I just posted a study in the peer-reviewed studies section. I thought it was very interesting and I think it pertains to training for the vertical jump (even though the study was aimed more at addressing why people who always wear high heels feel pain without them).
This is the study: http://www.adarq.org/forum/peer-reviewed-studies-discussion/tendon-muscle-joint-stiffness/
it's the bottom one in the thread
An article that summarizes it is here: http://jeb.biologists.org/cgi/content/full/213/15/i?maxtoshow=&hits=10&RESULTFORMAT=&fulltext=high+heels&searchid=1&FIRSTINDEX=0&resourcetype=HWCIT
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The study focuses on women who had worn high heels for 2 years or more. They then studied the calf muscle and achilles tendon to find out the effects of the high heels. They found that the calf muscles are shortened:
"the high heel wearers' muscle fibres were 13% shorter than those of the women who wore flat shoes"
The researches then asked: "by shortening the fibres, the muscles would have to contract more to shorten by the same length, and if this was the case the high heel fans' calf muscles could no longer function optimally and thus would produce less force than the flat shoe wearer's calf muscles. Had the shortened muscle fibres made it more difficult for high heel addicts to walk efficiently?"
They found out that: "The tendon had not lengthened to compensate for the shorter calf muscle. However, the high heel fans' tendons were much thicker and stiffer than the flat shoe wearers'. Narici and his team realised that by thickening and stiffening, the Achilles' tendon compensates for the shortened muscle fibres in the calf muscle, allowing the fashion addicts' calf muscles to function optimally as they walk"
So in conclusion the effect of the elevated heel was on increased tendon stiffness, ultimately there is a down side in that you lose ankle mobility. However, the increased in tendon stiffness is a huge positive. I think it was on kelly baggett's site where I read something that stated that elite jumpers had tendon stiffness greater than the norm. Furthermore, in another study posted here there is more favorable evidence for the advantages of tendon stiffness: "the stiffness of tendon structures has a favorable effect on stretch-shortening cycle exercise, possibly due to adequate storage and recoil of elastic energy."
i put some studies below.. this is always a tricky topic, because some studies contradict each other.. but basically, you want to increase tendon tensile strength/composition, but you want those tendons to be compliant under ballistic movements.. you want increased stiffness of the muscle & compliance of the tendon during a ballistic movement, this will result in greater elastic energy utilization and more force produced eccentrically in the muscles.
the key word they used above is "thicker", i'm sure if the gastrocs become tighter, those thicker tendons would become more compliant during walking etc.. did they talk about compliance?
most studies i've seen show a negative effect of "lack of compliance" in the tendons and sprint/cmj/rvj performance, less negative of an effect on squat jump.
a more effective way of improving the thickness of tendons, would be to build work capacity (frequency/volume/intensity) of reactive work.. lower level reactive drills, performed near maximally or maximally, will place quite a large load on the tendons and induce that stimulus for growth/adaptation, with much more specificity to sport than modifying shoes etc.
So by wearing elevated training shoes, wouldn't we be eliciting somewhat these favorable adaptations (increased tendon stiffness). Then with a proper stretching routine you could probably maintain ankle mobility and calf flexibility and get the best of both worlds--you'd have the added stiffness of the tendon as well as the increased range for the calf to contract over.
Elasticity of tendon structures of the lower limbs in sprinters
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.
