Prescription of Exercise for Health and Fitness

CHAPTER 20 Overview Health benefits of exercise Medical clearance Exercise prescription Monitoring exercise intensity Exercise program Exercise and rehabilitation of people with diseases

Health Benefits of Exercise 1960s: Dr. Kenneth Cooper 1970s to 1980s: fitness boom 1990s: The Great Awakening –1992: inactivity major risk for CAD (AHA) –1994: exercise public health initiative (CDCP/ACSM) –1995/1996: statement on exercise and cardiovascular health (NIH) –1996: report on health benefits of exercise (Surgeon General) –2000: identification of sedentary death syndrome

Health Benefits of Exercise Exercise not a priority in US population –Awareness of health benefits high –Application of knowledge low Exercise should not intimidate –30 min brisk walking, 15 min running –Every day or almost every day –Health benefits  as duration and intensity 

Medical Clearance Medical evaluation useful and important prior to starting exercise program –Medical information can be used to develop exercise prescription –Provides baseline to measure progress High-risk individuals should exercise only under medical supervision

Medical Clearance Medical evaluation provides motivation –Blood pressure –Percent body fat –Blood lipid values Periodic medical evaluations can identify dangerous conditions earlier

Medical Clearance: Medical Evaluation Low-risk/healthy individuals –Medical evaluation not required –Medical system could not handle patient load Moderate-risk individuals –2+ risk factors for cardiovascular, pulmonary, or metabolic disease, no signs or symptoms –Medical evaluation recommended High-risk individuals –1 or more signs or symptoms of disease –Medical evaluation recommended

Table 20.1

Medical Clearance: Risk Stratification Used by health and fitness professionals during screening process Risk stratification helps identify –Individuals with medical contraindications –Individuals with clinical conditions who need a medically supervised exercise program –Individuals at  risk for disease who need medical evaluation and exercise testing prior to exercise –Special needs that affect testing and prescription

Risk Stratification for Exercise Prescription

Medical Clearance: Graded Exercise Testing Graded exercise test (GXT) –Treadmill most common –Increase intensity gradually to maximal –Monitor subject for discomfort, warning signs Exercising ECG necessary –Resting ECG may not reveal all abnormalities –Exercising ECG can unmask coronary artery disease (CAD)

Medical Clearance: Graded Exercise Testing Can detect –Arrhythmias –ST segment changes (myocardial ischemia) –Results positive or negative, possibility of false negative or false positive Positive ECG requires follow-up tests –Coronary arteriogram –CT, MRI scans of heart

Figure 20.3

Figure 20.4

Medical Clearance: Graded Exercise Testing Sensitivity of exercise ECG –Can GXT correctly identify clinical populations? –Low (66% identified) for asymptomatic CAD Specificity of exercise ECG –Can test correctly identify healthy individuals? –Higher (84%) specificity Predictive value of abnormal exercise ECG –Do abnormal results actually indicate disease? –Low (~24%) for asymptomatic CAD

Medical Clearance: Graded Exercise Testing GXT has limited value in young and healthy –Accuracy of ECG questionable –Actual risk of cardiac arrest low –Expensive, less accessible test GXT recommended for –Moderate-risk cohorts –High-risk cohorts

Exercise Prescription Exercise program designed to improve aerobic capacity in untrained individuals Four basic factors of exercise prescription –Mode or type of exercise –Frequency of participation –Duration of each exercise bout –Intensity of exercise bout

Exercise Prescription Minimum threshold –Point below which no improvements occur –Exists for frequency, duration, and intensity –Varies with each individual Once minimum threshold exceeded, aerobic capacity increases

Exercise Prescription: Mode Modes most frequently prescribed –Walking/hiking/jogging/running –Cycling –Rowing –Swimming Less common modes –Spinning, aerobic dance –Racket sports

Exercise Prescription: Mode For competitive sports, precondition using common modes –Improves aerobic fitness prior to sport training –Improves success in sport performance Preconditioning required for several weeks or months before sport training starts –Sport maintains aerobic fitness –Sport may further improve aerobic fitness

Exercise Prescription: Mode Mode should be enjoyable and motivating Mode should be challenging Mode should produce needed benefits Multiple modes helpful –Inclement weather –Boredom

Exercise Prescription: Frequency and Duration Frequency –Optimal: 3 to 5 days per week –Start gradually, avoid burnout/fatigue –Less important than intensity or duration Duration –Optimal: 20 to 30 min per day –One long bout or multiple shorter bouts –Inverse relationship between duration and intensity

Exercise Prescription: Intensity Intensity most important factor –Minimum recommended: 50 to 60% VO 2max –Upper limit depends on purpose of training –Upper limit seldom exceeds 80% VO 2max High-intensity, low-volume interval training –Markedly increases aerobic capacity –Results seen in 2 weeks

Monitoring Exercise Intensity Training heart rate (THR) –Based on linear relationship between HR, VO 2 –Use target HR corresponding to target % VO 2max –75% VO 2max = 87% HR max (not 75% HR max ) Karvonen method for THR –Maximal HR reserve = HR max – HR rest –THR calculated as percent of maximal HR reserve –THR 75% = HR rest (HR max – HR rest )

Figure 20.5

Monitoring Exercise Intensity Training HR range –Example: 50 to 75% maximal HR reserve –Will ensure training response –Start at low end and move up HR correlated with cardiac work –THR ensures constant rate of work done by heart regardless of environmental conditions –Safe for high-risk patients –Allows for improved aerobic fitness

Monitoring Exercise Intensity Metabolic equivalent (MET) –Gauges intensity based on O 2 consumption –1 MET = 3.5 ml O 2 /kg/min –1 MET = resting metabolic rate Published MET values for activities but –MET can vary considerably among individuals –Values fail to account for environmental conditions –Values fail to account for physical conditioning

Monitoring Exercise Intensity VO 2 reserve (VO 2 R) method –ACSM position stand –VO 2 R = VO 2max – VO 2rest –Prescribe exercise as % VO 2 R –Assumes 1 MET = universal resting VO 2 % Maximal HR reserve versus % VO 2 R

Monitoring Exercise Intensity Ratings of perceived exertion (RPEs) –Individuals rate how hard exercise feels –Numerical rating scale Borg RPE scale –Scale 6 to 20 –Corresponds with HR –Very accurate when used correctly

Table 20.3

Exercise Program Total exercise program includes 1. Warm-up, stretching activities 2. Endurance training 3. Cool-down, stretching activities 4. Flexibility training 5. Resistance training 6. Recreational activities First three activities, 3 to 4 times per week

Exercise Program Warm-up and stretching activities –Start with low-intensity calisthenics, stretching –Gradually increase HR, breathing –Prepare exerciser for more vigorous exercise –Can reduce muscle soreness Sample warm-up –5 to 10 min stretching –5 to 10 min low-intensity activity

Exercise Program Endurance training –Develops cardiovascular endurance –Improves capacity and efficiency of cardiovascular, respiratory, and metabolic systems –Controls body weight Best modes: walk/jog/run, cycle, swim, row Poor modes: golf, bowling, softball

Exercise Program Cool-down and stretching –Should conclude every endurance workout –Reduced intensity –Do not stop abruptly Stretching after exercise   flexibility

Exercise Program Flexibility training –Supplements warm-up and cool-down periods –Useful for those with poor flexibility, joint pain –Should be performed slowly Timing of flexibility training –Best after workout –Tissues may be more adaptable and responsive after exercise

Exercise Program Resistance training –Starting point: 10 repetitions at 1/2 1RM –Proper starting weight: fatigue at repetitions 8 to 10 –If 15 repetitions reached, increase weight 2 to 3 sets per day, 2 to 3 times per week Can reduce to 1 to 2 sets if needed (still see results in untrained people)

Exercise Program Recreational activities important aspect of comprehensive exercise program Guidelines for selecting recreation: Will the activity –Be learned and performed with moderate success? –Provide opportunities for social development? –Keep costs within budget? –Maintain long-term interest? –Be safe given health and age?

Exercise and Rehabilitation for People With Diseases Exercise a major component of rehabilitation Used in rehabilitation programs for –Cardiopulmonary disease –Cancer –Obesity, diabetes –Renal disease –Osteoporosis –Arthritis, chronic fatigue, fibromyalgia –Cystic fibrosis