sprint exercise Flashcards by Ellen Butler

What is intensity and duration?

Intensity= rate of power produced relative to capacity 
Duration= time an exercise is sustained

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What are the four exercise domains?

Severe intensity, very heavy intensity, heavy intensity and moderate intensity

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What is severe intensity defined as?

Rapid muscular fatigue. Tolerable duration of <2mins.
Occurs at the upper limit of VO2max
Exercise becomes limited because of the hyperbolic relationship

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What is very heavy intensity defined as?

progressive increase in lactate throughout.

Tolerable duration is bounded by the power duration curve and is 2-60 mins

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What is heavy intensity defined as?

Sustained increase in blood lactate that comes to a steady state.
Tolerable duration of 1-3 hours

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What is moderate intensity defined as?

No sustained increase in arterial blood lactate.

Duration >3 hours

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What are the characteristics of type I fibres?

High fatigue resistant with a small diameter and contract rapidly with little force
Respire aerobically

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What are the characteristics of type II fibres?

Very large amd produce lots of force and power but are highly fatigable

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What are the characteristics of type IIa fibres?

properties that are between type 1 and 2. The fibres range on a continuum across a range of metabolic and physical properties

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What is the order of fibre recruitment?

During most forms of activity there appears to be an orderly hierarchy of motor unit recruitment from type I to type IIa to type IIx

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Is the relationship between fibre type and metabolic properties fixed?

No . For example, type IIa fibres from an endurance-trained athlete may be have a higher expression of oxidative enzymes than type I fibres from an sedentary individual

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What causes the number of which fibres an individual has?

Its a mixture between training and genetics

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What fibres are recruited during a sprint?

Type I, type II and type IIa

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What is the skeletal storage of ATP?

Skeletal muscle [ATP] storage is low:
5-8 mmol.kg-1 wet weight
Enough for ~8 maximal contractions or ~2 s

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During a sprint where is ATP largely supplied from?

During sprint exercise ATP supply is largely from anaerobic sources:
Stored ATP
Phosphocreatine (PCr) breakdown
Glycolysis

However, the integration (“cross talk”) between the energy providing pathways means that even during sprint exercise some energy derives from pyruvate entry to the mitochondrion to fuel oxidative phosphorylation

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What is the pattern of power output achieved over time?

Peak power is achieved after a few seconds it then declines.
At 10s ATP conc is halved in type IIx fibres this leads to a decline in power output. In the next few seconds ATP conc stays the seen in type IIx. There is a decrease in type I and IIa ATP at this time and so there is a further reduction in power

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What is the max flux capacity mmol ATP.kg-1.s-1) of ATP, PCr, glycolysis,CHO and FFA

ATP= -
PCr= 2.3 
glycolysis= 1.1 
CHO= 0.6 
FFA= 0.3

What is the max capacity mmol ATP.kg-1 of ATP, PCr, glycolysis,CHO and FFA

ATP= 8.2
PCr= 32
glycolysis= 75
CHO= 7500
FFA= -

What are the different stores and at what rate do they supply energy?

Oxidation of fatty acids= biggest store but slowest supply

Oxidation of carbs= second biggest store with a moderate supply speed

Glycolysis - smallest store and the biggest supply speed

That already stored as ATP and PC is the fastest store but is very very small

What is the overall reaction that occurs to breakdown PCr?

PCr + H+ Pi + Cr

What direction is the PCr reaction going in?

CK is near-equilibrium and has the fastest rate of all other enzymes in the muscle

The CK reaction favours PCr breakdown over ATP formation, therefore during sprint exercise (when ATP hydrolysis is rapid) the reaction flows rapidly left to right

What happens to PCr concentration during sprint exercise?

It declines during sprint and at 30s is almost depleted. This can result in an alkalosis which received inhibition of phosphofructokinase

What is the change in intracellular pH in the body during a sprint?

During the 15 second sprint there is a rapid alkalosis due to Pcr breakdown consuming protons and relieves inhibition of PFK.
During recovery as PCr is recovered which produced proteins and stimulates glycolysis and an acidosis which takes mins to recover back to baseline

What does the reaction of PCr breakdown mean? What does this mean about the power stroke?

PCr breakdown buffers ADP accumulation but does not attenuate Pi liberation
During the power stroke Pi is liberated and so a buildup of Pi stops this release and causes fatigue as it inhibits dissociation

What enzyme catalyses PCr breakdown?

Creatine kinase

What happens if you inhibit the enzyme that breaks down PCr?

Without creatine kinase to catalyse PCr breakdown and Pi production, they have lower absolute force production but better maintenance of force

What happens with high levels of ADP?

It causes muscle relaxation to become slow and so causing a reduction in muscle power output.

Where is there high expressions of Mechanical machinery CK?

cytosol

What is mitochondrial CK co-localised too?

The adenine nucleotide translocase

What does PCr mean about energy production?

Pcr is a temporal energy buffer providing rapid ATP provision during sprint exercise. It is also a spatial energy buffer - a signalling molecule to communicate with other cellular compartments the requirement for increased rates of ATP production

What is the Adenylate kinase (AK) reaction?

2ADP ↔ ATP + AMP

What is an important role of AMP?

AMP accumulation pays an important role in stimulating glycogen phosphorylase and PFK

What is the AMP deaminase (AD) reaction?

AMP + H2O + H+ → IMP + NH4+

When is AMP deaminase inhibited?

AMP deaminase is inhibited when [ATP] is high

What is the summary of the 30 second sprint?

- Oxidative phosphorylation activation is slow, therefore [ATP] homeostasis is challenged - Rapid PCr breakdown provides immediate ATP allow maintenance of peak power for first ~1-5 seconds - The consequent rapid accumulation of Pi, ADP and AMP maximally activates glycolysis after ~5 seconds - Pi accumulation is closely associated with muscle fatigue and power declines from 5-30 seconds

How is type II muscle adapted for anaerobic energy provision?

``` Greater PCr concentration Greater glycogen content Greater glycogen phosphorylase activity AMP deaminase activity a-glycerophosphate shuttle expression ```

When is AMP deaminase activity increased?

When pH is low This acts to better maintain [ATP] / [ADP] especially during severe exercise in type II fibres This also maximises energy release during ATP hydrolysis

What is the main energy provision during sprint exercise?

Energy provision during sprint exercise is predominantly anaerobic from PCr and glycolysis

What is the overall effect of creatine kinase?

The creatine kinase reaction provides a spatial and temporal cellular buffer for [ATP]

What does a high rate of PCR breakdown lead too?

High rate of PCr breakdown leads to an alkalosis, and increases Pi, ADP, AMP, and IMP – each helping to activate glycolysis via direct or indirect affects on GP, PFK and HK