Tags : : lifeline
So, as I said, I took my Lifeline chest expander into the
gym today to test the resistance of the cables. I did this by hanging the
expander off the pullup bar (tied with a belt), then attaching weight plates to
the handle and see how far it would stretch.
The cable tested was a yellow - rated at 70 lbs. at double stretch (that is, per side).
So to begin with I took some measurements. To ensure consistency, all lengths were measured between the tips of the middle plug of the expander handles, i.e. the shortest distance between the cables:
At rest (without being previously stretched): 30 cm (11.8"). With about 2 inches from this point to the cable ends on each side, this comes out to more or less the advertised 16".
Finishing position of back press (with scapular spread at the end of the movement): 125 cm (49.2")
Finishing pos. of front press: 122 cm (48.0")
FP of front lateral raise: 119 cm (46.9")
FP of overhead downward pull: 123 cm (48.4")
FP of front chest pull: 122 cm (48.0")
FP of bicep curl: 106 cm (41.7")
So into the gym I went, and decided to start off the experiment with a mere 20 kgs (44 lbs.). Seeing as the Lifeline yellow cable should provide 70 lbs. / 31.8 kgs at a stretch of 60 cm / 23.6", this should not have stretched the cable much at all. I was (unpleasantly) surprised to discover that the weight stretched the cable all the way down until the plate touched the floor, and would have continued stretching it further had the pullup bar been positioned higher. The cable was stretched thin and looked about ready to snap. Stretch at this point = over 130 cm between the reference points.
This pissed me off quite a bit.
I removed the weight and started experimenting with lower resistances.
5 kgs / 11 lbs. slight stretch – did not bother measuring it
10 kgs / 22 lbs. stretched to a whopping 84 cm / 33” (more than double stretch)
15 kgs / 33 lbs. stretched to a huge 127 cm / 50” (further than I stretch the cable in any of the exercises)
Since this was as far as the cable could go with the weight still hanging above ground (without touching it), I decided to call it a day. The findings of this little experiment are very disappointing – the quoted resistance obviously has no grounding in reality, i.e. the yellow cable most certainly does not provide 70 lbs. at double its original length. In fact, a mere 22 lbs. were sufficient to pull it further than double length. This is less than one-third of the claimed resistance.
Perhaps there is a trick of physics that I’m overlooking, but as far as I’m concerned I will not bother with cable poundages anymore – two yellows are “heavier” than one yellow and one red, and that’s it. I will measure progress by colors.
I must say that I wasn’t expecting the cable to perform as
advertised – any measurement of resistance had to be unreliable. But this is
still a huge surprise. The resistance rating seems to be completely random.
Other interesting observations:
The cable seems to stretch in a linear proportion to the weight attached: 15 kgs divided by 10 kgs – weight increase by a factor of 1.500, 127 cm to 84 cm – length increase by a factor of 1.511 (more or less equal).
Measured the cable at rest after stretching – 34 cm / 13.4”, or an increase of 4 cm / 1.6”
Measured the cable at rest after I’d gotten home – 30 cm, like before. Good elasticity.
Last Edited By: BigBruvOfEngIandUK Jun 5 11 3:48 PM. Edited 1 time