title: Large strengthening effect of a hip-flexor training programme: a randomized controlled trial.
abstract: OBJECTIVE
  To investigate the effect on hip-flexion strength of a 6-week hip-flexor training programme using elastic bands as resistance. We hypothesized that the training group, compared to a control group, would increase their hip-flexion strength more.
  
  
  METHODS
  Thirty-three healthy subjects (45 % females), 24(5) years of age, were included in a randomized controlled trial and allocated to heavy strength training of the hip-flexor muscles or to control (no strength training). Strength training of the hip-flexors (dominant leg) was performed three times 10 min per week for 6 weeks. The strength training group progressed from 15 repetition maximum (RM) (week 1) to 8 RM (week 6). Isometric hip-flexion strength (primary outcome) was measured by a blinded assessor using a reliable test procedure.
  
  
  RESULTS
  In the strength training group, the isometric hip-flexion strength of the trained leg increased by 17 %, (p < 0.001). The between-group difference in hip-flexion strength change in the trained leg (dominant leg, training group) versus the non-trained leg (dominant leg, control group) was significantly different from baseline to follow-up, corresponding to a mean change of 0.34 (95 % CI 0.17-0.52) Nm/kg, in favour of the strength training group (p < 0.001).
  
  
  CONCLUSIONS
  Simple hip-flexor strength training using elastic bands as external loading, for only 6 weeks, substantially improves hip-flexor muscle strength. This simple exercise programme seems promising for future prevention and treatment of acute and longstanding hip-flexor injuries, such as acute rectus femoris injuries and longstanding iliopsoas-related pain and impingement.
  
  
  METHODS
  I.
authors: Sports Orthopedic Research Center Copenhagen (SORC-C), Arthroscopic Centre Amager, Copenhagen University Hospital, Hvidovre, Italiensvej 1, 2300, Copenhagen S, Denmark. kristianthorborg@hotmail.com.|Physical Medicine and Rehabilitation Research - Copenhagen (PMR-C), and Departments of Orthopaedic Surgery and Physical Therapy, Copenhagen University Hospital, Copenhagen, Denmark. kristianthorborg@hotmail.com.
authors: Kristian
authors: K
authors: Thorborg
authors: Physical Medicine and Rehabilitation Research - Copenhagen (PMR-C), and Departments of Orthopaedic Surgery and Physical Therapy, Copenhagen University Hospital, Copenhagen, Denmark.|Clinical Research Centre, Copenhagen University Hospital, Hvidovre, Copenhagen, Denmark.
authors: Thomas
authors: T
authors: Bandholm
authors: Gait Analysis Laboratory, Copenhagen University Hospital, Copenhagen, Denmark.
authors: Mette
authors: M
authors: Zebis
authors: National Research Centre for the Working Environment, Copenhagen, Denmark.
authors: Lars Louis
authors: LL
authors: Andersen
authors: Sports Orthopedic Research Center Copenhagen (SORC-C), Arthroscopic Centre Amager, Copenhagen University Hospital, Hvidovre, Italiensvej 1, 2300, Copenhagen S, Denmark.
authors: Jesper
authors: J
authors: Jensen
authors: Sports Orthopedic Research Center Copenhagen (SORC-C), Arthroscopic Centre Amager, Copenhagen University Hospital, Hvidovre, Italiensvej 1, 2300, Copenhagen S, Denmark.
authors: Per
authors: P
authors: Hölmich
mesh_terms: D000328:Adult; D015444:Exercise; D005260:Female; D006615:Hip; D006801:Humans; D008297:Male; D053580:Muscle Strength; D018482:Muscle, Skeletal; D052097:Quadriceps Muscle; D016059:Range of Motion, Articular; D055070:Resistance Training / Q000379:methods*; D013848:Thigh; D055815:Young Adult
keywords: Elastic bands; Iliopsoas; Randomized controlled trial; Rectus femoris; Strengthening