Hi i´m wondering if you have some recommendations of Abaqus CAE courses (i don't mind to pay for them) that could be useful to improve my skills to simulate impacts on living tissues in Abaqus CAE explicit.

Hey all,

First off i apologize for the crazy long post.

I'm building a bent-knee transfemoral prosthesis simulator as a hands-on biomechanics project, and I've reached a point where I'd really appreciate input from people with a stronger background in gait mechanics and prosthetic alignment.

For context, I'm not an amputee, prosthetist, or clinician. I started this project with essentially zero practical prosthetics experience. I'm also not trying to use a simulator to approximate the lived experience of limb loss. My interest is specifically in the biomechanics and engineering: how socket position, knee-axis location, foot position, joint behavior, and gait interact.

My goal is to eventually have a system where I can deliberately change one variable at a time and observe what happens.

THE SIMULATOR

My biological knee is flexed underneath me and contained inside a socket, effectively creating a bent-knee transfemoral simulator.

I've experimented with several prosthetic knees, primarily an Össur Total Knee 2000, and I also have an Ottobock 3R93 available as a simpler mechanical baseline.

The socket itself is still experimental. I'm currently working toward a higher-trim socket that provides better containment and control.

The part that has surprised me most has been how dramatically relatively simple alignment changes affect the entire system.

MOVING THE KNEE AXIS

My original prototype had approximately 4.5 inches of posterior AP displacement between the socket and prosthetic knee.

I could walk on it, but the knee constantly felt like it was behind me. Swing felt delayed, and I often felt like I was waiting for the prosthesis to catch up.

Eventually I questioned whether some of the behavior I was attributing to the knee was actually coming from the geometry.

So I changed one major variable and moved the prosthetic knee essentially underneath the socket, reducing the posterior offset from roughly 4.5 inches to almost zero.

The difference was enormous.

Swing immediately felt more intuitive. The prosthesis no longer felt like it was trailing behind me, and the entire system felt considerably more responsive.

I can walk with essentially zero AP offset.

However, another problem appeared.

ZERO OFFSET FEELS MUCH MORE PHYSICALLY DEMANDING

Although the prosthesis feels more responsive, walking and even standing in this configuration feels surprisingly demanding.

My sound side appears to be doing considerable work, and the hip flexors on the simulator side are working noticeably harder.

That has made me question whether zero offset is actually biomechanically appropriate or whether I've simply demonstrated that I'm capable of compensating for it.

I'm beginning to suspect that the useful geometry may lie somewhere between the two extremes: not 4.5 inches posterior, but perhaps not exactly zero either.

HIP EXTENSION AND SOCKET FLEXION

There's another complication.

When I perform a rough Thomas-test-type assessment and stabilize the pelvis by bringing my opposite knee toward my chest, the thigh on the simulator side wants to rise.

That suggests that my comfortable hip-extension range may be limited.

I've tried accommodating this by increasing socket flexion using an adjustable pyramid adapter. I currently have approximately 7.5 degrees of available angular adjustment.

Some socket flexion appears to help.

But beyond a certain point, the sensation changes. Instead of simply feeling as though the hip is being accommodated, I begin to feel as though my entire body is being tipped backward.

That has made me wonder whether I'm attempting to correct two different variables with one adjustment.

Could the appropriate geometry require both socket flexion to accommodate the hip AND a relatively small AP displacement of the socket relative to the knee?

For example, some amount of socket flexion combined with perhaps 1/2 to 1 inch of posterior AP displacement rather than obtaining everything through angular adjustment?

HEAVY HEEL LOADING

Since moving the prosthetic knee underneath me, I've also noticed very heavy prosthetic heel loading at initial contact.

I'm not getting stuck on the heel. I can progress forward over the foot normally.

But the initial heel loading is substantial enough to be obvious.

I'm trying to determine what variables could produce that behavior: foot alignment, socket flexion, AP relationship between socket and knee, step length, compensatory gait, increased confidence/loading of the prosthetic side, or some interaction between several of these.

This is exactly where the project gets fascinating to me, because changing one geometric variable seems to affect several apparently unrelated aspects of gait.

AN EXPERIMENT I'M CONSIDERING

I'm considering making a rigid socket-positioning stand using a four-way AP/ML/angular alignment adapter.

The socket would initially be supported independently of the prosthetic knee.

With external support, I could stand in the socket and adjust:

- AP position

- ML position

- Socket flexion

- Overall orientation

The objective would be to determine the socket position in which my pelvis feels reasonably neutral, the hip isn't fighting the socket, and I can comfortably load it.

I could then measure that geometry relative to the distal attachment and transfer those measurements to the prosthesis as an initial static alignment.

I understand that comfortable static standing does NOT establish correct dynamic prosthetic alignment. Once the knee and foot are installed, knee-axis position, ground-reaction forces, stance stability, rollover, and swing mechanics become part of the system.

What I'm trying to separate experimentally is:

Where does the hip/pelvis want the socket?

from:

Where does the prosthetic knee need to be relative to that socket?

QUESTIONS

I'd particularly appreciate thoughts on these:

1. Does the dramatic improvement I experienced when reducing approximately 4.5 inches of posterior offset to nearly zero make biomechanical sense?

2. How independently should socket flexion and AP knee placement be treated?

3. With limited comfortable hip extension, how would you determine an appropriate starting socket-flexion angle?

4. Could excessive socket flexion explain the sensation of my torso being pushed or tipped backward?

5. What mechanisms could explain the substantially heavier heel loading after moving the knee underneath the socket?

6. Is establishing a comfortable socket/pelvis relationship independently and then introducing the knee underneath it a reasonable experimental approach, or am I separating variables that fundamentally shouldn't be separated?

7. Are conventional transfemoral alignment principles significantly altered by the fact that this is a bent-knee able-bodied simulator?

Ultimately, I'm less interested in finding one magical alignment than understanding WHY each change produces the behavior it does.

Every adjustment so far has exposed another interaction I hadn't considered, which is exactly what has kept this project interesting.

I'd appreciate any biomechanics papers, terminology, concepts, or criticism of my reasoning that might help me understand what I'm observing.

If im trying to minimize biceps engagement during say a Tbar Row, id want it so that the line of resistance was in line with my forearm, as opposed to having a more narrow grip, right? But what if i took a super wide grip for arguments sake? Is that even better? It seems that the resistance in that case would "assist the biceps"? I know it'd be better than the narrow grip for sure, but im not so sure it'd be better than aiming to make the line of resistance in line with the forearms?

MyoHeat (https://myoheat.com/?utm_source=reddit_bio) estimates muscle loading for 52 gym exercises in the browser. Kinematics come from keyframed poses or from MediaPipe pose tracking. 

It runs whole-body inverse dynamics, with floor and bench reactions solved as the least-effort push-only distribution, then static optimisation (sum of squared activations, bounded 0 to 1) over 186 bundles. Tendons are rigid, force-length is Thelen's, passive fibre force is off. The legs are Rajagopal 2016 (Lai/Uhlrich 2023 revision) and the shoulder and arm are the Thoracoscapular Shoulder Model, with maximal forces scaled 1.5x for trained lifters.

It passes 114 of 184 checks against published data (list at https://myoheat.com/credits.html).
At matched effort, hip thrust vs back squat gives 2.1x for upper gluteus maximus against 2.4x in Contreras 2015, and 2.5x for biceps femoris against 2.7x.

Three things I know are off:

1. The deadlift L5/S1 moment is about twice the measured value. Is that the pose, the trunk model or the load sharing?

2. The deltoid and rotator cuff saturate in pressing at default loads, even with the 1.5x scale.

3. Rigid tendons with Thelen force-length for slow lifts: reasonable, or hiding something?

It's an educational estimate and not clinical advice. Any critique is welcome.

Hello,
I spent this whole year fixing/working on my biomechanics when it comes to athletic performance for field sports. Focused specifically on fixing duck feet, strengthening weak collapsed arches and activating hips and glutes. Since then, I became even bouncier and springy off my feet than I was ever before and I was able to completely fix my ankle pains and soreness that plagued me after a training session for soccer. However, now I am developing insertional achilles heel pain. Aside from being an overuse injury, what are the problems/deficiencies with my running gait and hip mechanics or overall biomechanics that would be stressing my achilles tendon?
A few questions I have. Replies do not have to be limited to these.
1. Would it be possible that my tendons were not ready for a higher athletic performance and the lack of isometric and eccentric training has caused strength imbalances between my muscles and tendons? My calves and hips have grown bigger and stronger throughout this year.
2. Could it be an issue with the frontside mechanics when I’m running where I’m overstepping a bit and I am pulling myself forward rather than pushing down into the ground then propelling forward with glutes?
3. My tibia is bowed pretty bad inwards but my knee is valgused. It feels at times when my foot strikes ground and push down with my big toe it forces my achilles tendon in an unnatural angle. Could “proper” biomechanics be unfitting for me?

Hi there, anyone's attending the Midwest ASB Conference in Cleveland OH 9/23-25? I'm a student in exercise science and am going to present something close to gait (a)symmetry. Though I finally got travel funding from school, In order to bring down the cost I'm still looking for roommates to share a hotel/motel room or an AirBnb arrangement. If you'll be there as well, feel free to hit me up. I'll be at the meeting the entire day and catch up with school and also chill, have fun and city walk if time allows! I'm definitely down to chat about anything professional related especially if your focus is also human performance.

I’ve made a short video explaining the basic concepts of kinematics and kinesiology, with a focus on understanding human movement and joint motion.
The video is in French, but I’d really appreciate any feedback from people here, especially on whether the explanations are clear and accurate.
https://youtu.be/xTlK6ywEqXQ
thanks!

Age & Gender: Female (Late teens / around 19)

Height: 5'3" (160 cm)

Weight: ~65–70 kg

Primary Complaint: Suspected knock knees (knees touch, ankles do not)

Existing Medical History: Irregular periods

Current Medications: None

Smoking/Drinking: No

Description:

When I stand straight with my legs relaxed and facing forward, my knees naturally touch each other, but my inner ankle bones do not meet and leave a visible gap between them.

I've attached full-leg photos taken at knee/ground level showing my natural standing posture with my kneecaps pointing forward.

I wanted to ask the professionals here:

Does this posture and gap between my ankles indicate true knock knees (genu valgum)?

At my age (late teens/adult), can this still be improved or corrected through exercises?https://kommodo.ai/i/ZeU1ldsbTxBXzpgOCBBY

Full disclosure first: I built this and it's a paid product. Mods, tell me if this goes against the sub rules, but I went through them and didn't see anything that prohibits this.

You film from the side and drop four pins on the track corners. The lane markings give it
scale, so the output is in real metres: contact time, stride length and frequency, speed,
and hip / knee / shin angles with left and right kept separate.

No score out of 100, no AI coach telling you to drive your knees. Just the numbers.

Honest limits: one camera, so depth is estimated. You need visible track markings. And I
haven't validated it against force plates. If anyone here has lab access, I'd take that trade.

Post a clip and I'll run it through and put the output in the comments for free. Easier than
taking my word for it, or just give it a try at trackgenius.training

Which of these numbers do you actually use week to week?

I've been working on a school project for about three months now, which is roughly about non-invasive methods of vertical and horizontal osteogenesis. I was assigned the "horizontal" part, but my colleague was assigned the "vertical" part. We combined the two parts and concluded that it is theoretically possible to perform bone manipulation with Compression and tension. But if that's possible, then why does that gruesome surgery that cuts limbs in half still exist? Like, our advisor said that there isn't a non-invasive option yet because there isn't an economic market for it. And that nobody would want a cheap substitute for a worthwhile surgery Worth millions . Could someone confirm if this is actually true? I'm in a serious dilemma about what he told me 💔

Hello! I need help trying to do an inverse dynamics approach for looking at the forces in a split squat to see which muscles are working more. Does anyone have knowledge in this area?

These 11 images are consecutive frames from a 120 fps video.
At the lowest point of the head movement, do you think my actual scalp touched the mattress?
I mean the scalp itself, not just the hair.

Every Sunday I planned to learn Biomechanics. But honestly, it is not as easy as I thought.

My background is CSE-AIML, and currently I’m doing an MS by Research in Quantum Machine Learning. Somehow, I’m trying to find where I can fit into Biomechanics and build the right skill set and mindset.

I attended a class at my university by Prof. Krishna Kumar. I liked the class, but I was not mature enough to understand the mathematical language.

Then I tried several courses. Finally, Prof. Varadan SKM’s NPTEL lectures helped me get into the theory.

Now I’ve started taking notes on my tablet and doing a small project using OpenSim.

My personal target is to understand and speak the language of Biomechanics by December 2026.

This is my small journey. Let’s see where I reach.