Spending too many hours working out is one of the least efficient ways improve metabolism. It is impossible to work out at an intense pace for an extended period of time, while exercising at a moderate pace does not allow an athlete to achieve the exertion needed to reach the fat burning zone. Interval training has been proven to be a much better approach to boosting metabolism. A study conducted by the University of Alabama demonstrated that interval training burns three times as many calories as traditional training.

Lactic acid is produced in the muscles when glucose is broken down during strenuous muscular activity. Pushing to the lactate (anaerobic) threshold increases energy exertion by boosting the amount of lactic acid in muscle tissue. Lactate threshold is reached when the body no longer has sufficient oxygen for the muscles to function.

In the past, athletes were recommended to avoid exercising to the lactate threshold, as it was believed this would cause muscle soreness and limit ability to exercise. This belief stemmed from an experiment conducted on dissected frog legs that were found to contain high levels of lactic acid after receiving an electric shock. The frog legs contracted several times before they stopped functioning.

However, there is no direct correlation between muscle soreness and lactic acid. In fact, muscle soreness occurs one to three days after a workout, whereas the body is free from lactic acid after just one hour.

Lactic acid metabolizes carbohydrates from the diet without increasing insulin levels or triggering fat synthesis. The ultimate goal of a workout, therefore, is to burn more lactic acid rather than produce less. This is best achieved by interval training, especially given that it is impossible to continue working at the anaerobic threshold beyond short intervals.

The Role of Interval Training

Interval training involves exercising at the highest intensity possible for a specific period, interspersed with bouts of lower-intensity “active rest” exercise. Starting out, many experts recommend high-intensity intervals of at least 30 seconds, as anything less than this does not induce a lactic acid release. As you increase your lactate threshold, the length of intervals should be extended. A proper active rest interval lasts as long as it takes to you to reduce muscle lactate levels to a state where you can return to maximum effort.

Interval training helps the body to build up a tolerance to lactic acid by working through the burning sensation. Prolonging the release of lactic acid in muscles makes the workout more effective at improving metabolism and burning fat. Pushing the body to the anaerobic threshold improves metabolism even after the athlete stops exercising; effects can be felt up to 24 hours after the workout. For this reason, it is critical to eat food high in protein immediately after exercising to repair and replenish muscles.

Whether you’re a competitive athlete trying to take your performance to the next level or a weekend warrior looking to shed a few pounds, interval training is one of the most efficient ways to burn lactic acid in muscles and increase metabolism.