Physio Focus: Plyometrics

plyometrics
Plyometrics, sometimes referred to as “jump training”, are exercises widely recognised as an effective means of building dynamic strength, and are increasingly being adopted by endurance runners for stronger running and injury recovery and prevention.

Physiotherapist Luke Bowman explains plyometrics in more depth and why these dynamic exercises can help you…


The term “plyometrics” was introduced in 1975 by an American track and field coach called Fred Wilt. Plyometric exercises were actually being used earlier than this, in the 1960s by Soviet athletes, and this was what led Fred to his research in the area. The word is derived from the latin “plio” (more) and “metrics” (to measure).

Formerly known as “jump training”, plyometric exercises are training techniques traditionally used to improve dynamic strength and explosive power. They are also often used at the latter stages of injury rehabilitation (both upper and lower limb) in order to provide functional loading, as most sports require some form of dynamic motion. If tissues are not stressed adequately prior to returning to sport, then they will be ill-equipped and more likely to reinjure.

What do the exercises involve?

Plyometric exercises involve a rapid stretch (eccentric phase), a powerful concentric contraction (shortening the muscle) followed by a phase of transition prior to the landing (which is again eccentric as the muscles contract whilst lengthening in order to provide a smooth deceleration).

Concentric: Take for example the bicep. In order bend the elbow to lift an object we need the bicep to shorten and contract. This shortening of a muscle under stress is known as a concentric contraction. Imagine having to throw that object above your head as high as possible… this is still concentric as the muscle is still under load and shortening. The only difference with plyometrics is speed, the terminology to describe the contraction remains the same.

Eccentric: Now the object you have thrown is coming back to earth and you need to catch it. The only way to do this without dropping it on your foot (especially if it is weighted) is to decelerate the forearm slowly once the object is in your hands. This contraction under controlled lengthening of the muscle is known as an eccentric contraction. This phase is key in plyometrics, not only for the controlled landing (if doing a jumping based exercise) but also prior to take off in order to store and release mechanical energy from the muscle/tendon unit (what we call elastic recoil). This means that the force produced will be greater.

plyometrics

Kangaroos: eccentric and concentric power in action

Kangaroos are a great example: they are amazing jumpers due to the length of their leg tendons. This allows 90% of stored energy to be released for the hop, meaning kangaroos can travel extremely long distances with very little food or water as they expend very little energy.

What’s happening in the body during plyometric exercises?

Plyometric training places increased stretch loads on the muscles and tendons. As they become more tolerant to this increased load the stretch-shortening cycle (eccentric/concentric) becomes more efficient.

To understand this fully we need to look at our neurophysiology, in this case how our nervous system interacts with our muscles and tendons. Specialist sensory receptors found on nerve endings called proprioceptors act to relay feedback to the central nervous system. These include the muscle spindle and Golgi Tendon Organs (GTO). Muscle spindles are found in the belly of the muscle, and GTOs in the tendon (as you might have figured!).

If a muscle is overstretched, the muscle spindle relays more signals to the spinal cord. The spinal cord then replies by sending a signal back for the muscle to contract to prevent over-stretching. The faster the stretch, the stronger the signals are sent.

The GTO on the other hand, relay inhibitory signals relaxing the muscle when it is overloaded. This helps to provide a balance and prevents your muscles from over-contracting.

So this links with plyometrics in that the more you use and stimulate these receptors, the more reactive the system will become. This helps with coordination, speed of contraction and movement. This is what we refer to as increased neuromuscular control.

So how does this help your running?

Research has shown that plyometric training can significantly improve areas including vertical jump performance, change of speed and sprint speed. However the question is, has there been any evidence of benefits for endurance running?

A study into the effects of plyometrics specifically on endurance and explosive strength in middle and long distance runners was carried out by Ramirez-Campillo et al in 2014, comparing a control and plyometric training group (18 male runners in each group) over a six week period. Significant differences were highlighted including a 3.9% reduction in 2.4km time in the plyometric group as well as a 2.3% reduction in 20m sprint time, plus gains in explosive power, when all were compared to the control group who had no significant changes.

Research has also been carried out in the area of injury prevention, with improvements in neuromuscular control (as discussed earlier) being suggested as an important factor in reducing injury.

Why should you start using plyometrics?

Plyometrics are a really useful tool to have in your training programme for several reasons:

  1. The exercises are functional and relevant (especially when you compare to non-dynamic, one-directional strengthening exercises) as the running motion/stresses exerted on tissues can be replicated. With this in mind, plyometric exercises are best used in different planes of movement (for example burpees with tuck jump, box jumps, split lunges/ lateral lunges, mountain climbers, dot drills, etc).
  2. Plyometrics have a good evidence base which suggests benefit in a variety of sporting settings, including endurance sports like running.
  3. The improvements seen in change of direction speed, explosive power, vertical jump, etc, can also be applied to middle-to-long distance running, for example interval/fartlek training when you require a change of speed or during a race to change direction, avoid an object or accelerate suddenly.
  4. Injury rehab: As mentioned earlier, plyometric exercises are a very useful tool in a physio’s toolkit and can be extremely helpful when getting an athlete back to full fitness. This is because we can start to replicate and control dynamic and functional movements required when running (change of speed, direction etc). If you have been injured, take advice from a physio about when and how to introduce plyometrics.
  5. It is always good to break the repetitive cycle of running training especially if you (like most!) don’t incorporate a sufficient variety of strength and conditioning exercises into your programme.

How do you get started? (and what should you avoid?!)

The best approach is to seek the guidance of a qualified personal trainer or physio so you can identify the most appropriate exercises and avoid getting injured.

Make sure to warm up thoroughly and start with a few exercises, working on correct technique and control before you build up. As with any training your body needs time to adapt.

One important thing to note is that you should NOT start a plyometric programme with an active injury before seeking advice on what and when to commence. If you start using dynamic exercises on an injury which isn’t ready it may affect healing and slow recovery or even further damage the structure.


phsyio focus
Luke Bowman (BSc Hons Physiotherapy, HCPC and CSP registered) is the owner and lead clinician at Reform Physiotherapy.  Luke has a wealth of experience in musculoskeletal Physiotherapy. In addition to his work at Reform Physiotherapy, he works at the University of Cambridge with a wide range of collegiate athletes and the up and coming elite in sports including rowing, cycling, running, rugby, football, swimming, golf, athletics and basketball. Luke has a special interest in the area of gait analysis and lower limb biomechanics helping to give an extremely varied approach to symptom management, addressing the underlying causes of pain and dysfunction. Contact him via the Reform Physiotheraphy website, via Facebook or Twitter, on 01799 530650 or 07399 499959, or email reformphysio@outlook.com.

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