Maybe a better place to start would be what we can’t tell.
One study sent one-minute video clips of five different runners to 121 coaches ranging from high school to international level and asked them to rank the runners from most economical to least economical. They then compared those rankings to lab-measured values of running efficiency.
The rough range of running efficiency between the runners was around 40ml/kg to 50ml/kg of bodyweight all running at the same pace. The results found the coaches couldn’t rank any of the runners in order with only 6%managing to get 3 of the 5 runners in the right order. Another 12% got two in order.
When it came down to experience of the coaches the researchers collected information comparing the highest education level, certifications and running experience. None of it mattered. There was no correlation between any of these factors and the coaches ability to tell which runner was the most efficient.
So if we can’t measure performance of running technique can we predict injury? The research isn’t great. One paper investigating cadence in college level runners found those running under 160/min were at a heightened risk of stress fracture. Beyond that there’s not much evidence that health professionals can predict an injury just by looking at you on a treadmill.
Why do we still do it?
If you’re a runner coming in with an injury there’s a range of ways you might be able to offload the painful area with running cues. For most runners a treadmill analysis isn’t going to be the main part of their treatment but it could be a useful way to get your back whilst you rehab the injured area.
So while we can’t help you running faster or prevent an injury just by looking at your running we might be able to help you get back on track from an injury faster and for many that could make a gait analysis well worth it.