This document summarizes a study that investigated the effects of interval training on recovery from peripheral nerve injury in male and female rats. The key findings were: 1. Interval training effectively promoted motor axon regeneration and muscle reinnervation after injury in female rats, but not in male rats. 2. Restoration of the monosynaptic H reflex was enhanced by interval training in female rats, but not in male rats. 3. The efficacy of the H reflex, as measured by the ratio of Hmax/Mmax, was restored in both male and female rats by 10 weeks after injury with interval training. However, interval training did not enhance functional recovery of the M response or H reflex in male rats

1. • The ratio Hmax/Mmax is a measure of the efficacy of afferent neurons to recruit
motoneurons into activity via the H reflex.
• In all rats, this ratio is greatly exaggerated as muscles are re-innervated, but
declines rapidly thereafter.
• By 10 weeks after injury, ratio is restored in trained rats of BOTH sexes.
CONCLUSIONS
1. Interval training is effective in promoting motor axon regeneration and muscle
fiber re-innervation after peripheral nerve injury in female rats but not in male
rats.
2. Restoration of the monosynaptic H reflex is enhanced by interval training in
female rats but not in male rats.
3. Efficacy of the H reflex is enhanced in both male and female rats by interval
training.
Sex Differences in the Effect of Exercise on Recovery from Peripheral
Nerve Injury
Joshua Davila, Sohee Park, Poonam Jaiswal & Arthur W. English
Department of Cell Biology Emory University, Atlanta, GA 30322
BACKGROUND
• Only about 10% of patients ever achieve
full functional recovery from traumatic
peripheral nerve injury (Scholz et al J Reconstr
Microsurg. 25:339-44, 2009)
• Nearly 90% of traumatic peripheral
nerve injuries in the US occur in men.
• Moderate daily exercise applied after
traumatic peripheral nerve injury in
rodents results in a striking enhancement
of axon regeneration.
• Requirements for effectiveness of
exercise differ in axon regeneration in
male and female mice (Wood et al, Dev
Neurobiol. 72:688-98, 2012)
• Interval training enhances both axon
regeneration and functional recovery in
female rats but the effects of exercise in
male rats has not yet been investigated.
ACKNOWLEDGEMENTS
This research was supported by the Grant NS057190 to AWE from the
USPHS, the Emory Initiative for Maximizing Student Development under
award R25GM099644. The content is solely the responsibility of the authors
and does not necessarily represent the official views of the National Institutes
of Health.
This material is based upon work supported by the Howard Hughes Medical
Institute Science Education Program award #52006923 to Emory University.
Any opinions, findings, and conclusions or recommendations expressed in this
material are those of the author(s) and do not necessarily reflect the views of
the Howard Hughes Medical Institute or Emory University.
HYPOTHESIS
An exercise protocol (interval training)
that enhances functional recovery after
peripheral nerve injury in female rats will
be ineffective if applied to males.
METHODS
• Adult male Lewis rats
• EMG electrodes implanted to record
activity from the soleus (SOL) muscle
20 meters/minute
for 2 minutes Rest 5 minutes X4
Recordings
• Evoked EMG activity at weekly intervals
and compared to the baseline recordings
Exercise: Interval Training
• Five days per week for first two weeks,
starting three days after transection
Sensory
Axon
Motor Axon
SOLSOL
Cut &
Repair
2 ms
200µV
M Response H Reflex
• EMG activity evoked by stimulating the
tibial branch of the sciatic nerve and
assessed as direct muscle (M response)
& monosynaptic H reflex
*Data from Boeltz et al, J.Neurophysiol. 109;2645-57, 2013
RESULTS
• Unlike females, M Response recovery is
not accelerated in interval trained males.
• Recovery the same as untrained.
• H Reflex recovery is unaffected by
interval training in males.
N=4