[quote author="mortac8" date="1221182160"]Jeremy,
Most climbing harnesses have the attachment point at the hips/butt. Would this tilt the athlete forward upon takeoff? This worry was the reason I used a backpack and attached the assistance at head level (“handle” of the backpack).
There are harnesses used in gait rehabilitation that are worn as vests with a crotch and they evenly distribute the weight and are actually INTENDED to unload the person from above.
Regarding contact times….when I was doing this, they were just squat jumps. They were not plyometric. The contact times were probably about 1 second.
Oh…I was actually talking about contact times in sprinting. Don’t think what I said would apply to jumping (vertically).
btw, you guys realize there is a study on suspended jumps. by some japanese guy. i might have a link somewhere.
Yeah I’ve seen it. I believe it was in NSCA journal in the past year right? I was just saying that I don’t think it’s changing contractile velocity (at least I hadn’t seen any evidence to suggest that it was) despite practically everyone saying that’s the reason behind any benefit it might provide. It’s kinda like when people say lactic acid causes fatigue…[/quote]
The point of unloaded/suspended/assisted jumps would be to recruit muscle fibre faster and reduce the antagonist muscle inhibition of movement. Whilst a basketballer might benefit from jumping quicker, a field jump athlete needs more force or power in the same or slightly lower contact time. If assisted jumps changes the motor units recruited to motor units that contain a higher percentage of type IIB muscle fibre then certainly loading these fibres would increase their cross sectional area with a related increase in strength. Varying the load midset (by a small amount) would stimulate growth of the said fibres. Doing unloaded squat jumps for some sessions and heavier squat jumps for a session would achieve a similar but less dramatic improvement to muscle fibre.
I’m presuming the person (crazyhops) that is doing this exercise as a training method for jumping. If it will help increase limb angular velocity for the initial part of the movement but the overall force production time won’t decrease dramatically for the specific movement. In terms of sprinting, there would be a great improvement in co-ordination of muscle fibres recruited for the block start but only if the goal is speed of movement (ie much shorter ground force times). Imagine if you will, producing the same force of propulsion out of the blocks but in 100 milliseconds less time. Would that not improve overall sprint times?