Chronic Adaptations to Reduced Use - The Effects of Detraining, Immobilisation & Ageing

Question 1

What is detraining?

Answer 1

Planned or unplanned reduced volume or intensity of training

When strength and power performance decrements occur or when muscle mass is lost, some type of detraining may have occurred

Question 2

How long does detraining last?

Answer 2

It can take place over weeks (can be a result of resistance training program design) or many years (e.g. no exercise training combined with ageing)

Understanding detraining can help coaches to reduce the likelihood of causing detraining

Question 3

How can detraining occur?

Answer 3

Total cessation of all types of training (e.g. at the end of a season) however this is not advised

A reduction in weight training, this could be because of an injury

Planned reduction in weight training, usually with continuation of other types of physical training

Question 4

Cessation of Resistance Training

Answer 4

This may occur at the end of a season or at the termination of an athletic career

Seldom desirable

Studies indicate that strength gains decline at a slower rate that the rate at which strength increased

The direction and magnitude of strength changes during a short detraining period may vary depend on the initial level of conditioning

The rate of strength loss depends on: length of the training & detraining period, strength test used, muscle group examined, subjects involved.

Older subjects in particular lose strength rapidly after 12 weeks of detraining

Question 5

In-season Detraining

Answer 5

Loss of performance when an individual reduces or cuts out resistance training whilst undertaking other sports specific training

Athletes in sports with a high strength component can tolerate periods of no in-season resistance training with little or no decreasein strength or performance

Question 6

Long-term Detraining Periods

Answer 6

Staronet al. (1981)

▪Elite power lifter followed for seven months of detraining and dieting

▪Detraining resulted in a physiological shift from a strength profile to an aerobic profile

▪Improvement of peak oxygen consumption, increased mitochondrial density & improved oxidative enzyme profile

▪Reported a reduction in muscle fiber which contributed to a decrease in thigh

Hakkinen& Komi (1985)

▪24 weeks of heavy resistance training = 13% increase in vertical jump ability

▪12 weeks of detraining = a decrease in jump ability (still 2% above the pre-training value)

▪Short term detraining periods do not significantly affect vertical jump ability but longer periods can show a reduction

▪It is thought that in-season training programs may be enough to maintain performance

Winter & Snow (2000)

▪Bone mineral density decreased after 6 months of detraining

▪The type of resistance training, the inherent normal activity and the limbs involved influence the responses of bones to periods of detraining

Question 7

Watch Lecture Recording

Answer 7

13: 57 - 29:47
36: 40 - 49:11

Question 8

Number of people aged 60+ worldwide

Answer 8

2015 = 900million (16% of the population)

2050 = 2billion = (22% of the population)

Question 9

Falling

Answer 9

1 in 3 older adults (65+) will fall every year & risk increases with age

Significant mortality risk & injury risk, alongside psychological & social impact

Estimated NHS costs >£2.3 billion/year

Question 10

Ageing Effects: Muscle Strength

Answer 10

Muscle strength is a critical component in maintaining physical function, mobility and vitality in old age

Strength peaks between 20 and 30 years, then slowly declines until around 50 years of age

After 50, losses of ~12% to 15% per decade have been reported

After 65, more rapid losses~30% per decadehave been shown

Question 11

Mechanisms involved in the decline in muscles with age

Answer 11

Muscle atrophy

Reduced neural drive

Slower shortening velocity

Question 12

Muscle Properties during ageing

Answer 12

Increase in type l muscle fibres = slower contractile properties

Reduction in the rate of AP discharge

Reduction in tendon stiffness = impact on balance ability

Question 13

Neural Pathways during ageing

Answer 13

Decreased functional capabilities of CNS caused by:

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

Question 14

Motor Unit Properties during ageing

Answer 14

Reduction in the number of motor neurons

Higher innervation number –redundant fibresare re-innervated

Reduced capacity for rate coding (discharge rates are less)