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1st Feb

2012

Weight Pulleys Superior to Elastic Bands

Elastic bands or tubing are frequently given to patients after injuries and even surgeries, such as shoulder tendinitis or rotator cuff repair. Although such bands are very inexpensive and simple to set up, they have a number of shortcomings, which can have significant negative effects on the injured or healing tissues.

Following injury or surgery, or whenever there is significant pain, tissues often have poor tolerance to strain. There is typically protective muscle guarding present, which reduces the circulation and oxygen delivery to the muscle and tendon. There may also be swelling, inflammation and waste products present. An operated joint or tendon can have decreased tolerance to compression or strain for quite some time after the surgery. It is important not to exercise the tissue against too much resistance during this time.

In the acute stage, exercises should be performed in a way to best provide oxygen to the tissues, to reduce swelling and to stimulate tissue metabolism. This is best done by initially performing a motion slowly and using light enough resistance that the motion can be performed at least 25-30 times. This means that the resistance must be less than 50-60% of the weight that you can overcome once.

If the exercise resistance exceeds this level at any given point through range of motion, the muscle fibers quickly go into oxygen debt. This results in increased muscle guarding and pain, reduced tissue metabolism, and build up of waste products, and often an increase in tissue inflammation. This would prolong the recovery and jeopardize healing after an injury.

All skeletal muscles can generate the greatest strength close to the point where a joint is in its middle of range of motion. The muscle is weaker towards the inner and outer ranges of motion. Therefore, in early rehabilitation it is crucial to provide the muscle with the most resistance in the middle of range of motion, and less resistance at the beginning and at the end of the motion.

Weight pulley systems work well in this regard, since the angle of pull can be set up so that the resistance corresponds closely to how strong the muscle is at each point of the range of motion.

Elastic bands develop more tension the farther we move, and therefore will produce higher resistance on the muscle at the end of motion, than would the weight pulley. This is particularly true with a short band. Therefore, the resistance at the end of motion easily becomes excessive. The only way to avoid this is to use so little tension on the band in the beginning of the motion that it does not produce any measurable physiological effect early in the motion, therefore making the exercise ineffective. Furthermore, there is no exact way to measure how much tension is being applied, whereas with a pulley, this is determined by the specific weight used, and speed of motion. Research has also found elastic resistance to produce less increase in muscle mass and strength.

Although we use pulleys for most of our exercises, occasionally we choose to use elastic tubing, for practical reasons or because of the type of exercise that it is being used for.

Best wishes,

Gunnar

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