"Go Heavy or Go Home" — I love this old lifter's quote because it's inspirational, motivational, and just sounds bad to the bone. It's like "Dude, if you're just gonna clown around with wussy weights you might as well go home!" That said, how much truth does it hold and what's the application? Well here's a quick stab at it without getting too technical and trying to remember all those big words I learned in grad school:
There's definitely credibility to the positive benefits of lifting heavy. Lifting heavy will stress the nervous system and muscle fibers differently than lifting with lighter weights. If the stress doesn't injure you it will cause the body to adapt by becoming stronger both neurologically and physiologically — actual changes within the muscle. Lifting heavy is generally affiliated with increased strength. In other words, if you want to focus on gaining strength versus muscle hypertrophy (muscle size) you'd want to implement periods of heavy lifting into your workout regimen.
In general, I think of lifting heavy as using weight loads which tax the body in six or fewer reps. Personally, I rarely train in this rep range which I guess would send me home if I took the saying literally! The reality is that even those advanced male and female lifters who hang this quote over their bed, use it sparingly and strategically. As with many things in life, some is good, lots can be bad. So I guess the saying should be: go lift something heavy, be smart about it, foam roll it out, and then go home. But... that doesn't sound quite as cool does it!