The idea of plyometrics is for the muscle to reach its maximal force in the shortest possible time. If you look at the continuum below, lifting a heavy weight, say a squat at 80% 1RM, as quickly as we can will, not allow the muscle to reach its maximal force in the shortest possible time compared to hurdle jump. This is because in the squat the speed of movement will not be as fast as without the weight.
In order for the muscle to reach its maximal force, it goes through what is known as the ‘stretch-shortening cycle’. This occurs when the muscle is loaded eccentrically followed by a rapid concentric action. Think of the action of a vertical jump. As we push the hips back loading the hamstrings, the hamstrings stretch reflex kicks in, allowing the stretch to occur but limiting the amount of stretch. But as you are looking to jump, the muscle contracts quickly allowing you to jump, releasing the stored energy. Think of a rubber band. If you push the hips back and hold this position for a second or more, the energy built up in the stretch is lost, you won’t jump as high. ‘Because of the elastic quality of muscle tissue, the eccentric action followed quickly by a concentric action increases the contractile force of muscles beyond what would occur if the movement were performed without the stretch-shortening portion.’ (Newton, 2006, p.31).
The issue with plyometric and power training over the past few years is the buzzword ‘functional training’. People seem to be adapting and coming up with exercises they claim are ‘functional’ when in fact they could be detrimental to your sport or even cause injury. For example, the golf swing using a cable column: “I can power from the top of the movement and mimic my swing”. OK, so at the end of the swing do you continue to accelerate once you have hit the ball with a club? Yes. With the cable column does the swing slow down as resistance is increased as you get further away? Most likely, a better exercise, in my opinion, would be a side throw with a medicine ball, as with this exercise, you accelerate and power through releasing the ball, working on core rotation. Ok, it’s not as ‘sports specific’ as the cable column example but in my opinion far more transferable and likely to give you more benefits to your swing. The problem is people tend to think they are training absolute speed, but due to the weight they have added the exercises changes and is slowed down so they work in the speed strength or strength speed box. Due to the loading in the cable swig the biomechanics of the exercise changes, defeating the objective and purpose of the exercise.
In the following lower bodyexercises we look to progress from exercise that are not utilising the stretch shortening cycle to exercises that do – so some are not pure plyometrics. The exercises at the start are regressed from the box jump to make sure we can land before we can jump. If you can’t land, you can’t jump – poor landings increase the chances of injury, particularly to the ACL. In your teens and early adulthood you are unlikely to have spent much time landing and jumping – even if you play football I doubt you have thought much about your landing position or even practiced it.
The potential use of your plyometric activity is determined during the amortisation phase –the braking section. This occurs when the transfer of energy from eccentric motion to the concentric motion and accelerate. The quicker you get at this, the better your jump/throw. During this phase the stretch reflex kicks in – which is an involuntary response that helps protect the body from overstretching. The stretch reflex causes the muscles to tighten, preventing them going beyond their range of movement.
There are many more exercises regressions and progressions which could be added in between some of the exercises listed. There is also far more plyometric exercise that can be done laterally, as many sports do not just involve the leg muscles working linearly.
*For all of the exercises mentioned below look to complete 3 sets of 5 repetitions. Depending on your level of training and experience in plyometrics follow the table from Baechle and Earle (2008) referring you overload principle and how many contacts you should not look to exceed each session.
Appropriate Plyometric Volume
80 – 100
100 – 120
120 – 140
Baechle and Earle (2008).
Jump and land progressions
1, Eccentric loading
Stand with your feet about shoulder width apart, arms stretched out in-front parallel to the floor. Drive your arms down to your side as fast as you can and drop into a half squat position and hold for a second or three. When you drop prevent the knees turning in and push your hips back to load the hamstrings. Land softy, not on your heels or toes but the ball of your foot and use the muscles to absorb the force.
2, Drop Landing
Stand on a box or step which is not too high, the usual steps you get in a gym will be fine to start with. Look to progress to a box that is around your knee height. Standing feet shoulder width apart, step off the box and land with both feet on the floor at the same time with feet shoulder width apart. Eccentrically load the hamstring by dropping into a half squat position as you land (absorbing the energy) hold for a second or three in a half squat position. Land softy, not on your heels or toes but the ball of your foot and use the muscles to absorb the force.
3, Box Jump
Using the stretch shortening cycle, load up the hamstring and jump up onto a box. Make sure at the start (throughout the takeoff) and landing your feet are shoulder width apart, knees do not turn in. Land softy, not on your heels or toes but the ball of your foot and use the muscles to absorb the force.
4, Single Leg Box Jump – forward and lateral
Start with a regular small step you see in the gym. Start with one leg and jump up onto the step landing with the same leg, land with the same technique as all the other jumps, only on one leg and prevent the knee turning in on/out the takeoff and landing. Land softy, not on your heels or toes but the ball of your foot and use the muscles to absorb the force.
5, Hurdle Jump and Stick
Look to start with the small speed, agility quickness hurdle you get and progress to higher hurdles when you feel comfortable (12-30 inches). Start in the same position as the box jump, half squat, feet shoulder width, knees not turning out. Jump up and over the hurdle and Land softy, not on your heels or toes but the ball of your foot and use the muscles to absorb the force. Hold this position for a second or three and jump over the next hurdle.
6, Single Leg Lateral Jump and Stick
Perform these jumps bother laterally and medially to work the inside and outside of the knee, stabilising you as you land. Take a small agility hurdle, stand sideways on. Standing on one leg hop up and over the hurdle landing in the correct position, drop the hips back slightly loading up the hamstrings. Keep an eye on the knees turning in/or out upon landing. Land softy, not on your heels or toes but the ball of your foot and use the muscles to absorb the force. Hold this position for a second or three.
The following are exercises that would be deemed proper plyometrics as they are utilising the stretch shortening cycle. The previous exercise have been focused on eccentric strength and injury prevention, loading the hamstrings eccentrically as you land and stabilise.
7, Hurdle Jump, bounce, takeoff
Same as the hurdle jump and stick, but before you takeoff over the next hurdle add a little bounce before jumping over the next hurdle
8, Single Leg Hurdle Jump, Jump
With a small hurdle, jump over the hurdle with a single leg, take off over the next hurdle immediately.
Baechle, T, R., and Earle, R., W. (2008). Essentials of Strength Training and Conditioning. 3rd Ed. Human Kinetics, Champaign IL.
Boyle, M. (2004). Functional Training for Sports: super conditioning for today’s athlete. Human Kinetics, Champaign, IL.