Wednesday, February 29, 2012

Plyometric Intensity

Ebben, W.P., Fauth, M.L., Garceau, R.L., & Petusher, E.J.(2011). Kinetic Quantification of Plyometric Exercise Intensity. Journal of Strength & Conditioning Research, Volume 25 (number 12) 3288-3298.

Another article from a recent NSCA journal. This one is a study analyzing the intensity of plyometric exercises. The introduction describes how a wide variety of ideas of intensity are used to assess plyometric exercises and that a standard does not exist. I admit that my main textbook, Essentials of Strength Training and Conditioning, is vague on the topic and it's own assignments of intensity don't always make sense to me.

The importance of determining intensity is that is allows a sensible progression of exercise. For weight lifting it's easy. Intensity = weight, simple as that. For typical aerobic/anaerobic conditioning it's nearly as simple. Increases in time, speed or incline equal higher intensity. Comparisons between time, speed and incline are not well defined but frequently application or objective can be used for guidance. No similar metric exists for plyometric exercise.

Previous studies have focused on muscle activation or joint stresses for assessing the intensity of the exercise. These studies are useful but do not provide a complete picture, as they do not take into account the neural training. The neural training aspect of plyometrics should show a strong carryover to performance. Assessments of muscle activity and joint stress can be used to guide the number of repetitions per set, number of sets and total foot contacts per session when designing a program, as described here.

The present study analyzed the ground reaction force (GRF) and several other variables from a variety of different common plyometric exercises. GRF for take-off and landing are calculated separately and the authors conclude that these can form the guiding components. The other variables were well correlated to to these two or were obvious from the exercise. That is RFD, GRF and power will always be related. And a countermovement jump will normally have a longer flight time than a hop.

If the exercises are ordered from lowest to highest GRF then two separate lists are needed for take-off versus landing. However, I do not see how the landing plyos relate well to combat sports. If I'm hitting the ground at speed it's due to being thrown, not jumps and the like. Even the most energetic footwork appears to be quite modest compared to a drop jump.

Intensity of Takeoff from lowest to highest:
  1. Single Leg Jump
  2. Dumbbell Jump/Squat Jump*
  3. Countermovement Jump/Line Hop*
  4. Tuck Jump
  5. Cone Hop
 * Some levels have two exercises due to results that were similar.
These two links: Brian Mac and  Sport Fitness Advisor, provide visuals to describe the various exercises.

Note this progression is not a chart of difficulty of the exercise in general. I find the single-leg jump to be harder than a countermovement jump, but the takeoff force needed is lower for the single-leg jump. The SLJ spreads the force out over more time, so that peak force is lower even though the amount of force produced by the single leg is greater than in a double leg jump.

Other measures of intensity include power, jump height and time to takeoff. Power and jump height are strongly correlated, except that using a dumbbells increases the power needs of the exercise. As power is important for combat sports jump height can be used to progress the intensity of exercise, with dumbbell jumps at the highest intensity.

Time to takeoff is another important measure for combat sports because of the need for rapid execution of strikes. The most powerful strike is useless if it's too slow to hit, so a somewhat lighter hit that is faster can be more useful (especially if it allows a set-up for a harder hit). Time to takeoff follows the opposite progression of jump height with low jumps having a shorter time to takeoff. The exception is overloaded jumps i.e. the single leg and dumbbell jumps which have a high time to takeoff despite the low jump height. Drop jumps also have a short time to takeoff due to the elastic nature of the exercise. This suggests that low jumps in rapid succession may be the best training stimulus for rapid actions like those found in fighting.

The above information can  be used to design a program based on the needs of the particular athlete and the particular sport. If the coach concludes that the athlete needs to be faster than one program is indicated, but if the coach concludes that power needs to be worked then a different program is designed. Ultimately, a single best program will not be found, instead the program must be individualized to achieve the best results.

1 comment:

  1. This post took a long time for me to write. As I read more for putting this together I eventually realized that I needed the last paragraph about individualization. I'd originally intended to have produced the One progression needed for combat sports. And I realized that such would not be right.