Study Design: Single-session repeated-measures design.

Objectives: To define the resting position of the glenohumeral joint by investigating the magnitude of the anterior and posterior displacements of the humeral head and medial and lateral rotation ranges of motion (ROMs) of the glenohumeral joint at different abduction angles in cadaver specimens.

Background and Purpose: The resting position of a joint is the position in the joint’s ROM at which the joint capsule has its greatest laxity. It is frequently chosen as the position for assessing and treating joints with dysfunction. However, no study has been conducted to determine the resting position of the glenohumeral joint.

Methods:Seven freshly frozen cadaver shoulder specimens (age at time of death [mean ± SD] was 66.9 ± 2.5 years) were studied. Specimens were mounted on a system that uses computer-controlled hydraulics and motors to induce and monitor translation and rotation movements of the glenohumeral joint. The magnitudes of total displacement (DTotal) of the head of the humerus and total ROM (RTotal) of the glenohumeral joint were measured in the plane of the scapula at 0° (neutral), 30°, 40°, 50°, 60°, and the end range of glenohumeral joint abduction. The resting position was determined as the midpoint of the shared range of the 95% to 99.9% confidence intervals of the predicted abduction position where the peaks of displacement and rotation occurred.

Results: The DTotal measurements (mean ± SD) at 0°, 30°, 40°, 50°, 60°, and the end range of glenohumeral joint abduction were 30.53 ± 9.35, 44.87 ± 7.34, 45.35 ± 8.53, 43.99 ± 10.02, 39.63 ± 9.85, and 23.80 ± 10.42 mm, respectively. The RTotal measurements (mean ± SD) for the same positions were 67.15° ± 15.87°, 95.64° ± 24.26°, 98.88° ± 29.56°, 97.08° ± 30.17°, 90.91° ± 28.73°, and 63.48° ± 25.93°, respectively. The resting position was located at 39.33° ± 4.37° of glenohumeral abduction (45.13% ± 7.58% of the available abduction ROM). The resting position (Y) varied linearly with the maximum available abduction ROM (X) (Y=0.607X-13.120, R2=0.679, F=10.61, P=0.023). There was a main effect of joint position on both displacement (P<0.001) and rotation ROM (P<0.001).

Conclusion: In the plane of the scapula, the resting position of the glenohumeral joint (angle measured between the scapula and humerus) occurred at 39° of abduction (45% of the maximum available abduction ROM) and varied linearly with the amount of available abduction ROM. This finding suggests that in patients with glenohumeral joint hypomobility the resting position is located closer to neutral and that evaluation and treatment should be initiated accordingly at a smaller angle of abduction than the traditional resting position. Our data were derived from cadaver specimens, therefore, caution should be taken when generalizing the results of the present study to a patient population.

J Ortho Sports Phys Ther. 2002;32(12):605-612.

Keywords: glenohumeral joint, laxity, shoulder, range of motion, resting position

Study Design: A 2-factor (group and time) experimental design with repeated measures on time.

Objectives: To determine the effects of ankle cryotherapy on voluntary and resting motor function of the soleus over a 60-minute period. To determine if a relationship exists between changes in torque production and Hoffmann reflex (H-reflex) following ankle joint cryotherapy treatment.

Background: Controversy surrounds the use of cryotherapy prior to activity and rehabilitation. While cooling muscle may have a deleterious effect on motor function, cooling the joint may enhance motor function around the joint. The H-reflex is a good resting measure of motoneuronal activity. However, its relationship to voluntary activity is unknown.

Methods and Measures: Thirty subjects were pretested (baseline) for normalized H-reflex (defined as the ratio of maximum H-reflex [Hmax] to maximum direct motor response [Mmax]) and peak plantar flexion torque. A crushed ice bag was placed over the ankle of 15 subjects for 30 minutes. H-reflex and torque measurements were collected immediately following the cryotherapy treatment at 30, 60, and 90 minutes. Surface temperatures were recorded from the ankle and electrode site with each measurement interval.

Results: Both peak H-reflex and plantar flexion torque at 30, 60, and 90 minutes increased relative to baseline measurements. Each measurement was also greater than the corresponding control at 30,60, and 90 minutes. A weak correlation (r=0.38; P=0.036) existed between changes in H-reflex and plantar flexion torque at 30 minutes.

Conclusions: The soleus motoneuron pool is facilitated following a 30-minute crushed ice application to the ankle and over a 60-minute postcooling period. These data support the use of joint cooling prior to activity and rehabilitation.

J Orthop Sports Phys Ther. 2002;32(12):622-627.

Keywords: cyrokinetics, Hoffmann reflex, plantar flexion torque

This index includes all authors and co-authors of manuscripts published in the Journal during 2002.

J Orthop Sports Phys Ther. 2002:32(12):644-657.