Midway through winter, you have probably plowed through a few treadmill workouts. Treadmill workouts don’t change your running form significantly (enough to do a running analysis on a treadmill and assess the results), but they do change the forces your body uses to move you along. So how do you know if you are training safely and properly with hill training on the treadmill?
The study referenced below analyzed the running of both amateur and elite athletes. As all runners speed increased, they all took longer steps, more steps (increased cadence), and were in the air longer and had their feet on the ground less time.
As they ran up inclines (hills), they took smaller steps, more steps (increased cadence) and were in the air less. The elite runners feet stayed on the ground less than the amateur runners.
If you are doing cadence training, your cadence will likely change when you change surfaces or run faster. So optimal cadence will depend on whether you are going up hill, down hill or running on a flat surface or running faster or slower.
Elite runners were able to get their feet off the ground quicker on hills. This might be due to them having an edge on strength, so strength training or maintaining running strength appears to be important. Also, if a recreational runner is returning from an injury related mainly to weight bearing (ie. stress fracture), caution should be used in implementing hill training, as it may have the chance to put greater stress on the tissues than flat surfaces due to the runner keeping feet on the ground longer.