ACE 6th Edition Chapter 9: Muscular Training: Foundations and Benefits 4

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Chapter Goals:

  • Explain the basic anatomy and physiology underpinning muscular training and how this knowledge enhances the design and implementation of safe and effective muscular training programs. 
  • Be able to find the widespread benefits of muscular training. 
  • Understand the acute and chronic physiological adaptations to muscular training. 
  • List the principles of muscular training and recognize how these fundamental concepts apply to designing programs. 
  • Find the key variables for muscular training program design. 

Anatomical Systems

Muscular training is also known as resistance training, strength training, or weight training, and this is a central feature in the ACE IFT Model.

The use of muscular training can influence pretty much every single system of the body and has many benefits ranging from increases in the strength of skeletal muscles to improvements in the density of bones and the greater regulation of blood glucose levels. 

Skeletal System

The human skeleton is an active and living tissue needed for supporting structures, moving, and protecting organs, storing minerals, and forming blood cells. The main structural functions of bones are to provide support for the body’s soft tissues and provide the sites to which the muscles will attach, and these two things play a major role in the movement. 

We have various types of bones and different shapes that exist, which is important for them to have different functions and allow various muscles to attach and function. 

Out of all of the 206 bones of the body, 74 of them are actually put into the category of the axial skeleton. This comprises the skull, vertebral column, sternum, and ribs, which protect the central nervous system. 

The bones that remain of the 206 will be the appendicular skeleton, including the bones of the upper and lower limbs, the shoulder, and the pelvic girdles. 

It is important for trainers to have an understanding of these skeletons and know the basics of attachments and joint movements. 

Our bones will come together with other bones for articulation. These articulations allow the muscles to push and pull to move the body in all its motions. 

Synovial joints are the most common form of the joint within the body and are the freely movable type of joint. 

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We also have ligaments that are in place to strengthen the joints and stop movement indirections that could negatively affect the joints. 

The anatomical position is what we refer to as when a person is standing erect with their head, eyes, and palms facing forward. The feet are close, and the toes point forwards with the person’s arms hanging down by the side. With the anatomical position, we refer to movement in the different planes of motion and the axis of rotation. The three planes of movement are the sagittal plane, the frontal plane, and the transverse plane. 

The four angular movements for the synovial joints are the movements of flexion, extension, abduction, and adduction. 

As trainers, we should understand the function of joints and the movements that are capable at each type. 

Nervous System

The nervous system plays the role in collecting information about the conditions in relation to the internal and external state of the body. It then analyzes this collected information and initializes the right responses to fulfill specific needs.

The central and peripheral nervous systems are the two systems making up the entire nervous system. 

The CNS is made up of the brain and the spinal cord, and these are shielded by bony structures like the skull and the vertebral column. The CNS is used to receive the sensory information from the PNS and formulate a response to this input info. 

The PNS is then made up of all of the things outside of the CNS. These are things such as the nerves and ganglia.

The PNS is split into two categories: the autonomic nervous system and the somatic nervous system. These two systems work together to move the body, in the case of the somatic system, and control things like digestion and other involuntary things, in the case of the autonomic system. 

Proprioception is the sense of knowing where the body is in relation to the external environment.

Muscular System

Muscle tissue is put into different types based on its function, voluntary or involuntary control, and its ability to produce force based on the size and shape of the muscle.

We have three types of muscle tissue. These are skeletal, smooth, and cardiac muscles. 

Skeletal muscle tissue is the kind that attaches to the skeleton, and through its contraction, force is exerted onto the bones to move and stabilize. It is a voluntary type of muscle that can be controlled consciously. 

Smooth muscle is what we find in the walls of hollow organs and tubes like the stomach, the intestines, and the blood vessels. This muscle type functions to regulate the movement of materials through the body. This is also an involuntary type of muscle. 

Cardiac muscle forms the heart’s walls and is a very specialized type of tissue that maintains the heart’s constant pump. This is an involuntary type of muscle, but its appearance is closer to that of the skeletal muscle fibers. 

Most of the talk will now be on the skeletal muscle since we have control of these and use them to move, the basis of this book.

We categorize muscles as being four different things: agonists, antagonists, stabilizers, and synergists.

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Agonists’ muscles are the prime movers of movements and they work to go against the force and do the majority of the work. 

Antagonist muscles are the ones that oppose the agonist’s muscles and they work to relax in times of work so that the prime mover may do its job. 

The synergistic muscles are the muscles that will help the prime movers by adding some force to help. 

The stabilizers will function to secure joints and ensure that the muscles can work in their optimal path. 

Muscle Fiber Types

We have two types of muscle fibers. These are slow and fast twitch fibers. 

Slow twitch fibers are the fibers that are used for aerobic energy production, meaning that they use oxygen to produce ATP. These are used in endurance activities. 

Fast twitch fibers are muscle fibers used for anaerobic energy production, meaning that they function without oxygen. We have two types of fast twitch fibers: type IIa and IIx.

The Sliding filament model is used to describe how the muscles contract and make the muscle shorten. 

Connective Tissue

Connective Tissue is the material that is between the cells of the body and gives the tissues their form and strength. These connective tissues are made up of dozens of proteins that, include the main one of collagen. 

The major physical properties of collagen fibers are tensile strength and relative inextensibility.

Elastic fibers are another structure that gives connective tissues their properties. They are made up of amino acids, just like collagen fibers. These two tissues are always found together. 

The connective tissues give the range of motion we see with our joints. This can vary based on many different factors. The range of motion is the amount of movement that the joint can reach. This is an important factor in how efficiently we go through movements. 

Human Motion Terminology

We have three types of muscular actions that we can go through. These are concentric, eccentric, and isometric. 

Concentric actions are the ones where the muscle is getting shorter and, thus, overcoming some resistance or force. In a bicep curl, the bicep goes through a concentric action when it increases the weight. 

Eccentric actions are the ones where the muscle is getting longer while still also contracting, and thus, they are losing to the force and lengthening. In a bicep curl, this would be when the weight returns to the start of the movement. 

Isometric, or static, actions are when there is no change in the length of the muscle. So, in a bicep curl, this would be like keeping the weight at 90 degrees and not moving. The muscle contracts still, but it does not change its length. 

We have exercises sometimes divided into open and closed chain exercises. 

The joints we have, move, but this amount of movement is determined based on all of the surrounding structures and the intention of the joint. The joints differ in how much stability and mobility they provide. There is a tradeoff that exists between these two. You will find the more stable a joint is, the less mobile it is, and the same when reversed. 

Balance and alignment come into play when people are training, as we must promote proper body alignment and use our stabilizing muscles to stay stable. It is important to consider the center of gravity and the line of gravity as trainers. 

Benefits of Muscular Training

Muscular training is the process of exercising with progressively heavier resistances to stimulate muscle development. The main outcome of this training style is an increase in the size of the muscle fibers and the contractile strength. Some other outcomes will be greater tensile strength in the ligaments and the tendons and greater bone density. 

The ability of the person to perform work or exercise will increase when utilizing muscular training. Stronger muscles is the obvious result of training, but it also matters the style of muscular training, as we see results specific to training. 

We see the enhancement of metabolic function in people. This is because the muscle burns more calories than fat, and the actual work done causes the metabolism to work harder and more efficiently. 

We see reductions in risk and disease prevention. Muscles serve as absorbers of shock and they provide stability for the joints. If the muscles are stronger, they will dissipate the loading forces that are experienced in activity more efficiently.

Some other minor benefits are:

  • Improvements in body composition
  • Stronger low back muscles to help with the chronic low back problems seen in society today
  • Decreases in the prevalence of depression in older adults
  • Reductions in pain from osteoarthritis and rheumatoid arthritis
  • Improvements in the functional ability of older adults

Some factors that will influence muscular strength and hypertrophy:

  • Hormone levels
  • Sex
  • Age
  • Type of the muscle fibers
  • Muscle length
  • Limb length
  • The insertion point of tendons

Muscular Training Principles


This is the first principle, and it simply states that to get stronger, we have to have progression in our resistance training programs. This is one that is present in cardiovascular training also. 

We progress by increasing the number of reps performed, the number of sets done, or any of the other variables of working out. 


The principle of specificity, like with cardio training, means that for us to achieve the goals we set, we must train in a specific way. If we want to be better at some sport, then we need to train in a way using movements that are specific to that sport. 


Overload is a principle that says we need to increase the exercise volume to continue seeing results gradually. This is known as overloading the muscle. Always increasing the stimuli it receives. 


The principle of reversibility says the gains you make when you are training will usually leave in double the time it took to get them. So, if it took you ten weeks to put on 4 pounds of muscle, you would lose the 4 pounds of muscle in about five weeks now. 

Diminishing Returns

This principle says that as we progress and get stronger, the number of results we see will go down and there is a natural limit to our ability to exercise. This is why people who have worked out for years will see fewer results in a month than those who start working out for their first month. 

Muscular Training Variables Related to Program Design

The design of effective programs will require several variables to be taken into account:

  • We need to complete a thorough needs assessment of the client. 
  • Appropriate exercise frequency should be consistent with the client’s goals, training experience, and current fitness level, and there should be a good amount of recovery between the sessions.
  • The exercises that are chosen will need to be in the right order and chosen to be consistent with the program needs and goals, the availability of the equipment, the experience the client has, the technique, and the level of conditioning. 
  • The exercise volume and loads, including the sets, reps, and intensities, should be considered thoroughly. 
  • The right rest intervals should match the needs and goals of the clients. 

A proper resistance routine, just like cardiovascular training, should include a warmup, conditioning, and cool-down phase. 

ACE 6th Edition Chapter 9: Muscular Training: Foundations and Benefits 5
ACE CPT Chapter 1: Role and scope of practice for the personal trainer 2
ACE 6th Edition Chapter 9: Muscular Training: Foundations and Benefits 6
Tyler Read - Certified Personal Trainer with PTPioneer

Tyler Read

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