NSCA-CPT Exercise Physiology 5 — Questions and Answers
Question 1: What is the primary function of myoglobin in skeletal muscle?
- Generating ATP through oxidative phosphorylation
- Storing and facilitating oxygen transport within the muscle cell (Correct answer)
- Buffering intramuscular pH
- Activating actin-myosin cross-bridge cycling
Correct answer: Storing and facilitating oxygen transport within the muscle cell
Myoglobin stores oxygen within muscle fibers and facilitates its diffusion from capillaries to mitochondria during aerobic metabolism.
Question 2: During steady-state submaximal aerobic exercise, which substrate mix is MOST accurate at moderate intensity (~65% VO2max)?
- Nearly 100% fat oxidation
- Roughly equal contributions from carbohydrate and fat (Correct answer)
- Nearly 100% carbohydrate oxidation
- Equal contributions from carbohydrate, fat, and protein
Correct answer: Roughly equal contributions from carbohydrate and fat
At ~65% VO2max, both carbohydrate and fat contribute approximately equally to energy production, a mix that shifts toward carbohydrates at higher intensities.
Question 3: The sliding filament theory of muscle contraction states that muscle force is generated when:
- Actin and myosin filaments shorten individually
- Myosin cross-bridges pull actin filaments toward the center of the sarcomere (Correct answer)
- Titin protein contracts to shorten the sarcomere
- Troponin directly pulls actin filaments inward
Correct answer: Myosin cross-bridges pull actin filaments toward the center of the sarcomere
Myosin heads (cross-bridges) bind actin and pivot to pull actin toward the M-line, shortening the sarcomere and generating force without the filaments themselves changing length.
Question 4: Which change in blood chemistry during intense exercise MOST directly stimulates increased ventilation?
- Decreased blood oxygen partial pressure (PO2)
- Increased blood CO2 and decreased pH (Correct answer)
- Increased blood nitrogen levels
- Decreased hemoglobin concentration
Correct answer: Increased blood CO2 and decreased pH
Rising blood PCO2 and falling pH (increased H+ ions) are the primary stimuli detected by central and peripheral chemoreceptors to drive ventilation during intense exercise.
Question 5: Which term describes the heart's ability to stretch and fill with more blood, increasing stroke volume without an increase in end-diastolic pressure?
- Afterload
- Frank-Starling mechanism (Correct answer)
- Ejection fraction
- Peripheral resistance adaptation
Correct answer: Frank-Starling mechanism
The Frank-Starling mechanism states that greater ventricular filling (preload) increases myocardial stretch, resulting in a more forceful contraction and larger stroke volume.
Question 6: Which hormonal response to exercise promotes fat mobilization from adipose tissue?
- Insulin
- Glucagon only
- Catecholamines (epinephrine and norepinephrine) (Correct answer)
- Cortisol alone
Correct answer: Catecholamines (epinephrine and norepinephrine)
Catecholamines (especially epinephrine) stimulate hormone-sensitive lipase in adipose tissue, increasing free fatty acid release into circulation during exercise.
Question 7: In the context of training adaptations, 'central' cardiovascular adaptations refer to changes in:
- Peripheral muscle capillary density and mitochondrial density
- Heart size, stroke volume, and cardiac output (Correct answer)
- Blood lactate clearance by the liver
- Arteriovenous oxygen difference in active muscles
Correct answer: Heart size, stroke volume, and cardiac output
Central adaptations involve the heart itself — increased left ventricular volume, stroke volume, and maximal cardiac output resulting from endurance training.
NSCA-CPT Exercise Physiology 5
What is the primary function of myoglobin in skeletal muscle?