HeartRate zones vs. RPM's
 

I've been working out lately on an indoor spin cycle. As I've been training I've found that I can get into a 85%/90% zone at either a high RPM (110) with low resistance or the same zone at a low RPM (60) with high resistance...often times out of the saddle.

My question is what is the physical difference between those two extremes? I assume that from an aerobic/threshold point of view it doesn't really matter the RPM as long as the heart rate is at the right zone. Is it just a matter of excersising different muscle groups (or types..fast twitch/slow twitch)?

thanks

Your first statement is totally correct, you can have the same HR at low cadence and at high cadence in different gears. This is why I like to train with wattage and HR because I can see that I am putting out the same wattage in either situation.

In my personal training I notice that when I really mash the gears it takes a little more muscular endurance to push the higher gear and more aerobic work to spin the higher gear. It takes my HR sometime to end up adjusting to the difference (the typical HR delay). My HR goes up faster with spinning fast then pushing but over time the limits of the two come out around my LT...

It does matter which RPM range you train on, but you want to mix it all up. If you are doing strength intervals (hill repeats, etc), then a lower RPM pounding is going to be better than spinning at a higher RPM. If you are working aerobically then higher cadence seems to work better. My problem with low cadence work is that I tend to end up spinning up if not on a hill which justs makes me push my HR up more. You also need to watch for knee pain when mashing gears. In many situations tough (such as sprinting) you will use both, mashing out of the saddle and then sitting at high RPM.

I think when you're seated you pretty much use the same muscles regardless of cadence. When you stand you recruit a different set of muscles to help with the effort. I prefer to do my training at a higher cadence than mashing. I can mash when I have to but it puts added stress on my knees and I'd prefer not to do that. I've I'm going to mash I'll normally stand up as well since my cadence drops when standing compared to seated. If you feel comfortable riding both styles then continue to do so. Afterall it's a good thing to keep your body guessing :).

i don't think it matters too much for your HR, but pushing higher gears at lower RPM's will fatigue your muscles faster. Depends on what you are trying to do in the training, speed work, power work etc.

What climbo said. You're conditioning different things, both are useful! Pushing the big gear, under many circumstances, is faster. The downside is you can only do it so many times. Use it when you have to. Higher RPMs can be just as difficult in a different way, but you can do it over and over.

yeah, what I said !! :)