Exercise Physiology & Energy Metabolism Flashcards
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Read the first 7 Exercise Physiology & Energy Metabolism flashcards as text
During high-intensity interval training (HIIT), which metabolic byproduct accumulates and contributes to peripheral fatigue?
Answer: Lactate and hydrogen ions
Lactate accumulation alongside hydrogen ions (not lactate itself) lowers intracellular pH, impairing muscle contractile function during high-intensity exercise.
The crossover concept in exercise physiology describes the point at which:
Answer: Fat oxidation decreases and carbohydrate oxidation becomes the dominant fuel source
The crossover concept (Brooks & Mercier) describes the exercise intensity at which carbohydrate oxidation exceeds fat oxidation as the predominant fuel source.
Which enzyme is rate-limiting for beta-oxidation of fatty acids in skeletal muscle?
Answer: Carnitine palmitoyltransferase I (CPT-I)
CPT-I controls fatty acid transport into the mitochondrial matrix and is the rate-limiting step for beta-oxidation; it is inhibited by malonyl-CoA at high carbohydrate flux.
An athlete exercising at 65% VO2max for 90 minutes is MOST likely experiencing:
Answer: Progressive reliance on plasma free fatty acids as muscle glycogen declines
As muscle glycogen declines during prolonged moderate-intensity exercise, plasma free fatty acid uptake and oxidation progressively increase to spare remaining glycogen.
What is the primary role of AMP-activated protein kinase (AMPK) during exercise?
Answer: Sense energy depletion and stimulate glucose uptake and fat oxidation
AMPK is activated when the AMP:ATP ratio rises, signaling low energy status and triggering pathways that increase glucose uptake (GLUT-4 translocation) and fatty acid oxidation.
During the transition from rest to moderate exercise, oxygen consumption rises in a curvilinear fashion before reaching steady state. This period is called:
Answer: Oxygen deficit
The oxygen deficit is the gap between the oxygen required and the oxygen actually consumed at the onset of exercise before steady-state is achieved.
Which substrate contributes MOST to ATP production during a 10-km road race run at approximately 80% VO2max?
Answer: Muscle glycogen
At ~80% VO2max, muscle glycogen is the predominant substrate because the rate of fat oxidation cannot keep pace with the high ATP demand of this intensity.