The success rate of swimming the English Channel is approximately 10% of all those who have attempted it. The shortest distance is approximately 19 nautical miles (35200 metres) from Shakespeare Beach, Dover to Cap Gris Nez. 'S' is a 'Female Masters' swimmer, with a mass of 64kg, and a stature of 1.67m. She trains 3 times per week & annually competes in 200m freestyle. 'S' is training to swim the English Channel in 2010, of which the average water temperature is 15°C to 18°C and the average completion time is 12 to 16 hours; although some have known to take 20+ hours. Entrees have to pass an examination first, to determine whether they are able enough to even attempt the crossing. They have to complete a 6 hour swim in a 60-degree pool. However, she has no cold or open water experience. To aid the chances of her success, this case study will identify challenges faced and provide suitable recommendations to enhance the chances of her successfully crossing the channel.
When swimming in such cold conditions the body adapts and physiological changes occur. Huttuenen et al. found that having a high body composition will help an athlete to sustain core heat and prevent hypothermia. They also found that when swimming in such condition for a thinner swimmer, the exercise accelerated the drop in body temperature. Therefore a high percentage in body fat will be beneficial to 'S' as it holds core temperature in. A reason behind this is (Lambertsen & Greenbaum, 1963) because water has a specific heat approximately 1000 greater than air, so each cubic centimetre can take a thousand times more heat from the body compared to air.
'S' therefore as preparation, should concentrate upon increasing her body composition. Walker (2006) states that to gain weight for such an event, a diet of both complex carbohydrates and unsaturated fats are suitable. Too much simple sugar's such as glucose & fructose, will make you lethargic and cause difficulty when training. Therefore they should be avoided; however white meats & vegetables should still play a major role in one's eating patterns, as they are essential for a healthy diet. Women in general have a higher body fat percentage than men. McArdle et al. (2007, pg 225-227) states that due to females body composition, they have more buoyancy and therefore have a lesser energy expenditure then men when swimming at the same velocity. As their fat is situated more equally over their entire body & legs, the buoyancy aided the legs in floating, preventing drag, thus becoming more economical. They found that the front crawl swimming technique provided the greater economy, as it required less oxygen consumption at any velocity compared to the back crawl & breaststroke. Because of this, the front crawl should be primarily be the technique used by 'S'. They also state that physiological adaptations occur in cold water; of which are programmed to stabilise core temperature, such as shivering.
To prevent hypothermia, a suitable method which 'S' should apply to her training is to allow her body to acclimatise to the water temperatures which she will face. (McArdle et al., 2007, pg 662-663) However humans possess a much less capacity for adaptation to long-term exposure to the cold compared to high temperature conditions. Frequent exposure to cold water conditions has been known to cause a thermogenic response; of which gives the swimmer a higher 'shivering threshold'. Similarly, the resting metabolic rate responds to such conditions by increasing. This means that less energy is used to maintain core temperature; hence the athlete will sustain higher glycogen stores for the swim.
A way in which 'S' can acclimatise to cold conditions are quite simple. Instead of taking hot showers & baths, she should be having cold ones and any chance she has to swim in the sea would be very beneficial. Not only for acclimatising but also for the physiological adaptations which occur during training. She should practice swimming against the tide, in open waters & if safe to do so (with aid from a guide boat) swim in choppy waters. Walker (2006) suggests that when training the body for this event, it would be a good idea to be swimming approximately 50 miles per week. This training should primarily take place in cold waters; however pool swimming will still be beneficial by improving speed, although the body will not have to acclimatise as pools are usually heated. Although this will increase overall fitness and help train an athlete to become more economic, it can be difficult to recover each week after such intense exercise.
In order to reduce such difficulty, 'S' should maintain a diet of high carbohydrates with good proteins such as chicken. During the event itself 'S' will have to eat to maintain her glycogen stores. This means that eating during swimming will be essential and she should practice this during training. The quicker she can finish feeding in the water, less time will be wasted or spent eating. Such foods when in the water could be carbohydrate gels. These are easy to digest and take little time to consume.
(Jones & Doust, 1997) An effective method used to record and evaluate fitness levels in endurance athletes is the OBLA Test. It is used by cyclists, runners, tri-athletes etc to determine the lactate threshold of an athlete. For 'S' to swim the English Channel with as much absence from lactic acid as possible, her lactate threshold must firstly be determined. The OBLA Test does that by using an ergometer to measure the maximum physical capacity of an athlete. Once the lactate turnpoint & the heart rate of which it occurs at is identified then 'S' has a guideline of her swimming intensity. When training, if she sustains an intensity just below that turnpoint then she will be able to swim at maximum economy with the prevention of lactic build up. With the absence of this build up, 'S' will increase her chances of successfully crossing the channel.
However with intense training, that lactate threshold will increase. Therefore through training and a raised threshold she will be able to swim at a greater velocity while remaining below that threshold. The OBLA Test is an effective way to evaluate 'S' training and provide guidelines & targets she must reach to increase her chances.
In conclusion so long as 'S' takes the advice and training methods from this study, she should have a very good chance of successfully completing the swim and in good time. Although these precautions such as diet, training & equipment (wetsuit) are under our control, there are other variables which cannot be controlled; such as tides and how 'choppy' the water is. These can vary during the race and even the day before, therefore such factors should taken into account and perhaps over eating for the race, to make sure the glycogen stores are more than sufficient. Other than those variables 'S' should be well prepared for this challenge.
References
HUTTUNENA, P et al. (2000) Effects of long-distance swimming in cold water on temperature, blood pressure and stress hormones in winter swimmers. Journal of Thermal Biology, 25, 171-174.
JONES, Andrew and DOUST, Jonathan. (1997) The Conconi test is not valid for estimation of the lactate turnpoint in runners. Journal of Sport Sciences, 15, 385-394.
LAMBERTSEN, Christian and GREENBAUM, Leon. (1963) Proceedings second symposium on underwater physiology [online]. National Academies, 1963.
WALKER, Steven. (2006) English Channel Training Info [online] Article from SRI CHINMOY Marathon Team.
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