A recent research study (1) compared long-term changes in the achilles tendon between gymnasts & non-athletes. They found that gymnasts had developed greater muscle-strength, but no differences in tendon stiffness, suggesting “a training-induced imbalanced adaptation of muscle strength and tendon stiffness”. This confirms something Ido suggested almost 10 years ago (2, 3) - gymnasts lack tendon adaptations due to reliance on external springs.

We’ve been doing some bouncing work that specifically affects tendons & connective tissue. By limiting contribution of contractile/muscular elements, we shift the burden to the tendon, taking the energy provided by gravity to store & release it.

As we’ve been discussing in our classes, tendon is a soft-matter tissue. One property of soft matter, and connective tissues especially, is a shift of the stress-strain curve during cyclic loading (strain that loads/unloads repetitively). This shift means that there will be strains at a given load that would not otherwise produce an effect, because there is this repetitive component. Cyclic loading, such as in bouncing, produces the kind of strain that triggers adaptations towards elasticity - changes in proteoglycan content, fibril organization/orientation, and ultimately critical connective tissue properties).

This is a synergetic outcome - you cannot simply add up the effect of disparate jumps. 1+1 = 2 if you’re loading the tissue normally; but 1+1 = 17 when it’s done with bouncing, and a second-order effect arises - tendon adaptation.

1 - The study: Development of Muscle-Tendon Adaptation in Preadolescent Gymnasts and Untrained Peers: A 12-Month Longitudinal Study. https://pubmed.ncbi.nlm.nih.gov/34649260/

2 - RawBrahs interview, the relevant excerpt can be found in “Ido Portal on Paleo Diet, CrossFit, Gymnastics, Motivation, Movement & More” at 4:58 (https://youtu.be/WPnXjFNSf1o?t=238)

3 - Facebook post - November 22, 2018. https://www.facebook.com/portal.ido/photos/a.630345403674110/2342011115840855/