptation to motor coordination. This occurs within a chronological range, but is tied to the biological onset of the peak growth spurt, not an actual fixed age.3 Athletic excellence requires approximately 10 years of purposeful physical, mental and emotional training during this time frame.8 Knowledge of this can help in creating programs that avoid both emotional burnout and physical overuse injuries.
During this key period, a 75 percent training to 25 percent competition ratio is recommended.6-7 The ABCs of agility, balance, coordination and speed are emphasized in the training. As a child's growth spurt slows down, the ratio of training to competition can shift from 75:25 to 60:40.
In order to establish baselines for the functional development of the athlete, we can use a number of tests similar those used in the National Football League. These tests give the youth athlete, weekend warrior or elite athlete a yardstick by which to measure themselves and a goal for which to shoot. Tests include the vertical leap, broad jump, 20-yard shuttle and three-cone drill. Here are the fundamentals of the latter two:
- Place two objects 10 yards apart.
- Start at the midpoint (bottom of figure) with your feet and body facing straight ahead, so objects are to your left and right.
- At the whistle, simply turn, cross over, and sprint toward one side or the other, touching the ground at the object (5 yards).
- Turn and sprint to the opposite end line (10 yards).
- Finish by turning and sprinting across your original starting position (5 yards).
Tips: Stay low in the first 5 yards, decelerate completely at each line, keep your feet under your body and finish hard through the line.
- Set up three cones in a triangle with each cone 5 yards apart.
- Start in a ready position at the first cone.
- When the whistle blows, sprint 5 yards ahead to cone 2 and touch it.
- Run back to cone 1 and touch it.
- Run around the outside of cone 2 to cone 3 and run around it from the inside.
- Run around the outside of cone 2 and through the finish line at cone 1.
Tips: Stay low, decelerate at cones, utilize small, quick steps to navigate around cones, and finish hard through the line.
References
- Garhammer J. A review of power output studies of Olympic and powerlifting: methodology, performance prediction and evaluation tests. J Strength Cond Res, 1993;7(2):76-89.
- Hoffer J, Andreasson S. Regulation of soleus muscle stiffness in premamillary cats. J Neuophysiol, 1981;267-85.
- Newton RU, Murphy AJ, Humphries BJ, et al. Influence of load and stretch shortening cycle on the kinematics, kinetics and muscle activation that occurs during explosive upper-body movements. Eur J Appl Physiol Occup Physiol, 1997;75(4):333-42.
- Baechle TR, Earle RW. Essentials of Strength Training and Conditioning: 2nd Edition. Champaign, Ill.: Human Kinetics, 2000.
- Hewett TE, Paterno MV, Myer GD. Strategies for enhancing proprioception and neuromuscular control of the knee. Clin Orthop Rel Res, 2002;402:76-94.
- Balyi I, Hamilton A. "Long-Term Athlete Development: Trainability in Childhood and Adolescence. Windows of Opportunity, Optimal Trainability." www.sportdevelopment.org.uk/bayli20041.pdf
- Balyi I. "Sport System Building and Long-Term Athlete Development in Canada. The Situation and the Solutions." Coaches Report, Summer 2001;8(1):25-8.
- Ericsson KA. The Acquisition of Expert Performance: An Introduction to Some of the Issues. In: Ericsson, KA, Ed. The Road to Excellence: The Acquisition of Expert Performance in the Arts and Sciences, Sports and Games. Mahwah, N.J.: Lawrence Erlbaum Associates, 1996, pp. 1-50.
Other Resources
- Knuttgen HG, Kraemer WJ. Terminology and measurement in exercise performance. J Appl Sport Sci Res, 1987;1:1-10.
- Wolfenden LE, Holt NL. Talent development in elite junior tennis: perceptions of players, parents and coaches. J Appl Sports Psych, 2005;17:108-126.
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