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Canadian Fitness Education Services (CFES)
Fitness Knowledge Homestudy Program

Chapter 5 Principles of Human Movement

Movement Analysis

This chapter will provide a more detailed overview of human movement, including the different roles muscles play to control, assist or support movement and the different biomechanical factors that affect the way we move.   We begin with another look at muscle function.

 

Skeletal muscles work in partners, or pairs around the joints. Grouped together on opposite sides of the bones (e.g. anterior/posterior or medial/lateral), they pull on one side to create flexion (or adduction) and pull on the other side to create extension (or abduction). When a muscle or muscle group contracts on one side of a joint, the muscle(s) on the opposite side must relax and lengthen to allow the movement to occur.   This is called an agonist antagonist relationship.

 

We also have muscles that assist the movement at a joint (because they cross the same joint) and we have muscles that contract to stabilize the body, or part of the body, holding it still during the movement.   Therefore, we can identify four different roles that muscles play.

 

Agonist (Prime Mover) This is the muscle that is primarily responsible for a given movement. When more than one muscle crosses the joint, it is generally the larger muscle which will be the prime mover. For example, both the hamstrings and the gluts cross the hip joint, but in a hip extension exercise, the gluteus maximus (being the larger muscle at the hip joint) is considered the prime mover.

 

Antagonist (Opposing Muscle) This is the muscle that opposes the action of the prime mover. It is usually on the opposite side of the joint and it relaxes and stretches while the prime mover contracts. For example, in a hamstring curl the quadriceps must relax to allow the hamstring to contract.

 

Synergist (Assisting Muscle) This is the muscle group that assists the prime mover. It crosses the same joint but is smaller in size, or it may be causing movement at a secondary joint that is also involved in the exercise. For example, the synergist in a shoulder press (military press) is the triceps.   The deltoids control the movement at the shoulder and the triceps control the movement at the elbow.

 

Stabilizer This is the muscle group which holds the body, or parts of the body, rigid while other parts of the body are moving. For example, in a squatting movement the torso muscles stabilize the body while the leg muscles raise and lower the body.

 

Analysing Movement

 

Classifications of Movement (Single Joint/Compound)

 

Some exercises involve movement at only one joint. For example, a biceps curl with a dumbbell only involves movement at the elbow joint. Single joint movements are fairly simple to analyse . Other exercises involve movement at more than one joint.   For example a push up involves movement at the shoulder and the elbow. These are called compound exercises and they are a little more complicated to analyse. Here a few examples of each.

 

Analysing Single Joint Movements

1.  Draw a picture or perform the movement   (e.g. a biceps curl).

 

2.  Identify the working phase and releasing phase.

     (a) working phase (positive or concentric phase) raising the dumbbell.

     (b) releasing phase (negative or eccentric phase) lowering the dumbbell.

 

3.  Identify the joint movement in the working phase elbow flexion. The muscle that causes this joint movement, the biceps brachii, is the prime mover.

 

4.  Identify the joint movement in the releasing phase elbow extension. The muscle that causes this joint movement, the triceps, is the opposing muscle. It must relax and lengthen during the contraction of the prime mover.

 

5.  The assisting muscles are other (sometimes smaller) muscles that are also involved in the working phase. In this example, the brachialis and brachioradialis could be listed as assisting muscles.

 

6.  The stabilizers are those muscles which contract to hold the working limb still (the deltoids) and/or the body still (the abdominals) during the exercise.