Personal Trainers Certification Online Course - Biomechanics
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Personal Trainers Certification Online Course - Biomechanics

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Biomechanics Think about what we’ve learned so far. When Introduction to Biomechanics we move, our nervous system instructs our muscles to contract. These contractions cause What is Biomechnics? bones to move around the axes of joints. For Biomechanics evaluates the motion of a living this reason, our bodies can be viewed as a se- ries of levers (bones) which rotate around an organism and the action of forces upon it. In axis (joints) under the direction of a force (mus- the personal fitness training field, biomechanics can be looked at as the study of how the body cular contraction). When working with a client, we have a responsibility to not only guide them moves and what causes movement either inter- to their goals, but to do so in a safe and effective nally (via muscles) or externally (via external load manner. It is vital to have some understanding or added weight bearing activities). Biomechan- of how the human body is meant to move and ics is simply the application of the Laws of Phys- ics to the human body. more importantly, which movements to avoid and why. If a trainer does not understand these fundamental principles, their workouts will be Why are we concerned about inefficient and potentially dangerous. Our pri- Biomechanics? mary concern as trainers should always be to If you were to pick up a sports biomechanics give clients the greatest benefit with the least textbook, it would most likely say there are two amount of risk.

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Published 12 July 2014
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Biomechanics

Think about what we’ve learned so far. When Introduction to Biomechanics
we move, our nervous system instructs our
muscles to contract. These contractions cause What is Biomechnics?
bones to move around the axes of joints. For
Biomechanics evaluates the motion of a living this reason, our bodies can be viewed as a se-
ries of levers (bones) which rotate around an organism and the action of forces upon it. In
axis (joints) under the direction of a force (mus- the personal fitness training field, biomechanics
can be looked at as the study of how the body cular contraction). When working with a client,
we have a responsibility to not only guide them moves and what causes movement either inter-
to their goals, but to do so in a safe and effective nally (via muscles) or externally (via external load
manner. It is vital to have some understanding or added weight bearing activities). Biomechan-
of how the human body is meant to move and ics is simply the application of the Laws of Phys-
ics to the human body. more importantly, which movements to avoid
and why. If a trainer does not understand these
fundamental principles, their workouts will be Why are we concerned about
inefficient and potentially dangerous. Our pri-
Biomechanics? mary concern as trainers should always be to
If you were to pick up a sports biomechanics give clients the greatest benefit with the least
textbook, it would most likely say there are two amount of risk.
primary goals for biomechanics: performance
enhancement and injury prevention/re-
Biomechanics - a NEW way of habilitation. Biomechanics enhances perfor-
mance by utilizing mechanical principles to im- looking at exercise
One of the primary goals of this chapter is to prove an individual’s technique, the equipment
they use and to modify specific training protocols empower you with a solid foundation in biome-
that the trainer implements to help an individual chanics. Another is to introduce you to a new
way of looking at exercise in general. This is acheive their goals. Similarly, for injury preven-
tion and rehabilitation, biomechanics is used to new perspective is simply this:
develop techniques that reduce the chance of
Exercise is simply a mechanical stress injury as well as changes in equipment design to
reduce injury. placed on the body to which the body will
adapt.
Consider the “Job of a Trainer” from chapter 1.
What is the goal of a personal fitness trainer? In order to understand this new perspective and
it’s importance, one must be willing to accept “Help clients reach their goals the most efficient,
effective and safest way possible.” Now com- several premises.
pare that with the goals of biomechanics. They Premise #1
are virtually the same! To reach goals (perfor-
The primary physiological effects of mance enhancement) the most efficient, effec-
exercise (both good and bad) are in direct tive and safest (injury prevention) way possible.
response to the mechanical stress placed
on the body. Remember the GAS Theory from chapter 2? design. The exercises chosen (and how they
The GAS Theory shows us that the body will un- will be implemented) are based on the client’s
dergo adaptations when it is stressed. Exercise goals and needs and your knowledge of how to
can be seen as a mechanical stress (Force/Area), make them adapt safely and efficiently.
placed on the body where the body must ac-
cept forces from external sources and respond Lastly, exercise instruction - the area where most
by creating the appropriate internal forces (from personal trainers associate the importance of
the muscles and connective tissue) to create biomechanics. Put simply, understanding basic
the appropriate movement. The stimulus of biomechanics is the basis of instructing proper
these stressors (both externally and internally), technique.
stimulate the physiological adaptations within
the body. These physiological adaptations may
How do we use Biomechanics to be structural (adaptations to connective tissue
such as muscle, bone and fascia) or functional Maximize Performance and Minimize
(neuromuscular adaptations - i.e. motor learn- Chance of Injury?
ing). There is a systematic thought process that ev-
Premise #2 ery trainer must utilize in order to ensure that
their clients are getting the most of every rep in In order to facilitate the proper adaptations
every set. for our clients we have to understand forc-

es, how they are applied (how much, in what Analyze (movement)
direction, over what range of motion and Optimize
at what speed), and how the tissues of the
in order to... body will adapt to those forces.
Maximize (performance)
Minimize (injury) Put simply, understanding forces and their ef-
fects is at the core of personal fitness training.
What do we Analyze? Remember, there are forces on us all the time
(whether something is moving or not). And if When we evaluate the client’s technique, we are
there is movement, there’s a force that caused doing a biomechanical analysis (and remember,
that . every rep of every set is an assessment). You
should be able to distinguish between what is Premise #3
important and what is unimportant, what is cor-
Proper understanding and implementation rect and what is incorrect, what is possible and
of biomechanics is essential in all aspects what is impossible, what is effective and what
of training (Assess - Design - Instruct). is ineffective, what is safe and what is unsafe,
etc.
When you reach the assessment section, you
will find that much of the assessment process The first thing to evaluate and understand is the
consists of postural and movement assess- movement itself, without regard to the forces
ments. Put simply, these are biomechanical as- that caused it. In physics, this is known as ki-
sessments (looking at how the client’s body has nematics. This would be analyzing such de-
adapted to the forces through the years). These tails as the osteokinematics (planes of motion)
assessments might indicate certain kinetic chain you learned in chapter 3, the direction of mo-
imbalances (short/tight muscles on one side of tion, the path of motion, and the range of mo-
a joint) that need to be addressed. tion. Futhermore, a kinematic analysis might
include basic kinematic variables such as dis-
As previously stated, understanding how the tance, speed and acceleration (which you will
body is going to adapt to the biomechanical learn shortly).
stress you place upon it is essential to program
94 Only after you analyze the kinematics to you Step 1: Describe the Ideal Technique
look at the forces that cause the movement (as In order to train anyone a particular movement,
well as other forces on the body). In physics, you must have a fundamental knowledge of the
this is known as kinetics. skill. This begs the question, how do we know
the “ideal” technique? If it’s a performance
Another way of looking at the analysis process movement, such as pitching a fastball, you’ll
is to look at joints first (both moving and not want to watch successful pitchers, read coach-
moving, describing them kinematically), then ing journals and textbooks, and find any other
the external and internal forces on the body (ki- sources that discusses how successful individ-
netcs). Note, muscles are engineered to move uals apply their skill.
joints in a particular fashion (based on the struc-
ture of the joint). So a basic understanding of More likely, you’ll be describing some sort of ex-
joint structure and function is essential for prop- ercise or drill. Once again, you’ll use the same
er muscle activation (i.e. if we are moving the strategy of researching what the “ideal” tech-
joints properly, then the muscles must be work- nique is. That said, whether your describing
ing properly). Furthermore, we don’t really know a sports-specific skill or an exercise, you must
which internal forces are developed without first think critically and be skeptical of the “experts”.
looking at the external forces that caused it. Just because one person is successful doing
a bench press in a particular fashion doesn’t
mean everyone should use the same technique. Basic Definitions Please remember that your job is to individualize
Kinematics - The study of motion without re- the technique to the individual. It should be cu-
gard to its causes (forces) sotmized to their current abilities, their genetics
and their goals. Kinetics - The study of forces acting on a sys-
tem
The bottom line is when you are researching to Kinesiology - The scientific and artistic study
describe the ideal technique, you are really at- of human movement
tempting to find the common characteristics of
Force - A “push” or a “pull”. Based on New-
the most efficient technique and to appropriately
ton’s Second Law of Motion, Force = Mass x
modify this characteristics with your clients. Acceleration

Step 2: Observe the Client Performing the
How do we Analyze?
Technique
DOE-I: The practical way to Analyze and When observing a client perform a particular
technique, we have to ask ourselves several Optimize
questions. While it is unlikely that you will be using ad-
vanced biomechanical analysis tools with your
clients, there is a step-by-step process to do a • Who are we observing? What is their cur-
quailitative biomechanical analysis recommed- rent skill level? What are their current limi-
ed by McGinnis (2005). tations?
DOE-I • Under what conditions?
Describe (the • Where to observe? Step 1 D
ideal technique) • What to look for?
Observe (the client Step 2 O
per- form the The answers to these questions will determine
technique) Evaluate (the your ability to successfully evaluate the client.
Step 3 E
perfor- mance)
Step 4 I Instruct (the client)

95 Step 3: Evaluate the Perforamance the client and correct the errors in technique.
When evaluating the performance, we are sim- This will be discussed in greater detail in Chap-
ply comparing the “ideal” with the actual per- ter 10: Exercise Instruction.
formance of the client. We are identifying er-
rors and evaluating those errors to determine What to we Optimize?
the focus of your correction efforts. As the old
Again, we focus on both the movement (kine- expression goes, “you have to pick and choose
matics) and the forces that cause the movement your battles.” Is the error actually dangerous
(kinetics). We take into account the structure of and there is risk of injury. Or, is it a new client
the body (specifically, the anatomy of the joints learning a new skill that will take time to develop
first), it’s intended function and the goal of the the proper motor pattern?
exercise. We need to understand the ideal
How do we Optimize? movement and instruct accordingly. Our goal is
to get our clients as close to the ideal technique Step 4: Instruct the Client
(which my be unique to them) in order to Maxi- This is where proper communication skills are
mize Performance and to Minimize Injury. vital so you can successfully communicate with




Dumbbell Row
Analyze


• muscle hypertrophy (ex:
latissimus dorsi)?

• “pulling” endurance?
• other?
Kinematics?
• start position?
• plane of motion?

• range of motion
• speed of motion?
• other?
Kinetics?
• external forces (ex: dumb-
bell)
• internal forces (ex: mus-
cles involved)

96
Goal


Start (Position)
Describe
(the “ideal”)
Motion (Kinematics and Kinetics)
Start (Position)



Observe
Motion (Kinematics and Kinetics)
Start (Position)



Evaluate
Motion (Kinematics and Kinetics)
Start (Position)



Instruct
Motion (Kinematics and Kinetics)

Maximize Performance & Minimize Injury
97
Optimize
Analyze (Kinematics and Kinetics) Scalars
A term describing distance, speed or mass
which has magnitude but no direction. In other
words, it is a quantity that can be fully described

by its magnitude.

For example: Mass (m) - a scalar quantity mea-
suring an object’s inertia (resistance of an object
to motion). The mass of the dumbbells in the
picture below would be the same on the moon
as it would be on earth (even though its weight
is very different).













Kinematics -

Vectors Analyzing Motion (How far?
A term describing something that has both mag-
How fast? In what direction?) nitude and direction (i.e., displacement, velocity,
force). Vectors are represented by an arrow. The
direction and length of the arrow demonstrates
Scalars and Vectors the equivalent of a force and how it is applied to
In order to analyze motion, one first needs to be an object.
able to describe motion. One needs to be able
to answer kinematic questions such as:

• What type(s) of motion is(are) occuring.
• What is the start postioning?
• What is the goal of the motion?
• How much motion is there (range of motion)?
• What direction is the motion (path of motion)?
• How fast is the motion?
The following section will introduce basic kine-
matic concepts that are important to the ques-
tions above (as well as many other questions
we haven’t considered yet). But before we start
showing how to answer the questions above, it
is important to designate two classifications of
quantities used in mechanics - vectors and sca-
lars. Anything that can be measured in physics
is classified as either a scalar or a vector.
98 Types of Motion
What is motion? Movement is a change in posi- types of motion tion from one point to another over a period of
time. We classify movements as either linear,
angular, or both (general).

rectilinear Linear motion (i.e. translatory motion) is when
motion all the points on an object move together - the
same distance, the same direction and at the
linear same time. There are two types of linear motion,
motion rectiliniear motion and curvilinear motion.
Rectilinear motion is what is most commonly
curvilinear associated with the idea of “linear” motion - it
is movement in a straight line. Curvilinear mo- motion
tion, on the other hand is movement on a curved
path.
Rotary movement is the movement of an object
rotary or segment around a fixed axis in a curved path.
Each point on the object or segment moves (angular) motion
through the same angle, at the same time, at a
constant rate. An example would be a door with
the hinge as the axis and the door, which
moves around it. There are few, if any joints in
the hu- man body which move around a truly general plane mo-
fixed axis. However, for simplicity’s sake, joint tion
motions are often described as being rotary
movements.


General plane motion is a special case of cur-
vilinear motion where the object is segmented
and free to move rather than rigid or fixed. In Describing Motion
general plane motion, an object rotates about Linear Motion
an axis while the axis is translated in space by motion is measured in linear distance motion of an adjacent segment.
(i.e. inches or centimeters).

How high is this
weight lifted?
2 ft
99 Distance and Displacement Acceleration
Linear motion is quatified either as distance or A vector quantity demonstrating the rate of
displacement. Distance is simply a measure of change of an object’s velocity. In other words,
the path followed of an object, from it’s initial it is how quickly something “speeds up” or
position to it’s final position. Displacement on “slows down.”
the other hand is a vector quantity describing a = Δv/Δt
a change in position, a straight line from initial
position (no regard to path taken). For exam- Note: acceleration is a very important con-
ple, let’s look at a runner on the inside lane of a cept. In a sense, it bridges the two branches
track for a 200m sprint. The distance covered is of mechanics - kinematics (motion) and kinetcs
200m, but the runner’s displacement is approxi- (forces). This is because as we are going to find
mately 123.8m. out shortly, if there is an acceleration, there is a
force that caused it.

Momentum
A vector (symbol = p, since “m” was already
taken for mass) which measures the motion of
an object. It is an object’s mass multiplied by it’s
velocity.
p = mv
Notice two things about momentum. First, mo-
mentum truly is the measurement of an object’s
motion. So when you think motion, think mo-
mentum. Second, notice that momentum is a
constant. In other words, an object will main-
tain it’s motion (momentum) unless acted upon
by an outside force. This is known as Newton’s
First Law of Motion. So an object will maintain
it’s motion (or lack of motion) unless an outside
force speeds it up (accelerates it) or slows it
down (negative acceleration, “deceleration”).

Rotary/Angular Motion
motion is measured in degrees Finish
or radians.
Velocity and Speed
180

Velocity and speed both measure the rate in
How many de- change of the position of an object. In other

grees were com- words, “how fast” something is moving. Aver-
90 pleted in this ROM
age velocity is a vector and is total displacement

(Range of Mo- over time.

tion)? Δ displacement
average velocity =

Δ time


0

Speed is a scalar and is the total distance cov- Learn about becoming a NESTA Certified
ered over time. Personal Trainer. Start your fitness career now.
Δ distance
average speed =
Δ time
101
Compound v. Single Joint Movements Kinetics -
Compound Movement
Analyzing Forces (Multi-joint): Overall
Force - (this is important so pay attention!) movement is due to is a vector quantity, exerted between two several joints working
bodies in contact. together. (i.e., single-
F = ma arm row (shown) squat
(Force = mass x acceleration, unit = Newton. or bench press).
Also see Newton’s second law)
More simply put, a force acts as a PUSH or a Single Joint Movement:
PULL. It is represented by an arrow. The direc- Overall movement is due to one
tion of the arrow is the direction of the force. The joint moving about its axis. (i.e.,
origin of the arrow is the site of application of Bicep curl (shown) knee exten-
the force and the length of the arrow represents sion or lateral raise)
its magnitude.

Weight
Weight is a type of force, measuring an object’s
gravitational attraction to the earth or another
object.
Symbol = w = g * m


Closed Chain v. Open Chain
Chain is an engineering
term and is used in kinesiology to
describe compound movements
where the movement of one joint
will produce predictable motion at
another joint. (i.e., barbell squat (if Impulse (J)
knee joint moves, hip must move)). A force applied to an object over time that
It is a kinematic interdependance - causes momentum to change. In other words,
the chain is “closed” when both ends are fixed Force is equal to the rate of change of mo-
to a common object. mentum. If you increase momentum (either by
increasing the velocity or increasing the mass)
it will take more Force to stop the momentum.
Open Chain is an engineering term which will This is where potential injuries can occur. If mo-
be used to refer to a compound or single joint mentum is increased (commonly done by in-
movement where the movement of one joint creasing velocity and “throwing the weight”), it
does not require the of another is not the “throw” of the weight that is typically
joint. (i.e., dumbbell bench press (movement dangerous, but having to stop and “catch” the
of the shoulder does not dictate movement of weight. If this Impulse (Force) needed to stop
the elbow). The chain is the motion (momentum) is uncontrolled, it can
“opened” because one cause damage to the connective tissues. This
end is not fixed and hence ability to “decelerate” an object is important in
interrupts the kinematic in- developing explosive power that is often used
terdependance. in sports. However, these are skills that must
first be developed through the use of controlled
movements which challenge coordination and
proprioception
101 Forces and Rotation Levers
tras A rigid object that transmits and modifies force
perts or motion when forces are applied at two points
c l i c k h e r e of the object and it turns about a third point.

























Work (W)
Work is defined as the product of the force on
Axis (Fulcrum) an object and the distance it moves in the direc-
The point which a lever rotates around due to an tion of the force.
applied force.

Work = Force * Distance

Work performed is associated with energy. En-
ergy is defined as the capacity of a physical
system to do work. As an oversimplification,
just remember that the more work is performed,
the more energy is needed and hence calories
consumed.

Lever Arm (LA) Power (P)
The portion of the lever that is a fixed distance Power is defined as the rate of doing work (i.e.
from the axis to the point of application of how quickly work is done).
force.
Power = Work/Time
Effort/Force arm (FA)
A type of lever arm which is measured from the Power is can also be defined as the product of
distance of the axis to the force causing move- the force of an object and the velocity of the
ment on the lever. object in the direction of the force.

Resistance arm (RA) Power = Force * Velocity
A type of lever arm which is the distance from
the axis to the force (resistance force) that re- Power is often highly sought after in training for
sists the effort force. performance.

Think about it...
““There was no point telling an athlete to perform a certain type of training if I didn’t understand
how much force they had to produce, in what direction, over what range of motion it needed
to be produced and at what speed. I also realised that, instead of spending months giving an
already good athlete lots of physical training to make them just a little bit fitter, I could spend a
few weeks altering their technique to make them staggeringly more efficient … and the world
of sports performance seemed to open.” (Dr. Anthony Blazevich, Sports Biomechanics - The
Basics: Optimising Human Performance 2007)

102