title: A longitudinal study on cardiac effects of deconditioning and physical reconditioning using the anterior cruciate ligament injury as a model.
abstract: BACKGROUND
  Studies of cardiovascular deconditioning are primarily carried out after experimental bed rest. No previous study has followed the cardiovascular effects of decreased and resumed physical activity in athletes after acute physical injury and convalescence. Anterior cruciate ligament (ACL) injury causes a significantly decreased activity level over a long period, making it an ideal model for studying effects of deconditioning and reconditioning. Therefore, the aim of this study was to investigate how cardiac dimensions and maximal exercise capacity change after an ACL-injury.
  
  
  METHODS
  Seventeen athletes (5 women) were included. Cardiac magnetic resonance (CMR) was performed within 5 days of the injury (CMR1), before endurance training was resumed (CMR2) and 6 months after the second scan (CMR3). Maximal exercise testing was performed on the same day as CMR2 and 3.
  
  
  RESULTS
  The deconditioning phase between CMR1 and CMR2 was 59 ± 28 days. Total heart volume (THV) decreased with -3·1 ± 6·7%, P = 0·056. Between CMR2 and 3 (reconditioning), THV increased significantly (2·5 ± 4·6%, P<0·05). Left and right ventricular EDV decreased during deconditioning (-3·0 ± 5·6% and -4·7 ± 6·6%) and increased during reconditioning (1·7 ± 3·9% and 2·6 ± 6·2%) however not statistically significant. Left ventricular mass (LVM) remained unchanged. VO2 peak (mlmin(-1) kg(-1) ) increased significantly during the reconditioning phase (6·1 ± 5·3%, P<0·001).
  
  
  CONCLUSIONS
  Physiological cardiac adaptation to deconditioning and reconditioning caused by severe knee injury with maintained normal daily living during convalescence was smaller than previously shown in bed rest studies. Total heart volume and VO2 peak were significantly affected by reconditioning whilst LVEDV, RVEDV and LVM remained unchanged over the study period.
authors.affiliation: Department of Clinical Physiology, Lund University, Skåne University Hospital, Lund, Sweden.
authors.forename: Katarina
authors.initials: K
authors.lastname: Steding-Ehrenborg
authors.forename: Bo
authors.initials: B
authors.lastname: Hedén
authors.forename: Pär
authors.initials: P
authors.lastname: Herbertsson
authors.forename: Håkan
authors.initials: H
authors.lastname: Arheden
mesh_terms: D000203:Activities of Daily Living; D000222:Adaptation, Physiological; D000328:Adult; D016118:Anterior Cruciate Ligament / Q000503:physiopathology; D000070598:Anterior Cruciate Ligament Injuries; D001944:Breath Tests; D018493:Cardiovascular Deconditioning; D005080:Exercise Test; D005081:Exercise Therapy; D017079:Exercise Tolerance; D005260:Female; D006321:Heart / Q000503:physiopathology*; D006339:Heart Rate; D006801:Humans; D007718:Knee Injuries / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy*; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging; D008297:Male; D010101:Oxygen Consumption; D064797:Physical Conditioning, Human; D020127:Recovery of Function; D012720:Severity of Illness Index; D013318:Stroke Volume; D013997:Time Factors; D016896:Treatment Outcome; D016277:Ventricular Function, Left; D016278:Ventricular Function, Right; D055815:Young Adult
keywords: athletes; left ventricle; physiology; total heart volume