Anaerobic exercise is a growing trend in the fitness world. Unlike aerobic training where you work out at a relatively comfortable pace – anaerobic training is vigorous exercise. It leads to a higher level of fatigue – and a higher level of fitness. Find out why anaerobic exercise deserves a place in your fitness routine.
What is Anaerobic Exercise?
Anaerobic literally means “without oxygen.” When you’re exercising at a relatively comfortable pace, so-called moderate-intensity, aerobic exercise, you can supply your muscle cells with enough oxygen to make ATP through a process called oxidative phosphorylation. Oxidative phosphorylation takes place primarily inside the mitochondria of cells. Aerobic energy production produces lots of ATP. The downside is it requires a continuous supply of oxygen to keep making it.
When you first begin a workout, your muscles initially tap into existing ATP energy stores – but these stores are very limited. In fact, they’re only good for a second or two of exercise. Once ATP stores are no longer available, muscle cells tap can use a high-energy compound called creatine phosphate to make ATP. Unfortunately, ATP generation from creatine phosphate doesn’t last long either – usually no more than 10 seconds. At this point, muscle cells turn to glycolysis, a system that doesn’t require oxygen. After about two minutes, oxidative phosphorylation starts to kick in, an ATP-generating system that requires oxygen. Of course, this is all simplified. Cells usually use a combination of energy systems to produce ATP. The one that’s favored at any given time depends upon the intensity of the exercise. As exercise intensity increases, cells are forced to depend more on anaerobic ATP generation.
What Happens When You Work Out at a High Intensity?
As you increase the intensity of your workout there comes a point where your heart and circulatory system can’t deliver oxygen to your muscle cells quickly enough to use oxidative pathways for making ATP. That’s when cells have to depend on anaerobic pathways, including glycolysis, for making ATP. These pathways don’t require oxygen. The downside is they cause a rapid rise in lactate inside muscle cells. As the intensity increases, lactate increases so rapidly muscle cells can’t remove it fast enough. As a result, blood lactic acid levels began to increase at an exponential rate. When the rise in lactate becomes exponential, this corresponds with the lactate or anaerobic threshold. Factors other than lack of oxygen may also limit the ability of muscle cells to use oxidative pathways.
Anaerobic Exercise and the Lactate Threshold
What happens when you cross over the lactate threshold? As lactic acid levels increase, your blood pH drops or becomes more acidic. It’s this increase in acidity that partially explains why your muscles burn when you do high-intensity exercise. In actuality, your muscle cells still use aerobic means of producing ATP to some degree during high-intensity exercise but they depend more on anaerobic energy production as exercise intensity goes up.
What Types of Exercise Are Anaerobic?
Anaerobic exercise is any form of exercise that involves an intense burst of activity – sprinting, heavy weight lifting, jumping, high-intensity interval training, etc. Anaerobic exercise is short in duration because your performance is limited by muscle fatigue. If you’re able to sustain an activity for more than a minute or two, there’s a significant aerobic component and it’s not truly anaerobic.
What Are the Benefits of Anaerobic Training?
When you train above your lactate threshold even for short periods of time, your body adapts by becoming more efficient at removing lactate as it builds up. It does this is by becoming better at buffering the acid (hydrogen ions) that accumulate during high-intensity exercise. As a result, you become fatigued less rapidly and develop greater endurance. From a weight-training standpoint, this buffering capacity helps you become stronger. As your ability to remove lactate from the muscle improves, you can eke an additional rep or two before your muscles become too fatigued to continue. Short bursts of activity also build power.
The Afterburn Effect
Another benefit of anaerobic training is the “after-burn” it creates. Afterburn is the extra work your body has to do to recover from a high-intensity workout. Workouts above the anaerobic threshold create an oxygen debt that has to be repaid. Ever notice how hard you’re breathing after a burst of high-intensity activity? That’s the oxygen debt in action. Now, the lactate that built up during high-intensity exercise can be converted to pyruvate and enter aerobic metabolism since you’re supplying muscle cells with more oxygen. Your breathing and core body temperature also has to return to normal. As a result, you keep burning extra calories for hours after a high-intensity session is over. Plus, high-intensity workouts and heavy resistance training maximize release of growth hormone, an anabolic hormone that also boosts fat burning.
How to Get the Benefits of Anaerobic Training
One of the best ways to tap into the fitness benefits of anaerobic exercise is with interval training. Short periods of high-intensity exercise (30 seconds to 2 minutes) with periods of recovery from 2 to 4 times as long maximally utilize anaerobic energy systems. Intervals longer than this have a significant aerobic component. If you want to improve your anaerobic fitness, keep the intervals short and the recovery periods longer. Plyometrics is another form of anaerobic exercise that builds power. Of course, heavy resistance training also taps mainly into anaerobic pathways and gives you a significant after-burn.
The Bottom Line?
Make sure you’re incorporating anaerobic training into your fitness routine. It will help you build stronger muscles, greater power and even improve your endurance by helping your body handle build-up of lactate better. Take advantage of this fat-scorching form of exercise with workouts that involve interval training, plyometrics and heavy weight lifting.
References:
“Lactate Threshold Training”. Len Kravitz, Ph.D. and Lance Dalleck, Ph.D.
IDEA Health and Fitness. “Revisiting Energy Systems”
JCEM. “Effect of low and high-intensity exercise on circulating growth hormone in men”
IDEA Health and Fitness. “Interval Training Advantages”
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