The Physical Activity Guidelines for Americans make the message clear: Being active is the single best thing you can do to improve your health<sup>1</sup> and reduce your risk of all-cause mortality.
Exercise keeps your body nimble and able to accomplish everyday tasks like carrying the groceries into the house, weeding the garden, and chasing after kids (or grandkids), no matter your age.
Two forms of activity exist, aerobic and anaerobic exercise. The terms define the types of muscle fibers your body uses, the duration, and the intensity of what you do. They also refer to the processes by which energy is broken down and produced.
Aerobic activities, such as running, require oxygen to produce adenosine triphosphate (ATP), or energy.
Anaerobic means “without oxygen.” While it might be baffling to imagine exercise without oxygen, anaerobic exercise breaks down glucose in the body without using oxygen. It means you’re working at such a high intensity that your cardiovascular system isn’t able to get oxygen fast enough to your muscles.
Of course, your muscles need oxygen, so anaerobic work is abbreviated. You’re only able to sustain 90 to 100% of your max heart rate for short periods—think 20- or 30-second intervals with 20 to 60 minutes of rest between sets.
Sprinting, high-intensity interval training (HIIT), and weightlifting (think powerlifting or heavy weightlifting) are classic examples where you can work more intensely for shorter durations than aerobic workouts.
Both anaerobic and aerobic exercise are vital to your well-being.
Let’s take a closer look at the benefits of anaerobic exercise.
Burn Fat During and After the Workout
The fuel you use to power your workout<sup>2</sup>—whether that’s glucose (carbs), glycogen (stored glucose), or fat—depends on how hard you work.
If the intensity is low, your body burns more fat<sup>3</sup>. As you turn up the intensity, you burn more glycogen and/or glucose, but you still burn fat when you exercise anaerobically. The fat-burning bonus comes after your anaerobic workout stops.
To illustrate, one small study on young male adults tested the energy expenditure during and after steady-state exercise and high-intensity interval training. While the study showed that HIIT expended less energy than steady-state exercise, HIIT generated greater energy expenditure during EPOC (post-exercise oxygen consumption) while also using more grams of fat<sup>4</sup>.
Build Muscle Mass
Moving anaerobically benefits your cardiovascular system<sup>5</sup> and builds stronger muscles.
One study conducted on 12 young, elite handball players showed that sprint intervals (four short, 250-meter repeats at 80% of max speed) led to significant increases in anabolic hormones<sup>6</sup>—growth hormone and insulin-like growth factor—involved in building strength.
Increase Your VO2 Max
Those 30-second all-out burpee intervals do more than just leave you winded. Anaerobic exercise helps you improve your VO2 max, a measure of the maximum amount of oxygen your body can use during exercise.
It may seem counterintuitive that anaerobic exercise can improve how efficiently your body uses oxygen, but, as this study suggests, oxygen was used during sprinting<sup>7</sup>. It appears that quick, intensive bouts of anaerobic work improve both anaerobic and aerobic energy systems<sup>8</sup> significantly.
Boost Your Metabolism
Bump up the fat-burning potential of your workout by combining aerobic and anaerobic efforts. One study observed the greatest fat mass reduction in a group of obese participants who performed 25 minutes of an aerobic workout followed by a five-minute anaerobic closer. Aerobic plus anaerobic training produces greater lipid metabolism without significant changes to glucose<sup>9</sup> levels, study authors concluded.
Strength training not only helps you build stronger muscles but also increases your resting metabolic rate<sup>10</sup>—the calories you burn when you’re not exercising—without changing fasting glucose or insulin levels.
Another study on participants with impaired (high) fasting blood glucose (100–125 mg/dL) asked groups to complete resistance exercises at moderate (65%) intensity in various amounts and the other at high (85%) intensity in various amounts. All groups showed improved insulin sensitivity with the high-intensity group performing multiple sets of the exercises to be the most effective in increasing insulin sensitivity and lowering fasting blood glucose<sup>11</sup>.
<p class="pro-tip"><strong>Learn more about </strong> <a href="/blog/metabolic-health-strength-training">strength training and metabolic health</a>.</p>
Trim Your Waistline
High-intensity interval training can help you slim your waist. One study showed significant reduction in the waist-to-hip ratio<sup>12</sup> of participants who completed three months of HIIT at 20% above anaerobic threshold three times a week.
A review of research states that anaerobic high-intensity intermittent training produces greater abdominal fat reduction<sup>13</sup> than continuous aerobic training at similar amounts of energy expenditure.
A different review examined the mechanisms behind the increased fat-burning<sup>14</sup>, and particularly subcutaneous abdominal fat burning, effects of high-intensity intermittent exercise (HIIE). It points to suppressed appetite after the workout, fat oxidation during and after HIIE, and significantly lowered insulin that results in increases in the muscles’ capactiy for fatty acid oxidation.
Slow Age-Related Muscle Loss
We lose muscle mass as we age. Combat this decline in fat-free mass by including protein-rich whole foods in your diet and through exercise, particularly weight lifting and bodyweight resistance exercises (such as push-ups, planks, lunges, and squats).
"Without question, exercise is the most powerful intervention to address muscle loss, whether it occurs in the context of advancing age or debilitating chronic or acute diseases," explains Nathan K. LeBrasseur<sup>15</sup>, Ph.D. of the Department of Physical Medicine and Rehabilitation at the Mayo Clinic in Rochester, Minn.
Age-related muscle loss or sarcopenia can be a vicious cycle. You lose muscle mass, and exercise becomes harder and more painful. You may decide to skip it altogether to avoid the discomfort but eventually even walking upstairs or to the bathroom can prove difficult. Even if you’ve been inactive for a while, a modest increase in light activity offers significant health benefits<sup>16</sup>.
Build Strong Bones
As you build muscle, you also strengthen your bones, particularly with weight-bearing exercises. That makes anaerobic exercises, such as sprinting, excellent ways to maintain your muscle and bone mass as you age to help prevent osteoporosis<sup>17</sup>.
Researchers have found that combining aerobic and anaerobic exercise can increase bone mass density better<sup>18</sup> than walking alone can. The same research review summarized that progressive resistance training<sup>19</sup> poses the most effective impact on bone mineral density.
Improve Joint Health
Anaerobic exercise can make it easier for you to get around by keeping your joints healthy. These workouts will target the muscles, ligaments, and cartilage supporting them, and leave you less vulnerable to injury. A program of both aerobic and anaerobic workouts is particularly helpful for the femur joint<sup>20</sup> (hip).
Help Diminish Your Risk of Falls
Anaerobic workouts targeting your core muscles can improve your balance and reduce your risk of a fall. They can decrease your chances of a serious injury, as well-trained, strong muscles and bones can handle impact better. It may also help keep you from hitting the floor because you’ll be able to catch yourself faster.
Hip fractures<sup>21</sup> are especially debilitating in seniors with a significant loss of quality of life. Think of anaerobic exercise like strength training as insurance for an independent life as you age.
Reduce Your Risk of DOMS
Some people may forgo strength training or HIIT because of dreaded delayed onset muscle soreness (DOMS). The first step is always the hardest, and the intensity of anaerobic exercise, while thankfully brief in nature, is something you’ll need to work up to over time.
If you start an anaerobic exercise plan and stick to a regular schedule, your muscles will adapt. That’s why individuals typically find they have to increase weight or reps to get the same results. Scientists call it the repeated bout effect<sup>22</sup>.
As you build muscle mass, your strength increases, as does your ability to withstand the stress of the exercise. You’ll start to recover more quickly from workouts, and that includes any lingering or delayed muscle soreness.
Improve Your Mood
Intense workouts encourages your brain to produce and release endorphins<sup>23</sup>, the so-called runner’s high. Researchers from the University of Bonn confirmed this hypothesis through brain imaging. 'We could validate for the first time an endorphin-driven runner's high and identify the affected brain areas,” explained Professor Henning Boecker.
Boost Your Brainpower
Anaerobic exercise may also improve your brain health. A study looked at the effects of interval training and exercising continuously at the same rate (at 60% max) on brain blood flow. Researchers found that blood flow to the brain<sup>24</sup> was higher in during 10 minutes of continuous exercise but the total accumulated change in middle cerebral artery blood velocity was higher with the interval workout (10 x 1 minute at 60% max).
The takeaway: Even slightly higher-than-moderate-intensity exercise for short bouts, either continuous or in intervals, can increase blood flow to the brain.
Another study reviewed the effects of different effort levels on cognitive performance in elderly women. Trial results revealed that exercise performed at 90% of anaerobic threshold (when oxygen consumption goes about aerobic energy production, causing a rapid increase in lactate and metabolic acidosis) resulted in significant improvements in the performance of executive functions<sup>25</sup> (EF). Exercise at 60% of anaerobic threshold did not improve EF, and exercises completed at 110% of anaerobic threshold only improved performance in verbal fluency.
Lower Your Risk of Chronic Disease
The Physical Activity Guidelines for Americans<sup>26</sup> recommend that adults exercise at least 150 minutes a week at moderate intensity. They also encourage people to do strength training workouts at least two times a week. Taking these vital steps can reduce your risk of chronic health disorders, such as heart disease and diabetes.
Research shows that anaerobic training leads to improvement in glucose clearance and insulin sensitivity<sup>27</sup>, body mass index, blood pressure, and more beneficial effects on the cardiovascular system than lower-intensity training. That said, the research review also points out that too much anaerobic training could contribute negative effects by increasing the risk of cardiovascular disease.
The takeaway: Spread out your anaerobic efforts to a couple of times a week at most, and combine these workouts with lower-intensity aerobic or resistance training sessions.
Enhance Your Quality of Life
If we take all these benefits together, one thing becomes clear: Anaerobic exercise can improve your well-being in myriad ways. It can make both everyday activities and workouts easier and less painful. It can enhance your appearance, mood, brain function, and more. These workouts can make aging and its effects more manageable while reducing your risk of chronic diseases.
The question isn’t if you should add strength training or HIIT to your routine, but how and when. It’s one of the best ways to take charge of your health and reap the long-term benefits.
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