Physiological Changes: Health Related Fitness Chapter 8 1 McGraw-Hill/Irwin © 2012 McGraw-Hill...

Physiological Changes:

Health Related Fitness

Chapter 8

Maintaining an active lifestyle is linked to good

health.

Cardiovascular Fitness

A form of muscular enduranceEfficiency of the heart, lungs, and vascular system in delivering oxygen to working tissueYour ability to deliver oxygen to the muscle is affected by

Heart rateStroke volumeCardiac outputMaximal oxygen consumption

Cardiovascular Fitness: Heart Rate

The number of times the heart beats each minute (HR)Changes over the lifespan

Fetal HR is rapid and irregularBirth HR is below fetal level with periods of bradycardia (HR < 60 bpm)

120-140 bpm

Children’s HR 1 year ~ 80-100 bpm HR will continue to decline at rest until adolescence

AdolescenceMale ~ 57-60 bpmFemale ~ 62-63 bpm

Overall, resting HR declines by 50% from birth to maturityAdulthood

Average ~ 75-79 bpm

There is a decline in HR with ageResearchers believe the decline in HR with age is due to a decrease in sympathetic outflow and changes in the contractile properties of cardiac muscle

To predict maximal HR220-age = HR maxHR max = 195-220 bpmDecline = 0.8 bpm/year of age

To predict maximal HR in the elderly HR max = 206 – 0.7(age in yr.)

Work and HRLinear relationshipAs workload increases, HR increases

Workload

Cardiovascular Fitness: Stroke Volume

The volume of blood ejected from the heart with each beat (SV)Size of SV affected by

Heart sizeContractile force of the heart muscleVascular resistance to blood flowVenous return

SV is lower in childrenDue to smaller heart

Lifespan changesBirth ~ 3-4 ml/beatAdolescence ~ 40 ml/beatMale adult ~ 70-90 ml/beatTrained male adult ~ 100-120 ml/beat

Maximal stroke volume is achieved during submaximal work

Workload

40-60% (O2max)

Maximal SV during exerciseUntrained male ~ 100-120 ml/beatUntrained female ~ 80-100 ml/beatTrained male ~ 150-170 ml/beatTrained female ~ 100-120 ml/beat

Differences between male and female values due to smaller heart in female

Stroke volume and ageBetween the ages of 25-85 yr., SV can fall by 30%

Lifespan activity can minimize the SV decline with age

Cardiovascular Fitness: Cardiac Output

Amount of blood pumped in 1 minute (CO)HR x SV = COAt rest, CO5 liters/min

70 beats/min x 70 ml/beat = 4900 ml/min or 4.9 liters/min

Cardiovascular Fitness: Cardiac Output

CO and exerciseAffected by physical conditionAge

Untrained male ~ 20-25 liters/minTrained male ~ 30-35 liters/minBecause HR and SV decline with age, so does CO

Decline of 1 % / year after age 25 yr.

Cardiovascular Fitness: Maximal Oxygen Consumption

The largest amount of oxygen that a human can utilize at the tissue level (VO2 max )This is the best measure of physical work capacity (ability to do work without fatigue)Very little data exist on children under 6 years of age

For boys ages 6 to 16 years, VO2 max 50 to 53 ml/kg/minFor girls at 8 yr., VO2 max = 50 ml/kg/min, on averageIf you do not correct for weight (kg), boys/men will always have higher absolute valuesTo compare males vs. females, correct for body weight (kg) (relative values)

There is a gradual decline in maximal oxygen consumption in young girls as maturity approaches due to

Increases in body fatLower blood hemoglobin concentrations A decline in large muscle development

Many girls become less active during adolescence

With age there is a decline in VO2 max and a concomitant decline in physical work capacityAn active lifestyle across the lifespan can alter this decline

Physical Activity and Cardiovascular

Fitness in ChildhoodInformation is fragmented and limitedAre changes in the cardiovascular values in children due to training or maturation?Some researchers question the value of endurance training in preadolescent children

Fitness in ChildhoodVO2 max has been shown to improve in prepubertal children (10-11 yr.)Prepubertal children can follow the standard prescription used by adults

Frequency = 3 days per weekIntensity = 60%-80% HR maxTime = 30 min

Cardiovascular Endurance Field-Test Data

Field test data involve non-laboratory devices capable of testing large numbers of children

Practical Inexpensive

Most popular field test for childrenTimed distance run

Cardiovascular Endurance Field-Test Data

Boys’ run time peaks at 16 yr.Girls’ run time peaks at 14 yr.On average, boys run faster than girls at all ages

Fitness in AdulthoodPrescription ~ FIT

Frequency = 3 to 5 days/weekIntensity = 60-90% HR maxTime = 20-60 min

Mode of activity is any large muscle group movement (walking, biking, running)A program of this sort will increase physical working capacity

Fitness in AdulthoodIt has been suggested that as much as 50% of the functional declines in the factors affecting physical performance are due to disuse and not agingChildren’s Activity Pyramid

Muscular Strength

Strength is the ability to exert a muscular forceStatic or isometric force – muscular force exerted against a non-moveable objectDynamic force – muscular force exerted against a moveable object

Defining and Measuring Muscular Strength

Field testsPull-up test ~ upper body strength/enduranceChin-up test ~ upper arm strength/enduranceModified bent-knee sit-up test ~ abdominal strength/endurance

Age-related Changes in Muscular Strength: Laboratory Tests

Grip strength test is a common test among children

Easy to administerReliable

Changes in strength are tied to changes in body weight

In boys, the strength “spurt” lags a year behind the height “spurt”

Boys tend to outgrow their strength just prior to pubertyMay explain why some boys experience a period of clumsiness

Boys’ fastest increase in muscular strength occurs 1 yr. after peak height

In girls, the strength spurt occurs during the same year as peak heightIn general, boys are 10% stronger than girlsGender differences are most apparent after puberty

Total body strength in women is 63.5% of menAbsolute upper-body strength in women is 50% less than menAbsolute lower-body strength in women is 20-30% lower than men

AgingBetween 25-50 yr. there is a slow loss in muscle mass of about 10%Between 50-80 yr. there is an accelerated loss of muscle mass of about 40%Therefore, one can lose approximately 50% of total muscle mass by the age of 80 yr.

Age-related Changes in Muscular Strength: Field Tests

Average scores for boys and girls on bent-knee sit-ups (60 sec) based on findings of the National Children and Youth Fitness Studies I and II

Average scores for boys and girls on modified pull-ups and chin-ups based on findings of the National Children and Youth Fitness Studies I and II

Abdominal strength/enduranceLittle differences exist between boys and girls ages 6 to 9 yr.After age 10 yr., boys outperform girlsPerformance for both boys and girls levels off between 16 to 18 yr.

Upper-body strength/endurance30% of boys age 10-11 yr. failed to perform 1 chin-up during the NCYFS IModified chin-up test developed for the NCYFS II

Modified Chin-up Test

Upper-body strength/enduranceLittle differences exist between boys and girls ages 6 to 9 yr.After age 10 yr., boys outperform girlsAfter age 10 yr., girls are not capable of performing any chin-ups

Muscular Strength Training

PrepubescentControversy exists regarding strength training for this populationCan children increase strength through a resistance training program?Can these strength gains improve athletic performance?

PrepubescentSkills showing improvement

Long jumpVertical jumpRunning speedAgility

Specificity ~ greatest skill improvement was for those activities in which the children were involved

PrepubescentProfessional organizations publishing position statements for prepubescent strength training

American Academy of PediatricsNational Strength and Conditioning AssociationAmerican Orthopedic Society for Sports Medicine

All three recognize the value of weight training

PrepubescentWeight training involves the use of various resistance exercises to increase muscular strength, endurance, and power for fitness or sportWeight/power lifting is a sport incorporating maximal lifts (until physically mature)

Not recommended for youth

Adolescence/early and middle adulthoodPrograms of progressive resistance training will result in improved muscular strength/endurance

1 RM (repetition maximum) in boys and girls ages 6.2-12.3 yr. is safe when conducted in the presence of adult supervision

Minimal training standards (ACSM)Frequency ~ 2 times per weekIntensity ~ 60% of 1 repetition maximumAmount ~ 1 set

1 set of 8 to 12 exercises8-10 repetitions per exercise

Adolescence/early and middle adulthoodConcerns for these populations

Valsalva Maneuver ~ breath holding (straining) during a liftAnabolic steroid use

Late adulthoodCan strength training in late adulthood alter, delay, or allow one to avoid the physiological deterioration associated with aging?Even though decreases in muscular strength can be expected with age, the rate of decline can be significantly slowed

Late adulthoodIt is never too late to start a resistance-training program

1.9% to 132% improvements in strength

For the elderly, it is the intensity of the training and not the initial level of fitness that determines the response to training

Late adulthood Strength training also decreases the number of falls experienced by this populationStrength training positively influences activities of daily living

Mechanisms of strength increaseIn the early phase of training, neural adaptation predominates

Most training studies incorporate this phase

In intermediate and advanced training, progress is limited to the extent of muscular adaptation that can be achieved

HypertrophyAnabolic steroid use

Adverse Effects of Anabolic Steroids

Flexibility

Range of motion with a jointFlexibility is joint specific

There is no one good test for overall flexibility

A typical flexibility test Sit-and-reach test / back saver sit-and–reach testTests the hamstring, back and hip flexibility

Flexibility Sit and reach test

Back saver sit and reach test

Flexibility

Average sit-and-reach scores for boys and girls based on finding of the National Children and Youth Fitness Studies I and II

Performance Trends

Flexibility

Flexibility declines with age due to changes in

Connective tissue (tendons, ligaments) ~ less resilient and may crack or fraySynovial fluid ~ less viscousCartilage ~ may be damaged from injury or lifelong wear and tear

Flexibility

Declining flexibility and agingOsteoarthrosis is common in 80% of adults between the ages of 55 and 64 yr.

Regardless of process or causes, physical activity is necessary to maintain joint mobility

Body Composition ~ Obesity

Defining obesityMany define obesity based upon appearance alone or the number of pounds one is “overweight”Body composition

Amount of lean body tissue vs. fat tissue

Growth trends in adipose tissueBirth ~ 11% fat in boys and 14% in girlsFat at birth is stored in ~5 billion adipocytesThe number of fat cells continues to increase in childhood

Two growth spurts in fat tissue1 yr. ~ fat % in boys 26%; in girls 28%Puberty for boys; prepuberty and puberty for girls

Greater fat mass in girls during the second growth spurt

With age, fat’s contribution to overall body composition depends upon the size of fat cells, not the number of cells

General growth trendsBody weight reaches its peak at about 45 years of age

Body weight is not a good indicator of body composition

A sedentary lifestyle lends to the observed decrease in lean body mass and an increase in fat mass

Prevalence of obesity among children and adults

Trends in Obesity

Prevalence of obesity in the US ~ raceMexican American and black non-Hispanic women exhibit higher rates of overweight and obesity compared non-Hispanic white womenMexican American men exhibit higher rates of overweight and obesity compared to non-Hispanic blacks and non-Hispanic whites

Obesity in Selected Groups

Prevalence of obesity in the US ~ incomeLow socioeconomic status (income < 130% of the poverty levelHigh socioeconomic status (income > 130% of the poverty level

Prevalence of obesity in the US ~ incomeMen in both groups are likely to become overweight and obeseWomen in low socioeconomic groups are more likely to become overweight or obese compared to women in high socioeconomic groups

Health consequencesHigh blood lipid levelsElevated blood pressureDiabetesCardiovascular disease

Association between childhood and adulthood obesity

Children with a BMI value at the 95th tile for their age and gender have a greater than 60% chance of being obese at age 35 yr.

Selected percentiles for BMI in males from the Second National Health and Nutrition Examination Survey

Body Composition ~ ObesitySelected percentiles for BMI in females from the Second National Health and Nutrition Examination Survey

Field test measures of body fatHydrostatic weighingBod PodDual energy X-ray absorptiometry (DEXA)Skinfold calipers

Body Composition ~ Hydrostatic Weighing

Hydrostatic weighing has been the preferred method for determining percent body fatThis test is not practical as a field-test measureCalculations based upon water displacement

Body Composition ~ Bod Pod

The Bod Pod is fast becoming the new standard in body composition measurementCalculations are based upon air displacementEveryone can be tested ~ disabled, children, elderly

Body Composition ~ Skinfolds

Average sum of triceps and subscapular skinfold thicknesses in boys and girls

Relationship of obesity to motor development and performance

In general, greater amounts of fat are negatively related to activities where the body has to be projected or lifted (tests of vertical jumping, running/walking, running)

Gender Differences in Health-Related Physical Fitness

During the ages of 4-18 yrs.Strong negative correlation between BMI and endurance performanceBoys outperform girls in the distance run, chin-up, and sit-up testsGirls outperform boys in the sit-and-reach test

Factors Associated with Physiological Fitness in Children and

AdolescentsChildren who perform well on tests

of physiological fitness tend to participate

in more community-based activities,

watch less television, receive their

physical education from a specialist,

experience more activities over the

course of a year, and come from

families where physical activity is valued

We are living longer. What is the best way to live a long and

high quality life?

Key Terms

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