Quis 11 lab

Does resting HR affect MAX lactate values (mol/L)?

Hypo: a lower resting HR is predictive of a lower max lactate value (a higher resting HR, a higher max lactate value) Just: Resting HR is an index fitness so high resting HR= decreased fitness -> unfit subject would be untrained and have smaller heart (smaller left vent.) and lower SV-> less blood and O2 being delivered less quickly to mitochondria inside muscles so ATP will not be produced as fast due to lack of O2 -> anerobic (fast) glycolysis will have to begin sooner and pyruvate will be convered to lactate faster since demand of ATP of contracting muscles exceeds mitochondrial ATP production -> fast twitch muscles employed which accounts for accumulation of lactate quickly Results: max lactate value (mmol/L)/ Resting HR Interp: Accept

Do lactate values and ventilatory values indicate the same threshold (watts)? Should they? Why or why not? Think about RER?

Hypo: lactate values and ventilatory values indicate the same threshold Just: lactate threshold and ventilatory occur together -> when lactate levels spike, ventilation also spikes to try and remove some of the lactic acid through expelling CO2 out of the body-> when you make a lot of lactic acid, you make a lot of CO2 and rapid ventilation begins (this is what raises RER above 1.1 to indicate that subject is performing anaerobic respiration)-> Lactate threshold and ventilatory threshold occur at the same power. Result; Ventilatory threshold (watts) Interp: accept

Why is lactic acid produced?

Lactic acid is produced as a byproduct of aerobic (fast) glycolysis when O2 deliveries are insufficient to produce ATP aerobically via oxidative phosphorylation of carbs and fats. It is produced when mitochondrial ATP is less than the demand of ATP needed for contracting muscles. Lactic acid is not yet released, its proton (H+) which would make it lactate (anion found in the blood stream). It causes a decreases in pH of the blood causing acidosis. The production of lactic acid recycles NADH to NAD+ to allow glycolysis to continue in the absense of O2.

For exercising at normal altitudes, when and why is lactic acid produced? Make sure to give a complete and specific answer. When does it occur? Consider both the limits of mitochondria AND muscle fiber types. Why is it inappropriate to say that anaerobic metabolism occurs due to lack of oxygen for exercising at normal altitudes?

Lactic acid production occurs when the demand for ATP of contracting muscles exceeds (is greater than mitocondrial ATP production). When lactate spikes, the body is employing mainly fast (glycolytic) twitch muscles that can only provide energy and contraction for a short period of time as opposed to slow twitch muscle fibers that are primarly used during aerobic metabolism with the presence of oxygen. Slow twitch can continue contracting for a long duration. Fast twitch muscle fibers contribute to lactate accumulation that is released into the bloodstream. O2 is still available, it is just that the amount of O2 delivered to muscles and mitochondria is no longer sufficient to perform oxidative phosphorylation via aerobic metabolism to produce ATP. Muscles need more ATP than the mitochondria can give and so fast glycolysis has to step in to supplement the ATP production.