Can you push down more than your weight?

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It is not possible to press down more than your body weight without some form of restraint, such as being strapped in. While one can exert a force greater than their weight by jumping or using mechanical advantages like pulleys, in a seated tricep machine without restraints, the maximum force exerted is limited to one's body weight. The configuration of the machine, including the pulley system, can reduce the force required to lift weights, making it misleading regarding the actual weight being pressed. Users reported being able to select weights greater than their body weight, but this does not equate to pressing that weight down without additional support. Ultimately, pressing down more than your weight requires some form of mechanical assistance or restraint to achieve.
  • #31
Hey now...
 
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  • #32
Doc Al said:
Hey now...
I never said you didn't go to the gym, I'm just giggling at the thought of you stood there explaining what your doing to the other people in the gym.

"Now assuming that both the strings and pulleys are massless ...":smile:
 
  • #33
Field report from the gym

OK, so I did check out several machines at the gym at work. The gym is small, with only two machines that could function as a triceps pressdown machine (they do not have a machine dedicated to that function). Both were Cybex machines: A cable cross-over machine and a lat pulldown machines. So this is hardly representative of all machines.

Nonetheless, for the record, both machines use a simple pulley arrangement: no mechanical advantage. Both machines use a pin to select the number of plates you lift.

The plates on the crossover machine are just labeled by numbers in sequence, not anything that is obviously the weight. The numbers do not corresponding to 10 lb increments (as one might at first think); I checked by hanging an Ivanko 25-lb plate from the cable--it could easily raise the stack at position #4.

The lat pulldown machine looked obviously labeled in pounds: 12.5, 25, 37.5, etc. I hung that 25-lb plate from the cable--it was not enough to balance weight of the 25 lb stack. Only when I hung 27.5 lbs from the machine did it balance. So, at least for this particular setting, you'd have to exert more than 25 lbs of force to lift the 25 lb stack. (Which is quite reasonable.)
 
  • #34
Simple experiement. Try lifting your body so that all your weight is on the bar, maybe try standing on it if you can balance yourself with a nearby object. Compare your weight to the weights on the scale.

If the back of the seat is tilted forwards, you could exert upwards force on the back of the seat. You could also jerk your body downwards, but would be quickly repelled back upwards.
 

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