Short Term Tendon Adaptation Reddit Post

Vertical Junkie posted a reply to a submaximal short duration hang protocol on Reddit which quickly became one of the top rated climbharder posts.  Below is quick summary of the post!

Paul Norris (Physio, Vertical Junkie)

Post in reply to Emils Submaximal Short Duration Twice a Day Protocol

Starting out – I really enjoy Emils content and appreciate him putting ideas out into the world in an entertaining format! On that note – i tend to present information in a much less entertaining format 😉 So sorry about that. It’s hard to make physiology sexy!!

I wanted to outline some tendon physiology to help clear up the confusion around Emil’s video. The comments are already blowing up too far to leave any of this in there or on the video itself, so apologies for the separate post.

The finger flexor tendons do NOT generate force – they are simply a chain which applies force to the bone. Yes tenocytes (fibroblasts in tendons which create collagen) are refractory with an approximate 6 hour “lockout” period for stimulus. Yes doing short duration 10 min load cycles every 6 hours will optimise collagen synthesis. This over a long period can improve tendon resilience to injury – but you have to also manage tendon stiffness during this process.

Generally for rehab purposes as you apply intermittent tendon loading strategies for collagen synthesis you do them as long duration loads to prevent hyperstiffness of the connective tissue.

In regards to the huge strength increase from this program. It is likely due to one of two mechanisms.

  1. The most likely. Increased tendon stiffness from a repetitive Short duration loading program. When you do repetitive short duration loads you stimulate lysyloxidase to form crosslinks in your tendon. This increases tendon stiffness which improves the force application properties to the bone. It also INCREASES injury risk as the offset of an increased performance peak from the tendon.This is what worries me – is that everyone will be doing this program – getting gains – continue to stiffen the connective tissue, and then end up with catastrophic connective tissue failure. This is similar to doing power blocks before a performance phase to stiffen connective tissue, short duration loads, but doing it ONLY as a tendon stimulus (and removing the muscle and nervous system elements).

  2. Current ligament issue (not tendon). If he was suffering from a pulley issue on initial testing – loading the pulley submaximal in a non compressive state might have reduced inhibition of his finger flexor tendons and even not doing his old overloading training strategies may have allowed for remodelling and improvement of this pulley.

Regarding finger health – short duration loads aren’t great at remodelling tendon due to stress shielding mechanisms in the tendon. This would be a great finger health program if the load durations were longer but still submaximal.

This program would also likely not be enough stimulus to get these kinds of gains anywhere else. Either in the muscle unit itself or recruitment of the nervous system.

Either way – I think the causality and understanding of the physiology behind what is happening here is presented very poorly. I complement them on acknowledging their experiment being a single person case study but I would love for them to have a more complete understanding.

Sorry for the long read! Feel free to ask any questions and I can try and answer them with research papers or some really great conference talks from Keith barr, jill cook and other world leading tendon health experts.


For those interested – Keith Bar Covers some of these concepts in his sports congress summit from 2018.  (

From this we received over 100 comments and questions to clarify tendon mechanics in response to various loads, delve into the latest tendon research and talked over how to structure this as part of a training program.

To read all this – head over to the REDDIT post itself, reach out on Instagram or get in touch with Paul at or on the Vertical Junkie Discord for Members.

Clearing up Confusion on Emils New Twice a Day Hangboard Routine from climbharder

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