In this section, we will evaluate different methods to
measure the health-related physical fitness components.
Aerobic Capacity
Aerobic capacity is a dimension of physical fitness that
relates to the ability to perform sustained exercise and measures the functional
capacity of the cardiorespiratory
system (the heart, lungs and blood vessels). The single most reliable
measure of aerobic capacity is maximum oxygen consumption or VO2max.
In the laboratory, an individual performs a maximal exercise test on an
ergometer or treadmill. While following a specific exercise protocol, the
subject’s expired gasses are monitored with a computerized gas analysis system.
This testing equipment is also described in Section 13.3. VO2max
is achieved when the work rate is increased but the oxygen consumption does not
increase or has reached a plateau, the respiratory exchange ratio (RER) is
greater than 1.1, and/or heart rate is near age-predicted maximal levels.
Figure 14.5
Aerobic capacity testing on a treadmill.
Field methods include ways to assess aerobic capacity and
are feasible for mass testing. Generally, field methods require little equipment
and are less expensive in time and costs than laboratory methods. There are a
variety of different field protocols to measure aerobic capacity such as:
·
Maximal distance run tests
o
12-minute run/walk test
o
1.5-mile run test
o
20-meter shuttle run (PACER)
·
Step tests
·
Walk or jog tests
o
Rockport 1-mile walk test
o
BYU 1-mile jog test
Distance run tests, such as the 12-minute run or 1.5-mile run, are very convenient in physical education settings as entire classes can be tested in a short amount of time. Most need only a track and a stop watch to administer.
The PACER test is slightly different as it is performed similar to a shuttle run.
Required equipment includes a 20 meter area wide enough for all students to run, cones for marking area, CD player and the PACER CD.
The PACER CD is played during the test and the students start and stop to a series of beeps.
Students run a 20 meter distance before a beep sounds and continue back-and-forth at a progressively faster pace until they cannot keep up.
The PACER allows 9 seconds to cover the 20 meters at the start and decreases by .5 seconds every minute.
The test is completed when the student fails to reach the 20 meter line by the beep for a second time.
A partner counts the number of laps
a student completes and records the score.
Aerobic capacity can be estimated without performing exercise tests.
Jackson et al. (1990) developed multiple regression equations to estimate VO2max from data that is collected from participants without exercising.
The required variables include age, gender, body composition (BMI or skinfolds), and self-reported physical activity.
These equations had reasonable validity coefficients and the standard error of estimation was +/-5.7 ml/kg/min, which is comparable to submaximal and field exercise tests.
These non-exercise equations are especially feasible for mass testing, but not in highly trained individuals as the error rate increases.
The upper 5% of highly trained men and
women should be tested utilizing an exercise test.
Body Composition
Health-related fitness and training programs are designed to control body weight and body composition.
Body composition is the classification of the body into fat weight and fat-free weight or lean mass.
Percent body fat is simply the proportion of total weight that is fat weight.
The original gold-standard of body composition is the underwater weighing.
This is a laboratory technique that first requires weighing a person outside the tank, then immersing them totally in water and weighing them again.
The densities of bone and muscles are higher than water, and fat is less dense than water.
So a person with more bone and muscle will weigh more in water than a person with less bone and muscle, meaning they have a higher body density and lower percentage of body fat.
The volume of the body is calculated and the individual's body density is determined by using standard formulas.
Then body fat percentage is calculated from body density
using standard equations (either Siri or Brozek ).
A DXA scan (Dual energy x-ray absorptiometry) has surpassed underwater weighing in popularity in the last few years because of its accuracy and ease in measurement.
DXA uses a whole body scanner that consists of two different low-dose x-rays.
The attenuation or changes of those rays as they pass through bone, organs, muscle and fat provide estimates of bone mass, lean mass, and fat mass.
Estimates of total percent body fat have a reported
standard error of less than 2%.
Field methods of body composition are relatively inexpensive and can be performed fairly quickly.
The most popular field method is the skinfold technique.
Skinfold calipers are used to measure the thickness of a skinfold (or fatfold) at specific body sites.
Accuracy of skinfold measures are determined by the calipers and using trained technicians to perform the skinfold measurements at specific body sites.
Prediction of body fat from skinfolds involves the skinfold measurements, participant data such as gender and age, and a multiple regression equation.
Different equations use different skinfold sites, so look at the equations closely.
The YMCA skinfold test uses
the abdomen, ilium, triceps and thigh sites, while the FITNESSGRAM test utilizes
the triceps and calf skinfold sites.
Muscular Strength
Muscular strength is the maximum force that a muscle group
can exert. Muscular contractions are defined and categorized by movement and
speed and are as follows:
·
Concentric contraction – the muscle generates
force as it shortens.
·
Eccentric contraction – the muscle generates
force as it lengthens.
·
Isometric contraction – the muscle generates
force but remains static in length and causes no movement.
·
Isotonic contraction – the muscle generates
enough force to move a constant load at a variable speed through a range of
motion.
·
Isokinetic contraction – the muscle generates
force at a constant speed through a range of motion.
In the laboratory, measuring muscular strength can require expensive and sophisticated equipment with very precise testing protocols. Laboratory assessments are the most valid test, but are difficult to administer to a large population.
Isometric strength testing has been popular due to the flexibility in testing protocols and relatively inexpensive equipment.
There are standardized protocols for arm, shoulder, torso and leg strength tests utilizing equipment consisting of a platform, chain, load cell and a digital recorder.
Isokinetic strength testing is also a popular laboratory assessment.
A computerized isokinetic dynamometer measures torque through a defined range of motion while keeping the speed of movement constant.
This yields a torque curve for the muscle group through the range of motion.
The reliability of isokinetic
testing is high as long as the same protocol and equipment is used.
Isotonic strength testing often uses the same equipment as used in a strength training program and is the most popular in the field assessment of strength.
This familiarity with the equipment makes testing go quickly and utilizing existing equipment minimizes costs.
Testing protocols usually consist of a few warm-up sets and then gradual increases in weight until 1-RM is reached.
Between lifts, have the participant rest for approximately 2 minutes to prevent fatigue.
Both free-weights and machines can be utilized for
testing, but make sure to have spotters for safety.
A summary of each testing method with relative strengths
and weaknesses are listed in Table 14.1.
Table 14.1 A
Comparison of Strength Testing Methods
|
Method |
Strengths |
Weaknesses |
|
Isometric |
1.
Moderately inexpensive
2.
Can be used to test a variety of
different muscle groups.
3.
Closed kinetic chain.
4.
Strong research base for pre-employment
testing.
5.
Normative data available.
6.
Easy to learn how to administer the
tests. |
1.
Only one joint angle is tested at a time.
2.
Does not provide a torque strength curve
3.
Cannot measure dynamic contractions. |
|
Isotonic |
1.
Very inexpensive.
2.
Various equipment can be used.
3.
Closed or open kinetic chain.
4.
Tests often mimic strength training
program.
5.
Quick, testing protocol.
6.
Easy to learn how to administer the
tests. |
1.
Cannot measure “true maximum”.
2.
Cannot obtain a strength curve.
3.
Risk of injury
4.
Different equipment affects the score and
you need equipment specific norms.
5.
Can be difficult to find 1-RM in
untrained individuals. |
|
Isokinetic |
1.
Can obtain strength curves for many
different speeds.
2.
Can obtain both concentric and eccentric
contractions.
3.
Multiple ways to express data.
4.
Valuable in the rehabilitation process. |
1.
Very expensive equipment.
2.
Open kinetic chain
3.
Velocity of contraction affects torque
output; need norms for various speeds. |
Chart taken from Measurement for Evaluation in Physical
Education and Exercise Science by Baumgartner, et al., p. 238.
Muscular Endurance
Muscular endurance is the ability to persist in physical activity or to resist muscular fatigue.
As with muscular strength assessments,
isometric, isotonic and isokinetic protocols can be used. In the laboratory
isokinetic dynamometers can be programed for a set number of repetitions (for
example 30) and the torque produced is evaluated over the total number of
repetitions. There are numerous ways to represent the data depending on the
particular research questions being answered.
In the field, push-ups and a modified pull-up test are popular arm and shoulder endurance tests.
Technically a regular pull-up test can be used to assess muscular endurance, but the individual must be able to perform multiple pull-ups.
Since many individuals cannot do a single pull-up, the modified pull-up test is used to make the test a true endurance measure.
Specific protocols vary but either the individual will do as many repetitions as possible in a set time period (60-90 seconds) or follow a specified pace performing for as long as they can maintain technique and pace.
Abdominal muscular endurance is commonly measured by a curl up or half sit-up test.
These protocols are similar to the push-up and modified pull-up tests
regarding time and pace. The total
number of repetitions is recorded as a measure of muscular endurance.
Flexibility
Flexibility is the range of movement about a joint or group
of joints. Individual differences in flexibility depend on physiological
characteristics that influence the extensibility of the muscles and ligaments
surrounding a joint. Because flexibility is specific to a joint and its
surrounding tissues, there are no valid tests of general flexibility.
In the laboratory, flexibility can be assessed by
·
Goniometry
·
Visual estimation
·
Radiography (x-rays)
·
Photography
·
Linear measurements
Goniometry is the most feasible method of clinical assessment of flexibility and is accomplished by using a large protractor to measure the extreme points in a joint’s range of motion.
This measurement technique is often used in physical therapy and sports medicine as a diagnostic or therapeutic measure to determine the functional status of a patient with a musculoskeletal injury or disability.
Radiography is often touted as the most
reliable and valid method to measure flexibility, but the expense and radiation
exposure limits the feasibility of utilizing this method.
In the field, practitioners most commonly measure the range of motion of the trunk.
Low back pain is a prominent health problem in the United States and in theory the lack of flexibility in the low back should be associated with low back pain.
This relationship is not well understood and clinical research is ongoing as flexibility is not empirically related to low back pain.
The sit-and-reach test is a universally used test to measure trunk flexion and specifically measures flexibility of the low back and hamstring musculature.
Instructions for the sit-and-reach test are included in the Adult Fitness Test and FITNESSGRAM reading.
Health-related fitness batteries almost
unanimously measure trunk flexion by sit-and-reach for populations of both
children and adults.