Happy Sunday everybody! Today's discussion is going to be all about plyometrics .
This is one of the larger topics I get asked questions about, and hear the most amount of casual uninformed discussion on. Plyometrics have been around longer than the Olympic flame has been lit, however P90x (1 and 2) along with enterprising personal trainers looking to re-invent the wheel, have made it as popular as aerobics was in the 80's, and have taken it to levels that are detrimental to the long term health of the individual doing them.
Below I will go through the Science / Physiology stuff, the larger mistakes, and how to actually program plyometrics as a part of your workout cycle.
Physiology of a Plyometric Exercise
Plyometrics refers to exercise that enables a muscle to reach maximum force in the shortest possible time. The muscle is loaded with an eccentric (lengthening) action, followed immediately by a concentric (shortening) action.
How Plyometric Exercises Work
A muscle that is stretched before a concentric contraction, will contract more forcefully and more rapidly. A classic example is a dip" just prior to a vertical jump. By lowering the center of gravity quickly, the muscles involved in the jump are momentarily stretched producing a more powerful movement. But why does this occur? Two models have been proposed to explain this phenomenon. The first is the
Mechanical Model
In this model, elastic energy is created in the muscles and tendons and stored as a result of a rapid stretch. This stored energy is then released when the stretch is followed immediately by a concentric muscle action. According to Hill the effect is like that of stretching a spring, which wants to return to its natural length. The spring is this case a component of the muscles and tendons called the series elastic component. The second model is the
Neurophysical Model
When a quick stretch is detected in the muscles, an involuntary, protective response occurs to prevent overstretching and injury. This response is known as the stretch reflex. The stretch reflex increases the activity in the muscles undergoing the stretch or eccentric muscle action, allowing it to act much more forcefully. The result is a powerful braking effect and the potential for a powerful concentric muscle action.
If the concentric muscle action does not occur immediately after the pre-stretch, the potential energy produced by the stretch reflex response is lost. (i.e. if there is a delay between dipping down and then jumping up, the effect of the counter-dip is lost).
It is thought that both the mechanical model (series elastic component) and the neurophysical model (stretch reflex) increase the rate of force production during plyometrics exercises.
The Stretch-Shortening Cycle
All plyometric movements involve three phases. The first phase is the pre-stretch or eccentric muscle action. Here, elastic energy is generated and stored.
The second phase is the time between the end of the pre-stretch and the start of the concentric muscle action. This brief transition period from stretching to contracting is known as the amortization phase. The shorter this phase is, the more powerful the subsequent muscle contraction will be.
The third and final phase is the actual muscle contraction. In practice, this is the movement the athlete desires the powerful jump or throw.
This sequence of three phases is called the stretch-shortening cycle. In fact, plyometrics could also be called stretch-shortening cycle exercises.
Un-informed Exerciser / Trainer Problem Number 1: Skipping the prerequisites
Plyometric training shouldn’t be done in isolation, but as part of a complete training program that includes strength training. You don’t need to be able to squat a certain amount, but you do need to have a basic level of strength. Athletes will be better prepared by focusing on functional single leg strength rather than overemphasizing their maximum squat strength.
Also, before doing medium and high intensity plyometrics, the athlete must have proper landing mechanics. If the knees cave inward when landing, more strength is needed.
Any athlete can begin with low intensity plyometric exercises but medium and high intensity plyos should not be done until the prereqs are satisfied.
Un-informed Exerciser / Trainer Problem Number 2: Too much volume
The volume of plyometric exercises that should be done first depends on the intensity of the exercise. Low intensity plyos such as jumping rope, and warm up type plyos (like butt kicks and high knees) can be done in high volume. The volume of moderate and high intensity plyometrics, however, must be monitored carefully to avoid too much stress on the joints and ligaments.
The general way to measure volume in a plyometric program is by ground contacts (how many times you land). Even elite athletes do not exceed 140 ground contacts of medium / high intensity plyos per session. 1 Ground Contact = each time the foot takes off the ground, and lands.. So a box jump per "repetition" equals 2 Ground Contacts (1 on the box, 1 back on the ground)
The exact volume of ground contacts will depend on your training age (how often, how much, and how recently you’ve done plyometric work in the past) and the intensity of the plyometric exercises.
Un-informed Exerciser / Trainer Problem Number 3: Improper progression
Doing high intensity plyometrics before adapting to low and medium level plyometrics increases your risk of injury. Though a program may prescribe doing certain exercises for a certain number of weeks, the athlete should not progress to more complicated or intense exercises until the basics have been mastered. Any other strategy is asking for injury. Athletes should be able to perform every exercises and reps with maximum intensity, good form, and body control.
So How do I add plyometrics into my workout cycle?
First and foremost, they should be at the front end of your workout, typically one of the first items right out of the gate, after you are warmed up.. If you are training for performance, you want the energy systems to be able to handle the workload... If you are training just to burn calories, then insert it anywhere in your traditional strength / trx workouts. Below are the tenets to follow and some examples of good plyometric exercises.
Guidelines for Progression:
Adapt to landing before doing multiple response jumping drills
Double leg landings are less intense than single leg landings
Single response drills (one jump and one landing) are less intense than multiple response (several jumps with minimal ground contact time) drills
Examples of low intensity plyos
jumping rope
common warm up exercises (high knees, butt kicks, etc)
some that may be new: prancing (looks funny but works on “popping” the hips), galloping
Examples of medium intensity plyos
double leg: squat jumps, box jumps, broad jump
single leg: lateral jump and stick, scissor jumps
Examples of high intensity plyos
double leg: depth jumps, double scissor, mutiple squat jumps
single leg: bounding, multiple single leg hops
Final Thoughts
Many athletes don’t do any plyometrics for fear of injury. However, because sports ultimately involve jumping, plyometric training is an important part of a training program to decrease injury risk by allowing your body to adapt to the jumping and landing demands the sport entails before the season begins.
The idea here is not to say don't do plyometrics, but rather to do them correctly! If you are hesitant to add plyometrics to your training, start by adding low intensity plyometrics to your warm up routine. Progress to a low volume of a few medium intensity plyometric exercises.
As always comment questions you may have!
Thanks as always & as my friend Randy says, Stay Fit my Friends!
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