Breath holding is common in swimming, therefore understanding the physiology of breath holding is essential for swimmers. Learn if breath holding is safe and the physiology of breath holding.
Swimming requires frequent periods of breath holding. This is an uncommon characteristic compared to other sports, where breathing is unrestricted. The requirement of a breath is obvious, oxygen is necessary to supply the muscles for aerobic exercise. However, the breath in swimming does impair biomechanics, even in the swimmers with the best breathing biomechanics. Breath holding also allows swimmers to utilize underwater dolphin kicking, arguably the fastest form of swimming. The swimming community frequently uses breath holding during practices to reduce the frequency of breathing and to practice breath holding for underwater dolphin kicking.
Apnea is no movement of the muscles of inhalation while the volume of the lungs remain unchanged. In swimming training, breath holding underwater is incorrectly referred to as hypoxic training. Nonetheless, breath holding underwater utilizes apnea and is the results in hypercapnea, the excessive accumulation of carbon dioxide in the bloodstream [read more about hypercapnea training and the great work by Dr. Woorons; Exhale-Hold Technique; Dr. Woorons research article].
The swimming community practices long breath holds during movement, attempting to maximize the skill of holding breath underwater (although no swimmer actually holds their breath more than ~20 seconds in a race at a time). This domatic practice has resulted in numerous deaths, described as shallow water blackouts.
Physiological Result of Breath Holding
During breath holding underwater, heart rate and stroke volume (the amount of blood ejected from the heart with each contraction) both decrease. Blood flow in the arteries decreases, as the arteries reduce in size. During this, the body attempts to prioritize which organs receive blood, prioritizing vital organs (the brain for example).
Specifically for swimmers, a study compared the effects of breath holding during four 25-m laps with 30 seconds rest. The comparison groups were:
(a) at normal frequency breathing without fins
(b) with complete breath holding underwater for the four 25-m segments without fins
(c) at normal frequency breathing with standard commercial fins
(d) with complete breath holding underwater for the four 25-m segments with fins
The differences found between the different conditions, found in this study, were:
Breath holding underwater swimming induced a decrease in oxygen saturation in the arteries both with and without fins. Maximal heart rate decreased in both breath holding conditions.
The present study shows that acute dynamic breath holding underwater swimming elicits a decrease in arterial oxygen saturation and heart rate, in regional- and national-level male swimmers.
Remember, this study only looked at single length performance, not an entire set or maximal breath hold distance, a common by possibly dangerous use of breath holding underwater. If you use breath holding underwater for your team, consider the following takeaways and create a safe method for breath holding underwater practices:
1. Shallow water blackouts are the result of reduced heart rate and reduced blood ejection from the heart, likely from extremely slow underwater breath holding techniques. If you are using breath hold training, do it while using short distances, intense speeds.
2. Lack of performance correlates with a decrease in oxygen, making breathing biomechanics a paramount skill for success in events longer than 50 meters, as discussed with Coach Bruce Gemmell.