Thomas Research


  • Associate Professor
  • Chair, Department of Exercise Science, JCRS

4201 Henry Avenue
225 Ronson Health & Applied Science Center
Philadelphia, PA 19144

Contact Number(s):

The Adaptation to Repetitive Motion & Stress (ARMS) Lab is directed by Stephen Thomas, PhD, ATC. The goals of the lab are to define the underlying mechanisms responsible for biomechanical, neuromuscular, and tissue adaptations to repetitive stress.  Identifying these underlying mechanisms will allow the development of better training and recovery programs to minimize the risk of overuse musculoskeletal injuries.  

Current Projects

Chronic Shoulder & Elbow Adaptations in Professional Pitchers: Relationship to Injury & Kinetic Chain

The primary purpose of this research is to determine whether there is a relationship between chronic shoulder and elbow adaptations and upper extremity injuries in professional pitchers. Due to the high forces and repetition of throwing, baseball pitchers frequently suffer upper extremity injuries. These high forces also cause the shoulder muscles and surrounding tissue to adapt. Throwing injuries of the shoulder have been extensively researched but throwing injuries have not yet been related to shoulder ultrasound measures, which can quantify the severity of long-term adaptation. Understanding the relationship between chronic shoulder adaptations and injury can help improve injury prevention programs and decrease the number of upper extremity injuries to throwing athletes.

Does Isolated Elbow Arthroscopy for Posteromedial Impingement Lead to Future Ulnar Collateral Ligament Injury?

Despite successful return to sport (RTS) outcomes after posteromedial osteophyte resection, one possible consequence of removing this osteophyte is increased stress on the ulnar collateral ligament (UCL), leading to a UCL injury. It is currently unknown how often overhead athletes who have an isolated posteromedial osteophyte resection progress to require UCL reconstruction (UCLR).  The purpose was to report outcomes following arthroscopic resection of posteromedial osteophyte in overhead athletes and determine if overhead athletes who underwent arthroscopic posteromedial osteophyte resection for posteromedial impingement went on to require UCL surgery. The authors hypothesized that there would be a high rate of RTS following osteophyte resection and that players who underwent arthroscopic posteromedial osteophyte resection would have a >10% risk of requiring a subsequent UCLR or UCL repair.

Effects of Fatigue on Muscle Synergies in the Shoulders of Baseball Players

Throwing a baseball during a baseball competition involves high velocity, a high level of accuracy, and a high number of repetitions with little rest in between. Based on this speed, accuracy and repetition, neuromuscular adaptations have the potential to occur in response to the onset of fatigue. These changes can be identified through the extraction of muscle synergies, but neuromuscular adaptations in response to fatigue have not yet been explored in the baseball population. Therefore, the purpose of this study is to explore the effects of an isolated external rotation fatigue protocol on muscle synergies in the shoulders of baseball players.