Are Cable Pulley Machines Making You Weak (UH-OH)
video description
I-m a mechanical engineer who uses cables and pulleys for rigging and rescue professionally.
Date: 2022-04-22
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Comments and reviews: 9
Wayne
I'm really late to the party here, but Jeff is way off on his comments about how pulleys work. They basically re-direct the tension to the load, and he got that right. He went off-track when he started talking about the # of pulleys. The # is not relevant, the DESIGN is. They could be using 10 pulleys in order to get the cable to the stack, but not have a force-multiplying design included. In that case the added friction will actually INCREASE the apparent weight of the stack.
What IS relevant is the distance that the weight is moved as a ratio of how far you've moved the cable. If you move the cable 4' and the stack only moves 2' you're only moving 1/2 the weight. On the machines that I've seen there is re-direction and there is either a 1: 1 ratio or a 2: 1 ratio, so it's very easy to determine what fraction of the weight you are actually supporting. Just move the grip and see if the stack moves the same distance, or only 1/2 the distance. It's NOT rocket science.
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I'm really late to the party here, but Jeff is way off on his comments about how pulleys work. They basically re-direct the tension to the load, and he got that right. He went off-track when he started talking about the # of pulleys. The # is not relevant, the DESIGN is. They could be using 10 pulleys in order to get the cable to the stack, but not have a force-multiplying design included. In that case the added friction will actually INCREASE the apparent weight of the stack.
What IS relevant is the distance that the weight is moved as a ratio of how far you've moved the cable. If you move the cable 4' and the stack only moves 2' you're only moving 1/2 the weight. On the machines that I've seen there is re-direction and there is either a 1: 1 ratio or a 2: 1 ratio, so it's very easy to determine what fraction of the weight you are actually supporting. Just move the grip and see if the stack moves the same distance, or only 1/2 the distance. It's NOT rocket science.
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Tammi
If the weight is moving the same distance from the rest position that you are moving then the work is the same. Rather than whipping out my old statics engineering textbook to figure out the half dozen pulleys on my bodycraft express pro I just measured the distance the cable moved compared to the distance my arms were moving on a bench press. They were the same, so the work is the same so the weight is the same. I confirmed this with a pull scale used for deer hunting, which was much easier method. Most of the cheap machines are all over the place i bet. The bench press machines that act like levers are the most misleading. my father in laws machine is much lighter than the weight plates because your hands are out 10 more inches than the weights. Its weird to load up 200# of free weights on it and you get 150# at the handles.
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If the weight is moving the same distance from the rest position that you are moving then the work is the same. Rather than whipping out my old statics engineering textbook to figure out the half dozen pulleys on my bodycraft express pro I just measured the distance the cable moved compared to the distance my arms were moving on a bench press. They were the same, so the work is the same so the weight is the same. I confirmed this with a pull scale used for deer hunting, which was much easier method. Most of the cheap machines are all over the place i bet. The bench press machines that act like levers are the most misleading. my father in laws machine is much lighter than the weight plates because your hands are out 10 more inches than the weights. Its weird to load up 200# of free weights on it and you get 150# at the handles.
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Alex1911
Just gotto look at the cable pull machine. Lots have the weight rating at the handle on the stack. Some dual cable ones once attached to a single bar will actually be double the weight at the bar vs the stack. So it all really depends on the machine. You should be able know if the weight seems to light or heavy anyways regardless of the reading. Coming to a new cable pull machine I will always try and load it as heavy as possible then work down to find my ideal starting point to do reps, then start working up from there over the weeks. I love cable pull machines for curls and triceps, nothing beats that constant load from top to bottom. Being able to have one cable set high for triceps, and one low for curls is also killer to just keep switching back and forth till you're dying -
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Just gotto look at the cable pull machine. Lots have the weight rating at the handle on the stack. Some dual cable ones once attached to a single bar will actually be double the weight at the bar vs the stack. So it all really depends on the machine. You should be able know if the weight seems to light or heavy anyways regardless of the reading. Coming to a new cable pull machine I will always try and load it as heavy as possible then work down to find my ideal starting point to do reps, then start working up from there over the weeks. I love cable pull machines for curls and triceps, nothing beats that constant load from top to bottom. Being able to have one cable set high for triceps, and one low for curls is also killer to just keep switching back and forth till you're dying -
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victor
Yes he's correct with regards to pulleys. With that said machines don't make you week you just have to add more weight. I use machines to stay in shape and I'm not necessarily looking to get bigger with that said the more I do the stronger I get the more toned and bigger my arms get. It all depends on your goal. Machines are also great to do rehab because they isolate to one muscle group. I used them to rehab my shoulder and it worked. If I would have used free weights the chances of injuring myself would have been greater. You young guys can still work out however you want but as you get older injuries from working out are more likely and you'll have to modify the way you work out. Some parts of the body just don't work like they use to.
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Yes he's correct with regards to pulleys. With that said machines don't make you week you just have to add more weight. I use machines to stay in shape and I'm not necessarily looking to get bigger with that said the more I do the stronger I get the more toned and bigger my arms get. It all depends on your goal. Machines are also great to do rehab because they isolate to one muscle group. I used them to rehab my shoulder and it worked. If I would have used free weights the chances of injuring myself would have been greater. You young guys can still work out however you want but as you get older injuries from working out are more likely and you'll have to modify the way you work out. Some parts of the body just don't work like they use to.
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hug8956
Jeff I love the videos but as a mechanical engineer your statement about number of pulleys is not the most accurate. Lifting when pulleys are involved is all about tension in the cable. There are basically two types of pulleys, direction change and weight change. Often when there is a pulley on the top of the weight stack it is a weight change pulley. One end of the cable goes to a fixed point and the other end comes to the person lifting the weight (maybe even through some direction change pulleys. One cable will wrap roughly half way around the weight change pulley on top of the weight and come out of each side of the pulley. If the weight is 50 pounds the lifter only has to apply 25 pounds of tension to the cable.
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Jeff I love the videos but as a mechanical engineer your statement about number of pulleys is not the most accurate. Lifting when pulleys are involved is all about tension in the cable. There are basically two types of pulleys, direction change and weight change. Often when there is a pulley on the top of the weight stack it is a weight change pulley. One end of the cable goes to a fixed point and the other end comes to the person lifting the weight (maybe even through some direction change pulleys. One cable will wrap roughly half way around the weight change pulley on top of the weight and come out of each side of the pulley. If the weight is 50 pounds the lifter only has to apply 25 pounds of tension to the cable.
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john
45 with dadbod here, I am looking to get back into shape and i have never worked out, not one day. I have had hard jobs like roofing and spent 10 years walking 60lb dead weight bundles up ladders, about 60 to 120 times a day. but i stopped that about 12 years ago and my body is f-up. I was wondering about cable pulley machines as i live alone and dont have anyone to spot me, i am getting fat in my medium age about 25lbs over at 215. if you didnt know about fitness and wanted to lose weight and build some muscle, where would you start? did keto- it worked and my hair fell out so thats no9t on my list. any advice
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45 with dadbod here, I am looking to get back into shape and i have never worked out, not one day. I have had hard jobs like roofing and spent 10 years walking 60lb dead weight bundles up ladders, about 60 to 120 times a day. but i stopped that about 12 years ago and my body is f-up. I was wondering about cable pulley machines as i live alone and dont have anyone to spot me, i am getting fat in my medium age about 25lbs over at 215. if you didnt know about fitness and wanted to lose weight and build some muscle, where would you start? did keto- it worked and my hair fell out so thats no9t on my list. any advice
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Gerry
It would be more accurate to make sure people observe how far the handle moves (where you're applying force) versus how far the weight stack moves.
If the handle and weight stack move the same distance, then you are basically applying the same force as the weight stack. If the handle moves further, then the pullies are giving you a mechanical advantage. If the handle moves twice as far as the stack, the force used to move the stack is half the weight of the stack.
I'm really late to this anyway. Cya
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It would be more accurate to make sure people observe how far the handle moves (where you're applying force) versus how far the weight stack moves.
If the handle and weight stack move the same distance, then you are basically applying the same force as the weight stack. If the handle moves further, then the pullies are giving you a mechanical advantage. If the handle moves twice as far as the stack, the force used to move the stack is half the weight of the stack.
I'm really late to this anyway. Cya
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mackenziec
Bit misleading (engineer here. Compound pulleys are what you need to look for. If you have 100 pulleys you could still be pushing the advertised weight (ignoring friction. If there is a pulley MOVING then don't trust the weight. If the weight goes up by a pulley on the weights, then you need to move 2 inches for every inch the weight goes up (an inch on both sides) thus there is mechanical advantage. Maybe just clarify in your next video.
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Bit misleading (engineer here. Compound pulleys are what you need to look for. If you have 100 pulleys you could still be pushing the advertised weight (ignoring friction. If there is a pulley MOVING then don't trust the weight. If the weight goes up by a pulley on the weights, then you need to move 2 inches for every inch the weight goes up (an inch on both sides) thus there is mechanical advantage. Maybe just clarify in your next video.
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deputy
It's like relying on a taster to serve you food! Cmon guys go to a gym and try the same exercise with free weights a machine and pullys! See what what works for you! Move up the weight stack if you must but trial and error is the only way forward! When ever I read or hear something regarding an exercise I try it out in the gym and see if it works for me. If it does so much the better if not it must be working for someone else!
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It's like relying on a taster to serve you food! Cmon guys go to a gym and try the same exercise with free weights a machine and pullys! See what what works for you! Move up the weight stack if you must but trial and error is the only way forward! When ever I read or hear something regarding an exercise I try it out in the gym and see if it works for me. If it does so much the better if not it must be working for someone else!
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