Where Should You Push Harder on the Bike in a Triathlon?

Two triathletes can finish a 90 km bike leg with the same average power and very different times.

Position and equipment explain some of that difference. Pacing can explain another part.

A watt spent climbing a gentle hill does not necessarily buy the same time saving as a watt spent powering down the other side. The challenge is deciding where a little more effort is worthwhile, without borrowing too much from the run.

Should you ride at constant power?

On a flat road in calm conditions, a steady power output is a sensible starting point. Repeated surges followed by easing off generally offer little benefit when the conditions stay the same.

Hills and changing wind complicate the picture. Modelling research has found that controlled increases in power uphill or into a headwind, balanced by reductions on easier sections, can improve cycling times.[1]

But this does not mean attacking every climb. In a triathlon, any bike time gained has to be considered alongside the effort required and the run that follows.

Why a little more effort uphill can help

You spend more time covering a kilometre uphill than a kilometre downhill. On many rolling courses, a modest increase in climbing power can save more time than you lose by easing off on the descent.

The useful word is modest.

Shift early, find a comfortable cadence and let your power rise within a limit you have chosen before the race. Avoid letting a short ramp, another rider or a disappointing speed reading turn a controlled climb into a hard interval.

Climb duration matters too. A power level that feels manageable for one minute may be inappropriate for a twenty minute ascent.

Choose gearing that lets you stay within your plan. If every steep section forces you into an effort you cannot sustain, your pacing problem may partly be a gearing problem.

A worked example over 90 km

Imagine a gently rolling course with nine repetitions of a 5 km climb at 1% followed by a 5 km descent at 1%. That gives 90 km and approximately 450 metres of climbing.

We model the same rider and bike using two approaches:

|Pacing approach     |Uphill power|Downhill power|Average power|Modelled finish time|
|--------------------|------------|--------------|-------------|--------------------|
|Constant power      |220 W       |220 W         |220 W        |2:25:26             |
|Controlled variation|235 W       |About 201 W   |220 W        |2:24:22             |

The controlled approach is approximately 1 minute 4 seconds faster.

There is no increase in average power. The difference comes from where the effort is applied.

The downhill target is lower by more than the uphill target is higher because the rider spends longer climbing than descending. Average power is calculated over time, not distance.

These are illustrative figures, not a promise for your next race. The course is deliberately simplified, and this is one comparison rather than a claim to have found the optimal strategy.

Model assumptions: 85 kg combined rider and bike mass; CdA 0.25 m² in both directions; rolling resistance coefficient 0.004; air density 1.225 kg/m³; drivetrain efficiency 97.5%; no wind. Steady state speeds are calculated for each gradient. Downhill power is solved at 200.775 W to retain a time weighted average of 220 W, then rounded in the table. The model excludes acceleration, braking, corners, changes in position and fatigue.

Same average power does not mean the same physical cost

This is the important limit of the example.

A variable ride can place greater demands on the rider than a steady ride with the same average power. Experimental research comparing variable and constant power has investigated these differences, while pacing models that account for physiological cost favour more restrained changes than models constrained only by average power.[2,3]

Normalised power can help put a variable ride in context because it gives greater weight to harder efforts. It is an estimate, rather than a guarantee of how well you will run.

Do not judge your pacing solely by the average watts at the finish. Review the hard efforts, how you felt and what happened on the run.

When should you ease off downhill?

As speed rises, extra power can deliver relatively small additional speed gains. On a fast descent, maintaining a controlled position and following the road safely may be more useful than forcing the pedals to keep your average power up.

There is no universal speed where everyone should stop pedalling. Gradient, wind, gearing, your position and the road ahead all affect the decision.

On a gentle descent, continuing to pedal at reduced power may still be worthwhile. On a steep or technical descent, prioritise control and braking.

Do not sprint towards a corner only to brake away the speed you have just created.

Should you push harder into a headwind?

A small, planned increase may help, provided you compensate elsewhere and remain within your sustainable race effort. It is not a reason to force your normal cruising speed into the wind.

In one small laboratory study, controlled constant and variable pacing both improved times compared with riders’ initial self selected pacing. The difference between the two controlled strategies was only around two seconds.[4]

That is a useful reminder: avoiding a poor pacing decision can matter more than finding a theoretically perfect one.

Keep your aero position when conditions allow it, accept that your speed will drop and judge your effort against your plan. When the wind turns in your favour, let the speed come without automatically chasing an even bigger number.

Build the plan around the run

Before race day, decide your intended effort on ordinary roads, a sensible ceiling for sustained climbs and where the course offers opportunities to ease off.

Practise those decisions during longer rides, using your race position and fuelling setup. Include a run afterwards when appropriate within your training plan, so you can assess the complete session.

For a full distance race, allow for the longer exposure to fatigue. A strategy that works over 90 km should not automatically be carried across to 180 km.

During the race, keep the opening kilometres controlled. Adapt to heat, fatigue or unexpectedly difficult conditions rather than forcing a number that no longer matches the day.

Spend your effort where it helps, but judge the result at the finish line, not just at the end of the bike leg.

Sources

1. Swain (1997), A model for optimizing cycling performance by varying power on hills and in wind.

2. Physiological Response to Cycling With Variable Versus Constant Power Output, Frontiers in Physiology (2020).

3. Drechsler (2026), Balancing trade-offs to optimise pacing in cycling time trials under variable conditions.

4. Atkinson and Brunskill (2000), Pacing strategies during a cycling time trial with simulated headwinds and tailwinds.

The 90 km comparison is an original illustrative calculation for this article. The cited studies are not evidence that this particular strategy will improve a triathlon run or overall finish time.