While specific rules for triathlon can vary depending on the governing body (e.g. World Triathlon, USA Triathlon), as well as for an individual race venue, there are some basic universal rules. Traditionally, triathlon is an individual sport and each athlete is competing against the course and the clock for the best time. As such, athletes are not allowed to receive assistance from anyone else outside the race, with the exception of race-sanctioned aid volunteers who distribute food and water on the course.


Transition area (bicycles) of Hamburg Triathlon, 2002
Triathlons are timed in five sequential sections:

from the start of the swim to the beginning of the first transition (swim time);
from the beginning of the first transition to the end of the first transition (T1 time);
from the start of the cycling to the end of the cycling leg (cycling time);
from the beginning of the second transition to the end of the second transition (T2 time);
finally from the start of the run to the end of the run, at which time the triathlon is completed.
Results are usually posted on official websites and will show for each triathlete his/her swim time; cycle time (with transitions included); run time; and total time. Some races also post transition times separately.

Other rules of triathlon vary from race to race and generally involve descriptions of allowable equipment (for example, wetsuits are allowed in USAT events in the swimming stage of some races when the water temperature is below 25.6 °C (78.1 °F)), and prohibitions against interference between athletes. Additionally, the use of flippers or other swim propulsion and flotation aids are illegal in triathlon and can result in disqualification.

One rule involving the cycle leg is that the competitor's helmet must be donned before the competitor mounts (or even takes possession of, in certain jurisdictions) the bike, and it must remain on until the competitor has dismounted; the competitor may not be required to wear the helmet when not on the bicycle (e.g. while repairing a mechanical problem). Failure to comply with this rule will result in disqualification. Additionally, while on the bike course, all bicycles shall be propelled only by human force and human power. Other than pushing a bicycle, any propulsive action brought on by use of the hands is prohibited. Should a competitor's bike malfunction they can proceed with the race as long as they are doing so with their bicycle in tow. There are also strict rules regarding the 'bike mount' line. Competitors may not begin riding their bicycle out of transition until they are over a clearly marked line. Mounting the bike prior to this may incur a penalty (example: a 15-second time penalty at the London 2012 Olympics was imposed on Jonathan Brownlee, a competitor from Great Britain, for mounting his bike too early.)

Other time penalties can be incurred during the race for, among other things, drafting on the bike in a non-drafting race, improper passing, littering on course, and unsportsmanlike conduct.
Extract the basic universal competition sections of the triathlon in order, and explain each section.
Triathlons are timed in five sequential sections.
From the start of the swim to the beginning of the first transition (swim time). The use of flippers or other swim propulsion and flotation aids are illegal.
From the beginning of the first transition to the end of the first transition (T1 time).
From the start of the cycling to the end of the cycling leg (cycling time). The competitor's helmet must be donned before the competitor mounts the bike, and it must remain on until the competitor has dismounted.
From the beginning of the second transition to the end of the second transition (T2 time)
Finally from the start of the run to the end of the run, at which time the triathlon is completed.