Numerous books and articles have been written about plyometric training for athletes. However very few offer detailed progressive programs that take into account the need for a system of training that can be applied to a broad range of athletes. Instead you get a smorgasbord of exercises and opinions. Although the works of Chu, Radcliffe and Gambetta were outstanding at the time of their writing, very little has been written in the last ten years that connects our current knowledge of functional training with how to design and implement a system of plyometric exercises. In order to fully understand plyometrics, we must look at basics like terminology, volume and frequency.
Terminology
The first area that needs to be addressed in the area of plyometric training is terminology. The language of plyometrics must be universal so that any coach or athlete can view the program of any other coach or athlete and understand the exercises ideally without photos or video. The discrepancies in terminology were first brought to my attention by Mike Clark of the National Academy of SportsMedicine. Clark pointed out in a 2000 lecture that many coaches currently used names to describe plyometric exercises that were not properly descriptive of the movement.
Clark went on to detail the types of exercises and the specific actions:
Jump- two leg take-off and landing
Hop- single leg takeoff landing on the same foot
Bound- single leg take-off landing on the opposite foot
Skip- single leg takeoff with two foot contacts
Although many might view these descriptions as simple and common sense, I realized that I inadvertently had misclassified exercises. We had always referred to two legged jumps over hurdles as hurdle hops. I believe that this was and still is a common error among many strength and conditioning and track coaches. Clark made the facetious point that "bunnies don't hop, they jump".
Many might view this as a minor discrepancy but, a call from a coach in California made me realize the cost of "minor discrepancies".
The coach in question called me and said "Boy, are your guys great athletes, I can't get one guy on my team to do those thirty inch hurdle hops you guys do." I quickly realized that my "minor discrepancy" had caused this coach to try to perform an exercise with one leg that we had been doing with two. He had his athletes hurdle hopping as the program indicated while I had mine hurdle jumping.
A small detail? Maybe.
The reality is that an athlete could have been badly injured because of my incorrect use of descriptive terminology.
Categories of Exercises
After looking at terminology, the next area to examine is the categories of the different types of jumps, hops and bounds. I believe that this is the major failing of the most popular commercially available ACL injury prevention programs.
The two most popular, The Santa Monica PEP program and the Sportsmetrics program focus almost exclusively on jumps with no emphasis on bounds or hops. The reality is that the mechanism of the ACL tear is most frequently in a single leg hop (actually a redundancy as the term hop denotes single leg) or bound scenario, not a double leg jump.
A sound plyometric program must include a balance of exercises from each terminology category. Athletes must perform a balance of jumps, hops and bounds. In addition, hops must be done both forward, at 45 degree angles and potentially side to side. It should be noted that hopping medially and laterally are entirely different in both the muscles stressed and the injury prevention potential.
Medial hops ( hops toward the midline) are more difficult and provide much needed stress to the hip stabilizers.
Lateral Hop
A recent change we have made is to eliminate medial and lateral frontal plane hops in favor of medial lateral 45 degree hops. This was based on the realization that most decelerations come at angles closer to 45 degrees.
Volume
One question that begs to be answered revolves around the volume of jumps. Volume is measured by the number of jumps per session and has most frequently been measured by the number of foot contacts. Recently we have seen lots of recommendations for what are being referred to as extensive plyometrics. The concept basically advocates a high volume of "little jumps" to build up to more intense plyometrics.My feeling is that the term extensive plyometrics is a bit of an oxymoron. The whole idea of plyometrics is facilitate explosive contractions with the eventual goal of reduced ground contact time
One of the major failings of many plyometric programs is too high a number of foot contacts. Extensive plyometrics not only doesnt solve this problem but, more than likely exacerbates it. We also have to distinguish if some of the "extensive plyometrics" recommended are valuable, necessary or even really plyometrics ? Although in a technical sense all movements involve strech shortening I'm not sure that jump rope or line hops prepares the tissue properly for the more intense activity to follow?
We try to keep the number of jumps, hops and bounds at roughly 25 per day and 100 per week and never use extensive plyometrics in a preparatory phase.
Intensity
Instead, we use a realtively constant volume of drills that progress in intensity. The intensity of plyometric training is difficult to measure and really involves understanding the difference between a program of controlled jump training and a true plyometric program. Many exercises that we consider to be plyometric in nature are actually simply jumping exercises. A box jump is really just a jump. In order to be "truly" plyometric there needs to be a reactive component. However, our program is probably better described as a "progression to plyometrics" program.
Controlling the intensity of plyometric exercises is actually based on controlling how gravity is allowed to enter the picture and to act on the body. Jumps up to a box or hops up to a box are the lowest intensity as they involve a strong concentric contraction but minimize eccentric stress by not allowing the body to "in effect" come down. With box jumps and box hops, what goes up does not really come down. The body is accelerated up to a height but not allowed to travel back down. The athlete jumps up and steps down, thereby effectively negating the effect of gravity as an accelerating force.
What we do know is that mistakes in plyometric progressions will manifest themselves primarily as patella femorall issues. This could be due to tendon loading issues or to overstress of the patella femoral joint but in either case the issue is too much jumping ( or hopping)and or drills that are not properly progressed in intensity. Volume is frequently the enemy, particularly in atheltes that already experience a high volume of foot contacts in practice or training. Professor Jill Cook points out that peak tendon stress is at the point of switching from eccentric to concentric contraction. The goal of our progression is prepare for that point in a more controlled and thoughtful manner.
Chu's early work classified intensity of jumps based on whether the jumps were done in place or, covered horizontal distance. Although this early quantification system of in-place, short, and long was state of the art in the eighties, our increased analysis of the effects of physics on the body leads us to a system that I believe better describes the effect of jumps. I prefer classifying jumps as gravity reduced or gravity enhanced and then move to semi-elastic ( bounce) and elastic (rebound or continuous). Early plyometric descriptions left no room for jumps that were actually not plyometric in nature.
The following videos illustrate our progression
Phase 1- Jump or Hop Up- the objective here is to reduce the conribution of gravity. What goes up is not coming down)
Phase 2- Jump or Hop Over ( jumps over obstacles increase the intensity by incorporating the idea of accleration due to gravity)
Phase 3- Mini Bounce- this phase prepares the tendons for the hard switches of phase 4. After listening to Jill Cooks discussion on the Jake Turra Jacked Athlete podcast we have more support for what was previously an empirical step.
Phase 4- In this phase we progress to what most coaches would view as plyometrics. This is the "react to the ground" phase. Some might criticize the time needed to get here but we want to "arrive healthy". ( and yes, that is a 30 year old Michael Boyle in the video)
Frequency-
One of the first questions when discussing frequency and plyometrics relates to the NSCA position statement. I find it intriguing that the NSCA once published such a short sighted piece. In the initial position statement the NSCA took the position that plyometrics should only be done twice per week. This has since been amended to read that the same joints should not be worked on consecutive days. The NSCA takes no position on intensity or volume other than to indicate that depths jumps may be too intense for larger athletes. My feeling is that plyometrics can be performed up to four times per week but, must be divided into linear and multi-directional days. Linear plyometrics involve pure sagittal plane jumps and hops, while multi-directional plyometrics work in the frontal and transverse planes.
Transverse Plane Plyometrics
I believe that athletes must do decelerative work in the transverse plane but, think that transverse plane jumps and hops must be approached with great care. It must be noted that in many cases the transverse plane exercises recommended look very much like the injury mechanisms we are trying to avoid.
Age/ Level of Experience
Another interesting point in the NSCA statement relates to the development of a proper strength base for plyometrics. No one has defined what proper is. Previously foolish, short-sighted recommendations were made relative to strength base. Some writers recommended a certain number of weeks of strength training prior to beginning a plyometric program, others recommended a certain strength level prior to undertaking a plyometric program. It is my feeling that strength training and plyometric training can be done concurrently providing common sense is used.
The reality is that young athletes begin intense plyometric programs without a strength training base or a required strength level every day. Both gymnastics and figure skating involve intense plyometric type activity from very young ages. The key is to manage the effect of gravity on the body. The keys to a plyometric program are simple:
Good plyometrics are quiet. Failure to land quietly indicates that the athlete lacks eccentric strength and that the exercise is inappropriate. All that may be necessary is to decrease the height of the obstacle involved. Athletes should only jump onto boxes that they can land on quietly.
PS- Athletes should always jump from and land in from the same position.
Bibliography Chu,D Plyometric Training, NSCA Journal Gambetta, V Leaps and Bounds, Training and Conditioning, Momentum Media