Week 11 - Muscle & Skeletal Mass Assessment Flashcards
Average muscle mass (MM) % for women
33-36%
Average muscle mass (MM) % for men
40-42%
What changes are there to muscle w/ age?
Loss of muscular fibres
Loss of motor neurones at spinal cord level
Type II fibres = 60%–>30%
⬆️ replacement of muscle w. fat
What are the 3 types of fat according to region?
Subcutaneous/ Superficial belly fat
Visceral/Deep belly fat
Retroperitoneal (back) fat
What is the primary determinant of strength?
MM
Why are obese people stronger than thinner people?
Have higher lean mass.
Why are men stronger than women at the same weight?
They have proportionally more lean mass than women
What is sarcopenia?
Syndrome characterised by progressive + generalised loss of skeletal MM + strength.
Strictly correlated w/ physical disability, poor quality of life + death.
What are the risk factors for sarcopenia
Age
Gender
Level of PA
What % of bone mass is accrued by the end of adolescence?
80-90%
What % of MM is high risk in women?
Less than or equal to 5.75 kg/m^2
What % of MM is high risk in men?
Less than or equal to 8.50 kg/m^2
What % of MM is moderate risk in women?
5.76-6.75 kg/m^2
What % of MM is moderate risk in men?
8.51 - 10.75 kg/m^2
What changes are there to muscle metabolism w/ age?
⬆️ mit. DNA mutation
40%⬇️ in muscle mit. protein synthesis
⬇️ in myosin heavy chain synth.
Why is there a 40% ⬇️ in muscle mit. protein synthesis?
⬇️ oxidative phosphorylation + ATP generation
= Fatiguability
What can be used to estimate skeletal MM?
Anthropometric measures
What anthropometric measures of muscularity are there?
Matiegka (1921)
Martin et al. (1990)
Lee et al. (2000)
What measures are needed to use Matiegka (1921) equation?
Height
Max arm girth (triceps SKF)
Max forearm girth (2forearm SKFs - lateral + anterior)
Mid thigh girth (thigh SKF)
Max calf girth (medial calf SKF)
What is the Matiegka (1921) equation?
MM (kg) = Sum of 4 limb girths corrected by SKF / 8 x height x 6.5 x 0.001
What is the theory of predicting skeletal MM based on?
Corrected diameters of limbs to get muscle cross-sectional area (CSA).
What happens to MM between the ages of 30-65
Gradual decline
~ 1-2%/year
How is muscle area calculated?
pi x ( (circumference/2xpi) - (SKF / 2) ) ^2
What assumptions are there to calculating muscle area?
Perimeters (limb girths) are circular
1 or 2 SKF are representative of the entire subcutaneous layer of that section
