Tendon adaptation & muscle adaptation

For you nerdy ones, I have a question (as I am also nerdy!) about the adaptation of tendons to stimuli, to be contrasted against the body of research on muscle adaptation. (Could be the wrong forum for this kind of nerding off...but it felt most relevant here.)

Background on me & this topic: I am a B.S. Mechanical Engineering working full-time as a personal trainer, owner of The Fit Life Personal Training. I have invested...nearly 1000 hours (some 6 hours per week reading & experimenting; considerably more than the time spent earning my degree!) in the last three years to learning the body, how it works, how it adapts, how to challenge it optimally, and how to recover optimally. So while reading various materials (and referenced research) from Precision Nutrition about nutrient timing for muscle growth, and hypotheses about recovery processes in Mark Rippetoe's Practical Programming for Strength, AND while thinking on the enormous tendonous & ligamentous strength required of body weight athletes (I am personally unilateral calisthenics minded, more than gymnastics, but we are all family!), I got to wondering about the established research on tendon adaptation.

Specifically, I found this conclusion, "it appears that the tendon tissue response, contrary to muscle, is independent of stress levels/contraction type; indicating that this tissue is less sensitive than skeletal muscle to differences in mechanical stimulus" (Heinemeier).

Anyone with a background in kinesiology/physiology or a significant interest in this research have some insight about just what optimal loading causes tendon growth and time frames for recovery (possibly dependent upon and correlated with trainee experience)?

And, to keep things relevant to this particular population, what is the impact on that recovery cycle on our development as athletes, in the context of developing surrounding, acting muscle? (Examples: impact on elbow tendon supercompensation on development of advanced straight-arm skills like the crosses & levers, compared to impact of biceps growth on those same skills; impact of supraspinatus & infraspinatus tendons on planche training, compared to development of same-named muscles, posterior & anterior deltoid, and rhomboids.)

REFERENCE

Heinemeier, Katja M. Adaptation of tendon and muscle connective tissue to mechanical loading: Involvement of collagen-inducing growth factors. Institute of Sports Medicine, Bispebjerg Hospital, Copenhagen. 2007

I found this during some searching of the forum, by Coach Sommer:

Coach Sommer said:

A Word of Caution

The metabolic rate of connective tissue (tendons and ligaments) is approximately 1/10th that of muscular tissue. This means that connective tissue improves it's strength and flexibility at 1/10th the speed of muscular tissue; and that it also heals TEN times slower. For example, when comparing a slight muscular pull that would require 3 days to heal to a slight connective tissue pull of the same magnitude, the slight connective tissue pull would require 30 days to heal. Yes, that is correct - a full 30 days. This is not to imply that the joint will be disfunctional for the entire 30 day period, but that it will require that period of time to regain 100% functionality and stability.

I am now also curious about relative strength improvements in tendonous tissues (given appropriate compensation time). It is known that tendons increase in cross-sectional area after collagen turnover...but to what degree of muscular development is tendon strength insufficient to support this or that loaded movement (like the various joint pains of your typical amateur bodybuilder in training, because of overemphasized isolation movements)?

Hopefully, I'm not the only one talking on these points, lest I just be wasting data space, but it does seem interesting to study!

This article has some references which I think might be of use to you:

http://rheumatology.oxfordjournals.org/ ... /1444.full

Also you could research prolotherapy to learn more about tendon strengthening and proposed mechanisms of action.

A lot of this has to do with golgi tendon reflex inhibition. Your body has some automatic checks in place that help keep you from tarding out too hard in this area, but you can over-ride them if you have been training for a while.

Great link! I saw no mention of ionic charge and macrophages:

Eccentrics are how you damage tissue, and damaged tissue release more positive ions into the surrounding area than just the normal increase due to plasmalemmal AP conduction. Those ions are what draw macrophages to the area, and macrophages are what activate satellite cells and help them differentiate. This will certainly affect healing at the musculotendinous junction but I don't know if that will affect the tendon further away. It is an interesting idea though

Eccentrics don't cause more force in the tendon, it's only per muscle fiber. Important distinction when thinking about this sort of thing. The unit as a whole will experience less force at any given submaximal load moment during eccentric action than isometric or concentric. Each fiber that is working, however, will experience more stress and therefore more strain than usual.

Anyhow, this is certainly an interesting area of study