Lecture 13 - Fatigue, Cramps and Muscle Soreness Flashcards
What is performance (objective) fatigue?
Defined as difficulty maintaining force output or muscular control
What is self-reported fatigue?
subjective lack of physical or mental energy (or both) that is perceived by the individual to interfere with usual and desired activities
What is fatigue caused by? (peripheral and central)
– altered neural activation (central) OR
– altered muscle metabolism (peripheral)
What are the potential locations of source of fatigue
– CNS (Brain, spinal cord)
– PNS
– N-M junction
– Muscle fibre (membrane, SR, actin-myosin)
What is the difference in the origin of fatigue between healthy and people w/ disease?
- In healthy humans, fatigue is usually muscular
- In disease, most fatigue is initially due to neural changes (e.g. MS)
What fatigue is associated with resistance training and why?
Acute Neuromuscular Fatigue - Local contractile failure in muscle
* Lack of blood flow
* Lack of oxygen
* Nutrient fatigue or substrate depletion
– Depletion of creatine phosphate
– Depletion of glycogen
* Increased metabolites
* Altered Ca2 + signalling
What are the 3 types of muscle soreness?
- Acute (during activity)
- Delayed onset (24-72 hours after activity)
- Sustained (injury-related)
When does acute muscle soreness occur and what is it associated with?
- Occurs during physical activity
- Not usually associated with tissue damage
- Associated with production of lactic acid
When does delayed onset muscle soreness occur and what is it associated with?
- Occurs 24-72 hours after unaccustomed physical activity (work, leisure, vacation, sport)
- Common when start a new exercise program
Associated with eccentric muscle actions (e.g., walking downhill; unloading) - Associated with damage to muscle fibres & inflammation (Mild strain injury)
What are some characteristics of DOMS?
Characteristics
* Muscles often swollen and stiff
* Produces some weakness and inaccuracy
of movement until soreness resolves
* Soreness is greatest performing
eccentric tasks (e.g., walking downstairs)
* Usually resolves in 2-3 days
How do you limit DOMS in detrained or old populations?
- Use modest loads, especially eccentrically
- Especially important with older people
Are eccentric reps recommended at the initiation of an exercise program? Why/Why not?
No. DOMS will occur to a greater degree - Limit eccentric reps to allow for adaptation to occur initially
Do anti-inflammatories enhance or inhibit the adaptations caused by the training effect of exercise?
Insufficient evidence
– Some evidence that suppressing the inflammatory response compromises the adaptation in young adults
– Some evidence that anti-inflammatories do not inhibit and appear to enhance muscle hypertrophy and strength gains in older adults
What is often the cause of muscle soreness due to strain injury?
Often due to over exertion or poor mechanics
What are some sources of skeletal muscle injury?
MUSCLES: Damage to muscle fibres
TENDONS: Damage to tendons, bone attachments and myotendinous junction
NERVOUS: Spasm (sustained contraction) due to nerve activation or irritation
What are the steps in muscle regeneration?
1) Muscle fibres are damaged
2) Inflammation response
3) Degenerative dismantling of damaged cell
4) Proliferation of satellite cells
5) New myotubes are formed which fill with new myofibrils
How long can muscle regeneration take?
6 months
What is a satellite cell and what does it do in muscle regeneration?
- Type of muscle stem cells that sit between basal lamina and sarcolemma
- Stimulated and proliferate when cells substantially damaged (i.e., when not in contact with sarcolemma)
What is muscle atrophy?
Decrease in muscle fibre size (cross-sectional area)
What can cause atrophy and which is the more common cause?
Loss of mechanical loading (common) and loss of neural innervation
What are the effects of bedrest on muscles?
- Greater atrophy in antigravity muscles
- Greater atrophy in FT fibres
What are some examples of disuse models?
– Sedentary behaviour (pain states more extreme)
– Immobilisation of body segment(s)
– Bed rest (microgravity)
– Aging
– Denervation
What are the causes of muscle cramps?
Causes are not yet known
What is the best working theory of muscle cramps? How do we infer?
- Triggered by nerve activity
– No cramp without nerve activity
– Unclear whether nerve signal originates locally or in CNS
– Mechanical irritation or ischaemia of small nerve bundles?
What effect does water intake have on cramping? What can reverse this effect?
Water intake after dehydration makes muscles more susceptible to cramp (dilution of electrolytes)
– consumption of electrolytes reverse that effect
Incidences of muscle cramps increase with what?
- Fatigue
- Dehydration &/or electrolyte imbalance
- Reduced blood flow
- Hypothyroidism
- Pregnancy
What position do muscle cramps occur?
Only occur with muscle in shortened position
What are the 2 treatments of muscle cramps?
Acute Treatment
– Stretch muscle (i.e. put in lengthened position)
– Increase blood flow (heat or massage)
What is an ETAP?
Stitch - Exercise-induced Transient Abdominal Pain (ETAP)
What causes an ETAP
Characteristics consistent with irritation of parietal peritoneum
Why might exercise influence an ETAP?
Exercise may alter lymphatic flow influencing peritoneal fluid content
How do we prevent stitches from occuring?
- 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 a 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 (help promote blood flow to the muscles and enhance delivery and replenish glycogen stores in the muscle)
What are the most efficacious strategies for muscle recovery?
active recovery, massage, compression, immersion, contrast therapy, cryotherapy
Is massage an objectively efficacious strategy for muscle recovery
No
