Chapter 06

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Chapter 06
Assessing Muscular Fitness
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Definition: The ability of a muscle group to
develop maximal contractile force against a
resistance in a single contraction.
Force developed during muscular contraction is
determined by velocity of the contraction.
Maximal force is determined at a velocity of zero.
Maximal force is produced when the limb is not
rotating. As the speed of joint rotation increases,
the muscular force decreases.
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Definition: The ability of a muscle group to exert
submaximal force for extended time periods.
Similar to muscular strength, it can be assessed
for static (isometric) or dynamic contractions.
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Both strength and muscular endurance can be
assessed for static and dynamic muscular
contractions.
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Static (isometric) contractions: no visible
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Dynamic: visible change in joint angle
change in joint angle
◦ Types of dynamic contractions
 Concentric
 Eccentric
 Isokinetic
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Force exerted by muscle or muscle group exceeds
external resistance or load.
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Joint angle decreases
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Muscle shortens
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Joint angle increases
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Muscle lengthens while contracting
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Serves as a braking mechanism to decelerate body
segment movement, or to resist gravity.
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Maximal contraction of muscle or muscle group at
a constant velocity throughout entire range of
motion (ROM).
Specialized machines control velocity of
contraction and adjust external resistance to
match the force produced at degree in the ROM.
Resistance is variable, velocity is constant)
(Electromechanical devices vary the resistance to match the
muscular force produced at each point in the ROM. Thus,
isokinetic exercise machines allow the muscle group to encounter
variable but maximal resistances during the movement.)
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Both concentric and eccentric contractions are
sometimes called isotonic (“iso,” same; “tonic,”
tension). The term “isotonic contraction” is a
misnomer because the tension produced by the
muscle group fluctuates greatly even though the
resistance is constant throughout the range of
motion (ROM).
Thus, the greatest resistance that can be used
during regular, dynamic exercise is equal to the
maximum weight that can be moved at the
weakest point in the ROM.
The fluctuation in muscular
force during isotonic
contractions is due to the
change in muscle length and
angle of pull as the bony lever
is moved, creating a strength
curve that is unique for each
muscle group. For example,
the strength of the knee
flexors is maximal at 160° to
170°.
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Measures of static or dynamic strength and
endurance are used to establish baseline
values before training, monitor progress
during training, and assess the overall
effectiveness of resistance training and
exercise rehabilitation programs
(continued)
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Isometric strength is measured as the maximum
force exerted in a single contraction against an
immovable resistance (i.e., maximum voluntary
isometric contraction, or MVIC in kg or N).
Devices used to assess static strength and
endurance: (see photos in text)
◦ Isometric Dynamometers
◦ Cable tensiometers
◦ Strain gauges
◦ Load cells
◦ Handheld Dynamometers
(continued)
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Hand grip dynamometry for strength:
Adjust hand grip to accommodate client’s hand.
Set dial to zero.
Stand upright and grasp dynamometer.
Arm position varies between protocol selected.
Client squeezes hand grip quickly and as tightly as
possible and then releases the pressure.
◦ Extraneous body motion is kept to a minimum.
◦ Do 3 trials for each hand; 1-minute rest between
trials.
◦ Select best trial for each hand.
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Both use same dynamometer; score in kg
For leg assessment:
◦ Using the back and leg dynamometer, the individual
stands on the platform with trunk erect
◦ Start with knees flexed to 130o to 140o.
◦ Use pronated grip with bar across thighs.
◦ Extend knees but do not engage back muscles to pull bar
straight up.
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For back assessment:
◦ Fully extend knees and keep head and back erect.
◦ Use over-under grip with the bar across the thighs.
◦ Pull bar straight up by rolling shoulders without bending
backward.
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Can use dynamometric scores to determine
static muscular strength:
◦ Add best strength score for right hand, left hand,
legs, and back.
◦ Be sure to convert values to lb.
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Can use total dynamometric score to
compute relative static muscular strength
score (divide total score by body weight and
multiply by 100).
See Tables Next Slides
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Dynamic Muscle Testing: strength measured as
the maximum force exerted in a single
contraction against a movable resistance
Devices used to assess dynamic strength and
endurance:
◦ Free weights
◦ Constant-resistance machines
◦ Variable-resistance machines
◦ Isokinetic machines
(continued)
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Use cable tensiometers or strain gauges.
Follow standardized procedures closely.
Select proper tensiometer based on anticipated
strength score (above or below 100 lb).
Isometric assessments specific for single joint
angle.
Testing of multiple muscle groups is
recommended for overall strength score.
Digital, handheld dynamometers are now
available.
Detailed procedures for digital dynamometry are
in appendix C of textbook.
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Digital, handheld dynamometers are now
available.
Detailed procedures for digital dynamometry are
in Appendix C of textbook.
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Constant-resistance machines or free weights are
best.
However, each only assesses maximal strength of
weakest point in joint ROM.
Why? Mechanical and physiological advantage changes
throughout ROM, but resistance doesn’t.
Variable-resistance machines (VRM) were created to
address this (i.e., lever, cam, or pulley).
Load changes throughout ROM with VRMs, so it is
difficult to assess maximal strength. As the weight is
lifted, the mechanical advantage of the machine
decreases.
Variable-resistance exercise machines, therefore, have
limited usefulness for maximal testing - Not
recommended for strength assessment, but good for
resistance training programs.
Constant-resistance machines
Free weights
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Increase, and require
more neuromuscular
coordination
Allow full ROM
Spotter may be
required
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Increase neuromuscular
coordination
ROM limited by machine
No spotter required
Weight increments may be
limited
Machines may not
accommodate all body
types
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Eliminate many challenges of free weights and
constant-resistance machines
Allow movement in multiple planes
Can allow both constant- and variable-resistance
exercise
Have many adjustable compartments
Must simulate starting and ending body position
of validated muscular tests in order to use those
normative values
Note settings during baseline assessment testing;
use them for follow-up assessment settings.
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One-repetition maximum (1RM): maximum weight
that can be lifted for one complete repetition of
the movement
Involves trial and error in setting weights
Has been applied to all age groups, but use
standardized technique to keep all clients safe.
Spotting for your client is a must.
1RM bench press and leg press are good for
assessing upper body and lower body strength.
Compute relative strength (maximal lift/body
mass) and use normative values. Norms for men
and women are provided in Tables 6.4 and 6.5.
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1. Have your client warm up by completing 5 to 10
repetitions of the exercise at 40% to 60% of the
estimated 1-RM.
2. During a 1 min rest, have the client stretch the
muscle group. This is followed by three to five
repetitions of the exercise at 60% to 80% of the
estimated 1-RM.
3. Increase the weight conservatively, and have the
client attempt the 1-RM lift. If the lift is successful,
the client should rest 3 to 5 min before attempting
the next weight increment. Follow this procedure
until the client fails to complete the lift. The 1-RM
typically is achieved within three to five trials.
4. Record the 1-RM value as the maximum weight
lifted for the last successful trial. The following basic
steps are recommended for 1-RM testing.
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Dynamic Muscle Endurance Tests
Perform multiple repetitions with weight that is
set submaximal load (%1RM) or set %body mass.
Individual should be able to perform 12 to 15
reps of each exercise with weight that is 70% of
1RM.
The YMCA (Golding 2000) and ACSM (2010)
recommend using a bench press test to assess
dynamic muscular endurance of the upper body.
For this absolute endurance test, use a flat bench
and barbell. The client performs as many
repetitions as possible at a set cadence of 30
repetitions per minute.
(continued)
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Other options
◦ Seven-item multiple repetition battery: maximum
of 15 reps at set % of client’s body mass; add the
number of reps completed over the seven items;
use sum for overall categorization of dynamic
muscular endurance score
◦ Table 6.8 provides percentages for each test item,
as well as the scoring system and norms for
college-age men and women.
Dynamic Muscle Testing using Isokinetic and
Omnikinetic Exercise Modes
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Isokinetic dynamometers assesses strength,
endurance, and power.
Machine generates resistance equivalent to
client’s muscular force generation
(accommodating resistance).
Limb moves at constant, preselected velocity.
Can evaluate peak torque, total work, and total
power for each muscle group tested.
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This testing system provides an accommodating
resistance that adjusts to both the force and
velocity output of the individual and is not limited
to a preset velocity of limb movement.
Force and velocity adjust downward as client
begins to fatigue (self-accommodating)
Assesses isokinetic strength and endurance of
both fast-twitch and slow-twitch motor units in
the muscle group.
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In certain field situations, you may not have
access to dynamometers, free weights, or
exercise machines to assess muscular fitness.
As an alternative, you may use calisthenic-type
strength and endurance tests to assess your
client’s strength and muscular endurance.
Dynamic strength tests: Add additional weight
to client and have them perform the desired
movement as a 1RM.
Dynamic endurance tests: maximum number of
reps performed for select calisthenic exercises
◦ Pull-ups
◦ Push-ups (see Table 6.10 for Norms)
◦ Trunk curls (Table 6.11 for Norms)
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Possible reasons for measurement errors in
fitness testing:
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Client factors
Equipment
Technician skill
Environment
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Client factors - Clients with limited or no
prior weightlifting experience need time to
practice each lift to control for the effects of
learning on performance.
Clients should get adequate sleep before
performing these tests, and you should
restrict the use of drugs and medications
that may adversely affect their performance
Motivating clients and rest between lifts are
important.
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Equipment – The equipment used for testing
must match the equipment used to develop
the strength norms of the test.
It is also important to calibrate the
equipment and make sure that it is in proper
working condition prior to testing.
When selecting exercise machines, make
sure that the equipment can be properly
adjusted to accommodate varying limb
lengths and body sizes.
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Technician skill - All strength testing should
be done by qualified, trained technicians
who are knowledgeable about proper lifting
and spotting techniques and familiar with
standardized testing procedures.
Explain and demonstrate the proper lifting
technique and then correct any performance
errors you see as the client practices.
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Environment - The room temperature
should be 70° to 74° F (21° to 23° C) to
maximize subject comfort during testing.
Use a quiet, clean environment with limited
distractions (not an overcrowded weight
room, for example).
Remember to pretest and posttest your
client at the same time of day to control for
diurnal variations in strength.
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Can estimate 1RM from submaximal tests.
Although 1-RM tests can be safely administered
to clients of all ages, sometimes it is preferable to
estimate the 1-RM.
The 1-RM may be underestimated for clients with
little or no exercise experience because they are
unaccustomed to or may be apprehensive about
lifting heavy loads.
You can estimate the 1-RM of your clients from
submaximal muscle endurance tests (see pg. 144)
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Look for muscle balance. Muscle imbalance may
compromise joint stability and increase the risk of
musculoskeletal injury
Muscle balance ratios differ among muscle groups and are
affected by the force-velocity of muscle groups at specific
joints.
To control limb velocity during muscle balance testing, you
will do best to use isokinetic dynamometers. (see chart on pg.
145.)
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The difference in strength between contralateral (right vs.
left sides) muscle groups should be no more than 10% to
15%, and the strength-to-body mass (BM) ratio of the upper
body (bench press 1-RM/BM) should be at least 40% to 60%
of the lower body relative strength (leg press 1-RM/BM)
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Best to express client strength results in relative
terms.
Because strength directly relates to the body mass
and lean body mass of the individual, you should
express the test results in relative terms (e.g., 1RM/BM).
This is especially true in comparing your client’s
score to group norms and in comparing groups or
individuals differing in body size and composition
(e.g., men vs. women or older vs. younger adults).
If you compare the client’s relative strength
scores (from pre- and posttest training), you will
be able to evaluate the change in strength that is
independent of a change in body weight.
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Muscular strength and endurance are
important for maintaining functional
independence and activities of daily living
(ADLs).
You can use 1RM assessments with this age
group.
You may prefer to estimate 1RM from
submaximal loads:
◦ Brzycki (1993) equation and Wathen (1994)
equation are recommended (see pg. 146)
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Rikli and Jones (2001) battery assesses
physical capacity and functional fitness
through 2 tests:
◦ 30-second chair stand
◦ 30-second biceps curls
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These tests have functional application for
older clients’ ADLs.
Be sure to follow standardized technique
and follow known safety precautions. (see
demos, instructions, and norms pgs. 147-150)
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Children can safely perform 1RM trials.
◦ Must be closely supervised
◦ Best results obtained using child-sized equipment
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No support for contention of premature
closure of epiphyseal plates due to strength
training
Follow standard guidelines when testing
1RM:
◦ Be sure to allow for familiarization trial(s)
◦ Focus on proper lifting and breathing techniques
◦ See Testing Protocol, (p.150)

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