which comes first cadence or power - or asked another way how are they related

I agree with Ben.  Let your cadence self-select.

There's a quote - "Cadence is a red herring" that rings true.

Definitely focus on power. Power is the output that makes you go. More of it makes you go faster.

Cadence is more in the application of the power. There will be a range you operate best in, and it's likely you'll gravitate towards that with more riding. Having said that, it is helpful to be able to produce power well at a good range of cadence. You can handle terrain changes and situations more easily and are more likely to find where you operate best at. This area can move as you develop.

So what to do with this? Your main focus is on power development. This trumps everything. Most of the time ride where it feels like you should. Spend *some* time off of that to help increase your range, but the focus is still more on how hard you're working.

When I get fatigued... I increase my cadence.  Maybe I'm just weird.

but yeah.  It's interesting to know and watch your cadence, but I agree with the "self select" point above.  I've always thought that having a wide range of cadence is generally a good thing.  Usually, my peak power is 87-93 rpm or so, which I think is typical, but there's nothing magical about those numbers.  I would think those with bigger/stronger legs might gravitate to a lower cadence, and those with small, scrawny legs will go higher.  Size of crank probably matters as well- but as I recall, doesn't have much effect on power output.

anyway- to answer your question.  Power is first.  Whatever cadence you can sustain power output the best, is where you want to be.  Generally, it comes naturally.

oh- this doesn't apply to running, where cadence affects form.

Yeah, I haven't really seen or experienced where higher cadence necessarily makes the run go faster. Sometimes I might feel better coming right off the bike, but that doesn't mean I'm going faster. I've been stuck at an early run pace when pedaling faster and have come on much stronger later in the run when pedaling slower. Riding at an appropriate level really dominates how the run goes.

This is not to say no one will run better with a higher cadence, but would put the reason being more towards them finding what's more appropriate for them as opposed to equating higher to better.

I've seen others increase as well, but tend to see more decrease. I like having a decent range available as well, and still understanding where I'm strongest. But also where I'm strongest for what type of efforts. A longer effort of 20' or more is not going to be the same for me as 1' or less. The short one will be higher. Possibly quite a bit higher. Terrain comes in as well. That same short one will be lower going up a hill vs in the flats.

I would try *not* thinking about any correlations such as the big/strong vs scrawny. That can get in the way of the self selected, feeling out what's most natural.

You say that you were working on keeping your cadence above 80? What cadence were you riding at before. Cadence isn't the be all, end all, but I think working to stay above 80 is probably a good idea.

Not exactly an answer to the question but cadence is a metric that can be easily and cheaply measured.  Power meters can be quite expensive.  On both you need to be willing to record the data and take some time to review it compare against your effort but to me at least cadence is a good check against my effort without breaking the bank on a power meter.  But a cadence sensor is quite cheap in comparison

All of the good cyclists I know can spin at a crazy high cadence if they want to.  I have no idea what that says about how you should or shouldn't ride.....but show me someone who can hit a really high cadence, like >150 , without bouncing all over the seat, and I'll show you someone who can also put down some serious power at a lower cadence....whatever they like to ride at.   

Riding at a high cadence is something worth practicing.....as is everything that increases cycling skills.

This article doesn't really get too in-depth, but does give some starter rationale for a few things that have come up recently. One of them is with being able to push a high cadence at times. I'm certainly with the self selected idea on average cadence, but also with being able to push well beyond that for some periods of time.