Off season triathlon training -- to run or to bike?

I've been asked about off season training for triathletes a few times in the last few weeks. A few athletes have come in after 4 and 5 hour rides, and when I asked them what races they had coming up, they rattled off either a half-iron or full sometime next summer.

How come the 5 hour rides now? -- "Doing some bigger builds to get stronger on the bike"

Okay, I can buy that. Plus, the weather has been incredible here, so I can understand wanting to get out on the bike more. My only hesitation is that these people are good cyclists -- not great, not headed to the Tour de France, but good solid bikers. They typically cover the 112 miles on the bike in 5:15-5:30 or so. And, like many triathletes, they are mediocre runners -- above 4 hours for the marathon leg.

So here's my hangup -- triathletes are always strapped for time, and need to make the best use of their training days, especially those of us who work and have families, etc.

If we really want to improve the most, how should we go about it? If we do a little simple math we can find the right thread to pull.

It doesn't take long in the sport of triathlon to understand that winning a triathlon because of a great swim is about as rare as, well, a triathlete eschewing a wetsuit voluntarily in a race. There's just not enough time to be made up in the swim. Which isn't to say that the off season isn't a great time to work on your swim form -- getting out of the water having wasted less energy than your opponents is a great way to start a race.

So that leaves the bike or the run. Which one holds the most potential for improvement? Well, that's going to depend on the athlete. But if we do a simple experiment, like taking the first 5 finishers in an age group for an ironman, and finishers number 70-75 in the same age group, and average their bike and run times. We can then take those times and compare bike and run to see if there is a more significant gap in one or the other.

I mined data from two separate Ironman races on two different ends of the globe. Race #1 is Ironman Western Australia, and race #2 is Ironman Cozumel.

Looking at the mens 30-34 age group I took the top 5 finishers times, and then the 70th through the 75th.

Here's what I found:

Ironman #1 the top five bike average was 4:45, run average was 3:13
finishers 70-75 bike average was 5:29, run average was 4:10.

Ironman #2 the top five bike average was 4:58, run average was 3:16
finishers 70-75 bike average was 5:37, run average was 4:10.

That means in race #1 the 70-75th places biked 15% slower, but ran 29% slower than the 1stthrough 5th finishers. A 44 minute difference in bike, but a 57 minute difference in run.

Race #2 they were 13% and 28% slower respectively. A 39 minute difference in bike, and a 54 minute difference in run.

It's clear that most people ride well enough, and the place to spend some time to improve on is in the run -- for most of us.

If we look further down the finishers list the disparity gets even larger. Looking at the same races, same age group, but now finishers 175-180 we find for race #1 that they were 35% slower on the bike (+101 minutes) and 81% slower on the run (+158 minutes), and in race #2 they were 38% slower on the bike (+114 minutes) and 70% slower on the run (137 minutes).

I will completely stipulate that many athletes merely need to spend more time just getting better aerobic efficiency overall, and the easiest and usually the least injury prone way to do that is to bike more, but this definitely shows some major gaps in running efficiency.

If you're new to triathlons and you can run a sub 2:45 stand alone marathon, then you're probably fine biking a bunch this off season. If not, then this might be a good time to bring down that marathon time and work on your running efficiency.