Muscle biopsies show that FES of denervated muscles reverses human muscle degeneration from permanent spinal motoneuron lesion. Kern H, Rossini K, Carraro U, Mayr W, Vogelauer M, Hoellwarth U, Hofer C. J Rehabil Res Dev. 2005 May-Jun;42(3 Suppl 1):43-53.
This paper presents biopsy analyses in support of the clinical evidence of muscle recovery induced by a new system of life-long functional-electrical-stimulation (FES) training in permanent spinal-motoneuron-denervated human muscle. Not earlier than 1 year after subjects experienced complete conus cauda lesion, their thigh muscles were electrically stimulated at home for several years with large skin surface electrodes and an expressly designed stimulator that delivered much longer impulses than those presently available for clinical use. The poor excitability of long-term denervated muscles was first improved by several months of twitch-contraction training. Then, the muscles were tetanically stimulated against progressively increased loads. Needle biopsies of vastus lateralis from long-term denervated subjects showed severe myofiber atrophy or lipodystrophy beginning 2 years after spinal cord injury (SCI). Muscle biopsies from a group of 3.6- to 13.5-year denervated subjects, who underwent 2.4 to 9.3 years of FES, show that this progressive training almost reverted long-term muscle atrophy/degeneration.
This paper is a bit of a follow up to my last one on using EMS for aerobic exercise, which I thought wasn’t particularly enjoyable for able bodied people, but might be just the ticket for those with injuries, particularly quadriplegia. I noted, however, that I did not expect the parameters used in that paper, or used in my own experiment, to work with paraplegia. The above paper however outlines the EMS parameters apparently being used successfully in ongoing experiments in Europe.
Classically, electrical muscle stimulation works well for upper motor neuron lesions typical of cervical spinal cord injury because the sensory and motor neurons between the muscles and the spinal cord is intact. What is missing is input from the brain turning on, or off in the case of clonus or spasticity, muscle contractions. Because the spinal cord ends at at ~L1-2, at which point spinal nerves exit the cord forming the cauda equina, an injury here disrupts the reflex arc between the leg muscles and the spinal cord. Since electric muscle stimulation (EMS) generally works by first activating the motor nerves, which then indirectly activate their respective muscles, and those nerves are damaged with lower motor neuron injuries, EMS is generally not effective for non-spastic paraplegia. NMES (neuromuscular electrical stimulation pays homage to the nerve-muscle distinction in it’s name. EMS seems to have won out in the terminology/popularity war. The presence of spasticity in the leg muscles, however, is an indication that those nerves are still intact and conventional EMS should then work. EMS with complete spinal cord injury has not been shown to restore function, but benefits do include preserving muscle health, increasing cardiovascular health, increasing bone mineral density, provide some muscle cushion to lessen risk of pressure ulcers. All are good things that would be great if they could be extended to those with lower motor neuron injuries.
So this group reportedly did it with four phases of treatment a custom made muscle stimulator with the following parameters used in each phase:
Phase 1: “Early Twitch Stimulation”
- Waveform: biphasic rectangular
- Pulse Duration: 150-200 ms (this is the MASSIVE difference) milliseconds (ms) rather than miroseconds (uS), 1 ms = 1000 uS and the strongest machine I know of available in the USA are the Globus units which top out at 450 uS. This machine in the same units has a pulse duration of 200,000 uS making it up to 444 times stronger.
- Intensity: up to 200 mA (my Globus, that I love, tops out at 120 mA)
- Rate: 2 Hz
- Duty Cycle: 4 seconds on, 2 seconds off, progressed to 5 on 1 off with 3-5 min stimulation with 1-2 min rest
- Treatment Length: 15 min per day
- Training Frequency: 5 days per week
- Training Length: few months
- Electrodes: large 180 cm squared, per their 2010 paper
Phase 2: “Late Twitch Stimulation”
- As above but with pulse duration shortened to 80-100 mS (still 80,000 to 100,000 uS)
Phase 3: “Burst Stimulation for Long-Term Spinal-Motor Neuron-Denervated Muscles”
- Pulse shortened to 40 mS (40,000 uS), frequency increased to 20 Hz, for 2 seconds on 2 seconds off, 3-5 min stimulation with 1 min rest 3-5 times a session, twice a day, 5 days per week.
Phase 4: “Force/Endurance Stimulation”
- After 9-12 months of training, they started doing tetanic contractions (frequency not given but I would guess >50 Hz would start to work), pulse width and intensity not given, for leg extensions for 8-12 reps with 4-6 sets, 2 minutes rest, twice a week with cuff weights progressing up to 5 kg.
The authors did note that with the extreme high levels of electric stimulation that there were risks of “skin lesions,” particularly in the early phases of rehabilitation. The results certainly sound promising, which is the good news. The bad news is that I have yet to see an EMS machine capable of delivering anywhere close to the above parameters in the USA.
As always, if you have any further questions or need for clarifications, please don’t hesitate to ask. Being aware that some of my blog ideas are contentious and occasionally a bit out of the field of my expertise, I encourage my readers to come forth with any questions/comments that are of interest or concern. Your comments are valued and welcomed.
Chad Reilly is a licensed physical therapist, located in North Phoenix, practicing science based medicine with treatment protocols unique and effective enough to proudly serve patients from Phoenix, Scottsdale, Mesa, Chandler, Tempe, Peoria, and Glendale.