7) Muscle soreness and muscle cramps

Question 1

What is Acute Muscle Soreness?

Answer 1

Acute Muscle soreness = Soreness that occurs during or immediately after physical activity
* Can occur in any muscle placed under stress
* Subsides within a few minutes to a few hours
* May be due to tissue edema or accumulation of end products of exercise (ie. H+)
- Not due to muscle damage

Question 2

Acute Muscle soreness May be due to ? or ?

Answer 2

Acute Muscle soreness May be due to tissue edema or accumulation of end products of exercise (ie. H+)

Question 3

What is Delayed onset muscle soreness (DOMS)

Answer 3

Delayed onset muscle soreness (DOMS)
- Pain that starts 24-72 hours after intense exercise
* Disappears in 5 – 7 days post-exercise

• Symptoms: Mild muscle soreness to inability to perform certain activities
• Impaired muscular force capacities and increased soreness, pain, stiffness, swelling and altered biomechanics to the adjacent joints

Question 4

What are symptoms of Delayed Onset Muscle Soreness (DOMS)?

Answer 4

Symptoms: Ranges from Mild muscle soreness to inability to perform certain activities
Impaired muscular force capacities and increased:
* soreness,
* pain,
* stiffness,
* swelling and
* altered biomechanics to the adjacent joints

Delayed onset muscle soreness (DOMS)
- Pain that starts 24-72 hours after intense exercise
* Disappears in 5 – 7 days post-exercise

Question 5

What causes DOMS?

Answer 5

• Ultrastructural damage of muscle cells (Z-band streaming and broadening which destroys sarcomeres) leads to apoptosis and local inflammatory response
• Biopsy analysis of eccentric strained muscle tissue has proved a loss of myofibrillar integrity with Z-band streaming and a disruption of sarcomeres in the myofibrils

Question 6

Causes of DOMS
* Ultrastructural damage of muscle cells (? and ? which destroys ?) leads to ? and local ? response
* Biopsy analysis of eccentric strained muscle tissue has proved a loss of ? integrity with ? streaming and a disruption of ? in the myofibrils

Answer 6

• Ultrastructural damage of muscle cells (Z-band streaming and broadening which destroys sarcomeres) leads to apoptosis and local inflammatory response
• Biopsy analysis of eccentric strained muscle tissue has proved a loss of myofibrillar integrity with Z-band streaming and a disruption of sarcomeres in the myofibrils

Question 7

What types of exercise most often results in DOMS?

Answer 7

• Unaccustomed strenuous exercise, especially exercise focusing on eccentric contractions (lengthening contraction);
• exercise focusing on concentric and isometric contractions see less DOMS

Question 8

Why does DOMS most often follow eccentric-focused exercise?

Answer 8

Eccentric MM contractions have a greater disruption to the structural elements of muscle and connective tissue than concentric/isometric exercise

Eccentric = More damage

Question 9

What is Mechanical Hyperalgesia?

Answer 9

Tenderness and movement related pain
- typical sign of DOMS

DOMS = delayed onset muscle soreness

Question 10

What two things happen in the muscle to cause DOMS?

Answer 10

1) Structural Damage (microtrauma)
2) Inflammation

(1) Structural Damage (microtrauma)
- Muscle specific enzymes in blood suggest damage to MM membranes
- Muscle cell membranes (sarcolemma) rupture or Z-disk streaming (Streaming or smearing of the Z band, which is then no longer confined to a narrow zone which bisects the I band)
- Muscle Pain, tenderness, swelling

(2) Inflammation
- Substances (eg neutrophils, macrophages) released from injured muscle initiate inflammatory process

Question 11

What two things happen (within muscle) in association with DOMS?

Answer 11

1) Structural Damage (microtrauma)
2) Inflammation

(1) Structural Damage (microtrauma)
- Muscle specific enzymes in blood suggest damage to MM membranes
- Muscle cell membranes (sarcolemma) rupture or Z-disk streaming (Streaming or smearing of the Z band, which is then no longer confined to a narrow zone which bisects the I band)
- Muscle Pain, tenderness, swelling

(2) Inflammation
- Substances (eg neutrophils, macrophages) released from injured muscle initiate inflammatory process

Question 12

DOMS

(1) Structural Damage (microtrauma)
- ? in blood suggest damage to MM membranes
- ? rupture or ? streaming
- Resulting in: ?, ?, ?

(2) Inflammation
- Substances (eg ?, ?) released from ? initiate inflammatory process

Answer 12

(1) Structural Damage (microtrauma)
- Muscle specific enzymes (eg high creatine kinase) in blood suggest damage to MM membranes
- sarcolemma rupture or Z-disk streaming
- Resulting in: Muscle Pain, tenderness, swelling

(2) Inflammation
- Substances (eg neutrophils, macrophages) released from injured muscle initiate inflammatory process

Sarcolemma = Muscle cell membranes
Z-disc streaming = Streaming or smearingof the Z band - no longer confined to a narrow zone bisecting the I band

Question 13

Sequence of Events in DOMS

(1) High ? in contractile-elastic system in muscle causes structural damage to muscle and cell membrane
Excessive strain on ?
Can damage ?
Sarcomere comes apart -> Damage to ?

Answer 13

(1) High (mechanical) tension in contractile-elastic system in muscle causes structural damage to muscle and cell membrane (sarcolemma).
Excessive strain on connective tissue
Can damage Sarcoplasmic Reticulum (Ca++ stores)
Sarcomere comes apart -> Damage to PM (Sarcolemma)

(1) High (mechanical) tension in contractile-elastic system in muscle causes structural damage to muscle and cell membrane (sarcolemma). Excessive strain on connective tissue.
(2) Cell membrane damage disturbs calcium homeostasis, inhibiting cellular respiration. High calcium activates proteolytic enzymes that degrade the Z-lines.
(3) Elevation in neutrophils that participate in inflammation.
(4) Products of macrophage activity and intracellular contents accumulate outside cells resulting in stimulation of free nerve endings in muscle. This process is accentuated in eccentric exercise.
(5) Fluid and electrolytes move into the area (edema) causing swelling and activating pain receptors; muscle spasms may occur.

Question 14

Sequence of Events in DOMS

(1) Tension -> Damage to Sarcoplasmic Reticulum and Sarcolemma (PM):
(2) disturbs ? homeostasis,
SR damage → ↑? in sarcoplasm
- inhibits proteins involved in ? (ATP production)
- activates proteolytic enzymes that degrade the Z-lines.

Answer 14

(1) Tension -> Damage to Sarcoplasmic Reticulum and Sarcolemma (PM):
(2) disturbs calcium homeostasis,
SR damage → ↑Ca++ in sarcoplasm
- inhibits proteins involved in cellular respiration (ATP production)
- activates proteolytic enzymes that degrade the Z-lines.

(1) High (mechanical) tension in contractile-elastic system in muscle causes structural damage to muscle and cell membrane (sarcolemma). Excessive strain on connective tissue.
(2) Cell membrane damage disturbs calcium homeostasis, inhibiting cellular respiration. High calcium activates proteolytic enzymes that degrade the Z-lines.
(3) Elevation in neutrophils that participate in inflammation.
(4) Products of macrophage activity and intracellular contents accumulate outside cells resulting in stimulation of free nerve endings in muscle. This process is accentuated in eccentric exercise.
(5) Fluid and electrolytes move into the area (edema) causing swelling and activating pain receptors; muscle spasms may occur.

Question 15

Sequence of Events in DOMS

What happens when the Sarcoplasmic Reticulum is damaged?

Answer 15

(1) Tension -> Damage to Sarcoplasmic Reticulum and Sarcolemma (PM):
(2) disturbs calcium homeostasis,
SR damage → ↑Ca++ in sarcoplasm
- inhibits proteins involved in cellular respiration (ATP production)
- activates proteolytic enzymes that degrade the Z-lines

(1) High (mechanical) tension in contractile-elastic system in muscle causes structural damage to muscle and cell membrane (sarcolemma). Excessive strain on connective tissue.
(2) Cell membrane damage disturbs calcium homeostasis, inhibiting cellular respiration. High calcium activates proteolytic enzymes that degrade the Z-lines.
(3) Elevation in neutrophils that participate in inflammation.
(4) Products of macrophage activity and intracellular contents accumulate outside cells resulting in stimulation of free nerve endings in muscle. This process is accentuated in eccentric exercise.
(5) Fluid and electrolytes move into the area (edema) causing swelling and activating pain receptors; muscle spasms may occur.

Question 16

Sequence of Events in DOMS

Tension → SR damage → ↑Ca++ in sarcoplasm → ↓Cell. Resp // ↑Proteolytic enzymes → ↓ATP production // degradation of Z-lines
(3) Elevation in neutrophils → attract ? // participate in ?

Answer 16

Tension → SR damage → ↑Ca++ in sarcoplasm → ↓Cell. Resp // ↑Proteolytic enzymes → ↓ATP production // degradation of Z-lines
(3) Elevation in neutrophils that attract macrophages and participate in inflammation

(1) High (mechanical) tension in contractile-elastic system in muscle causes structural damage to muscle and cell membrane (sarcolemma). Excessive strain on connective tissue.
(2) Cell membrane damage disturbs calcium homeostasis, inhibiting cellular respiration. High calcium activates proteolytic enzymes that degrade the Z-lines.
(3) Elevation in neutrophils that participate in inflammation.
(4) Products of macrophage activity and intracellular contents accumulate outside cells resulting in stimulation of free nerve endings in muscle. This process is accentuated in eccentric exercise.
(5) Fluid and electrolytes move into the area (edema) causing swelling and activating pain receptors; muscle spasms may occur.

Question 17

Sequence of Events in DOMS

Tension → SR damage → ↑Ca++ in sarcoplasm → ↓Cell. Resp // ↑Proteolytic enzymes → ↓ATP production // degradation of Z-lines → ↑neutrophils → ↑macrophages and inflammation

(4) Products of macrophage activity and intracellular contents accumulate outside cells resulting in stimulation of ? in muscle. This process is accentuated in ? exercise

Answer 17

Tension → SR damage → ↑Ca++ in sarcoplasm → ↓Cell. Resp // ↑Proteolytic enzymes → ↓ATP production // degradation of Z-lines → ↑neutrophils → ↑macrophages and inflammation

(4) Products of macrophage activity and intracellular contents accumulate outside cells resulting in stimulation of free nerve endings (nociceptors) in muscle. This process is accentuated in eccentric exercise

(1) High (mechanical) tension in contractile-elastic system in muscle causes structural damage to muscle and cell membrane (sarcolemma). Excessive strain on connective tissue.
(2) Cell membrane damage disturbs calcium homeostasis, inhibiting cellular respiration. High calcium activates proteolytic enzymes that degrade the Z-lines.
(3) Elevation in neutrophils that participate in inflammation.
(4) Products of macrophage activity and intracellular contents accumulate outside cells resulting in stimulation of free nerve endings in muscle. This process is accentuated in eccentric exercise.
(5) Fluid and electrolytes move into the area (edema) causing swelling and activating pain receptors; muscle spasms may occur.

Question 18

Sequence of Events in DOMS

Tension → SR damage → ↑Ca++ in sarcoplasm → ↓Cell. Resp // ↑Proteolytic enzymes → ↓ATP production // degradation of Z-lines → ↑neutrophils → ↑macrophages and inflammation → stimulation of nociceptors (free nerve endings)

(5) Fluid and electrolytes move into the area (?) causing ? and activating ?; ? may occur

Answer 18

Tension → SR damage → ↑Ca++ in sarcoplasm → ↓Cell. Resp // ↑Proteolytic enzymes → ↓ATP production // degradation of Z-lines → ↑neutrophils → ↑macrophages and inflammation → stimulation of nociceptors (free nerve endings)

(5) Fluid and electrolytes move into the area (edema) causing swelling and activating pain receptors; muscle spasms may occur

(1) High (mechanical) tension in contractile-elastic system in muscle causes structural damage to muscle and cell membrane (sarcolemma). Excessive strain on connective tissue.
(2) Cell membrane damage disturbs calcium homeostasis, inhibiting cellular respiration. High calcium activates proteolytic enzymes that degrade the Z-lines.
(3) Elevation in neutrophils that participate in inflammation.
(4) Products of macrophage activity and intracellular contents accumulate outside cells resulting in stimulation of free nerve endings in muscle. This process is accentuated in eccentric exercise.
(5) Fluid and electrolytes move into the area (edema) causing swelling and activating pain receptors; muscle spasms may occur.

Question 19

DOMS and Performance

What are three causes behind the worsened performance (decreased force-generating capacity) during DOMS?

Answer 19

Reduction in the force-generating capacity of the muscle due to:
(1) Physical disruption of the muscle
(2) Loss of contractile proteins (damaged sarcomere/muscle fibre)
(3) Failure within the excitation-contraction coupling process (Damaged SR → Disruption in Ca++ homeostasis (↑Ca++ in sarcoplasm)

(3) is the primary reason for loss of force
- Even with stimulation of the muscle by alpha motor neuron, because the calcium stores are disrupted, the excitation-contraction coupling process is also disrupted

Question 20

What is the primary reason for the loss of force generating capacity in the muscle during DOMS?

Answer 20

Loss of excitation-contraction coupling process

From disturbance in Calcium homeostasis:
SR damage → ↑Ca++ in sarcoplasm

Alpha-motor neuron stimulation would normally result in release of Ca++ to allow unblocking of myosin binding site
- Instead high calcium in sarcoplasm activates proteolytic enzymes and disrupts cellular respiration/ATP production

Question 21

DOMS and performance

Muscle ? resynthesis is impaired as MM undergoes repair

Answer 21

Muscle glycogen resynthesis is impaired as MM undergoes repair

Glycogen = stored glucose
- Source for ATP
- Thus disturbing glycogen resynthesis = disturb ATP production

Question 22

Rhabdomyolysis

What is Rhabdomyolysis?

Answer 22

Rhabdomyolysis = Breakdown (dissolution) of striated muscle

More extreme than doms

Muscle injury → leakage of MM cell contents (electrolytes, myoglobin) and other sarcoplasmic proteins (Creatine phosphokinase (CPK), lactate dehydrogenase) into circulation and extracellular fluid

Skeletal mm damage due to several causes including:
- strenuous exercise
- heat stroke
- crush injury
- lack of blood flow (prolonged large reduction)

Symptoms:
* Muscle swelling
* Weak, tender and sore muscles * Dark tea-coloured urine
* Decreased urination
* Nausea
* Loss of consciousness

Question 23

Rhabdomyolysis

Rhabdomyolysis:
Muscle injury so severe it leads to: ?

Answer 23

Muscle injury → leakage of MM cell contents (electrolytes, myoglobin) and other sarcoplasmic proteins (Creatine phosphokinase (CPK), lactate dehydrogenase) into circulation and extracellular fluid

Myoglobin - processed in kidney
[Myoglobin]+++ → exceeds kidney’s handling capacity → kidney blockage → kidney failure

Rhabdomyolysis = Breakdown (dissolution) of striated muscle
- More extreme than doms

Skeletal mm damage due to several causes including:
- strenuous exercise
- heat stroke
- crush injury
- lack of blood flow (prolonged large reduction)

Symptoms:
* Muscle swelling
* Weak, tender and sore muscles * Dark tea-coloured urine
* Decreased urination
* Nausea
* Loss of consciousness

Question 24

Rhabdomyolysis

Rhabdomyolysis:
What is important regarding the leakage of muscle cell contents into bloodstream during rhabdomyolysis?

Muscle injury → leakage of MM cell contents (electrolytes, myoglobin) and other sarcoplasmic proteins (Creatine phosphokinase (CPK), lactate dehydrogenase (LDH)) into circulation and extracellular fluid

Answer 24

Myoglobin - processed in kidney
[Myoglobin]+++ → exceeds kidney’s handling capacity → kidney blockage → kidney failure

• Can test blood for muscle contents (high CPK / LDH) to check for mm damage

Rhabdomyolysis = Breakdown (dissolution) of striated muscle
- More extreme than doms

Skeletal mm damage due to several causes including:
- strenuous exercise
- heat stroke
- crush injury
- lack of blood flow (prolonged large reduction)

Symptoms:
* Muscle swelling
* Weak, tender and sore muscles * Dark tea-coloured urine
* Decreased urination
* Nausea
* Loss of consciousness

Question 25

Rhabdomyolysis

Rhabdomyolysis:

Skeletal mm damage due to several causes including:
- ?
- ?
- ? injury
- lack of ? (prolonged large reduction)

Answer 25

Skeletal mm damage due to several causes including:
- strenuous exercise
- heat stroke
- crush injury
- lack of blood flow (prolonged large reduction)

Rhabdomyolysis = Breakdown (dissolution) of striated muscle
- More extreme than doms

Myoglobin - processed in kidney
[Myoglobin]+++ → exceeds kidney’s handling capacity → kidney blockage → kidney failure

• Can test blood for muscle contents (high CPK / LDH) to check for mm damage

Symptoms:
* Muscle swelling
* Weak, tender and sore muscles * Dark tea-coloured urine
* Decreased urination
* Nausea
* Loss of consciousness

Question 26

Rhabdomyolysis

Rhabdomyolysis:

Symptoms?
* Muscle symptoms?
* Kidney symptoms?

Answer 26

Symptoms:
* Muscle swelling
* Weak, tender and sore muscles
* Dark tea-coloured urine
* Decreased urination
* Nausea
* Loss of consciousness

Rhabdomyolysis = Breakdown (dissolution) of striated muscle → release of mm cell contents (electrolytes, myoglobin, creatine phosphokinase, lactate dehydrogenase) into circulation and ecf
- More extreme than doms

Myoglobin - processed in kidney
[Myoglobin]+++ → exceeds kidney’s handling capacity → kidney blockage → kidney failure

• Can test blood for muscle contents (high CPK / LDH) to check for mm damage

Skeletal mm damage due to several causes including:
- strenuous exercise
- heat stroke
- crush injury
- lack of blood flow (prolonged large reduction)

Question 27

Rhabdomyolysis

Why is Rhabdomyolysis more severe than DOMS?

Answer 27

Myoglobin damages kidneys in large quatities; if kidneys cannot get rid of myoglobin fast enough, kidney failure and death can occur

Rhabdomyolysis = Breakdown (dissolution) of striated muscle → release of mm cell contents (electrolytes, myoglobin, creatine phosphokinase, lactate dehydrogenase) into circulation and ecf
- More extreme than doms

Myoglobin - processed in kidney
[Myoglobin]+++ → exceeds kidney’s handling capacity → kidney blockage → kidney failure

• Can test blood for muscle contents (high CPK / LDH) to check for mm damage

Skeletal mm damage due to several causes including:
- strenuous exercise
- heat stroke
- crush injury
- lack of blood flow (prolonged large reduction)

Question 28

Rhabdomyolysis

What is Exertional Rhabdomyolysis?

Answer 28

“Caused by exercise”
- Breakdown and necrosis of striated skeletal muscle after engaging in physical activity

Seen in spin classes/boot camps
- Repetitive use of large mm groups (gluteus maximus and quadriceps muscles)

Risk Factors:
- intensity of exercise
- conditioning of participant
- hydration
- body temperature

Rhabdomyolysis = Breakdown (dissolution) of striated muscle → release of mm cell contents (electrolytes, myoglobin, creatine phosphokinase, lactate dehydrogenase) into circulation and ecf
- More extreme than doms

Myoglobin - processed in kidney
[Myoglobin]+++ → exceeds kidney’s handling capacity → kidney blockage → kidney failure

• Can test blood for muscle contents (high CPK / LDH) to check for mm damage

Skeletal mm damage due to several causes including:
- strenuous exercise
- heat stroke
- crush injury
- lack of blood flow (prolonged large reduction)

Question 29

Rhabdomyolysis

What is Exertional Rhabdomyolysis?

Answer 29

“Caused by exercise”
- Breakdown and necrosis of striated skeletal muscle after engaging in physical activity

Seen in spin classes/boot camps
- Repetitive use of large mm groups (gluteus maximus and quadriceps muscles)

Risk Factors:
- intensity of exercise
- conditioning of participant
- hydration
- body temperature

Rhabdomyolysis = Breakdown (dissolution) of striated muscle → release of mm cell contents (electrolytes, myoglobin, creatine phosphokinase, lactate dehydrogenase) into circulation and ecf
- More extreme than doms

Myoglobin - processed in kidney
[Myoglobin]+++ → exceeds kidney’s handling capacity → kidney blockage → kidney failure

• Can test blood for muscle contents (high CPK / LDH) to check for mm damage

Skeletal mm damage due to several causes including:
- strenuous exercise
- heat stroke
- crush injury
- lack of blood flow (prolonged large reduction)

Question 30

Rhabdomyolysis

Exertional Rhabdomyolysis: Breakdown and necrosis of striated skeletal muscle after engaging in physical activity (caused by exercise)
- Most often seen during what types of exercise?
- Risk factors (5)

Answer 30

“Caused by exercise”
- Breakdown and necrosis of striated skeletal muscle after engaging in physical activity

Seen in spin classes/boot camps
- Repetitive use of large mm groups (gluteus maximus and quadriceps muscles)

Risk Factors:
- intensity of exercise
- conditioning of participant
- hydration
- body temperature
- drugs such as NSAIDS because of impact on kidneys

Rhabdomyolysis = Breakdown (dissolution) of striated muscle → release of mm cell contents (electrolytes, myoglobin, creatine phosphokinase, lactate dehydrogenase) into circulation and ecf
- More extreme than doms

Myoglobin - processed in kidney
[Myoglobin]+++ → exceeds kidney’s handling capacity → kidney blockage → kidney failure

• Can test blood for muscle contents (high CPK / LDH) to check for mm damage

Skeletal mm damage due to several causes including:
- strenuous exercise
- heat stroke
- crush injury
- lack of blood flow (prolonged large reduction)

Question 31

Exercise associated muscle cramps (EAMC)

What is the definition of exercise associated muscle cramps (EAMC)?

Answer 31

Exercise associated muscle cramps: a temporary involuntary contraction of skeletal muscle that is intense and painful
- can occur during or immediately after muscular exercise or during sleep
- Most common in endurance events
- Vary in intensity and duration

Hard to study in lab (random == hard to induce)

Question 32

Exercise associated muscle cramps (EAMC)

Exercise associated muscle cramps (EAMC)
- can occur?
- Most common during what type of exercise?
- Vary in ? and ?

Exercise associated muscle cramps: a temporary involuntary contraction of skeletal muscle that is intense and painful

Answer 32

• can occur during or immediately after muscular exercise or during sleep
• Most common in endurance events
• Vary in intensity and duration

Hard to study in lab (random == hard to induce)

Question 33

What are two proposed mechanisms of Exercise Associated Muscle Cramps (EAMC)?

Answer 33

Proposed mechanisms of EAMC:
1. Electrolyte depletion theory: disturbance of water and salt balance
2. Altered neuromuscular control theory

Proposed mechanisms of EAMC:
1. Electrolyte depletion theory: disturbance of water and salt balance
* Sweating causes spontaneous muscle contractions due to loss of normal resting membrane potential
* Cramp is often associated with large sweat losses during prolonged exercise in the heat, but can occur in cool environments with little or no sweat loss
* Sweat loss alone and the consequent disturbances of electrolyte balance cannot account for all cramps

3. 2. Altered neuromuscular control theory:
      * Muscle fatigue causes abnormal activity of the muscle spindle and Golgi tendon organ
      * Abnormal discharge of alpha motor neuron drive to the afflicted muscles
      * No prevention strategy or treatment is consistently effective

Question 34

EAMC

What is the electrolyte depletion theory?
- Disturbance of ? balance
- ? causes spontaneous MM contractions due to loss of ?
- Cramp is often associated with large ? losses during prolonged exercise in the heat, but can occur in cool environments with little or no sweat loss
- ? alone and the consequent disturbances of ? balance cannot account for all cramps

Answer 34

One Theory behind exercise associated muscle cramps
- Disturbance of water and salt balance
- Sweating causes spontaneous MM contractions due to loss of normal resting membrane potential
- Cramp is often associated with large sweat losses during prolonged exercise in the heat, but can occur in cool environments with little or no sweat loss
- Sweat loss alone and the consequent disturbances of electrolyte balance cannot account for all cramps

2. Altered neuromuscular control theory:
   * Muscle fatigue causes abnormal activity of the muscle spindle and Golgi tendon organ
   * Abnormal discharge of alpha motor neuron drive to the afflicted muscles
   * No prevention strategy or treatment is consistently effective

Question 35

EAMC

What is the Altered neuromuscular control theory?
* Muscle fatigue causes abnormal activity of the ? and ? (sensory organs)
* Abnormal discharge of ? drive to the afflicted muscles

Answer 35

One Theory behind exercise associated muscle cramps
Altered neuromuscular control theory:
* Muscle fatigue causes abnormal activity of the muscle spindle and Golgi tendon organ (sensory organs)
* Abnormal discharge of alpha motor neuron drive to the afflicted muscles (as mm fatigues, the muscle spindle and golgi tendon organ fall out of sync)

This theory suggests that EAMCs occur when fatigue and other risk factors contribute to a final common pathophysiological pathway to produce an imbalance between excitatory and inhibitory stimuli at the α motor nerve

The muscle spindles and golgi tendon organs are proprioceptive sensory organs:
- muscle spindle: senses the changes in muscle length and the rate of lengthening
- Golgi tendon organ: senses the changes in muscle tension