While in Vermont recently, I took advantage of the opportunity to run through the scenic countryside. This provided some beautiful scenery, but also tough terrain. The paths included runs up steep hills and mountain side roads (as you see in the pictures). As I continued to run uphill, my legs began feeling heavier and overall fatigue led me to question what is happening to our bodies as we run uphill?
The first thing I noticed when the terrain changed from a fairly flat surface to an incline was that I was becoming out of breath. When investigating this further in the research, it has been shown running on an inclined surface causes a greater oxygen deficit.1 Oxygen deficit refers situations in which there is a lack of oxygen available compared to the amount that is needed for energy demand (or the work being done--in my case, running uphill). When this happens your breathing becomes more labored and your body turns to other forms of energy until you can reach a more steady state. When comparing running on a flat surface to running uphill, research by Sloniger, et al found uphill running created a deficit that was 21% greater². Other studies have found an oxygen deficit of 37% at a 10.5% grade and approximately 80% at a 15% grade.
Research has shown that oxygen deficit may be due to an increase in muscle mass activation in the lower body.1 The percentage of muscle volume activated was 9% higher in uphill running versus flat surfaces. As a result of the greater volume activated, more oxygen is needed and thus causes a larger deficit. Additionally, when looking at the specific muscles being activated, there is a change in which muscles are used and the percentage they are used at. When running uphill the vastus group of the quadriceps and the soleus muscle of the calf were activated considerably greater than when running on a flat surface.2 A few muscles, such as the hamstrings and rectus femoris of the quadriceps (muscle of the quadriceps that crosses the hip and knee joints), had decreased activation during uphill running. 2.3 Thus uphill running might be a consideration for those who are returning to running from a hamstring issue as the hamstring isn’t used as much.
The change in muscle activation may be due to the change in running mechanics when running uphill according to the research.3 Running uphill causes a decrease in the length of strides and overall stride rate. Additionally, the time used for the push off phase of running increased about 26.4%. As a side note, these changes in running mechanics, may be useful in helping the acceleration phase of running.
Vermont was a great place to combine beautiful scenery and tough hills into a fun and challenging workout. Share pictures of your favorite hills to run on our facebook page.
1 Sloniger, MA., Cureton, K.J., Prior, B.M., Evans, E.M.; Lower extremity muscle activation during horizontal and uphill running. J. Appl. Physiol. 83(6):2073–2079, 1997.
2 Sloniger, MA., Cureton, K.J., Prior, B.M., Evans, E.M.; Anaerobic capacity and muscle activation during horizontal and uphill running. J. Appl. Physiol. 83(1): 262–269, 1997.
3Slawinski, J., Dorel, S., Hug, F., Courturier, A., Fournel, V., et al.; Elite Long Sprint Running: A Comparison between Incline and Level Training Sessions. Med. Sci. Sports Exerc., 40(6): 1155-1162, 2008.