100 Meter Breaststroke for the First Time in Masters

As to the time before the meet, don’t over think it. Make sure you get enough sleep and otherwise try to follow your usual workout preparation and warmup. Eating the right food at the right time won’t make much difference, but eating junk or something you’re not used to could be a problem. As to strategy, hopefully you have been doing some race pace so you have a feel for what 100 pace is. It is not a sprint, it is a little slower. For me it is the difference between stroking AFAP in a sprint vs slight emphasis on the glide. If it is LCM it is important to get into a rhythm you can carry for 100M. Work on streamlining and DPS in warmup. Mostly focus on having fun and learning for next time. 

Regarding time, if you can swim a 39.8 50 you can probably go out in 42-43 and come back in 46-48 so you should be well under 1:40, probably under 1:30, but this is a learning experience and YMMV

Thanks for your input, Allen, but YMMV, indeed. The 100 was a bit of a bust. I went out too strong and just totally tightened up after the turn. I almost couldn't finish. I ended up doing 1:41.45 (which somehow was still first of three in my age category).  I did a full underwater push off and pull out and felt oxygen-starved after surfacing. I then started feeling it in my muscles and had to slow down to a snail's pace just to be able finish. 

I did 40.46 in the 50, which is about what I expected after a two-year gap in competitions (did 39.6 two weeks ago in SCM 50 non-sanctioned). Yesterday, a guy I beat by nearly a second in the 50 finished 9 seconds ahead of me in the 100. 

It was a learning experience. I need to train more specifically for the 100 and perhaps get on a real team (I've been training solo all this time). 

It could be your age. I swam a 1"43 sy 46 years old several years ago, and a 45 in the 50 once in lCm.

I don't think age is the issue for that much drop off between the first and second 50. Going out too fast leading to tightening up can happen at any age. It is a matter of pacing and practicing at race pace enough so that when you dive in your body knows what your 100 pace is.

This is off topic but I noticed that US Masters has not yet given your fellow Oregonian Collete Crabb the record in 65 to 69 in 200 yard breast. According to the date  based she did a 2"56, they still list the 200 yard breast  record to Charlotte Davis for 65 to 69 women at 2:58. They did give Collete Crabb the 100 yard record at 1;@0 for 65 to 69 year old's. Maybe, its taking them time to update the data base.

This is off topic but I noticed that US Masters has not yet given your fellow Oregonian Collete Crabb the record in 65 to 69 in 200 yard breast. According to the date  based she did a 2"56, they still list the 200 yard breast  record to Charlotte Davis for 65 to 69 women at 2:58. They did give Collete Crabb the 100 yard record at 1;@0 for 65 to 69 year old's. Maybe, its taking them time to update the data base.