By Coach Tim Snow
Most IRONMAN marathons follow a familiar shape. The early miles feel easy, the pace slips in the back half, and heart rate creeps up while the legs slow down. At this past weekend's IRONMAN California, one of my athletes, Andrew Cruz, ran just the opposite shape. He got faster in each section of the run while his heart rate barely moved. His marathon time was an age group's best 3:19:19 (7:36/mile), good enough for 3rd in the M45-49 age group, following a solid swim/bike combo.
It wasn't luck, and it wasn't a day when everything simply felt great. It was a plan, built well in advance and carried out with discipline. Here's what the plan asked for, what he did, and why the data shows it went so well.
The plan: judge the day on execution
The race plan said the day would be judged on execution. Everything was built to set up his strength, the run. In the plan's words, "the run is where the magic happens," and the bike's job was to make that possible.
The key word was patience. His race would be defined by the back half of the marathon (miles 13-26), not the early miles of the bike. Over the back half, he'd be "collecting what everyone else would be giving back."
The run targets were deliberately wide, with room for his own judgment inside them:
- Pace: a primary range of 7:10-7:50 per mile.
- Run power (measured with STRYD): a primary range of 260-285 watts (W), used as a check against overcooking it.
- Start the first few miles at the slow end, then ratchet up as he felt better.
- Take the limits off for the final 10K, once he'd earned it.
Wide bands matter. A slower mile is never a failure or the start of a cascade. It's just a mile inside the plan.
There was mental work, too. The plan guarded against expecting to feel "phenomenal" all day. When a stretch felt less than great, he'd use the easy end of the range, which would let him come back to the harder end later.
Finally, he was taught The Three Sections: three overlapping windows of the run that each need their own focus: miles 0-13.1, miles 13.1-26.2, and the "middle middle," miles 6.5-19.5.
What happened
Heart rate: flat all day
Graphic 1 shows the whole run. The red line is heart rate (HR). Every mile averaged between 132 and 138 beats per minute (bpm). The highest was mile 21, at 138, the first mile after the limits came off. After a 112-mile bike, his HR held flat for 26.2 miles.
The blue line is pace, and it bounces more. That's expected: most of the mile-to-mile swing comes from aid stations. Pace stayed in or near the 7:10-7:50 plan range all day: a few miles drift a few seconds past 7:50, and mile 21 is faster than 7:10. Look at the start, too. Miles 1 and 2 were 7:46 and 7:52, at or just outside the slow end of the range, exactly as planned. From there he ratcheted up.
Power: 25 of 26 miles inside the plan
Because aid stations distort pace, power is the cleanest picture of how steady his effort was. Graphic 2 shows 25 of 26 miles inside the 260-285 W plan. The one exception was mile 21: 295 W at 7:02 per mile, his fastest mile of the day. That wasn't a mistake. It was the plan working. He'd remained patient for 20 miles so he could do exactly that.
Faster in every section, with no real rise in HR
Graphic 3 splits the run at the edges of the middle middle:
- Miles 0-6.5: 7:43 per mile, 266 W, 134 bpm
- Miles 6.5-19.5: 7:34 per mile, 272 W, 134 bpm
- Miles 19.5-26.2: 7:32 per mile, 275 W, 135 bpm
Each section was faster, and his power rose a little each time, while his average HR moved by one beat. The last section held the final 10K, the hardest running of his day.
Three halves, each a bit faster
Graphic 4 looks at the run through The Three Sections, as three 13.1-mile windows worked out from mile splits:
- First half: 7:38 per mile (1:40:10), 270 W, 135 bpm
- Middle half (the middle middle): 7:34 per mile (1:39:15), 272 W, 134 bpm
- Second half: 7:33 per mile (1:39:08), 273 W, 134 bpm
That's a negative split: Andrew ran the second 13.1-mile window about a minute faster than the first. IRONMAN marathons usually aren't negative splits. This one came from patience early, not from forcing it late.
Why this is so good
In an IRONMAN marathon, most people slow down while their HR creeps up. That's true, but something worse often happens later: the pace keeps slowing and the HR drops with it. At QT2, we call this "system failure." It's usually the legs that fail, not the heart and lungs, and they fail so badly they can't drive the HR up anymore. The runner can't go any faster, even with HR well below their lowest training zone. Both can happen in one race: early on, HR rises at a slower pace as the cost of running those paces increases; later, the cost becomes too much and the system breaks. (More in our post System Failure.)
Andrew's data shows neither. His HR stayed flat at 132-138 bpm while his pace held steady, then got faster. That's the signature of an athlete who paced the bike and the early run with patience, fueled well, and arrived at the back half with plenty left to give.
It wasn't easy, either. He rated the run a 9 for rating of perceived exertion (RPE) and called it "Very Strong." Good execution doesn't mean the day feels effortless. It means the hard part comes where you planned it. We all know how an IRONMAN marathon works. You can hurt in the middle, or you can hurt at the end. But you're going to hurt. You can be patient and slow in the opening miles, or frustrated and slow in the later miles. But you are going to, at some point, be slower than you would like to be. The "when" is the choice.
The scorecard, against the plan:
- Patience early: miles 1-2 at or just outside the slow end of the pace range, then a steady ratchet up.
- Power in range: 25 of 26 miles inside 260-285 W. Pace stayed in or near its range.
- Flat HR: 132-138 bpm, every mile.
- Faster every section: 7:43, then 7:34, then 7:32 per mile.
- A negative split: 7:38 per mile over the first 13.1-mile window, 7:33 over the second (1:40:10, then 1:39:08).
- The final 10K: limits off, and his fastest mile of the day, mile 21.
The long runway behind it
Race day was the last step of a long build. He started coaching with me in November 2025, with IRONMAN California as his A race. That runway gave us time to build toward one day, without rushing.
He also followed our StressLogic Framework religiously. StressLogic is QT2's framework for setting your weekly bike and run Training Stress Score (TSS). Each week gets one of five calls: Big Push, Small Push, Hold, Small Pull Back or Big Pull Back. Swim isn't part of it. (For more, read our post on your weekly training load.) Following those calls week after week, the pull-back weeks as much as the push weeks, is less exciting than any single workout, but it's also how a run like this one is built.
A full life, and a great IRONMAN
Andrew is a busy father of two young children with a demanding corporate job. He didn't turn his life upside down to race IRONMAN well. He had a long runway, a plan that fit his life, and the discipline to follow the StressLogic Framework in training and his race plan on the day.
Andrew's race shows it is possible to race IRONMAN very well, and qualify for Kona, within a well-balanced life that doesn't constantly push you to the edge of fatigue and constantly overdraw on your overall life-stress budget. (More on coaching built around a busy life.)
Quick answers
How did Andrew pace his IRONMAN California marathon?
He started at or just outside the slow end of a deliberately wide 7:10-7:50 per mile plan, then ratcheted up. He ran 3:19:19 (7:36 per mile) and finished 3rd in M45-49, grabbing a Kona slot along the way. Every mile averaged 132-138 bpm, each section was faster (7:43, 7:34, then 7:32 per mile), and 25 of 26 miles were inside his 260-285 W run power plan.
What is system failure in an IRONMAN marathon?
At QT2, system failure is when the pace keeps slowing and heart rate drops with it. It's usually the legs that fail, not the heart and lungs, and they fail so badly they can't drive heart rate up anymore, so the runner can't go faster even with heart rate well below their lowest training zone.
Why does a flat heart rate with a faster pace matter in an IRONMAN marathon?
Most people slow down in an IRONMAN marathon while their heart rate creeps up. Holding heart rate flat while getting faster is the signature of an athlete who paced the bike and the early run with patience, fueled well, and arrived at the back half with plenty left to give.
Want a plan built around your life?
With 1-1 Coaching, your QT2 coach uses Critical Power and Critical Speed testing to set your intensities, and StressLogic to decide how much training stress to apply each week, around the life you already have. Training for a full IRONMAN? See IRONMAN coaching.
Not sure which service fits? Take the Services Quiz
Or start a 1-1 coaching inquiry
