Weight training for improving biking?

Fred, do you have a link to the scientific studies?  I'm not arguing, I'd like to read about it. 

I found this link, but don't bash me if it doesn't apply.  I just googled for it as I heard from others that the amount of wattage necessary to pedal a bike for a short hard effort (less than 10 minutes) is comparable to how much power is required to walk up stairs.

http://www.letstalkscience.ca/hands-on-activities/mathematics/how-much-power-is-required-to-climb-a-flight-of-stairs.html

At my weight, it's around 400 watts to walk up stairs...that's an all out effort of maybe 2.5 minutes for me on the bike.  If I'm training for something like an Oly where I may target 240 watts for roughly an hour, then the power I need to train for is significantly less than what is required to walk up stairs. 

So I would ask myself the question.  If I already have the muscular strength to push more watts than I could ever imagine holding in a race by simply walking up stairs (not running, or running with a weight vest), then why would I think I need to increase the muscular strength in my legs?  Should I not be focusing on endurance so I can sustain the power I already have but hold it over a longer period of time?

Not to argue but I don't consider magazines and web sites like active.com to be 'respected sources'.  Yes they write articles but that doesn't mean the information in them has any actual scientific basis and is not just the authors interpretation of something he read elsewhere.

 Edited for spelling

Except that walking up one flight of stairs takes about 10 seconds and almost anyone can do it.....so in my mind it's absolutely not relevant. 

I'm not saying that weight training will help biking.....but I hear the same thing said about swimming, and baseball, and all kinds of sports.....but then I read interviews with top athletes who say that strength/weight training helped them immensely.

Again, I'm not arguing because I don't know.....but I'm very interested because my kid is getting to the age where we are talking about weight training, and I'm wading through the "knowledge".

Just curious what distance events you were/are training for?

This hits on something that should be discussed more when talking about cycling power:  gearing.

Are the cranks/chainrings/cassettes different on your bikes?  That could be one reason you do better on one bike than the other.

Power consists of 2 things:  Torque (strength) and speed (cadence)

Even if you've got a great Aerobic system, if you're limited in torque (not enough leg strength to spin the gears you have)  or limited in speed (can't spin the gears fast enough to make the required power) ... you're not going to be doing your best on the bike. 

Clearly, being stronger (without increasing your bodyweight) is almost always an advantage.  If you've got no torque available, your only option is to drop gears and try to "spin it out" when you encounter a climb or a headwind. There is a practical limit to cadence... if you have to drop too many gears to stay in your optimal "torque output range" ... you might not be able to increase cadence to match your previous power output.

It's also misleading to compare your average triathlete to the best cyclists in the world.   While the data shows "no correlation between strength and endurance" for these elite athletes... we also forget that they get to ride a different bike every day in their competitions, bikes that are dialed in EXACTLY to match the terrain, and the individual output of the rider. 

Your average "weekend warrior" probably doesn't have that luxury, and could likely benefit (at least a little) from increased strength to overcome the requisite "compromise design" of their equipment.

All this is NOT to say that one will gain bike speed just by weight training.  As they say in car racing: "There's no substitute for cubic inches"  We can say "There's no substitute for T.I.T.S"  I just think there's more potential for benefit from strength training (for your average triathlete) than is being indicated here.  JM2C, YMMV.

To address your question directly:  Over the past few months I've been exclusively weight training.  I'm "on a break" from triathlon for a while.  Actually, I was "on a break" from everything for a while, and decided to start lifting in order to restore some fitness.

I've been lifting weights roughly 3x a week since June.   I focus on 5 core exercises:  Squats, Bench Press, Overhead Press, Barbell Row and Deadlift.   The overall change in my body shape, and strength, has been fairly dramatic.  I would focus on fewer reps, higher weights if you want to build strength.   I don't know if you're doing isolation work or not, but I would dump it if you are.  Focus on compound movements that engage your entire core.  This will give you more "bang for your buck" in the time and intensity of your workouts, and leave you more time for tri training.

Finally, you won't "bulk up" unless you're eating a caloric excess, or if you've never really done any strength training before (some people experience "newbie gains" when they start lifting heavy weights)