What is the purpose of this?

It all depends on where it fits in a CONTEXTUAL sense. For some, that workout may be relatively manageable; others, not so much. You haven't bestowed us with an ACCURATE idea of effort (or, if someone really cares to nitpick, your heart rate or lactate levels). But yes, it looks as though it was in place to target your oxygen uptake, but then most workouts are.

Also, I'd imagine you could always just ask your coach. If his or her response doesn't meet your expectations, delve further. If that doesn't satisfy, ignore it all and simply watch whether you improve...or not.

Thanks, like I said 800s felt 5k ish whilst 400s more 3k to 1500 feel

Harder/more intense workouts like this don't generally target or address a single physiological component; they target multiple systems, and naturally they do so in a greater capacity than an easier effort might. More to the point, they target your ability to handle such loads, and the necessary pacing involved, which is likely (or at least should be) focused on your upcoming races.

Put hair on your chest.

Joggernaut wrote:

Harder/more intense workouts like this don't generally target or address a single physiological component; they target multiple systems, and naturally they do so in a greater capacity than an easier effort might. More to the point, they target your ability to handle such loads, and the necessary pacing involved, which is likely (or at least should be) focused on your upcoming races.

^this. If it was just a set of repeat 800's @5k it would be vo2 max. However, this kind of difficult multi-pace workout generally stresses a number of systems and lets you test the limits of your fitness.

800s at 5k pace are much more beneficial for developing running economy at race pace than they are for actually developing V02 max.

Does this mean it's better to include more than one pace of running in workouts?

Curious Runner wrote:

My coach gave me 6 x (800 with 90 sec rest, 400 with 1 min rest). Its pretty tough to do the 400 then a minute later go straight into an 800, let alone six of them! I ran the 800s just a tad quicker than 5k pace and the 400s between 3k and 1500m pace. Just wondering what type of workout this is, V02 max?

Sounds hard

Does this mean it's better to include more than one pace of running in workouts?

Yes, it does, and it is. But then this depends on the workout and its objective. An easy recovery jog or a long steady-state effort might each be mono-paced, but in general almost all other running should mix the paces (i.e., forces) up.

A variety of training paces is as important as long, hard running or volume. Our bodies adapt relatively quickly to the same stimuli done over and over, regardless of how "challenging" it may feel (that challenge you feel could very well just be a valley of fatigue, as it so often is in less experienced runners). Once your body becomes habituated to a certain type of training it won't respond to other types without a serious effort to break the cycle; you want to out-think your body! But the key through all this, of course, is to remain consistent.

not sure about the science, but on the ground, what he is doing is trying to get you used to surges and hills.

the 400s take the place of a surge or a hill, when your heart rate goes up for a minute or so, then you settle back in to race pace.

if I were a coach I would put surges into the 800s rather than separate the short and long pieces.

For example, 6 x 800, surging between the 400 and 600 meter mark in each one.

I think we need to replicate race conditions more.