Immediate and long-term effects of mechanical loading on Achilles tendon volume: A systematic review and meta-analysis

Eman Merza1, Dr Stephen  Pearson2, Professor  Glen  Lichtwark3, Meg Ollason1, Associate Professor Peter  Malliaras1

1Department of Physiotherapy, Faculty of Medicine, Nursing and Health Science, Monash University, Melbourne, Australia, 2Centre for Health, Sport and Rehabilitation Sciences Research, University of Salford, Greater Manchester, United Kingdom , 3Centre for Sensorimotor Performance, School of Human Movement and Nutrition Sciences, The University of Queensland, St. Lucia, Brisbane, Australia, 4Department of Physiology, Biomedicine Discovery Institute, Monash University, Melbourne, Australia

Introduction: Mechanical load induces transient changes in Achilles tendon dimensions related to fluid flow. Whether fluid flow involves redistribution within or flows out of the tendon is not known and could be determined by investigating volume changes. This study aimed to synthesize data on immediate and long-term effects of mechanical loading on tendon volume among people with healthy AT and midportion Achilles tendinopathy (MAT).

Methods: The review was reported in accordance with PRISMA guidelines. Twelve studies were included in the meta-analysis. Standardized mean differences (SMDs) were calculated for intervention-induced changes from baseline for all outcomes.

Results: For healthy AT, there were negligible to small changes in volume following cross-country running (-0.33 [95% CI = -1.11 to 0.45] (P = 0.41)) and isometric exercise (0.01[95% CI = -0.54 to 0.55] (P = 0.98)) and a large increase at the short-term with 12-week isometric protocol (0.88 [95% CI = -0.10 to1.86] (P = 0.08)). For MAT, there was an immediate large reduction in volume with isometric exercise (-1.24 [95% CI = -1.93 to -0.55] (P = 0.0004)), small increase with eccentric exercise (0.41 [95% CI = -0.18 to 1.01] (P = 0.18)) and small reduction at the short-term with long-term interventions (-0.46 [95% CI = -0.87 to -0.05] (P = 0.03)).

Discussion: The healthy AT seems to remain isovolumetric in response to acute interventions, regardless of reductions in CSA as a result of fluid redistribution. In contrast, pathological tendons may display a significant reduction in volume with acute and long-term interventions.


Eman Merza is a full-time PhD student at the Monash University department of physiotherapy. She obtained her bachelor’s degree in physiotherapy from Kuwait University in 2008 and her master’s degree from the University of Nottingham (UK) in 2016. Eman research focus is Achilles tendinopathy. She is investigating the biomechanical adaptation of the Achilles tendon in response to load.

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