Concept2 Forum

Ok . . . this is for all you physics majors and just plain smart people . . .

Suppose I row 30 min at 100 watts and 20 SPM.

Wikipedia defines a watt this way: one watt is the rate at which work is done when an object's velocity is held constant at one meter per second against constant opposing force of one newton.

It defines a newton like this: it is equal to the amount of net force required to accelerate a mass of one kilogram at a rate of one meter per second per second.

Allow me to make a fool out of myself . . . I'm an international relations major, not physics . . .


My flywheel is at rest . . . I pull hard (the equivalent of 100 watts).

The pull is roughly a meter long and it takes roughly a second. Have I now pulled approximately 100 x 1 Kg (2.2 lbs) . . . or 220 lbs?

Am I doing this 20 times a minute . . . 4400 lbs/min. ?

For 30 min . . . 132,000 lbs. ?

So you'd have to bench press 175 lbs a total of 754 times ? 200 lbs 660 times?


Obviously not. Obviously, I don't understand. Any help greatly appreciated.

Thank you

Well to start... 100 watts is pretty pathetic. But that's why you cannot compare lifting to a form of aerobic exercise. Your heart is far more powerful than any single muscle group when it comes to long-term power output. That's why you can't increase something like VO2 max from lifting weights.

So yes, it would equal something outrageous like a few hundred reps at a high weight.

bloomp wrote:Well to start... 100 watts is pretty pathetic. But that's why you cannot compare lifting to a form of aerobic exercise. Your heart is far more powerful than any single muscle group when it comes to long-term power output. That's why you can't increase something like VO2 max from lifting weights. So yes, it would equal something outrageous like a few hundred reps at a high weight.

Pretty pathetic? LOL I didn't realize we were competing.

I wasn't sure why you bothered to answer until I saw your comment that "everyone must fail." I get it now.

Your arrogance and lack of manners are matched by your ignorance. VO2max can be increased by almost any activity that pushes you close to and/or over the 100% mark . . . (Tabata, in his experiments, had athletes working at 170% and 200% VO2max) . . . AND you keep rest periods short enough so that the heart is unable to fully recover.

But VO2max wasn't my question was it?

A few things here. I was simply pointing out that a 100 watt average over 30 minutes is rather low. I had assumed you were using it as a simple example. If you took offense, I'm sorry.

No competition, just trying to point out that the reason you can have a higher wattage from an endurance activity is the fact that your heart is able to do more work over time. That means you have to do an equally large amount of work with one muscle group instead of using all your muscles with a continuous supply of ATP from aerobic contractions.

Please note I did NOT bring up intervals. Yes, intervals are a wonderful way to get your VO2 max up very quickly. Intervals are not what you asked about. Intervals are still somewhat aerobic in the way that they use multiple muscle groups and keep the HR high for several minutes with limited rest. I know how Tabata's work.

LOL . . . well, I'm 55, fat and out of shape and 100 watts is where I am right now. I've been better and will be again.

I do hope to eventually match your rowing prowess.

Intervals and VO2max . . . while interesting . . . are not what I am asking about.

My question is strictly for those who understand the physics of the thing . . . which I do not.

How does one determine the equivalent of 30 minutes, @100 watts @ 20 SPM in resistance exercise?

Thank you

JJW wrote:tly for those who understand the physics of the thing . . . which I do not.

How does one determine the equivalent of 30 minutes, @100 watts @ 20 SPM in resistance exercise?

Thank you

The easy answer would be that there simply isn't a way.

But if you had to it definitely wouldn't be bench pressing. I'd recommend either high pulls or cleans, as they are similar to the rowing stroke as they start out with the legs, then the back and then the arms. Squats are another option, as they hit the lower body pretty hard, but they ignore the upper body aspect of rowing.

JJW wrote: How does one determine the equivalent of 30 minutes, @100 watts @ 20 SPM in resistance exercise?

If you want to become a physics major then try this: http://www.atm.ox.ac.uk/rowing/physics/ergometer.html

JJW wrote:Ok . . . this is for all you physics majors and just plain smart people . . .
Suppose I row 30 min at 100 watts and 20 SPM.

Wikipedia defines a watt this way: one watt is the rate at which work is done when an object's velocity is held constant at one meter per second against constant opposing force of one newton.

It defines a newton like this: it is equal to the amount of net force required to accelerate a mass of one kilogram at a rate of one meter per second per second.

Allow me to make a fool out of myself . . . I'm an international relations major, not physics . . .


My flywheel is at rest . . . I pull hard (the equivalent of 100 watts).

The pull is roughly a meter long and it takes roughly a second. Have I now pulled approximately 100 x 1 Kg (2.2 lbs) . . . or 220 lbs?

Am I doing this 20 times a minute . . . 4400 lbs/min. ?

For 30 min . . . 132,000 lbs. ?

So you'd have to bench press 175 lbs a total of 754 times ? 200 lbs 660 times?


Obviously not. Obviously, I don't understand. Any help greatly appreciated.

Thank you

This is simply right And as other have said, the rowing you do with you legs, back and arms, the benchpress with your arms and frontshoulders only, so a lot less muscle. That makes it hard for those muscle, but aerobicly not that hard.

The push-up would be a better comparison than the bench press.

ThatMoos3Guy wrote: The easy answer would be that there simply isn't a way.

I don't believe that's true. I was hoping to find a way to do it mathematically . . . but it can also be done practically.

For example . . . you can certainly determine how mnay calories you burn rowing and how many you burn bench pressing, curling or any other exercise. They sell heartrate monitors that calculate it for you.

I'm sure there's also a way to determine how many watts you use doing squats, push-ups or whatever.

As long as you have various measures of power and effort then I think it would be possible to compare.

One simple way I came up with is to use Perceived Effort . . . which has been shown to be pretty accurate.

For example, I find it a challenge to row 20 SPM at 100 watts. OK . . . so that makes that my "20 RM." So what weight can I pull 20 times in one minute at a like degree of exertion on a Nautilus or Iso-Lateral Sitting Row machine? What weight can I do 20 times in one minute at a like level of exertion on a Bench Press.

Etc.

Anyway, thanks to all for your responses.

To express a bench press in watts isn't really meaningful. It doesn't depend on the number of repetitions but only on the speed of a single repetition. You could increase the power by making faster repetitions but the used energy per repetitions doesn't increase at the same rate because the power is delivered for a shorter period of time. You are probably looking for the total amount of burned energy.

Let's first consider the (meaningless) Watts case since that's what you asked for. Imaging you push a 70kg weight in 3 seconds and you have to overcome a distance 0.75 meters. Neglecting terms of kinetic energy and elastic energy (= meaning delivered energy over the entire cycle equals energy needed to overcome the gravitational potential and nothing more or less.). The power equals = gravitational constant * mass * distance / time. In this hypothetical case 175 Watts. This is probably a lower estimate. Some of the gravitational energy might be reused for the next repetition but there are also opposite effects which are expected to be higher: the movement also requires input of energy to increase the kinetic energy (increase speed not only move over a distance), the eccentric phase probably also burns energy even though it doesn't require energy (the amount of work done in this phase is negative).

The number of watts is not a meaningful number (from a certain perspective it can be seen as zero. e.g. imagine the repetitive lifting of a weight by a perfect spring, it goes on for ever without an external input of energy) and so is the perceived effort as well. If forces become high then effort may be very high as well even though the required energy or power can be low. Perceived effort (or a certain heart rate) should not be put equal to burnt calories. It is a meaningful measure only if you compare the same type of effort. For instance when comparing different days of training and making an estimate of progress.

The best thing to do is to take a sample of the muscle after exercise and compare those for different types of exercise. An example of it's use can be viewed here: http://www.thinkmuscle.com/articles/mcd ... c-diet.htm (also interesting if you like ultra marathons)

BTW. the bench press equivalent of rowing is a bench pull.