Merza, E 
ORCID: https://orcid.org/0000-0003-0363-6736, Pearson, SJ, Lichtwark, G and Malliaras, P
2022,
'The acute effects of higher versus lower load duration and intensity on morphological and mechanical properties of the healthy Achilles tendon: a randomized crossover trial'
, Journal of Experimental Biology, 225 (10)
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Abstract
ABSTRACT The Achilles tendon (AT) exhibits volume changes related to fluid flow under acute load which may be linked to changes in stiffness. Fluid flow provides a mechanical signal for cellular activity and may be one mechanism that facilitates tendon adaptation. This study aimed to investigate whether isometric intervention involving a high level of load duration and intensity could maximize the immediate reduction in AT volume and stiffness compared with interventions involving a lower level of load duration and intensity. Sixteen healthy participants (12 males, 4 females; age 24.4±9.4 years, body mass 70.9±16.1 kg, height 1.7±0.1 m) performed three isometric interventions of varying levels of load duration (2 s and 8 s) and intensity (35% and 75% maximal voluntary isometric contraction) over a 3 week period. Freehand 3D ultrasound was used to measure free AT volume (at rest) and length (at 35%, 55% and 75% of maximum plantarflexion force) pre- and post-interventions. The slope of the force–elongation curve over these force levels represented individual stiffness (N mm−1). Large reductions in free AT volume and stiffness resulted in response to long-duration high-intensity loading whilst less reduction was produced with a lower load intensity. In contrast, no change in free AT volume and a small increase in AT stiffness occurred with lower load duration. These findings suggest that the applied load on the AT must be heavy and sustained for a long duration to maximize immediate volume reduction, which might be an acute response that enables optimal long-term tendon adaptation via mechanotransduction pathways.
| Item Type: | Article |
|---|---|
| Schools: | Schools > School of Health and Society |
| Journal or Publication Title: | Journal of Experimental Biology |
| Publisher: | The Company of Biologists |
| ISSN: | 1477-9145 |
| Funders: | Monash University |
| SWORD Depositor: | Publications Router |
| Depositing User: | Publications Router |
| Date Deposited: | 15 Jun 2022 11:29 |
| Last Modified: | 15 Jun 2022 11:29 |
| URI: | http://usir.salford.ac.uk/id/eprint/63997 |
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