title: Residual Impact of Previous Injury on Musculoskeletal Characteristics in Special Forces Operators.
abstract: BACKGROUND
  Musculoskeletal injuries are a significant burden to United States Army Special Operations Forces. The advanced tactical skill level and physical training required of Army Special Operators highlights the need to optimize musculoskeletal characteristics to reduce the likelihood of suffering a recurrent injury.
  
  
  OBJECTIVE
  To identify the residual impact of previous injury on musculoskeletal characteristics.
  
  
  METHODS
  Cross-sectional study; Level of evidence, 3.
  
  
  METHODS
  Isokinetic strength of the knee, shoulder, and back and flexibility of the shoulder and hamstrings were assessed as part of a comprehensive human performance protocol, and self-reported musculoskeletal injury history was obtained. Subjects were stratified based on previous history of low back, knee, or shoulder injury, and within-group and between-group comparisons were made for musculoskeletal variables.
  
  
  RESULTS
  Knee injury analysis showed no significant strength or flexibility differences. Shoulder injury analysis found internal rotation strength of the healthy subjects (H) was significantly higher compared with injured (I) and uninjured (U) limbs of the injured group (H, 60.8 ± 11.5 percent body weight [%BW]; I, 54.5 ± 10.5 %BW; U, 55.5 ± 11.3 %BW) (P = .014 [H vs I] and P = .05 [H vs U]). The external rotation/internal rotation strength ratio was significantly lower in the healthy subjects compared with injured and uninjured limbs of the injured group (H, 0.653 ± 0.122; I, 0.724 ± 0.121; U, 0.724 ± 0.124) (P = .026 [H vs I] and P = .018 [H vs U]). Posterior shoulder tightness was significantly different between the injured and uninjured limb of the injured group (I, 111.6° ± 9.4°; U, 114.4° ± 9.3°; P = .008). The back injury analysis found no significant strength differences between the healthy and injured groups.
  
  
  CONCLUSIONS
  Few physical differences existed between operators with prior knee or back injury. However, operators with a previous history of shoulder injury demonstrated significantly less shoulder strength than uninjured operators as well as decreased shoulder flexibility on the injured side. All operators, regardless of prior injury, must perform the same tasks; therefore, a targeted injury rehabilitation/human performance training specifically focused on internal rotation strength and tightness of the posterior capsule may help reduce the risk for recurrence of injury. Operators presenting with musculoskeletal asymmetries and/or insufficient strength ratios may be predisposed to musculoskeletal injury.
  
  
  CONCLUSIONS
  Specific fitness programs to compensate for deficiencies in strength and flexibility need to be designed that may reduce the risk of injuries in Special Forces Operators.
authors.affiliation: Department of Sports Medicine and Nutrition, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Parr
authors.affiliation: School of Sport, Health, and Applied Science, St Mary's University, Strawberry Hill, London, UK.
authors.forename: Nicholas C
authors.initials: NC
authors.lastname: Clark
authors.affiliation: College of Health Sciences, University of Kentucky, Lexington, Kentucky, USA.
authors.forename: John P
authors.initials: JP
authors.lastname: Abt
authors.affiliation: Department of Physical Therapy, Methodist University, Fayetteville, North Carolina, USA.
authors.forename: Julie Y
authors.initials: JY
authors.lastname: Kresta
authors.affiliation: Department of Sports Medicine and Nutrition, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
authors.forename: Karen A
authors.initials: KA
authors.lastname: Keenan
authors.affiliation: US Army Special Operations Command, Fort Bragg, North Carolina, USA.
authors.forename: Shawn F
authors.initials: SF
authors.lastname: Kane
authors.affiliation: College of Health Sciences, University of Kentucky, Lexington, Kentucky, USA.
authors.forename: Scott M
authors.initials: SM
authors.lastname: Lephart
keywords: injury prevention; military; muscle injury; performance; residual