In most gyms today, a common instruction during squats, deadlifts, and lunges (as taught by many personal training organizations) is not to allow the knees to travel beyond the toes. Doing so will ultimately cause the destruction of your knees!
I do not agree. There are certain instances where partial range of motion (ROM) is indicated, but for the most part, I teach people the full squat for the following reasons.
FULL SQUAT BENEFITS
1 IT IS THE MOST PRIMITIVE MOVEMENT PATTERN KNOWN TO MAN
Our ancestors used to perform many daily functions (i.e. harvesting, gathering, hunting, cooking, eating, etc.) in a full squat position.
2 IN CASE ANYONE HASN'T NOTICED
We spend 40 weeks in the fetal position (which is basically a full squat) prior to entering this world - do we come out with bad knees?
3 WE SHOULD STRIVE TO TRAIN IN FULL ROM FOR EACH AND EVERY EXERCISE
The squat is no exception.
4 EVERY EXERCISE PRODUCES STRESS
The body then adapts to this stress.
5 CONTRACTION OF THE QUADRICEPS, HAMSTRINGS, AND GASTROCNEMIUS
MAINTAINS INTEGRITY IN THE KNEE JOINT
6 SHEERING AND COMPRESSIVE FORCES DO OCCUR AROUND THE KNEE JOINT
Sheering forces that occur in some open kinetic chain lower body exercises, such as the leg extension); however, the large contact area of the patella with the femoral groove (as knee flexion increases during the full squat) helps to dissipate compressive forces.
7 THE SQUAT IS CONSIDERED A NATURAL MOVEMENT PATTERN WITH HIGH
It is also a safe exercise if performed correctly (and that includes full ROM!)
8 DRAWER TESTS ARE PERFORMED AT AN ANGLE OF 90 DEGREES
So, does it make sense to only go down half way where you are most vulnerable especially when greater loads can be used (because you are much stronger in this partial ROM?)
"PARTIAL SQUATS PERFORMED ON A REGULAR BASIS WILL DECREASE FLEXIBILITY."
9 THE FULCRUM MOVES
According to Ironman contributor, George Turner, the fulcrum moves to the knee joint in a parallel squat as opposed to the muscle belly of the quadriceps in a full squat.
10 IF YOU CONSTANTLY TRAINED IN A LIMITED ROM
The likelihood of injury increases if one day you happen to squat beyond your trained ROM.
11 PARTIAL SQUATS PERFORMED ON A REGULAR BASIS WILLDECREASE FLEXIBILITY
12 THERE IS A LOW INCIDENCE OF LOWER BACK PAIN AND KNEE INJURY IN
ABORIGINAL AND ORIENTAL SOCIETIES
13 OLYMPIC WEIGHTLIFTERS
Even these weightlifters who practice full squats have quite healthy knees compared to other athletes.
14 RESEARCH THAT INDICATES
Although you may find some research that indicates full squats as potentially harmful to the knees, only one study has ever proved this to be true. However, it was performed on a skeleton - the same results do not hold true with surrounding connective tissue.
On the other hand, numerous studies show the benefits of full squats. Unfortunately, many personal training certification courses are teaching half squats as a safe version suitable for all individuals and this has now become written in stone.
God forbid that you deviate from this golden rule to do something that our bodies are meant to do!
Read this carefully: squatting should be performed in a full ROM where the hamstrings make contact with the calves (so that no light can be seen passing through your legs at the bottom position). It is okay for your knees to travel beyond the toes (just do not relax the knees in the bottom position). In other words, keep the legs tight and try to stay as upright as possible throughout the exercise.
So, next time some fitness instructor approaches you in the gym and advises not to go deep while squatting tell him/her that they don't know squat!