Fuel for Swimming

Wednesday, 22 October 2008, 15:53 • 1580 เข้าชมแล้ว
Swimming
Characteristics of the Sport
Training
Swimming requires a serious commitment to training. Typically, 6-12 sessions are
undertaken each week, with the distance covered in each session ranging from 1000-
2000 metres of quality work for a sprinter in taper phase to 10 kilometres for a distance
swimmer in the base phase of training. At the elite level workloads can involve 2-3 daily
sessions adding up to 6 hours of training per day. In addition, swimmers may undertake
some land-based aerobic training such as running or cycling as well as weight training
sessions. Training commitments are usually smaller at the club or school level.
Competition
Olympic swimming events last from 20 seconds to 15 minutes. Swimming is therefore a
highly anaerobic sport, with aerobic metabolism becoming more important as the race
distance increases. Although each event may be brief, swim meets are usually held
over 3 to 7 days, with swimmers typically competing in heats in the mornings and finals
in the evening. In minor carnivals, swimmers may enter a large number of events and
be required to swim 2 or 3 times in one day with 20 minutes to several hours between
events.
Physical Characteristics
Swimmers tend to be tall with pronounced upper body muscle development. Low body
fat is an advantage, since swimmers need to move their body weight through water.
However, some body fat in the right distribution may enhance flotation.
Other Issues
Many top swimmers are in their teens. Male adolescence is a period of heavy growth
and muscular development, requiring high-energy support. For males, the addition of an
intense training program means male swimmers can have trouble eating enough
kilojoules to meet energy needs. Adolescence for females brings hormonal changes,
which promote an increase in body fat. Despite heavy training loads, many female
swimmers can struggle to maintain low body fat levels. Long training hours restrict a
swimmer's lifestyle. This can either reduce the opportunities to eat in a busy daily
schedule or raise the importance of eating for comfort or entertainment. Access to food
can also be an issue when at swimming carnivals, and for athletes traveling to
compete.
Common Nutrition Issues
Daily Recovery
Strenuous daily training requires a high-energy, high-carbohydrate diet. Swimmers who
fail to consume enough carbohydrate will fail to recover adequately between training
sessions resulting in fatigue, loss of body weight and poor performance. Additional
energy requirements for growth may compound the problem. Swimmers with high energy
requirements need to increase the number of snacks during the day and make
use of energy-dense foods. It is good to have nutritious carbohydrate-rich snacks on
hand to eat straight after training to start the refueling process. This is especially
important for swimmers who travel long distances from their pool to work or home and
have to wait until the next meal can be consumed.
Fluid Needs in Training
High-intensity exercise in the steamy environment of a heated indoor pool, or outdoors
in the sun, can lead to moderate sweat losses, which are not obvious when the
swimmer is already wet. Smart swimmers bring drink bottles to the pool deck and drink during rest periods or between sets. Sports drinks provide an additional fuel supply for
long training sessions. In a fluid balance study undertaken on the Australian Swimming
Team in Atlanta in 1995, we measured average sweat losses of ~125 ml per kilometre
in training or about 600 ml per workout. These swimmers were provided with both water
and sports drink at the session and managed an average intake that perfectly matched
their losses (125 ml per km). Of course, some swimmers were better at matching losses
than others. And during anaerobic threshold sets, sweat losses increased to 170 ml/km.
Iron Status
An iron imbalance may occur in swimmers undertaking heavy training who fail to
consume sufficient iron. Female swimmers on weight loss diets are particularly at risk.
Iron levels should be checked regularly when in heavy training. Iron-rich foods such as
lean red meat and breakfast cereals fortified with iron should be included regularly in
the diet. Iron-rich plant foods such as wholegrain cereals, spinach and legumes should
be combined with animal iron sources (e.g. wholegrain pasta with bolognese sauce)
and vitamin C sources (e.g. glass of orange juice consumed with breakfast cereal) to
improve iron absorption. A sports dietitian will be able to provide specific dietary help.
Immune Status
Swimmers often worry about getting sick during periods of heavy training. Many
nutritional supplements and strategies have been suggested to keep the swimmer from
catching coughs and colds. To date, the most important strategy emerging from
immune studies of athletes is to keep well fuelled during training sessions. Sports drink
during the workout and a recovery snack afterwards help to reduce the stress on the
immune system.
Competition Nutrition
Muscle glycogen stores can be filled by 24 hours of a high-carbohydrate diet and rest.
Swimmers who are undertaking a long taper may need to reduce total energy intake to
match their reduced workload; otherwise unwanted gains in body fat will occur. Fluid
levels and carbohydrate stores need to be replenished between events and between
heats and semi-finals/finals. Drink a carbohydrate-containing fluid such as sports drink,
fruit juice or soft drink when there is only a short interval between races. Snacks such
as yoghurt, fruit, cereal bars or sandwiches are suitable for longer gaps between races,
or for recovery at the end of a session. Between day heats and evening final sessions,
most swimmers eat a high-carbohydrate lunch and have a nap. On waking, a
carbohydrate-rich snack is eaten before returning to the pool.
Case Study
Grant was a young up and coming swimmer who began to struggle with fatigue after
making the jump to training with an elite squad. As Grant's training sessions increased
to 12 per week, his times began to drop off and he struggled to maintain weight. A
sports dietitian examined Grant's diet and found additional carbohydrate was needed to
cover Grant's extra training needs. In particular, more carbohydrate was needed for
Grant to replenish muscle glycogen stores between sessions. At 80 kg, a daily intake of
600-800 g of carbohydrate each day was required. Although Grant loved to eat high
carbohydrate foods such as bread, cereal, fruit, potato, rice and pasta, he struggled to
consume sufficient quantities each day of these bulky foods. Grant's dilemma was
solved by increasing the number of meals consumed and making use of portable, easy to-
eat snacks. With some planning and preparation Grant made sure he always had
access to quick easy-to eat high-carbohydrate snacks such as smoothies, liquid meal
supplements, cereal bars, sports drink, yoghurt, fruit and bread. He started having
carbohydrate-rich foods and drinks immediately after each training session so that
muscle glycogen storage was activated as quickly as possible. Grant's intake was
increased to 800-900 g of carbohydrate and 21,000-23,000 kilojoules each day. Within
three weeks Grant had regained some weight and was feeling a new energy at training.
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