Chapter 5

Human Movement Science

Purpose

• To provide the fitness professional with a fundamental overview of how the components of the human movement system (HMS) work together to form, learn, and produce movement.

Objectives

• After this presentation, the participant will be able to: – Describe biomechanical terminology, planes of motion, axes,

joint motions, muscle actions, and how they relate to the kinetic chain.

– Describe how forces act on the HMS and influence movement.

– Provide an overview of motor behavior.– Describe the importance of sensory information as it relates

to movement.

Human Movement System Function

• The Human Movement System must– Be aware of its relationship to its environments, both internal

and external– Gather necessary information regarding its environments– Produce appropriate motor responses

• This ensures optimum functioning of the HMS and optimum human movement.

Biomechanics

• Biomechanics: motions that the HMS produces and the forces that act on it

• Terminology– Important to understand basic anatomic terminology – Allows for effective communication

Anatomic Locations

• Superior: a position above a reference point

• Inferior: a position below a reference point

• Proximal: a position nearest the center of the body or point of reference

• Distal: a position farthest from the center of the body or point of reference

• Anterior: a position on the front or toward the front of the body

Anatomic Locations

• Posterior: a position on the back or toward the back of the body

• Medial: a position relatively closer to the midline of the body

• Lateral: a position relatively farther away from the midline of the body or toward the outside of the body

• Contralateral: a position on the opposite side of the body

• Ipsilateral: a position on the same side of the body

Planes, Axes, and Joint Motion

• Three imaginary planes are positioned through the body at right angles, intersecting at the center of mass of the body.

• Movement is said to occur more predominantly in a specific plane if it is actually along the plane or parallel to it.

• Movement in a plane occurs about an axis running perpendicular to that plane.

• Anatomic position is reference position.

Planes, Axes, and Joint Motion

• Sagittal plane: bisects body into right and left sides, occurs around coronal axis, flexion and extension.

• Frontal plane: bisects body into front and back halves, occurs around anterior–posterior axis, abduction and adduction

• Transverse plane: bisects the body into upper and lower halves, occurs around vertical axis, internal and external rotation

Planes, Axes, and Motion

• Horizontal abduction: movement of a limb in transverse plane from an anterior to lateral position

• Horizontal adduction: movement of the arm or thigh in the transverse plane from a lateral position to an anterior position

Scapular Motion

• Scapular retraction: occurs when the shoulder blades come closer together.

• Scapular protraction: occurs when the shoulder blades move further away from each other.

• Scapular depression: occurs when the shoulder blades move downward, whereas

• Scapular elevation: occurs when the shoulder blades move upward toward the ears.

Muscle Actions

• Muscles produce a variety of actions known as the muscle action spectrum to manipulate forces.– Eccentric

• Lengthening of the muscle

• Force reduction

– Isometric• No appreciable change in the muscle length

• Dynamically stabilize the body

– Concentric• Shortening of the muscle

• Force production

Functional Anatomy: Muscles

• The traditional perception of muscles is that they work concentrically and predominantly in one plane of motion.

• It is imperative to view muscles functioning in all planes of motion and through the entire muscle contraction spectrum (eccentrically, isometrically, and concentrically).

Muscle Force

• Force is defined as the interaction between two entities or bodies that results in either the acceleration or deceleration of an object.

• The human movement system is designed to manipulate variable forces from a multitude of directions to effectively produce movement.

• The fitness professional must gain an understanding of the different kinetic chain components involved to efficiently produce force and movement.

Length–Tension Relationships

• The length at which a muscle can produce the greatest force– There is an optimal muscle length at which the actin and myosin

filaments in the sarcomere have the greatest degree of overlap. • Lengthening a muscle beyond this optimal length and then

stimulating it reduces the amount of actin and myosin overlap, reducing force production.

• Shortening a muscle too much and then stimulating it places the actin and myosin in a state of maximal overlap and allows for no further movement to occur between the filaments, reducing its force output.

Force–Velocity Curve• Refers to the ability of muscles

to produce force with increasing velocity – As the velocity of a concentric

muscle contraction increases, its ability to produce force decreases.

– As the velocity of an eccentric muscle contraction increases, its ability to produce force increases.

Force–Couple Relationships• A force–couple is synergistic action

of muscles to produce movement around a joint.– Common force–couples

• Internal and external obliques rotate the trunk.

• Upper trapezius and lower portion of the serratus anterior rotate the scapula upward.

• Gluteus maximus, quadriceps, gastrocnemius, and soleus produce hip, knee, and ankle extension.

– Muscles working together for the production of proper movement are said to be working in proper force–couple relationships.

Muscle Leverage and Arthrokinematics• Bones act as levers that are

moved by the force of the muscles around an axis (or joints).

• Amount of leverage the kinetic chain has for any given movement depends on the leverage of the muscles in relation to the resistance. – The closer the weight is to

the joint, the less torque it creates.

– The farther away the weight is from the joint, the more torque it creates.

Motor Behavior

• How the kinetic chain is able to create and learn movements

• Consists of the study of motor control and motor learning

Motor Control

• The study of movement – How the central nervous system integrates internal and

external sensory information with previous experiences to produce a motor response

Muscle Synergies• Muscles are recruited by the

central nervous system as groups or synergies. – Over time and through

proposed stages of learning, these synergies become more fluent and automated.

• Squat: quadriceps, hamstrings, gluteus maximus

• Shoulder press: deltoid, rotator cuff, trapezius

Proprioception

• The cumulative neural input from the sensory afferents to the central nervous system– Uses information from mechanoreceptors (muscle, tendon,

ligament, and joint receptors) to provide information about static, transitional, and dynamic position, movement, and sensation pertaining to muscle and joint force

– A vital source of information that the nervous system uses to gather information about the environment to produce the most efficient movement

Sensorimotor Integration

• The ability of the nervous system to gather and interpret sensory information to anticipate, select, and execute the proper motor response – There has to be a perceived reason to activate muscle tissue

• For the reduction or stabilization of forces imposed on the body

• For the production of force to overcome imposed forces on the body

– Achieved through the task of collecting and then interpreting all incoming sensory information

Sensorimotor Integration

• Only as effective as the quality of incoming sensory information – The skeletal system must be properly aligned to allow the

muscles to be positioned at the right length–tension relationships.

• This is known as structural efficiency.

– Proper structural alignment puts the body in the correct position to efficiently absorb, distribute, and produce forces.

• This is known as functional efficiency.

• Any deviation in the alignment of the kinetic chain causes altered sensory input that results in an altered motor response.

Motor Learning

• The integration of motor control processes with practice and experience that leads to a relatively permanent change in the ability to produce skilled movements. – Looks at how movements are learned and retained for

future use

Feedback

• The use of sensory information and sensorimotor integration to aid the kinetic chain in the development of permanent neural representations of motor patterns – Internal– External

Internal Feedback

• The information coming back to the central nervous system from all sensory receptors (proprioception)– Also known as sensory feedback

• Incoming (afferent) feedback is by the central nervous system to monitor movements and their outcomes, provide information about the environment, and allow for any necessary adjustments to be made.

External Feedback

• Information provided by some external source such as a fitness professional, videotape, or a heart rate monitor– Also known as augmented feedback

• Used to supplement internal feedback

• Provides clients with an external source of information that allows them to associate how the achieved movement pattern was (“good” or “bad”) compared with what they are “feeling”

External Feedback• Two major forms

– Knowledge of results: used after the completion of a movement to inform clients about the outcome of their performance.

– Knowledge of performance: provides information about the quality of the movement pattern.

• Clients must not become dependent on external feedback, especially from the fitness professional, as this may detract from their responsiveness to the internal sensory input.

Summary

• Each system of the human movement system (HMS) is interdependent.

• The entire HMS must work together to gather information from internal and external environments to create and learn movements (motor behavior).

• The body uses proprioception, sensorimotor integration, and muscle synergies to create efficient movement (motor control).

• Repeated practice, as well as internal and external feedback, allows this efficient movement to be reproduced (motor learning).