In a a clinical setting, there are a couple of key reasons why you would want to change a runner’s mechanics:
They are experiencing pain
They are coming back from an overuse injury, and they don’t want it to happen again
Now the million dollar question is how do you change their running mechanics? The short answer: you need to change their running mechanics.
This important paper by Willy and Davis et al. demonstrates that running mechanics will NOT necessarily change when you improve hip strength and single leg squat with an intensive hip strength program.
One of my key takeaways is that running is a complex motor skill that cannot be reduced to correlate tests such as single leg squatting and glute med MMT. You need to directly change their running mechanics through cueing and motor skill training while they run. If a runner has excessive hip adduction, cue them visually or verbally to run with less hip adduction. If a runner is overstriding, cue them to run with 5% shorter strides, or have them run with a metronome at a faster cadence.
Often we are over-reliant on what we see on the table with an impairment-based exam (eg. active ROM, passive ROM, MMTs, soft tissue palpation, joint mobility testing) and as a result, we miss the bigger picture in terms of changing the actual complex movement. In other words, we need to avoid over-reducing a movement into its component parts.
So, the big message here: to change running mechanics, you need to change running mechanics.