Study on change of rat soleus extensibility caused by reduction in joint movement with unweighting of the hind limbs.
Yuta Sato, Takeya Ono, Hideki Ishikura and 5 others
PMID 29410566WHAT IT FOUND
In rats, one week of hind-limb suspension plus ankle fixation caused greater ankle stiffness and soleus muscle resistance to stretching than fixation alone.
This suggests adding unweighting to immobilization may worsen contracture, but it is not patient evidence.
Key findings
01After one week, ankle dorsiflexion was 101.5 degrees with fixation alone and 74.6 degrees with fixation plus suspension.
02At the 10 mm lengthened position, soleus tension torque was 0.58 N with fixation alone and 2.13 N with fixation plus suspension.
03The soleus length-tension curve shifted further left with suspension plus fixation, and it resisted stretching earlier.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
This was a rat experiment, so it does not tell you what happens in a patient's ankle. The suspension group also had ankle fixation, so the study does not isolate the effect of unweighting alone. Only the soleus was tested; joint capsule, ligament, skin, and other muscles were not measured. There were only seven rats in each group and the study lasted one week. No treatment was tested, so it does not show that stretching, mobilization, or weight-bearing helps.
The easy way to misread this
Do not read this as evidence that a specific therapy prevents contracture in patients. It measured passive ankle stiffness and soleus muscle tension in rats after one week of fixation and unweighting. The suspension group also had ankle fixation, so it does not isolate unweighting alone.