--- In highjump@yahoogroups.com, amad bing <amadbing@...> wrote:
>
>
>
> To many people get hung up on weights far too early in their
careers. Lifting kills spring.
>
> is that true???
>
I have read in a few websites that a jumper needs to develop
the "fast twitch" or "type II" muscle fibres, which really provide
the spring. The theory seems to be that we all have a varying
proportion of fast twitch fibres and that they are only recruited in
plyometrics and close to one rep maximum lifts.

See:
http://en.wikipedia.org/wiki/Muscle
http://en.wikipedia.org/wiki/Myocyte

In other words, lifting a weight with which you can do more than
three reps doesn't improve your jumping ability. Some say it actually
reduces jumping performance. I am led to understand that performing 4-
12 reps builds muscle bulk, so the jumper becomes heavier!

Of course an athlete would have had to perform months of conditioning
work before attempting such heavy lifts -the risk of injury is too
high. The connective tissues and joints need to be conditioned or you
risk tearing the tendons off the bone! The athletes I deal with are
all too young for anything so intense and I personally am too old (!)
and am not prepared to risk injury just to hang on to a medal.

I don't feel happy squatting too low as I have had knee injuries, but
there is a school of thought which says that you don't fully recruit
the glutes until you do a full squat. I usually take my thighs to
horizontal and then raise. If I go deeper I do feel it in my glutes
later.

I enjoy plyos and have had the interesting sensation of, days later,
feeling tiny parts of my calf muscles twitching and "firing" when I
am sitting still. I don't know if this indicates an improvement in my
muscles' jumping ability but it seemed to indicate that I had caused
some changes in my legs!