exercise is performed to 30° to 45° of knee flexion position. Then it is progressed by moving the patient’s body to a lower degree of knee flexion angle and increasing the number of repetitions (White, Di Stasi, Smith, & Snyder-Mackler, 2013). Postoperative hamstrings strength exercises involve concerns related to the ROM of the exercise for patients with concomitant meniscus injury or patients with additional PCL reconstruction surgeries, meniscus repair, or chondral surgeries. In these cases, the ROM might be limited to 90° for 6 to 8 weeks after surgery to prevent failure of these surgeries (Adams et al., 2012). In patients who had reconstruction surgery using hamstrings- gracilis autograft, the hamstrings strengthening exercises should not be initiated until 8 weeks after surgery to ensure tendon regrowth (Adams et al., 2012). Imbalanced quadriceps-hamstrings muscles strength was reported as a predictive measure to identify female athletes with high risk for ACL injury (Myer et al., 2010). Clinicians may consider providing balanced strength training to both the hamstrings and quadriceps muscles throughout the rehabilitative process. As a result, the hamstrings may be able to decrease the anterior tension load applied on the graft tissue during quadriceps activation. This might suggest assessing the strength difference between quadriceps and hamstrings muscles to determine patients’ readiness to return to preinjury activities and to ensure better outcomes. Neuromuscular electrical stimulation NMES is commonly used for treating quadriceps muscle inhibition and strengthening the quadriceps muscles following ACL injury and ACL reconstruction (Adams et al., 2012; Kim et al., 2010; Lynch et al., 2012; Rice & McNair, 2010; Williams et al., 2005). Electrical stimulation to increase quadriceps muscle strength is most beneficial when quadriceps weakness is due to arthrogenic muscle inhibition (Kim et al., 2010; Lynch et al., 2012; Rice & McNair, 2010). The NMES device provides an alternating electrical current that resembles the electrical current of action potential coming from the motor cortex. The electrical current will initiate an action potential in the nerve branches that innervate the quadriceps muscle. As a result, the muscle will develop an involuntary muscle contraction (Trimble & Enoka, 1991). Early incorporation of NMES into the treatment program after ACL injury or reconstruction surgery is recommended to avoid quadriceps muscle inhibition and its impact on the functional recovery (Rice & McNair, 2010). Administering strength training augmented with NMES after ACL reconstruction was shown to be more effective in improving the quadriceps strength compared to the strengthening training alone (Kim et al., 2010). Therefore, NMES training is recommended as an adjunct treatment for patients whose injured limb quadriceps muscles exert a maximum voluntary isometric force of less than 80% of the uninjured limb (Adams et al., 2012; Delitto et al., 1988; Snyder-Mackler et al., 1995; Snyder-Mackler et al., 1994). There is an inconsistency in the reported studies about the treatment parameters for NMES (treatment time, frequency, phase duration, and the on-to-off ratio). A systematic review suggests that a stimulus waveform of 1.0- to 2.5-kHz frequency alternating current, with a 2- to 4-millisecond burst, may yield the best torque output with the least patient discomfort (Kim et al., 2010; Ward, Robertson, & Ioannou, 2004). Gorgey and Dudley (2008) suggested that a pulse duration of 450 microseconds resulted with 38% higher knee extensor torque compared to a short-phased duration of 250 milliseconds. A commonly used NMES protocol consists of 10 electrically stimulated isometric contractions of the quadriceps muscles, with 10 seconds on and 50 seconds off, with a 2,500-Hz stimulus delivered at 75 bursts per second (Fitzgerald, Piva, & Irrgang, 2003; Lepley & Palmieri-Smith, 2013; Snyder-Mackler et al., 1994). The self-adhesive stimulating electrodes can be place on the vastus medialis distally and on the vastus lateralis proximally (Lepley & Palmieri-Smith, 2013; Snyder-Mackler et al., 1994).
For the NMES to be effective in improving the quadriceps muscle strength, high-intensity electrical stimulation up to the patient’s tolerance is recommended to be administered (Risberg, Lewek, & Snyder-Mackler, 2004). Fitzgerald and colleagues (2003) reported that electrical current amplitude for NMES must be equivalent to the electrical current needed to produce 50% of maximum voluntary isometric contraction of the reconstructed limb’s quadriceps muscle in order to improve the quadriceps muscle strength. NMES training can be performed on a dynamometer with the knee positioned between 60° to 85° of knee flexion position. This position is used to prevent overloading the new harvested graft tissue as an activation of the quadriceps muscle between 0° and 30° of knee extension induces an anterior displacement of the tibia (Figure 6; Delitto et al., 1988; Snyder-Mackler et al., 1995).
Figure 6: Neuromuscular Electrical Stimulation to Quadriceps Muscles Using a Portable Device
Note . From Western Schools, © 2018. NMES training can be incorporated in the first few days after injury or surgery in conjunction with a progressive quadriceps strengthening program to avoid quadriceps strength deficits and activation failure (Rebai et al., 2002). Patients with patellar tendon autograft may experience donor site pain during forceful quadriceps contractions with the knee is positioned at a high angle of flexion. If a dynamometer is unavailable, a modified NMES protocol can be used to produce similar results (Fitzgerald et al., 2003). The modified NMES protocol places the patient in a supine position with the knee in full extension. The NMES stimulus is the same as previously described. The intensity is set to maximum patient tolerance once a full, sustained, tetanic contraction (sustained muscle contraction without an interval of relaxation) of the quadriceps is achieved. One advantage of NMES is that it does not require delaying the training program until impairments have been resolved and can be used regardless of the presence of joint effusion or ROM limitation to restore normal quadriceps activation (Lynch et al., 2012). Once quadriceps muscle strength of the injured limb is greater than 80% of the uninjured limb, NMES can be discontinued and patients may continue with their progressive strengthening program without NMES (Adams et al., 2012). All patients are recommended to participate in a progressive strengthening program to maximize quadriceps strength and restore normal limb symmetry in quadriceps strength. Applying NMES in combination with high-intensity progressive quadriceps strengthening exercises results in greater strength improvement in ACL-deficient and ACL-reconstructed patients when compared with standard exercise alone (Kim et al., 2010).
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Book Code: PTNJ0824
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