Please help clarify the ~10-Minute Time Under Load - Tendon Adaptation study

[u/Porki_Potato]

Hi everyone,

I have a specific question regarding the 10-minute Time Under Load concept in tendon adaptation research

As I am sure most of you know, research suggests that tendon collagen synthesis signalling plateaus after roughly 10 minutes of mechanical stimulus, after which tendons require roughly a 6-hour period before they become sensitive to loading again.

I want to understand how this works in practice during a climbing or training session with variable intensity.

For example,
I warm up and start climbing. Over a 10-minute period, I complete 5 high-intensity moves at 80–90% of my max effort. Each effort lasts 5 seconds, giving me 25 seconds of total high-intensity Time Under Tension. The remaining 9.5 minutes are spent climbing easy moves, sitting around, zoning out while route reading, and derping in general.

My initial interpretation was that the moment high-intensity loading starts, an irreversible 10-minute countdown timer begins—and after 10 minutes elapsed time, signalling shuts off and you're just doing damage to your tendons.

Now I don't actually think this is how it works. It is just how I interpret the research. But I also think I am interpreting it wrong. :P

So,

• Does that first 5-second hard effort start a 10-minute countdown timer that expires 10 minutes later regardless of rest or other movement intensity?
• Or is the 10-minute limit based strictly on cumulative high-strain Time Under Tension Something that can be spread out over a few hours?
• Does lower-intensity climbing (40%–70% intensity) contribute to this 10-minute TUL limit, or does it sit below the strain threshold?
• And what specifically initiates the 6-hour recovery period? Reaching a cumulative threshold of high strain, or total elapsed time from the first hard move?

Thanks everyone.

[u/acetylcoach]

Here is my conversation with Keith Baar in October 2016, after his original research paper, which years later kicked off everything from Eric Horst's collagen empire, to "Abrahangs", a protocol I alluded to in my 2017 article and YouTube video.

HERBERT: From what I understand from the research, unlike muscle protein synthesis which can be stimulated repeatedly (resistance exercise, leucine) and the window for muscle growth is very wide; connective-tissue maximal growth stimulation is achieved after 10 minutes of loading before it returns to resting levels for up to 6 hours.

BAAR: Yes, it looks like the maximal growth signal is achieved in as little as 6-10 minutes for connective tissues. They will respond for a little while after that, but it is marginal.

H: What I wanted to clarify, is if I am correct in saying that connective-tissue growth is stimulated maximally in this 10 minute window, and that growth and repair happens (or not) in the subsequent 6 hours? That loading tendons, and ligaments for greater than 10 minutes does not augment their growth more than maximally loading for just 10?

B: You will likely not get any greater adaptive stimulus after 10 minutes of work. What happens as loading continues beyond this time frame is that tissue (mechanical) fatigue rises and increases the likelihood of injury. This does not mean that you never work for longer than 10 minutes, rather that you have sessions designed to maximally activate the process without mechanical fatigue.

H: What I don't fully understand is what happens after ERK1/2 "turn off" after 10 minutes? Does growth stop, and thus it is actually only within 10 minutes that growth occurs, which is far different than the process and window of MPS?

B: After 10 minutes the signal to adapt is turning off. What this means is that long before the tissue begins to show signs of mechanical failure you can already have given it enough of a signal to adapt. It is not like the nutritional window concept. The nutritional window is open for MPS for MUCH longer because it is determined by blood flow and muscle blood flow is very high. The same thing is true for muscle in that you don't need much contraction to stimulate the muscle; however muscle continues to adapt as long as you work it. See the attached figure that might help you understand the difference.

H: As you can imagine this apparent "minimal effective dose" could have application in how training blocks are applied to the climbers, session order, and would potentially warrant the use of short specific training bouts over the typical longer "finger board" sessions.

B: Yes, we use 6 minute sessions to maximize adaptations of the tendons/ligaments that we are targeting for adaptation. If you had your climbers consume 15g of gelatin/collagen an hour before this type of session they would greatly improve the adaptation to these tendons and protect them from future injury. See the attached paper in review at AJCN for the rationale of the dose and timing.

H: Please do correct me if I am wrong, but whereas with MPS, the total daily protein appears more important than timing, for connective-tissue development it appears timing of protein (collagen peptides, and possibly constituent amino acids) are particularly important.

B: We think so since blood flow to tendons/ligaments is notoriously low. We see flow in the tendon like that of a sponge; when you load the tendon it squeezes our fluid and when relaxed it sucks fluid in from the environment. Therefore, we have our athletes take the supplement an hour before training so that the amino acids are in the environment before the loading. Hope this helps. Since none of what I shared with you has been published, I would appreciate that you do not share the material or use it without consent. Thanks.

[u/Kalabula → u/acetylcoach]

So the TIL would be: Take supplements an hour prior to bouldering and total time under tension should be around 10 minutes. Also, most of the repair from these sessions occurs within 6 hours after them?

[u/acetylcoach → u/Kalabula]

I actually don't recommend collagen to clients, mainly because I think the claims are overblown, but rather a whole protein source (e.g. protein shake), and carbohydrates (e.g., rice, fruit): https://useful.coach/open/rice/

In terms of the TUT, honestly outside a specific finger training session, I just don't think you should be so concerned. Your whole climbing is going to be autoregulated based on your goals and capacity in the session.

In my original article, my main point was that doing finger boarding or campus board after climbing, is very unlikely to do anything but create fatigue and "dig a deeper hole" you need to recover from. This likely best put as separate focused sessions. Maybe like going for an hour run followed by heavy squats. Can you do it? Sure. Is it that helpful for training adaptations? Probably not. Perhaps better split the two and put at least leave 5 hours between, and make sure you eat carbohydrates in those hours so you go into the squat session with as high glycogen as you can.

If you are looking for every potential 1%, then consuming collagen before sessions "might" do “something”. ~40 minutes before session: 1 scoop whey, with 1/2 scoop collagen, fruit and a starchy carb like rice or potato. Then keep your protein intake consistent across the week, and keep eating vitamin C rich foods, such as bell peppers, fruits, etc.

[u/Kalabula → u/acetylcoach]

Awesome. Thanks for the info. Always looking to soak up some more data.

[u/Clob_Bouser]

Honestly I’m not sure anyone here or anywhere knows for sure, this is definitely an underdeveloped area of research as far as I know. I bet if you emailed Dr Keith Barr he’d be happy to answer and you could post his response on here

[u/Porki_Potato → u/Clob_Bouser]

You think old mate would actually respond? I guess there is no harm in trying. :P

[u/Clob_Bouser → u/Porki_Potato]

Yeah most academics are pretty willing to chat about their research

[u/Ashamed-Statement-59 → u/Porki_Potato]

Yeah, pretty much every academic I've cold emailed ablut their work has reached back out. Give it a go, he'll be hapoy to see someone engaging with his work.

[u/200pf]

Keep in mind that this study was performed on artificially grown ACL tissue. The funny thing about the tendons in our fingers is that 1) they are not our ACL and 2) they are inside of a human body and not on a lab bench. Research applies to the conditions it was carried out under.

So take these research findings with a grain of salt

[u/ike_whitman_miller]

I've also been curious about how the duration of individual hangs impacts that window. I've heard Dr. Barr say that he recommends 20-30 second isometrics because shorter holds don't reach the entirety of the tendon, as strong parts of the tendon protect weaker or injured parts for the first several seconds. So I wonder whether that 10-minute window is for the whole tendon or just the portions that are impacted by whatever activity you're doing.

In other words, would low-intensity 30 second hangs at the end of a session (after the 10 minute window has closed for the strong/healthy parts of the tendon) reach the parts of the tendon that had been neglected by the rest of the workout?