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Home Health tree with naked man logoPhysical Activity and Health: Lecture

These lecture notes are copied from the multimedia version of the lecture that is posted online. Some of this information may only make sense if you view the multimedia slides.

 

Physical Activity and Health: Main Menu

The late 1960s brought a revolution in exercise. The Aerobics movement captured the attention of everyone and created an exercise boom that has endured. However, it became apparent that far too many adults were not engaging in exercise according to the recommended duration, frequency and intensity. For many, these guidelines were just too restrictive. A burning question emerged: does one really have to exercise according to this longstanding "exercise prescription" or are lower amounts of exercise and activity also beneficial?

One of the most profound developments of the 1990s was the publishing of the first ever Surgeon General's Report on Physical Activity and Health. This report made it clear that lower amounts of exercise and activity could have significant health benefits. This module will discuss the newer recommendations for both health-related and fitness-related activity.

The photo is of the San Luis Obispo Criterium.

Health-related Activity: Submenu

The first part of our discussion is related to the difference between health-related and fitness-related activity. And the new Surgeon General's recommendations for activity and health.

The photo on the left is of bicycle tourists in the Redwoods of Northern California. On the right, Napa Valley. Bicycle touring is a combination of biking and camping and is an example of health-related activity.

Health-related Activity: Explained

One does not have to achieve high levels of fitness in order to enjoy the health benefits associated with physical activity. Being more active in your everyday life can confer many health benefits including burning calories, and relieving stress. Recreational activities, like playing frisbee, besides being fun, may contribute to your health by adding to your total volume of moderate intensity activity.

Health-related Activity: Examples

Health related activity includes, but is not limited to, household chores, walking for transportation or recreation, recreational activity, or anything else that increases energy metabolism to moderate levels. For examples of moderate level activity, see the Surgeon General's report on Physical Activity and Health.

There are many ways that you can add more activity to your daily routine:

Activity and Mortality

Ongoing studies have shown that as a person increases their energy expenditure in moderate intensity activity, death rate from all causes declines. In fact, inactivity is becoming a more important predictor of early death than other historic risk factors like smoking, high blood pressure and high cholesterol.

A good way to start becoming more active is to just do it! It's not necessary to worry initially about training heart rates, frequency and duration. That will come with time. Instead, focus on your current activity level and then try to increase it. Using stairs instead of elevators and escalators, walking to the store instead of driving, or even walking your dog more often.

Relative Risk for All-cause Mortality

Low fitness, or inactivity, used to be considered only moderately important as a risk factor for early death. The Surgeon General's report cited numerous studies indicating that low fitness may be a more important risk factor than once thought. When compared to other traditional risk factors for premature death, Low Fitness was the strongest predictor of all cause mortality in both men and women.

Physical Activity: Prescription

The 1996 Surgeon General's report on Physical Activity and Health recommends that the average American should accumulate 30 minutes of moderate intensity activity per day on most, if not all, days of the week. The value of activity is cumulative and therefore short bouts of activity interspersed throughout the day, add to the health benefits associated with health-related activity.

Far from being unimportant, frequent short bouts of activity throughout your day can make a significant impact on your overall health. All you need to do is to take every opportunity to make your day more active rather than less active. When presented with an opportunity, select the most active of two options.

Fitness-related Activity: Submenu

The photos in the multimedia slide show two people engaging in fitness-related activities. For many, the main reason for exercising is to improve their fitness level. They want to perform better at recreational sports like tennis or basketball, or they want to improve their running or cycling distances and times. Go to next slide to learn the difference between health and fitness-related activity.

Photo on above left shows the Cuesta College pool in San Luis Obispo, CA. On the right, recreational riding in Morro Bay.

Fitness-related Activity: Explained

Fitness related activity is designed to greatly improve one or more of the components of fitness. While moderate activity will confer health benefits, seeking higher levels of fitness can add to those benefits. Starting with health-related activity, one can then progress on to greater fitness levels when one so desires.

Fitness-related Activity: Examples

In order to enhance any of the components of fitness, you will have to increase your effort levels during your workout. For physiological capacities to increase, you must place demands on your body that cause the body to adapt to those demands by becoming stronger, more flexible, etc. Any exercise that elicits the desired adaptation to training is said to produce the "Training Stimulus" which leads to what is called the "Training Effect".

Fitness Levels and Heart Disease

There is an inverse relationship between fitness (in this case measured by VO2 max) and death rates from heart disease. Achieving greater levels of fitness may prevent heart disease. Notice that women do not suffer from heart disease as often as men, however that difference diminishes at higher fitness levels. That is, as men increase their fitness levels, they become nearly as resistant to heart disease as women.

Components of Fitness: Submenu

The photographs in the multimedia slide illustrate the four components of fitness. The four components include: aerobic endurance, muscular strengths and endurance, flexibility, and body composition. Each person's fitness program should consider how to enhance each of these four components. An ideal fitness program is one that exhibits a balance between each of the four fitness components. Go to the next slide to learn more about aerobic endurance.

Aerobic Endurance

The key characteristic of aerobic activity is rhythmical, continuous movement. Thus, in order to enhance aerobic endurance, a given activity must exhibit this key characteristic. For example, though bicycling may be an aerobic activity, coasting long distances ceases to become aerobic since you are not utilizing your muscles in a continuous fashion.

Regular aerobic training produces a more efficient cardiovascular system including the heart, lungs and blood vessels. From a practical point of view, you will experience more energy and a decreased perception of effort with any given workload.

Aerobic Activities

Any activity that is rhythmic and continuous in nature is an aerobic activity. This would include cross-country skiing, dance/step, running/jogging, walking, rowing, spinning, etc. The key to aerobic activity is rhythmical, continuous contraction of muscles. This type of muscle utilization causes the muscles to use oxygen, hence the name "aerobic" (with oxygen).

Benefits of Aerobic Endurance

Since rhythmic, continuous activity places a continual demand on the heart, it is no surprise that the heart becomes a more efficient pump. The practical benefits to you is that you can work harder, and be more active without becoming tired or overexerted. Your heart works more efficiently at any given workload, your body becomes more efficient in utilizing oxygen for fueling activity, and your blood system maintains a lower, healthier blood pressure.

Aerobic Exercise Prescription

The American College of Sportsmedicine recommends the following prescription in order to achieve moderate to high aerobic fitness levels. In order to achieve the benefits of regular aerobic activity, you will need to perform aerobic exercise between 3 days and 5 days per week. While some extra improvement in aerobic capacity may be realized with exercising more than 5 days per week, there is extra risk with such a program. Exercising too many days per week may lead to "overtraining" and associated overuse injuries like "shin splints" and other forms of tendinitis. Overtraining may also predispose one to illness as the immune system may become "run-down" and suppressed.

Twenty to 60 minutes is the recommended "duration." It takes a minimum of 20 minutes to achieve the aerobic "training effect." The appropriate "intensity" should be between 70 and 85% of your maximum heart rate (MHR). Since exercise intensity is the most difficult of the exercise prescription to measure, we will consider heart rate in some detail below.

How to Measure Heart Rate

Using your first and second fingers (not thumb), press lightly on either the thumb side of the inside of the wrist (radial artery), or in the groove on the side of the neck. Be sure to press lightly, especially during exercise, as hard pressure may cause a reflex lowering of blood pressure. Count for 15 seconds and multiply by four for your heart rate in beats per minute (bpm).

Knowing how to count your pulse rate will come in useful for gauging your exercise intensity and also as a rough estimate of your initial fitness levels. The next slide will demonstrate how resting pulse rate can be used to estimate initial fitness levels.

Heart Rate as a Predictor of Fitness

As your heart adapts to aerobic activity, it becomes a stronger and more efficient pump. One of the indicators of the efficiency of the heart is resting heart rate. A lower heart rate (generally) means that your heart is more efficient and you are more fit.

Use the norms in the table in the multimedia slide to estimate your fitness level. Be sure to use your morning resting heart rate. Take your heart rate in the morning when you wake up for 3 or 4 days. Use the average to signify your normal resting heart rate.

Exercise Benefit Zone (EBZ)

Calculating your EBZ is an easy and fairly accurate way of determining your exercise intensity. Monitoring exercise intensity is important to achieving optimal aerobic condition. You can calculate your EBZ, sometimes called Target Heart Rate (THR), by using the formula (in red) on the slide, or by using the chart to the right of the formula. Calculate for the upper (85%) and lower (70%) limits. These limits represent the highest and lowest heart rates necessary to achieve optimal aerobic fitness. The next time you go out to perform aerobic exercise, about 10 minutes into your workout, take time to record your heart rate. Your heart rate for 15 seconds should be between the 70-85% range.

Muscular Strength/Endurance

The photo in the multimedia slide, taken in a community college weight room, shows students in a typical weight training class. Weight training programs come in all shapes and sizes and attempt to achieve gains in muscular strength and endurance. Your personal fitness instructor, teacher or coach will show you how to optimize your training program to achieve your goals.

Muscular strength is necessary to move objects. Lifting boxes or pushing a lawn mower are examples of activities that require a certain amount of strength. The larger the object, the more strength you will need to lift or push it. Muscular endurance is the ability to exert your strength continuously and repetitively. A baseball pitcher needs muscular endurance in order to repeat the pitching motion many times throughout a game without getting fatigued.

You will need varying amounts of strength and endurance to perform everyday tasks throughout your lifetime. As people age, they often lose their strength and endurance capacities. As a result, they have increasing difficulty performing typical everyday tasks that are necessary to remain independent. This loss of strength and endurance with age is not so much a result of age as it is a result of inactivity. As people get older, they often become less active. Strength and endurance, like the other components of fitness, are lost unless a person stays active.

Muscular Strength/Endurance Activities

Weight training is perhaps the most systematic way of achieving muscular strength and endurance. However, you can also practice all types of calisthenics using your body as the resistance (weight).

Often, when people go on vacation, they think they must put their workouts on hold. Just because a weight room is not accessible, doesn't mean that you can't develop or maintain muscular strength. There are many ways to retain muscular strength and endurance which require no special exercise equipment. Using a chair or bench you can perform bench dips, incline push ups and crunches (shown in the animation). You can also use empty milk jugs filled with water as weights. It takes very little room to pack a jump rope or piece of surgical tubing which can be used for a number of types of exercises and stretches. With a little imagination, you can organize many household items into a "road gym".

Benefits of Strength Training

Just as there are many ways to increase muscular strength and endurance, there are also many benefits. Increases in lean body weight (LBW) and decreases in percent fat are common outcomes of a strength training program. As muscles adapt to this type of regimen, there is an increase in muscle fiber size and, thus, strength. Other supportive tissue like tendons and ligaments also increase in strength. Bone adapts by becoming more dense, and there is an increase in the healthy type of cholesterol.

The photo shows someone working out at a local tennis club.

Strength Training Prescription

The American College of Sportsmedicine recommends the following as the minimum prescription for developing moderate to high muscular fitness levels. In order to enhance muscular fitness, you should develop an exercise program which has 8 - 10 exercises for the various major muscle groups. These exercises should utilize opposing muscle groups. In other words, if you choose an exercise for the front of the arms, you should also include an exercise for the back of the arms, or, if you include exercises for the chest, you should also include exercises for the upper back.

Each exercise should be performed in sets of 8 - 12 repetitions. One set is the minimum that should be performed for each exercise. As time permits, 2 - 3 sets of each exercise will provide greater benefits. You should perform your muscular fitness program at least two days per week. As you get stronger, or if time permits, you can increase the number of days to 3 - 5 days.

If you are inexperienced with the use of weights or of proper lifting techniques, you should seek the advice of a professional before embarking on a weight training program, or, you can enroll in a basic weight training class. If you are more interested in muscular endurance, you can take a Circuit Weight Training course.

Flexibility

Flexibility is something that people often lose with age (as the woman in the photo, back right). But loss of flexibility is more closely associated with inactivity than with age. In other words, if you don't use it, you lose it. Someone who is flexible can move their joints through their entire intended range of motion. Lack of flexibility can negatively effect your performance in many ways. Poor flexibility creates extra effort when performing many common tasks. Poor flexibility also negatively effects your performance in recreational activities such as tennis or golf. Proper stroke mechanics require good flexibility. Flexibility facilitates efficient stroke mechanics which adds to ones skill level, thereby enhancing enjoyment of the activity.

Reasons to Stretch

There are many good reasons to stretch, and there are many different times that are appropriate: before and after exercise, before going to bed, while you are watching TV, or even while you are talking on the phone.

1. Range of motion is necessary for success in many activities. Tennis, bowling, volleyball and other recreational activities are just a few examples of activities requiring good flexibility.

2. Stretching starts blood flow to the working muscles and thereby. . .

3. Prepares the body for the stress of activity.

4. Stretching also prevents some kinds of soreness, specifically the kind that comes from microscopic tears of the muscles. Engaging in strenuous activity when the muscles are cold may lead to muscle injury.

How to Stretch

There are right and wrong ways to stretch. The right way emphasizes a slow, gradual "static" stretch. The wrong way is to stretch in fast, forceful or "ballistic" movements. Everyone has different levels of flexibility. You may not be able to stretch like your friend the dancer, and you may never be able to, so don't compare yourself to anyone else. Gauge your success by your own progress.

Body Composition

In recent years, we have come to understand the relative importance of knowing a person's body composition, not just their weight. The two-component model of body density starts with the assumption that your body has two components: fat, and fat-free weight. It is fat-weight that seems to be implicated in many diseases. Therefore, we are becoming interested in our body fat levels and in learning how to more accurately measure the body's fat component. The photo in the multimedia slide illustrates underwater weighing, also called "hydrostatic weighing". This method has been long considered the "gold standard" for comparing methods of determining body fat. Though hydrostatic weighing is considered a standard, there is still a significant error factor when measuring body fat. It is important to understand that body fat measurements are imprecise, at best, and that your body fat value is only an estimate, no matter what method is used. Body fat measures must be considered along with other measures of health and fitness to form a reasonably accurate basis for exercise and nutrition prescription.

Suggested Body Fat Goals

While some people try to achieve low levels of body fat for particular reasons (athletics, social pressure, etc.), extremely low body fat may not be healthy. On the other hand, too much body fat may lead to disease. The chart in the slide represents one method of categorizing acceptable body fat ranges. Though body fat testing may give us an estimate of fat levels, any given measurement is prone to error. Therefore, you should set your goals for somewhere within an acceptable range of values for your age category.

Measuring Body Composition

There are simple and complex methods for measuring body composition. Two of the more common, not to mention accurate, are the underwater weighing technique (hydrostatic weighing) and the skinfold caliper methods. Though there is still potential for error, these two methods can provide a pretty good picture of our levels of body fat and provide valuable information for exercise and weight control prescription. Body fat measurements should never be used by themselves to predict a persons overall health status. Other physical and physiological assessments will help to create a balanced and more accurate picture of ones health and how one should modify their lifestyles.

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