This is an excerpt from Pacing by Kevin Thompson.
Triathlon is a complex and time-consuming sport to train and prepare for. Triathletes need a keen sense and understanding of their physical and technical capacities to position themselves correctly in races to optimise their performances. They also require special equipment to cope with variable environmental and course conditions (wetsuit, bicycle, gear ratios, wheels). These factors all feed into the pacing strategy. Mastering each of the three exercise modalities requires many hours of training as well as enormous commitment and discipline.
Olympic triathletes have to strike a balance between exercising at a severe intensity (i.e., above critical power; see chapter 5), perhaps to make a break in the race, and settling into an even pace (i.e., below critical power) to conserve aerobic and anaerobic capacity. Rather like marathon running, the event is too long (1.5 to 2 hours) for triathletes to exercise beyond their critical power for the whole race; doing so would lead to premature fatigue because they would reach their V̇O2max and deplete their anaerobic capacity well before the end of the race. When deciding when to exercise at a severe intensity, triathletes need to take into account issues such as their relative efficiency in each of the exercise modalities, whether a prolonged surge could catch them up to the leading bunch and then allow a reduction in intensity by drafting behind others, or whether they can gain a time advantage from the course conditions ahead (e.g., heading into a transition zone or climbing a hill).
In longer triathlon races lasting more than 3 hours, carbohydrate (glycogen) depletion, hyperthermia (when racing in hot conditions), muscle damage and a loss of central drive and motivation are the most likely causes of fatigue, which might derail the pacing strategy (Burnley & Jones 2007). The mental aspects of enduring hours of training and then competing for many hours in an Ironman triathlon are particularly daunting. For the much shorter Olympic distance triathlon, these factors are still a significant concern in training but perhaps less so in competition. Nevertheless, common to both forms of triathlon is the fact that successful competitors require considerable mental toughness to persevere with their pacing strategies while suffering worsening levels of fatigue and discomfort as the race progresses.
Physically, triathletes face a number of challenges that affect their race preparation and pacing strategies. The cumulative fatigue that results from training in three exercise modalities can easily lead to overuse injuries and high degrees of muscle soreness. In addition, maintaining the correct energy and fluid balance is also a challenge; a deficit can lead to ill health and poor training. To be able to train and compete at the appropriate exercise intensities, triathletes must maintain optimal muscle glycogen (carbohydrate) levels so they can execute their pacing strategies. A reduced rate of carbohydrate metabolism towards the end of a race will adversely affect exercise intensity and subsequently the race pace. In Ironman triathlon, sufficiently lowered carbohydrate levels can even lead to hypoglycaemia (abnormally low blood glucose) and ketosis (excessive accumulation of ketones) and a resultant loss of coordination or collapse (St Clair Gibson et al. 2013).
Elite triathletes train two or three times daily and therefore need to consume a high-carbohydrate diet to replenish muscle and liver carbohydrate (glycogen) stores. They also need to diligently replace water and salt losses from sweating during exercise. To maximise carbohydrate stores in the 24 hours prior to a sprint or Olympic distance triathlon, the triathlete might take in around 7 to 8 grams of carbohydrate per kilogram of body weight. In the 48 to 72 hours prior to an Ironman triathlon, a carbohydrate intake of around 10 to 12 grams of carbohydrate per kilogram of body weight per day is recommended (Australian Institute of Sport 2014).
Triathletes tailor their nutrition intake to the duration of the race and the environmental conditions. The longer and hotter the race is, the greater is the risk of severely depleting their glycogen stores and also dehydration. General recommendations as to the amount of carbohydrate a triathlete needs to take in during a race vary. However, for short races lasting around 2 or 3 hours a carbohydrate intake of between 30 and 60 grams (1 and 2 oz) per hour is recommended, whereas in a race lasting beyond 3 hours an intake in excess 90 grams (3 oz) per hour is recommended (Gatorade.co.uk 2014). Ironman triathletes are advised to take in 1 to 1.5 grams of carbohydrate per kilogram of body weight per hour - for example, 70 to 105 grams (2.5 to 3.7 oz) each hour for a 70 kg (154 lb) competitor (Australian Institute of Sport 2014).
Triathlons often take place in hot and humid conditions and so competitors need to acclimatise by training and practising their pacing in similar environments. This ensures that they adapt physiologically and psychologically to the conditions. A well-considered hydration strategy, taking into account the triathlete's personal rate of sweating, can mitigate against exercise-induced dehydration. Avoiding dehydration during a triathlon is important because it affects the body's ability to maintain sufficient blood volume to adequately support heat loss and to maximise oxygen delivery to maintain the desired race pace (see the section "Considerations for Longer-Term Endurance Events" in chapter 5).
Triathlon races occur under various changeable environmental conditions (e.g., weather, course topography, road surface, water temperature, tides). Thus, 'laboratory' studies simulating triathlon races are, of course, limited by the environmental conditions imposed. Power outputs, or speeds, vary greatly and frequently during competitive races, whereas in the laboratory, triathletes often demonstrate more constant power outputs. Nonetheless, findings from research studies do inform our understanding of the pacing strategies of triathletes.
Read more from Pacing: Individual Strategies for Optimal Performance by Kevin Thompson.