there is an extremely good article by eric cressey worth reading … in fact it is the embedded clips that are worth watching
I think Ash made two extremely (sorry make thats three) salient points
1) many athletes try to squat to narrow – have a look at the power position you use in action – your feet are generally slightly out from the line of the hip
2) dont use a weight you cant really handle – it takes time to build up true squat strength and form – with our younger athletes if they cant perform a one leg squat to just below parallel – they are not strong enough to be loaded up
– we use one leg and light front squats to ensure our athletes understand the concept of squatting correceltyy and we prefer them to break parallel – not necessarily ATG – but definitely an inch below parallel … with existing injuries that of course may need some examination.
3) individualise for the existing flexibility, body shape, strength and limb to back length etc of your athlete – that may mean front squats are preferable to back squat, and ensure any box squats are to the correct height for that athlete etc
remember these are all dynamic they change over time and you need to observe when to respond to such change
Some of these limitations however do not reflecy a lack of flexibility or mobility – some reflect the inherent structure of the athlete – we all perform better in slightly different body positions as we are all anatomically hung together is slightly different ways ( a classic example is the hip joint – some of us have beautiful deep set acetabulums lined with exquisitely thick cartilage our joints last our lifetime – others have far less coverage .. they are on the hip replacement list) … your big challenge as a conditioner is to recognise what works best for the individual and what is a true weakness needing addressing in that individual.
best wishes – feed off people like ashley as much as you can – their stored knowledge is the most precious asset in our community – and use your own brain to its limits … the brain is a muscle that can move the world !