Using Power and Heart Rate to Race Smarter

After racing for many years across full Ironman races, 70.3s, and marathons, one lesson stands out more than any other. We are all human. We start races with the best intentions, but emotions can take over and push us into decisions that hurt us later in the day.

Power and heart rate have been two of the most valuable tools

That’s where technology becomes your ally. Power and heart rate have been two of the most valuable tools in my own racing. Power tells you what you are doing in real time. Heart rate tells you how your body is responding to that effort. Used together, they keep you grounded and honest. Power alone is not enough. Some days your body simply cannot deliver what your mind wants. Heat, travel, stress, lack of sleep, caffeine, and nerves all show up in heart rate. Ignoring those signals and chasing a power number can put you in a hole fast. This is why I strongly encourage athletes to watch both power and heart rate on the bike. On the run, that becomes pace and heart rate. One sets the target. The other confirms whether that target makes sense on that day. Heart rate is highly individual. Genetics matter. Sleep quality matters. Caffeine intake matters. Stress matters. That variability is exactly why you should train with heart rate regularly. Over time, you learn how your body responds and what is normal for you.

Race-Day Targets

Since Kickr Lab cycling workouts are centered around power, it helps to understand realistic race-day targets. These are common ranges most athletes fall into. They are guidelines, not rules. Elite athletes may push slightly higher.

Sprint triathlon bike
90 to 100 percent of FTP

Olympic triathlon bike
85 to 90 percent of FTP

70.3 bike
75 to 85 percent of FTP

Ironman bike
60 to 73 percent of FTP

Pacing

On the run, the same principle applies. Pace gives you direction. Heart rate tells you whether that pace is sustainable today. This leads to the most overlooked skill in endurance racing. Pacing. Start too fast, and you will pay for it later, usually, with walking. Start too conservatively, and you leave fitness unused. Most athletes start too fast. Adrenaline is high. The crowd is loud. Caffeine is flowing. That is why we train with power and heart rate, especially during long workouts.

Every 30 minutes, check in with yourself. Look at your heart rate. Ask how the effort feels. Ask whether you could truly hold that pace or power, or even go slightly faster, for the duration of your race. Those small, repeated check-ins build discipline. Discipline is what turns fitness into results.

Train smart. Race smart.

Coach Duckworth