W6 - Ergogenic Aids - Nitrate Flashcards
Via what pathway is nitric oxide synthesised in the body?
L-arginine pathway
What does the L-arginine pathway require?
Arginine
O2
NADPH
What does the L-arginine pathway produce?
NADP
Citrulline
NO
What are the 3 forms of NOS?
NOS1 / nNos
NOS2 / iNOS
NOS3 / eNOS
When NO is produced in the CV system…
How does it enter the smooth muscle of the bv?
Diffuses from endothelial cell to the smooth muscle of the bv.
When NO is produced in the CV system…
What happens once NO has entered the smooth muscle of the bv?
Activates sGC
When NO is produced in the CV system…
What is the result of sGC being activated by the NO?
Incr cGMP
When NO is produced in the CV system…
What is the result of the activated sGC increases cGMP?
Activation of protein kinase (PKG)
- Results in decr Ca2+ via at least 4 mechanisms
When NO is produced in the CV system…
What are the 4 mechanisms by which ca2+ is decreased after PKG is activated?
Inhibition of voltage gated channels
Activation of plasma membrane calcium ATPase (PMCA)
Inhibition of IP3R
Activation of SERCA
When NO is produced in the CV system…
NO activates sGC.
= Incr cGMP
= Activates PKG
= Decr Ca2+ via 4 mechanisms
What do all these mechanisms result in?
Relaxation of vascular smooth muscle cells.
Process of digestion for dietary nitrate
Ingested
Absorbed into systemic circulation
Conc in saliva where oral bacteria can prod nitrite.
Nitrite is swallowed –> Stomach to be converted to NO + support host defence OR nitrite can be absorbed into systemic circulation again + who needed can be converted to NO.
Dietary nitrate supplementation and low intensity exercise
Red the O2 cost
Dietary nitrate supplementation and high intensity exercise
Enhances tolerance
Nitrate supplementation and time to exhaustion
Increased ~16%
- BUT not an ecologically valid measure of exercise performance.
Nitrate supplementation and rowing performance
NO sig improvement according to a meta-analysis
Beetroot juice ingestion and 10km TT performance
Incr power output
Nitrate supplementation and CWR bouts
O2 uptake is reduced
Nitrate supplementation and intermittent type exercise
Might have beneficial perf effects
When is the L-arginine -NO pathway blunted?
During hypoxia
Why would improved reaction time in the 2nd half of an intermittent sports game be beneficial?
Allows 1 to react quickly to changing stimuli
Nitrate supplementation and marathon
There are benefits
NO metabolism and menstrual cycle
It is known to be differences in its metabolism throughout the menstrual cycle
What is the minimal effective acute dose that may be required to gain an advantage from nitrate in a mixed population?
5mmol
VO2 during 75W clamped protocol and nitrate supplementation
Sig altered
When is the change after supplementing dietary nitrates more pronounced, when you start with a higher or lower aerobic fitness?
Lower
Why might elite endurance athletes have a reduced effect from nitrate?
Higher NOS activity
Higher baseline plasma [nitrite]
Better muscle oxygenation therefore L-arginine NO pathways always active due to amounts of O2 present.
Higher mit vol + efficiency
Nitrate dose + duration of supplementation may not be optimised for them
Higher proportion of type 1 fibres which may not be as responsive to nitrate supplementation
What seems to be a deciding factor of the lack of ergogenic effect from nitrate supplementation in athletes?
Aerobic capacity
Which type of athletes seem to experience ergogenic effects from nitrate supplementation?
Power + sprint
What is the most ecologically valid performance measure of endurance performance in sport?
TT
65+ ml/kg/min does not have a significant overall effect for nitrate supplementation + performance.
True or false
True
With regards to nitrate supplementation…
As aerobic capacity increases, what happens to TT performance improvements?
Decrease
What is meant by mitochondrial oxidative phosphorylation efficiency?
Amount of O2 consumed per ATP prod
Which type of muscle fibre seems to be affected the most by nitrate supplementation?
Type 2
What is believed to increase with nitrate supplementation?
Ca2+ sensitivity
SR Ca2+ pumping
What was the surname of the first author to show nitrate lowers VO2 during submaximal exercise?
Larsen
What effect does nitrate supplementation have on high intensity time to exhaustion?
Increases time to exhaustion
When considering the meta-analysis, which of the following does not have a significant improvement in performance with nitrate supplementation?
Running
Cycling
Handgrip
Rowing
Rowing
Which nitric oxide metabolism pathways is blunted during hypoxia?
Nitrate-nitrite-nitric oxide pathway
In the meta-analysis, which aerobic capacity does not have a significant overall effect for nitrate supplementation and performance?
65+ ml/kg/min
Which of the following do we believe increases with nitrate supplementation?
Calcium sensitivity
Calcium concentration
Sarcoplasmic reticulum calcium release
Sarcoplasmic reticulum calcium pumping
Calcium sensitivity
Sarcoplasmic reticulum calcium pumping
What enzymes is vital for the L-arginine pathway?
Nitric oxide synthase
What can oral bacteria do to NO3- from the diet?
Convert it to NO2-
What happens to the nO2-
To the stomach,
Some enters systemic circulation
Some converted to NO.
What happens to O2 uptake after nitrate supplementation for CWR bouts?
Decreases
