Thursday, 7 April 2016

Plyometric Training for everyday living.

As children, running, jumping and playing hopscotch was part of everyday activities; however, as we age our activities change. Jumping is an activity that is avoided by most adults either by choice or lack of need in their daily lives. 

The skills to develop rapid force production, involved in jumping are as important as balance and strength in keeping us healthy. Participating in regular plyometric training could help prevent a fall and reduce the loss of bone mineral density as we age.

Plyometric training was first identified as a useful training technique for soviet athletes in the 1980’s and has been used extensively for a large variety of athletes. However, every child does some form of plyometric activity through everyday play. 

The aim of plyometric training is to generate large amounts of force over the shortest amount of time as possible. Initially plyometric methods involved dropping from a height forcing the system into eccentric contraction (forced stretch while under contraction load) then contracting concentrically (shortening the muscle, main method of movement) as quickly as possible resulting in jumping. This is still applied in depth jumps. Today, the term plyometric is associated with any jumping exercise, even some that take time to load up rather than the rapid transfer of contraction methods.

Plyometric training largely focuses on concentric contractions: that is the shortening of muscles. It can also be applied to eccentric movements which can be more beneficial for injury prevention. Eccentric contractions are controlled lengthening of the muscle while still contracting. How does this help? By increasing one’s ability to generate substantial force quickly it will reduce the risk of falls. For instance, if you tripped you would be able to move your leg quickly enough to stabilise and prevent yourself from falling completely. In the elderly, falls are the number 1 reason for hospitalisation and loss of independence. 

It has long been known that bone mineral density (BMD) reduces as we age. We typically reach peak BMD in our 20’s. A reduced BMD increases the risk of fractures and broken bones from falls. Females are at greater risk of low BMD and increased rates of BMD loss especially post-menopausal women. There are several things that have a positive effect on BMD by reducing the rate of loss, or increasing the peak BMD for younger people. These include consumption of calcium rich foods regularly, getting enough vitamin D through exposure to sunlight and strength training. Of the many types of strength training, plyometric training has been shown to have the greatest impact on BMD.

Exercises and recommendations
There is a large variety of plyometric exercises employed by athletes that require equipment and coaching. Fortunately many can be done in the home or any open space. It is best to perform exercises on a soft surface such as grass or a yoga mat.

Firstly jumps, there is a vast variety of jumps, all of which apply plyometric principles.  Two common jumps are explained:
Basic 2 footed jump, it is not a requirement to leave the ground. The aim is to create maximal force acceleration through the calves, quads and glutes vertically. This is done by bending the knee and hips, then straitening them by pushing into the ground as forcefully as possible.

Single leg jump, start standing on one leg bend the knee. Then create maximal contractile force pushing into the ground straightening the knee trying to propel yourself as high as possible, again it is not a requirement to leave the ground.  But the action and force generation are key goals.

Once these simple jumps have been mastered, jumping or hopping directionally will increase the workout and increase stability and balance. Square jumping is one such method. Start by jumping forward then to the side, then back, finally back to the start.   

Depth jumps are very common for increasing force absorption. Start standing elevated to the ground then step off onto the ground and jump as soon as possible. Aim to have as little contact time with the ground as possible. 

Agility training is also another good method to increase force production rates without jumping. The fast changing of direction places similar stress on the tendons and muscles that stimulate the rapid force production. A simple agility set up is 4 points evenly apart, and stand in the middle.  Reach out and touch one of the points before returning to the centre as fast as possible.  Continue reaching out to each of the points and return to the middle each time.

Plyometric exercises are a great additive to your work out to increase speed and power with many other health benefits. They do require substantially more effort than conventional strength training and should be performed on non-consecutive days. So next time you see the kids playing hopscotch why not have a go!

Mark McCutchan
QUT Student Exercise Physiologist