This is a question I am asked a lot in weightlifting. It is a great question and as with everything in life, the answer is not as simple as we all would like it to be. Let me start off by stating that there are basics in weightlifting and there are nuances in weightlifting. Beginners to the sport should be introduced to the basics and learn them. When I say learn I mean repeat the basics of weightlifting over and over for at least couple of years. From then on, nuances can and should be explored to facilitate performance.
Weightlifting has two types of stances: the deadlift (start) position and the squat (finish) position. In both of these positions foot position is crucial for a successful lift. Variations in foot position distinguish lifters and are based on body type, technical skills and perception of the body in space, such as hand placement, potion of hips and knees, etc.
Foot position should always be taken into account, seriously. In both start and finish positions, the ankles are responsible for stabilization and transfer of forces from the floor up (the most stressed joints in the body while lifting). The plantar flexors (mainly Gastrocnemius and Soleus) and the main supinator (tibialis posterior) perform powerful actions, while the small muscles of the feet and toes are responsible for the stability of the ankles. That said, an ankle that is not able to stabilize the whole body and weight and transfer forces, may lead to a bad lift and injuries.
On top of this, another reason that foot position should be seriously taken into account is the mid-foot arch.This arch is responsible not only for foot stability and correct loading, but also for free bloodflow to the toes (so you will be able to use them as you push yourself off the floor). This arch is maintained mostly by the tibialis posterior muscle, which is a supinator.
Having said that, lets talk about the start stance. The basics, feet shoulder width apart, feet turned slightly out (0-7 degrees). This is also usually the toe out physiological position while walking, which mostly depends on hip position and knee position. As you raise up from the floor to get the bar above the waist, the feet move into supination (meaning that most of the weight is distributed on the outside of the foot) and that it is mostly the action of that same muscle that is responsible for maintaining a nice looking arch in your foot. This can happen only if your toes are turned out. Therefore good stability and powerful movement will be move efficient with the toes out start position.
Next, the finish (squat) position. Here the basics are very simple: get your feet to turn out. Slightly more than your starting position is normal. If the lifter is able to get the weight lifted into the “weightlessness” phase, the feet will change their position naturally. Sideways and backwards displacements are common here.
The important thing to remember here is to land comfortably enough with the feet so the pelvis won’t drop down to the floor.
Biochemically speaking you won’t be able to squat low in a stable position without turning your feet out. Mostly because the hips are directed outwards (externally rotated) and also because the hip, knee and ankle joint will be loaded through the whole surface rather than only on one side of the surface (yet another reason that there are a lot of hip labral tears, meniscus tears and ankle joint problems by weightlifters who do not perform the lifts correctly).
In summary, foot position in weightlifting can dictate whether the lift is going to be successful and healthy to the joints. Basics should be learned before trying to jump ahead and correct foot position in both the start and the finish positions. Nuances in weightlifting are endless, but basics are the essence of this beautiful sport and the most important starting block for weightlifters new to this sport.