Individualized Muscle-Tendon Assessment and Training
Adamantios Arampatzis, Falk Mersmann and Sebastian Bohm
Front Physiol. 2020 Jun 26;11:723. doi: 10.3389/fphys.2020.00723. eCollection 2020.
We are back for another research roundup reviewing: Individualized Muscle-Tendon Assessment and Training (https://pubmed.ncbi.nlm.nih.gov/32670094/)
This review is piggy backing off of January's roundup about tendon stiffness and rate of force development. Here's the link if you'd like to read it again: https://mailchi.mp/julietamanda.com/january-research-roundup
I want to preface this review by saying I don't believe any of these methods are available to climbing yet because of the poor accessibility to the tools needed. BUT the concepts are interesting and someone with an ultrasound machine may want to look at these things :)
Purpose
This article is perspective which means it's proposing potential protocols.
Currently most strength training interventions and assessment protocols focus on muscle strength. However, there is more at play because the muscle is part of the muscle-tendon unit (MTU).
As discussed in the January Research Roundup, if there is an imbalance in the development of muscle strength or tendon stiffness, the MTU is less effective and also more susceptible to injury.
Also previously discussed, the optimal way to train muscle strength is different than the best way to increase tendon stiffness.
This article proposes a protocol for identifying which part of the MTU needs to be strengthened (the muscle or the tendon) so that training loads can be more appropriately assigned to individual athletes.
Background
The tendon is a collagenous structure that has elastic properties and deforms to different degrees based on how it is stressed. The level of deformation is known as tendon strain.
Deformation is a normal characteristic of the tendon. However if the tendon is repeatedly subjected to strain levels that are too high or too low, the structure and function of the tendon may be compromised.
This article cites another study (Wang et al. 2013) that showed these upper and lower end values: a strain of 9.0% or higher can cause structural deterioration of the tendon while a strain of 3.0% or lower can also degenerate the tendon (use it or lose it!).
In previous studies by the group, Arampatzis et al., 2020 states, "cyclic loading of the
tendon with strain values between 4.5 and 6.5% and a duration of 3 s per repetition... was the most effective mechanical stimulus for the improvement of human tendon mechanical properties in vivo (Arampatzis et al., 2007a, 2010; Bohm et al., 2014)."
However the strain values of 4.5-6.5% may be achieved at different loads in different individuals.
(Image from Arampatzis et al., 2020)
Currently, protocols use an intensity of 90% of a voluntary maximum isometric contraction (MVC) as a general rule of thumb to reach these strain values, though this necessary intensity may actually vary from individual to individual.
Proposed Methodology for Individualized Muscle-Tendon Training
The first proposed step from this article is to assess the tendon strain during an MVC. If the tendon strain is high (9.0% or above) then this indicates that the muscle is much stronger than the tendon is stiff and that tendon stiffness should be the focus of the individual's training.
If the tendon strain is low (4.5% or below) then this indicates that the muscle is weaker than the tendon is stiff and focusing on increasing muscle strength would be good for the individual.
Summary of proposed practical implementation:
1. Find a relevant position for an isometric contraction to measure the desired tendon. In this article's example, they propose assessing the patellar tendon with a seated position and the knee at 90 degrees.
2. The individual performs an isometric contraction of 5 seconds, building in intensity throughout the duration of the contraction (after proper warm-up)
3. A linear ultrasound transducer measures the force or moment data
4. The displacement of the tendon insertion is manually measured with video analysis software and is the elongation value
5. Using the force/moment data and the elongation value, the strain can be calculated
Arampatzis A, Mersmann F, Bohm S. Individualized Muscle-Tendon Assessment and Training. Front Physiol. 2020 Jun 26;11:723. doi: 10.3389/fphys.2020.00723. PMID: 32670094; PMCID: PMC7332733.
Wang, T., Lin, Z., Day, R. E., Gardiner, B., Landao-Bassonga, E., Rubenson, J., et al. (2013). Programmable mechanical stimulation influences tendon homeostasis in a bioreactor system. Biotechnol. Bioeng. 110, 1495–1507. doi: 10.1002/bit. 24809
My Two Cents
Because this is a perspective article, the proposed methodology still needs to be validated. However, I do think it would be interested to see the strain values in common tendinopathies in climbers and if there are any obvious trends or patterns.
For example, flexor tendon injuries, epicondylitis, lower extremity tendinopathies, etc.
As always, I'm interested to hear your thoughts so feel free to reply to this email and have a great weekend!
