Electrical stimulation of the upper limb in stroke: stimulation of the extensors of the hand vs. alternate stimulation of flexors and extensors. (2004)

Abstract
OBJECTIVE:
To investigate whether there is a difference in functional improvement in the affected arm of chronic stroke patients when comparing two methods of electrical stimulation.

DESIGN:
Explanatory trial in which 30 chronic stroke patients with impaired arm function were randomly allocated to either alternating electrical stimulation of the extensor and flexor muscles of the hand (group A) or electrical stimulation of the extensors only (group B). Primary outcome measure was the Action Research Arm test to assess arm function. Grip strength, Motricity Index, Ashworth Scale, and range of motion of the wrist were secondary outcome measures.

RESULTS:
Improvement on the Action Research Arm test was 1.0 point in group A and 3.3 points in group B; the difference in functional gain was 2.3 points (95% confidence interval, -1.06 to 5.60). The success rate (i.e., percentage of patients with a clinically relevant improvement of >5.7 points on the Action Research Arm test) was 27% in group B (four patients) and 8% in group A (one patient). The differences in functional gain and success rate were not statistically significant, neither were the differences between the two groups on the secondary outcome measures.

CONCLUSION:
The difference between the two stimulation strategies was not statistically significant.

My comments:

I came across this article as I was reading up on EMS methods for arm and hand function for in patients with lost function due to lack of strength and/or spasticity post stroke. The way it was cited in other journals was as evidence that alternately stimulating the wrist and finger flexors (often spastic) with the wrist extensors didn’t work any better than just stimulating the extensors all by themselves. What I didn’t expect to find, and what wasn’t clear in the abstract (I hate that), was that neither protocol resulted in statistically significant or clinically relevant improvements. The exact quote, from the article was:

“Neither the difference between the groups nor the improvement in the group that received ES of the extensor muscles only exceeded the minimal clinically important difference of 10% (i.e. 5.7 points on the ARA test).”

I thought that particularly interesting because when googling the retail price of the Ness Handmaster, I get a retail price of $6200-$6800, which I thought was on the pricey side for an EMS machine for which similar parameters can be had in the $150 range. While I think the Ness Handmaster uniquely pricey for what it was, I was surprised it didn’t work better. Looking at the parameters, which weren’t entirely clear, I thought they leaned towards too much electric stimulation rather than too little. Subjects started with 20 minutes of EMS, 3 times per day, and worked up to 60 minutes with a duty cycle of 40%. Telling me the duty cycle is 40% doesn’t tell me what the actual on and off times were (note to researchers, just report the on and off times, plus any ramp info). However, in comparison, my “go to” strengthening program has a 16.6% duty cycle, which is 10 seconds on 50 seconds off, and I run that program for just 10 minutes, usually 3 times per week. To equate a 40% duty cycle with a 10 second on period, the rest would only 15 seconds. So their treatment time started at double mine, worked to 6 times mine, and instead of training 3 times per week, they were training 3 times per day. That’s A LOT of stimulation and at least when comparing to what is generally used in the training for strength and conditioning for athletes, sounds like it might be too much.

My other thought on the study was about how they alternated stimulation of the wrist flexors and extensors. If I had my druthers, I would have stimulated them concurrently so that the extensors would balance out the extensors. My reasoning being that doing so, you could increase the intensity of each with lesser strain on the wrist and finger joints so that both muscle groups could work up to higher electric stimulation intensities. Likely, I would have used a mesh glove or rubber carbon gripper electrode on channel 1, combined with the other electrode in the pair being a large ~3.5″ rubber carbon one on the forearm flexors, and then put both electrodes of channel 2 (using rubber carbon electrodes) on the wrist extensor muscles. My reasoning would be that the gripper/glove would better hit the hand intrinsic muscles, while the double up of large 3.5″ electrodes on the wrist extensors would help them balance out the increased muscle mass and spasticity of the wrist flexors.

I’m only recently starting to look into the data for EMS for restoring function post stroke, and from the reviews I have read there is a lot of research that shows it works. Perhaps this was a uniquely poor finding, for reasons which are potentially apparent as I talked about above. However, I’ll be looking at future papers with a bit more of a skeptical eye as this one wasn’t cited with the utmost in clarity.