Just finished a 13-mile time trial (closed loop, no stops, slight headwind disadvantage due to sheltered parts of loop) with the goal of estimating how hard and fast I could/should go in the bike leg (13mi.) of an upcoming sprint triathlon. I wanted to push hard, but not enough to destroy a 5K run that would follow. The effort came while well-rested, hydrated, uninjured, mostly optimal conditions. Here’s what I came up with:
Average speed: 22.3mph (hold your laughter until the end, please.)
Average HR: 168
Max HR: 174
(Maximum HR ever recorded while running: 201 - no accurate cycling equivelant performed)
Average of percentage of MHR: 84%
Subjective analysis: 80% (160bpm) felt too easy, >85% (>170bpm) felt like a compromised run would likely follow. 83-85% MHR (165-170bpm) felt ideal for maximizing effort on the bike for this distance without compromising a solid run.
Does this sound about right, based on your n=1 experience?
It depends on your cycling background, and your current cycling fitness. For a 13 mile ride, I can ignore the HR and just go full blast, sprinting out of the corners, without having a compromised run. But, I train for HIM so a 13 mile ride seems relatively short. If your training is based on shorter rides, then you likely cannot just go full throttle for the whole way.
It sounds like the way you have determined what is right for you is a reasonable method, so I would go with that.
Cycling background is weak, historically and currently. I ride 2, maybe 3x per week, never longer than 30 miles at a stretch. One hard, one medium, one longer/easier ride. My run fitness is the best of the three (hope to run 18:XX after the ride).
My concern was about diminishing returns. I’ve heard time and time again that X time gained on the bike equals X+ lost on the run when pushing too hard, so I’m just wondering where that line is, roughly.
Being it’s a sprint, is it reasonable to ride like there’s no run to follow, and hope your run fitness will carry the day, or will running like hell on shot legs produce a net loss in overall time than running like hell on tired legs? Too many variables to answer with any reasonable accuracy, I suppose.
Agreed… It is a personal issue that only you can determine, and it will change with yoru relative fitness.
What I would do if I was you (and I do this regularly) is to run a short distance after the time trial at what you would like your race pace to be. So for you, maybe run 1-1.5 miles. Gauge how it feels. Could you hold it until 5K? What is your HR like? Is it around where you would expect for the pace, or is it much higher? If much higher, then you are likely not going to hold pace as long as you would expect. In which case, repeat until you find that point on the bike that lets you keep your run speed up.
There is definitely a point at which there are marginal gains on the bike that lead to huge losses on the run, so you do need to figure this out. The best approach when new is to go conservative on the bike, ramping up in intensity with each race or hard training effort, until you find that point where it breaks your run.
Trial and error helps a bit, but I find that if I try to regulate my bike speed for short efforts then there is always a net loss for the entire bike/run time trial. When I ditched the heart rate monitor for short efforts and went all out on the bike, I found that I gain 1-2 minutes on the ride and lost 30 seconds on the run. That seems to be consistent for me over the last four years for efforts in the 20K/5K range. Basically it is the positive vs. negative split argument. Most people just can go faster at shorter efforts using negative splits, so you hammer hard and then hang on. This changes when you jump up past about 90 minutes—at least for me—and I have to relax a little more on the bike.
Chad