The effects of cross-education on loss of muscle strength and knee function after ACL reconstruction

There is over 30% loss of voluntary muscle force in the operated leg after an
anterior cruciate ligament (ACL) reconstruction surgery. Patients could return
to sport or work sooner by minimizing muscle weakness. Imaging, brain
stimulation, and behavioural studies show that exercise a muscle in one limb
improves function of the same muscle in the other, non-exercised limb. The
possibility exists that XED can reduce strength and functional losses and help
ACL-reconstructed patients recover faster.

Primary Objective:
The aim is to compare the effects of rehab with standard care vs. standard care
plus XED on loss of muscle strength and function in the operated limb at the
end of phase I rehab after ACL reconstruction surgery.

This study will be a randomized clinical trial with two arms: standard care and
standard care plus XED. The standard care plus XED group will receive standard
care plus structured exercise training of the non-operated quadriceps muscle.
Measurements: 1) 1 week before surgery, 2) End of Phase I rehab at 4 weeks, and
3) 3 months after surgery 4) Minimum follow-up of 6 months follow. Primary
outcomes: a) Return to sport or work status at 6 months and b) Cincinnati Knee
Score. Secondary outcomes: hop test, balance, proprioception, force control,
maximal quadriceps torque, and gait quality.

The control group will receive standard care of ACL rehab and the other group
will receive standard care plus extra exercise training of the non-operated
leg.

The clinical tests are part of the standard patient care and require no extra
time or effort. Patients visit the Center for Human Movement Sciences one time
before ACL reconstruction surgery, one time 4 weeks after surgery, and for a
3rd and final time 6 months after surgery for about 1.5 hours. The laboratory
tests will measure each quadriceps muscle*s ability to produce and control
force in a standardized way. The force control task requires minimal effort to
aim at a target at a low force and match the target force as accurately and
steadily as possible. The maximal knee extension task is also a standard test
and consists of ~2-s-long efforts with 1-2 min of rest between contractions.
Muscle activation is measured during the quadriceps test by electrically
stimulating the quadriceps muscle through the skin. This peripheral nerve
stimulation causes the muscle to twitch, this can be more surprising than
painful. It can cause some momentary burning and tingling sensation. The
balance test requires the patient to hold his/her balance on a board. The
proprioception test measures the ability to sense the position of the leg
unloaded and requires minimal effort. Gait variability is measured during slow
walking on a treadmill and is a sensitive test of symmetry and neural control
of gait. Electromyography (EMG) of the quadriceps will be recorded. Therefore
the skin underneath the three electrodes will be shaved and cleaned. This may
cause some light irritation of the skin. There will be minutes of rest between
each test.