Study Design: Repeated-measures design comparing 7 static weight-bearing shoulder exercises.

Objective:The purpose of this study was to determine the demand on shoulder musculature during weight-bearing exercises and the relationship between increasing weight-bearing posture and shoulder muscle activation.
Background: Weight-bearing shoulder exercises are commonly prescribed in the rehabilitation of shoulder injuries. Limited information is available as to the demands placed on shoulder musculature while these exercises are performed.
Methods:Eighteen healthy college students volunteered for this study. Surface bipolar electrodes were applied over the infraspinatus, posterior deltoid, anterior deltoid, and pectoralis major muscles. Fine-wire bipolar intramuscular electrodes were inserted into the supraspinatus muscle. Electromyographic (EMG) root mean square signal intensity was normalized to 1 second of EMG obtained with a maximal voluntary isometric contraction (MVIC). Subjects were tested under 7 isometric exercise positions that progressively increased upper extremity weight-bearing posture.
Results: There was a high correlation between increasing weight-bearing posture and muscular activity (r = 0.97, p<0.01). There was relatively little demand on the shoulder musculature for the prayer and quadruped positions (2%-10% MVIC). Muscular activation was greater for the infraspinatus than for other shoulder muscles throughout most of the exercise positions tested.
Conclusion: These results indicate that alterations of weight-bearing exercises, by varying the amount of arm support and force, resulted in very different demands on the shoulder musculature. Specifically, the infraspinatus was particularly active during the weight-bearing exercises used in this study.
J Ortho Sports Phys Ther, 2003;33:109-117. Key Words: electromyography, muscles, progressive resistive exercise, rehabilitation

Study Design: Descriptive study employing cadaver dissection and measurement of posterior-anterior (PA) glide of the femoral head in the acetabulum.

Objective:To quantify PA glide of the femoral head in the acetabulum in a cadaveric sample.

Background: Posterior-anterior glide of the femoral head within the acetabulum is a joint mobilization procedure described in orthopaedic physical therapy texts, yet there is no published evidence that the joint structures of the hip allow such movement. This study attempted to quantify PA glide of the femoral head in the hip joints of embalmed cadavers.

Methods:Twelve hips, 3 male and 9 female, from 8 embalmed cadavers were employed in this study. Hips were dissected to the level of the joint capsule and a metal rod inserted through the femoral neck served as a mobilizing handle. A load cell was installed into this handle so that mobilizing forces could be monitored. A dial gauge, which recorded displacement of the femoral head, was mounted to the pelvis via bone pins and an external fixator.

Results: Using mobilizing forces of 89, 178, 267, and 356 N, mean femoral head displacements of 0.57, 0.93, 1.20, and 1.52 mm were recorded. Within the 89-N trials, PA displacement ranged from a minimum of 0.04 mm to a maximum of 1.54 mm. Within the 356-N trials, PA displacement of the femoral head ranged from a minimum of 0.25 mm to a maximum of 2.90 mm.

Conclusion: In an embalmed cadaveric model, measurable PA glide of the femoral head within the acetabulum does exist and it is highly variable between individuals.

J Orthop Sports Phys Ther, 2003;33:118-125.

Key Words: accessory movement, cadaver hip joint, joint mobilization, posterior-anterior glide

This case report involving a 20-year-old male in the military serves as a reminder that not every individual presenting with musculoskeletal dysfunction has a simple uncomplicated musculoskeletal problem. Always consider acute exertional rhabdomyolysis (AER) as a differential diagnosis in patients who have performed intense exercise recently and are now complaining of muscle pain and weakness, especially if they have any of the AER risk factors discussed in this report (poor physical condition, exercising in a hot, humid environment, and poor fluid intake). These patients have an excellent prognosis if AER is caught early and treated aggressively. However, serious complications can occur if AER is overlooked or dismissed as delayed onset muscle soreness.

J Orthop Sports Phys Ther. 2003;33(3):104-108.