TENS & Pain Management
- Electronic Muscle Stimulation
Percussion Therapy & Muscle Recovery
Effectiveness of Transcutaneous Electrical Nerve Stimulation for Treatment of Hyperalgesia and Pain
Transcutaneous electrical nerve stimulation(TENS) is a commonly used nonpharmacologic and noninvasive treatmentfor pain. Although a number of clinical studies show the effectivenessof TENS for pain, there is still much controversy over which conditionsto treat with TENS and the adequate parameters to use. Prior reportsshow that TENS reduces pain through both peripheral and centralmechanisms. Centrally, sites in the spinal cord and brainstem thatutilize opioid, serotonin, and muscarinic receptors are activated byTENS. Peripherally, at the site of TENS application, opioid and α-2noradrenergic receptors are involved in TENS-induced analgesia [1•].The purpose of this review is to update the reader on the latestliterature concerning TENS: basic science, experimental pain, clinicaltrials, and systematic reviews.
TENS is the application ofelectrical current through electrodes placed on the skin for paincontrol. It can be applied with varying frequencies, from low (< 10Hz) to high (> 50 Hz). Intensity may also be varied from sensory tomotor intensities. Sensory intensity is when the patient feels a strongbut comfortable sensation without motor contraction. High intensityusually involves a motor contraction but is not painful. In general,higher-frequency stimulation is delivered at sensory intensity, andlow-frequency stimulation is delivered at motor intensity. Priorliterature from our laboratory shows that, regardless of intensity,different frequencies activate central mechanisms to produce analgesia.Specifically, we show that low-frequency TENS activates μ-opioidreceptors in the spinal cord and the brainstem, whereas high-frequencyTENS activates δ-opioid receptors in the spinal cord and the brainstem [2–4].Subsequent studies have investigated the role of serotoninergic,noradrenergic, muscarinic, and γ-aminobutyric acid (GABA)-ergic systemson the analgesia produced by both low-frequency and high-frequency TENS.
Theterms “hyperalgesia” and “allodynia” are widely used in the followingtext. Hyperalgesia is an increased pain sensitivity to a peripherallyapplied stimulus .Primary hyperalgesia is an increased pain sensitivity at the site ofinjury, which is thought to mirror changes in the peripheral nervoussystem. Secondary hyperalgesia occurs outside the site of injury, and itis thought to be mediated by changes in the central nervous system. Weand others have tested the effectiveness of TENS on a variety ofmeasures of both primary and secondary hyperalgesia. Allodynia isdefined as pain in response to a normally innocuous (nonpainful) stimulior activities that are thought to be mediated by changes in the centralnervous system, where activation of a peripherally locatednonnociceptor is perceived as painful.
Neuromuscular Electrical Stimulation for Treatment of Muscle Impairment
Purpose: In response to requests fromphysiotherapists for guidance on optimal stimulation of muscle usingneuromuscular electrical stimulation (NMES), a review, synthesis, andextraction of key data from the literature was undertaken by sixCanadian physical therapy (PT) educators, clinicians, and researchers inthe field of electrophysical agents. The objective was to identifycommonly treated conditions for which there was a substantial body ofliterature from which to draw conclusions regarding the effectiveness ofNMES. Included studies had to apply NMES with visible and tetanicmuscle contractions.
Method: Four electronicdatabases (CINAHL, Embase, PUBMED, and SCOPUS) were searched forrelevant literature published between database inceptions until May2015. Additional articles were identified from bibliographies of thesystematic reviews and from personal collections.
Results:The extracted data were synthesized using a consensus process among theauthors to provide recommendations for optimal stimulation parametersand application techniques to address muscle impairments associated withthe following conditions: stroke (upper or lower extremity; both acuteand chronic), anterior cruciate ligament reconstruction, patellofemoralpain syndrome, knee osteoarthritis, and total knee arthroplasty as wellas critical illness and advanced disease states. Summaries of keydetails from each study incorporated into the review were alsodeveloped. The final sections of the article outline the recommendedterminology for describing practice using electrical currents andprovide tips for safe and effective clinical practice using NMES.
Conclusion: This article provides physiotherapists with a resource to enable evidence-informed, effective use of NMES for PT practice.
Comparison of Interventional Strategies to Improve Recovery after Eccentric Exercise-Induced Muscle Fatigue
Post-training recovery is currently oneof the main aspects to consider in physical conditioning, particularlyin the field of sports performance, because of its impact on injuryrisk, reduced sports performance, and other factors .Different techniques have shown certain positive effects in therecovery process, with proven effects such as reduction of delayed onsetmuscle soreness (DOMS), maintenance of sports performance, reduction ofpain and many others . These include manual therapy (MT) , mechanical vibration (MV)  or the foam roller (FR) .
MVcan reduce the tension on the muscle-tendon attachments that affect theviscoelastic component of these structures, leading to increased muscleperformance and flexibility, reducing muscle stiffness and increasingblood flow . Indeed, massage has been shown to prevent and decrease muscle pain .While MT is the most traditional technique, other treatments such as MVhave recently shown positive effects on muscle recovery, particularlyin reducing DOMS  and reducing serum creatine kinase concentrations . Thus, MV is now considered a therapeutic intervention technique for muscle recovery.
Percussiontherapy (PT) has been classified within this same line of vibrationtreatments, although it has been less researched despite having beendeveloped in 1931 by Fulford . The rationale for its application is based on MV as it is assumed that PT may optimize muscle tissue recovery. PT ischaracterized by deep tissue treatment (e.g., of both fascia and muscle)based on three concepts: amplitude, torque and frequency. Thefrequencies are proposed with different objectives and with theintention of covering the needs of different patient or athleteprofiles. The benefits derived from their use include reduced pain,increased blood flow, improved scar tissue, decreased lactate, reducedmuscle spasms, increased lymphatic flow, inhibition of the Golgi reflex,increased range of motion and improved recovery based on the principlesfor the treatment of fascial connective tissues [11,12].Thus, it seems that the use of percussion devices may support othertypes of interventions (e.g., MT) given their potential effect on thetonic vibration reflex , though further research is needed.
Inaddition, considering the current interest in new treatments toaccelerate muscle tissue recovery, both in high-level and amateurathletes, recent studies have proposed self-myofascial tissue releaseusing a FR. This treatment uses the subject’s own body mass to applypressure against the roller, which has been shown to be effective toreduce the perception of pain , decrease DOMS and prevent a decline in performance .
Inorder to objectively evaluate the effect of these therapies on therecovery of athletes (both acute and chronic), the application oftechnologies to assess the condition of muscle tissue is required, tochoose the application of one particular technique over another. Muscleassessment by tensiomyography (TMG) enables the non-invasive analysis ofseveral parameters associated with neuromuscular fatigue/recovery,including radial displacement (Dm), which is related to muscle stiffness,and contraction time (Tc), which is the time that elapses between 10%and 90% of muscle displacement and varies depending on the type ofmuscle fiber and degree of fatigue .Based on these considerations, the aim of this study was to evaluatethe effect of different recovery treatments (MT, MV, PT and FR) on thecontractile properties of skeletal muscle through TMG (Tc and Dm), afterperforming an eccentric overload training session. We hypothesizedsignificant changes in muscle recovery after the application of MT andPT in comparison to the other techniques.