I used to include the hack squat but found it difficult to keep balance without raising my heels slightly on a block. I knew however that that wasn't good for my knee's and therefore discontinued this otherwise productive exercise. Cheers Zen ps., i thought for a moment that your boy was going to demonstrate the lift! :)
Nope. No injury. I thought my son was going to mess with the camera. I didn't want to pull the rest of the reps if the camera wasn't rolling. Oddly enough when I later did pull the 50 reps in 10 minutes, I wasn't making a video.
Age has nothing to do with it - I know a few guys down at the gym who are pumping heavy iron and they're in there '70s! This is good deadlifting and good deadlifting technique. Don't agree with the high reps but KEEP UP THE GOOD WORK!
The thing to remember with going for reps in a certain time is to pace yourself. If it is your 6RM, then pull mostly singles or doubles. The more you fatigue, the longer you have to rest between sets to stay steady state.
My orthopedist has no problem with deadlifts. 315# is less than 2/3 of my max. With that sort of load it's usually OK to do a lot of volume. I've done 50 and 60 rep workouts at 315 in the past without problems. I work hard on core and posterior chain, specifically so my back will be strong.
I wonder how many people actually try those? I keep telling people those are tough, maybe this will give them a point of reference. Plus these beat the floor up a lot more than those.