Anatomy Muscle Torque Problem Help?

[jaybanks930]

Hey, I am a bit confused by this problem regarding muscle torques and work during running. I am just having a hard time interpreting the graph. It is my understanding that the action is concentric when the curves are on the same side of the 0 line and eccentric when they are on opposite sides. I'm unsure however of how to tell which muscle group is predominant from the graph. I have attempted a few of the problems based on this logic, but I am not confident in my answers at all. Not looking for the solutions necessarily, but does anyone know how to interpret the graph and specifically to tell which muscle group is predominant and what action is occurring (flexion/extension)? My professor never explained it to us but it's on the assignment. Any help is appreciated. Thanks in advance!

[imatfaal]

When you are talking muscles acting within larger groups I think eccentric and concentric are used as follows

 

-Concentric: when a joint is flexing and the muscles in question are shortening (ie agonists to the flexion) or when a joint is extending and the muscles are extending

(I would hazard an example as biceps and lifting a weight by flexing the elbow for concentric flexion, and triceps (some of it) in extension

 

-Eccentric: when a joint is flexing and the muscles in question are lengthening (ie antagonists to the flexion) or the joint is extending and the muscles are shortening

(this is less usual and harder to grasp - it only comes about with other muscles or forces involved. The best example is the squat - your hips and your knees are both flexing but both Glut Max for hips and Quadriceps for knees are working against this motion (ie they are antagonists); the motion is caused mainly by gravity - GlutMax and Quadriceps are controlling and slowing motion.

 

This is much more complicated in the running pace - but the same idea applies. You have to consider what is happening to the knee joint (ie its rate of rotation) - and why at every moment; is it moving because of muscle action, because of inertia (of both the lower leg and/or the body), through action of gravity, or a combination of all the above.

 

Function will stroll by soon and set me right

---

 

To explain the graph - the dotted line is the angular velocity which is in radians per second (ie the change in angle over time). When the line is below the axis the knee is flexing - ie the foot is moving clockwise with respect to the knee. When the line is above the axis the knee is extending - the foot is moving anticlockwise wrto the knee

 

And my guest for my next meeting have arrived and I have to leave it there

[jaybanks930]

When you are talking muscles acting within larger groups I think eccentric and concentric are used as follows

 

-Concentric: when a joint is flexing and the muscles in question are shortening (ie agonists to the flexion) or when a joint is extending and the muscles are extending

(I would hazard an example as biceps and lifting a weight by flexing the elbow for concentric flexion, and triceps (some of it) in extension

 

-Eccentric: when a joint is flexing and the muscles in question are lengthening (ie antagonists to the flexion) or the joint is extending and the muscles are shortening

(this is less usual and harder to grasp - it only comes about with other muscles or forces involved. The best example is the squat - your hips and your knees are both flexing but both Glut Max for hips and Quadriceps for knees are working against this motion (ie they are antagonists); the motion is caused mainly by gravity - GlutMax and Quadriceps are controlling and slowing motion.

 

This is much more complicated in the running pace - but the same idea applies. You have to consider what is happening to the knee joint (ie its rate of rotation) - and why at every moment; is it moving because of muscle action, because of inertia (of both the lower leg and/or the body), through action of gravity, or a combination of all the above.

 

Function will stroll by soon and set me right

---

 

To explain the graph - the dotted line is the angular velocity which is in radians per second (ie the change in angle over time). When the line is below the axis the knee is flexing - ie the foot is moving clockwise with respect to the knee. When the line is above the axis the knee is extending - the foot is moving anticlockwise wrto the knee

 

And my guest for my next meeting have arrived and I have to leave it there

 

Thanks so much! I actually get it now. I realize that angular velocity tells you which way the joint is moving but resultant joint torque tells you which muscle is predominant.

[imatfaal]

 

Thanks so much! I actually get it now. I realize that angular velocity tells you which way the joint is moving but resultant joint torque tells you which muscle is predominant.

 

Glad my old memories have helped.

 

From a physical view (ie more physics as the science than anatomy) you could also think about the relationship mathematically between angular velocity and net torque. I would avoid getting too tied up in the vector notation etc but getting your head around angular velocity, and importantly the link between change in angular velocity (ie angular acceleration) and net torque would be very useful. But a word of warning - analysing any biological systems movement in terms of classical mechanics requires a big dose of simplification and even then it is complex