Exercise intensity assessment and interpretation Flashcards

1
Q

Exercise intensity: definition?

A
  • Refers to the physiological response to a given external work rate
  • External work rate itself is not the intensity of exercise

• Normalising exercise intensity is the attempt to ensure all
participants experience an equivalent physiological demand

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2
Q

Ensuring a comparable exercise intensity is important, why?

A

• Ensuring a comparable exercise intensity is important:

• For studies designed to measure the physiological or psychosocial
impact of an intervention or stimuli

• For the design of effective training or rehabilitation programmes

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3
Q

Why account for exercise intensity?

A
  • Metabolic, gas exchange, and perceptual responses vary greatly at different intensities
  • Intra and inter individual variability obscures real differences
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4
Q

what underpins the variance in response?

A
  • Submaximal thresholds
  • Lactate or gas exchange threshold
  • Maximum lactate steady state
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5
Q

Prescribing exercise intensity as a percentage of VO2max is widely used, why?

A

• Better than using just external work rate

• Relies on a valid VO2max and fails to account for the
variation in the occurrence of submaximal thresholds:

• Lactate threshold varies widely between people, can
occur between 30 – 85% VO2max

• Physiological and perceptual responses very different
above and below the GET and MSS

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6
Q

Same % VO2max, Same Intensity?

A

• Main difference is one participant’s VO2 reaches a
steady state, whilst the other’s keeps rising

• Indicative of exercise being much more difficult for the second participant

• In a test to exhaustion at this ‘same’ intensity, 1
participant would last >4hrs, the other would last
~10-20 minutes

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7
Q

Exercise intensity Domains?

A
  • It is accepted that there are 4 exercise intensity domains (Burnley and Jones, 2007):
  • Moderate, Heavy, Severe, Extreme
  • Knowledge of these domains is critical for understanding differences in the physiological response to exercise
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8
Q

Exercise intensity domains: domain threshold?

A
  • Moderate – below the LT
  • Heavy – above LT, below MSS
  • Severe – above MSS achieving VO2max
  • Extreme – exhaustion before VO2max
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9
Q

Vo2 slow component?

A

• A slowly developing component of VO2
that becomes evident
after 2-3 mins

  • Only seen above the LT (i.e. never during moderate intensity exercise)
  • Eventually levels off during heavy intensity exercise
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10
Q

Most likely explanation of the slow component?

A
  • Additional motor unit recruitment:

* The original hypothesis was that additional fibres were recruited to replace fatiguing fibres

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11
Q

How to calculate cycling economy or Gain?

A

Change in Vo2/change in work load

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12
Q

Moderate intensity exercise:

A

• All exercise below the LT with no elevation in blood lactate

• VO2
increases at ~10 ml·min-1
·W-1

  • All team sports involve periods of moderate intensity exercise
  • Rare in other top class sports
  • Recreational runners will commonly exercise in the moderate domain
  • Moderate exercise can be continued for ~4hrs
  • Fatigue is likely related to muscle glycogen depletion, muscle damage, and/or increased core temperature
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13
Q

Heavy intensity exercise?

A
  • All work rates that are above the LT below the MSS where a steady state in VO2 will eventually be attained
  • Differs significantly from moderate
  • Closer heavy exercise is to the LT = smaller the VO2 SC

• Crucially – even if exercise is completed to exhaustion, VO2
remains sub-maximal – i.e. a steady state will be attained

• VO2
‘gain’ may reach ~12 ml·min-1
·W-1 due to the VO2 SC

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14
Q

Heavy Intensity Exercise and Sport?

A
  • HR – delayed, elevated steady state attained
  • Bla – elevated above baseline but a steady state will be attained
  • Many endurance events (including the marathon) are performed predominantly within the heavy domain
  • Constant work rate activities lasting ~30 - 120mins
  • Fatigue is complicated
  • Combination of metabolite accumulation and substrate availability
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15
Q

Severe intensity exercise?

A

• All work-rates that are above the maximum steady state where
VO2 max is attained if exercise is continued to exhaustion

• It is the VO2 SC that causes VO2
to reach its maximum

• A steady state will never be reached during severe exercise

• HR – No steady state will be achieved; HR will continue to rise
until HR max is achieved

• BLa – no steady state; will continue to rise until exhaustion

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16
Q

Severe Intensity Exercise? Exercise in the severe domain is unique for 2 reasons:

A
  1. It encompasses a wide range of work rates which
    results in the attainments of VO2max
  2. Exercise tolerance is significantly limited, but also predictable

• Finite amount of work can be done above MSS,
thus exhaustion can be estimated with remarkable accuracy

17
Q

Severe intensity exercise and sport?

A

• 1,500 – 10,000m track events are conducted largely in the severe
domain

  • Durations of 2 - ~30 minutes
  • Getting pacing wrong can have dire consequences

• There is no recovery if work rate is reduced but stays in the
severe domain

• Fatigue is related to PCr depletion and accumulation of fatiguing
metabolites (Pi, H+).

18
Q

Extreme intensity exercise?

A
  • Work rates that are so high that fatigue ensues before VO2 max has been attained
  • The highest defined exercise intensity domain
  • Time to exhaustion usually <90s
  • Fatigue mechanisms similar to severe (PCr depletion and accumulation of fatiguing metabolites)
  • Relatively little work has been done in this area
  • HR – No steady state will be achieved; exercise will cease before HR max is attained
  • BLa – No steady state; value may be surprisingly low due to short duration of exercise