J Orthop Sports Phys Ther 1992;16(3):108-113.

Key Words: electromyography, muscle cocontraction, stairstepping

Although lower extremity immobilization, including restricted knee flexion, is commonly used in rehabilitation, the effect of angle of knee restriction and walking speed on the vertical ground reaction forces during gait is unclear. Force plate measurements were made on 36 healthy males walking at 3 different speeds when knee flexion was unrestricted and restricted to both 10 and 25°. Analysis of variance and post hoc analyses showed significant increases in 4 characteristics of the vertical ground reaction force in the restricted leg and in 2 characteristics in the unrestricted leg during walking with restricted knee flexion. Loading rate and unloading rate for the restricted leg and peak force for both legs showed significant speed-knee flexion restriction interactions. At the fast walking speed, 2 significant differences were found between knee flexion restrictions of 10 and 25°. The clinical implications of these findings are that restricted knee flexion during gait may significantly alter the forces applied to both lower limbs.

J Orthop Sports Phys Ther. 1997;25(4):236-244.

Key Words: ground reaction forces, knee restriction, gait

Foot orthotics have been used successfully in the treatment of musculoskeletal symptoms associated with structural variations of the foot. Their effectiveness has been primarily addressed through 2-dimensional, frontal plane motion studies of the subtalar joint in individuals considered "clinical pronators. " Recent evidence suggests that assessment of tibial axial rotation in combination with frontal plane analysis of calcaneal inversion/eversion may provide improved understanding of subtalar joint function. The purpose of this study was to examine the effects of semi-rigid foot orthotics on 3-dimensional lower limb kinematics in 20 recreational runners presenting with distinct structural foot characteristics. Radiographic measurements were used to classify subjects into a low or high rearfoot profile group. The results of the kinematic analysis showed a significant orthotic effect for rotations occurring from heel contact to peak tibial internal rotation, as well as in the coupling relationship between tibial axial rotation and calcaneal inversion/eversion. Both groups responded similarly with a mean reduction of 2° in tibial internal rotation. No differences were found for the frontal plane rotations for either group when orthotics were worn. The findings suggest that the maximum effect of orthotics may be realized in the first 50% of stance and related to the changes in tibial axial rotation.

J Orthop Sports Phys Ther. 1995;21(6):317-327.

Key Words: running, kinematics, foot orthotics

Abnormal scapular kinematics and associated muscle function presumably contribute to shoulder pain and pathology. An understanding of scapular kinematic and electromyographic profiles in asymptomatic individuals can provide a basis for evaluation of pathology. The purpose of this study was to describe normal 3-dimensional scapular orientation and associated muscle activity during humeral elevation. Twenty-five asymptomatic subjects, 19-37 years old, were evaluated. Digitized coordinate data and surface electromyographic signals from the trapezius (upper and lower), levator scapulae, and serratus anterior were collected at static positions of 0°, 90°, and 140° of humeral elevation in the scapular plane. The scapula demonstrated a pattern of progressive upward rotation, decreased internal rotation, and movement from an anteriorly to a posteriorly tipped position as humeral elevation angle increased. Electromyographic activity of all muscles studied increased with increased humeral elevation angles. Differences between mean values at all elevation angles for all variables were significant (p < .05), except for the lower trapezius between the 90° and 140° humeral angles. The results of this study suggest assessment of scapular tipping and internal rotation as well as upward rotation may be necessary to understand pathologies of the shoulder that are related to abnormal scapular kinematics.

J Orthop Sports Phys Ther. 1996;24(2):57-65.

Key Words: scapula, electromyography, shoulder joint

Step ergometry has become a popular treatment mode in cardiovascular fitness and knee rehabilitation programs. The following study describes the effects of forward stair stepping at 35 and 95 steps/minute and forward and retrograde stair stepping at 60 steps/minute on the mean electromyographic (EMG) activity of the gluteus maximus, rectus femoris, vastus medialis, semimembranosus/semitendinosus, and gastrocnemius muscles. Thirty-three subjects without prior lower extremity pathology participated in the study. Analysis of variance was used to compare mean EMG activity during the knee extension phase of the different stepping conditions. Significant differences (p<.05) in mean EMGs of gluteus maximus, rectus femoris, vastus medialis, and gastrocnemius were noted across all cadences. The semimembranosus/semitendinosus EMG activity displayed a single significant difference between the cadences of 35 and 95. The comparison between forward and retrograde stepping identified only one significant difference in mean EMG (semimembranosus/semitendinosus). The effects of cadence on EMG activity should be considered when developing conditioning or rehabilitation programs for the lower extremity. Faster cadences result in increased peak activity of shorter duration for the gluteus maximus, quadriceps, and gastrocnemius. There is no apparent difference in EMG activity of the hamstrings due to cadence. Also, noting the minimal activation that occurs, stair-stepping exercise would not be recommended for strengthening of the hamstrings musculature.

J Orthop Sports Phys Ther. 1994;19(3):173-180.

Key Words: weight bearing, electromyography, stair stepping

Health and risk factor surveillance is a critical aspect of an effective ergonomics process. Physical therapists are becoming increasingly involved in many components of the ergonomics process, including health and risk factor surveillance. The purpose of this study was to develop and implement a multistaged active surveillance program for the management and control of cumulative trauma disorders. The surveillance program was established at 3 newspaper companies consisting of 1,150 employees. This study focused on the first 3 stages of the multistage surveillance model, which incorporates the use of symptom and job factor questionnaires, specific anatomical surveys, and clinical detection tests. The results of the study indicated that 1) musculoskeletal symptoms in the back, neck, and hands accounted for the majority of reported missed work among the newspaper workers; 2) production workers had a higher prevalence of musculoskeletal symptoms than office workers; and 3) the prevalence of probable carpal tunnel syndrome among the newspaper workers was 1.5%.

J Orthop Sports Phys Ther. 1994;19(5):267-276.

Key Words: ergonomics, cumulative trauma disorders, surveillance

Objectives: To determine whether differences in humeral translations exist between patients with shoulder impingement symptoms and an asymptomatic comparison group, and if so, to determine if shoulder range-of-motion (ROM) measures are associated with abnormal translations.

Background: Abnormal translations of the humeral head are believed to reduce the available subacromial space and to contribute to the development or progression of shoulder impingement symptoms. These abnormal translations have also been theorized to be related to tightness of the posterior capsule and decreased shoulder ROM.

Methods and Measures: Three-dimensional humeral translations were tracked in symptomatic construction workers and an asymptomatic comparison group while elevating the arm in the scapular plane under no-load, 2.3-kg, and 4.6-kg hand-load conditions. Between-group comparisons were made across 3 phases of motion (30°–60°, 60°–90°, and 90°–120°) and the association between humeral translations and cross-body adduction and shoulder internal rotation ROM measures were determined by Pearson correlation analysis.

Results: Persons with shoulder symptoms demonstrated small but significant changes in anterior-posterior translations of the humerus. These changes for the 90°–120° phase of humeral elevation were moderately negatively associated with available cross-body adduction ROM.

Conclusions: The identified kinematic deviations are consistent with possible reductions of the subacromial space. Further study of relationships between posterior capsule tightness, rotator cuff function, and abnormal humeral translations is warranted to better delineate underlying kinematic mechanisms that may contribute to shoulder impingement symptoms and to refine rehabilitation techniques.

J Orthop Sports Phys Ther. 2002; 32(6):248–259.

Key Words: biomechanics, kinematics, shoulder motion abnormalities