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Medicine LibreTexts

11.3: Adding Physical Activity to Your Life

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  • Overcoming the Barrier to Being Physical Active

    Given the health benefits of regular physical activity, we might have to ask why two out of three (60%) Americans are not active at recommended levels.

    Many technological advances and conveniences that have made our lives easier and less active, as well as many personal variables, including physiological, behavioral, and psychological factors, may affect our plans to become more physically active. In fact, the 10 most common reasons adults cite for not adopting more physically active lifestyles are (Sallis and Hovell, 1990; Sallis et al., 1992):

    • Do not have enough time to exercise
    • Find it inconvenient to exercise
    • Lack self-motivation
    • Do not find exercise enjoyable
    • Find exercise boring
    • Lack confidence in their ability to be physically active (low self-efficacy)
    • Fear being injured or have been injured recently
    • Lack self-management skills, such as the ability to set personal goals, monitor progress, or reward progress toward such goals
    • Lack encouragement, support, or companionship from family and friends, and
    • Do not have parks, sidewalks, bicycle trails, or safe and pleasant walking paths convenient to their homes or offices.

    Understanding common barriers to physical activity and creating strategies to overcome them may help you make physical activity part of your daily life. Please visit the link below to see a full table of SUGGESTIONS FOR OVERCOMING PHYSICAL ACTIVITY BARRIERS:

    Creating your own Fitness Program

    The first step to implementing a fitness program is to identify your goals. As discussed in earlier chapters, goals should be specific, measurable, action-oriented, realistic and time-bound (SMART). Progress can be difficult to track if goals are vague and open-ended, such as “I will exercise more.” Here is an example of a SMART goal for fitness:

    • Specific: “I will walk for 30 minutes a day 3-5 days per week
    • Measurable: “I will improve my resting heart rate over the next month”
    • Action-Oriented: “I will research walking routes around my home and campus”
    • Realistic: “I will increase my walking to 45 minutes per day in one month”
    • Time Bound: “I will try this walking program for one month and then reassess my goals”

    You can also make a SMART Goal in one statement, such as “I will walk for 30 minutes 3-5 days per week for the next month in order to improve my resting heart rate.

    FITT Principle

    Using the FITT principle is one way remember the guidelines for physical activity and create a prescription for improvement in your health-related physical fitness.

    • Frequency: how often a person performs a health-related physical activity.
    • Intensity: how hard a person exercises during a physical activity period. Intensity can be measured in different ways, depending on the related health-related component.
    • Time: also known as duration. Refers to the amount of time or repetitions when performing a physical activity.
    • Type: the kind of exercise or physical activity a person is performing.

    Adapted from:

    Table \(\PageIndex{1}\)

      Cardiorespiratory Flexibility Muscular Endurance Muscular Strength



    3-5 times per week

    Increase frequency as you get into better shape

    Should be a regular part of your warm-up and cool-down

    Increase frequency as you get into better shape

    Daily for some muscle groups

    Perform 3-4 times per week

    Increase frequency as you get into better shape

    Perform 3 times per week

    Different muscle groups each time you work out

    Increase frequency as you get into better shape 



    50%-60% of heart rate reserve

    Increase intensity as you get into better shape

    Stretch all major muscles and joints; hold for 15-30 seconds

    Perform 1-3 repetitions

    Increase intensity as you get into better shape

    Less than 50% of your predicted 1-rep max

    Start with body weight then add resistance 15 or more reps/1-3 sets

    Increase intensity as you get into better shape

    60%-80% of 1-rep max

    8-12 reps / 1-3 sets

    Increase intensity as you get into better shape



    20-60 minutes of continuous activity

    Increase the time as you get into better shape

    10-20 minutes

    Increase the time as you get into better shape

    30-60 minutes

    Increase the time as you get into better shape

    15-60 minutes

    Increase the time as you get into better shape



    Running, cycling, swimming, and activities that use large muscles Perform static stretches and controlled dynamic stretches Resistance training (body weight/ tubing/medicine balls/free weights) Resistance training (body weight/ tubing/medicine balls/free weights)

    Measuring Intensity

    Target Heart Rate and Estimated Maximum Heart Rate

    Exercise intensity can be measured using either heart rate or the rating of perceived exertion (RPE) method. We will look at each of these methods in turn. There are two methods of using heart rate to measure exercise intensity: the percentage of maximal heart rate method and the heart rate reserve (HRR), or karvonen method.

    As its name suggests, the percentage of maximal heart rate method involves prescribing exercise at a certain percentage of maximum heart rate. To find out a person’s true maximum heart rate we need to measure it in a laboratory. However, for most people this is impractical; therefore we can estimate maximum heart rate using the formula ‘220 – age’.

    Example 1: Percentage Heart Rate Method

    Case study: ‘Mariella’, age 30

    1. Calculate maximum heart rate (HRmax)
      • Estimated HRmax= 220 – age
      • = 220 – 30= 190 bpm (beats per minute)
    2. Calculate exercise intensity
      • ACSM guidelines = 55–90% of HRmax
      • Lower target (55%) = 190 × 55%
      • = 190 × 0.55 = 104.5 bpm (we would round this up to 105 bpm)
      • Upper target (90%) = 190 × 90%
      • = 190 × 0.90 = 171 bpm

    This formula gives us an idea of maximum heart rate, but we must remember that it is just an estimate and not completely accurate. Therefore using this method, according to ACSM guidelines, Mariella should exercise at a heart rate somewhere between 105 and 171 bpm. This is quite a wide range so, depending on her fitness levels, you would need to decide whether to prescribe Mariella exercise to the upper or lower end of this scale.

    Please note that there are online calculators available to calculate all of this information for you. Once such calculator can be found at:

    The HRR method is thought to be more accurate than the percentage of maximal heart rate method because it takes the individual’s resting heart rate into account. The formula for calculating HRR can be seen in Box 2. The ACSM recommends that to improve aerobic fitness, exercise intensity should be set at either 40–85 per cent of (HRR) or 55–90 per cent of maximum heart rate (HRmax) (Pollock et al., 1998). These ranges are deliberately broad to reflect different levels of fitness; that is, someone with relatively low levels of fitness who has just started an exercise programme may need to work on the lower end of the scale, whereas someone who has a higher level of fitness, perhaps who has been exercising for a while, may need to work at an intensity towards the upper end of the scale. This demonstrates the importance of progression in an exercise programme.

    Example 2: Heart Rate Reserve Method

    Case study: ‘Mariella’, age 30

    1. Calculate maximum heart rate (HRmax
      • Estimated HRmax = 220 - age 
      • = 220 – 30 = 190 bpm (beats per minute)
    2. Measure resting heart rate (HRrest)
      • You would measure this either using a heart rate monitor or manually, using your fingers. Ideally it should be measured first thing in the morning. Let's imagine that Mariella's HRrest has been measured at 70 bpm.
    3. Calculate heart rate reserve (HRR)
      • HRR = HRmax – HRrest = 190 – 70 = 120 bpm
    4. Calculate exercise intensity
      • ACSM guidelines = 40–85% HRR
      • Lower target (40%) = (HHR × 40%) + HRrest
      • = (120 × 0.40) + 70
      • = 48 + 70 = 118 bpm
      • Upper target (85%) = (HHR × 85%) + HRrest
      • = (120 × 0.85) + 70
      • = 102 + 70
      • = 172 bpm

    Using this method, according to ACSM guidelines, Mariella should exercise somewhere between 118 and 172 bpm.

    Borg Scale

    An alternative to using heart rate methods is the RPE method of measuring exercise intensity. However, you should note that it is difficult to give a general recommendation for RPE, as it is by its very nature open to personal interpretation; that is, what I consider to be a 12 may be different to what you consider to be a 12.  RPE can be a useful way of measuring exercise intensity when heart rate monitoring is difficult or inappropriate. For example, some types of medication (e.g. beta blockers) given to people with hypertension lower the heart rate, and therefore heart rate measurement is not appropriate for people on this type of medication. The Borg Rating of Perceived Exertion (RPE) Scale is one way to measure perceived exertion. In medicine, this is used to document the patient’s exertion during a test, and sports coaches use the scale to assess the intensity of training and competition. The original scale introduced by Gunnar Borg rated exertion on a scale of 6-20. The seemingly odd range of 6-20 is to follow the general heart rate of a healthy adult by multiplying by 10. For instance, a perceived exertion of 12 would be expected to coincide with a heart rate of roughly 120 beats per minute.
    Set Points on Scale

    It ranges from 6 to 20, where 6 means “no exertion at all” and 20 means “maximal exertion.” Choose the number from below that best describes your level of exertion. This will give you a good idea of the intensity level of your activity, and you can use this information to speed up or slow down your movements to reach your desired range.

    Try to appraise your feeling of exertion as honestly as possible, without thinking about what the actual physical load is. Your own feeling of effort and exertion is important, not how it compares to other people’s. Look at the scales and the expressions and then give a number.

    1. No exertion at all
    2. Extremely light (7.5)
    4. Very light
    6. Light
    8. Somewhat hard
    10. Hard
    12. Very Hard
    14. Extremely hard
    15. Maximal exertion

    9 corresponds to “very light” exercise. For a healthy person, it is like walking slowly at his or her own pace for some minutes.

    13 On the scale is “somewhat hard” exercise, but it still feels OK to continue.

    17, Or “very hard,” is very strenuous. A healthy person can still go on, but he or she really has to push him- or herself. It feels very heavy, and the person is very tired.

    19 on the scale is an extremely strenuous exercise level. For most people this is the most strenuous exercise they have ever experienced.

    Taking Your Heart Rate

    Generally, to determine whether you are exercising within the heart rate target zone, you must stop exercising briefly to take your pulse. You can take the pulse at the neck, the wrist, or the chest. We recommend the wrist. You can feel the radial pulse on the artery of the wrist in line with the thumb. Place the tips of the index and middle fingers over the artery and press lightly. Do not use the thumb. Take a full 60-second count of the heartbeats, or take for 30 seconds and multiply by 2. Start the count on a beat, which is counted as “zero.” If this number falls between 85 and 119 bpm in the case of the 50-year old person, he or she is active within the target range for moderate-intensity activity.

    Taking your heart rate.PNG

    Figure \(\PageIndex{1}\) Taking your heart rate