Have you ever done successful crash training?

Have you been running for a while but want to get in decent shape for a race? By short, do you mean 5-7 weeks? If so, then yes, it's possible. (The method: make a big jump in weekly mileage, plan in 3 key workouts with a progression in pace/distance between them, add in a few moderate support workouts, leave time to taper, and hope you don't get inured.)

If you haven't run before and have 1 week before a 5K that you just have to beat your brother-in-law in, then no.

Only one outcome from crash training.

I wouldn't make it out of the first week

The CNS effects of training come very quickly, within hours. So running specific drills can be efffective in a very short time.

Intramuscular energy stores start to increase after just a few days of running, so this can be a quick impact of training.

Mental benefits may allow you to push a bit harder after only a handful of runs.

Improvements to VO2max begin within a week or two of training.

So what you should do if your goal is to improve in a very short period of time depends on the period of time. But the takeaway is there "crash" training is possible. There is certainly no substitute to long term consistent work for any meaningful improvement, though.

I had to do some digging, but this is my experience from 6 years ago with "crash" training for a sub 2 minute 800. It was more compressed than crash in nature. Here's the meat and potatoes of what I did:

Follow up:

I decided to not crash train, instead running a couple of really hard workouts and then backing off for my race. Here are the workouts I did and the end result:

5/2: 45 minutes & strides

5/3: 800, 600, 400, 300, 200 in 2:17 (5min) 1:30.9 (6min) 61 (4 min) 45 (3 min) 29

5/4: 30 minutes easy

5/5: 17:45 5k (2 seconds off pr) 8 miles for the day

5/6: 600, 90 seconds rest, 200 in 1:28.5, 29.3. (pb for the 600 btw) then 4x200 in 30,29,29,30.

5/7: 3x300 in 45,44,44 w/ 5 minutes rest

5/8: 30 minutes w/ 6 strides

5/9: 4x200 in 28,27,28,27.

5/10: 30 minutes w/ 6 strides

5/11: 1:59 800

I have done it several times and even ran an 800 and 600 PR in my mid 20s after one week of running after a year lay-off.

Ran for one week and ran a 2:04 800 and then came back the following weekend with a 1:27 600.

I was in very good physical shape, I just wasn't running.

Yes. How long of a period do you have to train? How much have you been running? What is your goal?

Once, I ramped up too quickly to 100 miles/week for NCAA cross country. I was hurt a lot that season and under-performed in all but one of the regular season races. I finally got myself healthy by conference and ran some PRs in the postseason meets. Workouts were mostly hard intervals and tempos, with recovery days spent swimming in the pool. Averaged 40--45 miles a week that fall. Had to do a ton of strengthening work all fall because I had run so little over the summer that my muscles were weak.

Once in my mid-30s, I had been running 40-50 miles per week all winter when I decided I wanted to do an ultra that spring. I had run 1:18 for a half on a hilly course, so I was in ok but not great shape. Ran between 70 and 90 miles for the next 3 weeks, tapered for 2 weeks, then had a great race going until I got lost. Was in third place at 40ish miles against a national-caliber field when I took a wrong turn, but the fitness was there. I've always been a lot better on the trails than the roads. though.

If you're talking about a 5000 or something, I'd just focus on 200s one day, 800s or 1000s another day, maybe one or two sessions of mile repeats, and take the easy days really easy. I wouldn't go farther than 10 miles for a while. Oh, and do doubles as often as you can. Even 2 miles at a time will help. You can get into shape quickly that way, but obviously it isn't the best for your long-term development. Good luck!

I had agreed to a run about 20 miles of a multi-day relay, but didn't run for a couple of months prior. Two weeks out I just started running 7 miles per day, no rest days. I did fine.