Repeats vs. Intervals - What's The Difference?

Yesterday running a six miler through my hometown I peered at my running form in the reflection of the downtown shop windows as I shuffled along on my first mile. Disgusted with my warm up mile running form, my brain told my body to increase pace to not look so old. According to my Garmin I went from an 8:20 pace to a 7:33 pace on my 3rd mile with my perceived effort remaining basically the same. I thought about how running a 6:30-6:40 pace in a ten mile race I ran recently seemed only a bit harder because I had mentally prepared myself beforehand, but this day was kind of a struggle since I just wanted to get the run in before traveling home. I know from reading Running Times recently how they compared running economy to a cars fuel economy. Kind of an ok analogy except they didn't mention that the cars fuel economy can be lessened by the brain controlling the gas pedal. Obviously we can mess up a cars fuel economy with erratic driving, but unlike a human the car has a fixed economy and you can't train it to a better fuel economy by doing repeats on the track. One thing that will probably never be fully understood is the measurement of the minds ability to override different types and levels of training by shear will power, which is extremely hard or impossible to calculate. Yes our bodies' running economy has a limit based on our physiology, genetic makeup, training, and form, but the intangible will always be our minds ability to take us beyond those limits.

Martin VW wrote:

Mr MattM wrote:I like to try and understand the training. I run what I run, but I still like to know what's behind it all.

+1.

I remember seeing articles over the years comparing stocks picked by fund managers versus those picked by throwing darts. In some cases, the dartboard stocks performed better.

That doesn't mean I'm picking stocks using a dartboard.

Maybe you should in this economy!

Mr MattM wrote:I like to try and understand the training. I run what I run, but I still like to know what's behind it all.

Me too. I don't know enough to contribute, but I like to think every run has a definite role in improving my performance and to have an idea what that role is.

fostever wrote:

Disgusted with my warm up mile running form,

I have paid attention to my form in the last 2 years and felt significant improvement, but my recent half marathon photo said otherwise or not enough(?).

Repeats = the hard part
Interval = the easy part in between


Example: 8 x 800m repeats at 5k with 400m intervals


Running economy? Let me know when you crack the code. I'm too busy getting slower.

Dave-O wrote:Repeats = the hard part
Interval = the easy part in between


Example: 8 x 800m repeats at 5k with 400m intervals


Running economy? Let me know when you crack the code. I'm too busy getting slower.

Well, yeah, but we were discussing the relative effort levels of faster vs. slower repeats in the way Daniels defines them.

And yes, you're a tortoise compared to the rest of us. Or not.

mul21 wrote:

Dave-O wrote:Repeats = the hard part
Interval = the easy part in between


Example: 8 x 800m repeats at 5k with 400m intervals


Running economy? Let me know when you crack the code. I'm too busy getting slower.

Well, yeah, but we were discussing the relative effort levels of faster vs. slower repeats in the way Daniels defines them.

Not just Daniels.

Hudson uses the term "Speed Intervals:

Speed Intervals

Speed intervals are short or relatively short intervals run faster than 5K pace...In my system, the purpose of speed intervals is to provide neuromuscular fitness support for specific endurance."

McMillan utilizes "Tempo Intervals," "Cruise Intervals" and "Aerobic Capacity Intervals."

Tempo Intervals

Tempo Intervals are like fast tempo runs broken into two to four repeats with relatively short recovery jogs. The appropriate race paces for tempo intervals are 10K to 15K race pace and they should last between eight and fifteen minutes. Unlike the previous workouts, Tempo Intervals are the first workouts to allow for a recovery jog between hard efforts. In this case, you jog two to five minutes between each repeat then start the next one.

A tempo interval workout that I've had particular success with is two (or three) times two miles at 10K race pace effort with three minute recovery jogs between repeats."

Cruise Intervals

The Cruise Interval workout was popularized by the running coach, Jack Daniels. They, like the other Stamina workouts, are meant to increase your lactate threshold pace. Cruise Intervals are like shorter and slightly more intense tempo intervals. They last three to eight minutes and the pace is between 8K and 12K. Like tempo intervals, they are followed by short recovery jogs (30 seconds to 2 minutes). You'll probably find that it's easy to run too fast on these. The tendency is to treat them like regular long intervals. However, keep it under control and work on a smooth, fast rhythm. Control in training is key to improvement."

Aerobic Capacity Intervals

Here's where we get to the fast stuff. These workouts are what most of us think of as "speedwork". They last between 400m and 2000m and are run between 3K and 8K race pace. The goal here is to spend time at your maximum aerobic capacity (or VO₂max). Because the pace is faster, you must take a recovery jog of about half the distance of the repeat (or jog for the same duration as the faster running). So if you run a 1200m repeat, you would jog for about 600m to recover. These workouts allow you to maintain your speed over a longer period of time.


Pfitzinger anso uses the terms "Cruise Intervals," but doesn't distingush them from "LT Intervals."

And, from a Wiki source (just to make cutting and pasting easier)

Interval (I) pace

Intensity at 98-100 % HR_max. This intensity stresses the VO₂max to raise the maximum oxygen uptake capacity. Since the pace is very intense, it can only be sustained for up to 12 minutes during racing. To cope with the intensity, and to train for longer periods of time, this training is performed as interval training, hence the name. The interval between each work bout should be a little less than the time of the work bout. Optimum intervals are 3-5 minutes long. There is no benefit to exceeding 5 minutes at this pace, under Daniels' theory, which means that despite the popularity of mile-repeats in many running groups, Daniels discourages them for people whose pace is slower than about 5:00/mile, preferring shorter intervals such as 1200 meters.

For example, an I session can be 6 x 800 m at I pace with 400 m recovery jogs. At most 8% of the weekly training miles should be I pace.

So, Martin, what are your thoughts now?

Fostever - interesting you should mention that. Sometimes when I'm confined to the treadmill, my HR will be the same for 9:30 as it is for 7:40ish. And I've read (somewhere, sorry, can't cite it) that humans are "most efficient" at around a 7:45 pace. I don't know what exactly that meant (calories burned per mile?), but it seems related to running form and economy.

Mr MattM wrote:So, Martin, what are your thoughts now?

My take? Since some (most?) won't want to wade through, here's my bottom line.

If the goal is building stamina, VO2Max and lactate tolerance, in the simplest form, "speedwork" within marathon training cycles would be a mixture of strides with EQUAL recoveries (surges at 5K pace or faster, 1 minute on, 1 minute off), 800s @ 5K pace with MEDIUM (~ 2 minute) recoveries, and threshold miles @ 10K pace with SHORT recoveries (60 - 90 seconds). That would seem to be the recipe, at least from the way I read things from Hudson, McMillan and Daniels. Now, they also are very similar philosophically, which is why I have their material and not anything from Pfitzinger, Higdon or others.

It doesn't seem that speedwork at 3K or faster paces with full recoveries play a prominent role in marathon training for MOST marathoners within the marathon training cycle. Daniels does include "repetition-type" workouts (short, fast speedwork with full recoveries), but I'd say that's for the 2:45ish guys / sub 3 women running 90+ mile weeks.

The Boring, Unnecessary Details

Putting the naming issue aside, I have my Hudson Run Faster, my Daniels Running Formula Second Edition and my McMillan plans in front of me. Since this site focuses mostly on marathon training, and because the training for other distances would very significantly, I'm looking at the "speedwork" contained in those three coaches' marathon training plans.

"Short"

McMillan and Hudson both utilize what I came to call "surge" runs - 1:00 @ 5K (Hudson) to slightly faster than 5k (McMillan) with a 1:00 recovery. They're a little long - and therefore done a little slower - than at least what I know of as "strides," but I think that's really splitting hairs. The purpose is the same - build turnover and improve lactic acid tolerance.

400s, which would still be "short" for a marathon training plan, are also used. In looking back, my McMiillan plans didn't include any, but I think it was because of the inclusion of a higher frequency of hill work to train specifically for Boston. But from an article on the subject, he would set them up as:

"Six Weeks to Race Day: 12-16 x 400m with 200m jog in sets of four at half marathon, 10K, 5K and 3K race pace"

Article is here http://runningtimes.com/Article.aspx?ArticleID=20190

I found a "killer" 400 workout in Hudson's "Level 3" plan - "Specific-Endurance Intervals 3 miles easy, 2 x (10 x 400m @ 10K - 5K pace w/1-min. active recoveries), full recovery between sets, 3 miles easy."

20 x 400's a TOUGH workout at anything approaching 5K pace with just 1 minute recoveries, less so at 10K pace.

I had to go to Daniels' "Elite" training plan to find anything short, and I know I couldn't handle a workout like this:

2 miles Easy pace + 5 x (1,000m Interval (sub-5K) pace with 2 minute jogs) + 6 X (400 Repetition (sub-3K) pace with 3 min Easy pace) + 2 mioes E pace.

So, I would say that Daniels doesn't believe that short, fast repeats play a prominent role for anyone training for the marathon outside of really serious runners.

"Medium"

If we seek out a "traditional" marathoners' track workout (800s), McMillan calls them "Cruise Intervals" and a typical workout would be:

15 to 30 minute Warm-Up + Cruise Interval Workout: 6 to 8 times 800 meters with 200 meter recovery jog between plus 3 x 200m with 200m recovery jog + 15 to 30 minute Cool-down

Build Stamina - lactate threshold speed. RUNRR

RUNRR is McMillan's prescribed recovery routine - you can read about it here http://www.mcmillanrunning.com/articlePages/article/7

Hudson calls them "Specific Endurance Intervals." He doesn't use them often, prefering time-based intervals (1 / 2 / 3 minutes) to distance-based, but where they do appear, it's "3 miles easy 6 x 800m @ 5K pace w/2-min. active recoveries 3 miles easy."

In Daniels, again, not a lot of reliance on middle distance speedwork. No 800s, but workouts such as this: "Sets of 1,000m, 1,200m, or miles I (sub-5K) pace, with 3-, 4- or 5-minute recovery jogs to total lesser of 8% of weekly mileage and 10km." I think those times relative to distance and speed would probaby constitute full recovery, or close to it.

"Long"

McMillan included more "Tempo Intervals" in my Boston plan than Cruise Intervals. These would be at 10K to 15K pace and ranged from

15 to 30 minute Warm-Up + Tempo Interval Workout: 4 to 5 x 1600 meters with 1 minute 30 seconds recovery jog followed by 3 times 200 meters with 200 meter recovery jog + 15 to 30 minute Cool-down

Build Stamina - lactate threshold. RUNRR

to

15 to 30 minute Warm-Up + Tempo Interval Workout: 3 times 3000 meters with 3.5 minutes recovery jog followed by 3 times 200 meters with 200 meter recovery jog + 15 to 30 minute Cool-down

Build Stamina - lactate threshold. RUNRR

Hudson still calls them Specific Endurance Intervals, with the pace for 1 mile being 10K-ish, but with recoveries ranging from 2 minutes to 3 minutes.

In Daniels, a pretty heavy reliance on Threshold (10K) pace runs, ranging from 5 to 6 minutes with 30 - 60 second recoveries, to 10 to 12 minutes with 2 minute recoveries.

Geesh, I'm gone for work travel for a week and there's a novel's worth of info here to digest. I'll need to print this out Friday and read it while pretending to pay attention at a meeting. I think I saw my name or at least the workouts I do taken in vain somwhere in there...

Well I stand corrected. I didn't realize so many coaches use the term "interval" for the hard portion of the workout.

Martin VW wrote:

Michele "1L" Keane wrote:Wow, my brain hurts from trying to digest all of this; however interesting it is. I think I'll just go Run More and toss in some intervals, repeats and tempo runs. Carry on. Not sure where a 50 yr old woman who has run for over 35 yrs can go at this point anyway. I'm just trying not to lose too much "speed" and the longer intervals with shorter recovery work for me during half and full marathon cycles.

Oh, and I really glad that Martin has joined us! Keep up the discussions.

Yeh, I think in the end it'll be helpful to put a nice bow on everything, to demystify it a little.

I know a certain someone that lives in the Wash DC area does full recovery for almost all of his speedwork, while almost everything in McMillan has shorter recoveries. I'd at least to understand what he's getting the benefit of that I'm not.

And the speed sessions put together by the coach of my running club regularly mixes in "repeats" and "intervals" but I've never fully understood the benefit.

And, thanks.

Ok, I did want to answer this one as to what my thinking is about longer recoveries (or "rest intervals" between the fast "repeats" is how I define them).

For repeats of a mile/800/400, I like to do a recovery time period of roughly equal to the amount of time running the fast repeat. A classic example of this is the "Yasso 800" workout where you do 10x800 at roughly 5K pace and you are jogging a 400 in the same amount of time it takes you to run the 800 hard. So it might be 3:00 "on" for the hard 800, 3:00 "off" for the jog/walked 400. I extend that same type of rest interval approach down to 400s and up to the mile. When I do a 4x1 mile workout, it is pretty much a complete rest I get to during the long recovery period. So if I did a 6:00 mile, its a good 5:00+ minutes before I line up again. I'll get water, jog, walk and let the heart rate come all the way back down to complete low and rested.

Why?

To keep the speed of the hard parts faster.

Here's my thinking. A typical training week in the meat of a marathon cycle from Coach Dave will have 3 key workouts each week: speed/tempo/long run.

The long run one is obvious and sometimes gets mixed in with a little goal pace running but often is just "get x miles done"

The tempos are ALWAYS fast continous runs. I'm not doing any "float" or recoveries or fartlek type stuff within the tempo portion unless it is something like 2 x 3 miles with a full recovery between. Within the 3-6 mile tempo portion, I'm at HMP down to 10k pace the whole time. Not easy or particularly fun and the purpose is to teach me to run while in a bit of discomfort and extend out both mentally and physically how long I can do that.

True speed days? Totally different. The purpose of the workout in my mind is to work on turnover and hitting race and sub-race paces. The Yasso 800 workout I described above would be a completely different type of workout with 30-60 rests between each 800. Not a better workout, just different. No runner could hit the same speeds on the 800s taking such a short rest. At slower speeds in the 800s, you are not learning to do the same type of leg speed turnover. So it becomes more of an endurance challenge which is fine but the actual pace of the workout will slow which I don't like on track days.

As an example, I once went to Boston and did a workout with MVW where we did mile repeats with 1:00 rest intervals. A lot of people do a similar workout. Something "on", 1:00 rest, go again. My problem with it is that the workout more closely approximates a tempo run than what I think of us as true track work. With that short an interval, the speed of the miles run hard gets slower. So instead of mashing it on the mile repeats at 5k pace or faster and learning what the legs feel like running that fast, you will never really go much faster than 10K pace if you are only taking 1:00 rest intervals. So again, its a different workout with the short rest interval and FOR ME AT LEAST not as good a one since it more closely mimics the benefits I'm already getting out of doing a weekly fast continous tempo run. In fact, I think of the "1:00 rest intervals" as "tempos for runners who don't like FCR tempos".

I don't go to the track to do anything but 400s to miles....when I'm there, its time to run FAST. Short rest intervals make it more like tempo (not overly fast) paces which I'm fine with doing on the roads.

Chris M wrote:

For repeats of a mile/800/400, I like to do a recovery time period of roughly equal to the amount of time running the fast repeat. A classic example of this is the "Yasso 800" workout where you do 10x800 at roughly 5K pace and you are jogging a 400 in the same amount of time it takes you to run the 800 hard. So it might be 3:00 "on" for the hard 800, 3:00 "off" for the jog/walked 400. I extend that same type of rest interval approach down to 400s and up to the mile. When I do a 4x1 mile workout, it is pretty much a complete rest I get to during the long recovery period. So if I did a 6:00 mile, its a good 5:00+ minutes before I line up again. I'll get water, jog, walk and let the heart rate come all the way back down to complete low and rested.

Why?

To keep the speed of the hard parts faster.

Here's my thinking. A typical training week in the meat of a marathon cycle from Coach Dave will have 3 key workouts each week: speed/tempo/long run.

You're missing the purpose of the workout by doing them this way. Your HR isn't supposed to get completely back down. You're supposed to be teaching your body to run fast while fatigued. Now, that's not nearly as important at the marathon distance as it is if you were concentrating on say, 5K races. You're getting enough of the benefit to help, but certainly not the full benefit as you would if you slowed down a bit and did the rest portion of the workout as designed.

It's similar to Kenny running his repeats in the 3rd lane. He's not really doing the workout as intended because he's running further than he's supposed faster than he's supposed to. My high school coach always told us he'd rather see us run our speed workouts a tick slow than too fast. I'm going to trust his judgement on that based on how many state champions he produced.

I'm with Chris on this, but for I only apply it to 400s. For 800s and farther, I will slow it down a bit and shorten the recovery.

400s are all-out. They are too short for anything else, IMO.

Mr MattM wrote:I'm with Chris on this, but for I only apply it to 400s. For 800s and farther, I will slow it down a bit and shorten the recovery.

400s are all-out. They are too short for anything else, IMO.

If you have Daniels Running Formula handy, look at Fig 8.2 on P. 125. He explains that 400 workouts are benefitical, if the recovery time is kept short, for spending a lot of time at VO2Max. He suggests starting a new 400 every 2 minutes, so that your recovery time is however much you have left of the 2 minutes after completing the interval (i.e., 80 seconds on / 40 seconds off).

If you're doing the 400s "all-out," you won't have enough recovery time to do the ones that follow.

400s are beneficial when run all-out, as well. As I said before, it's for neuromuscular efficiency. I'll run 800s/1200s for VO2Max work with shortened recovey (typically 72 sec recovery intervals on 800s). I can work on LT with traditional tempo runs, progression runs, or longer repeats (typically 2 miles).

To get full neural synapsis activity and certain types of muscle recruitment requires near all-out effort. If/when I do run 400s, that's my purpose. Other people's purposes may differ.

mul21 wrote:

Chris M wrote:

For repeats of a mile/800/400, I like to do a recovery time period of roughly equal to the amount of time running the fast repeat. A classic example of this is the "Yasso 800" workout where you do 10x800 at roughly 5K pace and you are jogging a 400 in the same amount of time it takes you to run the 800 hard. So it might be 3:00 "on" for the hard 800, 3:00 "off" for the jog/walked 400. I extend that same type of rest interval approach down to 400s and up to the mile. When I do a 4x1 mile workout, it is pretty much a complete rest I get to during the long recovery period. So if I did a 6:00 mile, its a good 5:00+ minutes before I line up again. I'll get water, jog, walk and let the heart rate come all the way back down to complete low and rested.

Why?

To keep the speed of the hard parts faster.

Here's my thinking. A typical training week in the meat of a marathon cycle from Coach Dave will have 3 key workouts each week: speed/tempo/long run.

You're missing the purpose of the workout by doing them this way. Your HR isn't supposed to get completely back down. You're supposed to be teaching your body to run fast while fatigued. Now, that's not nearly as important at the marathon distance as it is if you were concentrating on say, 5K races. You're getting enough of the benefit to help, but certainly not the full benefit as you would if you slowed down a bit and did the rest portion of the workout as designed.

It's similar to Kenny running his repeats in the 3rd lane. He's not really doing the workout as intended because he's running further than he's supposed faster than he's supposed to. My high school coach always told us he'd rather see us run our speed workouts a tick slow than too fast. I'm going to trust his judgement on that based on how many state champions he produced.

Yeah, running FAST isn't really the important adaptation during marathon training. Because marathoning is sub-maximal, you're looking to increase your lactate threshold so that your sub-maximal level is faster, and so that you can go farther. The speed phase of marathon training is designed to support the 8 week marathon-specific strength/stamina phase that leads into taper.

How? Well, according to Daniels, you want to do tempo runs AND what he calls "Cruise Intervals" or "short-rest intervals perfromed at threshold pace."

"The typical duration of individual runs within a cruise interval session varies from about 3 to 15 minutes, with 1 minute of recovery time followning each 5 minues of running time."

"The great advantage of the brief recoveries is that blood-lactate levels remain fairly constant, and the runner experiences threshold effort throughout the entire training session, which can last a fair bit longer than could be accomplished with a steady tempo run at threshold pace."

So, doing 800s to 1600s as one of the hard sessions and tempo runs in the weeks in between would fit what Daniels says. Something like 800s / tempo / 1600s / tempo / 800s / tempo etc.

BTW, we were booking along at a lot faster than threshold pace in that session at Tufts, despite the 1 minute recoveries.

Mr MattM wrote:400s are beneficial when run all-out, as well. As I said before, it's for neuromuscular efficiency. I'll run 800s/1200s for VO2Max work with shortened recovey (typically 72 sec recovery intervals on 800s). I can work on LT with traditional tempo runs, progression runs, or longer repeats (typically 2 miles).

To get full neural synapsis activity and certain types of muscle recruitment requires near all-out effort. If/when I do run 400s, that's my purpose. Other people's purposes may differ.

No argument, but as I mentioned earlier, McMillan and Hudson don't include that type of training within a marathon cycle, and Daniels suggests it exclusively for "elite" training. So, from what I've read, I'm not sure if that neuromuscular efficiency training is best within a marathon training cycle, but maybe fits better in between cycles.

As a Canova fan, I'll just add that he believes that ALL SPEEDS need to be incorporated in training to maximize results. Canova says (with his typical slightly broken English writing style):

Speed faster than 110 % of 5k pace have a MECHANICAL goal, and/or can work for increasing the LACTIC POWER. We can use only few repetitions with very long recovery.

Martin VW wrote:

Mr MattM wrote:400s are beneficial when run all-out, as well. As I said before, it's for neuromuscular efficiency. I'll run 800s/1200s for VO2Max work with shortened recovey (typically 72 sec recovery intervals on 800s). I can work on LT with traditional tempo runs, progression runs, or longer repeats (typically 2 miles).

To get full neural synapsis activity and certain types of muscle recruitment requires near all-out effort. If/when I do run 400s, that's my purpose. Other people's purposes may differ.

No argument, but as I mentioned earlier, McMillan and Hudson don't include that type of training within a marathon cycle, and Daniels suggests it exclusively for "elite" training. So, from what I've read, I'm not sure if that neuromuscular efficiency training is best within a marathon training cycle, but maybe fits better in between cycles.

But if I can do 8-10x400 all out with long recovery intervals, and then a 10 mile easy run later in the day, how am I now adding to my marathon training results? If I have built a large aerobic base and am incorporating appopriate levels of LT and VO2Max work, why would I not benefit from a few (emphasis on 'a few') extremely hard/fast but short training efforts? I think it's a cherry on top kind of thing. If you can do it, great! If not, it's not likely to be a major limiting factor.

It would never be a staple training session for me, but I can see it's value... even in marathon training.

Mr MattM wrote:

Martin VW wrote:

Mr MattM wrote:400s are beneficial when run all-out, as well. As I said before, it's for neuromuscular efficiency. I'll run 800s/1200s for VO2Max work with shortened recovey (typically 72 sec recovery intervals on 800s). I can work on LT with traditional tempo runs, progression runs, or longer repeats (typically 2 miles).

To get full neural synapsis activity and certain types of muscle recruitment requires near all-out effort. If/when I do run 400s, that's my purpose. Other people's purposes may differ.

No argument, but as I mentioned earlier, McMillan and Hudson don't include that type of training within a marathon cycle, and Daniels suggests it exclusively for "elite" training. So, from what I've read, I'm not sure if that neuromuscular efficiency training is best within a marathon training cycle, but maybe fits better in between cycles.

But if I can do 8-10x400 all out with long recovery intervals, and then a 10 mile easy run later in the day, how am I now adding to my marathon training results? If I have built a large aerobic base and am incorporating appopriate levels of LT and VO2Max work, why would I not benefit from a few (emphasis on 'a few') extremely hard/fast but short training efforts? I think it's a cherry on top kind of thing. If you can do it, great! If not, it's not likely to be a major limiting factor.

It would never be a staple training session for me, but I can see it's value... even in marathon training.

Well, according to Daniels, "because the purpose of interval training is to stress your VO2Max, you must spend time running at VO2Max...because a single run doesn't last long enough to allow your body to reach VO2Max, the short recovery helps you to achieve VO2Max more quickly in subsequent workbouts." The short recovery doesn't permit full recovery back to resting VO2Max, so with each new workbout VO2Max is reached more quickly than in earlier bouts or with longer recoveries."

Of course every hard workout has its value in marathon training. The question is, are you getting the most value out of the time spent?

Yes, because I am doing VO2 work elsewhere, and the 400s are for biomechanical and certain muscle recruitment purposes. There is also the whole creatine phosphate energy system to consider.

I'm not sacrificing VO2 work at all, just adding another component to the overall systems' training load.

Every speed should be hit. If you never run with anything but short recoveries, you simply cannot do 400s or mile repeats at the same speed. Unless you are sandbagging it and not trying, you will be significantly faster on mile repeats with 4+ minute recoveries versus 1 minute. Ditto for slightly longer 400 recoveries. And I think there is significant value in running 400s and mile repeats at those faster paces. I LOVE going back to MP after ripping off a series mile-race-paced 400s. It feels like jogging! I am a big believer in knowing the purpose of each workout and when I am doing a max speed type workout, I'm looking to learn and hone running at the fastest pace possible and really work on mechanics and form. Tempos and other speed workouts work on quicker on/off transitions, sustained VO2max levels and other adaptations.

There's a reason "Yasso 800s" are probably the single most famous track workout for marathoners. The simplicity of it and the long recoveries with a ton (almost 5 miles) of 5k-paced running makes it, in my mind, a much better workout than some of the super short recovery ones done at lower speeds.

I think if you really want the benefit of Yasso's, you need to change them up, either by running at 3k pace and getting the benefit from the long jog interval, or running a bit longer at 5k pace e.g 1k-1200 meters, if you prefer 3+ minute interval.

When I am fit, it only takes 90 seconds to bring my heart rate back down to 120 after 800meters @5k pace, which is when the next repeat should start. For longer intervals like 1k and 1200 meter, where you spend more time above the lactate threshold, the longer interval makes more sense.

I really think of Yassos as being similar to Pfitz's 600 meters where you run as quickly as you can and jog until you can do it again.

As long we incorporate 3k, 5k, 10K-HMP, and MP(later in the marathon program) paces in the workouts, along with strides, the outcome will be good.

I also think that if you can run 10x800meters at Yasso pace(2:50 for a 2:50 marathon) with 75-90 second or so intervals, you are ready to hit your target for the marathon, assuming you get in the long runs.

The other key is not running the interval too fast, a major mistake a lot of us make. That changes the workout more than the speed of the repeat.