Recent research has discussed the use of low-frequency electrical stimulation to increase blood flow by eliciting muscular contraction in soft tissues. This randomized clinical trial examined the efficacy of low-frequency electrical stimulation combined with stretching exercises and foot orthoses in individuals diagnosed as having plantar fasciitis for less than 6 months.
Twenty-six participants aged 18 to 65 years diagnosed as having plantar fasciitis were randomly assigned to two treatment groups: a control group receiving only stretching and orthoses and a treatment group receiving low-frequency electrical stimulation in addition to stretching and orthoses. To assess treatment response, a visual analog scale was used to determine first-step morning pain, and changes in daily activity levels were monitored by using a validated outcome measure. All of the participants were assessed before starting treatment, after 4 weeks of treatment, and 3 months after the conclusion of treatment.
Participants in the control and experimental groups demonstrated pain reduction and improvements in functional activity levels after 4 weeks and 3 months.
Regardless of whether low-frequency electrical stimulation was used as an intervention, the use of plantar fascia-specific stretching and prefabricated foot orthoses provided short-term (3-month) pain relief and improvement in functional activity levels.
McPoil and Cornwall were two of my favorite professors at NAU and most of what I know about foot anatomy and mechanics I learned from them. Both treatment groups wore the same foot orthotics, both did the same plantar fascia stretching protocol described by DiGiovanni, but one group also did low rate TENS to the bottom of the foot at a rate of 10 pulses per second and at an intensity such that they felt a “moderate contraction or pulsing action that was comfortable.” The TENS was performed once daily before they did their evening stretches. No additional data was given with regard to pulse width, or amplitude used.
The conclusion of the paper was that both groups improved, such that the effectiveness of the TENS treatment was questionable and there was no significant difference between the groups. However when I calculated the pain score improvement myself I found the TENS group decreased pain 35% at 4 weeks, compared to 23.9% in the control group, and at the 3 month follow up the TENS group pain was 68% improved while the control group was 54.1% improved. The P-value for the difference between groups was not given but knowing what I know about TENS, a greater number of subjects likely would have shown a statistically significant treatment difference, and maybe the same would have happened if the TENS intensity was increased. In the TENS research low or uncontrolled intensity TENS is often questionable with regards to pain reduction, but if the machines are turned up to the strongest comfortable current consistent pain reductions are often found.
Still I am not a biggest fan of TENS because good quality electric stimulation machines can also be programed to do electric muscle stimulation (EMS) parameters that increase muscle strength. I would be very interested in seeing this study repeated using to target the foot intrinsic muscles, known to be weak in those with plantar fasciitis. I currently prefer 10 seconds on, 50 seconds off for 12 minutes (10-50-12) with maximal pulse width and max tolerable amplitude using an electrode placement identical to that in this paper. Besides improved muscle strengthening, EMS parameters have been shown to be superior to TENS for pain reduction as well. The 10-50-12 EMS parameters would be almost identical to what world renowned sprint coach Charlie Francis favorite duty cycle (10-50-10) used for foot injuries in his sprint coaching book. I just like to add 2 extra minutes to my treatment to get the intensity of the machine where I want it. Also I would like to see the study repeated replacing DiGiovani’s stretches with comprehensive muscle strengthening program of the entire lower extremity. A recent study just found basic calf strengthening, which was far from comprehensive, superior to Digiovani’s stretches. In my physical therapy clinic the combination of EMS and strength exercises I am noticing acceleration in the rate of recovery in my plantar fasciitis patients, most of whom have tried various foot stretches, and orthotics for months with little or no relief.
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.