An Endurance Nation athlete asked if running hard in hills could substitute for doing intervals at a fast pace.
My reply:
I live in the midst of hills, so I’ve gotten quite used to running and training in them. Here’s my take on your question, which as I understand it is, “Is getting my HR up while ascending, and my speed up while descending giving me the same training benefit as doing fast intervals on the flats?” I’d say that depends on what your training goals are. If you are aiming for an IM run, then just slogging out those miles as you describe will probably give you what you need. But if your goal is to train as much speed into yourself as possible for 5K, 10K, and even 21K runs, including at the end of a triathlon, then doing intervals on a track is the gold standard.
My thinking is, there is more to fitness than simply getting your HR up (cardiovascular adaptation). There are neuro-muscular and bio-mechanical adaptations as well. Going up hill, strides are much shorter at the same effort level as they would be on the flat. And the vectors of force are different. I suspect the brain can tell the difference, and would not be as adapted to the length and direction of hop required in each stride for really fast running. So different stresses, different training adaptation. Then there’s the downhill issue – trying to go really fast downhill increases the forces on your body with each step, increasing the risk of injury.
Running fast on a forgiving flat surface like a rubberized or cinder track helps reduce the risk of injury, while allowing your body to adopt the proper range of motion, cadence, and effort level required to go as fast as possible for the interval time. I live at the bottom of a hill, with three roads out/up. One leads in 3/4 of a mile/200′ to a middle school cinder track. That’s where I do my speed work, or else I drive to the rubberized high school track a few miles away.