sprint exercise Flashcards
What is intensity and duration?
Intensity= rate of power produced relative to capacity Duration= time an exercise is sustained
What are the four exercise domains?
Severe intensity, very heavy intensity, heavy intensity and moderate intensity
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
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
What is heavy intensity defined as?
Sustained increase in blood lactate that comes to a steady state.
Tolerable duration of 1-3 hours
What is moderate intensity defined as?
No sustained increase in arterial blood lactate.
Duration >3 hours
What are the characteristics of type I fibres?
High fatigue resistant with a small diameter and contract rapidly with little force
Respire aerobically
What are the characteristics of type II fibres?
Very large amd produce lots of force and power but are highly fatigable
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
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
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
What causes the number of which fibres an individual has?
Its a mixture between training and genetics
What fibres are recruited during a sprint?
Type I, type II and type IIa
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
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
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
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
