Which of the 3 sports is best for building your endurance base?

What he said...biking is much kinder to your body for long workouts.

 Agreed...  I'm also searching through the slowtwitch forums to find a great response about this same question.  No luck yet. 

But isn't it also true that by having a strong bike base, it will allow you to stay at FoP pace while also conserving energy and have better times during your run (think bricks or race enviroment, not stand alone runs).  I've always been under the impression that strong bikers come off the bike and into the run in much better shape than a strong runner would (again, think race environment).

Tell that to all the people doing ultramarathons.

ALL 3 sports are important because specific training adaptations occur on each and specific fitness doesn't really translate from one to the other. 'Building a base' is one of those terms a lot of athletes/coaches use but not everyone understands what is it or depending who you ask you'll get a different definition. Base training is nothing more than laying down your general fitness foundation to handle the specific training load in the future.

General fitness refers to the intensity and volume (training load) which is not particular to your main event. Specific fitness refers to the intensity and volume directly related to your main event aka as race pace. i.e. someone training for an IM could work on tempo/threshold training (intensity) for shorter periods (volume) and focus a bit more on specific weaknesses early on the season and as the season progresses then the focus will switch from general to specific training in which tempo/threshold sessions will be reduced and longer steady pace sessions (race pace) will become more important.

Aerobic base is another one of those terms that I feel confuses people. 1 hr going all out (threshold pace) or 5 hrs riding at easy/steady pace are both aerobic efforts because our body relies on the aerobic energy system to fuel the effort. Hence IMO intensity or duration doesn’t dictate base training, as I said above your specific goal and needs will.

Honestly I don't think there is a right answer here.  I was in great shape in high school as a competitive swimmer, and I had endless energy.  All the swimming translated into great aerobic fitness which allowed me to run competitively in a 5k with almost no running at all at under 7 minute miles.  However, there comes a point where muscle fitness overcomes aerobic fitness and your muscles just can't take it.  I tried to run a 10k at the same pace and bonked at about mile 5, still finishing at about 7:45 miles, but it was hard and my legs were a bit sore after that.  11+ years later and I wish i had that aerobic fitness back, but I am working toward it.  I would say this "muscle vs aerobic" phenomenon will apply to all 3 sports, with running/cycling being more closely related, but if you exceed your muscle fitness in the sport, it won't matter what your aerobic fitness is. 

In my opinion, I think running is the best one to focus on during the winter, and my reasoning is that it is dangerous to ramp up your running when you haven't been doing it for a long time, which is unlike swimming and cycling, which are much less injury prone.  So by building a great aerobic base in running, this will translate more smoothly once you begin to hit the other sports hard come spring (or whatever), and you can ramp those up a lot faster with less risk for injury.  I would still definitely recommend, however, cross training in the pool 2-3 times a week (or something not involving your legs), which helps tremendously for recovery and still works your aerobic base while your legs take a break.  This is just my opinion.

I believe Bryan is talking day in, day out.  Even ultra runners do not train 3 - 5 hours a day continuous.  You can do that on the bike once you've built up to it.  (Assuming you have no other obligations like a job or a family).

I happen to agree with him .......

Good thread.

I heard a coach say last week that the better runner you become , it will help your cycling and not vice versa, but in regards to the swim , as everyone said: "you got to get your feet wet".

x2 

I'm at an age (55), where wear & tear and recovery times are becoming ever bigger factors in my training.  I can do long rides on consecutive days, but my knees need a day off if I run for three miles or more.

Since my primary training objective is general health & fitness, versus race performance, I'm not overly concerned with intensity or specificity of training unless I'm approaching a race.

Mark

I got into triathlons in July 2008.... when i started getting into shape i would rollerblade to school every day at top speed....i would notice differences to my lactic threshold...then i got into biking till i was dead...that got me into great shape!! ohh yeah and cross country skiing is awesome for VO2 max inceasements, and base building!!

But since i knew i had to swim and run in my first triathlon, i started working on those 2 months before my first race!! I did very well. But before all of that i would do strength training on my entire body....by luck.... because i was pretty weak, and this prevented me from injury over the next months of aerobic training.

So i say do whatever you want, and try not to injure yourself, but biking, skiing, and rollerblading are all awesome!! you can go forever and not deal with friiiiikin cramps!! (running and cramps go together when you push hard!)

I think we are missing a HUGE issue here.

'Aerobic Base' is not some aqueous thing that resides in our bodies.

Aerobic base is not determined by oxygen intake (Ie the lungs and heart) but rather by oxygen utilization.  When you sprint as hard as you can, you are getting enough oxygen in your blood stream (otherwise your brain would be complaining as well...aka passing out), your muscles just can't absorb it fast enough.  When the energy demand on a muscle exceeds what it can produce aerobically, the anaerobic pathway is fired up, leading to increased lactate production, and on and on and on.   That's actually a pretty dumbed down explanation, but it works for this.