Electromyographic normalization procedures for determining exercise intensity of closed chain exercises for strengthening the quadriceps femoris muscles.

The purpose of this study was to compare the electromyographic (EMG) amplitudes of the quadriceps femoris (QF) muscles during a maximum voluntary isometric contraction (MVIC) to submaximal and maximal dynamic concentric contractions during active exercises. A secondary purpose was to provide information about the type of contraction that may be most appropriate for normalization of EMG data if one wants to determine if a lower extremity closed chain exercise is of sufficient intensity to produce a strengthening response for the QF muscles. Sixty-eight young healthy volunteers (39 female, 29 male) with no lower extremity pain or injury participated in the study. Surface electrodes recorded EMG amplitudes from the vastus medialis obliquus (VMO), rectus femoris (RF), and vastus lateralis (VL) muscles during 5 different isometric and dynamic concentric exercises. The last 27 subjects performed an additional 4 exercises from which a second data set could be analyzed. Maximum isokinetic knee extension and moderate to maximum closed chain exercises activated the QF significantly more than a MVIC. A 40-cm. lateral step-up exercise produced EMG amplitudes of the QF muscles of similar magnitude as the maximum isokinetic knee extension exercises and would be an exercise that could be considered for strengthening the QF muscles. Most published EMG studies of exercises for the QF have been performed by comparing EMG amplitudes during dynamic exercises to a MVIC. This procedure can lead one to overestimate the value of a dynamic exercise for strengthening the QF muscles. We suggest that when studying the efficacy of a dynamic closed chain exercise for strengthening the QF muscles, the exercise be normalized to a dynamic maximum muscle contraction such as that obtained with knee extension during isokinetic testing.

Surface electromyographic analysis of the low back muscles during rehabilitation exercises.

STUDY DESIGN: Prospective, single-group, repeated-measures design. OBJECTIVE: To analyze the longissimus thoracis and lumbar multifidi muscle activity with surface electromyography (EMG) during exercises used in back rehabilitation programs. BACKGROUND: Physical therapists use a variety of exercises when rehabilitating patients with low back pain (LBP). EMG analysis of exercises can provide a measure of muscle activation so a clinician can have a better idea about the effect the exercise may have on the muscle for stabilization, endurance, or strength training. METHODS AND MEASURES: Surface EMG analysis of the muscle activity of the longissimus thoracis and lumbar multifidi was carried out bilaterally on 3 different experimental groups while performing a variety of exercises commonly used in low back rehabilitation programs. Groups 1 and 2 each had 30 subjects and group 2 had 29 subjects, ranging in age from 21 to 35 years. All EMG data during exercises were normalized to percent of the maximum voluntary isometric contraction (MVIC). RESULTS: The lumbar multifidus and longissimus thoracis muscles were most active, with EMG amplitudes of greater than 92% +/- 12% MVIC during prone lumbar extension to end range with resistance applied. Prone lumbar extension to neutral, resisted lumbar extension while sitting, and prone extension with the upper and lower extremities lifted (Superman exercise) produced EMG amplitudes ranging from a mean +/- SD of 77% +/- 13% to 82% +/- 12% MVIC. Exercises that produced EMG amplitudes of less than 50% MVIC were bridging exercises, the side-bridge exercise, and upper and lower extremity raises in either the prone or quadruped positions. CONCLUSION: The findings from this study may be helpful for physical therapists in selecting exercises when progressing patients with LBP from low-intensity exercises to those that require more muscle activity.

Electromyographic analysis of core trunk, hip, and thigh muscles during 9 rehabilitation exercises.

STUDY DESIGN: Prospective, single-group, repeated-measures design. OBJECTIVE: To identify exercises that could be used for strength development and the exercises that would be more appropriate for endurance or stabilization training. BACKGROUND: The exercises analyzed are often used in rehabilitation programs for the spine, hip, and knee. They are active exercises using body weight for resistance; thus a clinician is unable to determine the amount of resistance being applied to a muscle group. Electromyographic (EMG) analysis can provide a measure of muscle activation so that the clinician can have a better idea about the effect the exercise may have on the muscle for strength, endurance, or stabilization. METHODS AND MEASURES: Surface EMG analysis was carried out in 19 males and 11 females while performing the following 9 exercises: active hip abduction, bridge, unilateral-bridge, side-bridge, prone-bridge on the elbows and toes, quadruped arm/lower extremity lift, lateral step-up, standing lunge, and using the Dynamic Edge. The rectus abdominis, external oblique abdominis, longissimus thoracis, lumbar multifidus, gluteus maximus, gluteus medius, vastus medialis obliquus, and hamstring muscles were studied. RESULTS: In healthy subjects, the lateral step-up and the lunge exercises produced EMG levels greater than 45% maximum voluntary isometric contraction (MVIC) in the vastus medialis obliquus, which suggests that they may be beneficial for strengthening that muscle. The side-bridge exercise could be used for strengthening the gluteus medius and the external oblique abdominis muscles, and the quadruped arm/lower extremity lift exercise may help strengthen the gluteus maximus muscle. All the other exercises produced EMG levels less than 45% MVIC, so they may be more beneficial for training endurance or stabilization in healthy subjects. CONCLUSION: Our results suggest these exercises could be used for a core rehabilitation or performance enhancement program. Depending on the individual needs of a patient or athlete, some of the exercises may be more beneficial than others for achieving strength.

Normalization procedures using maximum voluntary isometric contractions for the serratus anterior and trapezius muscles during surface EMG analysis.

The serratus anterior and trapezius muscles are considered to be the only upward rotators of the scapula and are very important for normal shoulder function. A variety of methods have been used to produce a maximum voluntary isometric contraction (MVIC) of these muscles for normalization of EMG data. The purpose of this study was to quantify the surface EMG activity of the serratus anterior muscle and the upper, middle, and lower parts of the trapezius during 9 manual muscle tests performed with maximum effort in 30 subjects. It was found that no one muscle test produced a MVIC for all individuals. Therefore, to perform normalization within each subject, it is suggested that the 2 or 3 tests identified in this study that produce high levels of EMG activity for each muscle be performed. The scapular protraction muscle test that is often used to normalize data for the serratus anterior muscle produced relatively low levels of EMG activity and was not found to be an optimal test. Muscle tests in which an attempt was made to de-rotate the scapula from an upwardly rotated position produced much higher levels of EMG activity in the serratus anterior muscle.

Comparing the function of the upper and lower parts of the serratus anterior muscle using surface electromyography.

STUDY DESIGN: Prospective single-group repeated-measures design. OBJECTIVE: To use electromyographic (EMG) analysis during muscle testing to determine if there is a difference in function of the upper and lower parts of the serratus anterior (SA) muscle. BACKGROUND: The SA muscle is a very important scapular protractor and upward rotator. Authors have anatomically described the muscle as being divided into 2 or 3 parts, and have suggested that the upper part is more suited for protraction and the lower part for upward rotation of the scapula. METHODS AND MEASURES: Surface electrodes recorded EMG activity of the upper and lower parts of the SA muscle during 9 different muscle tests in 29 healthy subjects. RESULTS: Three muscle tests demonstrated significantly greater (P<.05) EMG activity in the lower part of the SA as compared to the upper part. There was no significant difference in the EMG activity of the upper and lower parts of the SA when the other 6 muscle tests were analyzed. CONCLUSION: When upward rotation was the primary position of the scapula during the muscle tests, the lower part of the SA was activated to a greater degree than the upper part. Muscle tests with maximum scapular protraction with varying degrees of upward rotation produced EMG activity with no significant difference when comparing the upper and lower parts of the SA. This information may be helpful for clinicians when muscle testing and developing exercise programs for the SA muscle.

Surface electromyographic analysis of exercises for the trapezius and serratus anterior muscles.

STUDY DESIGN: This study used a prospective, single-group repeated-measures design to analyze differences between the electromyographic (EMG) amplitudes produced by exercises for the trapezius and serratus anterior muscles. OBJECTIVE: To identify high-intensity exercises that elicit the greatest level of EMG activity in the trapezius and serratus anterior muscles. BACKGROUND: The trapezius and serratus anterior muscles are considered to be the only upward rotators of the scapula and are important for normal shoulder function. Electromyographic studies have been performed for these muscles during active and low-intensity exercises, but they have not been analyzed during high intensity exercises. METHODS AND MEASURES: Surface electrodes recorded EMG activity of the upper, middle, and lower trapezius and serratus anterior muscles during 10 exercises in 30 healthy subjects. RESULTS: The unilateral shoulder shrug exercise was found to produce the greatest EMG activity in the upper trapezius. For the middle trapezius, the greatest EMG amplitudes were generated with 2 exercises: shoulder horizontal extension with external rotation and the overhead arm raise in line with the lower trapezius muscle in the prone position. The arm raise overhead exercise in the prone position produced the maximum EMG activity in the lower trapezius. The serratus anterior was activated maximally with exercises requiring a great amount of upward rotation of the scapula. The exercises were shoulder abduction in the plane of the scapula above 120 degrees and a diagonal exercise with a combination of shoulder flexion, horizontal flexion, and external rotation. CONCLUSION: This study identified exercises that maximally activate the trapezius and serratus anterior muscles. This information may be helpful for clinicians in developing exercise programs for these muscles.

Examination of and intervention for a patient with chronic lateral elbow pain with signs of nerve entrapment.

BACKGROUND AND PURPOSE: Lateral elbow pain has several causes, which can make diagnosis difficult. The purpose of this case report is to describe the examination of and the intervention for a patient with chronic lateral elbow pain who had signs of nerve entrapment. CASE DESCRIPTION: The patient was a 43-year-old woman who had right lateral elbow pain for about 4 months, which she attributed to extensive keyboard work on a computer. She had a reduction in joint passive range of motion during "neural tension testing," an examination procedure to detect nerve entrapment. This sign, in combination with other findings, suggested that the patient had a mild entrapment of the deep radial nerve (radial tunnel syndrome). The patient was treated 14 times over a 10-week period with "neural mobilization techniques," which are designed to free nerves for movement; ultrasound; strengthening exercises; and stretching. OUTCOMES: The patient had minimal symptoms at discharge, was pain-free, and had resumed all activities at a 4-month follow-up visit. DISCUSSION: Neural tension testing may be a useful examination procedure and mobilization may be useful for intervention for patients who have lateral elbow pain.