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
What assessment methods are used for FM + FFM?
Body composition
Assessment method - MRI
What is this used for?
Adipose tissue
SkeletalMM
Organ + other soft tissue
Other
Assessment method - Dual X-ray Absorptiometry
What is this used for?
FM, Estimated Skeletal MM, organ + other soft tissue, bone mineral content
FM, non-bone lean body mass + bone mineral content
How electrolyte rich is skeletal muscle?
Electrolyte-rich w/ low resistance
Compare how electricity flows between muscle body H20 + fat
When using BIA
Muscle body H20:
- Low resistance + impedance
= Electricity flows easily = Conductor
Fat:
- High resistance + impedance
= Electricity doesn’t flow = Insulator
Is FFM the same as Skeletal MM?
NO
What % of females FFM is Skeletal MM
47%
What % of males FFM is Skeletal MM
53%
What assumption is there when using stature + bone breadths to predicts skeletal mass?
Constant body density
Approx what % of body mass is skeletal mass?
10-18%
Equations for stature + bone breadths to predict skeletal mass
Matiegka (1921) - F+M
Drinwater et al. (1986) - F+M
Equations for stature + bone breadths to predict skeletal mass
Matiegka (1921) - F+M
S (kg)
[ (Humerus BB + Wrist BB + Femur BB + Ankle BB) / 4 ] x 2 x ht x 1.2kg x 0.001
Equations for stature + bone breadths to predict skeletal mass
Matiegka (1921) - F+M
S (%)
(S kg / body mass) x 100
What 3 stages can be used to ID the stages of bone mass
<17 yrs = Growth
18-35 yrs = Consolidation
> 40 yrs = Involution
