Effect of Cryotherapy on Neuromuscular Electrical Stimulation: A Review of the Literature

Neuromuscular electrical stimulation (NMES) has been shown to be an eff ective technique to strengthen muscle following musculoskeletal injury or surgery. A limitation of NMES is the discomfort caused by the strong electrical contractions required for eff ective strength gains. This article explores whether the application of cryotherapy over muscle aff ects the ability of the muscle to contract in response to NMES and whether the reduction in discomfort of the stimulus enables greater force production. Eleven studies that met the inclusion criteria were reviewed. This review found that short-duration application of cryotherapy can improve tolerance to strong contractions elicited by NMES for muscle strengthening; however, longerduration applications may aff ect muscle force production. More studies are needed to determine the eff ect of cryotherapy on force production of muscle during NMES and whether greater increases in strength can be achieved. Neuromuscular electrical stimulation (NMES) is a widely used intervention for rehabilitation of weak or damaged muscle. Studies support the use of this technique for strengthening muscle following ligament repairs of the knee and total knee joint arthroplasties.1-4 The typical clinical approach is to place electrodes on the skin overlying the motor points of the muscle, which are usually defi ned as the location over the muscle where the motor nerve to the muscle is most accessible. The intensity of the stimulation depends on the amplitude, duration, and frequency of the electrical pulses, or bursts. A high-amplitude, longpulse duration stimulus is required to achieve a contraction that is at least 50% of maximal voluntary contraction (MVC). This stimulus may not be tolerated by the patient. Farquhar and Snyder-Mackler5 identifi ed patient discomfort as the limiting factor in using NMES in clinical settings, especially “when high contractile forces are sought for strength training regimens.” Most clinical uses of NMES are for strengthening of weak or injured muscle. The use of NMES for uninjured individuals is uncommon because strength gains can be achieved by exercise programs without the use of NMES. Patient tolerance to NMES for muscle strengthening depends primarily on the type of electrical current chosen for the treatment and the patient’s pain coping style.5 Some patients can tolerate burst mode alternating current (Russian stimulation) NMES, whereas other patients prefer biphasic pulsed NMES. Pain coping style varies from those patients who focus on the discomfort of NMES and those who focus on the benefi ts of the treatment and are willing to tolerate discomfort. Patients who focus on the discomfort of NMES require a blunting strategy to decrease their perception of pain. Strategies for blunting the perception of pain can include distraction by listening to music or interventions that interrupt nociception to the central nervous system. Modalities such as cryotherapy applied during or prior to NMES may be an effective blunting strategy; however, decreasing the temperature of tissues overlying a muscle or of the muscle itself may affect the ability of NMES to achieve a muscle contraction. The effect of Dr Nolan and Dr Galantino are from the Physical Therapy Program, School of Health Sciences, The Richard Stockton College of New Jersey, Galloway; and Dr Buccafurni is from Fox Rehabilitation, Northfi eld, New Jersey. Received: January 4, 2011 Accepted: June 12, 2012 Posted Online: January 2, 2013 The authors have no fi nancial or proprietary interest in the materials presented