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A time trialist is a road bicycle racer who can maintain high speeds for long periods of time, to maximize performance during individual or team time trials.

A cyclist riding a time-trial bicycle with aerodynamic wheels and aero bars.

In a traditional individual time trial, riders set off alone (not in a group or peloton) at intervals, typically anything from one to five minutes, and try to complete the course in as short a time as possible. In order to maximize the overall speed a time trialist must be able to maintain a steady effort throughout the event, of which the best measure is believed to be the rider's power at lactate threshold (LT) or aerobic threshold (AT). The best time trialists, such as Lance Armstrong and Jan Ullrich, are believed to have very high power output at LT/AT, which they can then maintain for the duration of the time trials.

To be a successful time trialist, a cyclist must have exceptional aerodynamic posture and be able to take in plenty of oxygen. Aerodynamic performance can also be improved by riders using 'skin suits', overshoes and streamlined helmets.

Bike technology is also important in time trials. Lance Armstrong's time trial bicycle for the 2004 Tour de France probably cost in excess of $10,000 (retail bikes are available for as much as 3,500 GBP, about 6,750 USD). By using aerodynamic components, a bicycle can be designed to minimize its drag coefficient, allowing a rider to drop his or her time by minutes during a long course. Many pros (Armstrong included) seek out older components based on their aerodynamic properties rather than the newest technology in their attempt to create the ultimate time trial bike. It all comes down to the individual rider's preference.

Time trials may also form individual stages of stage races. By incorporating time trial specialists into a cycling team, the team can lower its aggregate time dramatically.

• Individual time trial
• Team time trial