Cross Education of Muscles
What is cross education of muscles?
This phenomenon is being seen more and more within sport, rehabilitation and physiotherapy. This is a neurological process where you see strength within the untrained limb from training in a unilateral fashion. For example, if someone had one of their limbs in a cast it would be possible to train the uninjured limb and see strength adaptations within the limb in a cast. This has changed how physiotherapist and coaches look at rehabilitation.
How does it work?
As said above it is believed to be a neurological process. This is via the brains pathways that are used when unilateral exercise is performed as the primary muscles being stimulated will work the same muscles on the opposite side of the body. For example, performing a single leg raise on the right leg, the quadriceps are the primary muscles being worked, so this will correspond to the left quadriceps which is not be used so supporting muscles will not gain any effects.
What research has been done?
Cross education was first discovered in 1894 at Yale where strength gains were found in untrained limbs after performing unilateral training (Scripture et al.,1894). It is believed that the first truly controlled study was conducted in 2009 where they used a cast to immobilise the subjects left arm as they performed resistance training on the right arm. There were two groups, where one group did no training and the other performed resistance training. As predicted the cast group with no training had a decreases in strength of 14.7% whereas the opposite group saw no significant decrees in strength or atrophy. What this shows that your recovery can be improved during your healing phase.
How do you train in cross education fashion?
So with research continuing to determine what the perfect formula for cross education may be to realise its full potential, as the current belief is that unilateral training should be performed 2-3 times a week with a high load and low set repetitions with a significant rest period of 1 to 2 minutes between sets.
It is key to have the correct formula as you do not want to cause an imbalance between each muscle or limb therefore this is why high load / low repetition must be performed. High load is important to cross education of muscles as you need to create a big enough stimulus to engage neural driven motor pathways to activate the opposite limb.
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Scripture, E. W., Smith, T. L., and Brown, E. M. (1894). On the education of muscular control and power. Stud. Yale Psycol. Lab. 2, 114–119.
Farthing et al (2009). Strength training the free limb attenuates strength loss during unilateral immobilization. J Appl Physiol 106: 830–836,
