I think i may have to disagree with this a bit. When i joined the Marine Corps I could only do 7 pullups. After boot camp, i could do 14. I blame this to fat loss. At the same time, i went in curling 80lbs a couple times. when i got out, i could barely curl 60lbs. So my strength definately went down. I went through a period where i didnt really train much at all and my pullups went down to 10. They are now at 18, a couple inches from 19, and i havent done very many sets of pullups in that time. Just WG pulldowns mostly, and some occasional underhand pulldowns. I'm also now 20 lbs heavier than after bootcamp. But i now incorporate pullups into my workouts, sets of 5 with a 25lb plate extra.