You’ve just finished your aerobic workout, you’re breathing hard and heavy, and your legs are weak and are burning like their on fire. ‘That fat is going to be burned up like crazy’ you think to yourself. What you might not know is that you may have just sabotaged your fat-burning quest because of the high lactic acid levels you have generated from your hard workout.
Lactic acid is a by-product of carbohydrates being burned to give you energy that is fast and that can fuel your high-intensity workouts. Its effects on your system show by making your muscles weak combined with a ‘burning’ sensation either during, near the end, or immediately after your exercise session. It can also be the culprit in causing nausea, dizziness, and headaches if levels become too high.
The problem with lactic acid comes when you are specifically trying to use up your fat stores by performing aerobic exercise. Since lactic acid is a readily available form of energy that can be used by your muscles, your body would rather use that than have to go through the long process of metabolizing fat. When you produce a lot of lactic acid by either exercising at a high intensity (85% – 100% of maximum heart rate) or by greatly increasing the energy demand on your muscles in a short period of time (for example by increasing the resistance on the stationary cycle too quickly or by beginning to run much faster), your body ceases to burn fat. Instead of using fat for energy, it uses lactic acid and carbohydrates in place of fat as its main source of energy to power the exercise.
So how do you structure your workouts to help optimize your fat reduction in an efficient manner? A proper warm-up at 50% – 55% of your maximum heart rate for 10 to 15 minutes will help to contribute to lower levels of lactic acid when you begin to exercise at your chosen workout intensity. The intensity with which you perform your fat-burning aerobic work should generally be at approximately 60% to 70% of your maximum heart rate. Exercising at this lower intensity will help to maximize fat loss as well as keep lactic acid levels low enough so as not to interfere with the fat burning process.
A cool down portion for 5 – 10 minutes at 50% of your maximum heart rate after your aerobic exercise can also help to reduce the rise in lactic acid following the session. Since the majority of your fat burning effects will often come after the exercise session (your metabolic rate can stay elevated for several hours following your aerobic workout), avoid doing any type of weight training or other high intensity exercise for 3 to 4 hours following your fat-burning workout since these types of exercise can produce high levels of lactic acid.
Optimizing your exercise routine to cause a reduction in body fat stores can sometimes be a tricky process. However, being physically active several times a week for at least 25 to 30 minutes a session is a large part of the process towards proper and long term body fat reduction.