Why doesnt running do shorter/faster reps with very short rest like swimming

Lactic Tolerance requires LONG recoveries. Short recoveries are Lactic Buffering. examples for 800m would be 6x300m (6minutes recovery), as done by Keely Hodgkinson. Marco Arop does 3-4 x 400m in 49sec with 5-6minutes recovery.

Buffering workouts are different, and could also include simulations and/or float recoveries, like 3x200m (100m float recovery) - total 800m, or 4x200m with 30seconds (or less) recovery.

Most sprinters are sprinters. The longer swims like 1500 are not very popular. Swimming also beats up the body much less than running. A few sprints is all that a runner can take, yet swimmers can train 5 hours a day.

Coaches asked themselves this exact question. They decided it must work better and then began the legendary American running era of the 90s.

High volume training was never a trademark of the 90s. Things like 25x400/30-45s rest is much more of a 2024 workout. You see a lot of it with the double threshold crowd

Emiel Puttemans used to do a session of 50m sprinting, 50m slow and apparently ran 8:00 for 3000m of that session.

Yes the fact that it is non weight bearing, and being in the horizontal position means that it's much harder to get the heart rate up as high as you do in running for comparable intensities (% of race pace). Elite swimmers will often have hard back to back to back days (many have hard doubles). You just can't do that in running. The pounding of running breaks down the body more than swimming....just have to be careful with shoulders in swimming. It's a great cross training sport to improve aerobic endurance without the physical stress on the body from running (especially for runners that are injury prone).

This would be closest to a tempo workout (in the sprint sense of the word, not the distance sense). For example, a 60 second 400 runner might run 2 sets of 10x100 with 30 sec rep rest and a couple mins set rest in 17-18 seconds. It's aerobic development, but using running mechanics that are closer to sprinting. I've used this stuff successfully in the place of easy runs for relatively fast girls who can't shake shin splints no matter what we do.

Because the demands more from the cardiovascular system and running has impact.

swimming has higher cardio demands than running but running you have impact.

Short intervals with short rest is a great way to build aerobic capacity in the intermediate fibers. I think the key is keeping them relaxed (e.g., 3k-LT EFFORT)! The short interval keeps lactate from getting too high, and the short rest prevents the anaerobic system from fully recovering throughout the session. Therefore, you train to run faster speeds at lower lactate levels as long as you refrain from hammering them :)

Elite runners probably do them more often than you would think. They are just not the "sexy" workouts you hear about close to a national/world record performance!

Gretchen Walsh in a nutshell.

Who does 25x400m on 30s rest? Nonsense. Runners do short intervals in time but rarely with such short rest. One workout they actually do is 20/10s for 2x5 minutes, meaning 'sprint' for 20 seconds, jog for 10. That was used by exercise scientists and they said doing that 2-3 times per week resulted in better aerobic and anaerobic gains than just running an easy 45 minutes per day. I tried it a bunch of times and it seems like a good workout as you're trying to get back into shape. Obviously, the quality of the sprints isn't the greatest. The pool workouts of 50-200m, however, would take roughly 25-45s on up to 2 to 4 minutes, per interval, depending on the quality of the swimmer, and you would see lots of runners doing intervals for those times from 150s on up to 1200s, but with at least 45 seconds rest and more typically 1-2 min. The runners would not repeat such intervals every day like a lot of swimmers because the swimmers are doing a low impact exercise in water and runners would get injured trying that. Probably the closest real analogue was Jim Ryun's training, because his coach Timmons came over from swimming to track and brought the workouts. So, he gave him tons and tons of reps on relatively short rest every day. The pace was sometimes not very fast but he ran as many as 18 miles of track work, at times.

Okay, I stand corrected. Jakob does in fact do 25x400m on 30 seconds rest at 5-10k pace, having gradually built up over the years to this. But it was not a workout I've seen among the elites prior to that. El G did a session of mile pace 400s on 45s rest. I have done sessions of 16x400 or 8x800 on 45s rest alongside UNM athletes in the past.

Actually, I have copies of the workouts that Timmons gave Jim Ryun and although they were really long workouts (10 miles) none of them were short-rest, like swimmers do, but were very similar longer rest intervals to what track athletes have done for many decades. As far as "who does 25 x 400 on 30 rest" besides Ingbretsen, you can check the LetsRun article I posted earlier in this thread to see that in the mid-80s I had D3 runner, Danny Henderson do these genuine short rest workouts for two years as a post-graduate and he dropped from 13:55 to 13:23 in the 5K and from 29:23 to 28:03 in the 10K. However, I never saw any other high caliber runner do this type of genuine short-rest work from then until Ingbretsen made it "popular" recently.