We all know hilly race courses make for slower race times, and we can feel that hills are more demanding than level running. But what changes, physiologically? Why do we feel these changes on hills?
A fantastic article out of the Journal of Sports Medicine this month reviewed all of the current literature on the biomechanics and physiology of uphill and downhill running. The authors divided the data into categories of biomechanical adaptations, neuromuscular adaptations, and “other” physiological aspects of hill (up or down) running.
Let’s look at uphill running first. Everyone’s initial thought is that this is harder than running downhill, and they are not wrong. Uphill running takes more energy because of the mechanical energy (what you produce) required to overcome the potential energy (essentially gravity) of the uphill slope. So it makes sense that uphill running would exhibit greater muscular activity— because the muscles have to generate the energy to get you up the hill—but this also results in quicker lactate accumulation. The lactate accumulation uphill is still quicker even if the pace is slowed while running uphill. Along the same lines, glycogen depletion was higher in uphill running, even compared to running on flat surfaces at the same intensity. Glycogen is fuel for your muscles - this is why you need to refuel with carbohydrates during marathons, or really any run greater than or equal to 2 hours.
When we break it down biomechanically, running uphill results in higher step frequency (so more work) and more of a mid to forefoot strike to reduce the severity of impact, especially to your tibia (shin bone). Your ankles, knees, and hips flex more at foot strike when running uphill to compensate for the change in impact. Your hips will also achieve more extension in the push off phase of running—most likely because it takes more work (using those glutes!) to get up the hill. Overall, your leg joints work 28% more going uphill.
So, even if you slow down going uphill, your body will still use more energy and experience quicker lactate accumulation and glycogen depletion. Your hips, knees, and ankles have to work 28% harder running uphill due to the biomechanical changes necessary to accommodate the graded surfacer. No wonder it feels harder!
With this information under your belt, it can change your mental game when it comes to tackling an uphill portion of a course... and maybe now you will be a little more accepting when you see hill repeats on your training schedule!
Look out for what happens when you’re running downhill soon!
Vernillo G Giandolini M Edwards WB. “Biomechanics and physiology of uphill and downhill running". Journal of Sports Medicine. 2016; epub ahead of print: 09 August.
- Cathlin Fitzgerald, PT, DPT, CSCS, CAFS
- NY Custom PT & Performance
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