Lecture 15 - The Effect of Detraining, Immobilisation & Ageing

Question 1

What is immobilasion and what impact can this have upon muscle mass?

Answer 1

• The fixing of a joing and surrounding musculature resulting in muscle wastage (atrophy)
• Can be as much as 50% loss within a few weeks.

Question 2

How do muscle unit properties change with age?

Answer 2

• Progressive reduction in the number of motor neurons - 47%
• Higher innervation number – redundant fibres are re-innervated
• Reduced capacity for rate coding (discharge rates are less)

Question 3

What are the causes for increased level of atrophy?

Answer 3

• Reduction in rate of protein synthesis

- Loss of muscle fibres.

Question 4

How does detrain affect jump capacity?

Answer 4

• Decreased by 12 % but is still 2% above pre-training value.

Question 5

What factors can determine the rate of strength loss?

Answer 5

• Length of the training and detraining period
• Strength test used
• Muscle group examined
• Subjects involved
• Initial level of conditioning

Question 6

How do muscle properties change with age ?

Answer 6

• Proportion of type l muscle fibres increases
• Greater number of type l fibres results in slower contractile properties
• Reduction in the rate of AP discharge – rate of torque development much lower
• Reduction in tendon stiffness – impact on balance ability

Question 7

How does the function of gait change in older adults ?

Answer 7

• Step length decreases along with forward velocity de to an inability to produce the same level of propulsion caused by strength loss and sarcopenia, tightening of hip flexors, tendon changes and reduced balance control.

Question 8

What are the strength losses in men per decade after 50 and after 65?

Answer 8

• 30-50 reduction of 1-2% year
• 50-65% reduction of 12-15% per decade
• 65+ losses of 30% per decade reported

Question 9

What is in-season detraining?

Answer 9

• In season detraining is the loss of performance when an individual reduces or cuts out resistance training whilst undertaking other sports specific training.
• Athlete who perform power sports, such as sprinting can handle a period on detraining without any losses in performance.

Question 10

How can sarcopenia be prevented?

Answer 10

• Physical activity
• Resistance training
• Nutrition – ↑ protein synthesis
• Supplements

Question 11

What are some issues with chronic detraining ?

Answer 11

• Development of excess fat mass and associated CVD problems such as diabetes.

Question 12

What has been found about long term detrain effects on power lifters ?

Answer 12

• With detraining these lifters gain more of an aerobic profile via physiologic shift.

Question 13

What are the ageing effects on muscle mass?

Answer 13

• With ageing, related losses in muscle increase (sarcopenia). These muscle fibres that shrink are replaced with fat or fibrous connective tissue which compromises force and metabolic functions.

Question 14

What impact can detrain have on bone density?

Answer 14

• Decreases after six months.

Question 15

What are the effects of leg unloading on muscles?

Answer 15

• Reduction in strength that is greater than atrophy – caused by impairment of activation
• Reduction in type l fibres
• Decrease in peak force of fibres due to reduction in specific tension which was greater than that observed for limb suspension.

Question 16

What is detraining, how long does it last and how can it occur?

Answer 16

• Cessation of exercise training
• Can last weeks to years.
• Can occur though not training at all, reduction in weight training.

Question 17

What effect does immobilisation have on muscle fibres and the explication of this?

Answer 17

• Decline in proportion of type 1 and increase in type 2 fibres.
• Muscle fibres effected most by immobilisation are those who’s activity is reduced the most.

Question 18

How does strength adaptation change in older adults?

Answer 18

• Strength can increase significantly with only small muscle mass moment, this indicates improvement in neural adaptation.

Question 19

How do neural pathways change with age?

Answer 19

• Change in modulation of reflex pathways
• Slower reactions and greater cerebral cortex activity during simple tasks
• Increased co-activation of antagonist muscles

Question 20

What are the effects of hind limb suspension on muscles?

Answer 20

• Decline in proportion of type l fibres
• Increase in proportion of type ll fibres
• Reduction in maximal force & specific tension
• Type l fibres show a reduction in diameter
• Increase in contractile speed – expected due to
  changes in fibre type

Question 21

What are the effects of spaceflight on muscles?

Answer 21

• Atrophy greatest for type llx muscles and least for type l fibres
• Decrease in the number of fibres in antigravity muscles
• Declines in muscle strength after 17 days in space – strength reductions greatest in thigh muscles than arm muscles
• Increase in fatigability

Question 22

What is something you may notice in older population when standing ?

Answer 22

• Noticeable swaying or shifted posture due to loss of muscle control.