when is work done in weightlifting?

Question

(in physics terms) Is mechanical work done when the weightlifter lowers the bar to the floor or just when he lifts it?

Answer 1

Whenever the lifter exerts a force over a distance, work is done. When it is lifted, he has performed a positive amount of force over a postitive distance, so the work is positive. When he lowers it, he is exerting a positive amount of force over a negative distance, which means he is performing negative work on the weights... however, the weight is exerting a negative amount of work over a negative distance on the lifter's muscles, so technically positive work is being done on the lifter.

Answer 2

I'm not qualified to answer this in physics terms.

But I do know this: When lifting, most coaches tell you to do a "5-count." Meaning, 3 seconds moving down, 1 second hold at the bottom, and a blasting 1 second upwards to the start of the movement.

So, judging from that, I would say the most mechanical work is done on the lowering part.

Answer 3

While the man is holding the weight above ground level whether lifting or lowering, work is being done as his muscles in all cases are being used. So both lifting and lowering is a form of mechanical work.

(If he drops it on his foot, then the barbell is doing some (very painful) work.

Answer 4

Technically, both. Most of the work is done lifting the bar against gravity. Although no work has to be done for the bar to return to the ground (as the potential energy contained in the bar when its lifted above the ground will do this all on its own), work is still done in reducing the velocity at which the bar is lowered, assuming he doesn't just drop it. Much like the moon lander had to perform work (through booster rockets) to slow its decent to the moon surface so they didn't just crash

Answer 5

What you are doing is Potential Energy = mgh
The higher you rise something, the more potential you will have. So work is done by lifting the bar.

Answer 6

The work is done when the distance between the ground and the height of the weights increase. All other movement is not work.

Answer 7

he's obviously doing work when lifting

unless he simply drops the bar to the ground he is doing work when lowering the bar (that's why you lower the dumbbell slowly when doing a bicep curl- so your muscles get more work)

Answer 8

Only when he lifts it. When he lowers it, it's gravity that does work on the barbell. Thw weight lifter converts that work into chemical energy (acting like a frictional force)

Doug

Answer 9

when he lifts it.