From my experience with wearable tech- you can’t really rely on the Garmin to adequately measure your vertical oscillation in a way that can reveal much about your running technique, especially when trail running. It’s sort of similar to how the Stryd pod only approximates power during running based on an equation.
The main reason to care about vertical oscillation is that it’s one of many metrics that describe an individual’s running economy- along with cadence, stride length, ground reaction forces and overstride/understride (think shin angle right after initial contact and maximum hip flexion angle during mid to late swing).
The absolute vertical oscillation might vary by height, running speed and terrain- but in general, think back to high school physics. Remember the problem where you had to figure out the maximum distance to shoot a cannonball? Too much “y” (vertical) and your cannonball goes really high but not far. Too much “x” (horizontal) and again, your cannonball doesn’t go that far. The perfect mix of horizontal and vertical and your cannonball travels the maximum distance.
It’s not a perfect analogy, but running works in a similar fashion. You need the right mix of the ability to produce both vertical and horizontal power and in a coordinated way in order to run with good running economy- ie run with good performance. This is proceeded by the need to be strong enough to absorb the impact and loading of running.
Too much vertical oscillation- and that’s the runner “bouncing” down the road but not going very far very fast. It’s also associated with the same factors that can cause overstriding- which is- a lack of the ability to produce horizontal forces such that the body’s center of mass travels forward fast enough that it’s over the foot by the time initial contact and weight acceptance occurs.
Too little vertical oscillation- and that’s the runner that “shuffles” down the road, with very little spring to the step and a lot of wasted energy trying to actively swing the limbs forward. Often co-occurs with a higher stride rate, sometimes because the runner read about cadence and tried to increase turnover without having the leg strength, power and coordination to back it up.
Both situations cause poor running economy, or too much energy used for the pace. I’m curious to know how much that affects the AeT and Ant thresholds…..
If you want to know where you fall on this spectrum, getting a good quality videogait analysis can be well worth it! Depending on where you live, there’s some people who are really good at this. 🙂