Re: squat stance
with sprintes and throwers who move a lot of weight relative to bodywt I strongly advocate comfort and stability rather than arbitary positioning … they experiment and find a groove that suits – few if any end up choosing a sumo position
Lower limb wise we are all strung together in slightly different ways, our limb lengths, muscle insertions, joint angles etc all differ.
Although my evidence is only anecdotal smaller hipped athletes in my opnion have a greater risk of labral hip cartilage tears using a sumo stance … there is too much weight palced on a small area of cartilage at that extreme angle – small hipped individuals typically have less ball insertion into the hip socket and correspondingly less cartilage action
– its also kinda interesting to note that farmers who report a lot of time riding astride (with a wide hip stance) on bikes etc suffer an extremely disproportionate incidence of dual hip arthritis
all trivia I know …. on a more conditioning note I kinda like squats in a more natural position relative to running motion … you ever seen someone run sumo style???