Kin 4310 Test 3

Exercise

" A sub-category of physical activity, that is planned structured purposeful and repetitive."

Physical activity

"Any bodily movement produced by the skeletal muscles that results in energy expenditure."

Field tests

12-Minute Run/Walk Test VO2max = (Distance in miles - 0.3138) / 0.0278 1.5-Mile Run Test VO2max = 3.5 + (483 / time in minutes) 20-meter Shuttle Run (PACER) VO2max = -32.678 + 6.592 (max speed in km/h)

Dietary Assessment - Methods

24 hour recall Food record/diary Weighed Unweighed Food frequency questionnaires Diet history Duplicate diet collection

Measuring Physical Activity

30+ different instruments and/or methods Pros and cons of each, depending on what information you are trying to capture Characteristics assessed: Frequency Intensity Duration

DFW

= number of data points - number of groups = N - k

DFB

= number of groups - 1 = k - 1

Independent T-test

A hypothesis test that is used to determine if there is a significant difference between two groups

Health

Absence of: Physical pain Physical disability Conditions likely to cause death Emotional well-being Satisfactory social functioning

Methods to Assess PA Objective Measures

Accelerometers Marker of movement Heart rate monitoring Physiological response to PA Pedometers Number of steps taken Direct observation Observed or videotaped GPS systems Newer application; measures population movement

Food Frequency Questionnaires

Assesses energy and/or nutrient intake by determining frequency of consumption of a limited number of foods known to be major sources of the dietary component under investigation Lists approximately 100 food or food groups May ask for indication of portion size Portion numbers and sizes are statistically analyzed to estimate nutrient intake

Diet History

Assesses subject's usual dietary intake over an extended period of time Collect general information on subject's health habits Question subject about usual eating patterns Verify accuracy of data provided Subject also completes d-day food record

Diet History Strengths

Assesses usual nutrient intake Can detect seasonal changes Data on range of nutrients can be collected Correlates well with biochemical markers of intake (i.e. - protein intake and nitrogen excretion

Pedometers

Assesses walking via number of steps taken Must be calibrated correctly to provide valid & reliable data Fixed to waistband Small-light-unobtrusive Display: Steps Distance Kcals Step Targets: Adults: 10,000 steps/day Children: 127 steps/min60 mins = 8000 steps/day

Duplicate Food Collection Strengths

Avoids coding errors and errors involved in the use of food composition tables Can be used for nutrients and contaminants found in very small amounts for which food composition databases are incomplete

Skinfold Thickness

Based on the principle that approximately half of the body's fat tissue is directly beneath skin Reliable measurements can give a good indication of percent body fat Skinfold test is done with pressure calipers Several sites are measured and percent fat is estimated from the sum of the three sites All measurements should be taken on the right side of the body

Health-Related Physical Fitness

Body composition Aerobic fitness Flexibility Muscular endurance Muscular strength Heart disease, diabetes... Heart disease, ... Low back pain Chronic fatigue Function, independence

Storage fat

Body fat in excess of essential fat; stored in adipose tissue

Lean body mass

Body weight without body fat

Food Frequency Questionnaires Strengths

Can be self-administered Scannable computer scoring available Inexpensive May be more representative of habitual intake Allows for examination of diet-disease relationships

CT

Computed tomography (CT) Measures regional adiposity by imaging multiple cross-sectional slices Measures fat layers within body cavity, limbs or organs Sequential images are segmented into adipose and nonadipose tissue pixel values measured in Houndsfield units (HU) Uses higher-dose X-ray energy Radiation exposure can be a drawback Procedure is simple; time required depends on number of slices taken

Heart Rate Monitors Limitations

Cost (large samples) Data attrition Discomfort over long periods Age, sex, training status affect HR No information on context of physical activity

Mortality

Death rate = # of deaths in pop in a given time/ # of ppl in pop in a given time Average lifespan = # of years one is expected to live

Direct Observation Strengths

Detailed quantitative & qualitative data Describes PA in real time Low financial cost Computer software allows for immediate recording & analysis of data

Testing the significance of a correlation

Determine critical values of r Table B4 in book Calculate p-values of r df=n-2

Food Record/Diary Strengths

Does not rely on memory Can provide detailed data on intake and eating habits Multiple day data more representative of usual intake Valid up to 5 days

ANOVA Assumptions

Each group is comprised of a randomly selected sample Scores in each group are normally distributed The variances of each group population are homogenous

How to measure aerobic fitness?

Exercise testing Oxygen consumption Power output Field tests 12-minute run/walk Generalized 1-mile run/walk Shuttle run

Variance WITHIN groups

How spread out is the data in each group relative to its group mean? Square the differences between every data point and its group mean, (X - Xi)2 Sum the squares, SSw = S(X - Xi)2

Morbidity

Incidence = # of new cases of dz in a given time/ # of ppl in pop in a given time Prevalence = # of cases of a dz in a pop/# of ppl in pop

Health Status

Individual Health Status Observer (e.g., physician) Self-report Health of a population Life expectancy at birth Death rate Prevalence of disease Pollution

Air Displacement

Individual sits inside small chamber Computerized pressure sensors determine the amount of air displaced by the person Body volume is calculated by subtracting the air volume with the person inside the chamber from the volume of the empty chamber (air in the lungs is taken into consideration) Body density and percent body fat are then calculated Less cumbersome to administer Takes only about 5 minutes

Physical Activity Questionnaires

International Physical Activity Questionnaire (IPAQ) Physical Activity Questionnaire for Adolescents (PAQ-A) Leisure Time Exercise Questionnaire (LTEQ)

Two-way ANOVA

Like one-way ANOVA, but there are two independent factors Used when we want to learn about the main effects of each factor individually, but also want to understand how they interact a.k.a. Factorial ANOVA

Intensity

METs: multiples of the metabolic equivalent of sitting quietly for one hour Sedentary < 1.5 METs Light 1.5 < 3.0 METs Moderate 3 - 6 METs Vigorous > 6 METs

Mean Sum of Squares

MSb = SSb / dfb

MRI

Magnetic resonance imaging (MRI) Used primarily by research and medical facilities 2nd "gold standard" technique Uses high powered magnets and imaging software Measures total and regional adiposity Safe; no problems with radiation exposure, etc. Procedure can be time consuming and is very expensive

Food Frequency Questionnaires Limitations

May not represent typical food or portion sizes consumed Relies on ability of subject to describe diet

Accelerometers

Measure accelerations of the human body Record activity patterns over a period of time Benefits: small, non-invasive, large storage capacity, can be used widely in field settings Different types: Actigraph (or CSA) - most commonly used Caltrac - estimates energy expenditure Tritrac - newer, measures PA in 3 planes

Direct Observation

Measure behavioral aspects of physical activity Provides information on specific activities occurring in a variety of settings over time Quantitative & qualitative information Useful with younger children Requires trained observers Pen and paper instruments

Heart Rate Monitors

Measures cardiorespiratory response to physical activity Transmitter and belt worn around the upper body Data commonly displayed on a wrist receiver Downloaded via interface for analysis

Heart Rate Monitors Strengths

Measures physiological relationship with energy expenditure Valid & reliable in lab & field Describes intensity of PA Easy & quick for data collection & analyses

Essential fat

Minimal amount of body fat needed for normal physiological functions; constitutes about 3-5% of total weight in men and 8-12% in women

Body Mass Index (BMI)

Most common measure of body composition Incorporates height and weight to estimate critical fat values at which disease risk increases BMI = Body Mass / Stature2 Always expressed in metric units (kg/m2 )

Dual energy X-ray absorptiometry (DXA)

Most frequently used by research and medical facilities Considered the "gold standard technique" for body composition assessment Uses low-dose beams of X-ray energy Measures fat mass, fat free mass, and bone density Procedure is simple; takes only 15 minutes to administer Safe; no problems with radiation exposure, etc.

Methods to Assess PA Subjective Measures

Physical activity logs (PALS) 24 hour recall 7 day recall Previous month recall Previous year recall Questionnaires All are self-administered or interviewer administered, either in-person or on telephone

Waist-to-Hip Ratio

Predicts disease risk according to distribution of adiposity ("apple" vs. "pear" shape)

Waist Circumference

Predicts disease risk according to region of adiposity (waist versus other areas)

Aerobic Power Output

Rate of mechanical work used to define exercise intensity Usually expressed in Watts Cycle ergometers (arm or leg) Treadmills

Girth Measurements

Requires a standard measuring tape Women: Upper arm, hip, and wrist measurements (cm) Look up constants based on measurements and determine body density and percent fat according to predicting equations Men: Waist and wrist measurements (inches) Use table for percent body fat estimate

Food Record/Diary Limitations

Requires high degree of cooperation Subject must be motivated and have average literacy level Subjects willing to complete food records may not be typical Quality of record declines in relation to the number of days studied Reactive

24 Hour Recall Strengths

Requires only 20-30 minutes Fairly inexpensive Provides detailed quantitative and qualitative data Low subject burden Low reactivity

t-test for dependent means

Requires paired data Two sets using the same measurement scale t-test is based on these difference values Examples: Body mass index is measured before and after a special diet program Grip strength is measured in the dominant hand and the non-dominant hand

24 Hour Recall

Requires trained interviewer Interviewer helps subject remember all foods consumed and assists in determination of portion sizes Common technique: Interviewer asks what subject first ate and drank upon waking THAT day, and works forward to time of interview Interviewer then begins at point exactly 24 hours ago and works forward to time of waking

Estimating Food Portion Sizes

Significant problem with interpretation of portion sizes Subjects should give as accurate description as possible, possibly by comparing to other objects (i.e. - deck of cards) Food models or pictorial representations can also be used Subjects can also be taught how to record net weight or volume on food labels and report proportion of the food that was consumed

Bioelectrical Impedance

Simple to administer, but accuracy is questionable Sensors are applied to the skin and a weak electrical current is run through the body to estimate body fat, lean body mass, and body water Based on the principle that fat tissue is a less-efficient conductor of an electrical current The easier the conductance, the leaner the individual Body weight scales with special sensors on the surface may also be used to perform this procedure Hydration status can influence results

Correlation studies

Step 1: Calculate test statistic, r Step 2: Look up the critical value of r Step 3: Compare your r to rcrit Step 4: Reject the null hypothesis?

Unweighed/Estimated Food Record

Subject cooperation and literacy skills required Less invasive - tends to be more acceptable to subjects Some accuracy lost, but often balanced by better subject participation and adherence

Food Record/Diary

Subject records, at time of consumption, the types and amounts of food and beverages consumed for a period of time ranging from 1-7 days Weighed food record Food and beverages weighed Preferred method - considered more accurate Unweighed/estimated food record Portions estimated using household measures such as cups, teaspoons, tablespoons, etc.

Duplicate Food Collection

Subjects collect identical portions of all food and beverages consumed over a specified period of time Duplicate portions are then chemically analyzed for nutrient content

F-score

The F- distribution is not symmetric; it is skewed positively. The values of F can be 0 or positive; they cannot be negative. The F-distribution changes shape with respect to degrees of freedom

Aerobic Fitness

The ability of the heart, lungs and blood vessels to supply oxygen to the working muscles The ability of the muscles to use the available oxygen A major component of fitness! There is a significant relationship between aerobic fitness and mortality rates

Metabolic Equivalents (METs)

The amount of oxygen used at rest 1 MET = 3.5 ml·kg-1·min-1

Body Composition

The different components that make up the human body Fat Muscle Bone Important in assessing health status and disease risk

Dependent T-test

The t-test can also be used when there is only one group of subjects, and they are tested under two conditions

Hydrostatic Weighing Drawbacks

Time consuming Not feasible to test large number of people Requires measurement of residual lung volume (if unknown, can be estimated) Difficult to perform on the aquaphobic

Diet History Limitations

Time consuming and expensive Labor intensive - requires highly trained interviewers and complex coding systems May overestimate nutrient intake Requires cooperative subject with ability to recall usual diet

Direct Observation Limitations

Time-intensive training Time & labour intensive data collection Limited sample sizes Observer presence (reactivity) Limited validation against physiological criteria

24 Hour Recall Limitations

Time-intensive training Time & labour intensive data collection Seldom representative of usual intake Under/over reporting can occur Requires cooperative subject; data can be withheld or altered

Physical Activity Level (PAL)

Total energy expenditure in 24 hours/Basal metabolic rate

Variance BETWEEN groups

Total variance is based on all data from all groups Variance BETWEEN groups represents the spread of the group means

Hydrostatic Weighing

Underwater weighing Most common technique used for decades A person's "land" weight is compared with underwater weight Fat is more buoyant than lean tissue Most other indirect techniques have been validated against hydrostatic weighing

Determine critical value of F for a = 0.05

Use table B3 on page 356 You need: df for the Denominator df for the Numerator Type I Error rate

Nonexercise estimates

Uses age, measures of body composition and physical activity to estimate VO2max

Duplicate Food Collection Limitations

Very expensive Considerable subject burden May underestimate intake

Percent body fat (%BF)

Weight of fat in the body relative to the person's total weight

Interaction effects

When the effect of one factor depends on another factor E.g. There is an interaction between IRRIGATION and FERTILIZER on TREE GROWTH

Main effects

When there is a significant difference between different levels of a factor E.g. There is a main effect of DIET on BMI There is a main effect of AGE on BMI There is a main effect of GENDER on STATURE

A large value of F represents

a low probability that the data could have resulted if H0 is true

Disability-Adjusted Life Years (DALY)

a measure of overall dz burden, expressed as the cumulative # of years lost due to ill-health, disability or early death

Analysis of variance (ANOVA)

a method for testing the hypothesis that three or more population means are equal.

Factors

a variable that separates data into groups. E.g.: Gender: MALE or FEMALE Diet: HIGH-FAT or LOW-FAT Treatment: PLACEBO, LOW DOSE, HIGH DOSE Age: YOUNG, MIDDLE-AGED, ELDERLY Physical Activity Level: SEDENTARY, ACTIVE

Critical values of F are calculated based on

degrees of freedom (size of dataset)

An excessively large F test statistic

evidence against equal population means.

Direct techniques

involve looking inside the body and measuring the different tissues by volume (or area) Dual energy X-ray absorptiometry (DXA) Magnetic resonance imaging (MRI) Computed tomography (CT)

Indirect techniques

involve measurements outside or on the surface of the body to estimate what is inside: Hydrostatic weighing Air displacement Skinfold thickness Bioelectrical impedance BMI, WC, WHR Girth measurements

Calculating F

k = number of groups N = total number of data points Xi = the mean value of each group then we calculate... SStotal = Sum of squares of all data SSw = Sum of squares within groups SSb = Sum of squares between groups df = degrees of freedom MSw = Mean sum of squares within groups MSb = mean sum of squares between groups F

You need these for T-test

n: number of pairs of measurements SD: The sum of all the differences SD2: The sum of the squares of all the differences

Sum of squares WITHIN groups

represents the spread of each data point within its own group Subtract each data value from its own group mean

When the variance WITHIN groups decreases

the variance BETWEEN groups becomes more apparent. F = MSb/MSw F increases

When the variance BETWEEN groups decreases

the variance WITHIN groups becomes more apparentF = MSb/MSw F decreases

If there is a significant effect of treatment

then MSbetween will be large relative to MSwithin and F will be large

If there is no effect of treatment

then MSbetween will be relatively small and F will be small

If F > Fcrit

there is an effect of treatment, and we can reject the null hypothesis