Pacing is critical for your Ironman performance and it's fair to say, you can't predict how well your racing is going to do end until 13 miles in the marathon. How you ride the cycle section will determine whether you run or walk the marathon so it's critical that you get it right. If you ride too hard you will burn too much carbohydrate, lose too much fluid and your nutrition plan will have minimal impact. The issue with riding too hard on the bike is that the effort required to go faster is exponential. By that, I mean that riding 17mph might be comfortable, but to increase to 17.5 and certainly to 18mph requires a significantly higher level of effort and moves you from 'comfortable' to 'hard'. The gain from the extra half a mile an hour might be 10 minutes at best, which is a small amount to gain for such an increase in effort. If you're struggling on the marathon and start to walk, that 10 minutes will disappear within the blink of an eye...
Why do people go too hard on the bike?
People go hard on the bike for several reasons. The main one is that you're fresh as it's the start of the event. Let's face it, not many people go 'too hard' in the final miles of the marathon as you're too knackered to do anything 'too hard'. If you're fresh, it feels easier, so you ride faster than you should. The adrenaline doesn't help, coupled with the fact that most of the other people can't pace themselves either, so they're flying past you making you feel uneasy about the whole thing! It takes a brave person to hold their pace and ignore everyone else... if you think it's mentally tough to keep going when you're tired, consider how tough you have to be to hold your pace when everyone else is disappearing into the distance.
Biking is macho...
Is it me or has biking become the macho discipline of triathlon? Certainly amongst guys, the real pride is in the bike split... what was your power??? What was the split??? How strong are your quads??? Are you an UBER biker??? If you read the KONA reviews, or any other Ironman, there is definitely a bias towards the bike split and bike course records, but run times have progressed little over the last 10 years. I know plenty of people who have ridden 5:30 bike splits and then ran 4:30 or slower as a consequence, only to talk repeatedly about their bike split for the next 12 months. There are 3 disciplines, treat them equally.
Pacing on the bike is simple. You should ride at a pace which allows you to climb off at 112 miles and feel like you can run the marathon. If you feel drained after an 80 mile ride, then you're riding too hard. You can use your own judgement or you can use a heart rate monitor to help your pacing, but the 3 critical things are:
1. Riding at the correct intensity (not too hard)
2. Riding a consistent intensity (avoid spikes and dips, keep the intensity even)
3. Ignore everyone else
For the run, the same applies. If you have a GPS you should definitely check your pace for the first 10 miles. 85% of the field set off at a faster pace that they can sustain for the full run. Decide your target pace for the full marathon, work out the pace per mile/km and stick to it from the start. You'll appreciate it during the second half of the marathon.
Good luck on Sunday folks
But if you pace it right... you shouldn't need any luck ;)
The Endurance Store