I thought you were argueing that stiffer tendons = higher/faster ground rection forces whereas the study above seems to add support to the opposite?
When you gain flexibility through an effective stretching program is it because the muscle or the tendon becomes more pliable?
It’s only rumours and hardly scientific but Kadour Ziani stretches for hours daily and his vertical leap is crazy plus he is skinny as a rake and imo relies very much upon his tendon elasticity.
Exactly Cheetah you are correct. Another name for compliance is ELASTICITY, as we know the more elastic a tendon is, the faster its stretch shortening cycle,the more likely ground reaction forces will be high. A stiffer tendon is likely to be inelastic, in other words more muscle effort will be needed to stretch that tendon. People misinterpret stiffness for elasticity and elasticity for stiffness. It is fair to say that the muscle tendon complex as a whole would be able to produce high forces and yet be elastic at the same time if the tendon is elastic in nature or compliant.
Endurance training increases tendon stiffness and sprint training improves compliance do another search… If you have “Science And Practice of Strength Training”
By Vladimir M. Zatsiorsky, William J. Kraemer then read page 35 “Muscle and Tendon Elasticity”.
http://www.shobix.co.jp/ijshs/TempFiles/journal/4/20050098.pdf
Check out
Section 4.1 “Effects of sprint and endurance training”
Simulation of Biceps Femoris Musculotendon Mechanics during the Swing Phase of Sprinting
* Autores: Darryl G. Thelen, Thomas M. Best, Elisabeth S. Chumanov, Stephen C. Swanson, Bryan C. Heiderscheit
* Localización: Medicine & Science in Sports & exercise: Official Journal of the American College of Sports Medicine, ISSN 0195-9131, Vol. 37, Nº. 11, 2005 , pags. 1931-1938
* Resumen:
o
Introduction/Purpose: Characterization of hamstring mechanics during sprinting is fundamental to understanding musculotendon injury mechanisms. The objective of this study was to use muscle-actuated forward dynamic simulations to investigate musculotendon mechanics of the biceps femoris long head during the swing phase of sprinting.
Methods: We used a three-dimensional linked segment model with 26 Hill-type musculotendon actuators to simulate swing phase dynamics. Muscle excitations were computed that drove the linked segment model to track measured hip and knee motion of an individual sprinting on a treadmill. The simulations were used to investigate the effect of tendon compliance on the excursions and power development of the muscle and tendinous components of the biceps femoris.
Results: The biceps femoris musculotendon complex underwent a stretch-shortening cycle over the latter half of swing phase, with the shortening portion occurring in the final 10% of the gait cycle. Biceps femoris excitation increased markedly between 70 and 80% of the gait cycle and continued through the end of swing. Following the onset of excitation, stretch of the muscle component slowed considerably while the tendon lengthened and stored elastic energy. Simulating the sprinting movement with a more compliant tendon increased tendon elastic energy storage, thereby reducing peak muscle stretch and negative muscle work.
Conclusions: Muscle-actuated forward dynamic simulation provides a powerful approach for investigating biomechanical factors that may contribute to the occurrence of hamstring musculotendon injuries.Do a search on the internet to see if there is data.
Endurance training increases tendon stiffness and sprint training improves compliance do another search
I thought you were argueing that stiffer tendons = higher/faster ground rection forces whereas the study above seems to add support to the opposite?
You guys got me wrong, I was not argueing, I simply asked if there were any experimental data to support the statements, as I thought Martin had access to some lab instruments. I then proceeded to present my training monitoring experience on GTC and GRF and even posted a study that backed up what Martin had written. The study I posted on endurance runners/sprinters tendon stiffness was not for arguing purposes either, it was just what I found and I think it can not be dismissed but rather understood in the underlying physiology… after all it is a scientific study.
Re. the article by Keitaro Kubo, it seems that forceful elongation (like what happens in plyometrics and sprinting, for istance) would more strongly affect the tendon compliance, and that would be in line with a study I had found on eccentric training and increased tendon compliance.
If this is so, will “normal” stretching actually affect tendon compliance in your opinion?
Yes something as simple as stretching seems to improve the compliance of tendons. Massage probably aids tendon compliance as well. Stretching decreases viscosity of tendons but increases elasticity.
Check out the link below
What about stretch during weight lifting, for example good-mornings. If you do the exercise with maximal range, it does increase flexibility while increasing strength, but what effects does it have on viscosity and elasticity?
Good question. I think that stretching and resistance training should be kept apart and done in different sessions.
Sometimes when applying physics we can miss the beat. There may not always be absolute correct answer.
Stiffness is the ratio of stress to strain in a loaded material, that is , the stress divided by the relative amount of change in shape. By definition alone stiffer tendons will elicit greater elastic energy - law of reaction- greater force for deformation, greater energy return. This increased energy return comes at a cost, in that ^ muscle force is required.
You would be right, if tendons were so stiff that they wouldn’t deform back to normal however human tendons are no were near that stiffness. Even asphalt roads have a degree of elasticity.
I favor stiffer tendons- but you need to be strong to generate the required F to deform them. However as an evolutionary trait, it wouldn’t make sense that those with stiffer tendons wouldn’t be strong, as they wouldn’t be able to move efficiently.
When talking about tendons we must talk about the muscle tendon complex. Tendons are not perfect springs as they have viscosity and have to work in tandem with muscle hence using the pure physics definition is incorrect. Biological systems are generally imperfect they do not follow a Euclidean perfection. As a given a stiffer tendon is good but a stiff compliant tendon is the key. Viscosity leads to resistance in stretch leading to loss of energy. Improving elasticity (compliance) is very important. There is no point in developing stiffness without maintaining or increasing elasticity. An elastic tendon is beneficial a stiffer tendon will NOT necessarily lead to an improvement in performance without an improvement in elasticity/compliance.
You may favour stiffer tendons but nature favours compliant tendons.
Its not a question of me being right the research says that compliant tendons are needed for faster sprinting as plain and simple as that. You want tendons that are more complaint but muscles that can be stiffer when tendons are doing the stretching. The hill model alludes to this. Yes stiffness is good but compliance even more.
I think you are mixing up stiffness of muscle with stiffness of tendon. You want muscle to be stiff when applying force but tendons to be compliant when energy is TRANSFERED from the muscle.
As always happens on this forum some people dont bother to read the info presented before them and digest what is really being said.
I will make it clear once more then I won’t bother.
Greater GRF= More compliant tendons. Stretching improves compliance in tendons along with plyo.
Strength training is useful for developing stiffness. Having a more compliant tendon DOESN’T, I REPEAT DOESN’T lead to a decrease in stiffness of the muscle tendon complex.
Having JUST STIFF tendons with low ELASTICITY/COMPLIANCE leads to loss of energy through heat.
NO ONE IS SAYING THAT TENDONS ARE ABSOLUTELY STIFF.
Yes stiffer but with more elasticity.
Having had a debate with another sports science enthusiast on this very same issue, I thought I might interject.
After arguing back and forth for a while, we decided to go straight to the source and emailed Dr. Keitarou Kubo, a researcher in this very topic. Here is part of our email followed by his response:
Us:
“Secondly, if compliant tendons are better for stretch-shortening cycle performance, how can more compliant tendons lead to better sprint or jump performance if the tendon deforms more once force is applied to it? Wouldn’t this cause the ground contact times to increase during sprinting or jumping?”
and
Dr. Kubo:
“Certainly, more more complaint tendon would be harmful for transmitting muscle force to bone. In fact, we reported that tendon stiffness decreased and EMD elongated after 20-days bed rest. I believe that the optimal compliance (or stiffness) of tendon would be in existence.”
So, from his response, it is clear that one would not want more compliant tendons for sprinting, though there could be an optimal stiffness level.
“Another sports science enthusiast…” hmmm.
Read what I typed,
"Strength training is useful for developing stiffness. Having a more compliant tendon DOESN’T, I REPEAT DOESN’T lead to a decrease in stiffness of the muscle tendon complex.
Having JUST STIFF tendons with low ELASTICITY/COMPLIANCE leads to loss of energy through heat.
NO ONE IS SAYING THAT TENDONS ARE ABSOLUTELY STIFF.
Yes stiffer but with more elasticity."
Can’t people deduce for themselves that I am not advocating JUST compliance and no stiffness?
No one is advocating that resistance training or strength training should be ignored. How many people stretch to improve tendon compliance?
Stiffness will take care of itself through strength and resistance training but not necessarily elasticity.
Having more compliant tendons does not affect stiffness.
I repeat no one is advocating JUST compliance on its own.
May I add that if you ask the right questions you get the right answers.
Answer this.
You have two athletes A and B with the same stiffness qualities. B has more compliant tendons you know elastic tendons. Who will have a shorter ground contact time?
I recently aquired “The Vertical Project” (dont worry- I didn’t pay for it!). Interestingly one exercise was aimed directly at increasing the compliance of the achilles tendon. Using a pair of strength shoes, you lower your heels over the back of the shoes to stretch the achilles, you then bounce but only using the lower ROM so as the bounce is coming from the elongated tendon. This is continued for upto a minute with tendon massage and stretching in between sets. I was sceptical at first but after some of the research presented in this thread it seems as though this drill may actually help achilles compliance.
Also, when a static stretching programme is used and gains are made in ROM, are these gains in the muscles or tendons? If muscle stiffness and tendon compliance is key then shouldn’t stetches be aimed at tendons more than muscles (if possible i.e. contracting the muscle under stretch to hit tendon).
Compliant tendons and stiffer muscles, maybe . If we use consider MTC (muscle tendon complex) than an increase in the stiffness of the muscle-tendon complex should result in a higher RFD.
Greater GRF= More compliant tendons. Stretching improves compliance in tendons along with plyo.
It should be greater GFR= stiffer MTC. No evidence on stretching & stiffer MTC or compliance & ply training.
The key point here is that the rate of torque development depends on both on the stiffness of the series elastic component( tendon) and the force velocity characteristics of the contractile component (muscle). So you want the muscle to contract fast and than have stiff tendons to transmit force rapidly. ( law or reaction).
There is evidence to support your view. However I think the researchers have got it wrong.
Elasticity of tendon structures of the lower limbs in sprinters
* Kubo,
* Kanehisa,
* Kawakami &
* Fukunaga
*
1 Department of Life Sciences (Sports Sciences), University of Tokyo, Komaba, Meguro-ku, Tokyo, Japan
Correspondence to: Tetsuo Fukunaga PhD
Department of Life Sciences (Sports Sciences), University of Tokyo, Komaba 3-8-1, Meguro-ku, Tokyo 153-8902, Japan.
The present study aims to investigate the elasticity of tendon structures of the lower limbs in sprinters and its relation with sprint performance. Subjects were 10 male sprinters and 14 controls whose anthropometric variables and isometric maximum strength were similar. The elongation (L) of the tendon and aponeurosis of vastus lateralis (VL) and medial gastrocnemius muscles (MG) during isometric knee extension and planter flexion, respectively, were determined using a real-time ultrasonic apparatus in vivo, while the subjects developed a gradually increasing torque from zero (relax) to maximal effort (MVC) within 5 s. While sprinters compared with controls showed significantly greater L above 500 N (about 50% of MVC) and higher dL/dF for VL at less than 20% of MVC during knee extension, there were no significant differences between the two groups in L and dL/dF for MG at every 10% of MVC during plantar flexion. Moreover, the average value of dL/dF above 50% of MVC, proposed as the compliance of tendon structures, did not significantly differ between sprinters and controls in either VL or MG. In a regression analysis within sprinters, the compliance of VL was negatively correlated to 100-m sprint time, r=−0.757 (P < 0.05), but that of MG was not, r=0.228 (P > 0.05). Thus the present results indicate that the elasticity of tendon structures of VL and MG at high force production levels, which might be assumed to associate with the storage and subsequent release of energy during exercises involving the stretch-shortening cycle, are similar in both sprinters and controls. For sprinters, however, the tendon structures of VL are more compliant than that for controls at low force production levels, and its elasticity at high force production levels may influence sprint performance.
Sharmer the MTC is more efficient when tendons are compliant and muscles have the ability to generate greater stiffness.
Has Zatriosky got it wrong?
I wonder.
I think you do not understand the MTC model. Research and computer simulations suggest that they are right. What they are saying is very simple.
By all means improve Stiffness but don’t neglect the elastic strength aspect of stiffness thats all. The hill model of the MTC requires tendons to become more compliant as a muscles ability to generate greater stiffness increases. Having more compliant muscle DOES NOT take away from STIFFNESS. If tendons are compliant then muscles do less work and are less likely to rupture because they will not need to contract eccentrically to aid a less compliant muscle. How is that wrong?
How can you claim that the research is wrong and on what basis? Where is your evidence to refute the research? Explain why they are wrong?
That would make sense but the strength shoe is a no no not good at all. The stretching should not be excessive. You just need to do a small amount to maintain and increase compliance marginally not chronically.
I need to review the J.Biomechanics articles by Farley- their views were the opposite of Zatriosky. I’ll get back to you on this. This is good, at least I need to open up the archives which is a rarity.
What effect does a decrease in viscosity have?
Why is it that many say it is bad to be too flexible?
think of Viscosity this way - in relation to oil
high viscosity oil, up around 80 - 100 is typically used for Gear boxes (its very thick)
High performance engines run a 5-20 viscosity oil, very runny. flows well, so it can lubricate the fast moving parts quickly
From my experience,
100m - 1.2 to 1.5 seconds
Triathlon being tested at the world champs on a couple of weeks.