The Right Leg’s Connected to the … Left Leg?

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Rehabilitation of any injury or condition is a multifaceted process that requires attention to every aspect related to a successful recovery. One of the factors often overlooked is the maintenance of conditioning on the non-affected side. What many individuals, including coaches and clinicians, often fail to appreciate is the fact that training the non-injured side of the body can lead to a faster and more complete recovery, through a process known as cross education.

 

Cross education (also referred to as “cross transfer”, “interlateral transfer”, “cross limb transfer”, “contralateral training effect”, and “interlimb transfer”) was first referred to in the literature in 18941 and has been thoroughly investigated in over 20 clinical trials. It is basically the phenomenon whereby training one side of the body leads to strength changes on the opposite side.

 

Broadly speaking, the two main mechanisms by which force production capacity can be improved are 1) changes in the muscular tissue and 2) changes in the nervous system, or put more simply, improvements in the hard-wiring to the muscles. These nervous system changes take place at numerous different sites, including the brain itself. As you are probably aware, there are two hemispheres of the brain. These two hemispheres are linked by numerous structures, in particular an important bridge called the corpus callosum. These structures allow for communication between the two hemispheres, and for the benefits of training stress to be shared between both sides of the body. Essentially the brain is not smart enough to figure out where the training stimulus is coming from and as a result makes both sides of the body stronger.

 

Studies have shown strength gains in the non-trained limb of up to 77% of the trained side2. Amongst the research siting evidence of it’s effectiveness the most relevant to rehabilitation professionals are the three studies showing increased strength and a maintenance of muscle mass on the opposite side even when the limb was immobilised3,4,5. Whilst these studies haven’t been repeated on injured individuals, it does suggest that if we can maintain strength training on the opposite side we can potential ward off some of the strength and muscle mass losses that inevitably occur following injury, and therefore optimise the rehabilitation process.

 

There are other obvious benefits to this approach. Often when an individual is injured they cease all types of activity, either due to normal exercise habits being broken, or simply due to a loss of motivation. Some people also falsely believe that training the uninjured side will cause them to become “unbalanced”. Allowing training on the uninjured side will provide more exercise options, allowing maintenance of all the positive effects that occur through exercise, as well as continuing the social interaction that often accompanies physical activity.

 

At Club 360, our approach to rehabilitation is to focus on what an individual can do rather than what they can’t, and we look to take any opportunity to keep our patients as active as possible. The cross education effect gives us yet another reason to push forward with this approach.

 

References

 

  1. Scripture, E. W., Smith, T. L. & Brown, E. M. On the education of muscular control and power. Stud Yale Psychol Lab 2, 114–119 (1894).
  2. Hortobágyi, T., LAMBERT, N. J. & HILL, J. P. Greater cross education following training with muscle lengthening than shortening. Med. Sci. Sports Exerc. 29, 107–112 (1997).
  3. Farthing, J. P., Krentz, J. R. & Magnus, C. R. Strength training the free limb attenuates strength loss during unilateral immobilization. J. Appl. Physiol. 106, 830–836 (2009).
  4. Farthing, J. P. et al. Changes in functional magnetic resonance imaging cortical activation with cross education to an immobilized limb. Med. Sci. Sports Exerc. 43, 1394–1405 (2011).
  5. Magnus, C. R., Barss, T. S., Lanovaz, J. L. & Farthing, J. P. Effects of cross-education on the muscle after a period of unilateral limb immobilization using a shoulder sling and swathe. J. Appl. Physiol. 109, 1887–1894 (2010).

 

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