Week 3 Flashcards
Which of the following, in relation to dimensional theory, is not a factor that may contribute to a higher scaling of exponent of strength compared to height in children?
a) Recruitment of type I fibres
b) Central inhibition
c) Lower number of motor units
d) Transformation of type I to type II fibres
Lower number of motor units
When do testosterone levels accelerate in boys, increasing in muscle size and strength?
a) When they turn 8
b) Following puberty
c) Unpredictable and varies among children
d) Testosterone levels are constant throughout life
Following puberty
Which one of the following statements is false about muscle growth and strength in children?
a) Muscle strength increases as muscle mass increases
b) Girls and boys have similar muscle strength at the age of 16 years old
c) Girls and boys have similar muscle strength at the age of 8 years old
d) Muscle fibre number fixed soon after birth
Girls and boys have similar muscle strength at the age of 16 years old
According to dimensionality theory, area should relate to HEIGHT by the exponent:
a) 0.67
b) 1.0
c) 2.0
d) 1.5
2.0
When assessing the relationship between body mass and strength, Jaric et al. (2002) found the exponent for prepubescent athletes to be:
a) 0.67
b) 0.61
c) 0.63
d) 1.14
1.14
A motor unit is:
a single α-motor neuron and the muscle fibres it innervates
Nerve conduction velocity:
a) is inversely related to height
b) increases in adults as they age
c) is faster with distal segments than proximal
d) not influenced by axonal diameter
Is inversely related to height
In Dimensionality Theory, height is also used to predict an area or function of the body. In relation to the equation Y=aXb, (describing strength in relation to height) the little b = 2, therefore:
a) The line on the graph is linear and stays horizontal because the number is greater than 1
b) The slope decreases
c) The slope increases linearly
d) The slope gets steeper as height increases because ‘b’ is greater than 1
The slope gets steeper as height increases because ‘b’ is greater than 1
Does muscular strength decline and then plateau with age?
No, it plateaus and then declines
At what age does a rapid strength decline begin?
60s
a-motoneurons receive neural input from what three sources?
- efferent (descending) neuron from the brain
- afferent (sensory) neuron from the tissues
- Spinal neurons (including interneurons)
Premotor cortex function?
Coordinates sensory cues
Supplementary motor area function?
Programming the motor plan
Primary motor cortex function?
initiates and executes movement
In a study of adding and electrical pulse to a contracted muscle, what did they find?
Stimulation of motor nerves produced no additional torque in majority of elderly men and women (in smaller contractions, there was an electrical signal spike, however in maximal contractions there was no addition stimulation seen)
In the study adding electrical impulse to contracted muscles, the finding suggests that…?
Older populations remain able to utilise descending motor pathways for optimal muscle activation (descending control from the motor cortex is not the factor that reduces strength with age)
A study showed that which group of people lost the most strength over 5 years?
The group that became less active (even more so than the group that was sedentary from the start)
A study showed that which group of people lost the least amount of strength over 5 years?
The active group that stayed active
What are three gold standard methods of assessing muscle mass?
- Magnetic resonance imaging (MRI)
- Computed tomography (CT)
- DEXA scanning
Ageing is associated with reductions in muscle _____ and cross sectional area
volume
Ageing is associated with increases in ____ and decreases in _____
non-muscle tissue (fat, CT), muscle mass
Study reported reduction of muscle area by ___% between ages 20-80
40%
Approx. ___% of muscle mass is lost by age 50
10%
Sudden reduction in muscle mass at age ___
60
With age, type ___ fibres reduce, type ___ are less affected
II reduce, I are less affected
List 2 underlying mechanisms that explain the loss of type II fibres with age?
- Inactivity and immobilisation
- Changes in functional demands for force, velocity and duration (less explosive movements)
One study determined that there were much more variability in the type __ fibres in the older individuals than the type __ fibres
I (more variability between people), II (less variability)
There are two possibilities for the decrease of type II fibres in older people…?
- The SIZE of type II fibres decrease
2. The NUMBER of type II fibres decrease
What is collateral sprouting?
Process in which the surviving (intact) motor axons send axon terminals (sprouts) to the denervated muscles in an attempt to reinnervate these muscle fibres and restore muscle power (if type II fibres decrease, it recovers them in type I fibres = more type I)
Nerve conduction velocity (NCV) _____ with age due to ____
decreases, demyelination
Although NCV decreases with age, the contribution of NCV to strength is modest compared with age and ____
age and muscle mass
Reinnervation if damaged nerves is ___ in elderly
slower
With increasing age there is an increase in time to ….(2)?
- time to peak tension
- time to relaxation
(may be due to reduced proportional contribution of type II fibres)
Force can be adjusted by varying the _______ of MUs?
firing rate
Firing refers to the _____ of the neuron
depolarisation (impulse)
Does varying the firing rate of a single MU alter the force only slightly or a lot?
Can alter it a lot
A loss of type II fibres as we age may have a different effect on different muscles – give example?
Some muscles have a higher type II fibre composition –> e.g. gastrocnemius has higher type II composition than soleus, therefore it will lose more power than soleus from its original ability
Enzymes indicative of metabolic changes in energy production pathways (3)?
- Hexokinase
- Lactic dehydrogenase
- Adenosine triphosphate (ADP)
There is a _____ in concentrations and activity of many enzymes with age
decrease
List some hormone changes with ageing? (5)
- Insulin levels increase
- Insulin sensitivity decline
- Growth hormone decline
- IGF-I decline
- Testosterone decline
Considering hormones can decrease with age, does supplementation of these hormones increase muscle mass?
Growth hormone with resistance training test still didn’t have effects –> therefore not clear
What are some methods of testing physical performance? (5)
- Gait speed
- Timed ‘get up and go’ test
- One leg balance
- stair climb power test
- Short physical performance battery
