It’s the time of the year when everyone sets their goals of losing weight and becoming fit. Some do P90X, Insanity, Cross Fit, or simply just join a gym to accomplish these tasks. Running tends to be a fitness activity that is easy to do, can be done almost anywhere, and is rather inexpensive. What tends to stop most individuals from continuing to run is overuse injuries or pain. This is typically due to improper training regimens. Our society has the belief that no pain equals no gain, so we push harder thinking we will get more benefit from the workout. While this can be true some of the time, if most workouts are done at maximum potential this can lead to negative effects such as injury and the inability to improve aerobically.
One of the key points to understanding this comes from realizing how our bodies utilize energy. One of the sources of fuel our body uses is glucose which we obtain from glycogen stores in our body. Glucose is the secondary source of long term energy storage in our body (the primary energy stores being fats held in adipose tissue). At all times our body is using both glucose and fats for energy with the key being the right ratio. Elite marathoners have trained themselves to burn primarily fat for the majority of the race leaving glucose for the secondary fuel source. The reason is that we only have enough glucose at hand for about 60 minutes of intense activity at which point we will have to rely on external sources of glucose. When we ingest supplemental glucose some is used for energy and some gets stored because as we ingest glucose our bodies release insulin which functions to store the glucose. By training slower over longer durations our body becomes efficient at utilizing fat thereby reducing the need for external sources of glucose. This leads to burning more fat.
Consider that when one exercises at maximum potential for one hour, they will most likely primarily burn glucose. At exhaustion glucose utilization initially decreases more than glucose production, which leads to greater hyperglycemia, requiring a substantial rise in insulin for 40–60 min to restore pre-exercise levels. So little fat if any gets burned, insulin levels ultimately rise resulting in storage of more glucose that will be converted into glycogen. Only so much can be stored as glycogen and the rest is stored as fat.
So if you want become more fit, reduce your risk of injury, and burn more fat – turn to long slow runs of moderate exertion over periods of up to 60 minutes. Exertion levels can be better understood by training according to your heart rate. See my blog on heart rate training –The Maffetone Method for Running: How slowing down can make you faster. Need a heart rate monitor? . Click here for an inexpensive yet reliable heart rate monitor.