TESTING INFRASPINATUS AND DELTOID MUSCLES WITH NEW TECHNIQUE TO DECREASE DELTOID ACTIVITY DURING TESTING USING EMG ANALYSIS

BACKGROUND

Muscle strength testing of an injured infraspinatus muscle (IM) is confounded by actions of synergistic muscles such as the posterior deltoid (PD).

HYPOTHESIS/PURPOSE

The purpose of this study was to describe a condition for testing of the IM that results in less EMG activity of the PD musculature. The researchers hypothesized that greater inhibition of the PD could be achieved through active adduction (AA), creating reciprocal inhibition of the PD.

STUDY DESIGN

Prospective cohort descriptive study.

METHODS

Thirty-four (19 females and 15 males) right-handed subjects between the ages of 22- 31 (mean 24.2 years + /- 6.2) with no previous history of shoulder surgery or pathology participated. Surface electrodes were placed over the muscle bellies of the IM and PD of the right shoulder along with a ground electrode over the C7 spinous process. EMG activity was recorded during resisted external rotation in four different testing conditions (seated active and passive adduction, and side-lying active and passive adduction). The order of test positions was randomly assigned, and each subject completed all four positions with appropriate rest. During AA conditions, subjects were asked to adduct the humerus against a sphygmomanometer (using 80% maximum force output) while maximal effort external rotation was manually resisted.

RESULTS

PD activity was significantly less during AA than with no AA (p<0.05) in both test positions. No significant difference occurred between IM EMG activity in the various test conditions.

CONCLUSION

The results of this study suggest that clinicians can reduce activity of the PD without reducing activity of the IM by using AA of the humerus before applying manual resistance to test the IM during manual muscle testing.

LEVELS OF EVIDENCE

1b.

Effects of functional electrical stimulation on gait recovery post-neurological injury during inpatient rehabilitation

This stage 2 trial investigated the therapeutic effect of single channel, peroneal functional electrical stimulation (FES) for improving gait and muscle activity in people with neurological injuries who were enrolled in an inpatient rehabilitation program. Twenty-six patients (16 male; M age = 51.3 yr., SD = 16.2; 2-33 days post-injury) completed the study. Participants were randomly assigned to an experimental group (n = 13) or control group (n = 13). The experimental group received FES and the control group received sensory stimulation during 45-min. gait training sessions three times a week for the duration of their stay in a rehabilitation facility (average of four sessions for both groups). Changes in gait speed, tibialis anterior muscle electromyography (EMG), and FIM™ locomotion scores were compared between groups. No significant differences were found, as both groups demonstrated similar improvements. The current results with this small sample suggest a low dose of gait training with single channel FES did not augment gait nor EMG activity beyond gait training with sensory stimulation; therefore, clinicians will likely be better served using a larger dose of FES or multichannel FES in this clinical population.