Spearfishing Freediving Physiology for Spearfishing 1 — Questions and Answers
Question 1: What physiological reflex helps divers conserve oxygen during a breath-hold dive?
- Adrenaline rush
- The mammalian dive reflex, which slows heart rate and redirects blood to vital organs (Correct answer)
- Increased respiratory rate
- Muscle relaxation response
Correct answer: The mammalian dive reflex, which slows heart rate and redirects blood to vital organs
The mammalian dive reflex triggers bradycardia (slowed heart rate) and peripheral vasoconstriction when the face contacts cold water, reducing oxygen consumption.
Question 2: What happens to air volume in a diver's lungs as they descend to greater depth?
- Air volume increases proportionally
- Air volume compresses according to Boyle's Law, decreasing as pressure increases with depth (Correct answer)
- Air volume stays constant
- Air converts to liquid at depth
Correct answer: Air volume compresses according to Boyle's Law, decreasing as pressure increases with depth
Boyle's Law states that gas volume decreases inversely with increasing pressure; at 33 feet (2 ATM), lung volume is halved compared to the surface.
Question 3: What is 'lung squeeze' and at what depths does it typically become a risk for spearfishers?
- A feeling of fullness after eating before diving
- Pulmonary barotrauma from exceeding the lung's minimum compression volume, typically at depths greater than 100 feet for most divers (Correct answer)
- Mild chest compression felt at any depth
- Air trapping in the sinuses
Correct answer: Pulmonary barotrauma from exceeding the lung's minimum compression volume, typically at depths greater than 100 feet for most divers
Lung squeeze occurs when depth compresses lung volume below residual volume, causing injury to lung tissue; it is a serious risk for divers attempting extreme depths.
Question 4: Why do experienced spearfishers pack-breathe (inhale in stages) before a dive?
- To hyperventilate and extend dive time
- To maximally load the lungs beyond tidal volume, increasing oxygen stores for the dive (Correct answer)
- To equalize ear pressure at the surface
- To reduce anxiety before descending
Correct answer: To maximally load the lungs beyond tidal volume, increasing oxygen stores for the dive
Pack breathing staggers inhalation to exceed normal tidal volume, maximizing lung oxygen stores; it differs from hyperventilation as it does not flush CO2.
Question 5: What is the 'urge to breathe' physiologically driven by during a freedive?
- Dropping oxygen levels in the blood
- Rising CO2 (carbon dioxide) concentration stimulating chemoreceptors in the brain (Correct answer)
- Nitrogen buildup
- Lactic acid accumulation
Correct answer: Rising CO2 (carbon dioxide) concentration stimulating chemoreceptors in the brain
The primary drive to breathe is triggered by CO2 accumulation activating chemoreceptors in the medulla and carotid bodies, not by falling O2 levels.
Question 6: How does equalization failure during a descent affect a spearfisher's dive?
- It has no practical effect
- Inability to equalize middle ear pressure causes pain and can rupture the eardrum, forcing an aborted dive (Correct answer)
- It increases bottom time
- It only affects hearing temporarily
Correct answer: Inability to equalize middle ear pressure causes pain and can rupture the eardrum, forcing an aborted dive
Pressure imbalance between the middle ear and the surrounding water causes barotrauma (ear squeeze), with potential eardrum rupture if the diver continues descending without equalizing.
Spearfishing Freediving Physiology for Spearfishing 1
What physiological reflex helps divers conserve oxygen during a breath-hold dive?