Misunderstood contraction types – Frog helper

A response to the Misunderstood Activity
created by Michelle Laurence (@Michelle Laurence)

Number of views: 192

I teach in a first year University students in the Kinesiology program. Specifically I teach Musculoskeletal Anatomy. Students struggle (especially in the remote learning scenario we faced this year) to understand the difference of concentric and eccentric contractions. Briefly a concentric contraction is one where the muscle is contracting and simultaneously shortening, while an eccentric contraction the muscle is also contracting and simultaneously lengthening. This frog is not passively sitting on this branch. She is concentrically contracting her fingers and toes (correct terminology for frog?) to maintain her position on the branch. In doing so, she is meeting the effect of gravity to pull her off the branch.
The acrobat
Since one leg has fallen from the branch, she is failing to resist the pull of gravity. How gravity is countered will determine if she is concentrically contracting her fingers and toes (thereby closing them around the branch) or should the pull of gravity overcome her ability to continue the concentric contraction, then her muscles will continue to contract but lengthen as her body slides off the branch and she slowly release her grip as her weight succumbs to the effect of gravity. I often forget to focus on the roll of gravity in differentiating between these contractions.

The slow fall of these frogs off the branch also demonstrate the difference between concentric contraction (where the muscle can overcome the effect of gravity) and eccentric contraction when gravity wins over the muscles ability to produce force.
https://media.gettyimages.com/videos/redeyed-tree-frog-stepping-on-top-of-other-frog-perched-on-twig-it-video-id559-135

This exercise really helped me discover and breakdown the misunderstandings students have with this concept.