Well I've been squatting 100kgs on the barbell, but there's no way I'll be able to lift two 50kg dumbells.
Also, a mate of mine who is a personal trainer had a look at my form and said I wasn't leaning back enough. Basically my knees were over my toes too much. He suggested I drop 40kgs off my barbell squat and focus on form, and just smash out more reps. I think that's probably a good idea because i don't want to injure myself.
I always feel really unstable if I lean back when squatting (ie. shins perpendicular to floor), like I'm going to topple backwards.
Doesn't it have the same effect? Less weight but more reps?
We looked at rep ranges earlier. If 100Kg is your 1 RM, dropping 40Kg would put you at 60% which is at the lowest effective weight range. If you're doing reps with 100Kg, you probably don't want to go that low. It's really just a warm up weight following by a ridiculous amount of reps to get to failure. I would suggest that if he's giving that kind of advice on one hand, he probably doesn't know what good form on squats is anyway. Vary your load in the 60-90% range without spending too much time at either end.
The 50 Kg DBs feel heavier than the barbell since you use a differnet musculature to support the weight. Try doing progressively heavy farmer's walks. You'll hit 50 Kg in no time. The other aspect is that you lift from a dead stop from the floor, similar to a deadlift, only deeper. That's harder than back squating since you don't get the stretch reflex to help you out of the hole.