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The Compex

The Complex is a portable muscle stimulation device. It is often used for pain relief, to prevent muscle loss after injury or surgery, and to improve muscle strength.

 It can be used in many fields eg: post-operatively, for people with neurological conditions, and for athletes wanting to improve performance. This blog will look at the following topics:

  • How does the Compex work?
  • What to expect when using the Compex
  • The evidence behind muscle stimulation

How does the Compex work?

The Compex works via stimulating our nervous system which tells our muscles to contract. The nervous system is made up of our brain, spinal cord and many nerves 

There are two main types of nerves, sensory and motor nerves. Sensory nerves help us to feel eg: temperature and pressure. Motor nerves help us to contract and move our muscles. When specific motor nerves are stimulated it will cause specific muscles to contract.

When we decide to contract a muscle, our brain sends a message to nerve fibres. This message occurs through an electrical signal. The signal is then sent to muscle fibres and the stimulus causes them to contract.

Muscle stimulation devices work in a similar way. They use electrical impulses to stimulate nerves. The nerves become excited and transmit this signal to the muscle fibres. This results in a response from the muscle (a twitch). When lots of muscle fibres are stimulated, a large muscle contraction can occur. The Compex can stimulate motor or sensory nerves. When stimulating motor nerves, the aim is to cause muscle contractions to improve muscle performance. This is also known as EMS (electrical muscle stimulation). When stimulating sensory nerves, the goal is to reduce pain. This is also known as TENS (transcutaneous electrical nerve stimulation).

What to expect when using the Compex

The Compex has various parts. It consists of the main device, wireless modules, and electrodes. The device is where you choose settings and can change the intensity of the contraction. You can also change what type of nerves you want to stimulate (motor or sensory). The electrodes stick onto the skin. The placement of the electrodes depends on what muscle you are targeting. The modules clip onto the top of the electrodes. They are wirelessly connected to the main device and provide the programmed electrical stimulus.

Once the Compex is set up with the appropriate settings, you can start treatment. Initially, the device scans the muscle to see how much electrical stimulus it can tolerate. This will likely feel tingly and may contract the muscle. After this, you can begin the program. Sessions will have a warm-up phase at the start and a cool-down phase at the end. What you feel during treatment will depend on the setting that is chosen and the level of intensity selected. This can range from a light tingling sensation to a strong muscle contraction lasting 5-10 seconds. The duration of treatment also depends on the selected setting. It can be normal to experience some muscle soreness after using the Compex. This is because the muscles have been working, as they would during exercise. This soreness should feel similar to muscle soreness experienced after a work-out.  It shouldn’t last longer than 48-72 hours.

The evidence behind muscle stimulation

There has been lots of research on the effectiveness of muscle stimulation. The Compex claims to improve strength, improve power, improve jump height, increase muscle volume and reduce lactic acid. Summarised below are some findings from research articles on electrical stimulation:

Muscle stimulation significantly maintained and increased muscle thickness and strength after ACL surgery. This was compared to a group who underwent surgery but did not use muscle stimulation post-operatively. These findings were present at 4 weeks and 3 months after surgery. 

  • Muscle stimulation can have performance improvements for healthy adults and athletes. This study saw significant improvement in muscle performance and the performance of explosive activities such as jumping and sprinting.3
  • Applying the Compex over 6 weeks can significantly improve muscle strength and vertical jump height in gymnasts. This finding was maintained 1 month after treatment.4
  • 5 weeks of treatment with the Compex can improve muscle strength, jumping and kicking capacity in soccer players.5
  • Muscle stimulation can assist in reducing lactic acid buildup. One study in swimmers found that it had equal effect to gentle exercise in recovery. It was suggested to be an alternate method of lactic acid removal.6,7
  • Muscle stimulation is beneficial for critically ill patients to maintain muscle mass.8

We have Compex devices at the clinic for hire or purchase. They are effective tools to use in conjunction with other Physiotherapy treatments and may help you to reach your goals sooner rather than later.


  1. What is EMS machine & how it works? Compex. Published 2015. Accessed April 30, 2019.
  2. Hasegawa S, Kobayashi M, Arai R, Tamaki et al. Effect of early implementation of electrical muscle stimulation to prevent muscle atrophy and weakness in patients after anterior cruciate ligament reconstruction. J Electromyogr Kinesiol. 2011; 21(4): 622-630.
  3. Gondin JCozzone PJBendahan D. Is high-frequency neuromuscular electrical stimulation a suitable tool for muscle performance improvement in both healthy humans and athletes? Eur J Appl Physiol. 2011; 111(10): 2473-87. doi: 10.1007/s00421-011-2101-2. 
  4. Billot MMartin APaizis CCometti CBabault N. Effects of an electrostimulation training program on strength, jumping, and kicking capacities in soccer players. J Strength Cond Res. 2010; 24(5): 1407-13. doi: 10.1519/JSC.0b013e3181d43790.
  5. Warren CDBrown LELanders MRStahura KA. Effect of three different between-inning recovery methods on baseball pitching performance. J Strength Cond Res. 2011; 25(3):683-8. doi: 10.1519/JSC.0b013e318208adfe.
  6. Neric FBBeam WCBrown LEWiersma LD. Comparison of swim recovery and muscle stimulation on lactate removal after sprint swimming. J Strength Cond Res. 2009; 23(9): 2560-7. doi: 10.1519/JSC.0b013e3181bc1b7a.
  7. Gerovasili V, Stefanidis K, Vitzilaios K, et al. Electrical muscle stimulation preserves the muscle mass of critically ill patients: a randomized study. Crit Care. 2009;13(5):R161. doi:10.1186/cc8123
  8. Deley GCometti CFatnassi APaizis CBabault N. Effects of combined electromyostimulation and gymnastics training in prepubertal girls. J Strength Cond Res. 2011; 25(2): 520-6. doi: 10.1519/JSC.0b013e3181bac451.


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