How much can I still gain in fitness?

I think there is still time to make some gains - both in fitness and in confidence. A week should be plenty of time to allow for positive adaptation to the training, as long as you don't push yourself so hard that you struggle to recover in the intervening week. Better to avoid doing too much more than you've been doing lately.

The two-week taper is more in order in a situation where somebody has a huge IM-like quantity of training to recover from.

If you're sure you'll finish - then no. 

None of the training you do will result in any significant gains for what you're trying to accomplish.  A week out - either you're going to finish at your goal or you're not.

Just try as hard as you can, go out and race your race.  Chances are, you'll surprise yourself.  Worst case scenario, the result will motivate you to train harder to reach goal at your next race.

My perspective as a lousy swimmer who's struggling to become MOP is that swimming 3 to 4 times a week in the week or two before the race can have a HUGE impact. I agree that fitness gains are not going to happen, but my swim limiter is not fitness, its technique. I have not had enough swim time to engrain good technique into my muscle memory. As a result, if I have not been swimming much, it takes me some time in the pool to get BOP to MOP technique. If I just show up on race day I'll be back of the pack. If I swim 4 or 5 times in the week or two before the race, I'll be MOP.

I don't see the same relative improvements from biking or running. If it were me, I'd swim my little heart out, bike good and hard this wekend, but take it easy with the running.

I feel the need to disagree here with the view that fitness gains can't be had in a short period. Fitness gains are the adaptations that happen during recovery from training. So if you can recover in time, then you can gain fitness in time. Perhaps not a whole lot, but enough to make some difference. 

(Please somebody jump in to correct me here if I'm wrong about the coupling of recovery and adaptations.)

I agree.  It just depends on the individual how well they recover from specific workouts.

I agree with you - really my question is what is the length of that period?  Is a week too short?  Frankly I think I will gain the most from biking and running at this point (swimming for years and nothing much changes).    I know I would need Carnac to tell me if I could recover in time, but there must be some guidelines.  

This is what I was thinking.  For me, racing is such a mental game.  My mindset has an impact on my performance just as my physical preparedness does.  If you *feel* just a bit more prepared, that can make the difference to go just a bit faster.

I think they can be had too, but it's more question if they're that detectable over this short of a time period for someone who has been active at least pretty regular for some time. Above I said to go ahead and do stuff this weekend, but be mindful of how much and how hard it is. There is the balance of recovering enough to do a solid workout again, and there is the intent of the taper to have the bit of a boost for race day.

I have a HIM that same day and am planning some things this weekend too, like 10 mile TT Sat, a 60 mile or so ride on Sunday, some swimming & med-long run Monday. I know I'll recover well from those and get that boost for race day in the last few days before the race of doing virtually nothing. Now if I went for a century ride all 3 days or tried to do a 2.5-3 hr long run this weekend, I could recover to go hard again by next weekend, but I wouldn't have the race I'd like. That's where I'd need to be careful of "cramming" for a race. And I know about where this is from watching all the training I've been doing the last few years. For bikergrrrrl, it's the same idea, but maybe different limitations on the volume & intensity.

I'm also thinking longer term and how much working out I'd miss if I did a drawn out taper like most do. Not every race has to be optimized perfectly.

The guidelines are pretty much individual.

The Oly I did this past weekend...I rode 70 and ran 16 the weekend before, and didn't start my taper till the Thursday before the race.  I was pretty much recovered when I toed the line on Sunday...YMMV.

Okay, thanks!    It sounds like if I feel recovered, I might have gained something, so it's worthwhile (within reason).   I do have a fairly good idea of my time for recovery - I didn't know for sure if feeling recovered would mean I'd done myself any good.  I swear, I am smart in other things but training is a bit of a mystery to me.

I am going to do two more longer rides (Friday and one weekend day) and make sure to get my runs in plus at least one OWS.    I feel like my best bet is to get my bike fitness as "in shape" as I can manage.    I'll still go full taper next week and fortunately the race is on Sunday.   My best half marathons have been on a two week taper, which is why I am nervous.  I just take a bit more time to feel better.

you've got 10 days.  That's about the minimum for adaptation to take place.

So- it's taper time.   don't do anything stupid between now and then.

 good luck, have fun.

Well, even if you don't see actual "adaptations" by Sunday, you should see some benefit later down the road...which isn't a bad thing.  It doesn't sound like you're trying to qualify for the Olympics or anything next Sunday, so I would say train hard, rest up, race, and have fun.  Don't sweat the details.

Raceday Apollo provides some graphs that show the benefit of a workout X days out. So it shows you get maximum benefit say 15 days out, less and less as you get closer and negative benefit 5 days out and less. In fact it's 4 for the swim and 5 for run and bike.

Of course it's different for everyone and if you use the S/W and test a lot it's supposed to adapt to you.

But out of the box, for the normal person, less than 4-5 days out a  workout has negative effect.

Skiba is a pretty smart guy and I would believe this to be true.

You have time for one more build cycle in the next 3 weeks then it is just maintain until race day.  Workouts done less than 2 weeks prior to the race won't build your performance for the race, but you will maintain your fitness during those two weeks. 

What you don't want to do is build more than is reasonable in that time (not more than 1 mile per week build on your long run, etc. ). 

If your not confident in this race, why not just train through it and schedule another race down the road?  You may not be able to gain fitness before this race, but you can gain fitness for a race a month down the road.

Ok, so this is pushing a bit beyond the OP's query (simple answer: brigby's advice is very sensible). But I'm genuinely curious about the basis for claims like these:

If adaptation happens during recovery, and if most recovery happens in the few days after a workout, why should there be a need for a longer lag between training and adaptations? Of course, a really heavy training load, such as peak IM training, can take a couple of weeks to recover from. And elite athletes who are pushing themselves to the limit might take a while to fully recover from their peak training. But those extreme cases are not what we're looking at here. 

Most of us have probably had the experience of trying out some new activity. And then trying it again a (very) few days later and finding that we have improved at that activity. Doesn't that show that workouts can have rather rapid effects?

yes and no.  depends on how much you plan on doing relative to your training base till now. I'd say be reasonable with your mileage plans. At this point, you may improve a bit on speed, but I highly doubt it will help your endurance. Definitely wouldn't blow yourself out with a heavy workout. Shorter speed intervals would be a better idea.

As for my thoughts on tapering, I think it's usually overdone, still necessary, but perhaps not as drastic as many make it out to be. Certainly plan on getting good rest on those legs following your last weekend...