title: Experimental knee joint pain during strength training and muscle strength gain in healthy subjects: a randomized controlled trial.
abstract: OBJECTIVE
  Knee joint pain and reduced quadriceps strength are cardinal symptoms in many knee pathologies. In people with painful knee pathologies, quadriceps exercise reduces pain, improves physical function, and increases muscle strength. A general assumption is that pain compromises muscle function and thus may prevent effective rehabilitation. This study evaluated the effects of experimental knee joint pain during quadriceps strength training on muscle strength gain in healthy individuals.
  
  
  METHODS
  Twenty-seven healthy untrained volunteers participated in a randomized controlled trial of quadriceps strengthening (3 times per week for 8 weeks). Participants were randomized to perform resistance training either during pain induced by injections of painful hypertonic saline (pain group, n = 13) or during a nonpainful control condition with injection of isotonic saline (control group, n = 14) into the infrapatellar fat pad. The primary outcome measure was change in maximal isokinetic muscle strength in knee extension/flexion (60, 120, and 180 degrees/second).
  
  
  RESULTS
  The group who exercised with pain had a significantly larger improvement in isokinetic muscle strength at all angular velocities of knee extension compared to the control group. In knee flexion there were improvements in isokinetic muscle strength in both groups with no between-group differences.
  
  
  CONCLUSIONS
  Experimental knee joint pain improved the training-induced gain in muscle strength following 8 weeks of quadriceps training. It remains to be studied whether knee joint pain has a positive effect on strength gain in patients with knee pathology.
authors: The Parker Institute, Copenhagen University Hospital Frederiksberg, Frederiksberg, Denmark.
authors: T J
authors: TJ
authors: Sørensen
authors: H
authors: H
authors: Langberg
authors: P W
authors: PW
authors: Hodges
authors: H
authors: H
authors: Bliddal
authors: M
authors: M
authors: Henriksen
mesh_terms: D000328:Adult; D018771:Arthralgia / Q000139:chemically induced / Q000503:physiopathology*; D001696:Biomechanical Phenomena; D003718:Denmark; D005260:Female; D006801:Humans; D007270:Injections, Intra-Articular; D007719:Knee Joint / Q000503:physiopathology*; D008297:Male; D053580:Muscle Strength; D010147:Pain Measurement; D052097:Quadriceps Muscle / Q000503:physiopathology*; D055070:Resistance Training; D012462:Saline Solution, Hypertonic / Q000008:administration & dosage; D013997:Time Factors; D019415:Torque; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D012462:Saline Solution, Hypertonic