Table 3.

Summary of the Literature and Recommendations for Use of NMES or EMG-NMES for Wrist and Finger Extension

Indication	Parameter Recommendations	Outcome Measures Demonstrating Benefit
Wrist and finger extensor weakness	Electrode placement: Both recording EMG and stimulating electrodes were placed just distal to common extensor origin and halfway down the extensor surface of the forearm (on extensor carpi ulnaris, extensor carpi radialis, or both, aiming for a neutral position of the extended wrist in terms of radial and ulnar deviation) Body and limb position: patient seated, elbow flexed 90°, forearm pronated NMES waveform: asymmetric biphasic PC Frequency: 30–40 Hz to produce tetany32–39 Pulse duration: 200 μs32,33,39–41 or 300 μs37,38,42–44 Current amplitude: individual maximum tolerated intensity; trying to achieve full wrist and finger ext Work–rest cycle: 10:30–60 s to avoid muscle fatigue Treatment schedule: average 30 min/d33,34,37–39,44 Session frequency: 5 d/wk33,38–40,43–46 over 4–8 wk;32,33,37,38,40,43,45,46 extra wk may be required if applied>6 mo post-stroke	Increased muscle recruitment32 Increased wrist and finger extension33,34,37,38 Increased grip strength37,38,47 Increased wrist ROM33,38,43 Reduced flexor spasticity and increased reach32,44 Increased cortical activation39 Improved function (e.g., B&B,34,39 UE F-M,35,40,41,44 Barthel Index38,43,44)
Rationale for recommended NMES protocol	EMG can be used in combination with NMES to detect and encourage voluntary movement and patient involvement. At an EMG threshold preset by the clinician, NMES stimulates contraction of the wrist extensor group and moves the wrist and hand through a functional range. Adding EMG to NMES protocols will require the patient to initiate the contraction; however, several studies have not shown superior outcomes when comparing EMG-NMES with NMES alone.32,41,48 Electrodes placed over the wrist and finger extensor group using biphasic PC applied using small, portable devices is sufficient to move the wrist into at least 30° ext, without excessive finger ext, to allow finger grasping. Adding a second channel of electrodes on wrist flexors to stimulate wrist extensors and flexors alternately did not produce better clinical outcomes.49 Pulse frequency should be set to the normal recruitment rate of forearm muscles (30–50 Hz); although higher frequency may produce greater muscle force, the muscle will tend to fatigue more quickly and limit total session duration. Comparison of high- (40 Hz) and low- (20 Hz) frequency stimulation produced similar outcomes,50 whereas a doublet pattern of 20 Hz produced greater muscle force than continuous use of a single 20 Hz frequency.51 Work–rest cycles are set to minimize muscle fatigue and allow as many repetitions of the movement as possible in a single session. Cauraugh and colleagues34 showed that individuals with UE hemiplegia could move more blocks after receiving NMES with ON time set to 10 s than after a similar protocol with only 5 s ON time. Also, longer rest times between contractions will produce sustained muscle tension throughout the treatment session, whereas shorter rest times (5 or 10 s) will cause muscle fatigue and result in less voluntary muscle work over time.19 Treatment schedule: NMES and EMG-NMES applied to wrist and finger extensors for at least 30 min/d, 5 d/wk, for 4 wk can improve muscle strength. Most studies that produced benefit were applied 150–210 min/wk.32,33,37–39,41,44 Mangold and colleagues36 concluded that 12 sessions of NMES applied to the wrist extensors for 25–30 min/d, 4 d/wk, for 4 wk (120 min/wk) was insufficient to produce changes in any outcome for people who had recently sustained a stroke. Hsu and colleagues52 compared 30 and 60 min duration NMES for 5d/wk for 4 wk; a significant and similar improvement was detected in F-M and ARAT tests in both NMES groups compared with CON; therefore, no advantage was found for 60 min treatments. Most reports have suggested that functional changes are more likely when NMES is applied as soon after stroke as possible, when the patient has at least some ability to initiate hand and wrist movement (Chedoke-McMaster Stroke Assessment stage 5 of recovery).
Physiological effect of NMES	NMES and EMG-NMES applied to the wrist extensors can improve upper limb function by increasing grip and wrist extensor strength and improving active ROM of the wrist and hand.29,53 Increased cortical activity detected using fMRI54 and transcranial magnetic stimulation tests55 after NMES application to wrist extensors suggests that this treatment can enhance neuroplasticity and improve motor relearning after stroke. The effect of NMES on wrist flexor spasticity is not yet clear.
Critical review of research evidence	Studies included in Table 4 evaluated the effect of adding NMES or EMG-NMES to a conventional rehab programme; in all but three studies,32,45,46 significant improvement in outcomes was detected. NMES or EMG-NMES improved grip and wrist extensor strength in three studies33,37,38 and increased active ROM of the wrist.33,38,43 NMES-induced improvements in function were reported in 12 of the studies in Table 4. Differences in functional outcome between NMES and control treatments were detected using F-M,40–42,44 B&B,34,39 and Barthel Index,38,43,44 whereas MAS,32,34,45 FIM,30,38 and ARAT38,46 were seldom associated with change. Improvements in arm function persisted 32 wk37 and 6 mo14 after the end of NMES. 7 SRs22,23,29,53,56–58 examined the effects on UE impairments, activity, and function of applying NMES and EMG-NMES to the wrist extensors post-stroke. Inclusion criteria were different for each SR, with the result that no 2 reviews included the same group of studies; thus, it is not surprising that pooled findings resulted in contradictory conclusions. There are commercially available devices with pre-positioned EMG and NMES electrodes that allow for quick patient set-up or self-administration by the patient for home-based therapy (e.g., NESS Handmaster,59 Automove).49,55,60,61 More complicated computer-programmed, multi-channel devices that sequentially activate muscles to cause combined movements of the arm and hand are also available. NMES has also been applied in combination with other therapies such as bilateral movement,62 positional feedback, and robotic powered devices;63 however, the added benefit of these complicated and expensive devices has not been shown.57,64 Patients who elect to use a device that incorporates EMG and NMES should consult a qualified therapist to fit the device properly and train them in how to use it safely and effectively. There are conflicting results regarding the length and extent of carry-over of the benefits produced by NMES and EMG-NMES treatment (see Table 4).32,35,37,38,41,44 Persch et al.65 evaluated patients who had received 12 wk of NMES to wrist extensors and hand using a neuroprosthesis (Bioness H-200) and showed that functional improvements (ARAT, MAS, F-M) were retained 3 mo after ending the intervention; there are also studies that suggest functional gains are retained up to 9 mo after NMES intervention.41,44 Benefit has been shown for patients who had sustained a stroke>1 yr before NMES initiation;34,39 however, Hsu and colleagues66 studied the response of 90 stroke survivors to 4 wk of NMES and found greater time since stroke and stroke severity were significant predictors of failure to improve on ARAT scores post-intervention.

NMES=neuromuscular electrical stimulation; EMG=electromyography; PC=pulsed current; ROM=range of motion; Hz=Hertz (cycles per second); ext=extension; B&B=Box & Block Test; UE=upper extremity; F-M=Fugl-Meyer; ARAT=Action Research Arm Test; CON=control; fMRI=functional magnetic resonance imaging; rehab=rehabilitation; MAS=Motor Assessment Scale; SR=systematic review.