Submitted by Toast1185 t3_ybyeyq in askscience
AquaDoctor t1_itkf47g wrote
They suddenly fail.
Simple answer is that ligaments don’t bulk up the way muscles do. And while we’ve created multiple supplements and exercises to increase muscle mass, it’s the same ligament holding bones together. A 180lb high school kid who adds 50lb of muscle in college has practically the same ACL he always did.
ACLs typically fail with a pivot and valgus load to the knee. That’s a twist and the knee bends in toward the other knee, usually from a force like a tackle or other hit.
While ligaments don’t repair themselves as quickly and regularly as bone, they are living tissue so any micro trauma will typically result in repair. I haven’t read any literature on evidence showing cumulative injury to ACLs causing most injury.
Source: I’m an orthopaedic surgeon
andytronic t1_itl4cll wrote
> A 180lb high school kid who adds 50lb of muscle in college has practically the same ACL he always did.
Will they get stronger over time, with increased strength, or do we just live with the ones we're born with?
Jezdak t1_itl60xi wrote
Absolutely bang on with this, but I'd add repeated injuries that cause small amounts of scar tissue each time could theoretically lead to a weakening.
Pretty unusual to have that many significant injuries in exactly the same place though, and I've never seen any studies dealing with it.
Zephrok t1_itl4egb wrote
So Ligaments dont strengthen at all? Rock climbers talk much about finger tendons getting stronger through climbing and training hangboarding. Pro climbers can hang and pull on one finger - I certainly can't.
What is happening there?
Jfrog1 t1_itlj8se wrote
tendons/ligaments do strengthen over time, they just take much longer to strengthen than muscle, or skeletal tissue. Consequently they tend to be the weak link. Think of a power lifter who can squat 600 pounds. The were not able to do that 5 years ago, but with years of training, when they started at being able to just squat 400 pounds, the muscle and ligament tissue adapted and grew to be able to withstand the stress of their surroundings.
[deleted] t1_itlsy58 wrote
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yersiniaD t1_itl5asb wrote
The tendons in the fingers are joined to and powered by muscles in the forearm, so grip strength can be increased by muscle training. Ligaments join bone to bone so they can't be developed through training.
runningwithtigers t1_itmqcod wrote
ACLs do adapt! Check out Powerlifter's ACL thickness vs general population.
AquaDoctor t1_itnurcu wrote
Very specific article looking at heavy weight lifting in very specific athletes. "All athletes in our study began training before or during their pubertal growth spurt." And not to be a complete jerk about it, but you've posted a few comments with this article, published in a journal that went out of business in 2014 and looking at 9 (NINE!) total weight lifters. I'm all for looking at new data, but this isn't it.
SuperSimpleSam t1_itv2ni4 wrote
It would also be more useful showing the ligaments getting thicker rather than a comparison to the general population since the people that are able to lift heavier weights might be ones with thicker ligaments.
AquaDoctor t1_itvqi3h wrote
That's such a great point. Selection Bias. The ones with the thicker ligaments were able to lift heavy weight or stayed in the sport. The ones with regular ligaments either tore their ACLs or dropped out. It would be like saying that playing basketball makes you taller. Great thought. Thanks
dave200204 t1_itllkae wrote
Most grip strength training is really working your forearms. If you look closely at Rock climbers arms they usually have well defined biceps, triceps and forearms.
AquaDoctor t1_itntxof wrote
Tendons attach muscles to bones. Ligaments attach bones to bones. So any answers confusing the two need to be corrected. yersiniaD has the right answer.
abark006 t1_itltakh wrote
I’ve experienced this first hand. I’ve actually plotted charts and have noticed for my height, around 6’3 I feel noticeable strain on my knees at around 230 pounds when playing basketball. Black in college I was able to play football at 235 but being young helps with that lol
[deleted] t1_itkz35w wrote
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RevFernie t1_itlalz8 wrote
Have you had to treat any Brazilian jiu-jitsu folk with torn ACL from "heel hooks" a submission that twists the knee?
AquaDoctor t1_itnuy5q wrote
I've treated a multitude of BJJ athletes. No ACLs though. They are all monsters. Constant injury and constantly looking to get back on the mat to fight. Just monsters.
RedJamie t1_itlfvzu wrote
Do you enjoy your career as a physician? Or do you have any regrets about the process?
AquaDoctor t1_itnvin0 wrote
Love what I do. It's become more difficult to practice medicine with insurances dictating what you can and can not order. In a perfect world we could order tests as needed and figure things out without regard to cost. But we live in the real world, unfortunately.
CodeBlue614 t1_itloovc wrote
Nice explanation! Just curious, in non-contact ACL tears, is the process any different? When I was a freshman in college, my team had something like 8 ACL tears over the course of the season, and 1 in particular was an offensive lineman who just came out of his stance and didn’t contact anyone on the play. At the time, some of my teammates blamed all the injuries on the coaches having too many full-contact practices because they thought it would make us tougher.
AquaDoctor t1_itnv5du wrote
I think there's some thought to the idea that the fatigue is in relation to the musculature in the knee, and once that fails to protect transition and rotation in the knee, then they tear the ACL. But look, we are constantly learning about the body and changing our thought patterns. Nothing is set in stone.
runningwithtigers t1_itmq3bn wrote
Dynamic knee valgus occurs AFTER the ACL is already ruptured.
Zhang et al (2019) Sports Med, 49(3)
Powerlifters have been shown to have thicker ACLs than the general pop
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3535026/
pivot/valgus load to the knee is the old way of thinking about ACL injuries.
Complete ACL tears have shown to heal in as little as 3 months.
[deleted] t1_itndni3 wrote
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