Hypoxic Training: A Risk Analysis

January 15, 2014

Shawn P. DeRosa, J.D.
Manager of Aquatic Facilities & Safety Officer for Intercollegiate Athletics
The Pennsylvania State University

Shallow water blackout (“SWB”), also referred to as hypoxic blackout, is a term describing loss of consciousness arising from oxygen deprivation brought about by voluntary or involuntary hyperventilation.

In swimming, voluntary hyperventilation occurs when a swimmer intentionally “overbreathes,” blowing off carbon dioxide.  Involuntary hyperventilation can occur as a result of stress and physical exertion during a workout that pushes the swimmer beyond his/her maximum aerobic capacity (VO2 max).

This “silent killer” of otherwise healthy, accomplished swimmers should give pause to every coach and aquatic director around the world. Do we need to rethink how we run our practices or manage our facilities?

The dangers of breath holding are well known and well documented. The U.S. Naval Center website contains multiple examples of competent swimmers who lost their lives to shallow water blackout. Media outlets continue to highlight drownings of swimmers found unconscious, underwater following breath holding activities. In February 2013, swimmer Alex Bousky of the Peoria Notre Dame Varsity swim team suffered a non-fatal drowning. Bousky’s team is reported to have been working on how far they could swim underwater.

Industry groups including USA Swimming, the American Red Cross, the National Swimming Pool Foundation and the U.S. Navy have long cautioned against underwater breath holding activities, particularly those involving hyperventilation. Other groups, such as the YMCA of the USA and the Department of Morale, Welfare and Recreation of the U.S. Navy outright ban such extremely dangerous activities. Why? Because SWB has been proven to kill otherwise healthy swimmers.

While USA Swimming has not mandated a ban on restricted breathing training on the surface of the water, the national governing body for swimming admits that there is “no evidence that swimming without oxygen necessarily trains the anaerobic system.” USA Swimming states that there is a difference “between having swimmers hold their breath while swimming under water versus an extended breathing pattern while swimming on the surface.” The latter, is thought to improve oxygen management capacity. The former has proven to be deadly.

While USA Swimming and the American Red Cross continue to educate coaches regarding the difference between extending the breathing pattern on the surface and breath holding drills beneath the surface, some coaches continue to place athletes at risk of injury or death by doing “over/unders” or “lungbuster repeats.”

Even more dangerous is when a coach puts pressure on the athlete to swim extended distances underwater, such as by requiring an entire team to repeat an underwater drill if any one athlete surfaces to breathe. This creates a concern for athlete welfare as well as a potential area of liability, both for the coach and the employer.

Aquatic programs are advised to follow a risk management approach to addressing safety and liability concerns presented by hypoxic blackout. This entails evaluating the nature of the risk before selecting a risk aversion or risk management strategy. This also requires distinguishing between underwater drills and those conducted on the surface of the water. As both drills can lead to SWB, an evaluation must be made as to the likelihood or frequency of SWB resulting from such drills as well as the possible severity of such occurrence.

The frequency of an event can be described as frequent, probable, occasional, seldom (remote) or improbable.

The severity of an occurrence is often classified into the following levels:
– Catastrophic: may result in death;
– Severe: may cause severe injury or financial loss;
– Moderate: may cause property damage or minor injury resulting in hospitalization;
– Minor: may cause minor injuries requiring basic first aid or minor medical treatment.
Using a basic risk matrix chart, we can classify activities into low, medium, high and extremely high risk categories. The level of risk management required increases as the level of risk rises.

– Low: Minimal risk and/or unlikely to occur. These risks may be assumed.
– Medium: Remove or mitigate risks where possible, such as through rules, regulations, policies and procedures.
– High: Aggressive risk management required to reduce the likelihood of occurrence. Consider whether risks may be eliminated. Transfer risk through insurance.
– Extremely High: Consider eliminating activity. Aggressive risk management and monitoring required. Transfer risk through insurance.

Hypoxic Training — On the Surface
USA Swimming cautions that any drills that require breathing on a restricted schedule should occur on the surface of the water and only “in a training program of experienced swimmers in good physical condition with proper supervision and instruction.”

The risk of a swimmer losing consciousness on the surface is lower than during underwater swimming drills. While on the surface, swimmers are more likely to take a breath when needed whereas underwater they may resist the urge to breathe. Further, any loss of consciousness while swimming on the surface is more readily apparent to lifeguards allowing for a more timely rescue. If a swimmer loses consciousness underwater, that swimmer may go unseen for a period of time thereby increasing the likelihood of death or brain injury.

Using the risk management matrix to classify the level of risk for a SWB occurring while swimming on the surface, we arrive at severity level of severe and a frequency of seldom. With observant lifeguards and coaches, it is unlikely that death would result should a swimmer lose consciousness while swimming on the water. However, submersion, aspiration of water and resultant seizures could result in hospitalization. This places the level of risk at medium. Policies and procedures and are needed to help reduce the risk of a SWB incident, as is education of patrons, instructors and coaches.

Common risk reduction strategies include:
– Lifeguards required.
– Prohibit voluntary hyperventilation.
– Structure practice so as to minimize involuntary hyperventilation immediately prior to a hypoxic set.
– Encourage swimmers to breathe as needed.
– Allow adequate time for recovery, which will vary from swimmer to swimmer.

Underwater Drills
Common underwater activities that can lead to SWB include repeated underwater swims or kicking drills as well as stationary breath holding competitions for time. In both instances, the nature of the risk is clear: possible death. Even with successful resuscitation, complications including hypoxic brain damage and respiratory infection can occur.

Following many recent deaths of competent swimmers, including swim team members, lifeguards and young adults with military aspirations, it cannot be said that the risk of SWB is remote or improbable. Far too many young adults have died because of SWB, and the industry, media and general public has become increasingly aware of the real and present dangers of underwater swimming drills. The likelihood of a SWB incident can be classified as probable. With time, if underwater breath hold activities are allowed to occur it is likely (probable) that a swimmer will suffer a hypoxic blackout. Given that underwater breath holding activities resulting in SWB have led to death, the evaluation of the severity of this risk requires a finding of catastrophic. With a classification of both catastrophic and probable, underwater drills would be considered an extremely high risk activity. Organizations would be well advised to eliminate the risk all together through a ban on underwater drills in all but a carefully and closely regulated environment. Indeed, USA Swimming’s most recent update to the Safety Training for Swim Coaches program advises that hypoxic training should only occur on the surface of the water.

However, as underwater swimming is a required skill for many programs, including SCUBA and lifeguarding programs, strict rules must be developed to guide instructors and coaches in supervising underwater drills.

Considering the guidelines established by USA Swimming and the American Red Cross for hypoxic training, facilities should consider the following before allowing underwater drills:
– Instructor/coaches need additional experience and training before considering underwater drills.
– When swimming underwater, instruct swimmers to surface and breathe when necessary. Never resist the urge to breathe.
– Only allow one breath prior to submersion. SWB is closely linked to hyperventilation.
– Only allow underwater drills at the start of a workout when swimmers are not close to their maximum aerobic capacity (VO2 max).
– Only allow a distance of one length, one time. No repeats or challenges to see who can swim the greatest distance underwater.
– Allow adequate time for recovery, which will vary from swimmer to swimmer. A rule of thumb is to require a two minute recovery time before attempting another underwater swim.

In summary, SWB presents a very real risk to the health and safety of our patrons and athletes. Strict guidelines must be established prior to allowing any sort of hypoxic training at your facility.

From a recreational perspective, the risk of SWB from underwater swimming for time or distance may be considered extremely high. Facilities should ban this practice, educate patrons and staff, and post signs to help encourage compliance. Given the number of deaths attributable to SWB, allowing patrons to practice underwater breath holding could be tantamount to gross negligence.

From a competitive standpoint, there is no proven benefit to underwater drills. There is a potential benefit in extending the breathing pattern on the surface. Hypoxic training during swim team practice should be limited to drill on the surface, consistent with USA Swimming guidelines. Education of coaching staff and support from administrators and risk management officers is highly recommended.

For instructional programs that require underwater swimming, such as SCUBA or lifeguarding courses, education of instructors is critical to creating a safe environment. Lifeguards should be positioned to render assistance, and strict limitations on the underwater practice are needed. Hyperventilation must be prohibited.

Ultimately for many universities, coach education will be of paramount importance. Working with coaching and medical staff to develop a reasonable approach to hypoxic training, based in science, will allow coaches to reap the benefits of training without putting athletes at an unreasonable risk of injury or death.

– American Red Cross, Safety Training for Swim Coaches (2013)
– Aquatics International, Deathly Shallows, Kendra Kozen, Nov. 2011
– Aquatics International, Coming Up for Air, Judith Sperling, Feb. 2008
– Aquatics International, Dying for Air, Walter & Tom Griffiths, Feb. 2005
– Association Internationale Pour Le Developpment De L’Apnee, http://www.aidainternational.org
– Athletic Business, Don’t Hold Your Breath, Paul Steinbach, Jan 2007
– Confederation Mondiale des activites subaquatiques, www. cmas.org
– Department of Defense, Risk Reporting Matrix
– Sea & Shore, Winter 2009‎
– Shallow Water Blackout Prevention (http://www.shallowwaterblackoutprevention.org)
– Shallow Water Blackout UK (http://www.shallowwaterblackout.org.uk)
– SportRisk, Hyperventilation & Hypoxic Training, Judith Sperling, April 2011
– Swimming Technique, Lowdown on Hypoxic Training, Kevin Milak, Jul-Sep 2003
– Texas State, Risk Assessment Matrix, Campus Activities & Student Organizations
– USA Swimming, Safety/Loss Control Manual, Aug 2009.
– U.S. Navy, BUPERINST 1710.11C, Chapter 15 Aquatic Programs and Facilies, 1523. Hyperventilation and Breath-Holding (Jul 2001)
– YMCA, Statement of the YMCA of the USA Medical Advisory Committee, Nov 1999, Reaffirmed Feb 2011.

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