When muscles are first learned, it is classically the concentric (shortening) contractions that are first learned. Unfortunately, this is often as far as many students progress when learning about the musculoskeletal system. If a snapshot were taken at any one instant in time during a motion pattern, less than half of the contractions that are occurring in the body would actually be concentric contractions of movers (agonists). There are also the eccentric contractions of antagonists and the isometric contractions of fixators (stabilizers).
A nice exercise to do to examine and learn about the roles of muscles is to choose a specific joint action (and describe the position of the body at that time to determine the role of gravity), and then determine a possible mover, antagonist, fixator, neutralizer, and support muscle. Be aware though that some actions are simple and some are more complicated.
Joe
May 20, 2009 at 4:01 am
1. abduction of the arm at the shoulder joint.
2. gravity is the atagonist.
3. rotator cuff group, Supraspinatus
4. The supraspinatus is contracting concentrically.
5. the Deltoid would be a synergist.
June 2, 2009 at 11:35 pm
1. Abduction of the right arm at the shoulder, while standing in the middle of a room.The hand and fore arm are just going alone for the ride.
2. A possible antagonist in this scenario would be coracobrachialis, because it adducts the arm at the shoulder joint.
3. No the antagonist would not be working, because gravity is pulling the arm down.Gravity is the antagonist.
4. Noneutralizer, the supraspinatus only abducts the arm at the shoulder joint It doesn’t have a second action; like rotation, that has to be neutralized.
5. No support muscle, the fore arm and the hand are just going alone for the ride.
June 3, 2009 at 11:56 am
Hi CZ,
Hmmm…. What is your mover? If we said that the supraspinatus can also flex the arm at the shoulder joint, would that allow you to find a neutralizer? What about fixator??? And I think that it is conceivable to find a support muscle in this scenario.
Joe
May 20, 2009 at 11:45 am
Hmm…
1. what is the position of the body in this scenario?
2. Can you name a posible antagonist muscle in this scenario?
3. Would that antagonist muscle be working?
4. What about a neutralizer?
5. what about a support muscle?
Joe
May 22, 2009 at 3:44 pm
Hi Joe.
Scenario: running (at a conversational pace) on a flat surface without elevation (i.e., Central Park outer circle)
Action in question: Flexion of the right thigh @ the hip joint.
Fixed attachment: pelvis
Mobile attachment: thigh
Gravity’s role: antagonist
Major muscle groups used: hip flexors. I specifically chose to look at the psoas major.
Mover: Psoas Major
Stabilizer: Rectus abdominus (posterior tilt of pelvis @ lumbosacral joint keeps ant. tilt of pelvis @ hip joint action of psoas major in check)
Neutralizer: TFL (medial rot. of the right thigh @ hip joint keeps lateral rotation of thigh @ hip joint action of psoas major in check).
Support: Left Psoas Major, working as a mutual neutralizer?, left lateral rotation of trunk @ spinal joints keeps right lateral rotation of trunk @ spinal joint action of psoas major in check. hmmmmm. also, I wonder if the right QL is working as a support and/or stabilizer to the right psoas major (extension of trunk @ spinal joints) keeps psoas major’s flexion of trunk @ spinal joint in check)???
Would elevation make a huge difference in how the right psoas major works in this scenario?
May 26, 2009 at 3:27 pm
Hi Maria,
All looks good except the ‘support’ part. :)Remember, a support muscle works somewhere else to support the body (so it does not fall with gravity).
Joe
June 9, 2009 at 1:21 pm
Hi Joe,
I need to provide you with a support muscle for the right psoas major when the action in question is flexion of the right thigh at the hip joint. I’m choosing the left soleus as the support muscle because during the action in question, the left leg is receiving/supporting the body’s weight as the right leg lifts off the ground.
June 10, 2009 at 12:04 am
Hi Maria,
So you are saying that as the right thigh lifts into flexion at the hip joint, that the left soleus contracts, I assume to prevent dorsiflexion of the left ankle joint?
Joe
May 25, 2009 at 1:28 am
1. The position is in standing upright at the base of a staircase, while lifting the right thigh, flexing at the hip joint. Gravity is antagonistic to this action. The thigh alone is moving and all else is in anatomical position.
2. The mover contracting concentrically is the tensor fascia latae.
3. The antagonist, though not working, is the gluteus maximus.
4.A fixator would be the rectus abdominis.
5.A neutralizer, cancelling out abduction of the mobile attachment would be pectineus.
6. A support muscle would be the erector spinae group, keeping the trunk in an upright position.
Suzanne M.
May 26, 2009 at 3:28 pm
Hi Suzanne,
All is most likely good, but can you give a one-sentence explanation for why you chose the specific muscle in each case?
Joe :)
May 28, 2009 at 10:39 pm
Certainly.
The gluteus maximus extends the thigh at the hip joint, therefore antagonistic to flexion of the thigh at the hip joint by the TFL.
The rectus abdominis posteriorly tilts the pelvis at the hip joint, “fixating” the fixed attachment, the pelvis.
The pectineus (the neutralizer) adducts the thigh at the hip joint cancelling out possibile abduction of the thigh at the hip joint by the TFL.
The erector spinae extends the trunk at the spinal joints keeping the anterior pulling force of the thigh from tilting the trunk into flexion.
May 26, 2009 at 1:45 am
1:Joint action
Flexion of forearm at the elbow joint
2:Mover
Biceps Brachii
3:Antagonist
Triceps Brachii
4:Fixator
Deltoid
5:Neutralizer
Brachioradialis
6:Support
Brachialis
May 26, 2009 at 3:29 pm
Hi Siam,
Same idea as with comment above. Please give a one sentence long explanation for why you chose each muscle that you did.
And, is the brachialis a support muscle in this scenario???
Joe :)
May 26, 2009 at 8:48 pm
1:Joint action
Flexion of forearm at the elbow joint
2:Mover
Biceps Brachii because when it contracts it flexes the forearm
3:Antagonist
Triceps Brachii because it is eccentrically contracting or lengthening because it does extension
4:Fixator
Deltoid because it is keeping the arm laterally rotated
5:Neutralizer
Brachioradialis because it cancels out supination and pronation of the forearm when flexion occurs at the elbow joint.
6:Support
Triceps Brachii because it concentrically shortens to prevent the forearm from extending too quickly with gravity which in this scenerio is an antagonist
May 26, 2009 at 6:17 am
AIQ: gently kicking a ball….Extension of the leg at the knee joint
Position of the body: standing erect, thigh slightly flexed, leg flexed in anticipation of the kick
Mover: Gravity/Rectus Femoris
Antagonist: Gastrocnemius
Fixator: long head of biceps femoris
Neutralizer: no neutralizer needed
Support Muscle: Adductor Magnus
May 26, 2009 at 3:30 pm
Hi Jana,
Why is the adductor magnus a support muscle?
and, can you give a one-sentence explanation for why you chose each specific muscle that you did?
Joe :)
June 16, 2009 at 8:57 pm
Extension of the leg @ the knee joint.
Mover: Rectus Femoris; it’s number one action is extension of the leg @ the knee joint
Antagonist: Gastrocnemius; does the opposite action of the Rectus Femoris, which is flexion of the leg @ the knee joint.
Fixator: I chose the long head of Biceps Femoris because it will counteract the anterior tilt of the pelvis @ the hip joint due to it being a posterior tilter of the pelvis @ the hip joint.
Support Muscle: I had a hard time with because I over-thought the answer. Adductor Magnus would hold the thigh in place as an extensor of the thigh @ the hip joint, while the leg was flexing @ the knee joint. If the thigh flexed at the same time the leg extended, there would be more power to the action due to both the thigh and leg moving in the same direction, and you would not get a gentle kick of the ball.
May 27, 2009 at 3:48 am
action: dorsiflexion of the foot at the ancle joint.
mover:tibialis anterior
antigonist:gastrocnemius
fixator:soleus
support:fibularis longus
May 27, 2009 at 11:56 am
Mike,
why is your fixator a fixator, and your support a support muscle? What about a neutralizer?
Joe
May 27, 2009 at 5:21 am
scenario/action in question/position of body:
Flexion of arm @ elbow joint. Hand is holding onto an immovable bar – I thought this would add some flavor.
Fixed attachment – forearm
Mobile attachment – arm
gravity’s role – antagonist
mover – brachialis
stabilizer – triceps brachii
neutralizer – brachioradialis
May 27, 2009 at 11:57 am
Caitlen,
How are the triceps brachii and brachioradialis acting as stabilizer and neutralizer? what about a support muscle?
Joe
June 16, 2009 at 1:21 am
scenario/action in question/position of body:
Flexion of forearm @ elbow joint. Hand is holding onto an immovable bar
Fixed attachment – forearm is fixed because it stops the unwanted action at the fixed attachment (it doesn’t move in this action so it’s not the mobile attachment/neutralizer)
antagonist – triceps brachii because it extends the forearm at the elbow joint…opposite of the action in question
neutralizer – there is none
mover – brachialis because it flexes the arm at the elbow joint (action in question)
support muscle – deltoid holds the arm in position while action in question is working
stabilizer – i was incorrect here before. The fixator and support are stabilizers.
May 31, 2009 at 2:57 pm
Flexing the trunk at the hip joint(action)crunchs, with my thigh bent at knee joint.
Mover is the Rectus Abdominus because it can flex the trunk at the hip joint causing the action in question.
Antagonist is gravity and the weight of my body causing the opposite action of the action in question, pulling my trunk down.
Fixator is the Psoas Major(anterior tilt of pelvis at hip joint) stopping the posterior tilt of the pelvis at the hip joint(fixed body part) caused by the rectus abdominus.
Neutralizer is the External Abdominal Oblique right and left contracting eccentrically to stop lateral flexion of trunk at hip joint. ??
Support is SCM holding my neck(cervical spine) up as it isometrically contracts.
Synergist i picked the External Abnominal Oblique again because it can also do flexion of the trunk at hip joint. working with the mover muscle to create the action in question (flexion of trunk at hip joint) ??
June 3, 2009 at 11:50 am
Hi Flavia,
The trunk cannot move at the hip joint. Do you mean the pelvis anteriorly tilting at the hip joint or do you mean the trunk flexing at the spinal joints???
Joe
June 2, 2009 at 10:09 pm
forearm is in anatomial position and im slowly lifting the forearm in flexion. POSSIBLE MOVER-(biceps brachii)it flexs the elbow at the humeroulnar joint.ANTAGONIST(GRAVITY)FIXATOR (NONE)NEUTRALIZER (TRICEP BRACHII)it extends the elbow at the humeroulnar joint SUPPORT (extensor carpiradials longus) assist to flex elbow
at humeroulnar joint
June 3, 2009 at 11:53 am
Hi TC,
Why can’t there be a fixator? Isn’t it possible that the arm could move into flexion at the elbow joint??? wouldn’t the triceps brachii be an antagonist, not a neutralizer? And, support is not the same as synergist.
Joe
June 11, 2009 at 12:43 am
Joe,
To be honest, I’m bewildered about the muscle that would “support” the right psoas major when I do flexion of the right thigh at the hip joint. When I think of how the body would potentially fall over because of the right thigh flexion, it’s either because the trunk comes flexing forward or the left leg would not support the weight of the rest of the body. That’s why I picked a muscle on the left side of the leg; I was going down the road of thinking I needed a leg to keep the body from falling, and left soleus is one of the muscles in the left leg that could contribute to supporting the body.
M
June 11, 2009 at 8:56 pm
Maria,
Your reasoning is sound. I just want/need you to explain in specific joint terminology why the soleus is the muscle you chose…
Joe
June 11, 2009 at 3:16 am
flexion of the forearm at the elbow joint (picking up a dumbell) Antagonist: brachialis
Fixed attach: Arm Mobile: forearm
im confused joe =[
June 11, 2009 at 8:44 pm
Does the brachialis have another action upon the forearm at the elbow joint that needs to be neutralized? Does its other attachment possible need to be stabilized. How would the body need to be supported if the body goes into the position that you are creating here?
Joe
June 11, 2009 at 3:38 am
A Tennis Backhand
Extension of the Forearm at the Elbow Joint
Extension of the Hand at the Wrist Joint
Extension of the Arm at the Shoulder Joint
The individual will be in an active standing position with a possible squat.
The Extension of the Forearm will be executed by the Triceps Brachii coupled with the Wrist Extensor Group for Extension of the Hand at the Wrist Joint.
I am assuming that gravity plays a large role in this as far as the Support and Fixator muscles go.
The Brachioradialis along with the Flexi Carpi Radialis and Biceps Brachii will have the role of Fixators to conquer the force of gravity and keep the arm stable.
To support this the Rotator Cuff will engage to keep the Arm and Forearm level to the ground with the Deltoid being a major factor in this for two reasons.
1)To keep the arm Abducted as a supporter and…
2)2) The Posterior Deltoid will actually be a mover in this to generate more force as an Extensor of the Arm at the Shoulder Joint.
My only question in this Joe is, I can’t think of a role of a Neutralizer.
Patrick J.
June 11, 2009 at 8:49 pm
Hi Patrick,
Re neutralizer, is there a second action of the triceps brachii upon the forearm at the elbow joint that would be unwanted and therefore need to be neutralized?
Re gravity, I am not sure that it has a role. Is the swing horizontal and parallel with the ground?
Re Can you explain better what the fixation force is stopping, using specific joint action terminology?
Joe
June 11, 2009 at 3:59 am
Hiya Joe,
The agonist muscle I am singling out for this scenario– Satorius.
1. Scenario: At the gym, standing, in kickboxing class. Keeping the right leg straight and steady as I lift the left leg to do a side kick.
Action in question: abduction of the thigh at the hip joint.
2. Possible antagonist would be gracilis of adductor group.
3. Would that antagonist muscle be working? No, the adductor magnus would relax as the mover- satorius contracts.
4. What about a fixator?
A fixator could be biceps femoris, as can stop the unwanted action in question, flexion of the thigh at the hip joint
5. What about a neutrilizer?
A would be vastus lateralis that extends the knee at the knee joint, to stop the unwanted action of flexion of the leg at the knee joint.
6.. what about a support muscle?
All of the anterior and posterior thigh muscles could be considered support muscles in this scenario.
June 11, 2009 at 8:52 pm
Sharon.
Stopping an action of the thigh is the role of a “fixator” because the thigh is the mobile attachment, right?
Why are the thigh muscles support muscles? Which side of the body? Pick one and explain in joint action terminology why it is a support muscle.
joe
June 12, 2009 at 5:04 am
Joe,
In this scenario, the anterior and posterior (specifically the quads and hamstrings) musculature of the right lower extremity would be support muscles.
These muscles hold the body in position via isometric contraction at the knee joint to keep the body from falling/crumpling over as the action in question, abduction of the thigh at the hip joint, is occurring on the left leg.
Gravity could also be a support force.
June 11, 2009 at 9:59 am
action- extention of leg at the knee joint
agonist-quadriceps (3 vasterlatis muscles)
antagonist-hamstrings
no fixator/stabilizer (does not cross hip joint and has no other unwanted action)
support muscle- soleus muscle posture muscle-stabilizer
June 11, 2009 at 8:55 pm
Jenny,
Which side is moving? what is the position of the person (seated, standing, lying, etc)?
If there is no stabilizer, then are you saying that there is no other attachment of the vastus muscles other than the leg (i.e., tibia)??? Hint: There is always a possible stabilizer.
Soleus on which side?
Joe
June 19, 2009 at 12:53 am
Action: Supination against gravity with the elbow flexed 90 degrees. ex- using a screwdriver
Agonist: Biceps Brachii
Synergist: Supinator
Antagonist: Pronator Teres, pronator quadratus
Neutralizer: Triceps Brachii
Fixators: Rotator cuff Muscles
October 21, 2009 at 4:11 pm
Great way to get class participation in learning. Well done.
November 3, 2011 at 10:52 pm
tennis blx…
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