Starting a race at a pace above what you can sustain may seem like a good strategy. After all, gaining a few seconds in the first kilometers can create the feeling that you are “getting ahead.”
The problem is that, in endurance events, what matters is not only how fast you can start, but how much of that pace you can sustain until the finish line.
The distribution of effort throughout a race, known as pacing, is a fundamental component of performance. It involves continuously adjusting intensity, perceived exertion, and speed according to the distance remaining, fatigue level, course profile, and environmental conditions.
And that is precisely why starting too fast can come at a high cost later in the race.
What happens when you start above a sustainable pace?
During the first few minutes, the body is still relatively fresh. Perceived exertion may be low, and the excitement of the start can be high. This makes it easy to run or cycle above the planned pace without immediately noticing the consequences.
However, excessively increasing intensity shifts exercise toward higher-intensity domains, increasing the contribution of anaerobic energy pathways and accelerating the development of fatigue.
In endurance exercise, changes in intensity can significantly affect both central and peripheral fatigue throughout the event.
In practice, this means that a few seconds gained at the beginning can result in minutes lost when fatigue catches up later.
The energetic cost of an aggressive start
The higher the intensity, the greater the energy demand tends to be.
In a long-distance event, the goal is not simply to produce as much energy as possible at that moment, but to manage the available resources throughout the entire course.
An excessively fast start can increase reliance on carbohydrates and accelerate muscle glycogen utilization. At the same time, higher intensity increases metabolic demand and may bring on the sensation of fatigue earlier.
This does not mean that “starting fast always depletes glycogen.” The response depends on intensity, duration, training status, carbohydrate availability, and nutritional strategy.
The key point is that the intensity chosen at the beginning changes the physiological cost of the entire race.
That is why, in long endurance events, preserving the ability to produce effort in the final kilometers may be more important than gaining a few seconds at the start.
More intensity also means more fatigue
The problem is not only about energy availability.
A pace above what can be sustained may also increase the accumulation of metabolites associated with high-intensity exercise, neuromuscular disturbance, and perceived exertion.
As the race progresses, accumulated fatigue changes the relationship between effort and speed. The athlete may need to work progressively harder to maintain a pace that initially felt comfortable.
That is why the feeling of “I’m flying” during the first few kilometers can turn into “I can’t hold this pace” later on.
Fatigue during endurance exercise is multifactorial and involves peripheral, central, and perceptual components, all of which contribute to the regulation of exercise intensity throughout the event.
And heat can make the cost even higher
Pacing cannot be determined by looking at the clock alone.
Temperature, humidity, elevation, wind, and course characteristics can all change the physiological cost of exercise.
In hot environments, for example, starting above a sustainable pace can rapidly increase heat production and cardiovascular strain. During long events, this can further compromise the ability to maintain intensity later in the race.
That is why the same pace that may be appropriate on a cool morning can be excessive during a race held in hot conditions.
The strategy needs to consider the effort that a given pace represents under the actual race conditions, rather than simply the number displayed on the watch.
Why can the first kilometers be misleading?
There is also a psychological component.
At the start, the athlete is rested, motivated, and surrounded by other competitors. It is common to let the pace be dictated by the environment, following the person next to you or trying to take advantage of the feeling of being fresh.
The problem is that your ability to sustain that pace has not yet been tested in that specific context.
With experience, athletes become better at recognizing the relationship between intensity, perceived exertion, and expected duration. Research suggests that pacing behavior is a skill that can be developed through experience and repeated exposure to the task.
In other words, knowing when to hold back is also a performance skill.
Pacing does not mean running slowly
Holding back does not mean racing too conservatively.
The ideal strategy depends on the duration, sport, course, athlete's level, and characteristics of the competition. In some situations, changes in pace and surges are inevitable or are even part of the dynamics of the event.
The goal is to avoid making the initial intensity so high that it compromises the ability to respond later.
In longer endurance events with relatively consistent courses, distributing effort more evenly can be an effective strategy. For less experienced athletes, a more balanced approach may also help prevent a significant drop in speed toward the end.
So, what pace should you choose?
One of the most important questions before a race should be:
“What pace can I sustain?”
Not:
“What is the fastest pace I can run right now?”
A practical strategy is to establish a target pace or power range for the beginning of the race and avoid exceeding it simply because the initial effort feels easy.
For example, during a long-distance running event, the first few kilometers can be completed close to the planned race pace while monitoring:
- perceived exertion;
- heart rate;
- environmental conditions;
- muscle response;
- carbohydrate and fluid intake;
- whether there is still room to increase the pace.
From there, the pace can be adjusted as the race progresses.
What about nutrition strategy?
Pacing and nutrition should not be planned separately.
Carbohydrate availability during exercise is one of the tools used to help sustain intensity during endurance events. However, nutrition cannot compensate for inadequate pacing.
In other words, increasing carbohydrate intake will not erase the physiological cost of starting well above a sustainable pace.
Race nutrition should be part of a strategy that has been tested in training, taking into account event duration, intensity, gastrointestinal tolerance, and individual characteristics.
The same applies to hydration and sodium. Requirements vary according to exercise duration, environmental conditions, sweat rate, and individual factors. During long events or races in the heat, these variables should be considered alongside pacing.
A good race is not necessarily one that starts the fastest
The goal of an effective pacing strategy is to reach the final kilometers with the ability to continue producing effort.
This does not mean that every race should finish faster than it started. Current evidence does not support a single universal pacing strategy for every situation. Different approaches can produce similar outcomes depending on factors such as event duration, task demands, and individual characteristics.
The point is different: your initial pace needs to make sense for how much of the race is still ahead of you.
Starting too fast can create a physiological debt that will be paid later. Starting in a controlled manner allows the athlete to use their capacity to increase effort when it matters most.
At your next race, think beyond the start
Before accelerating during the first few kilometers, ask yourself a simple question:
“If I keep this exact pace, how will I feel 60 minutes from now?”
If the answer is “I probably won’t be able to maintain it,” that may not be your race pace.
In endurance sports, performance is not simply about producing more. It is about producing enough, for the right amount of time, while still having the capacity to continue when fatigue sets in.
Because in the end, the seconds gained at the start are only valuable if you can still run, cycle, or swim strongly when the finish line is getting closer.
