Usually, the claims about being able to pull things (trucks, whatever) and lift/carry large amounts of weight are made of the penis, not of the testicles. My guess is that these are from individuals who have overdeveloped pubococcogeous (sp?) muscles (informally known as the PC muscle group, which darn near ever'body can spell). if the references you have seen have been generic references to the "genitals", they almost certainly mean weight that the guy's dick can haul. If they specifically claim that it is their balls that can pull a tractor-trailer uphill, it's bogus. 100Kg? Hey, sorry, no. I don't believe it.

Hanging a man by the balls was used by some barbaric civilizations (like Texas) as part of the punishment for ****. The weight of a man's body, being suspended by a rope, is enough to break the suckers. Stalin once ordered one of his assistants to be hung be the balls, but added that, if he survived the experience, he was to be drowned in the river, but that if he died, he was to be considered innocent.

Y'gottah love them psychopaths who become the leaders of powerful countries.

As for the pic with the chick with the chain on the guy's nads: ask her how hard she pulled before she managed to rip them off. Problem solved.