Exercise intensity assessment and interpretation Flashcards
Exercise intensity: definition?
- 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
Ensuring a comparable exercise intensity is important, why?
• 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
Why account for exercise intensity?
- Metabolic, gas exchange, and perceptual responses vary greatly at different intensities
- Intra and inter individual variability obscures real differences
what underpins the variance in response?
- Submaximal thresholds
- Lactate or gas exchange threshold
- Maximum lactate steady state
Prescribing exercise intensity as a percentage of VO2max is widely used, why?
• 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
Same % VO2max, Same Intensity?
• 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
Exercise intensity Domains?
- 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
Exercise intensity domains: domain threshold?
- Moderate – below the LT
- Heavy – above LT, below MSS
- Severe – above MSS achieving VO2max
- Extreme – exhaustion before VO2max
Vo2 slow component?
• 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
Most likely explanation of the slow component?
- Additional motor unit recruitment:
* The original hypothesis was that additional fibres were recruited to replace fatiguing fibres
How to calculate cycling economy or Gain?
Change in Vo2/change in work load
Moderate intensity exercise:
• 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
Heavy intensity exercise?
- 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
Heavy Intensity Exercise and Sport?
- 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
Severe intensity exercise?
• 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