title: Low- Versus High-Intensity Plyometric Exercise During Rehabilitation After Anterior Cruciate Ligament Reconstruction.
abstract: BACKGROUND
  Plyometric exercise is used during rehabilitation after anterior cruciate ligament (ACL) reconstruction to facilitate the return to sports participation. However, clinical outcomes have not been examined, and high loads on the lower extremity could be detrimental to knee articular cartilage.
  
  
  OBJECTIVE
  To compare the immediate effect of low- and high-intensity plyometric exercise during rehabilitation after ACL reconstruction on knee function, articular cartilage metabolism, and other clinically relevant measures.
  
  
  METHODS
  Randomized controlled trial; Level of evidence, 2.
  
  
  METHODS
  Twenty-four patients who underwent unilateral ACL reconstruction (mean, 14.3 weeks after surgery; range, 12.1-17.7 weeks) were assigned to 8 weeks (16 visits) of low- or high-intensity plyometric exercise consisting of running, jumping, and agility activities. Groups were distinguished by the expected magnitude of vertical ground-reaction forces. Testing was conducted before and after the intervention. Primary outcomes were self-reported knee function (International Knee Documentation Committee [IKDC] subjective knee form) and a biomarker of articular cartilage degradation (urine concentrations of crosslinked C-telopeptide fragments of type II collagen [uCTX-II]). Secondary outcomes included additional biomarkers of articular cartilage metabolism (urinary concentrations of the neoepitope of type II collagen cleavage at the C-terminal three-quarter-length fragment [uC2C], serum concentrations of the C-terminal propeptide of newly formed type II collagen [sCPII]) and inflammation (tumor necrosis factor-α), functional performance (maximal vertical jump and single-legged hop), knee impairments (anterior knee laxity, average knee pain intensity, normalized quadriceps strength, quadriceps symmetry index), and psychosocial status (kinesiophobia, knee activity self-efficacy, pain catastrophizing). The change in each measure was compared between groups. Values before and after the intervention were compared with the groups combined.
  
  
  RESULTS
  The groups did not significantly differ in the change of any primary or secondary outcome measure. Of interest, sCPII concentrations tended to change in opposite directions (mean ± SD: low-intensity group, 28.7 ± 185.5 ng/mL; high-intensity group, -200.6 ± 255.0 ng/mL; P = .097; Cohen d = 1.03). Across groups, significant changes after the intervention were increased the IKDC score, vertical jump height, normalized quadriceps strength, quadriceps symmetry index, and knee activity self-efficacy and decreased average knee pain intensity.
  
  
  CONCLUSIONS
  No significant differences were detected between the low- and high-intensity plyometric exercise groups. Across both groups, plyometric exercise induced positive changes in knee function, knee impairments, and psychosocial status that would support the return to sports participation after ACL reconstruction. The effect of plyometric exercise intensity on articular cartilage requires further evaluation.
  
  
  BACKGROUND
  Clinicaltrials.gov NCT01851655.
authors.affiliation: Department of Physical Therapy, University of Florida, Gainesville, Florida, USA TRIA Orthopaedic Center, Bloomington, Minnesota, USA terese.chmielewski@tria.com.
authors.forename: Terese L
authors.initials: TL
authors.lastname: Chmielewski
authors.affiliation: Department of Physical Therapy, University of Florida, Gainesville, Florida, USA.
authors.forename: Steven Z
authors.initials: SZ
authors.lastname: George
authors.affiliation: UF Health Rehab Center at the Orthopaedics and Sports Medicine Institute, Gainesville, Florida, USA.
authors.forename: Susan M
authors.initials: SM
authors.lastname: Tillman
authors.affiliation: Department of Orthopaedics & Rehabilitation, University of Florida, Gainesville, Florida, USA.
authors.forename: Michael W
authors.initials: MW
authors.lastname: Moser
authors.affiliation: UF Health Rehab Center at the Orthopaedics and Sports Medicine Institute, Gainesville, Florida, USA.
authors.forename: Trevor A
authors.initials: TA
authors.lastname: Lentz
authors.affiliation: Department of Orthopaedics & Rehabilitation, University of Florida, Gainesville, Florida, USA.
authors.forename: Peter A
authors.initials: PA
authors.lastname: Indelicato
authors.affiliation: Veterinary Population Medicine, University of Minnesota, Minneapolis, Minnesota, USA.
authors.forename: Troy N
authors.initials: TN
authors.lastname: Trumble
authors.affiliation: Department of Health Outcomes and Policy, University of Florida, Gainesville, Florida, USA.
authors.forename: Jonathan J
authors.initials: JJ
authors.lastname: Shuster
authors.affiliation: School of Public Health and Preventive Medicine, Monash University, Melbourne, Australia.
authors.forename: Flavia M
authors.initials: FM
authors.lastname: Cicuttini
authors.affiliation: Institute on Aging, University of Florida, Gainesville, Florida, USA.
authors.forename: Christiaan
authors.initials: C
authors.lastname: Leeuwenburgh
mesh_terms: D016118:Anterior Cruciate Ligament / Q000601:surgery; D000070598:Anterior Cruciate Ligament Injuries; D059549:Anterior Cruciate Ligament Reconstruction / Q000534:rehabilitation*; D015415:Biomarkers / Q000378:metabolism; D002358:Cartilage, Articular / Q000502:physiology; D024043:Collagen Type II / Q000378:metabolism; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000209:etiology / Q000503:physiopathology; D007718:Knee Injuries / Q000534:rehabilitation / Q000601:surgery; D007719:Knee Joint / Q000502:physiology; D008297:Male; D059385:Plyometric Exercise / Q000379:methods*; D052097:Quadriceps Muscle / Q000502:physiology; D000068958:Return to Sport / Q000502:physiology; D012420:Running / Q000502:physiology; D057566:Self Report; D055815:Young Adult
chemical_list: D015415:Biomarkers; D024043:Collagen Type II
keywords: ACL; articular cartilage; knee; loading; outcomes; psychosocial