Reverse Band Bench (30-80)
5x135, 5x185, 3x225, 3x275
5x295 @ 8
5x295 @ 8
5x295 @ 9
5x295 @ 9
5x295 @ 9
These were easy. I'm still a little unclear about how much the bands take off, exactly, but the overall weight was about right.
Close-Grip Bench
5x225 @ 8
5x225 @ 8
5x225 @ 9
5x225 @ 9/10
5x225 @ 9/10
Lost the groove on the last two sets, but not a struggle.
Pullups: 4x8 @ 45
Dips: 4x8 @ 70
Dumbbell Preacher Curl: 2x5 @ 40
Sunday, October 3, 2010
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When you reverse band you tie them from above, right? If you want to know how much it helps: lay on the bench and lockout with the bar. Have someone mark the distance from the floor (or bench, or whatever reference point) to your lockout point. Have them also measure from the same reference point to the point where the bar is when it's on your chest.
ReplyDeleteThen allow the bar to just hang from the bands without touching it. Load it up evenly with weight until it rests at the marked lockout point. That's how much weight it takes off at the top. Load it up until it's just hanging exactly at the point marked when it was on your chest. That's how much it takes off at the bottom.
You can assume that the assistance decreases linearly from the chest point to the lockout point.
This is also an interesting way to know how far (in inches, feet, meters, nautical miles, furlongs, light years -- whatever your distance unit of choice) you press the bar.
I personally do it old-school and measure my bar travel distance in cubits.
ReplyDeleteBrian -- You are a genius, MIT is lucky to have you as a student :) What happens if I want to measure the tension of regular bands (from below)?
ReplyDeleteI sense sarcasm, but I like it :)
ReplyDeleteI would use the same procedure to mark the location with respect to a reference point for both bar position on chest and lockout. Then I'd place a scale directly in the center of the bench. Use some blocks to prop the scale up such that the bar resting on the scale is at the correct location for whichever measurement you want (chest or lockout). The scale will record the weight of the bar + the band tension at that point. Collect these measurements for both chest and lockout positions. The tension at each position is the scale reading less the bar weight. The tension varies linearly between chest and lockout.
The choice of what to use as blocks to support the scale (especially in the lockout position...) is up to you.
Soooo.... you can either do all that, or you can hang one of these from the ceiling: http://www.amazon.com/Industrail-Heavy-440-Hanging-Digital/dp/B00186R2UG
OR semi-credit to Jon Lovegren for this:
ReplyDeleteYou can use your results from the hang-test to determine the spring constant of the bands (assuming you use the same bands for reverse and regular).
Spring constant = Force/(stretched distance)
oh, nvm... I think Jon is going to post about this now.
Such dorks we are.
Now, let's say you had different bands for tension from below. You want to know the extra force applied by these bands during some type of bench exercise, for example.
ReplyDeleteYou can do this like Brian's solution for the top-down bands, except with an extra step. We need to experimentally determine the force/distance relationship of the bands.
1) Setup bands from above, as you would in the assisted lockout exercise. A squat rack is ideal.
2) Pull them tight, removing slack, but don't stretch them. This could be done by inserting a bar, letting it hang, and then lifting the bar slightly until slack starts to develop. You are trying to remove tension from the bands.
3) Mark location of bar. This location will be called zero tension point, or ZTP.
4) Add any amount of weight. Anything that stretches the bar substantially far, or at least as far as the bands will be stretched during the exercise. Let's call the amount of weight, including the bar, 'W'.
5) Measure how far the bar has moved since the ZTP mark. Let's call this distance 'D'.
6) Now the spring constant (K) is simply W/D. This can be multiplied by any distance of band stretch to determine the force F = K*strech_distance
7) Setup the bands in the desired lifting configuration, in this case from below.
8) Again, pull them upwards until tight but don't stretch them
9) Mark this location, the ZTP.
10) Get in the bench with a bar, and have someone mark any point you like, i.e lockout or at chest.
11) Measure the difference between this point and the original zero-tension point. Whenever the bar is above the ZTP, of course the bands apply force.
12) Multiply the distance above the ZTP to the point of interest, calling it 'D'.
13) The band force at your point of interest is simply K*D.
Jon
You forgot that there are two bands, so the individual constants of the bands are k1 + k2 = k that Frank found.
ReplyDeleteI was assuming this test was to be done using the exact same band setup (same type, number) as to be used when lifting. If you performed my test on bands separately and then added them during a workout, yes then you'd combine the K's.
ReplyDeleteDude, you guys rock. I will be returning here whenever I have any physics questions.
ReplyDeleteThanks. Hanging the industrial scale from the ceiling looks like the best solution, mainly because this way I can avoid all these calculations.
ReplyDelete