“I will stop training you if I see you running.” My trainer said to me recently. Stop running? Wasn’t too long back that the passage of time would invariably witness me curled up in bed. Now all of a sudden running wasn’t good enough. What was going on? The key to this question lies in the complexity of the human body.
Our body needs energy to function. This is your basal metabolic rate. Once up and about, your body uses different energy systems to function. Depending on the nature of the activity your body uses the energy system that is most likely to meet its energy needs. Lifting 250 pounds in a single lift is not the same as walking at 3KM per hour. The first uses your phosphagen energy system. Most often, you use your anaerobic system. This is your body trying to function with a lack of sufficient oxygen. What happens now is extremely interesting. Your body is literally consuming the muscles you worked so hard to build to function. There is one more fly in the ointment however. The rate at which your heart is pumping for the activity to be performed. If you are 60% of your maximum heart rate you are consuming part glycogen (sugar) and part fat. As you go closer to your maximum, you start to consume only glycogen.
So what is all this fuss about running then? As you walk, jog or run your body begins to adapt. Initially you might be huffin and puffin (high heart rate) like the bad wolf in the story of the three pigs . Very soon your capacity to perform that exercise grows and your heart rate does not increase to anywhere close to its maximum. The outcome is that running or walking at steady state will more likely consume muscle than sugar. And you worked so hard to build that muscle didn’t ya!