Week 5 - Skeletal Muscle: Fatigue, Cramps and Muscle Soreness Flashcards
What is fatigue? (subjective & objective)
Self-report (subjective)
- Perception, “subjective lack of physical or mental energy (or both) that is perceived by the individual to interfere with usual and desired activties:
Performance (objective)
- Defined as difficulty maintaining force output or muscular control
What are the causes of neuromuscular fatigue?
- Altered neural activation
- Altered muscle metabolism
Where are some potential location of source of fatigue?
- CNS
- PNS
- Neuromuscular junction
- Muscle fibre
What is acute neuromuscular fatigue and what is it mostly associated with?
- Local contractile failure in muscle
- Mostly associated with energy production (energy supply fatigue)
What are the types of substrate depletion with energy supply fatigue?
- Depletion of creatine phosphate
- Depletion of glycogen
Is acute muscle soreness usually associated with tissue damage?
No
What is acute muscle soreness associated with?
Production of lactic acid
What sensation may acute muscle soreness produce?
A burning sensation
What activity helps with the fastest recovery from acute muscle soreness?
Low intensity dynamic activity
When does Delayed Onset Muscle Soreness (DOMS) occur?
24-72 hours after unaccustomed physical activity
What type of muscle actions is DOM associated with?
Eccentric muscle actions (eg. walking downhill, unloading)
What causes DOMS at the muscle level?
Damage to muscle fibres & inflammation (mild strain injury)
What are some characteristics of DOMS? (5)
- Muscles often swollen and stiff
- Produces some weakness and inaccuracy of movement
- Soreness is greatest performing eccentric tasks
- Usually resolves in 2-3 days
- Provides lasting protection for ~6 weeks
What causes muscle soreness due to a strain injury?
Muscle or associated tissue injured
What tissues may be involved in a muscle strain injury?
Muscle fibres and connective tissues
What are common causes of muscle soreness due to strain injury?
Over exertion of muscles or poor mechanics
What is the difference between a sprain and strain?
Sprain: ligament or joint capsule
Strain: muscle &/or tendon
What are common sources of skeletal muscle problems?
- Damage to muscle fibres
- Damage to tendons
- Damage to myotendinous junction
- Damage to tendon attachment to bone
- Spasm due to nerve activation or irritation
What are satellite cells in muscle regeneration?
Type of muscle stem cells that sit between basal lamina and sarcolemma
When are satellite cells stimulated to proliferate?
When cells are substantially damaged (i.e., when not in contact with sarcolemma)
What are the steps in muscle regeneration?
- Damage to muscle fibres
- Cell infiltration & inflammation responses
- Degenerative dismantling of damaged cell
- Proliferation of satellite cells
- Form myotubes then filled with new myofibrils
- Process may take 6 months in human
What is the general process of muscle recovery after injury?
- Muscle degeneration
- Inflammation
- Muscle regeneration
- Muscle remodelling
- Complete/partial muscle maturation/functional repair
What is atrophy and what are the results from it?
- Decrease in muscle fibre size
- Result in loss of force (weakness)
What is the main cause of muscle atrophy with disuse?
It is mostly due to the loss of mechanical “loading” rather than the loss of neural activation.
What muscles experience greater atrophy during bed rest (microgravity)?
Greater atrophy in antigravity muscles and fast-twitch fibres
What are some examples of disuse models?
- Sedentary behaviour (especially in pain states)
- Immobilisation of body segments
- Bed rest (microgravity)
- Aging
- Denervation
What do disuse models represent?
Disuse models represent a range of adaptive changes due to inactivity
What triggers muscle cramps?
Nerve activity
- No cramp without nerve activity
- Unclear whether nerve signal originates locally or in CNS
How does water intake after dehydration affect muscle cramps?
Water intake after dehydration can make muscles more susceptible to cramps due to the dilution of electrolytes. Consuming electrolytes can reverse this effect
What factors increase the incidence of muscle cramps? (5)
- Fatigue
- Dehydration &/or electrolyte imbalance
- Reduced blood flow
- Hypothyroidism
- Pregnancy
When do muscle cramps typically occur?
In the shortened position
What is the acute treatment for muscle cramps?
- Stretch muscle (put in lengthened position)
- Increase blood flow (heat or massage)
What are some causes of Exercise-Induced Transient Abdominal Pain (ETAP)?
- Consistent with irritation of the parietal peritoneum
- Somatic pain (not visceral)
- Aggravated by GIT (food/water ingestion)
- Exercise may alter lymphatic low influencing peritoneal fluid content
How can ETAP be prevented?
- Don’t eat or drink shortly before exercise if prone to ETAP
- Limit fluid intake volume during exercise
- Consider tonicity of fluids
What is the role of cool down after exercise?
- Prevent sudden decrease in venous return
- Provide good blood flow for reduction/removal of muscle metabolites
- Provide some restoration of muscle energy stores
What are the different recovery strategies after exercise? (11)
- Passive rest (including sleep)
- Active recovery (eg. light exercise)
- Stretching
- Myofascial release (eg. massage, foam rolling)
- Electrostimulation (eg. TENS)
- Compression garments
- Immersion (eg. pool recovery)
- Contrast water therapy
- Cryotherapy
- Hyperbaric therapy (eg. 100% oxygen)
- Nutrition
How effective are recovery strategies?
- Most reduced self-perceived ratings of fatigue and muscle soreness
- Few decrease markers of muscle damage
- Massage/myofasical release, cold water immersion and compression garments seem most favourable
