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.

Wooden Legs

This past weekend I was at an event, hitting friends with swords as usual. One of the guys there described feeling 'wooden' in his footwork. And he talked about what training things he was doing about it.  While we were fighting he said that he started off feeling like he was moving well, what I think of as explosive, but that he quickly slowed down.

He attributes the problem primarily to some weight that he's put on.

After watching the video of the day's fighting, I'm not sure that he actually slowed down all that much. So maybe part of the problem was perception. Maybe it was cardiorespiratory.

His chosen solution was Tabata's or rather high-intensity interval training (HIIT). He does footwork patterns at high-intensity with an interval timer. And some of those intervals he does while carrying extra weight. He also does jump rope, and I'm not sure what else is part of his training regimen.

I think there are a couple of ways he can improve the training for his footwork.

1) The Tabata's - the Tabata protocol is based on very high intensities of exercise - in the realm of 170% of VO₂max. These are done for short durations, generally around 20 seconds. And there are rest periods in between sets of anywhere from half as much time to two to three times (that is work:rest ratios of 2:1 to 1:3). Footwork patterns aren't gonna do that. And footwork while carrying extra weight still aren't likely to hit that intensity for his legs. To get that kind of intensity of exercise in his legs, he should probably be jumping, hopping, bounding and other plyometric exercises like that.

Carrying 50lbs. while doing footwork increases the intensity by about 25% for a 200 lb. person. But jumping easily reaches 100%+ of bodyweight. So added weight is good, but jumping is better.

By carefully picking what kinds of plyos he does he can maintain a high-degree of specificity in the exercises, while also upping the intensity level beyond just footwork. As these are a new exercise for him, he should start with low-intensity plyos and work his way up progressively.

Altogether, this should provide a better conditioning training for his footwork.
The next two sections are more strength training than conditioning solutions to his wooden legs. And should be done in conjunction with the HIIT. The basic idea is that if the necessary force for a given action is a smaller percentage of max then endurance increases without sacrificing speed. For example, if I go from a 12" vertical to a 18" vertical then I can do 6" more times because each one represents a smaller portion of my max.

2) Explosive lifts - Ideally, these would be Olympic lifts, like the Power Clean. However, those require expensive equipment and significant training. So for a simpler solution we can do Squat Jumps, as described by Mike Boyle in Functional Training for Sports (p. 165). This exercise consists of simple jumping straight up from a squat position. It is important to get full extension of the hip, knee and ankle in this exercise.

The intensity of this exercise should be increased until each set consists of only 3-5 jumps in a row. This is done by adding weight, such as dumbbells, which can be held in the hands. For a lower body exercise like this weight can be increased in 10-20# increments.

Rest periods between sets should 2 minutes or longer, and the athlete should do at least 3 sets. For efficiency of time the athlete could do a light upper body activity in between sets.

3) Conventional weight lifting - Squats, leg presses and deadlifts will all contribute to lower leg strength and be useful in explosive footwork. Straight leg deadlifts do a good job of focusing on the glutes, while the squats/leg press focus on the quadricpes, so both exercises should be done. Single-leg variants of both of these exercises are also a good addition to the program.

For improving explosiveness in footwork weights should be chosen in the range that develops strength and power. So 1-6 RM weights. These are going to be large weights for such exercises and an athlete new to these should proceed slowly.

A program might look like four workouts a week for this, with two strength training and two plyo/conditioning days each week. A day off between each workout is ideal, which results in an 8 day cycle.

Increasing the Impact Force of the Rear Hand Punch - Part 2

Rear Leg Drive was covered in the previous post. This post will deal with the other 4 concepts from that article.

* * *

Turner, A., Baker, E., Miller, S.,  (2011). Increasing the Impact Force of the Rear Hand Punch. Strength and Conditioning Journal, volume 33 (number 6), pages 2-9.

The article discusses the kinetics and kinematics of the rear hand punch to show ways of increasing the impact of the punch. Turner indicates that the material is generalizable to other strikes, which I don't doubt. The rear hand punch is used as the basis of the analysis because it is well understood, used in many arts and the most powerful punch.

Five key aspects of the punch are identified to optimize the strike:
1. Rear leg drive
2. Landing with a rigid front leg
3. Stretch-shortening cycle of the trunk
4. Velocity of the strike
5. Effective mass of the strike

These key aspects align with the key elements of the kinetics of the strike
Rear Leg Drive - the rear leg is used to initiate the strike and extended explosively to contribute power. This is done with the front leg in the air and moving forward. The more powerful the rear leg drive the harder the strike.
Rigid Front Leg - the front leg must land rigidly to provide a brake on the forward motion of the body. This focuses the rear leg drive on the upper body. The more rigid the braking action, the more force is transferred to the strike.
SSC of the Trunk - the rear shoulder is pulled back early in the strike coiling the trunk to generate more power. This occurs because of the elastic nature of musculature. Stretch Shortening Cycle (SSC) is the neurologic component that increases the elastic reaction of the muscles. A better trained SSC in the trunk increases the trunks contribution to power.
Velocity of the Strike - the arm can move at tremendous speed and is quite light, so it's primary contribution to force is through velocity. The faster the arm moves the harder the strike.
Increase Effect Mass - the arm actually slows down just before the strike lands. Activation of the muscles in the arm to make it rigid cause this effect. A rigid arm allows more of the mass of the body to be contributed to the power of the strike.


Rigid Front Leg
Landing with a rigid front leg will cause more force to be transferred to the strike. Substantial bend in the knee is the most likely indicator that the front leg is not rigid enough. Training for a more rigid leg should be done gradually, because we are training to overcome the body's natural defense against impact/landing. As long as this process is done gradually then the connective tissues and related structures will strengthen appropriately.

Training for a more rigid landing can be done with box drops. Simply step off a plyometric box (or similar) and land. Don't focus on trying to land rigidly, let that develop at it's own pace. Start with small boxes and work your way up to taller boxes, as well as single-leg drops. When incorporating this with other plyometric programs it is important to take into consideration the total number of contacts per training session, so as not to overload the tissues.

Olympic lifts and squat jumps will also help develop this characteristic.

Stretch Shortening Cycle of the Trunk
The rear hand punch, and many other strikes, include a wind-up action that brings the elastic nature of the muscles into play. This elasticity is the reason that untrained folks will naturally pull their fist back before punching. It's also the reason why when you jump you naturally drop down just a bit before moving upwards.

The elasticity of the musculature is the result of two factors: connective tissue is elastic similar to the way that rubber bands are; and our nervous system has controls on the muscles that produce a similar effect - which is known as the Stretch Shortening Cycle (SSC). These two together can substantially add to force production.

Medicine ball exercises can be used to train this capacity. The most basic is a side pass.

1. Stand in your typical striking stance with your left foot forward. 
2. Hold a medicine ball at arm's length with both arms. 
3. Rotate clockwise a short distance, quickly and then reverse direction and throw the ball. 
4. If possible catch the ball and repeat, making sure to counter turn a little with each catch or before each throw.

• Focus doing the throw with the torso, not the arms.
• For this exercise, we are concerned with rapid action so a light ball of around 2 kg is sufficient. 
• Not all med balls are equal, some bounce better than others. For fighter training I think the bouncier kind are more useful for a wide variety of drills.

A forward and backward pass can be done as well, following the same principles. For the forward pass face the wall with your feet squared and the ball over head. Arch back just a little bit before throwing forward. The backward version is done while facing away from the wall and you crunch forward just a bit before throwing overhead and backwards.

There are plenty of good variations on these exercises. This is meant as a good start.

Increase the Velocity of the Punch
Training to increase arm velocity will focus on ballistic type exercises. The focus is on speed not just weight. Here again, medicine ball exercises will help. A variety of throws using form similar to strikes will work for this kind of training. Again, use a light medicine ball to focus on velocity of action. However, the simplest ballistic upper body exercise is the clap push-up.

Another option is to use resistance bands for conventional weight training exercises (not discussed in the article). These increase resistance progressively and so the action starts off fast with a light resistance and the load increases as velocity decreases. This method also plays well into the next concept.

Increase the Effective Mass
The effective mass of the hit is determined by how rigidly linked the parts of the arm and body are at impact. The more rigid they are at impact the more weight is behind the punch. Studies of muscle activation in punches show a double-peak effect. As the hand starts to move forward the muscles activate strongly. Then the relax and the hand sort of glides forward. Last the muscles activate again making the arm and wrist rigid.

This double peak is not observed in shadow-boxing or other training done "in the air". So training with a solid striking target is necessary to train the body to transfer force on impact. Pad and bag work is the basic way to do this. For weapon arts it's necessary to have a striking target like a pell to hit.

* * *
The article also has a sample program to show the combination of these various training elements. That's a whole other topic though, and I'll get into it with later posts.