Middle-distance intervals

I feared for participation in tonight’s workout with so a dire weather forecast and the slight wane of enthusiasm that late Autumn seems to bring. The marathon is completed for many, the IMRA season had its last big hooray at Powerscourt and it is mainly cross-country fanatics that are keeping the running show on the road as November moves towards December.

That’s exactly what my training group has been about this fall and a small troupe turned out for the very fast interval session scheduled to be run on the grassy fields around UCD. One runner had to text me to cancel because he had locked his keys in his car. I won’t mention names but it is amazing what people will do to avoid running middle-distance pace.

The workout

We began with our usual roughly 15 minutes of easy jogging followed by some dynamic movements and a set of easy windsprints (sprinting 100m followed by 100m jogging around a GAA pitch). After that we only allowed some recovery to keep the heart rate up around 130bpm and muscles warm. We had a bit of wind and rain and one side of the 400m course sloped slightly down and another up. We had figured out over previous sessions that three sides of a GAA pitch equated to exactly 400m.

I instructed the runners to do the following: 4-8 x 400m @ 1500m race pace (71-73 secs for this group) with 1-2 minutes recovery. Athletes were instructed to get moving again between the 1st and 2nd minute once they felt like “they could hit the same pace again”.

The aim of the workout was eight repetitions, as you can usually handle just over double the distance of the race pace you are running for a set of repetitions such as this, but with a big race on Sunday, and the risk that the guys would set off at 800m pace by accident, I wanted them to cut out as early as four repetitions if they could no longer maintain the pace even with 2 minutes recovery.

It started slightly fast with a 69 but the group rallied very strongly and kept within 69-72 seconds for all eight repetitions and even cut their recoveries slightly towards the end to ensure they felt the amount of burn I had outlined. “Heavy acidic legs”, “strong burn in the throat” , these were just some of the images I tried to convey for them to get the right intensity.

Afterwards I asked how many more they could have done: “2-3” said one, “1-2, but it’d be really really hard”, said another. The perfect answer would have been “1 more” but with the Dublin Intermediates looming three days away, I preferred to stop the session slightly undercooked rather than overcooked.

With a workout like this where your body has used lactic acid and glucose intensely as a fuel, your body is flooded by acidic hydrogen ions. To help clear these from the muscles it is more important than ever to  do as much easy aerobic running afterwards. The lads did 15 minutes but you could easily do more after a session like this. A massage can help clear out such “junk” from sore legs but a good cooldown will accomplish much the same for free.

What we did ahead of the workout

Our group has focused on cross-country based workouts the last few months after coming back from a short post-summer break. We started out in Marlay Park and moved to the UCD area when the evenings turned too dark. We like to keep our sessions specific when possible so parks are a perfect training ground and we do everything on grass. If there’s a bit of a slope and it is a bit wet, even better. Lydiard used the cross-country session to help strengthen the legs of his runners and work out any weaknesses in their running form which would be ruthlessly exposed on a bumpy course. He reckoned that if you put a track man in a cross-country race, he’d have a better man on the track for next season.

We have been moving from workouts run at high aerobic intensity (at your lactate threshold or steady state) using progress calibration runs over 5km on grass, and then longer slower intervals. Eventually we moved on to faster work such as Ron Daws’ classic 400/100 workout (consisting of 20 repeats of 400m at your 10k pace, each followed by 100m running recovery) to further prepare the body for really fast running. Time trials of 3k followed and this week we decided to do our first interval session at middle-distance pace (the speed you would run in an 800m to 2000m race).

Why run that fast?

Cross-country races are all longer than 6km for men (and 3km for women) and with the tough terrain the pace will invariably be a good deal slower than middle-distance pace for the majority, so why use this type of training for the event?

First answer is: cross-country fields tend to go off extremely fast. Make any mistake and it can burn you off early and you never really recover. Doing a bit of work at these intensities can help build up the defenses to shake off the worst effects of a fast start and to hold a stronger drive to the finish. This only works if you have already developed your aerobic foundation to a high level and have done enough anaerobic training to establish the basic protection. If you don’t, this session will burn right through you.

Middle-distance pace versus normal repetition pace

Even for well-prepared runners, I only use these sessions sparingly. In fact, this was the first session at such intensity we have used all year. Most repetitions, in any training system, are run at between 3k to 5k race pace (eventually trying to get as close as possible to your VO2 max pace, or the speed you can maintain for 8 minutes). What many don’t realise is that while running at these paces your aerobic energy system is still contributing 88-93% of the energy! So the anaerobic system is only “mildly activated”.

Once you go beyond this pace, things change drastically as the demand for sugar (glucose) rises sharply: at 1,500m race pace the aerobic contribution drops to 76% and then to 57% for 800m pace. It is easy to see why it takes specialised training to be successful in the middle-distances. This means the negative side-effects of normal anaerobic training, such as hormonal stress and lowering of the body’s pH,  are magnified significantly. So we use this type of intensity very sparingly as it will quickly eat away the athlete’s hard-won aerobic condition. Once that foundation starts to crumble, the performances fall apart like a house of cards. We plan to do no more than another 1-2 sessions at this intensity to avoid burn-out. Middle-distance runners would use these workout more regularly but that’s a topic for another day.

So if you like the sound of this workout by all means try it out for yourself but be sure to first complete the right preparation and never jump straight into fast work like this or go out and do it week on week. Nothing good will come of it.

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Director and coach at Borg Coaching Services
Rene Borg is the head coach of Glendalough AC and a passionate runner competing over all distances and terrains.

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