Abstract
Introduction: Shoulder dysfunction is one of the leading musculoskeletal reasons patients seek treatment from physical therapists. Research on the best practices of manual therapy (MT) has been limited over the years by a lack of understanding of the forces utilized and the actual effect on the humeral head and capsule. This study serves as a bridge between past literature in confirming or refuting suggested normative values of translational forces needed for reaching joint capsule end range. Methods: Subjects for this descriptive quasi-experimental study were recruited using convenience sampling. Quantitative measurements of the forces applied to the humeral head during an inferior glide manual therapy technique were measured using a flexible force sensor device. The distance of humeral head displacement in healthy, living human subjects was studied simultaneously to the forces applied during an inferior glide shoulder joint manipulation. Results: Sixty-nine subjects participated in this study consisting of one data collection session. Common inferential statistics for force and distance data yielded no statistically significant results suggesting a larger subject pool may be necessary in future studies. A 1-tailed Pearson bivariate correlation found a fair correlation between the subject’s age and the force needed to move the joint capsule to end range. Discussion: The average force required to reach end range within the joint capsule was 14.27 N, with a range from 5.25 N to 35.92 N, compared to 80 N found in previous studies. Improved technology of the flexible force sensor device enabled more accurate measures between the hand applying the joint manipulation and the contours of manipulated tissue. An increase in joint capsule stiffness occurs with age resulting in overall increased force to reach end range within the joint capsule. Conclusion: Average force required to reach joint capsule end range was 14.27 N. No definitive parameters can be identified based on the results of this study, while data suggests subject characteristics warrant further investigation and must be included as well as controlled for as variables in future research.