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Lowry V.1, Paquette P.1,2, Cyr V.1, Gagnon D.H.1,2, Godin V.1, Labelle D.1, Laroche T.1, Manuguerra-Gagné A.1, Pilote-Lapointe J.1, Desmeules F.1,3
1University of Montreal, School of Rehabilitation, Montreal, Canada, 2Center for Interdisciplinary Research in Rehabilitation of Greater Montreal, Montreal Rehabilitation Institute, Montreal, Canada, 3Maisonneuve-Rosemont Hospital Research Center, University of Montréal Affiliated Research Center, Orthopaedic Unit, Montreal, Canada
Background: Eccentric exercises are recommended for the treatment of tendinopathies. However, their use increases muscle and tendon loading to a greater extent than isometric or concentric exercises. Consequently, eccentric exercises may increase risk of muscular or tendon damage. The optimal training volume yielding to the best possible physiological impacts of eccentric exercises remains difficult to pinpoint by physiotherapists in clinical practice. Typically, they rely on a trial-and-error process informed by previous clinical experience and indirect outcome measures to guide clinical progression and recommendations for return to normal activities of patient under their care. Musculoskeletal (MSK) ultrasound imaging is a non-invasive technique that may allow physiotherapists to quantify in vivo soft tissues changes resulting from eccentric exercises and eventually guide physiotherapists in prescribing the adequate training volume.
Purpose: To quantify MSK ultrasonographic changes of the dominant rectus femoris muscle and patellar tendon following an eccentric fatigue protocol completed by healthy individuals.
Methods: Sixteen healthy adults performed 5 sets of 15 maximal eccentric knee flexion between 80° to 10° of knee flexion at a constant speed(60°/s). Three MSK ultrasonographic images of the rectus femoris and the patellar tendon were recorded by a single evaluator in the longitudinal and transverse planes before (T0), immediately after (T1) and 48 hours after (T2) completing the protocol. An ultrasound imaging device (Philips-HD11XE) equipped with a 5-cm wide linear probe (5-12MHz) was used. Outcome measures, computed using a Matlab image analysis software recently developed by our team, included muscle thickness, width and cross-sectional area (CSA) as well as echogenicity measures (i.e., mean grayscale value within the CSA) for the rectus femoris in the transverse plane. For the longitudinal (1-cm wide region of interest) and transverse patellar tendon planes, similar measures were computed. One-way repeated measures ANOVAs were computed.
Results: For the rectus femoris, both the CSA (+0.44 cm2; +8.3%; p 0.05) and the height (+0.21cm2; +11.5%; p 0.05) increased significantly between T0 and T1 whereas the echogenicity (-3.27/256; -6.7%; p 0.05) decreased between T0 and T1. However, the echogenicity change is below the minimal detectable change. There was no statistically significant difference for the rectus femoris for any outcome between T0 and T2. For the patellar tendon, there was no significant difference for thickness and CSA pre-post exercise protocol. The echogenicity decreased significantly between T0 and T2 in the transverse plane only (-6.37/256; -7.9%; p 0.05) and T1 and T2 in the transverse (-5.88/255; -7.4%; p 0.05) and longitudinal planes (-6.08/255; -8.6%; p 0.05).
Conclusion(s): Changes of the rectus femoris immediately after the eccentric fatigue protocol may be attributable to the increased vascularization caused by muscular contractions. Changes of the patellar tendon 48 hours after the eccentric program may be caused by the late-onset inflammatory reaction leading to tissue repair and adaptation.
Implications: MSK ultrasonography is capable to detect changes in the anatomy and physiology of muscle and tendon of the extensor mechanism following eccentric exercise. More research is needed to understand the physiological changes observed but ultrasonography could ultimately be used to monitor muscle and tendon damage or repair processes over time.
Funding acknowledgements: This study was funded by Dany Gagnon´s Junior 1 research grant of the Fonds de recherche en santé du Québec.
Topic: Musculoskeletal: lower limb
Ethics approval: This study was approved by the ethic committe of the Centre de recherche interdisciplinaire en réadaptation de Montréal.
All authors, affiliations and abstracts have been published as submitted.
