is lack of any kind of pain or discomfort (or even soreness) in the lower back a good indicator that it did not round during the squat?
Not really. Rounding your back during squats (and other lifts) increases the shear forces on the spine. These forces increase the odds of an injury (muscle strain, disc rupture), but these odds are nowhere near 100%. Many people have completed many lifts with rounded backs without injury, but I wouldn't use that as an endorsement to consistently train that way. Sooner or later, the odds
will catch up and you'll be writhing in pain. Moreover, even if you avoid acute injuries, lifting with a rounded back may contribute to chronic pain later in life.
I can't still fully sense my lower back especially at the very bottom.
Then record your lifts or have someone (knowledgable) watch you as you squat until you develop the proprioception to keep your back safe. It may help to do exercises such as supermans and the cat stretch so you know what your back feels like when it is in extension or rounded. Also, while you don't want to use a mirror with heavy weight on your back, you can turn your head and watch your back in a mirror while doing air squats to help improve your proprioception. You should be able to maintain a rigid, neutral back the whole way down.
Also, is usage of a belt advised?
This is a slightly complicated issue.
The good:
* The
primary role of a weight lifting belt is to allow you to lift more weight by increasing intra-abdominal pressure. This can be useful when going for a PR, especially if you are competing in any sort of weight lifting.
* Belts can be very effective teaching aids for learning the valsalva maneuver. The tactile feedback of having your abs push against something - and the extra rigidity you develop in the torso as a result - is a great way to quickly see how & why you should use the VM.
The bad:
* Belt do NOT increase safety: crappy technique can lead to an injury whether or not you are wearing a belt.
* Using the belt too much, in my experience, leads to total dependence on it. People that do all their lifts with the belt sometimes are unable to lift much without it and are more prone to injuries when they try. This might be because using the belt too much prevents some core muscles from developing (compared to training w/o a belt) or just a mental issue where they are not confident or can't maintain proper form without the feel of a belt.
IMO, most beginners and intermediates should reserve belt usage for the occasional PR attempt and nothing else. Advanced lifters can decide for themselves.
And regarding shoes, I'm wearing chuck taylor's now. Isn't that good enuf?
Stronglifts has a good article about
shoes for weightlifting.