Presentation Package

1
chapter 6
chapter
6
Assessing Muscular Fitness
Author name here for Edited books
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Objectives

• Identify methods for assessing muscular strength
  and endurance
• Understand how type of muscle contraction affects
  force production
• Differentiate between advantages and limitations
  of free weights as compared to machine weights
  for assessment
• Learn sources of error in the assessment of
  muscular fitness and how to control them
• Learn procedures for conducting 1-RM tests
• Appreciate challenges of conducting muscular
  fitness assessments for the elderly and children
• Identify methods for assessing functional
  strength of elderly adults

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Muscular Strength

• 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.

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Muscular Endurance

• 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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Types of Contractions

• Static (isometric) no visible change in joint
  angle
• Dynamic visible change in joint angle
• Types of dynamic contractions
• Concentric
• Eccentric
• Isokinetic

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Concentric Contraction

• Force exerted by muscle or muscle group exceeds
  external resistance or load
• Joint angle decreases
• Muscle shortens

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Eccentric Contraction

• Joint angle increases
• Muscle lengthens while contracting
• Serves as a braking mechanism to decelerate body
  segment movement

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Isokinetic Contraction

• 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

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Figure 6.2
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Assessing Strength and Endurance

• Isometric muscle testing strength measured as
  the maximum force exerted in a single contraction
  against an immovable resistance
• MVIC maximal voluntary isometric contraction
• Devices used to assess static strength and
  endurance
• Dynamometers
• Cable tensiometers
• Strain gauges
• Load cells

(continued)
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Assessing Strength and Endurance (continued)

• 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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Assessing Strength and Endurance (continued)

• Hand grip dynamometry for strength
• Adjust hand grip to accommodate clients 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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Back and Leg Dynamometry

• Both use same dynamometer score in kg
• For leg assessment
• 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.
• 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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Dynamometry Normative Values

• 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.
• Can use total dynamometric score to compute
  relative static muscular strength score (divide
  total score by body weight and multiply by 100).

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Table 6.2
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Table 6.3
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Isometric Strength Assessment

• 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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Figure 6.4a
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Figure 6.4b
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Dynamic Strength and Endurance

• 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 doesnt.
• Variable-resistance machines (VRM) were created
  to address this.
• Load changes throughout ROM with VRMs, so it is
  difficult to assess maximal strength.
• Not recommended for strength assessment, but good
  for resistance training programs.

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Free weights Versus Constant-Resistance Machines

• Free weights

• Constant-resistance machines

• Increase neuromuscular coordination
• ROM limited by machine
• No spotter required
• Weight increments may be limited
• Machines may not accommodate all body types

• Increase neuromuscular coordination
• Allow full ROM
• Spotter may be required

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Free-Motion Machines

• 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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Dynamic Strength Testing

• 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.

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Dynamic Endurance Testing

• 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.

(continued)
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Dynamic Endurance Testing (continued)

• Other options
• YMCA bench press test gender-specific resistance
  at set cadence
• Seven-item multiple repetition battery maximum
  of 15 reps at set of clients body mass add
  the number of reps completed over the seven
  items use sum for overall categorization of
  dynamic muscular endurance score

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Isokinetic Assessment

• Assesses strength, endurance, and power.
• Machine generates resistance equivalent to
  clients 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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Omnikinetic Assessment

• Accommodating resistance machine that adjusts to
  both force and velocity generated by client
  (variable force, variable velocity)
• No preset velocity
• 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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Field Test Assessments

• 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
• Trunk curls

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Sources of Error

• Possible reasons for measurement errors in
  fitness testing
• Client factors
• Equipment
• Technician skill
• Environment

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Additional Concepts

• Can estimate 1RM from submaximal tests
• Look for muscle balance upper versus lower body
  agonist versus antagonist left versus right side
• Best to express client strength results in
  relative terms

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Working With Older Clients

• 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

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Functional Testing for Older Clients

• Rikli and Jones (2001) battery assesses physical
  capacity and functional fitness through 2 tests
• 30-second chair stand
• 30-second biceps curls
• These tests have functional application for older
  clients ADLs.
• Be sure to follow standardized technique and
  follow known safety precautions.

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Working With Children

• Children can safely perform 1RM trials.
• Must be closely supervised
• Best results obtained using child-sized equipment
• 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