Hello again! We are back to talk more about estim and its effects on muscle denervation. Last time we discussed what a denervated muscle was, today, you are in for a real treat as we discuss what the best type of stimulation for denervated muscles is!
Not all stimulation patterns are equally effective in treating denervated muscles (Eberstein &Eberstein). To be effective, estim must stimulate all denervated muscle fibers! This would be very time consuming and somewhat near impossible without the use of implanted electrodes (Eberstein & Eberstein, 1996). For example, with 2 independent stimulation channels, electrodes are placed in the glutes, quadriceps, hamstrings, and triceps surae. Each of the muscle groups would need to be stimulated for 15-20 mins once or twice a day resulting in up to 2 hours of stimulation a day! So now, Q: how do we overcome this issue?
A: long stimulus duration pulses (Eberstein & Eberstein, 1996). In an interesting study performed by Mokrusch I et al, (1990), chronically denervated rabbit muscle was stimulated twice a day for 6 minutes by bidirectional long rectangular impulse of constant current to the point where muscle contractions were isometric, titanic and strong. The results produced a muscle with decreased fat and connective tissue, both, as you learned earlier, are found in chronically denervated muscle. Mokrusch et al (1990) believes that when using surface electrodes to produce a strong tetanic contraction on denervated muscle, that rectangular impulses were most effective because they encourage the longest possible current flow. Herbison et al (1971) did a study that supported this idea. A low impulse square wave on rat denervated muscle found no significant effect on the muscle, but, when long impulses were used, there was a significant increase in muscle weight.
On reflection of what we have read, we think that the results of these studies suggest that the best electrical stimulation to use for denervated muscles is a long pulse duration current. A few facts that lead us in this direction are that long pulse duration current works the best with surface electrodes and high frequency, which is needed to stimulate the denervated muscle fibers into titanic contraction.
So the question now is ‘what are the benefits of electrical stimulation and how do we keep it safe to use?’- Stay Tuned, Until next time!
Team North America signing off--
-Megs and Brooke
References:
Mokrusch, T., Engelhardt, A., Eichhorn, F., Prischenk, G., Prischenk, H., Sack, G., & Neundörfer, B. (1990). Effects of long-impulse electrical stimulation on atrophy and fibre type composition of chronically denervated fast rabbit muscle. Neurol. 237: 29-34
Eberstein, A. & Eberstein, S. (1996). Electrical stimulation of denervated muscle: is it worthwhile?. Med Sci Sports Exerc. 28(2)1463-1469.Kern, H., Hofer, C., Modlin, M., Forstner, C., Raschka-Hogler, D., Mayr, W. & Stohr, H. (2002). Denervated Muscles in Humans: Limitations and Problems of Currently Used Functional Electrical Stimulation Training Protocols. Artifical Organs. 26(3): 216-218
Herbison, G.J., Teng, C.S., Reyes, T., & Reyes, O. (1971). Effect of electrical stimulation on denervated muscle of rat. Arch Phys Med Rehabil. 52 : 516-522
Your writing gives us a nice development of the topic. The word for smoothly fused muscle fibre contractions is tetanic (as in tetany) not titanic (as in huge and sinking). cheers CY
ReplyDeleteAhem....thanks for fixing the spelling error in one place, but there are two other instances that cause a readers heart to sink!
ReplyDeleteA small question that is probably too late to answer (given we are post submission date) is what you mean by high frequency. My understanding is that one only needs low frequency to get the muscle contracting. CY