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Breath Holding Underwater Guide: Metabolic Effects and Safety in Swimming

Apnea is no movement of the muscles of inhalation and the volume of the lungs initially remains 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[read more about hypercapnea training and the great work by Dr. Woorons; Exhale-Hold Technique; Dr. Woorons research article].

During breath holding underwater, cardiac output decreases because of concurrent reductions in stroke volume and heart rate Underwater breath holding(HR). Peripheral blood flow reduces because of arterial vasoconstriction, whereas blood flow in the carotid artery increases suggesting redistributed blood flow toward vital organs during breath holding underwater. Arterial oxygen desaturation occurs in parallel and plasma lactate concentration is increased from baseline after breath holding underwater, suggesting greater reliance on anaerobic metabolism during breath-holding. Unfortunately, the responses of other stress hormones: cortisol, dehydroepiandrosterone (DHEA), and testosterone have never been investigated.

Diving responses seem to be augmented by several factors, such as face immersion in cold water and hypoxia, resulting in arterial oxygen saturation, and greater lactatemia. Studies of the metabolic responses to breath holding underwater during dynamic exercise remain relatively scarce. It was found that the diving-induced bradycardia during moderate dynamic cycle exercise was powerful enough to override the exercise tachycardia for the period of breath holding underwater. However, more recent studies in elite synchronized swimmers  and trained breath-hold divers showed that with higher exercise intensity, HR was increased during dynamic breath holding underwater compared with dry static breath holding underwater, but a relative bradycardic response was still observed during the dynamic breath holding underwater.

With the emergence of underwater kicking, breath holding underwater training is extremely common. Unfortunately, the risk of shallow water blackouts is a concern, as many elite swimmers report an experience of loss of consciousness, memory, and sadly death. I have vividly talked with elite swimmers about their experiences of shallow water blackouts, being lucky enough to surface safely by themselves or with the help of a teammate. Therefore, understanding the effects of breath holding is essential for performance enhancement and more importantly swimming safety.

Physiological Response of Breath Holding Underwater

Fifteen young trained regional- to national-level competitive male swimmers, 5–12 years of swimming, 3–7 times per week (Age, 21.9 ± 0.9 Underwater Breath Holdingyears; Height, 180.1 ± 2.0 cm; Weight, 69.5 ± 1.7 kg) volunteered to participate. The swimmers began with a 15-minute standardized warm-up followed by 15 minutes of passive recovery and then swam a total of four 100-m freestyle trials at maximal speed in randomized order, separated by 30-minute recoveries. Each 100-m freestyle trial consisted of four 25-m segments with departure every 30 seconds. The conditions were as follows:

(a) at normal frequency breathing without fins (S)

(b) with complete breath holding underwater for the four 25-m segments without fins (SAp)

(c) at normal frequency breathing with standard commercial fins (F)

(d) with complete breath holding underwater for the four 25-m segments with fins (FAp)

Swimming performance was assessed by the 100-m freestyle time. For the metabolic parameters, HR was continuously measured during the 4 trials with waterproof HR monitors. Arterial saturation was measured with a Nonin Onyx 9590 Finger Pulse Oximeter at rest and 30 seconds after the end of the last 25 m of each trial. For lactatemia measurement and cortisol, DHEA, and testosterone analyses, 10 μl of capillary blood from the fingertip and 1.5 ml of saliva were also drawn at rest and, respectively, 3 and 10 minutes after the end of the last 25 m of each trial. The unstimulated saliva was collected by the subjects themselves using Salitubes.

Swimming time was lower with fins than without fins, with or without breath holding underwater, with an increase in velocity (V) of about 0.2 m·s−1: VS, 1.59 ± 0.11; VSAp, 1.54 ± 0.12 m·s−1 compared with VF, 1.80 ± 0.10; VFAp, 1.77 ± 0.08 m·s−1. breath holding underwater swimming induced an alteration in performance without fins, but not with fins. Basal SpO2 did not differ between trials (98.2–98.5%). breath holding underwater swimming induced a decrease in SpO2 both with and without fins.

Maximal HR decreased in SAp compared with S and F. However, there was no difference in maximal HR between the SAp and FAp conditions. End exercise blood lactate was not different between trials. Cortisol and testosterone values were quite similar across trials and showed no increase compared with basal values. However, end exercise DHEA values were higher than rest values for all trials.

The present study shows that acute dynamic breath holding underwater swimming elicits a decrease in arterial oxygen saturation, HR, and swimming performance in regional- and national-level male swimmers. However, the decrease in HR and swimming performance induced by breath holding underwater disappears with fin use.

It is interesting to note that the alteration in swimming performance with apnea was positively correlated with exercise bradycardia and negatively with the arterial oxygen desaturation without fins. It therefore seems that performance is directly linked to the subject’s capacity to supply oxygen to exercising muscles.

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:

Main takeaways:

  1. Shallow water blackouts are the result of bradycardia and reduced cardiac output, likely from extremely slow underwater breath holding techniques. If you are using breath hold training, do it while using short, intense distances.
  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.


  1. Guimard A, Prieur F, Zorgati H, Morin D, Lasne F, Collomp K. Acute apnea swimming: metabolic responses and performance. J Strength Cond Res. 2014 Apr;28(4):958-63.

By Dr. G. John Mullen received his Doctorate in Physical Therapy from the University of Southern California and a Bachelor of Science of Health from Purdue University where he swam collegiately. He is the owner of COR, Strength Coach Consultant, Creator of the Swimmer’s Shoulder System, and chief editor of the Swimming Science Research Review.

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