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Thursday, March 22, 2012

How Far Could A Human Swim?

Theoretically, how far could an open water swimmer continue in one non-stop ultra marathon swimming effort?

There are dozens of people who have swum non-stop for more than 24 hours, others who have swum more than 40 hours, but only a handful who have swum more than 60 hours, and only a precious few who have swum more than 80 hours.

Straight. Non-stop. No sleep. No getting out.

Practically, swimmers like Susie Maroney and Diana Nyad have come close to finding out with their swims in the Caribbean Sea. Kevin Murphy has been in the cold, rough English Channel for 52 hours ... and regretted coming out. The longest distance and time an adequately trained marathon swimmer could swim is based on a number of factors:

1. Water Temperature
2. Sleep Deprivation
3. Watr Salinity
4. Third Spacing
5. Swimmer's Speed and Pacing
6. Swimmer's Personality
7. Turbulence
8. Marine Life
9. Equipment
10. Nutrition
11. Body fat index
12. Conditioning
13. Elevation of Residence
14. Age of the swimmer
15. Gender
16. Support crew
17. Luck

1. Water Temperature
Water temperature is important because the water temperature, ideally, would be at least 28°C (82.4°F). It may be too warm in the first two days, but the warmer waters held in days 3, 4 and on. However, when the water temperature is in this range, it usually means that the air temperature is at least this warm. This amount of warmth can be a detriment to the swimmer in the middle of the day, but quite welcomed at night.

2. Sleep Deprivation
Sleep deprivation is more of a safety issue in the water than it is for endurance athletes on land. On land, you can wobble and crash if you fall asleep or even move in a bit of a slumber, but in the open water, this is not possible. Once the swimmer's vision becomes narrower and things appear dark or tunnel-focused, they are entering a danger zone. Additionally, in warm water, a swimmer would tend to get sleepier faster than in cooler water, another limiting factor.

3. Water Salinity
The salinity of the water is a major factor because the skin's pores and orifices (especially in and around the mouth) become severely irritated. It affects some swimmers more than others, but it does affect everyone over 24 hours in the water and, severely, for those who are in the water over 48 hours.

4. Third Spacing
There is also the factor of Third Spacing where your body naturally expands after being submerged for lengthy periods of time which will affect your physiological performance over time. It affects some swimmers more than others, but it does affect everyone over 24 hours in the water and, severely, for those who are in the water over 48 hours especially when the water is warm.

5. Swimmer's Speed and Pacing
The speed of the swimmer is less of a factor unless tides and currents are an issue. Most importantly in order to maximum time in the water (and therefore distance), an individual with an efficient swimming stroke has a significant advantage over others. But most importantly, is the athlete who is able to pace themselves physically and psychologically well.

6. Swimmer's Personality
Swimmers who do marathon swims are a special breed who can mentally remove themselves from the task at hand. Because their vision and hearing is impaired due to their position in the water, a steely type of personality is required.

7. Turbulence
Calm water is ideal, but rough water is bearable if the turbulence is with the swimmer. Rough water conditions work not only on the swimmer, but is also a living hell for the crew, especially when the swimmer is in the water over 48 hours.

8. Marine Life
Marine life must be a consideration. To maximum time in the water, swimmers will definitely want to avoid jellyfish, sharks, Portuguese Man o War, sea nettles, sea snakes or the like.

9. Equipment
Use of a wetsuit, hand paddles and fins would obviously be easier than swimming under the traditional rules of the sport, but wetsuit swims are an entirely different discipline when maximization of time and distance are the goals. Equipment also includes illumination that is required for night swimming.

10. Nutrition
Most ultra distance swimmers eat well enough during their swim. Athletes can choose scientifically formulated foods (e.g., gel packs) or normal food (e.g., bread, fruits, chocolate). While mega-marathon swims can be limited by not eating or hydrating enough, proper nutrition is essential to performing well in the 50+ hour range. But when swimmers are in the water for extended periods, especially salt water, their taste buds are shot and nothing tastes like it does on land.

11. Body Fat Index
Ultra-endurance athletes of any discipline usually have a higher body fat percentages than elite marathon athletes (runners or swimmers). Body fat insulates the body, is more buoyant than muscle and enables the body to last longer in the open water. While some endurance athletes lose significant weight in their marathon efforts, carefully monitored marathon swimmers lose less weight during a swim because they refuel and hydrate often. Because the water temperature of even the warmest oceans is more than 10°F (l2°C) lower than the normal core body temperature, body fat percentage is helpful in the world of ultra-marathon swimming.

12. Conditioning
It is inevitable that the athlete is very well-prepared physiologically to complete an ultra-marathon swim. Training for a 2+ day swim takes serious training. At the elite level, the athlete's mental outlook is so strong that their body generally gives up before their mind does. This is why seriously committed marathon swimmers - if allowed to by their support crew - are fished out of the water; their mindset allows them to reach their physical limits.

13. Elevation of Residence
Living at high altitude may help; however, it is also true that the higher an athlete lives, the less likely they are to have access to good year-round open water training venues. Training exclusively in a pool at high altitude is not optimal for an ultra-marathon swim.

14. Age of Swimmer
Maturity is most definitely a necessity for ultra-marathon swimmers. While there are always exceptions (Lynne Cox, Susie Maroney and Nick Adams were doing ultra marathon swims at precocious ages), maturity usually comes with age and life experiences. It is much ore likely that the better ultra-marathon swimmers will be over the age of 25 than not.

15. Gender
Many marathon swimming world records are held by men (e.g., Philip Rush, Petar Stoychev, Abo-Heif, Kevin Murphy). But many women have also been successful in ultra-marathon swimming (e.g., Vicki Keith, Yuko Matsuzaki, Penny Palfrey). Many scientists state that the female gender are better physiologically at marathon distances although neither gender has a lock at the most extreme ends.

16. Support Crew
A successful ultra-marathon swimmer will have a well-prepared, patient, knowledgeable support crew with a high navigational IQ and an intimate understanding of the swimmer. The best escort pilots and teams can get an athlete across an ocean or a lake or down a river much better, safer and faster than an inexperienced crew. The positioning of an athlete relative to the boat and currents, the date of the swim (taking into account full moons and tidal flows), knowledge of the swimmer's abilities and training, and a deep well of knowledge of the body of water are absolutely critical to success.

17. Luck
Luck cannot be overstated in the dynamic environment of the open water. Every open water swimmer needs luck when swimming over 24 hours non-stop in an ocean, lake or river. Large bodies of water rarely remain the same during mega-marathon swims because the elements can change so radically. If luck is on the athlete's side, then the conditions are conducive to a truly long marathon swim. If the conditions deteriorate during the swim, then the chances of doing the ultimate ultra-marathon swim are significantly reduced or, in most cases, prematurely eliminated.

We estimate the outer limits of swimming non-stop in the open water without sleep is 80-100 hours and would best be done swimming/floating downstream in a warm-water river that starts in the highlands (not the mountains) and flows out to the ocean in a non-industrial area. Ideally this fresh-water river would be wide enough where rapids are not an issue (and therefore rocks) and in a location where boat traffic was minimal. Salt water locations would be more challenging, but the tidal flow may be more conducive to a longer swim in the ocean. There are several rivers in the temperate regions of Africa that fit this bill, although several people have swum very long distances down the Mississippi, Hudson, Parana, Danube rivers over the past 150 years.

Copyright © 2012 by World Open Water Swimming Association


  1. Great question.. really. How far can the human body go?
    What was the length of Penny Palfreys Carribean swim? Over 24 hours but not 60?
    There is a quote I like*
    "we are capable of more than we can believe"


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