Re: Jump Training in reduced gravity

[Guest guest]

Randy Dixon wrote:

> My thought was: That by using a bungee cord or rubber tubing and suspending

> it from a height and attaching it to an athlete by a harness that it would

> unload the jumping and they would jump higher, and and at a higher velocity.

To Randy and ST Members:

It seems that the method you're proposing would result in the athlete

experiencing some degree of reduced gravity. I don't know if there have been

specific studies relative to vertical jumping, but reseachers have done quite

a bit of work on the effects of reduced gravity on walking and running. For

example, Farley's research indicated that, even in reduced gravity, the

stiffness of the leg remains constant.

What we also know is that, under prolonged bouts of zero gravity we lose bone

density. We've observed this in space flight. Exercise bikes and treadmills

have been used in the space program for years. Though these are a good form

of cardiovascular exercise, they don't provide the daily resistive forces

needed for bone and muscle maintenance.

In the past, rubber band and bungee devices were designed to address this

issue, but they did not provide the constant force that was necessary for

optimal muscle maintenance in space.

About four years ago, students at Colorado State began developing a machine

that could simulate in a space-like environment the constant resistance we can

get with weights here on earth. Their device looks similar to a weight machine

in a typical gym, but instead of weights, it uses special springs to provide

constant tension. The unit consists of cables and pulleys that are attached to

small units which contain their constant-force springs or force packs. As you

would expect, each pack provides a different amount of resistance. The unit

can also be adjusted for various body types by way of custom length cables.

So what was their exercise of choice? The deadlift. They placed their

machine aboard a KC135 " vomit comet, " and hooked up their test subjects to

various kinds of electrodes and micro pressure sensors.

Although deadlifts, even using a device like this under these conditions,

would seem pretty straightforward, people apparently have different postures

in microgravity, and the research team really wanted to know what happens when

they performed this lift minus a gravity vector. It will be interesting to see

if there are any applications of their microgravity trainer research to earth-

based lifting.

Kindest regards,

Ken Jakalski

Lisle High School

Lisle, IL

[Guest guest]

> In the past, rubber band and bungee devices were designed to

> address this issue, but they did not provide the constant force

> that was necessary for optimal muscle maintenance in space.

It sounds like the CSU students invented a spring-based Soloflex or

Bowflex in which the medium itself, rather than gravity, provides

the resistance. As to force curves, free weights don't provide

constant force throughout a movement on Earth so I'm curious as to

why this is so important in microgravity. Anybody remember the

Nordicflex (or something) that basically matched resistance so that

the force curve was flat throughout the movement? Although the

missing negative would be an issue, I would think that a greater

number of exercises could cover all the angles so to speak. The

fact that NASA's answer to bone loss was aerobic exercise should

tell us all how utterly ignorant and behind-the-times many very

smart people are regarding strength training.

[The use of aerobic exercise for bone maintenance in space travel doesn't

suggest that they are ignorant or behind the times at all. The dose-response

issue with exercise was based on bone mineral maintenance, not bodybuilding.

Trying to mimic the beneficial effects of constant gravitational forces on our

bodies requires much more than just three sets of 12 reps. This remains a

huge issue for space travel, and research continues in this area. ST Co-

moderator, Gray]

Ty Scheske

St. Louis, MO

USA

[Guest guest]

Ty,

One of your statements was slightly incorrect. In human movement (static)

FrDr=FmDm, where Fr is the resistance force multiplied by the Dr (moment arm

distance of the resistance) and Fm is the muscle force multiplied by the Dm

(moment arm distance of the muscle). This is known as torque.

Your statement that the force of free weights changes was not completely

correct. F=ma, therefor the force of the free weight doesn't change, what

does change is the moment arm which causes a change in torque, which then

causes a change in muscle torque which is caused by a change in muscle force.

The idea of constant force machines is to keep the torque the same so that

muscle force remains constant (which imposible because of variations in both

the resistance moment and the muscle moment). The idea behind NASA'a machine

is to keep the resistance force constant (as opposed to the typical

force/elastic curve where force increases with deformation) while allowing

the torque to change through the movement as it does in nature (at least

this was my interpretation of the machines description).

Just to keep the facts straight for intelligent discussions sake,

J s, MS, CSCS, USAW, NSCA-CPT

Assistant Strength & Conditioning Coach

College of ton

Strength Dept.

30 Str.

ton, SC 29424

Ty Scheske wrote:

> As to force curves, free weights don't provide

> constant force throughout a movement on Earth so I'm curious as to

> why this is so important in microgravity.

[Guest guest]

I'm pretty sure the " constant force " referred to here isn't in reference to

" force curves " but rather it is referring to the fact that stress must be

applied over a long period of time to maintain bone. I would also guess that it

is much more than a spring based Soloflex, finding a device to provide

resistance is not difficult, finding one that will mimic most of the

physiological effects of gravity is.

Randy Dixon

Harlingen, TX USA

Ty Scheske wrote:

> It sounds like the CSU students invented a spring-based Soloflex or

> Bowflex in which the medium itself, rather than gravity, provides

> the resistance. As to force curves, free weights don't provide

> constant force throughout a movement on Earth so I'm curious as to

> why this is so important in microgravity...