Training Tips - Plyometrics Overview

Plyometrics is a type of exercise that uses explosive movements to develop muscular power which is the ability to generate a large amount of force quickly. It can be used in a variety of ways, for example, to improve the effectiveness of a boxer's punch, or to increase the jump height of a basketball player. Plyometrics is a very useful tool in martial arts where explosive power is used from both upper and lower body. Plyometric training acts to increase an athlete's power output without necessarily increasing their maximum strength output.


Physics of plyometrics

Muscular power is determined by how quickly strength is converted into speed. The ability to convert strength to speed in a very short time allows for athletic movements beyond what raw strength will allow. Therefore an athlete who has strong legs and can perform the freeweight squat with extremely heavy weights may get less distance on a standing long jump or height on a vertical leap than a weaker athlete trained in plyometrics. Though the plyometrically-trained athlete has a lower maximal force output and could not squat as much, training allows them to compress the time required to reach their maximum force output and allowing them to develop more power with their contraction.


Safety Considerations

Plyometric exercises carry increased risk of injury due to the powerful forces generated during training and performance, and should only be performed by well-conditioned individuals who are under supervision. Good levels of physical strength, flexibility and proprioception should be achieved before commencement of plyometric training.

Flexibility is required both for injury prevention and to enhance the effect of the stretch shortening cycle.

Proprioception is an important component of balance, coordination and agility, which are also required for safe performance of plyometric exercises.

Further safety considerations include:

• Age - low-intensity and low-volume only for pre-pubescents.
• Surface - some degree of softness is needed. Gymnastics mats are ideal, grass is suitable.
• Hard surfaces such as concrete should never be used.
• Footwear - must have adequate cushioning and be well fitting.
• Bodyweight - athletes or patients who are severely overweight or obese should be very careful and low-intensity plyometric exercises should be selected.
• Technique - most importantly, a participant must be instructed on proper technique before commencing any plyometric exercise. They should be well rested and free of injury in any of the limbs to be exercised.

Plyometrics are not dangerous, but the potential for high intensity and stress on joints and musculo-tendonous units makes safety a strong prerequisite to this particular method of exercise. Low-intensity variations of plyometrics are frequently performed in various stages of injury rehabilitation, indicating that correct performance is valuable and safe for increasing muscular power in all populations.


Exercise

Intensity
The intensity of plyometric exercises varies greatly. Skipping exercises are classed as low intensity, while reactive drop jumps from 32in (80cm) and above are the highest intensity of the plyometric exercises. See the table below for further intensity classifications:

Exercise Type Intensity
Depth Jumps 32-48in (80-120cm) High
Bounding Exercises Submaximum
Depth Jumps 8-20in (20-50cm) Moderate
Low Impact jumps/throws Low

Plyometric training should progress gradually from lower intensity to higher intensity drills, especially for individuals who lack a significant strength training background.
Increasing the load by adding additional weight thought weighted vests of ankle weights for example, is not recommended. Too great a load can reduce the speed and quality of movement negating the effects of plyometrics.

Volume
Plyometric volume relates to the number of repetitions per session. For lower body exercises a repetition is a ground contact. See the table below for the number of repetitions recommended for a plyometric training session:

Experience Ground Contacts
Beginner 80-100
Intermediate 100-120
Advanced 120-140

Frequency
Typically, 2-3 sessions of plyometrics can be completed in a week. Alternatively, recovery time between sessions can be used to prescribe frequency and is recommended at 48-72 hours .
It is not recommended that plyometric training be scheduled for the day after a heavy weight training session when muscles may still be sore.

Rest Intervals
The effectiveness of a plyometric training session depends on maximal effort and a high speed of movement for each repetition. Rest intervals between repetitions and sets should be long enough to allow almost complete recovery. As much as 5-10 seconds may be required between depth jumps and a work to rest ratio of 1:10 is recommended. For example, if a set of bounds takes 30 seconds to complete, the rest interval between sets would be 300 seconds or 5 minutes.