Bryan Picco

INTRODUCTION Quantifying healthy shoulder motion enables comparisons to special (e.g. athletic, injured) populations and allows for the identification of mechanisms of diminished performance. Although previous work has documented shoulder motion using bone pins [1], the overall applicability is limited due to small sample sizes, and because the majority of shoulder kinematic studies utilize skin-mounted motion capture techniques for pragmatic reasons. Also, past investigations tend to focus solely on scapular plane abduction. This study generated an extensive collection of healthy 3-dimensional (3D) dynamic sternoclavicular (SC), acromioclavicular (AC), scapula-thoracic (ST), and glenohumeral (GH) kinematic profiles collected in multiple vertical movement planes utilizing skin-mounted shoulder motion capture.

Exerting manual forces is critical during occupational performance. Therefore, being able to estimate maximum force capacity is particularly useful for determining how these manual exertion demands relate to available capacity. To facilitate this type of prediction requires a complete understanding of how maximum force capacity is governed biomechanically. This research focused on identifying how factors including joint moment strength, balance and shoe-floor friction affected hand force capacity during pulling, pressing downward and pushing medially. To elucidate potential limiting factors, joint moments were calculated and contrasted with reporte joint strength capacities, the balancing point within the shoe-floor interface was calculated and expresess relative to the area defined by the shoe-floor interface, and the net applied horizontal forces were compare with the available friction. Each of these variables were calculated as participants exerted forces in a series o condition...

INTRODUCTION In a healthy shoulder, as the humerus elevates, the scapula rotates upward and tilts posteriorly. Factors are known to influence the magnitude of this response such as the plane of elevation [1]; however, gender is rarely tested as a factor. This is remarkable, as gender is known to influence kinematic and injury outcomes at other joints, such as at the knee [2]. Therefore the purpose of this investigation was to identify how gender interacts with humeral elevation angle and humeral elevation plane to affect healthy scapular kinematics during dynamic humeral elevation.

The shoulder is complex and comprised of many moving parts. Accurately measuring shoulder rhythm is difficult. To classify shoulder rhythm and identify pathological movement, static measures have been the preferred method. However, dynamic measures are also used and can be less burdensome to obtain. The purpose of this paper was to determine how closely dynamic measures represent static measures using the same acromion marker cluster scapular tracking technique. Five shoulder angles were assessed for 24 participants using dynamic and static tracking techniques during humeral elevation in three planes (frontal, scapular, sagittal). ANOVAs were used to identify where significant differences existed for the factors of plane, elevation angle, and tracking technique (static, dynamic raising, dynamic lowering). All factors were significantly different for all shoulder angles (p<0.001), except for elevation plane in scapulothoracic protraction/retraction (p=0.955). Tracking techniques were influential (p<0.001), but the grouped mean differences fell below a clinically relevant 5° benchmark. There was large variation in mean differences of the techniques across individuals. While population averages are similar, individual static and dynamic shoulder assessments may be different. Caution should be taken when dynamic shoulder assessments are performed on individuals, as they may not reflect those obtained in static scapular motion tracking.

Scapular kinematics are important indicators of dyskinesis, often suggesting underlying shoulder pathology, but the influence of sex is unknown. This study's objective was to examine scapular kinematics in healthy males and females. Positions of surface-mounted reflective markers were tracked during arm elevation movements in 0°/30°/40°/60°/90°/120° planes. Scapulothoracic rotations (protraction/retraction, medial/lateral rotation, posterior/anterior tilt) were calculated. ANOVA analysis evaluated main and interaction effects of sex, plane, phase, elevation angle. Males and females had similar protraction/retraction and medial/lateral rotation kinematics; mean sex-related peak angle differences were 2.5°, 1.8° (raise (concentric)), respectively, and 2.9°, 2.7° (lower (eccentric)). Largest sex differences for mean peak angle occurred for posterior/anterior tilt at higher elevation angles (raise, 8.4°; lower, 8.5°). Elevation, plane, phase were main effects for all scapular rotati...

The shoulder is complex and comprised of many moving parts. Accurately measuring shoulder rhythm is difficult. To classify shoulder rhythm and identify pathological movement, static measures have been the preferred method. However, dynamic measures are also used and can be less burdensome to obtain. The purpose of this paper was to determine how closely dynamic measures represent static measures using the same acromion marker cluster scapular tracking technique. Five shoulder angles were assessed for 24 participants using dynamic and static tracking techniques during humeral elevation in three planes (frontal, scapular, sagittal). ANOVAs were used to identify where significant differences existed for the factors of plane, elevation angle, and tracking technique (static, dynamic raising, dynamic lowering). All factors were significantly different for all shoulder angles (p<0.001), except for elevation plane in scapulothoracic protraction/retraction (p=0.955). Tracking techniques w...

Pushing and pulling account for nearly half of all manual material handling tasks. The purpose of this investigation was to develop a 3-D spatial muscle activity map for the right upper extremity during pushing and pulling tasks. Nineteen males performed 140 ramped directional hand exertions (70 push; 70 pull) at locations along three axes aligned with the anatomical planes. Electromyography (EMG) of 14 sites on the right upper extremity was recorded. Two directional 3-way repeated measures ANOVAs assessed the influence of hand position on EMG. Hand position and exertion direction influenced total and individual muscle demand. During pulling exertions, all three hand location parameters influenced total muscle activity (p < 0.001) and similarly in pushing exertions (p < 0.002), though less pronounced than in pulling. Data were used to create equations to predict the muscle activity of untested hand locations for novel work design scenarios.

Exerting manual forces is critical during occupational performance. Therefore, being able to estimate maximum force capacity is particularly useful for determining how these manual exertion demands relate to available capacity. To facilitate this type of prediction requires a complete understanding of how maximum force capacity is governed biomechanically. This research focused on identifying how factors including joint moment strength, balance and shoe-floor friction affected hand force capacity during pulling, pressing downward and pushing medially. To elucidate potential limiting factors, joint moments were calculated and contrasted with reported joint strength capacities, the balancing point within the shoe-floor interface was calculated and expressed relative to the area defined by the shoe-floor interface, and the net applied horizontal forces were compared with the available friction. Each of these variables were calculated as participants exerted forces in a series of condit...