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Speed vs. Watts: Understanding the True Measure of Cycling Performance

As an Ironman coach, I often encounter athletes fixated on their speed during cycling workouts both on the trainer and outside. While speed is an important metric, it doesn't always paint the full picture of an athlete's performance or effort. In contrast, power output, measured in watts, provides a much more accurate and consistent indicator of how hard an athlete is working. Understanding the difference between speed and watts can significantly enhance your training and racing strategies.


Speed: A Variable Metric

Speed, or how fast you are traveling on your bike, is influenced by a multitude of factors:

1.Terrain: Hills, descents, and flat roads all affect your speed differently.

2.Wind: Headwinds and tailwinds can drastically alter your speed, making it hard to gauge effort.

3.Road Surface: Smooth asphalt versus rough (think Texas chip seal), uneven surfaces can change your speed.

4.Drafting: Riding in a pack or drafting behind another cyclist reduces wind resistance, increasing your speed without a proportional increase in effort.

While speed can give you an idea of your performance, it’s heavily influenced by these external factors, making it an unreliable measure of your actual effort or fitness level.


a triathlete riding in the aero position
ironman training

Watts: A Consistent Measure of Effort

Watts on the other hand measure the power you are generating while cycling. This metric is far more reliable because it directly reflects the amount of work you are putting into the pedals, regardless of external conditions. Here’s why watts are a better indicator of your effort:

1.Independence from External Conditions: Unlike speed, watts are not affected by wind, terrain, or drafting. Whether you're climbing a hill, riding into a headwind, or on a smooth flat road, the power you generate remains a true representation of your effort.

2. Training Precision: Using a power meter allows for precise training. You can set specific power zones for different types of workouts, ensuring you train at the right intensity to achieve your goals, whether it's building endurance, increasing strength, or improving speed.

3.Race Strategy: In races, particularly long-distance events like Ironman, pacing is crucial. By monitoring your watts, you can avoid going out too hard too early, ensuring you conserve your energy for the latter parts of the race.


Practical Applications of Power Training

1.Setting Power Zones: By conducting a functional threshold power (FTP) test, you can determine your power zones. These zones help you train at the appropriate intensities, whether you're aiming for a high-intensity interval session or a steady endurance ride.

2.Monitoring Progress: Regularly tracking your power output allows you to see improvements in your fitness over time. As your FTP increases, you'll know you're getting stronger and more efficient.

3.Race Execution: During a race, you can use your power meter to stick to your planned power output, preventing the common mistake of going out too fast and hitting the wall.



While speed is a useful and easily understood metric, it’s not the most reliable measure of your effort or performance because of its susceptibility to external variables. Power, on the other hand, offers a more accurate and consistent indicator of how hard you are working. By incorporating power-based training into your regimen, you can train more effectively, monitor your progress with greater precision, and execute your race strategy with confidence.

Remember, in the world of cycling, watts don't lie. Embrace the power meter, and let it guide you to new heights in your triathlon performance. Whether you’re climbing a steep hill or cruising on a flat road, focusing on your power output will ensure you’re always working at the right intensity to achieve your goals.


Have you thought about hiring a coach for your next Iron distance event? Click the purple button below and fill out the short form for a free 15 minute chat with me about your race goals!


Mary Timoney

Ironman University Certified Coach

USA Triathlon Coach

TriDot Coach

ACSM Trainer


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