How to run an 18:xx 5k as a woman?

With a 21:31 PR set during a half marathon, your current 5K fitness is probably a bit closer to that 18:xx goal than you might think. I'd suggest hopping into a 5K race (or just run a TT) this weekend, just to see where you're at.

From there, you can determine workout paces for your 5K training block. Here is a simple approach:

Mon/Tue/Thu/Fri easy 45 min

Wed warmup, 20 min tempo (use an online calculator to determine your tempo pace, based on your 5K run), 4-6 x 100-150m-ish accelerations ending with at least 40-60m at a full sprint

Sat warmup, track repeats at or slightly faster than *current* 5K pace. 4 week cycle: 12 x 400m with 1 min rest, 6 x 800m with 2 min rest, 3 x 1600m with 3 min rest. Then run another 5K on the 4th week and recalculate tempo & workout paces.

Sun rest / cross train / weights. Whatever makes sense, don't overdo it.

Just an idea, hope this helps. Have fun, keep us posted!

A 5k is different you will recover significantly faster. You may want to run a local race in a few weeks when you are sure your recovered. This will give you some baseline data and help you plan your workouts.
You can do the same kind of workouts but they should be faster and shorter over all distance. For example go 3min fast @130 recovery jog x7. Tempos for 4 miles Fartlek for 3-4 miles fast
Strides once a week become much more important.
Your easy days you can still do your regular training.
You should run a couple low key races races for experience. Relax and gain experience.
Eventually you may want to try some interval workouts. 4 x1200M @ 2 min rest 1x 200.

Stick with the 65mpw (or as close as you can manage).

Keep a threshold interval session in there once a week. Something like 5 x 6 mins @ 1 hour pace (60-90" recovery) or 3 x 10 mins (2' recovery).

Then for the other workout, do something 5k or 10k specific. Examples might be:

5k sessions -

12 x 400m at 5k pace (200m jog recovery)

6 x 800m at 5k pace (60-90" recovery)

5 x 1k @ 5k pace (90"-2' recovery)

10k sessions -

8 x 1k at 10k pace (60" recovery)

5 x 1 mile at 10k pace (2' recovery)

4 x 2 @ 10k pace (2-3' recovery)

Maybe just rotate between a 5k session one week and a 10k session the next. I include 10k workouts in there (despite 5k being your goal), because there's quite a bit of evidence coming through that higher volume workouts at 90% vo2 max are actually more effective at boosting vo2 max than lesser volume workouts at say 95% vo2 max.

Perhaps once you've adjusted to these workouts, you could include 4-5 x 200m repeats at mile pace at the end of your threshold intervals (once a week). This will give you a slightly better spread of intensities, and should help with running economy at race pace.

* 4 x 2k @ 10k pace (2 -3' recovery)

I should also mention to give yourself 6-8 weeks (at least) of this type of training. If so, you should get pretty close to your goal.

The other posters have already given advice.

I would just say that there are no magic workouts.

Try to run more consistently than you ever have. And make sure you are getting in 1-2 hard sessions per week. For a 5k you should be touching at least 2 paces below and 2 paces above.

So make you do workouts at mile, 3k, 5k, 10, half marathon. Alternate the workouts.

You don’t need to focus on long runs until your next marathon block.

I like these examples. I'm not sure you need that much volume of intensity. A sub 19 min 5k requires just a few sessions that raise your threshold and vo2max. Here are a few example sessions I would recommend taking into consideration if you can do 1 track session per week and 2 quality sessions per week.

Session 1 1k at threshold + 2x4x400 w/30 seconds rest 2min between sets + 4x200 w/1min rest + 1k threshold

Session 2 6x1k w/90 seconds rest + 5x30 seconds w/30 seconds rest

Session 3 10min threshold + 6-8x45 second Hill + 5 min threshold

Session 4 4x5min threshold + 5x100m

Good luck and let us know how it goes.

Just jog few times per week. Stop shoving chocolate down your throat doesn't hurt either. 18 is nothing.

No chance if you just ran a 3:18 marathon and you're a woman.

First goal should be to try and run 21:00 again.

Btw 5k and 10k pace workouts will leave you exhaused so ignore the previous advice.

This is a great start. Would recommend someone at your level just finding a good running club & hopping in their weekly workout. Train specifically for the 5k. Calendar out a few months & stick a goal 5k at the end of it. Focus on that race & forget about the half marathon & marathon for now. A lot of newer runners enter the sport & just start racing marathons. There's nothing wrong with that but then speed is rarely touched on & we avoid faster workouts that are less comfortable. You just need to have your 5k session be the main focus of your week. 2 workouts/week. Every 2 weeks do 2 5k workouts, 1 under distanced workout, & 1 threshold/tempo. Keep it simple. Focus on those sessions. Run super easy in between workouts. Do strides 2x/week. Shorten the long run just a touch. You don't have to go over 80-90min & can get away with 70-75. I would just find some people to run fast with every week or do that on your own. You just have to consistently do the workouts that you probably haven't been doing in your marathon builds.