"Air" Barbell Pull-Ups! I shit you not.
A hard charging trainee in another other land convincingly held my bewildered ear about the benefits of dynamic isometric tensioning exercises for strength and calisthenics prowess. He was demonstrating the "Air" Pull-Up with an unloaded barbell to a very captive audience on introduction day.
Sadly, he was his unit's PTI; big, well built, legs like tree trunks, well-toned and cut... but it ended there. Needless to say the next day he completely failed the CRFT we gave with a whooping 14 Dead Hang Pull-Ups and we had "given" him two or three of those out of mercy. Back to the drawing board there buddy. His strength, power, stamina, and endurance were nil on the scale.
For the remainder of the course he was ordered to demonstrate a different exercise everyday at morning muster... he was an excellent motivation tool to say the least!
An aside... he was a genetic freak and had to do very little to look the way he did. Believe me after seven months we had transformed him into a machine and he became one of the best amphib operators I ever had trained.
The man was a mule, could hump forever, and would happily carry half his fire team's gear without complaint and was one of the few men I have seen carry a hidden mortar base plate like an extra pairs of socks!