Put a couple power taps on that bar between the weight lifter's hands and the bar, and compare it to the force measured at the hub while a sprinter is putting out 1000 watts, and then compare the two forces? Is that how you would do it? OK, I can buy that.
I guess it all comes down to how you define the word "equivalent".
The comparison above seems a bit over simplified, but I'm not smart enough to argue against it, so I will concede for the moment. Something keeps nagging at me that it's not quite than simple, but I can't quite articulate it.