Aerobic Exercise

Aerobic exercise not only improves fitness; it also has known benefits for both physical and emotional health.

Imagine that you're exercising. You're working up a sweat, you're breathing hard, your heart is thumping, blood is coursing through your vessels to deliver oxygen to the muscles to keep you moving, and you sustain the activity for more than just a few minutes. That's aerobic exercise (also known as "cardio" in gym lingo), which is any activity that you can sustain for more than just a few minutes while your heart, lungs, and muscles work overtime. In this article, I'll discuss the mechanisms of aerobic exercise: oxygen transport and consumption, the role of the heart and the muscles, the proven benefits of aerobic exercise, how much you need to do to reap the benefits, and more.

What is the difference between cardio and aerobic exercises?

Aerobic and cardio exercises are often used interchangeably, as they both entail activities that elevate heart rate and breathing, thereby enhancing cardiovascular health. However, they have slightly different mechanisms. Aerobic exercise focuses on utilizing oxygen for converting carbohydrates and fats into energy, whereas cardio exercise aims to boost heart rate and enhance the heart's pumping efficiency to meet the body's demand for oxygen. Aerobic exercise involves big muscle groups in rhythmic, repeating movements, which improves cardiovascular health and overall well-being. Aerobic exercises include brisk walking, cycling, swimming, dancing, and sports such as basketball and tennis.

Cardio exercises, also known as cardiovascular exercises, focus on the heart and circulatory system and include activities such as jogging, cycling, swimming, or rowing. While aerobic exercises refer to activities that increase heart rate and breathing, cardio exercises focus on strengthening the heart muscle and improving its efficiency in pumping blood throughout the body. All cardio exercises are aerobic exercises since they raise heart rate and oxygen intake. However, not all aerobic exercises are cardio-focused, as they also focus on muscular endurance and flexibility.

The beginning

It all starts with breathing. The average healthy adult inhales and exhales about 7 to 8 liters of air per minute. Once you fill your lungs, the oxygen in the air (air contains approximately 20% oxygen) is filtered through small branches of tubes (called bronchioles) until it reaches the alveoli. The alveoli are microscopic sacs where oxygen diffuses (enters) into the blood. From there, it's a beeline direct to the heart.

Getting to the heart of it

The heart has four chambers that fill with blood and pump blood (two atria and two ventricles) and some very active coronary arteries. Because of all this action, the heart needs a fresh supply of oxygen, and as you just learned, the lungs provide it. Once the heart uses what it needs, it pumps the blood, oxygen, and other nutrients out through the large left ventricle and the circulatory system (cardiovascular system) to all the organs, muscles, and tissues that need it.

A whole lot of pumping going on

Your heart beats approximately 60-80 times per minute at rest, 100,000 times a day, more than 30 million times per year, and about 2.5 billion times in a 70-year lifetime! Every beat of your heart sends a volume of blood (called stroke volume -- more about that later), along with oxygen and many other life-sustaining nutrients, circulating through your body. The average healthy adult's heart pumps about 5 liters of blood per minute.

Oxygen consumption and muscles

All that oxygen being pumped by the blood is important. You may be familiar with the term "oxygen consumption." In science, it's labeled VO2, or volume of oxygen consumed. It's the amount of oxygen the muscles extract or consume from the blood, and it's expressed as ml/kg/minute (milliliters per kilogram of body weight). Muscles are like engines that run on fuel (just like an automobile that runs on fuel); only our muscles use fat and carbohydrates instead of gasoline. Oxygen is a key player because, once inside the muscle, it's used to burn fat and carbohydrates for fuel to keep our engines running. The more efficient our muscles are at consuming oxygen, the more fuel we can burn, the more fit we are, and the longer we can exercise.

The average sedentary adult will reach a level of oxygen consumption close to 35 ml/kg/minute during a maximal treadmill test (where you're asked to walk as hard as you can). Translated, that means the person is consuming 35 milliliters of oxygen for every kilogram of body weight per minute.

That'll get you through the day, but elite athletes can reach values as high as 90 ml/kg/minute! How do they do it? They may have good genes for one, but they also train hard. And when they do, their bodies adapt. The good news is that the bodies of mere mortals like the rest of us adapt to training too.

The U.S. Centers for Disease Control and Prevention (CDC) recommends aerobic exercise as a crucial component of a healthy lifestyle. Aerobic physical activity makes you breathe faster and your heart beat quicker. This promotes blood circulation, strengthens the heart and lungs, aids in weight management, elevates mood and energy levels, and builds muscle strength and endurance.

The U.S. National Institutes of Health (NIH) recommends individuals to engage in at least 150 minutes of moderate-intensity aerobic activity per week, such as 30 minutes a day, 5 days a week. According to the NIH, regular aerobic exercise, such as brisk walking, jogging, or swimming, reduces the risk of heart disease, hypertension, type 2 diabetes, and cancer. Doing aerobic exercise regularly can help you live a longer, healthier life by improving both your physical and mental health.

According to the CDC, adults need at least 150 minutes of moderate-intensity activity, or 75 minutes of vigorous-intensity activity, or a mix of both, every week. Adults also need at least two days of muscle-strengthening activity each week. You don't have to do it all in one go. It's okay to break it up into smaller sessions throughout the week, like 30 minutes a day for 5 days.

The Physical Activity Guidelines for Americans, released by the US Department of Health and Human Services (HHS) highlight the importance of physical activity and a balanced diet in promoting good health and lowering the risk of chronic diseases.

Here are the key CDC recommendations (based on the Physical Activity Guidelines for Americans) on the appropriate amount of exercise for maintaining health across different age groups and special populations:

• Preschool-aged children (aged 3-5): They should be physically active throughout the day to enhance growth and development.
• Children and adolescents (aged 6-17): They should engage in at least 60 minutes of moderate-to-vigorous physical activity daily, primarily aerobic activities. Muscle-strengthening and bone-strengthening activities should be included at least three days a week.
• Adults: Adults should aim for at least 150 to 300 minutes of moderate-intensity aerobic activity per week, or 75 to 150 minutes of vigorous-intensity aerobic activity per week. Muscle-strengthening activities that involve all major muscle groups should be performed on two or more days a week.
• Older adults (65 years and above): The recommendations are similar to those for adults, but older adults should also include balance training and take into account their fitness levels and any chronic conditions.
• Pregnant and postpartum women: They should aim for at least 150 minutes of moderate-intensity aerobic activity per week. Those who were physically active before pregnancy can continue their activities with medical consultation.
• Adults with chronic health conditions and disabilities: Adults with chronic diseases or disabilities with good mobility should aim for 150 to 300 minutes of moderate-intensity aerobic activity or 75 to 150 minutes of vigorous-intensity aerobic activity each week, along with muscle-strengthening activities for two or more days. If they are unable to reach these standards, they should engage in regular physical activity appropriate to their abilities.

There are two other physical activity guidelines in the United States.

• The first, the Surgeon General's Report on Physical Activity and Health, is a lifestyle recommendation. That is, you can modify it to fit into your daily routine and activities of daily living. The recommendation is that for substantial health benefits, adults should do at least 150 minutes (2 hours and 30 minutes) to 300 minutes (5 hours) a week of moderate-intensity, or 75 minutes (1 hour and 15 minutes) to 150 minutes (2 hours and 30 minutes) a week of vigorous-intensity aerobic physical activity, or an equivalent combination of moderate- and vigorous-intensity aerobic activity. Preferably, aerobic activity should be spread throughout the week. Moderate intensity is equivalent to feeling "warm and slightly out of breath" when you do it.
• The second recommendation is from the American College of Sports Medicine. The ACSM recommends performing moderate-intensity aerobic activity for a minimum of 30 minutes, five times per week OR vigorous-intensity aerobic activity for a minimum of 20 minutes, three times per week.

Which one you choose is a personal choice. They are not intended to compete with each other but rather to provide options and maybe even complement each other. Of course, there's no downside to working out regularly with aerobic exercise and also becoming more physically active as per the Surgeon General (take more stairs, mow the lawn by hand, park far away from the store, and walk), so combining them might be a good decision.

There are several ways to approach aerobic training. I'll use walking as an example of aerobic activity and go through some of the training methods. You can plug in any other aerobic activity if you prefer, such as running.

"Is walking an aerobic exercise?"

Walking is regarded as an aerobic exercise, as it requires sustained action with broad muscle groups at a moderate intensity, relying on oxygen to convert carbohydrates and lipids into energy. Walking for extended durations improves cardiovascular health, helps with weight management, and strengthens lower-body muscles. Moreover, walking contributes to mental well-being by reducing stress and anxiety. It's accessible to practically everyone because it doesn't require any particular equipment and can be done anywhere.

What are the “5 aerobics?”

Five examples of aerobic exercises other than walking include:

Running or jogging:

• Running or jogging is a faster-paced activity and is typically done outdoors or on a treadmill.
• It improves cardiovascular health, burns calories, increases leg strength, and boosts mental health.

Swimming:

• Swimming involves propelling oneself through water with synchronized arm and leg movements.
• It may include many strokes such as freestyle, breaststroke, backstroke, and butterfly.
• It offers a full-body workout with minimum impact on joints, increases cardiovascular fitness, and strengthens muscles.

Cycling:

• Cycling can be done on a stationary bike or outside on a bicycle.
• It involves pedaling to move the bike forward or maintaining a consistent pace on a stationary cycle.
• It improves cardiovascular health, strengthens legs and core muscles, has a low impact on joints, and can be enjoyed as a social activity.

Dancing:

• Dancing involves rhythmic movements to music.
• Various forms of dancing include Zumba, hip-hop, salsa, and ballroom.
• Dancing promotes cardiovascular health, improves coordination and balance, burns calories, and is enjoyable and entertaining.

Rowing:

• Rowing can be done on an ergometer or in water.
• Pulling a handle toward the torso while pushing with the legs simulates rowing motion.
• It provides a full-body workout, improves cardiovascular fitness, strengthens back, arm, and leg muscles, and offers low-impact joint training.

"Simple" aerobic training

The simplest method of starting is just that simple. Select the number of minutes you'd like to walk for (let's say 20 minutes for your first walk) and head out the door or step on the treadmill and go for it. Remember that to make it aerobic you want to walk at a pace that leaves you feeling "warm and slightly out of breath" and one that you can sustain for the time that you planned. In this case, set your sights on completing 20 minutes and pace yourself to do it. If you start too quickly, then you may poop out too soon. It's not important how fast you do it; it's just important that you attempt to complete the time. If you find 20 minutes is too ambitious, then start with less. Again, the most important thing is to get started. You can always add more later on.

Simple aerobic training, such as step movements, is an excellent technique to boost cardiovascular fitness, coordination, and muscle strength.

Aerobic step exercises include:

Basic step-up:

• Put your right foot onto a step and raise your left foot to keep it next to your right foot.
• Step down with your right foot and then bring down your left foot.
• Repeat it as if you are going up and down the stairs.
• This exercise strengthens your legs and glutes while improving cardiovascular fitness.

Step touch:

• Stand next to the step.
• Step up with your right foot and then tap your left foot against the step.
• Step down with your left foot, then your right foot.
• Repeat on the opposite side.
• This exercise improves coordination and balance while offering a cardiovascular workout.

Knee raises:

• Step up with your right foot, then raise your left knee to hip level.
• Step down with your left foot, then your right foot.
• Repeat on the opposite side.
• This exercise enhances balance, coordination, and core strength.

Lateral step-up:

• Stand sideways to the step.
• Step up sideways with your right foot, then lift your left foot to meet it.
• Step down with your left foot, then your right foot.
• Repeat on the opposite side.
• This exercise improves lateral movement and coordination, as well as leg and glute strength.

Step kicks:

• Step up with your right foot and kick your left foot forward.
• Step down with your left foot, then your right foot.
• Repeat on the opposite side.
• This exercise increases heart rate, boosts flexibility, and strengthens legs.

Five-out, five-back training plan

As discussed above, I like the simplicity of the five-minute out, five-minute back aerobic training plan. And like I said, you can increase gradually to 15 minutes out, 15 minutes back. It's aerobic and you'll get a training effect as long as you feel warm and slightly out of breath when you do it.

Interval training

Interval training is more intense than simple aerobic training. It's a very effective way to increase your fitness level (remember stroke volume and mitochondria activity!), but it's tough, so I recommend holding off until you build up to 20-30 minutes of aerobic exercise. The idea of intervals is to set up work to active-rest ratios (work:active-rest), and as you get more fit, decrease the active-rest interval and increase the work interval. The work interval of the ratio is a speed that is faster than what you usually do, and the active-rest interval is your usual speed. To do it, you start at your usual speed for five to eight minutes, then increase the speed to the work interval for one to three minutes, then slow down to your usual speed for a few minutes to catch your breath (this is the active-rest interval), and then you repeat the cycling for the duration of your workout.

Here are some examples of interval training using walking as the activity:

Training Plan #1

Try the following if you currently walk for 30 minutes at 3.5 mph on the treadmill.

• Interval 1: 3.5 mph for five minutes to warm up
• Interval 2: 3.8 mph for one minute
• Interval 3: 3.5 mph for three minutes to catch your breath (active rest)
• Interval 4: 3.8 mph for one minute
• Interval 5: 3.5 mph for three more minutes, and so on until you reach 30 minutes.

After a few weeks, you can try increasing using plan #2.

Training Plan #2

The work:active-rest ratio in the above example is 1:3. Over weeks and months, you increase the work interval and decrease the active rest. For example:

• Interval 1: 3.5 mph for five minutes to warm up
• Interval 2: 3.8 mph for two minutes
• Interval 3: 3.5 mph for two minutes (active rest)
• Interval 4: 3.8 mph for two minutes
• Interval 5: 3.5 mph for two more minutes, and so on until you reach 30 minutes.

Training Plan #3

The work:active-rest ratio in the above example is 1:3. Over weeks and months you increase the work interval and decrease the active rest. For example:

• Interval 1: 3.5 mph for five minutes to warm up
• Interval 2: 3.8 mph for three minutes
• Interval 3: 3.5 mph for one minute (active rest)
• Interval 4: 3.8 mph for three minutes
• Interval 5: 3.5 mph for one more minute, and so on until you reach 30 minutes.

As you can see, the ratio changed from 1:3 to 3:1 (work to active rest). The next step would be to do all four minutes at 3.8 mph (the new active rest) and increase the work interval for one minute to 4.0 mph.

One final note. Spin class is interval training. It's done at gyms on special spin cycles with an instructor who barks out orders to increase the intensity and then slow down to catch your breath. It's addictive, and people who do it regularly swear by it. You should already be doing some aerobic exercise and be reasonably conditioned before you try it, but I recommend it if you're looking for one of the toughest workouts around.

Heart rate training

You can get more specific with your aerobic interval training and use heart rate since it's an excellent indication of how hard you are working. Let's use jogging on a treadmill as the aerobic activity in this example. For example, if your heart rate is at 70% of your predicted maximum when you jog at 6 mph, then start at that speed and either increase the speed or elevation so that your heart rate increases to 85% or even 90% for one minute, then back to your usual jogging speed for three minutes to elicit a heart rate of 70%. Start with a 1:3 work:active-rest ratio. That's a good starting point, and as you increase the work intervals and decrease the active-rest ratios like in the examples above, you'll notice that your conditioning improves so that your heart rate will be lower at higher speeds.

It's a good idea to plan your intervals. Write them down so that you don't have to think about them while you're working out. I also suggest intervals no more than one to two times per week because they are tough workouts and you will need some time to recover. It's okay to do aerobic activity on days in between your intervals, but give your body a chance to recover from the intervals before doing them again.

Increasing duration and intensity

The general rule for increasing aerobic activity is 10% per week. Interestingly, there's no evidence to suggest that a 10% increase is the safest and most effective amount of time to increase, but that's the rule of thumb and it seems to work pretty well. So, if you're walking for 20 minutes, then the next increase ought to be two minutes for the following week. The bottom line though is to listen to your body. If you find that increasing by 10% is very easy, then go ahead and try a little more. But if you find that you are tired for hours after your workout, or chronically sore or achy from your workouts, then you know you need to cut back to 10% increases. Learn how to listen to your body and everything should be OK.

High-intensity interval training

High-intensity interval training (HIIT) is an aerobic exercise that consists of short bursts of intense activity followed by intervals of lower-intensity exercise or rest. When compared to typical steady-state cardio, HIIT is far more effective in improving cardiovascular fitness, burning calories, and increasing overall endurance in less time.

Common HIIT aerobic exercises include:

Jumping jacks

• Begin with your feet together and arms at your sides.
• Jump up, spread your legs, and raise your arms high.
• Jump again to return to your starting position.

Burpees

• Begin in a standing position and squat down, placing your hands on the floor.
• Jump your feet back into a plank position, then do a push-up.
• Return your feet to your hands, and jump up with arms raised.

High knees

Run in place, raising your knees as high as possible, aiming to reach waist level.

Mountain climbers

• Start in a plank position.
• Bring one knee to your chest and quickly switch legs to simulate a running action while on a plank.

Engaging in a 10-minute aerobic exercise routine can be a convenient and flexible way to meet the CDC's recommendations for physical activity. The CDC emphasizes that adults should aim for 150 minutes of moderate-intensity activity each week, 75 minutes of vigorous-intensity activity, or a combination of the two, spread throughout the week. This could mean 30 minutes (or three sessions of at least 10 minutes each) per day for five days a week.

Here is a sample 10-minute aerobic exercise routine that aligns with CDC guidelines:

• Warm-up (two minutes): To get your body ready for exercise, begin with a brief warm-up. For around two minutes, you can do arm circles, light stretches, or stationary walking.
• Cardiovascular workout (six minutes): Pick a cardiovascular workout that you find enjoyable and are capable of doing at a moderate to intense level. You can choose to jog in place, do jumping jacks, dance, or walk quickly. For six minutes, focus on increasing your breathing and heart rate while performing the selected activity.
• Cool-down (two minutes): After your aerobic workout, take two minutes to relax your body and gradually reduce your heart rate to avoid feeling lightheaded or uncomfortable. Spend around two minutes gently stretching the main muscular groups in your body, including your hamstrings, quadriceps, calves, chest, and shoulders.

This routine is a combination of a warm-up, cardiovascular activity, and cool-down to offer a well-rounded 10-minute aerobic workout. It is important that you pay attention to your body, modify the intensity as necessary, and speak with a healthcare provider, particularly if you have any underlying health issues.

The significance of a 10-minute aerobic exercise lies in its ease and flexibility to fit into a hectic schedule, making it simpler to maintain continuity and incorporate physical activity into everyday life. Regular involvement in such routines can result in improved endurance, weight management, and mental health, demonstrating that even brief periods of exercise can have major health benefits. Various studies provide evidence that exercising for brief periods may enhance your fitness, even if you are not already active.

The most effective aerobic exercise plan varies from person to person, depending on their health, age, goals, and interests. Therefore, it's important to try different options until you find the one that suits you best. An aerobic training program includes a combination of moderate to high-intensity cardio, such as jogging, swimming, or cycling, and strength training exercises.

For example, a beginner could start with 20-30 minutes of brisk walking three times per week, gradually increasing the intensity and frequency of their workouts. At the same time, weight training exercises can be done two to three times per week.

It is recommended that you adhere to the CDC guidelines, which call for at least 150 minutes of moderate-intensity or 75 minutes of vigorous aerobic physical exercise every week. Both levels of intensity help meet aerobic exercise goals. Intensity refers to how hard your body works during these activities. One thing to remember is that one minute of vigorous-intensity activity is equivalent to two minutes of moderate-intensity activity.

Examples of moderate-intensity exercises:

• Brisk walking
• Water aerobics
• Bicycling slower than 10 miles per hour
• Playing doubles tennis

Examples of vigorous-intensity exercises:

• Jogging or running
• Swimming laps
• Bicycling 10 miles per hour or faster
• Playing singles tennis

Step, funk-fusion, hip-hop, jazz, kickbox, boot camp, cardio box...There are dozens of classes to choose from. They last anywhere from 30 to 60 minutes and vary in intensity.

Here's some advice for choosing classes:

1. Classes are generally rated as beginner, intermediate, and advanced. Choose the level that fits your condition. It's no fun taking an advanced class if you're a beginner. It will be hard and frustrating and you won't enjoy the experience. Watch the class or speak with the instructor to help you decide what's right for you. Sometimes it comes down to the class time that fits your schedule, but just be sure to not get in too far over your head.
2. Low-impact classes mean that one foot always stays on the ground. They are less intense than high-impact and may be more suitable if you are a beginner. Some classes are now called, "high-low" or "mixed-impact," which means they combine low and high-impact moves. Again, speak with the instructor if you're not sure.
3. High impact means both feet leave the ground, so there will be jumping and balance moves. Stick with lower-impact and more gentle and rhythmic dance classes if you are concerned about the pounding (low back problems, knee arthritis, or other joint injuries).
4. Experiment until you find the classes that work best for you.

Classes are great for people who like to exercise with others, who like to dance, who like music and rhythm, who want the extra motivation and energy that an instructor and class provide, and who prefer the structure and schedule of a regular class. Classes, equipment, and videos are all great ways to stay fit and healthy, but if you're limited by injury or other conditions, then aerobic exercise chair workouts may be just the thing (see resources for online vendors). The instructor leads you through a workout in a chair and it's great exercise. You might not need chair exercise, but you may have a parent or friend who does. Exercise videos and DVDs make great gifts!

The bottom line to equipment, classes, and videos is that if they get your heart rate elevated and keep it there, then it's aerobic and it counts!

That's it!

There you have it. Aerobic exercise is awesome stuff! It strengthens your heart, adds strength to your muscles, makes them more efficient fuel burners, increases your endurance and your energy, improves your mood, makes you fit and healthy, and much, much more. Is 30 minutes of aerobic exercise enough? It could take as little as 30 minutes out of your day for a tremendous payoff, so I suggest giving it a shot. Follow my advice for getting started by doing only what is realistic and building up slowly. You have only health and fitness to gain, and you're worth it! Good luck!

The activity you choose is a personal choice and it varies for everyone, so you need to experiment until you find what works best for you.

Here are 7 possible types of workouts at home:

1. Rowers, treadmills, bikes, and cross-country skiers are all effective if you use them.
2. There is some suggestion that some individuals are more inclined to exercise at home with equipment than at the gym or a class.
3. Some individuals prefer to go to the gym while others are perfectly content to work out at home on their equipment in front of their TV. TV can make time pass quickly, and so can your favorite movie, music, scholarly courses taught by professors, or books on tape (see resources for online vendors).
4. Finding something that will distract you might just make that 30-minute workout bearable, and believe it or not you might even look forward to it! After all, it could be the only 30 minutes in your day that you have all to yourself. Indulge!
5. Aerobic exercise videos and DVDs are also effective if you use them! They are convenient if you prefer to work out at home instead of taking a class at a studio or a gym, and there are hundreds to choose from. I suggest that you check out Collage Video (http://www.CollageVideo.com), or give them a call and ask for a recommendation.
6. Also, check if your local library rents exercise videos on tape or DVD. And by the way, there are videos for all types of activity; from weight training to tai-chi, to stretching.
7. Check out all the possibilities to add flexibility and strength training to your cardio workout.

My suggestion for getting started with an exercise program is almost always the same. Keep it simple, keep it practical, keep it convenient, keep it realistic, keep it specific, and don't try to make up for years of inactivity all at once. Select any activity and amount of time where the probability of sticking with it is high. You may not love walking, but if you can do it right outside your door, it requires no special equipment, and you already know how to do it (you've been walking your entire life!), then walking might be your best bet for getting started because it's so convenient.

What I mean by "be specific" pertains to setting exercise plans. Planning is helpful for behavior change, and I suggest that you set goals each week. I suggest writing down what day(s) of the week you'll exercise, what time of day, minutes of activity, location, and the activity that you'll do. Be as specific and realistic as possible, and remember that it's not how much you do when you get started but that you simply get started (getting started is usually the hardest part).

A sample plan might look like this:

• Monday: Take a 20-minute brisk walk at 7 a.m. around the block four times.
• Tuesday: Do the same as on Monday.
• Wednesday: Take a 20-minute walk at 6:30 p.m. (right before dinner) around the block.
• Thursday: Take the day off.
• Friday: Take a 20-minute walk at 7 a.m. around the block.
• Saturday: Walk with your family at 10 a.m. for 45 minutes in the park.
• Sunday: Bike ride with your spouse for 60 minutes in the park at noon. Mom will babysit.

Another plan I like is the five-minute out, five-minute back plan. Just like it sounds, you walk for five minutes from your starting point, turn around, and walk back. It's simple and doable for almost everyone. It's a change in your activity behavior even though it's not all that much, and you can increase as you get more used to it. From five minutes you could go to seven and a half out, seven and a half back, a total of 15 minutes just like that. And you can keep your eye on 15 out, 15 back, and there you go meeting the Surgeon General's recommendation of 30 minutes. If you're feeling ambitious, you can add some abdominal crunches and push-ups once you get back.

For push-ups, if you can't do a standard one on the floor, modify them by leaning against a wall, leaning against a table, or on your knees on the floor. The slower you go the harder they are. Start with two to three sets of crunches and push-ups, 12-15 repetitions, three to four days a week. As they get easier, you can increase the intensity of crunches by going slower or putting your legs in the air with your knees bent. As push-ups get easier, you can go to the next lower level (for example, from wall to table to on your knees on the floor).

I suggest keeping records of your weekly progress by writing down what happens, or at least checking off that you followed through, and then setting your weekly plan every week for at least three months. Then at three months, you can evaluate your progress and see if any changes need to be made. How will you know if you're ready to stop setting weekly goals each week? Ask yourself if you believe you will be exercising regularly in six months. If the answer is "I'm not sure," or "no," then you ought to continue to set weekly goals. If you are confident that you can maintain the behavior and will be exercising in six months, then you may not need to set weekly goals, but at the first sign of slipping, you ought to go back to it.

How our bodies adapt

Here's what happens inside your body when you do aerobic exercise regularly:

1. Your heart gets stronger and pumps more blood with each beat (larger stroke volume). Elite athletes, as I just mentioned, can have stroke volumes more than twice as high as average individuals. But it's not just that. Conditioned hearts also have greater diameter and mass (the heart's a muscle too and gets bigger when you train it), and they pump efficiently enough to allow for greater filling time, which is a good thing because it means that more blood fills the chambers of the heart before they pump so that more blood gets pumped with each beat.
2. Greater stroke volume means the heart doesn't have to pump as fast to meet the demands of exercise. Fewer beats and more stroke volume mean greater efficiency. Think about a pump emptying water from a flooded basement. The pump works better and lasts longer if it can pump larger volumes of water with each cycle than if it has to pump faster and under more strain to get rid of the water. High stroke volume is why athletes' hearts don't pump as fast during exercise and why they have such low resting heart rates; sometimes as low as 40 beats per minute, whereas the average is 60-80 beats per minute.
3. Downstream from the heart are your muscles, which get more efficient at consuming oxygen when you do regular aerobic exercise (remember, "consuming" oxygen means that the muscles are taking the oxygen out of the blood). This happens because of an increase in the activity and number of enzymes that transport oxygen out of the bloodstream and into the muscle. Imagine 100 oxygen molecules circulating past a muscle. You're twice as fit if the muscle can consume all 100 molecules than if it can only consume 50. Another way of saying it is that you're twice as fit as someone if your VO₂ max is 60ml/kg/min. and theirs is 30ml/kg/min. In terms of performance in this scenario, you'll have more endurance because your muscles won't run out of oxygen as quickly.
4. Mitochondria inside the muscle increase in number and activity. Mitochondria are the powerhouses of your cells. They do all the heavy-duty work to keep you moving. They use oxygen to burn the fat and carbohydrate that makes you go. The good news is that they increase in number and activity, by as much as 50%, in just a matter of days to weeks in response to regular aerobic exercise in adults of all ages.

Burn, baby, burn

I mentioned that fat and carbohydrates are the fuels our muscles burn. The difference between them is that fat is high-test; it contains 9 calories per gram whereas carbohydrate has only 4, so you get more energy and can go farther on a gram of fat than on a gram of carbohydrate.

You want to burn fat because it's such an efficient fuel, plus it's nice to lose some of your excess fat! The catch is that you need more oxygen to burn fat because it's denser than carbohydrates. The good news is that your body gets better at using oxygen and burning fat when you do regular aerobic exercise; as I described, your heart pumps more blood, your muscles consume more oxygen, and you have more mitochondria.

Aerobic exercise burns lots of calories. Below is a table of minutes of continuous activity necessary to expend 300 calories based on your body weight and different exercise types.

Heart rate reserve

Your heart rate rises during aerobic exercise. It can rise from 70 beats per minute (bpm) at rest to as high as 170 bpm or even higher during exercise, depending on the intensity of the exercise, your fitness level, your age, and other factors. Whether your training is aerobic or anaerobic is determined by the intensity of your workout, and monitoring the intensity is the key to knowing which one you're doing.

For many individuals, simply monitoring how the body feels while exercising is enough to determine the proper aerobic intensity. I recommend "warm and slightly out of breath" as the cue for aerobic activity; that is if you feel warm and slightly out of breath while you're exercising, then that's good enough.

On the other hand, some people like to know with more precision how their body is doing during exercise. If that's the case for you, then taking your heart rate during exercise and using a target heart rate training zone might be just the ticket.

• Target heart rate zones range anywhere from 50% to 100% of your maximum heart rate (your maximum heart rate is based on your age).
• Aerobic exercise is anything less than 85%, and anaerobic exercise is anything above that.
• A nice starting point for a sedentary individual is somewhere in the range of 50% to 65% (you can always increase as you get more fit) and 65% to 85% for more conditioned individuals.

I recommend the heart-rate reserve method for calculating a target heart rate. Here are the formula and an example of the method for someone 27 years of age, assuming a resting heart rate of 70 bpm, and a training range of 70%. If you plug in other values, you can get other ranges.

Here's the heart rate reserve formula:

• Max HR = 220 - Age 
• Heart Rate Reserve (HRR) = Max HR - resting heart rate 
• Training Heart Rate = HRR x percent at which you want to train
• Target Heart Rate = Training Heart Rate + resting heart rate

Assuming a resting heart rate of 70 bpm, 27 years old, and 70% training range:

• Max HR = 220 - 27 = 193
• Heart Rate Reserve (HRR) = 193 - 70 = 123
• Training Heart Rate = 123 x .70% = 86
• Target Heart Rate = 86 + 70 = 156

So this 27-year-old exerciser will try to maintain a target heart rate of 156 beats per minute while doing aerobic exercise.

Please note: There's been some recent research to suggest a new way of estimating maximum heart rate. The formula is the following:

1. Multiply 0.7 times your age.
2. Subtract that number from 208.

An example if you're 26 years old is: 0.7 x 26 = 18, then the Max HR is 208 - 18 = 190. You'd then take the Max HR of 190 and plug it in as usual to the formula above. This new formula makes a slightly bigger difference as you get older.

You can read a complete review of heart rate training zones.

Aerobic vs. anaerobic exercises

According to the NIH, aerobic exercise refers to activities that primarily use oxygen to produce energy for sustained periods. These exercises typically involve moderate-intensity activities performed over an extended period and they rely on continuous oxygen intake to fuel muscular activity. Aerobic exercise primarily targets the cardiovascular system, improving heart and lung function, and increasing endurance over time. Aerobic exercise has numerous health benefits, including improved cardiovascular health, reduced risk of chronic diseases such as heart disease and diabetes, weight management, and enhanced mood and mental well-being.

Examples of aerobic exercises:

• Running/jogging
• Swimming
• Cycling
• Brisk walking
• Dancing
• Rowing
• Hiking
• Jumping rope (moderate pace)
• Skiing
• Stair climbing
• In-line skating
• Tennis (doubles)

Anaerobic exercises involve short bursts of intense physical activity performed without relying on oxygen for energy production. These activities require high levels of power and strength. Anaerobic exercise primarily targets muscle strength, power, and hypertrophy (muscle growth), rather than cardiovascular endurance. They may lead to improvements in muscle mass, strength, and power, as well as enhanced metabolism and fat loss, especially when combined with aerobic exercise and proper nutrition.

Examples of anaerobic exercises:

• Sprinting: Short, quick runs of no more than 100 meters
• Strength training and weightlifting: Exercises that use heavy weights and few repetitions such as bench presses, deadlifts, and bicep curls
• High-intensity interval training (HIIT): Short bursts of intense exercise (such as burpees or mountain climbers) followed by rest or low-intensity periods
• Calisthenics: Intense exercises such as jump squats, box jumps, and plyo push-ups
• Jumping rope: Short periods of intense and fast-paced jumping
• Hill sprints: Uphill sprinting for a short distance but with maximum effort
• Isometric exercises: Holding body still under tension, such as planks and wall sits
• Resistance band exercises: Sprints or resisted squats done with resistance bands
• Bodyweight exercises: Push-ups, pull-ups, and dips performed quickly or with added resistance
• Agility drills: Quick movements requiring sudden direction changes, such as cone drills or ladder drills

It’s important to note that a complete fitness program must include both anaerobic and aerobic workouts. The CDC recommends an average of 150 minutes of moderate activity each week, along with two or more days of strength training (or anaerobic exercise).

Anaerobic exercise concentrates on muscle strength, power, and hypertrophy, whereas aerobic exercise concentrates on cardiovascular health and endurance. Including both forms of exercise in your regimen can have a positive impact on your overall fitness and health.

To maximize the benefits of anaerobic exercises, it's important to engage in high-intensity workouts with short recovery periods between sessions. Maintain proper technique and adhere to a consistent exercise routine. Additionally, follow a balanced diet rich in proteins, carbohydrates, and healthy fats, and stay hydrated to fuel your workouts effectively. Avoid overtraining and make necessary adjustments to sustain your exercise regimen.

Diabetes

No study has been more conclusive about the role of healthy lifestyle changes (diet and exercise) in preventing diabetes than the Diabetes Prevention Program. It was a study of more than 3,000 individuals at high risk for diabetes who lost 12-15 pounds and walked 150 minutes per week (five 30-minute walks per day) for three years. They reduced their risk of diabetes by 58%. That's significant considering there are 1 million new cases of diabetes diagnosed each year. Aerobic exercise can also improve insulin resistance. Insulin resistance is a condition in which the body doesn't use insulin properly, and this condition can occur in individuals who do and do not have diabetes. Insulin is a hormone that helps the cells in the body convert glucose (sugar) to energy.

Many studies have shown the positive effects of exercise on insulin resistance. In one, 28 obese postmenopausal women with type 2 diabetes did aerobic exercise for 16 weeks, three times per week, for 45-60 minutes, and their insulin sensitivity improved by 20%.

Cardiovascular disease

The list of studies that show that aerobic exercise prevents or reduces the occurrence of cardiovascular disease is so long that it would take this entire article and probably five others just like it to review all of the research. One of the most important is one of the earliest. In a study of more than 13,000 men and women, it was shown that the least fit individuals had much higher rates of cardiovascular disease than fit individuals -- in some cases, the risk was twice as high. Aerobic exercise works in many ways to prevent heart disease; two of the most important are by reducing blood pressure and allowing blood vessels to be more compliant (more compliant means that they become less stiff and it's less likely for fat to accumulate and clog up the vessels). Results like these have been proven over and over again.

Obesity and weight control

Aerobic exercise is believed by many scientists to be the single best predictor of weight maintenance. You can lose weight without exercise by reducing your caloric intake enough so that you burn more calories than you consume, but it takes a regular dose of exercise to keep your weight off. How much is not clear, but somewhere between 30 and 40 minutes of vigorous exercise several times per week, to 45 to 75 minutes of moderate-intensity exercise five or more days per week is probably about right. Your mileage will vary, and so once you get to the weight that you want to be at you'll need to experiment with different amounts of exercise until you find the one that works for you.

The American College of Sports Medicine recommends that overweight and obese individuals progressively increase to a minimum of 150 minutes of moderate-intensity physical activity per week, but for long-term weight loss, overweight and obese adults should eventually progress to 200 to 300 minutes per week of moderate-intensity physical activity. These are general guidelines, and so again, you need to experiment to see what works for you.

Scientists have recently become interested in the effects of aerobic exercise on cognitive function. It has been shown in rats that the use of a running wheel every day stimulates new brain cells to grow in as few as 12 days. Brain cells in humans can't be studied directly, but what has been shown is that rates of dementia and Alzheimer's disease are lower in older individuals who exercise three or more times per week compared with older adults who exercise fewer than three times per week. In some cases, the risk is 62% lower. Evidence is also accumulating that active individuals perform better on cognitive function tests such as tests of memory and spatial relations than sedentary individuals.

Perhaps no area of exercise science has been more studied than the benefits of aerobic exercise. There is a mountain of evidence to prove that regular aerobic exercise will improve your health, your fitness, and much more. Here's a partial list of the documented health benefits of aerobic exercise.

Cancer prevention

Research is clear that physically active men and women have about a 30%-40% reduction in the risk of developing colon cancer compared with inactive individuals. It appears that 30-60 minutes per day of moderate- to vigorous-intensity physical activity is needed to decrease the risk, and there is a dose-response relationship, which means that the risk declines the more active you are. There is reasonably clear evidence that physically active women have a greater reduction in risk of breast cancer compared with inactive women. Like colon cancer, it appears that 75 to 150 minutes per day of moderate- to high-intensity physical activity is needed to decrease the risk, and there is likely a dose-response relationship as well. Research is inconsistent regarding whether physical activity plays any role in the prevention of prostate cancer. There are relatively few studies on physical activity and lung cancer prevention. The available data suggest that physically active individuals have a lower risk of lung cancer; however, it is difficult to completely account for the risks of active and passive cigarette smoking as well as radon exposure. There is little information on the role of physical activity in preventing other cancers.

Cancer treatment

There's some good news for people undergoing cancer treatment. In one study, aerobic exercise performed five days per week for 30-35 minutes for six weeks at 80% of maximal heart rate reduced fatigue in women being treated for cancer. In another study, 10 weeks of aerobic exercise at 60% of maximum heart rate for 30-40 minutes, four days per week, reduced depression and anxiety in female cancer patients. Aerobic exercise isn't a panacea when it comes to cancer, but evidence suggests that it certainly can help.

Osteoporosis

Osteoporosis is a disease characterized by low bone density, which can lead to an increased risk of fracture. The good news is that exercise may increase bone density or at least slow the rate of decrease in both men and women. It may not work for everyone, and the precise amount and type of exercise necessary to accrue benefits are unknown, but there is evidence that it can help. In children, there is good news, too. It seems that active children have greater bone density than sedentary children and that this may help prevent fractures later in life.

Depression

Most of us who exercise regularly understand that exercise can elevate our mood. There have been several studies investigating the effects of exercise on depression. In one of the most recent studies, it was shown that three to five days per week for 12 weeks of biking or treadmill for approximately 30 minutes per workout reduced scores on a depression questionnaire by 47%. It's not a substitute for therapy in a depression that causes someone to be unable to function (in which case medication and/or psychotherapy may be necessary), but for milder forms of depression, the evidence is persuasive that it can help.

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