coolio+++1 good post.

dangg...thanks. Thats exactly what I was looking for.

I wonder if that bit on the calf means that not starting on the ball of the foot, but standing on the heel and rotating onto the ball as you jump would give you a more explosive force, more time and room to generate power through speed. Kinda like throwing a punch from half-way versus from full distance.

I would guess that best way to get the most explosive force from the calves would be to start on the balls of your feet, drop down to heals close to or touching the ground ,and then returning to the balls of the feet.  This would put the calf muscle through a stretch shorten cycle http://en.wikipedia.org/wiki/Stretch_shortening_cycle that would maximize their explosive power.

The only reason I suggested starting on the balls of the feet and sinking down, is that you often see this action when people jump.  Some people start with their heals raised when their legs are still straight, some do a little hop and land on the balls of their feet and some raise their heals as they squat. It just seems pretty common to raise the heals before the extension phase of the jump and to me this makes sense because it pre-loads the calves so they can more explosively contract.  Do you think it is better to start flat footed or am I misunderstanding you?  I truly want to know because I am trying to improve my jumping ability.  I am also curious as to what you think about the following studies.  One indicates that the power contribution of the muscles that extend the ankles is about the same as the muscles that extend the hips
http://www.ncbi.nlm.nih.gov/pubmed/3594313?ordinalpos=13&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum
and the second one http://www.ncbi.nlm.nih.gov/pubmed/15574084?ordinalpos=1&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_DiscoveryPanel.Pubmed_Discovery_RA that indicates that in all but maximal jumps the contribution of the muscles extending the ankles is actually more than that of the hips (see table of data from the study below.  Power outputs are in Joules).

Jump Height	Power produced at ankle	Power produced at knee	Power produced at hip	Total power produced
Low	1.8 (40.44%)	1.62(36.40%)	1.03(23.14%)	4.45
High	1.97(35.30%)	1.77(31.72%)	1.84(32.97%)	5.58
Max	2.06(28.45%)	1.94(26.79%)	3.24(44.75%)	7.24

Again I am not trying to pick a fight, I am just trying to understand the different information I am getting from different sources.

Hmm, while the bold is true it doesn't necessarily tell the whole story.

For example, when "loading" a broad jump you bend at the hips and knees while the arms swing back. As you start to jump you roll forward onto your toes while the hips and knees start extending and the arms swing forward. Unfortunately, based upon the bold statement above and reading through the rest of the abstract, it does not look like they take into account the power generation in terms of how each contributes to the next. If you look at a picture or video of a broad jump (there's one in maximizing sprints and jumps), you'll see that the hips, knees and arms contribute heavily towards accelerating the jumping motion while the ankles are clearly one of the last parts to contract and provide force. Since there is already upwards momentum generated from the hips, knees and arms obviously the ankles are going to close their angle faster (and thus supposedly "generate" more force) whereas some of it is the momentum already attained from the previous force exertions.

Looking at the linked segment method and specifically and inverse dynamics where they calculate based on angular acceleration.. yeah, that's what we want to avoid because of said force already generated before the other joint angle starts extending (in this case plantar flexion of the ankle).

http://www.sfu.ca/~jmorriso/kin380/link_segment_analysis.pdf
http://www.univie.ac.at/cga/teach-in/inverse-dynamics.html


In any case, there are a few relevant facts we can determine from the comparison of broad jump vs. vertical leap (in the first study). Namely, we see that broad jump tends to have more ankle force while vertical leap tends to have more hamstring involvement. This is consistent because we see that in broad jump there is often a rocking onto of the toes (either before or during the jump -- will cover this in the next quoted section) which can utilize the stretch-shorten cycle to gain power for jumping. On the other hand, there is very little action of this during a vertical leap (often do not rock onto the toes or go from flat foot), so the stretch-shorten cycle is blunted and the hamstrings must take up more slack in extending the knees and hips.

And yes, the hamstrings do both since they insert on the tibia and connect to the pelvis over both the knee and hip joints. This is also why I am a bit wary of the low hamstring involvement in both of the studies because the hamstrings just DON'T extend the knee joint but also work at the hip joint. But this is minor because of the huge ankle involvement both studies seem to think... which is obviously not true. I detailed that above though so.. yeah whatever.


With standing broad jump there are two ways you can utilize the stretch-shorten cycle.

1. One is starting off on the toes, sinking down (aka letting the muscles RELAX and stretch), then explode into the jump.

2. The other is starting flat footed, loading the jump (bending at knees, hips, arms swing back), then as shift the weight forward onto the toes thus dorsiflexing the ankle. This will also load the gastroc and soleus which is exactly similar to "sinking down" and then exploding in the jump.

I personally utilize the second one, and I think it is a bit superior (looking at vids of NFL combine jumps on youtube) because starting up on the toes relies on tension to be present in the muscles. Sinking down generally does not alleviate all of the tension and the muscles MUST be relaxed to get the maximum effect of the stretch-shorten cycle. If the muscles are tense "sinking down" the muscles spindles detect less of a stretch which translates into the spinal cord sending less force contraction message to the muscles.


I think that about covers it.