Muscle Damage & Running Economy (Part 1)

     In grad school, we had to come with a research topic and collect data in the lab... It was more or less collecting pilot data for potential research topics. Being the endurance nerd I am, I somehow convinced my lab partner (who had little or no interest in running) that we should look into the effect of muscle damage on running economy.

     We decided we'd collect running economy data using a metabolic cart while running on the treadmill, complete a "muscle damage" protocol then collect running economy data again 48-hours post muscle damage. I hypothesized we'd see a decrease in economy, and it'd feel absolutely awful.

     I don't think I've ever been or ever will be more sore than I was after completing 6 sets of 10 eccentric leg press AND 100 depth jumps from 60cm. I stumbled out of the weightroom on Jell-O legs and my running would suffer for nearly a week - just from one workout that probably took less than an hour to complete.

     A couple days later, we saw an increase in oxygen consumption at a sub-maximal running speeds and a very predictable increase in our rating of perceived exertion (RPE). Shocking right? While we only had two participants (n = 2), this is consistent with other research. Muscle damage decreases the efficiency of skeletal muscle - from decreased muscle-tendon stiffness, to increased motor-unit recruitment and decreased mitochondrial function. There is a number of potential mechanisms. It can also alter range of motion and running form... potentially leading to the adoption of less efficient stride. So, the decrease in running economy is multi-factorial - it's physiological and biomechanical.

     It's been 10 years since this project, but I was thinking about it this morning as I started my run... shuffling to get started; sore from my efforts two days ago. Running felt labored and I was not moving very fast...

     It made me think about ultra and marathon races. Muscle damage is surely a factor in these long running events. Running is an inherently plyometric activity - eccentric loading is unavoidable. Eccentric loading is typically cited as a cause of muscle damage - and muscle damage is well documented in distance running. Some muscle damage protocols actually use downhill running to impart damage (increased eccentric loading with downhill running).

     So, what impacts might muscle damage, during a race, have on physiology in the late stages of that race?

More on that later...

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