Muscular Strength and Muscular
Endurance Assessments and
Exercise Programming for
Apparently Healthy Participants
Chapter 4
Copyright © 2014 American College of Sports Medicine
Introduction
• Muscular strength and muscular endurance are two
components of health related fitness.
• Resistance training has become a fitness trend.
• Can improve quality of life for all ages.
• Recommendations by ACSM now recognized by WHO for
health benefits of resistance training.
• Reductions in mortality, CVD risk factors and improved
body composition are some of the benefits gained.
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Exercise is Medicine: Reduction in BP
• CV exercise has been noted for its ability to lower resting
blood pressure.
• Resistance training has been discouraged for its potential
to increase BP.
• Meta-analysis performed by Carnelissen et al. revealed
that resistance training decreased BP with a mean
reduction of 3.9 mm Hg in normo- and prehypertensives.
• Hypertensives saw approximately the same mean
decrease; however, it was not statistically significant.
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Additional Benefits
• Resistance training has been proven to cause increases
in bone mass, counteracting the degenerative disease of
osteoporosis.
• Enhances physical function.
• Helps to decrease age-related weight gain.
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Resistance Training
• A specialized method of physical conditioning which
involves the progressive use of wide range of resistive
loads and a variety of training modalities designed to
enhance muscular fitness.
• The term resistance training should be distinguished from
bodybuilding and powerlifting, which are competitive
sports.
Copyright © 2014 American College of Sports Medicine
Structure/Function
• 600+ Skeletal muscles, varying in shape and size
• Sarcomere: smallest contractile unit made of proteins
• Myofibril: made of many sarcomeres
• Single muscle fiber: made of many myofibrils
• Fascia: connective tissue, surrounding muscles providing
stability while being flexible.
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Structure/Function (cont.)
• Agonists: primary joint movers
• Synergists: accessory joint movers
• Antagonists: muscles that oppose movement
• Only muscles that are used during exercise will adapt to
the stress.
• Different training loads stimulate different muscle fibers.
Copyright © 2014 American College of Sports Medicine
Fiber Types
• Two types of muscle fibers:
– Type I (Slow Twitch): high oxidative capacity, a
lower contractile force capability and better for
endurance activities.
– Type II (Fast Twitch): high glycolytic capacity, a
higher contractile force capability and better for
strength and power activities.
• Ratio of the two fiber types vary, and are largely
dependent on heredity.
– Fiber type cannot be changed, however, training can
alter their involvement in movements.
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Recruitment
• Muscle fibers are innervated by a motor neuron and this
neuromuscular gathering is called a motor unit.
• The size of a motor unit as well as the number of fibers
within a motor unit varies within different muscles.
• Size Principle: Recruitment occurs from largest groups to
smallest groups depending on demands.
• Smaller or low-threshold motor units (mostly type I
fibers) are recruited first and larger or high-threshold
motor units (mostly type II fibers) are recruited later.
Copyright © 2014 American College of Sports Medicine
Copyright © 2014 American College of Sports Medicine
Recruitment in Training
• Training in the 4 to 6 RM range will recruit higher levels
of units than training in a 12 to 15 RM range.
• Even with heavy loads, the lower threshold units are still
recruited first as higher levels are recruited as necessary.
• Periodization is based on the principle that different
training loads and power requirements recruit different
types and numbers of motor units.
Copyright © 2014 American College of Sports Medicine
Types of Muscle Action
• Concentric contractions occur when the muscles are
shortening.
• Eccentric contractions occur when the muscles are
lengthening.
• Isometric, or static, action occurs when the muscle is
loaded, however no movement at the joint takes place.
• Static action typically happens during the “sticking point”
of an exercise when the force produced by the muscle
equals the resistance.
Copyright © 2014 American College of Sports Medicine
Copyright © 2014 American College of Sports Medicine
Muscle Action
• The highest force produced occurs during an eccentric
muscle action.
• Maximal force produced during an isometric muscle
action is greater than seen during a concentric
contraction.
• As the velocity of movement increases, the amount of
force that is generated decreases during a concentric
muscle contraction and increases during an eccentric
muscle action.
• Progression during eccentric actions must occur slowly to
reduce risk of muscle strain.
Copyright © 2014 American College of Sports Medicine
Copyright © 2014 American College of Sports Medicine
Copyright © 2014 American College of Sports Medicine
Benefits of Assessment
• Can be assessed by a variety of laboratory and fieldbased measures.
• Provide valuable information about an individual’s
baseline fitness.
• Highlight a client’s progress and provide positive
feedback that can promote exercise adherence.
• Adults who undergo fitness testing should complete a
health history questionnaire and individuals at
cardiovascular or orthopedic risk should be identified.
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Muscular Fitness Tests
• Specific to the muscle groups being assessed, the
velocity of movement, the joint range of motion and the
type of equipment available.
• Tests need to be individualized for each client.
• Each client should have a familiarization session before
participating.
• Large amplitude dynamic movements (also known as
dynamic stretching) and test-specific activities should
precede muscular fitness testing.
Copyright © 2014 American College of Sports Medicine
Copyright © 2014 American College of Sports Medicine
Muscular Fitness Tests (cont.)
• Initial assessment of muscular fitness and a change in
muscular strength or muscular endurance over time can
be based on the absolute value of the weight lifted or the
total number of repetitions performed with proper
technique.
• When strength comparisons are made between
individuals the values should be expressed as relative
values (per kilogram of body weight).
Copyright © 2014 American College of Sports Medicine
Assessing Muscular Strength
• The 1 RM is the standard muscular strength assessment
– The heaviest weight that can be lifted only once.
– Assumes proper technique.
• Proper familiarization is necessary and increases
reliability of testing.
• A 10 RM can also be used to assess muscular strength.
Copyright © 2014 American College of Sports Medicine
How to Assess 1 RM
• Warm-up for 5 to 10 minutes with low-intensity aerobic
exercise.
• Perform a specific warm-up with several repetitions with a light
load.
• Select an initial weight that is within the subject’s perceived
capacity (~50% to 70% of capacity).
• Attempt a 1 RM lift; if successful rest ~3 to 5 minutes before
the next trial.
• Increase resistance progressively (e.g., 2.5 to 20 kg) until the
subject cannot complete the lift. A 1 RM should be obtained
within four sets to avoid excessive fatigue.
• The 1 RM is recorded as the heaviest weight lifted successfully
through the full ROM with proper technique.
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Assessing Muscular Endurance
• Muscular endurance is the ability to perform repeated
contractions over a period of time as is typically assessed
with field measures.
• These tests can be used independently or in combination
with other tests of muscular endurance to screen for
muscle weaknesses and aid in the exercise prescription.
• Certain populations (e.g., overweight) may find these
tests difficult to perform.
– Poor results obtained during testing may discourage
further participation.
Copyright © 2014 American College of Sports Medicine
Copyright © 2014 American College of Sports Medicine
Fundamental Principles
• Four fundamental principles that determine the
effectiveness of all resistance training programs:
– (a) Progression, (b) Regularity, (c) Overload, and
(d) Specificity.
• P.R.O.S.
– Initial level of fitness, heredity, age, gender,
nutritional status, and health habits (e.g., sleep)
all influence the rate and magnitude of adaptation.
Copyright © 2014 American College of Sports Medicine
Progression
• The demands placed on the body must be continually and
progressively increased over time to achieve long-term
gains in muscular fitness.
• Over time, physical stress on the body must become
increasingly challenging.
• This principle is particularly important after the first few
months of resistance training when the threshold for
training-induced adaptations in conditioned individuals is
higher.
Copyright © 2014 American College of Sports Medicine
Progression (cont.)
• A reasonable guideline for a beginner is to increase the
training weight about 5% to 10% per week and decrease
the repetitions by 2 to 4 when a given load can be
performed.
• Two plus two rule: once a client can perform two or more
additional repetitions over the assigned repetition goal on
two consecutive workouts, weight should be added to the
exercise during the next training session.
Copyright © 2014 American College of Sports Medicine
Frequency
• Resistance training must be performed regularly several
times per week in order to make continual gains in
muscular fitness.
• Two to three training sessions per week on
nonconsecutive days is reasonable for most adults.
• Proper recovery is still crucial.
• Long-term gains in muscular fitness will be realized only
if the program is performed on a regular basis.
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Overload
• In order to enhance muscular fitness, the body must
exercise at a level beyond that at which it is normally
stressed.
• Overload is typically manipulated by changing the
exercise intensity, duration, or frequency.
Copyright © 2014 American College of Sports Medicine
Specificity
• Refers to the distinct adaptations that take place as a
result of the training program.
• The principle of specificity is often referred to as the
SAID principle (specific adaptations to imposed
demands).
• The adaptations that take place in a muscle or muscle
group will be as simple or as complex as the stress
placed on them.
• Important that exercises performed are consistent with
the target activity (i.e., a certain sport).
Copyright © 2014 American College of Sports Medicine
Program Design Considerations
• Programs should be based on a participant’s health
status, current fitness level, personal interests and
individual goals.
• Identify “at-risk” persons and those who may need
medical clearance.
• Consider current fitness status and previous exercise
experience.
• As individuals gain experience with resistance training,
more complex programs are needed in order to make
continual gains in muscular fitness.
Copyright © 2014 American College of Sports Medicine
Types of Resistance Training
• Dynamic constant external resistance (DCER)
• Variable resistance training
• Isokinetics
• Plyometrics
Copyright © 2014 American College of Sports Medicine
DCER
• Most common method of resistance training for
enhancing muscular fitness.
• Describes a type of training in which the weight lifted
does not change during the lifting (concentric) and
lowering (eccentric) phase of an exercise.
• Different types of training equipment, reps and sets can
be used in DCER training.
• Commonly used to enhance motor performance skills and
sports performance.
Copyright © 2014 American College of Sports Medicine
DCER (cont.)
• The weight lifted does not change throughout the ROM
• The heaviest weight that can be lifted throughout a full
ROM is limited by the strength of a muscle at the
weakest joint angle.
• DCER exercise provides enough resistance in some parts
of the movement range but not enough resistance in
others.
• To overcome this, variable resistance machines provide a
specific movement path that makes the exercise easier
to perform.
Copyright © 2014 American College of Sports Medicine
Isokinetics
• Dynamic muscular actions that are performed at a
constant angular limb velocity
• Used by physical therapists and certified athletic trainers
for injury rehabilitation
• The speed of movement—rather than the resistance—is
controlled during isokinetic training
• The best approach is to develop increased strength and
power at different movement speeds.
Copyright © 2014 American College of Sports Medicine
Plyometric Training
• Characterized by quick, powerful movements that involve
a rapid stretch of a muscle (eccentric) immediately
followed by a rapid shortening of the same muscle
(concentric).
• The amount of time it takes to change direction from the
eccentric to the concentric phase of the movement is a
critical factor in plyometric training.
• This time period is called the amortization phase as
should be as short as possible (<0.1 second) to
maximize training adaptations.
Copyright © 2014 American College of Sports Medicine
Copyright © 2014 American College of Sports Medicine
Plyometric Training (cont.)
• Plyometric exercises can place a great amount of stress
on the involved muscles, connective tissues, and joints.
• This type of training needs to be carefully prescribed and
progressed to reduce the likelihood of musculoskeletal
injury.
• The importance of starting with basic movements or
establishing an adequate baseline of strength before
participating in a plyometric program should not be
overlooked by the HFS.
Copyright © 2014 American College of Sports Medicine
Plyometric Training (cont.)
• It is reasonable for individuals to begin plyometric
training with one or two sets of six to eight repetitions of
lower intensity drills and gradually progress to several
sets of higher intensity exercises.
• In order to optimize training adaptations, performance of
more than 40 repetitions per session appears to be the
most beneficial plyometric training volume.
Copyright © 2014 American College of Sports Medicine
Modes of Resistance Training
• Decisions should be based on an individual’s health
status, training experience, and personal goals.
• Major modes include:
– weight machines, free weights, body weight
exercises, and a broadly defined category of balls,
bands, and elastic tubing.
• A combination of single joint and multi joint exercises
should be performed.
• Free weights are more beneficial for recruiting accessory
muscles and utilize balance.
Copyright © 2014 American College of Sports Medicine
Copyright © 2014 American College of Sports Medicine
Modes of Resistance Training (cont.)
• Body weight is one of the oldest modes of training.
• It can be hard to adapt body weight exercises to one’s
strength level.
• Additionally, obese/sedentary persons may not be able to
perform body weight exercises which can be a deterrent
to exercise.
• Stability balls and medicine balls help train balance and
core strength and have been used by therapists for many
years.
Copyright © 2014 American College of Sports Medicine
Copyright © 2014 American College of Sports Medicine
Copyright © 2014 American College of Sports Medicine
Safety Concerns
• HFS needs to monitor the ability of all participants to
tolerate the stress of strength and conditioning
programs.
– Without proper supervision and instruction, injuries
that require medical attention can happen.
• All exercises should be performed in a controlled manner
using proper breathing techniques.
– Avoid the Valsalva maneuver
• HFS’s should be able to correctly perform the exercises
they prescribe and should be able to modify exercise
form and technique if necessary.
Copyright © 2014 American College of Sports Medicine
Copyright © 2014 American College of Sports Medicine
Safety Concerns (cont.)
• Resistance training area should be well-lit and large
enough to handle the number of individuals exercising in
the facility at any given time.
• HFS’s are responsible for enforcing safety rules (e.g.,
proper footwear and safe storage of weights) and
ensuring that individuals are training effectively.
• Evidence indicates that HFSs who develop and directly
supervise personalized programs can help clients
maximize strength gains.
Copyright © 2014 American College of Sports Medicine
Resistance Training Program Variables
1) Choice of exercise
2) Order of exercise
3) Resistance used
4) Training volume (total number of number of sets and
repetitions)
5) Rest intervals between sets and exercises
6) Repetition velocity
7) Training frequency
Copyright © 2014 American College of Sports Medicine
Choice of Exercise
• Select exercises that are appropriate for an individual’s
exercise technique experience and training goals.
• Promote muscle balance across joints and between
opposing muscle groups.
• Closed kinetic chain: distal joint segment is stationary;
mimic everyday activities.
• Open kinetic chain: distal joint is free to move.
• Strengthen the abdominals, hip, and low back for
postural control.
• Include multidirectional exercises that utilize stability.
Copyright © 2014 American College of Sports Medicine
Order of Exercise
• Large muscles before small muscles; multijoint before
single joint.
• More challenging exercises done in the beginning when
fatigue is minimal.
• Experienced individuals may choose to utilize a split
routine.
• Ultimately, training time availability and personal
preference should help determine type of routine.
Copyright © 2014 American College of Sports Medicine
Resistance Load Used
• One of the most important variables is weight selection.
• Adaptations to resistance training are linked to the
intensity of the training program.
• It is recommended that training sets be performed to
muscle fatigue but not exhaustion using the appropriate
resistance.
• RM Loads ≤6 are most beneficial to muscular strength.
• RM Loads ≥20 are most beneficial to muscular
endurance.
Copyright © 2014 American College of Sports Medicine
Resistance Load Used (cont.)
• A repetition range between 8 and 12 (~60% to 80% 1
RM) is commonly used to enhance muscular fitness in
novice to intermediate exercises.
• Using lighter weights (e.g., <50% 1 RM; 15–20
repetitions) will have more effect on muscular
endurance.
• Consistent training at high intensities (e.g., ≥80% 1 RM)
increases the risk of overtraining.
Copyright © 2014 American College of Sports Medicine
Resistance Load Used (cont.)
• A percentage of an individual’s 1 RM also can be used to
determine the resistance training intensity.
– Beginners: reasonable to use a resistance training
intensity of ~50% to 60% 1 RM while developing
motor skill.
• Research shows that 60% 1 RM and 80% 1 RM produced
the largest strength increases in untrained and training
adults, respectively.
• When prescribing percentages of 1 RM for an exercise, it
is important to consider the muscle being worked,
relative to strength levels.
Copyright © 2014 American College of Sports Medicine
Training Volume
• A combination of (a) the number of exercises performed
per session, (b) the repetitions performed per set, and
(c) the number of sets performed per exercise.
• ACSM recommends that apparently healthy adults should
train each muscle group for two to four sets to achieve
muscular fitness goals.
• Multiple set training is more effective than single set
training for strength enhancement in untrained and
trained population.
• Balancing high- and low-volume training allows for
proper recovery.
Copyright © 2014 American College of Sports Medicine
Rest Intervals
• Determine energy recovery and strength gains made.
• To maximize gains in muscular strength, heavier weights
and longer rest intervals (e.g., 2 to 3 minutes) are
needed.
• To increase muscular endurance, lighter weights and
shorter rest periods (e.g., <1 minute) are required.
• The same rest interval does not need to be used for all
exercises.
• Fatiguing from a previous exercise should be taken into
consideration when planning rest time.
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Repetition Velocity
• Gains in muscular fitness are specific to the training
velocity.
• Beginners need to learn how to perform each exercise
correctly and develop an adequate level of strength
before optimal gains in power performance are realized.
• It is likely that the performance of different training
velocities and the integration of numerous training
techniques may provide the most effective training
stimulus.
Copyright © 2014 American College of Sports Medicine
Training Frequency
• A resistance training frequency of 2 to 3 times per week
on nonconsecutive days is recommended for beginners.
• Allows for adequate recovery between sessions (48 to 72
hours) and has proven to be effective for enhancing
muscular fitness.
• Although an increase in training experience does not
necessitate an increase in training frequency, a higher
training frequency does allow for greater specialization
characterized by more exercises and a higher weekly
training volume.
Copyright © 2014 American College of Sports Medicine
Copyright © 2014 American College of Sports Medicine
Periodization
• Refers to the systematic variation in training program
design
• Based on Selye’s general adaptation syndrome
– after a period of time, adaptations to a new stimulus
will no longer take place unless the stimulus is
altered.
• For all individuals with different levels of training
experience who want to enhance their health and fitness.
Copyright © 2014 American College of Sports Medicine
Periodization (cont.)
• Goal is to constantly challenge training demands.
• The general concept of periodization is to prioritize
training goals and then develop a long-term plan that
varies throughout the year.
• The year is divided into specific training cycles (e.g., a
macrocycle, a mesocycle, and a microcycle) with each
cycle having a specific goal (e.g., hypertrophy, strength,
or power).
• The classic periodization model is referred to as a linear
model because the volume and intensity of training
gradually change over time.
Copyright © 2014 American College of Sports Medicine
Periodization (cont.)
• A second model of periodization is referred to as an
undulating (nonlinear) model because of the daily
fluctuations in training volume and intensity.
• Example:
– 2 or 3 sets with 8 to 10 RM loads on Monday
– 3 or 4 sets with 4 to 6 RM loads on Wednesday
– 1 or 2 sets with 12 to 15 RM loads on Friday
Copyright © 2014 American College of Sports Medicine
General Recommendations
• Resistance training has the potential to offer unique
benefits to men and women of all ages and abilities.
• Designing an effective program can be complex.
• Programs should be individualized and consistent with
one’s personal goals.
• Safe and effective programs utilize good instruction,
proper progression and consistent evaluations.
• Effective leadership and continual motivation help
maintain consistency within a program.
Copyright © 2014 American College of Sports Medicine