Neuroprotective Effects of Exercise on the Morphology of Somatic Motoneurons Following the Death of Neighboring Motoneurons.
Cory Chew, Dale R Sengelaub
PMID 31286830WHAT IT FOUND
In rats, wheel running after some motor neurons were killed reduced loss of dendrites in surviving motor neurons, but did not prevent motor neuron death or muscle atrophy.
This is a cellular effect in rats, not evidence of improved human function.
Key findings
01After motoneuron death, exercise reduced dendritic length loss to 28%, compared with 64% in saporin animals that did not exercise, and exercised animals had 97% longer dendrites than saporin animals that did not exercise.
02Exercise did not prevent the 21% motoneuron reduction or the 62% muscle weight loss after saporin injection.
03The maximum distance of dendrites outward and along the spinal cord did not differ across groups.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The study was done in male rats, not in people, so it does not show that exercise helps patients with motor neuron disease, spinal cord injury, or nerve root injury. The outcome measured was motoneuron dendrite structure, not movement or functional recovery in patients. The rats exercised voluntarily in running wheels for four weeks; this is not a prescribed therapy dose that a therapist could transfer to a patient. The number of animals was small, and group sizes changed between analyses because some tissue samples were compromised. Exercise did not prevent motoneuron death or atrophy of the injected muscle, so the finding is limited to surviving motoneuron dendrites. The Discussion's suggestion that this may lead to physical therapy regimens is future speculation, not a result of this study.
Declared interests
The authors declared no conflict of interest. The article is listed as supported by NIH extramural research.
The easy way to misread this
Do not conclude that exercise protects motor neurons or improves function in patients. This study measured dendrite length in rats after toxin-induced motor neuron death, and exercise did not prevent motor neuron loss or injected muscle atrophy.