Here is a guest article from the one and only Dr Eamonn Flanagan. He has generously agreed to host some of his ideas on the blog, so here is his bio and I hopes everyone enjoys the article and thinks about how/if it can be applied to our training. I have taken the liberty of providing some videos to support Eamonn's ideas, all of which he suggested of course! Here is a link to his other guest article on the use of creatine for weightlifters.
Eamonn Flanagan is a strength and conditioning coach with the Scottish Rugby Union. He has formally worked with Munster Rugby and in hurling,athletics, rowing and AIL rugby. He is an 85/94kg lifter and represents the University of Limerick Weightlifting Club.
Plyometrics is the term now applied to exercises that have their roots in Eastern Europe where they were first known simply as “jump training” (Chu, 1998). They are exercises involving rapid, explosive movements for the development of athletic power. Examples of plyometrics include depth jumps, hurdle jumps and bounding. Plyometric training has been shown to have a number of beneficial effects for athletes. These primarily include the development of an athlete’s power production. Plyometrics can increase the speed at which athletes can develop force and injury prevention for athletes in sports where there is a high degree of jumping, landing and side-stepping movements. Plyometrics have been shown to be highly effective in ACL injury prevention programs for athletes in sports such as volleyball, basketball and soccer (Hewett, 1996).
The training adaptation to plyometrics takes place at a neural level (Markovic, 2005). Plyometric training does not increase muscle size. It increases the efficiency and speed of muscular contraction by training the body to activate more muscle fibers with better timing during these explosive exercises. It trains the muscles to use the stretch shortening cycle (SSC) more efficiently.
The stretch shortening cycle (SSC) is the basis of plyometric exercises. The SSC is a natural type of muscle function in which muscle is stretched immediately before in is contracted (flexed). This eccentric/concentric coupling produces a more powerful contraction than that which would result from a purely concentric action alone (Komi, 1992). For example, crouch down to a half squat position. Hold this position for one second and then jump as high as possible (without going down any further). This is a purely concentric jump, it can be difficult to get good jump height with such a jumping technique.
Now try a regular vertical jump in which you can crouch down and jump up very rapidly. This is an eccentric/concentric jump. You are sure to jump higher and develop more force, more rapidly in such a jump.
This eccentric/concentric coupling of the SSC is the natural form of muscle function, and it is evident in everyday activities, such as running, throwing and jumping.
There are a number of biomechanical mechanisms that contribute to the SSC. More about these involved mechanisms can be read in this article
All stretch shortening cycles are not created equally. The type of stretch shortening cycle can be described as fast or slow (Schmidtbleicher, 1992). Different biomechanical mechanisms are used in these different stretch shortening cycles. As a result, training in the fast SSC will not improve slow SSC performance, and vice versa.
The fast SSC is characterized by very short ground contact phases, quick eccentric/concentric (“up/down”) movements and limited range of motion at the knee hips, knees, and ankles. A typical example would be depth jumps. Other examples are fast, repeated hops over hurdles or repeated standing long jumps with short ground contact phases.
The slow SSC involves longer ground contact or contraction times, larger ranges of motion at the knee, hips and ankles and slower overall movement of the working muscles. An example would be maximal effort vertical jumps or box jumps. Other examples would be single standing long jumps and single hurdle jumps.
To understanding the application of plyometrics into a training program it helps to have an understanding of the force velocity curve. The force velocity curve dictates that humans can produce their highest levels of total force at very slow velocities and in activities of very high velocity, low total forces are produced. For example, a maximal effort back squat will generally be performed at a low velocity, but one will generate a very high level of total force. In sprinting, with each foot contact, a low total force is produced but the movement speed is very high velocity. The weightlifting movements, most likely, lie somewhere in between these extremes as moderate force, moderate velocity movements – cleans lying a little more toward maximal strength and snatches lying a little more toward maximal speed.
Plyometrics' position on the force velocity curve can be seen also. They are quick powerful movements. Many sport scientists and strength and conditioning coaches suggest that for optimal athletic development one must train across the force velocity spectrum. In powerlifting the conjugate system of Westside training also works from a similar principle with maximal high level loads lifted in the same training block as dynamic, high velocity lower loads. In most weightlifting programs this principle is also included: front and back squats are high force, low velocity. Heavy pulls are next down the curve. Then the weightlifting movements themselves.
Plyometrics could then be used to train faster force production abilities. By training across the whole force-velocity spectrum, the athlete is less likely to be inhibited by a deficiency in any one particular aspect of his performance be it speed, speed-strength or maximal strength. Plyometrics are a highly suitable way for weightlifters to train speed strength. Exercises such as box jumps, vertical jumps, depth jumps and hurdle jumps are all biomechanically similar to the weightlifting movements. They are bilateral (double legged), they use the same major muscles and joints, have similar range of motion at the active joints and similar timings of muscular activation. Uni-lateral (single leg) plyometrics such as bounding and hopping drills are probably not as biomechanically well matched to the weightlifting movements. Dreschler (1996) states that plyometrics can help to decrease the time it takes for a lifter to reach maximum force and improve their power output. But, he cautions that the modality of training is unlikely to produce any dramatic improvements in weightlifting performance.
There are a couple of other specific applications of plyometrics which could be useful in a weightlifting context. The first of those involve very young lifters or very novice lifters. With such lifters, they may not be technically proficient enough to perform cleans and snatches with enough weight to illicit a good training effect. If this is the case then from a force-velocity perspective, their training could be very lopsided toward maximal strength at low velocities. By incorporating simple plyometric exercises such as box jumps, hurdle jumps and standing long jumps the young or developing athletes can get a degree of speed-strength development in their training and also learn control and coordination of their bodies. Here is a video demonstrating this principle with Scottish coach Charlie Hamilton having his young lifters perform dynamic jumps onto plates:
Another very useful application of plyometrics is when weightlifters are suffering from upper extremity injuries such as wrist injuries. Here the weightlifter should still be able to squat heavy and develop their maximal strength capabilities. They are unlikely to be able to perform any cleans, jerks or snatches however. So plyometrics can be used extensively to keep their training volumes up and to develop their speed-strength capabilities while injured.
Lifters should use a variety of slow and fast plyometrics. The slow plyometrics such as vertical jumps and box jumps are good to use first as it is easier with these slower movements to teach good jumping and landing mechanics. Once athletes have mastered good jumping and landing mechanics they could begin to incorporate low-level fast plyometrics like repeated jumps over low hurdles. The degree of difficulty of these fast plyometric exercises could be slowly increased over time. One should exercise caution with fast plyometrics however. They are more intense than slow plyometrics and the strain they place on the nervous system is likely to be higher.
Dreschler (1998) comments on the placement of plyometrics into the weightlifter’s periodized training plan. It should be limited to one or two periods of several weeks per year. This could be one or two 4-6 week blocks of plyometrics in general preparation phases of training. The amount and intensity of the jump training should be carefully limited in the phases. Dreschler (1998) also suggests that once a weightlifter has learned the plyometric movements and begun to express fast force production well and effectively that quite a low amount practice (or the mere practice of the weightlifting lifts themselves) should be enough to retain the benefits of plyometric training. This could be as simple as the lifter performing 3 or 4 sets of 3 in the box jump at the beginning of a training session in his general preparation phase.
Overall, plyometrics offer a simple and effective way to promote fast force production and to train speed-strength capabilities of athletes. Their inclusion is probably most suitable for young or novice athletes and those with upper body injuries which limit their actual weightlifting movements. The benefit of plyometrics may be less for adult, mature lifters but they could still be used to train across the force-velocity spectrum and benefits (or maintenance) of fast force production can be achieved with a low volume of plyometrics.