Exercise

Exercise Related Articles

Exercise Facts

Exercise isn't a new idea. Records of people exercising go back to 1100 B.C., when the Greeks competed in the javelin throw, distance running, archery, and boxing. Hippocrates (460 B.C.-377 B.C.), the father of medicine, wrote that "eating alone will not keep a man well; he must also take exercise." Milo of Croton, in 6 B.C., discovered the Principle of Progressive Overload, in which he carried a calf every day on his shoulders and as it grew into a bull and got heavier, he got stronger (just like adding heavier dumbbells).

Skip ahead a thousand years to 1844, when the YMCA was founded and people started to do more formal exercise. Then, in 1896, the first modern Olympic games began, and by the early 1900s, gymnastics was mandatory for all American school children. In the late 1950s, things really picked up; Jack LaLanne had an exercise show on TV; the President's Council on Physical Fitness was created; in the 1960s and '70s, Jackie Sorensen and Jane Fonda produced exercise videos, Nautilus, Inc. (maker of fitness equipment), was founded in the 1980s; Ken Cooper coined the word "aerobics," and a running phenomenon was started by George Sheehan, Jim Fixx, and others. Today, we have limitless types of exercise classes, technology built into every cardio machine, and all sorts of contraptions for building muscles. In this article, we'll take a more in-depth look at what exercise is all about.

The Benefits of Regular Exercise

Physical Fitness

Physical fitness is a measure of the condition of the body to perform during activities of daily living (light, moderate, and strenuous), formal exercise (like when you work out), and emergencies (as when you must escape from danger like a fire). The physical fitness of our nation is declining, proved by the rising rates of obesity, diabetes, some types of cardiovascular disease, and other medical conditions. To improve physical fitness, one must "practice," or work out. Emphasis should be on improving aerobic conditioning (stamina or endurance), muscular strength and endurance, and flexibility. The types of exercise necessary to do this are described next.

Types of Exercise

Types, or modalities, of exercise fall into three major groups: aerobic, anaerobic, and flexibility. Here's a description of each.

Aerobic Exercise

Aerobic means "with oxygen." Aerobic exercise is performed at an intensity that causes you to feel "warm and slightly out of breath." Examples are swimming, dancing, jogging, brisk walking, rowing, and all the cardio machines in your gym. These can be done anaerobically as well by increasing the intensity (see more about anaerobic exercise below).

Aerobic exercise burns more fat than anaerobic exercise. That's because fat has more calories per gram than carbohydrate (9 vs. 4) and because it's so dense it needs more oxygen to burn it for fuel in the muscle. In order to get more oxygen to burn fat, you need to exercise moderately so there is time to bring in large volumes of oxygen. If you sprint or lift weights in short bursts, there's no time to bring in lots of oxygen, so the primary fuel is carbohydrate.

Anaerobic Exercise

Anaerobic exercise is working out at an intensity that gets you out of breath and sweaty. Typically, it's performed in brief spurts like a set of lifting weights or a sprint. Games like basketball or soccer have large components of anaerobic exercise because of the sprinting, but a long-endurance event might too when you hit the hills or sprint at the finish line.

Flexibility Exercises

There are no specific guidelines as to how much to stretch. It feels good, and so I recommend stretching as often as you like. Most people tend to sit most of the day, and so I recommend getting up every so often and taking a good stretch. I guarantee you'll feel better. Stretch your neck, or maybe do some side bends, or even bend forward and touch your toes. Whatever it is, listen to your body and stretch until you feel better.

Proper technique for stretching is to push into the stretch until you feel mild tension, hold until you feel looser, then push a little more. The key point is to hold until you feel looser. So, listen to your body and stretch until you feel looser.

Stretch and tone classes are popular for a reason. They feel good and you get results. Yoga is another great way to stretch, plus, it's meditative and stress reducing. Start with a beginner class if you're new at it. Your muscles will know after your first session that you did something.

When your body feels limber, you feel more connected to it. Muscles communicate with the pleasure and sensation centers in your brain. When muscles feel relaxed, you feel that way, too. There's a limited amount of research to prove this, but ask 100 people who stretch if it's true, and they will tell you it is. Does stretching prevent injury? There's very little research to prove it. I recommend calf stretching to treat conditions like plantar fasciitis (pain in the heel), and gentle stretches for rehabilitation after muscle pulls and strains but only after it starts healing. As for prevention, there's no downside to keeping muscles loose, and it feels good, so why not? And if it does happen to prevent injury, then it's a bonus.

The very best way to stretch, particularly if you're doing cardio and working your legs, is to warm up for five to 10 minutes to get the muscles filled with blood and warm. Then stop your cardio and stretch. You'll notice the difference compared with a cold stretch right away. When I coached fencers, I always had them start practice with a 1-2 mile jog and then stretch. Fencers need lots of flexibility, and I didn't want any of my athletes pulling muscles. An excellent resource for flexibility exercises is Bob Anderson's book or DVD titled Stretching.

Burning Fat and Carbohydrate With Aerobic Exercise

At rest, you burn just about equal amounts of carbohydrate and fat. If you were to get up and move quickly and get slightly breathless, then the percentage of fat burned would drop because it takes more oxygen to burn a gram of fat than carbs since fat has more calories than carbs (9 per gram compared with 4 per gram for carbs). At lower intensities of aerobic exercise, you burn more fat than carbohydrate. At higher intensities of anaerobic exercise, you burn more carbs since you're more breathless and can't deliver enough oxygen to the muscles to burn more fat (carbs are fast-acting fuel). However, don't get misled into thinking burning more fat means burning more calories. For example, if you jog for 30 minutes at 6 mph (3 miles) and you weigh 150 pounds, you'll burn 300 calories. But if you run at 8 mph for 30 minutes (4 miles) you'll burn 400 calories. You may burn a higher percentage of fat at the slower speed, but you burn fewer total calories. And if you're looking for weight loss, you're looking to burn the most calories you can. Plus, at the higher speed, you get fitter. You know the cardio and fat burning settings on the treadmill? Forget about it. Don't go at the slower fat-burning speed if you want to burn more calories and get more fit. The fat burning will happen at either intensity. Get more fit.

Aerobic Exercise Guidelines

The aerobic exercise guidelines for health and fitness from the American College of Sports Medicine (ACSM) is to do 20-60 minutes of continuous vigorous activity (large muscle groups moving rhythmically) three to five times a week at 60%-90% of max heart rate. Examples are cycling, walking, jogging, swimming, dancing, rowing, and others. An important addition to these guidelines is the "lifestyle activity" guideline suggested by the Surgeon General in the 1996 government report "Physical Activity and Health." The recommendation in the report is to accumulate 30 minutes of moderate-intensity physical activity on most, if not all, days of the week. Accumulate means you can meet the guideline in two bouts of 15 minutes, three bouts of 10 minutes, or one bout of 30 minutes. The guideline is intended to make it easier for people to incorporate exercise into their activities of daily living instead of taking the time to do more formal workouts (like working out at the gym or jogging in the park).

Calculating Heart Rate Training Zone

Heart-rate training involves calculating a high and low heart rate and working out in between the two numbers to maximize fitness benefits. You can start your workout at the lower part of the range, and as you get fit, you can gradually increase the intensity. I recommend the heart-rate reserve method for calculating a target heart rate. Here's the formula. If you plug in other values, you can get other ranges.

  1. 220-Age = Max HR
  2. Subtract resting heart rate from Max HR = Heart Rate Reserve (HRR).
  3. Multiply HRR to the percent at which you want to train.
  4. Add back resting heart rate.

Here's an example. Assuming a resting heart rate of 70 bpm, 27 years of age, and a 70% training range (60%-85% is the normal training range):

  1. 220 - 27 = 193
  2. 193 - 70 = 123
  3. 123 x .70 = 86
  4. 86 + 70 = 156

The Rating of Perceived Exertion Scale (RPE)

Another way to measure exercise intensity is to use the Borg Scale of Perceived Exertion (RPE). It's a simple way to measure intensity, which cues you to listen to your body. To use it, select the number from the scale below that best describes your level of exertion. Ask yourself, "How hard does the work feel?" Pay attention to your overall level of fitness and then rank it. RPE #13 is equivalent to a heart rate of approximately 60%-75% of heart-rate reserve and where you can train to improve your fitness and health.

  • 6 No exertion at all
  • 7
  • 7.5 Extremely light
  • 8
  • 9 Very light
  • 10
  • 11 Light
  • 12
  • 13 Somewhat hard
  • 14
  • 15 Hard
  • 16
  • 17 Very hard
  • 18
  • 19 Extremely hard

Why Is Exercise Important?

The list of exercise benefits goes on and on. Without going into all the details, below is a list of exercise benefits, all backed by research to support every claim.

What's the Best Time to Exercise?

There isn't a best time to exercise. An exception might be if you exercise when you are tired and can't put 100% into your workouts. That could be late afternoon or late evening. But there has never been a study to prove that you get more benefit at one time of day compared with another.

How to Get Started if You're New to Exercising

Below are a few different routines for getting started with aerobic exercise. Walking is the most popular activity in the country and so it's featured in these routines.

  1. The simplest is the five-minutes out, five-minutes back plan by Mark Fenton. Just like it sounds, you walk out for five minutes, turn around and walk back. That's it, and off you go about your day. When you can do that easily enough, then go ahead and add two and a half minutes so that it's seven and a half out, seven and a half back, and on to 10 and then 15 minutes for a 30-minute walk. You can do this with outdoor biking as well, using 10-15 minutes out as the starting point.
  2. Below is a sure-fire weekly walking plan to get you fit. Work up to any time-limit you like.
Week Warm-Up Time Brisk Walk Time Cool-Down Time Total Time (min)
1 walk slowly 5 min walk briskly 5 min walk slowly 5 min 15
2 walk slowly 5 min walk briskly 8 min walk slowly 5 min 18
3 walk slowly 5 min walk briskly 11 min walk slowly 5 min 21
4 walk slowly 5 min walk briskly 14 min walk slowly 5 min 24
5 walk slowly 5 min walk briskly 17 min walk slowly 5 min 27
6 walk slowly 5 min walk briskly 20 min walk slowly 5 min 30
7 walk slowly 5 min walk briskly 23 min walk slowly 5 min 33
8 walk slowly 5 min walk briskly 26 min walk slowly 5 min 36
9 walk slowly 5 min walk briskly 29 min walk slowly 5 min 39
10 walk slowly 5 min walk briskly 33 min walk slowly 5 min 43
11 walk slowly 5 min walk briskly 37 min walk slowly 5 min 47
12 walk slowly 5 min walk briskly 42 min walk slowly 5 min 52
13 walk slowly 5 min walk briskly 47 min walk slowly 5 min 57
14 walk slowly 5 min walk briskly 53 min walk slowly 5 min 63
15 walk slowly 5 min walk briskly 60 min walk slowly 5 min 70

Walk three to five times per week. If you drop below three times per week, then keep the total Brisk-Walk-Time the same as the previous week. Walking briskly means you feel somewhere between "warm and slightly out of breath" to "out of breath and sweaty."

Check out the following sites for training programs for walking and running:

http://www.coolrunning.com/index.shtml (The site has a "Couch-to-5K Running Plan," which is a great way to get started.)

http://www.halhigdon.com

http://www.jeffgalloway.com/

http://www.runnersworld.com/home/ (Click on "training plans" in the left margin.)

Interval Training

Interval training (IT), also known as speed training or speed work, is a method of cardio training in which you combine aerobic and anaerobic training. The way it works is that you work out at your normal pace for a few minutes (after a proper warm-up), and then you increase the pace for a minute or two at periodic intervals. Take running as an example. You run at your normal pace of 6 mph for three minutes, then increase to 6.5 mph for one minute, then back to 6 mph for three minutes, then back to 7 mph, and so on, continuing this for the duration of your workout. As you get more fit, you decrease the rest time and increase the work time. These periodic changes are known as "work to active-recovery ratios" (written as work: active recovery).

You can get more specific and use your heart rate to monitor your intervals. Heart rate is an excellent indication of how hard you're working. For example, if your heart rate is at 70% of your predicted max when you jog at 6 mph, then start at that speed for three minutes, then increase the speed (or elevation on the treadmill) so that your heart rate increases to 85% or even 90% for one minute, then go back to jogging at 6 mph, or 70% of heart-rate reserve.

A ratio of 1:3, or work to active-recovery, is a good starting point. As you get more fit, you can increase the work and decrease the active-recovery in 30-second increments so that the ratio becomes 2:2. Research clearly shows that fitness improves quickly and substantially with interval training. And there's more research to show that you may be able to get as fit with intervals as you can with traditional aerobic training in less than half the time. Give intervals a try. They get you fit, and they can help you break through a weight-loss plateau as well.

Resistance Exercise

Resistance exercise is any exercise that causes muscles to contract against external resistance. It could be weight-lifting machines, free weights (for example, dumbbells), resistance bands, or even your body weight (pushups, pull-ups, etc.). ACSM guidelines for resistance exercise are to do one set of eight to 10 exercises that condition the major muscle groups, two to three days per week, eight to 12 repetitions of each exercise; 10-15 repetitions may be more appropriate for older and frailer people, and multiple-set regimens may provide greater benefits if time allows. Research shows that beginners can get stronger with just one set of each exercise, but then after three to four months, you'll probably need to increase the number of sets to get stronger since your strength will plateau and your muscles will need a greater stimulus to improve.

Free Weights vs. Machines

Both of these work, and I recommend a combination to maximize your workout. Here are the advantages of the two:

Free weights:

  • More versatile so you can do more exercises with them
  • Challenge your balance since you must control the weights
  • Less expensive than machines

Machines:

  • Safe for beginners who might not have the coordination or experience to work with free weights on their own
  • Are efficient because all you need to do is put the pin in the weight stack to get your resistance
  • Permit you to do certain exercises more easily and safely than with free weights (for example, cable rows compared with bent-over rows, pull-downs compared with a pull-over)

Bodybuilders use both, and if it's good enough for them, then it ought to be good enough for you. I recommend at the very least using the cable row or rowing machine and the cable crossover. The cable crossover is great because it allows you to do many of the exercises you can do with free weights without lots of different dumbbells, plus the cables have a smooth action that feels great. Ask a trainer at your gym to show you the different exercises you can do with it if you don't know how.

Here are the potential down sides to free weights:

  • You need lots of them to get a thorough workout if you want to work out at home.
  • You could drop one.

Here are the potential downside to machines:

  • Not all machines fit all body types. Ask a trainer to make sure the machine is set properly for you (seat adjustment and arm adjustment if available).
  • The range of motion is set and may not fit your anatomy. For instance, the biceps machine where the handles do not rotate can cause considerable stress on the elbow. The same goes for the triceps machine. So, if you have pain on a machine, ask a trainer for advice.
  • They are efficient for home use but can get pricey. In all cases, I recommend having a few sessions with a trainer if you've never lifted weights before.

I also recommend exercise tubing for resistance exercise. Tubing is inexpensive and versatile. You can do lots of exercises with it, even in a chair. In fact, there are more exercises that you can do with tubing than with dumbbells and machines combined. All that, plus tubing is portable and you can stow it away in a drawer! I recommend starting with a set of four tubes for about $20. They come in colors to denote the tension. If you order them, make sure to order the strap that allows you to attach the tube to a door (critical for at least a dozen exercises including rows, triceps press-downs and kickbacks, lateral and v-front raises, pull-downs, upright rows, biceps curls, and more). To work the legs, hips, and glutes (buttock muscles), purchase leg bands.

Here are some vendors that sell exercise tubing:

http://www.performbetter.com/catalog/default.asp

http://www.power-systems.com

Other methods for resistance exercise include physioballs, medicine balls, Pilates, and Gyrotonics. Physioballs are great for abdominal work; medicine balls are great for side bends and torso twists, lunges (try holding the ball while you do giant lunges across the room), toe touches, overhead lifts, and tossing against a mini-trampoline or with a partner; Pilates and Gyrotonics both use machines (although there are Pilates mat classes as well) and are great for toning, stretching, balance, coordination, and strength. Gyrotonics is a system of exercise designed to improve flexibility and balance as well as strength. It differs from Pilates in that it works more on flexing the body inward whereas Pilates works on extending the body outward. It's a personal preference, and if you have a Gyrotonics center in your area, you might want to try it. Search online for a center near you.

Resistance Exercise Workout Routines

Below is a beginner weight-lifting workout routine. The program is broken up by muscle group and is geared toward three days a week but can be modified if you like for more or less days. Do 10-12 repetitions, one to three sets per exercise. That means select a weight you can lift 10-12 times to momentary fatigue with good form. When you can easily lift the weight 12 times, increase the weight.

Day 1: Chest (bench press with bar or dumbbell press, flies, pushups), triceps (bench dips, kickbacks)

Day 2: Back (bent-over rows or attaching the tube to a door), biceps (curls, standing, or seated)

Day 3: Shoulders (lateral raises, front raises), legs (squats, lunges)

Abdominal exercises at each workout (see ab exercises below)

There are dozens of exercises for both your lower and upper body. You can go to http://www.exrx.net for pictures and videos of exercises for every muscle group.

You can experiment with different splits. For instance, you could try the following:

Day 1: Chest (bench press with bar or dumbbell press, flies, push-ups), back (bent-over rows, pull-downs)

Day 2: Biceps (curls, standing, or seated), triceps (bench dips, kickbacks)

Day 3: Shoulders (lateral raises, front raises), legs (squats, lunges)

Here are some excellent abdominal exercises. Make sure to stretch your low back before and after doing them, and use an exercise mat on the floor for support and cushioning.

1. Bicycle maneuver: Lie flat on the floor with your lower back pressed to the ground. Put your hands beside your head. Bring knees up to about 45-degree angle and slowly go through a bicycle pedal motion. Touch your left elbow to your right knee, then your right elbow to your left knee. Keep even, relaxed breathing throughout.

2. Captain's chair: While seated, stabilize your upper body by gripping the hand holds and lightly pressing your lower back against the back pad. The starting position begins with you holding your body up with legs dangling below. Now slowly lift your knees in toward your chest. The motion should be controlled and deliberate as you bring the knees up and return them back to the starting position.

3. Crunch on exercise ball: Sit on the ball with your feet flat on the floor. Let the ball roll back slowly. Now lie back on the ball until your thighs and torso are parallel with the floor. Cross your arms over your chest and slightly tuck your chin in toward your chest. Contract your abdominal muscles, raising your torso to no more than 45 degrees. For better balance, spread your feet wider apart. To challenge the obliques, make the exercise less stable by moving your feet closer together. Exhale as you contract, and inhale as you return to the starting position.

4. Vertical leg crunch: Lie flat on the floor with your lower back pressed to the ground. Put your hands behind your head for support. Extend your legs straight up in the air, crossed at the ankles with a slight bend in the knee. Contract your abdominal muscles by lifting your torso toward your knees. Make sure to keep your chin off your chest with each contraction. Exhale as you contract upward, and inhale as you return to the starting position.

5. Reverse crunch: Lie flat on the floor with your lower back pressed to the ground. Put your hands beside your head or extend them out flat to your sides -- whatever feels most comfortable. Crossing your feet at the ankles, lift your feet off the ground to the point where your knees create a 90-degree angle. Once in this position, press your lower back on the floor as you contract your abdominal muscles. Your hips will slightly rotate and your legs will reach toward the ceiling with each contraction. Exhale as you contract, and inhale as you return to the starting position.

Using a Personal Trainer

If you're new to exercise, then it's a good idea to enlist the help of a personal trainer. Exercise is hard to learn on your own, and resistance exercise is especially so. It's just hard to learn it from books, and there's always that doubt about whether you're doing it right or not. A trainer will fix all of that. They can evaluate you and set up the proper routine for you. You can set up a plan with which you see the trainer several times a week or just once month to check in and to modify your plan. Consult with the trainer as to what to do, but ultimately you'll decide based on cost, availability, scheduling, and how confident you are doing it on your own.

If you're an exercise veteran but want a little push, a trainer might be perfect, even if for just a few sessions. It can add variety, change things up, and might just give you the boost you're looking for. By the way, a personal training session makes a great gift!

You should look for the following when selecting a trainer:

  1. Tell the trainer your story and what you want out of training. If you're unsure the trainer can help, then keep looking.
  2. A trainer should listen carefully, hear you, and understand what you're looking for. It's about your goals, not the trainer's.
  3. Make sure you feel comfortable with the trainer and that you're not afraid to ask questions. If there isn't a connection, you're not going to show up. You don't have to be in love, but it won't work if you don't get along.
  4. Ask the trainer for two to three references.
  5. The trainer should ask to speak with your doctor if he or she doesn't understand your medical problems. It's a good sign if a trainer asks for permission to speak with your doctor.
  6. Find out if you can speak with the trainer during time you're not training.
  7. Ask about payment and cancellation policies.

Trainers' fees vary all over the country, and the range is anywhere from $45 to $150 per session.

Trainers should be certified. Several organizations have certifications for personal trainers; they are ACSM (http://www.acsm.org/), NSCA (http://www.nsca-lift.org/), and ACE (http://www.acefitness.org/). There are other agencies certifying fitness and aerobics instructors, but these three are the most highly regarded. You can also check these Web sites to locate fitness trainers all over the country.

Exercising for Weight Loss

Exercise is the single best predictor of keeping your weight off. If you lose weight but don't exercise, you'll almost certainly regain it. How much exercise is necessary to keep your lost weight off is not known. Some people keep their weight off with 35-40 minutes of vigorous aerobic exercise with some resistance exercise three to four days a week, while others might need 45-60 minutes of lighter exercise five to six days a week. You won't know until you get to your goal weight and experiment. As for weight loss, that's another story. The bottom line is that to lose weight you must consume fewer calories than you burn no matter how much exercise you do. Even if you run a marathon every day you will not lose weight if you consume more calories than you burn. So, if you're not losing, then you are consuming more calories than you burn, even if you think you're not. There are some medical conditions that can cause weight gain or resistance to weight loss. Adrenal problems, thyroid conditions, some rare hormonal imbalances, and even cardiac conditions in which there is retention of fluid are examples. There are also medications that can cause weight gain or resistance to weight loss. Mood stabilizers or antidepressant medications are examples that may fit in this category. Now, exercise does burn calories, and as long as you don't compensate for the calories burned by eating more (some people figure they exercised so why not eat more, or they're simply hungrier), then exercise will certainly help your weight-loss efforts. But again, the bottom line to losing weight is to burn more calories than you consume, and to keep it off, exercise is key.

Exercise for Metabolism

It used to be thought that aerobic exercise would raise metabolism for hours after a workout. The fact is that metabolism returns to baseline usually within half an hour of your workout. Research on resistance exercise, on the other hand, shows that you can increase your metabolism by as much as 100% if the intensity is high enough, and it can stay elevated for as much as 10-12 hours afterward.

What's Your Body Mass Index (BMI)?

One way to know if you are at a healthy weight is to determine your BMI. BMI is a way to estimate your excess weight and risk of disease. The formula is: weight (lbs.) / [height (in.)]2 x 703 . That is, divide weight in pounds (lbs.) by height in inches (in.) squared and multiply by a conversion factor of 703. Here's an example:

Weight = 150 lbs.

Height = 5'5" (65")

Calculation: [150 ÷ (65)2] x 703 = 24.96

An important point about BMI is that it can overestimate body fat and poor health in individuals who are muscular. For example, a 5'10", 210-pound individual with 10% body fat is not obese but would be considered so by the BMI charts. The authors of the BMI formula readily admit this error, but for the majority of Americans who are not lean and muscular, BMI is a good estimator of body fat and increased health risk...just not for every person. Another way to estimate your health risk is your waist circumference across your belly button. Women should be less than 35 inches and men less than 40 inches. Some scientists believe that waist circumference is more important than BMI for assessing health risk, and so I recommend that you take your waist circumference as an accurate health-risk indicator.

Exercise Videos

Videos can be very helpful. If you're busy and can't get to a gym, then a video at home is great. It's guided, the music is great, and it's fun. There are so many videos now that you have your choice of type and level of fitness. You can choose from beginning yoga, advanced tai chi, weight lifting, exercise for moms with their kids, or exercises in a chair. The sky's the limit. Check out Collage Video (http://www.CollageVideo.com) for tapes or DVDs that would work for you. If you need exercises sitting down, consider chair exercises from Armchair Fitness (http://www.ArmchairFitness.com).

The opportunities to exercise are endless. Choose the one that appeals most to you, whether it's walking, jogging, swimming, dancing, weight lifting, or stretching. The main point is to do something. The benefits happen quickly. The first step is to get started.

Web Links and More Information

Active at Any Size
http://www.niddk.nih.gov/health/nutrit/activeatanysize/active.html#activeat

American Volkssport Association (national walking clubs)
http://www.ava.org/

American Hiking Society
http://www.americanhiking.org/

Rails to Trails (walking/biking trails on abandoned rail beds)
http://www.railtrails.org/default.asp

The President's Council on Physical Fitness and Sports
http://www.fitness.gov/

Surgeon General and Fitness - Report of the Surgeon General
http://www.cdc.gov/nccdphp/sgr/fact.htm

Physical Activity and Weight Control
http://www.niddk.nih.gov/health/nutrit/pubs/physact.htm

American Council on Exercise
http://www.acefitness.org/

Exercises for Every Muscle Group
http://www.exrx.net/

Vendors

http://www.flaghouse.com/

http://www.performbetter.com/

http://www.power-systems.com/

Collage Video
http://www.collagevideo.com/

Armchair Fitness
http://www.armchairfitness.com/

Training Plans

http://www.coolrunning.com/

http://www.halhigdon.com

http://www.jeffgalloway.com/

http://www.runnersworld.com/home/

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Reviewed on 12/12/2017
Sources: References