What triathlon really is
Triathlon is an endurance race that joins three sports in continuous sequence: first swimming, then cycling and finally running. The clock does not stop. It runs during the three segments and also during the transitions, the moments when the athlete switches sports. That is why the final time is the sum of everything, including what is lost tying shoes or putting on a helmet.
This continuity is what makes triathlon different from simply practicing three separate sports. The body must learn to move from one motor pattern to another under fatigue, and that is where much of the challenge lives.
The official distances
There is a ladder of distances, from accessible to extreme. The four most common are:
- Sprint: 750 m swim, 20 km bike and 5 km run. The most popular entry point.
- Olympic (or standard): 1,500 m swim, 40 km bike and 10 km run. The format raced at the Olympic Games.
- Half Ironman (70.3): 1.9 km swim, 90 km bike and 21.1 km run. The number 70.3 is the sum of the distances in miles.
- Ironman (140.6): 3.8 km swim, 180 km bike and a full 42.2 km marathon run.
There is also the super sprint, shorter than the sprint, designed for those starting from zero.
The transitions: the "fourth sport"
The transitions have their own names. T1 is the exit from the water to the bike, and T2 is getting off the bike to run. Many triathletes call the transition the fourth sport, because seconds lost there add up in the final result as much as minutes of training.
In a typical sprint race of age-group athletes, the two transitions combined usually add about 8 minutes to the total time, something around 8% of the entire race. Training transition area setup, equipment order and the gesture of putting shoes on yields time practically for free.
Brick training: teaching the legs to switch
Getting off the bike and starting to run produces the classic heavy legs feeling. That is not an impression. The switch demands redistributing blood flow, recruiting different muscle groups and bearing body weight again, all at once. Evidence shows that the first kilometer of running right after the bike is the most prone to an uncoordinated feeling, with greater variability in the running gait than when running without the prior effort.
The training answer for that is the so-called brick, a session that chains bike and run without a break, mimicking T2. The idea is habituating the nervous system to anticipate the switch, so running coordination stabilizes faster. The gain shows up precisely in the first minutes after getting off the bike, which are the most critical.
Managing load across three sports
Training three sports multiplies volume and the risk of accumulated fatigue. A well-established reference in the endurance sports literature is the polarized intensity distribution, popularized by physiologist Stephen Seiler. The central idea: about 80% of training at genuinely low, comfortable intensity, and the remaining 20% at genuinely hard effort, avoiding the constant middle ground.
For the triathlete, that means most swim, bike and run sessions should be easy enough to talk through, reserving hard effort for a few key sessions. Evidence suggests this bimodal pattern favors maximal oxygen uptake and movement economy, and helps sustain the volume of the three sports without accumulating excessive fatigue. Since each body responds differently, it is worth talking to a professional to calibrate volume and recovery.
How to start
For most people, the first race is about finishing, not competing. Start with the sprint or super sprint distance. Swimming is usually the segment that scares most, so investing in technique in the water early tends to pay off. A realistic initial routine spreads the three sports across the week, includes at least one short brick session and respects easy days as part of training, not as laziness.
The average time of a sprint race among age-group athletes hovers around 1h40, with wide variation depending on experience in the water and on the bike. Do not use that number as pressure: use it as a map of the terrain.
