Chapter 4: Muscular Strength and Endurance

Learning Objectives

. Describe the basic physiology of muscles and explain how strength
training affects muscles.
. Define muscular strength and endurance and describe how they relate to
. Assess muscular strength and endurance.
. Apply the FITT principle to create a safe and successful strength
training program.
. Describe the effects of supplements and drugs that are marketed to active
people and athletes.
. Explain how to safely perform common strength training exercises using
free weights and machines.


Muscles make up more than ________ of your body mass. Muscular strength and
endurance are vital to health, wellness, and overall quality of life. This
chapter explains the benefits of strength training and describes tests used
to assess muscular strength and endurance. It describes the basics of
weight training and provides guidelines for establishing a weight training

I. Basic Muscle Physiology and the Effects of Strength Training

A. Muscles consist of individuals' muscle cells, or
_____________________, connected in _____________ which enables the
body to move.

1. Muscle fibers are bundles made up of smaller units called

2. Strength training causes the size of individual muscle fibers to
increase by increasing the number of myofibrils known as
_____________________. Inactivity causes the opposite effect,
known as _______________.

B. Muscle fibers are classified according to their strength, speed of
contraction, and energy source.

1. ________________________fibers are relatively fatigue resistant
and do not contract as rapidly or strongly as fast-twitch fibers.

2. ________________________ fibers contract more rapidly and
forcefully than slow-twitch fibers but fatigue more quickly.

3. Most muscles contain a ___________________________ fiber types,
the composition of which is based on ______________.
________________activities tend to use slow twitch fibers, whereas
_______________&______________ activities require fast twitch

C. To exert force, the body recruits one or more motor units to contract.

1. A _________________ is made up of a nerve connected to a number
of muscle fibers.

2. When a motor nerve calls on its fibers to contract, all fibers
contract to their full capacity.

3. The number of motor units is dependent upon the amount of
_____________ required.

D. Strength training improves the body's ability to recruit motor units-
__________________ - which increases strength even before muscle size

II. Benefits of Muscular Strength and Endurance

Enhanced muscular strength and endurance can lead to improvements in
the areas of performance, injury prevention, body composition, self-
image, lifetime muscle and bone health, and metabolic health..

A. Improved Performance of Physical Activities
Increased muscular strength and endurance helps with performance of
everyday tasks and recreational activities and leads to the enjoyment
that accompanies higher levels of achievement.

B. Injury Prevention
Muscular strength and endurance help protect you from injury in two
key ways:

. By enabling you to maintain good posture.

. By encouraging proper body mechanics during daily activities such as
walking or lifting.

C. Improved Body Composition
Muscular strength and endurance exercise increases fat-free mass which
raises metabolism..

D. Enhanced Self-Image and Quality of Life
Strength training offers the benefit of readily recognizable results:
Your body will become noticeably stronger and firmer, and you can
easily monitor your progress in terms of amount of weight lifted and
number of repetitions, leading to greater self-confidence and self-

E. Improved Muscle and Bone Health with Aging
Strength training can prevent muscle and nerve degeneration brought
about by aging and inactivity.

1. After age 30, people begin to lose muscle mass (sarcopenia)
which leads to loss of strength and eventual mobility.

2. Aging and inactivity can cause motor nerves to disconnect from
the portion of muscle they control and allow muscles to become
slower-less able to perform quick, powerful movements.

3. Risk of bone loss, or osteoporosis, can be lessened with
strength training, and increases in muscle strength can also help
prevent falls.

F. Metabolic Health
Regular strength training helps prevent and manage both CVD and
diabetes by:

. Improving glucose metabolism.

. Increasing maximal oxygen consumption.

. Reducing blood pressure.

. Increasing HDL cholesterol and reducing LDL cholesterol (in some

. Improving blood vessel health.

III. Assessing Muscular Strength and Endurance

A. Muscular strength is usually assessed by measuring the maximum amount
of weight a person can lift