Time In The Zone

Following my post, Training Zones, Rob Smith asked, "how much training do you do in each of the zones?". This will be my attempt to answer that question. Mainly it will explain why I can't just give a, 25% in this zone, and 33% in that zone, answer.

As a refresher I outlined my heart rate training zones as:
  • Aerobic 132-154bpm (70-82%HRmax)
  • Threshold 155-166bpm (83-88%HRmax)
  • VO2 167-188 (89-100%HRmax)

To understand how I apply these zones, I need to explain some aspects of my training philosophy. Firstly, training and racing fit into my life, and shouldn't compromise other aspects. Therefore, what I choose to do in training isn't always structured around what makes for best training practice, it is often dictated by it is what I can fit in. Recovery is highly variable, and as a shift worker, with two young kids, my recovery, especially sleep is quite often compromised. This can have a big influence on what I do within a session.

Second, I am no longer a believer in really keeping an eye on weekly totals. I do keep a training diary, but whenever I review it, I am looking more at the field tests, and indicator workouts, rather than worrying if I covered 60 or 80km in so many days. Mileage is important to a point, but there is a lot of limitation in reducing training to a set of numbers. There are plenty of times I choose not to wear a heart rate monitor and just run on feel.

Third, the heart rate zones are still reasonably arbritrary, plus performance isn't just limited to what the cardiovascular-pulmonary system can do. Heart rate isn't always an accurate guide on the intensity of training. An element of my current training is preparing the structure (muscles, connective tissue and bones) to be able to handle the prolonged higher intensity training that I plan on completing closer to race day. At the moment this involves short hill repeats, <100m sprints, lifting weights, loading under stretch and some plyometrics. In all of this training, heart rate is irrelevant, yet the loading on the body and recovery requirements can often be significant.

A Snapshot

To get a starting point, I'll just pull the data from my training diary. Due to a race being in the mix, I've taken a nine day, instead of seven otherwise, I think the results would be skewed towards indicating more higher intensity work than is typical. I'll begin with a brief description of each day's run training, with the totals at the end.

Day 1: Aerobic Run with pram (2 kids), 10.8km in 65min.

Day 2: MAF Test: 8.4km @ HR 152 + warm up & cool down

Day 3: RACE: Salomon Race 1, Trail Kew, 10.8km + warm up & cool down

Day 4: Aerobic Run: 15km, slow, 90min

Day 5: Aerobic Run: 10km

Day 6: Aerobic Run: 10km. Intended to be long run, but unwell kid changed the plans. As a result there was a reshuffle of the Threshold and Long runs.

Day 7: Threshold: warm up with 6x80m sprints then 2 x 7.6km at Threshold, 5min job between. The first repeat was mainly on feel and HR sat on or just below the bottom of the range. Second repeat right in middle of zone. Note that this has been the intended session through the last few weeks of Base training, but today was the first day I didn't have to call the threshold section short.

Day 8: Aerobic Run: 10km with pram. Stiff legs, difficult maintaining reasonable form.

Day 9: Long Run: 32km in 3 hours, after a very easy 30min, aim was to sit in the aerobic zone.

On top of this were a couple of strength sessions and one 30min, stupidly easy spin on the bike. Based on what my heart rate monitor recorded, the intensity split is:

  • Low;132bpm: 13min, 2%
  • Aerobic: 10hr, 10min, 83%
  • Threshold: 1hr, 29min, 12%
  • VO2: 23min, 3%

The percentages didn't seem quite right to me, so I scanned through the heart rate profiles of a few sessions. Of particular note, there was a fair amount of variability in the HR versus other indicators of intensity. In the race, I averaged a HR of 165bpm, yet the intensity was predominantly above my threshold. It looks like there HR was blunted a bit during the race. Maybe it was the excessively fast start, or the different style of technical running that caused it. Furthermore, the sprints, and pick ups during some of the aerobic sessions just don't show up in the heart rate records.

What is clear, is the substantial majority is within my Aerobic zone, with a bit around Threshold, and a very small amount above that. The low intensity area is almost insignificant. This snapshot is taking at end of my Base phase of training. As I progress through Threshold and Specific phases, I plan on a substantial increase in time spent at the threshold zone, and later more time spent in the VO2 area closer to race day. Yet I still predict close to 70% of training to be within the aerobic range.


  1. hi there

    thanks for the detailed reply!

    the reason i ask is because my coach is a firm believer in doing about 85% in the aerobic zone and 15% above the anaerobic threshold - actually he has published several papers on the subject. more anecdotally, looking at the ironman performances of his athletes, the strongest correlation he saw was a positive one between amount of aerobic training and overall result but he actually saw a NEGATIVE correlation between the time spent in between these two zones and the final result. i wrote a post on the subject here if you are interested http://fromrusttoironman.blogspot.com/2010/12/master-class.html .

    at the time i was reading maffetone, who i know you also follow to some extent, but maffetone was saying that we should do 100% of training in the aerobic zone.

    i found it very interesting what you were saying about the need to train the fast twitch muscles for late recruitment in a marathon. i suffered in much the same way as you in the ironman i did about a month ago, in that i found that the limiting factor was muscle fatigue. although i did some series on the bike in training, and unlike the marathon training i had done previously, i did no high intensity running work. its possible that it was a mistake but, of course, it is a delicate balance as you say, because you don't want to inhibit your fat burning capabilities.

    good luck for your marathon. i'm where you were a couple of years ago, wanting to break the 3h mark.

    i had another question which concerns how you carbo load. i found i had to rely on gels to get to around 10g of carbs per kilo of body weight (http://fromrusttoironman.blogspot.com/2010/11/carbo-loading.html) . my trainer though that the ingestion of so many high GI gels might interfere with the fat burning i had spent so many months training. i noticed that you said that you felt that the body could only carbo load a few times a year. i'd be really interested to know how you do it. i can wait until the post you do on the marathon preparations!


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