In 2000/2001, 13% of Canadians suffered a unilateral injury (Stats Canada, 2004). According to research, the most common complications after immobilization of an injured limb are decreased range of motion, decreased strength and muscle atrophy (decrease in physical size of the muscle).
What is the non-injured limb doing during this time?
Generally speaking, when someone has an injury requiring immobilization, there is a decrease in overall activity. Here’s where Athletic and Physiotherapists can help! What if we actually increase the activity on the non-injured side?!?
The idea of strengthening the non-injured limb/joint to assist in the maintenance of strength and muscle size in the injured side is referred to as Cross Education.
Cross Education was first observed in 1894. To date, it is hypothesized that this phenomenon works due to changes in the neural networks of the brain, in the region responsible for motor learning. Even though the strength training is being performed on a single limb, a new motor pattern is created in the brain. Both sides of the body can access this motor program and therefore strength gains can occur on both sides.
Adverse Effects of Immobilization
After only nine (9) days of wearing a wrist cast, wrist flexion decreased 29.3%, and extension decreased 32.5%, when compared to the uninjured side (Miles et al, 1994). In another study by Trumble et al., 1994, it was found that wrist range of motion was still only 75% of the non-injured side three years post fracture. This same study noted that grip strength too remained altered, being only 69% of the strength of the non-injured side at the three year mark. A 15 – 36% decrease in strength after rotator cuff surgery and immobilization was noted after six to eight months in study performed by Binet et al., 2003, and five years after surgery, a decline in strength still remained (Rokito, 1999).
If this sort of significant change can occur in a week and a half, what does this mean for rehabilitation?
Current rehabilitation protocols after rotator cuff surgery do not begin basic strength restoration until the 6 – 12 week mark, when the sling is no longer worn. Protocol for wrist rehabilitation after fracture and immobilization does not call for strength exercises until 9 – 12 weeks post injury. Therefore, the detrimental effects of immobilization on strength have already set-in, significantly altering recovery from injury.
The Facts!
Current research on Cross Education has defined the following parameters when considering the use of this technique in a rehabilitation setting:
1) The magnitude of the Cross Education effect is directly related to the strength increase of the trained limb/muscle.
2) Effects are usually shown with a 3 -6 week training program, with exercises being performed daily.
3) Increases in muscle size will only occur on the trained side; the untrained side will, however, maintain its original size and will not continue to atrophy (shrink in physical size) with lack of use.
4) Effects are only shown between the same muscle groups i.e. left hamstrings to right hamstrings, not left hamstrings to right quadriceps.
5) Greater effects of Cross Education are shown if the exercises performed are novel or more complicated.
6) A larger increase in strength on the immobilized side will occur if the trained side is the person’s dominant limb
Using these principles, a rehabilitation program can begin from day one of an injury and could lead to a more complete recovery. Want more information? Contact the clinic, or schedule an appointment with Sherry!
References:
- Stats Canada. (2004). Injuries in Canada: Insights from the Canadian Community Health Survey
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- Rokito, A. S., Cuomo, F., Gallagher, M. A., Zuckerman, J. D. (1999). Long-term functional outcome of repair of large and massive chronic tears of the rotator cuff. J Bone Jt Surg, 81-A(7), 991-997.