For those of you that want the answer upfront, here it is:

There is reasonable evidence that an ~80:20 ratio of low to high intensity training gives excellent long-term results among endurance athletes that train daily.

This means that about 20 percent of your training volume should be at high intensity.

For those of you that need more details, settle in.

I do a fair amount of training plan consulting for athletes that I’ve trained in a one-on-one situation in previous years. These athletes want to take more responsibility for planning their own training and they love the challenge of putting together the puzzle pieces. One of the athletes that loves this kind of fun is Steve Kwiatkowski. You can find his blog here.

A few weeks back we entered a discussion about how much intensity to include in a training plan. The short of it is I spent a good part of my weekend doing research. The reference materials are listed at the end of the blog.

After all that research, I came to the conclusion that my previous guidelines are still valid:

• You should have 2 and no more than 4 key/breakthrough/stressful workouts each week. This includes big volume days, high intensity days or the combination of both.
• The volume of weekly intensity should be about 20 percent of your total weekly training volume.

I know these guidelines bring up more questions, but I can only squeeze so much into one blog. I’ll go into more discussion in future blogs.

For those of you that still want even more details I’m going to give you a few excerpts from the best collective research paper I found, with the link to the paper at the end of the blog:

If doing some HIT (1-2 bouts per week) gives a performance boost, is more even better? Billat and colleagues explored this question in a group of middle distance runners initially training six sessions per week of continuous training below lactate turn point (CT) only. They found that a training intensification to four CT sessions, one high intensity (HIT) session, and one lactate threshold (LT) session resulted in improved running speed at VO2max (but not VO2max itself) and running economy. Further intensification to two CT sessions, three HIT sessions and one LT session each week gave no additional adaptive benefit, but did increase subjective training stress and indicators of impending overtraining (Billat et al., 1999). In fact, training intensification over periods of 2-8 wk with frequent high-intensity bouts (3-4 sessions per week) is an effective means of temporarily compromising performance and inducing overreaching and possibly overtraining symptoms in athletes (Halson and Jeukendrup, 2004).  There is likely an appropriate balance between high- and low-intensity training in the day-to-day intensity distribution of the endurance athlete. These findings bring us to two related questions: how do really good endurance athletes actually train, and is there an optimal training intensity distribution for long-term performance development?

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We concluded that the greater polarization observed might have been due to better management of intensity (keeping hard training hard and easy training easy) among the most successful athletes. This polarization might protect against overstress. (Gale's comment: Easy training should be easy and fast training should be at intensities aimed at improving performance at the given goal distance.)

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The first study on runners to quantify training intensity using three intensity zones was that of Esteve-Lanao et al. (2005). They followed the training of eight regional- and national-class Spanish distance runners over a six-month period broken into eight, 3-wk mesocycles. Heart rate was measured for every training session to calculate the time spent in each heart-rate zone defined by treadmill testing. All told, they quantified over 1000 heart-rate recordings. On average these athletes ran 70 km.wk-1 during the six-month period, with 71 % of running time in Zone 1, 21 % in Zone 2, and 8 % in Zone 3. Mean training intensity was 64 %VO2max. They also reported that performance times in both long and short races were highly negatively correlated with total training time in Zone 1. They found no significant correlation between the amount of high-intensity training and race performance.

Comparing the intended and achieved distributions highlights a typical training error committed by recreational athletes.  We can call it falling into a training intensity “black hole.”  It is hard to keep recreational people training 45-60 min a day 3-5 days a week from accumulating a lot of training time at their lactate threshold. Training intended to be longer and slower becomes too fast and shorter in duration, and interval training fails to reach the desired intensity. The result is that most training sessions end up being performed at the same threshold intensity. Foster et al. (2001b) also found that athletes tend to run harder on easy days and easier on hard days, compared to coaches' training plans.  Esteve Lanao did succeed in getting two groups to distribute intensity very differently. The group that trained more polarized, with more training time at lower intensity, actually improved their 10-km performance significantly more at 7 and 11 wk. So, recreational athletes could also benefit from keeping low- and high-intensity sessions at the intended intensity.

The excerpts come from this paper:

Seiler, S., Espen, T., Intervals, Thresholds, and Long Slow Distance:  the Role of Intensity and Duration in Endurance Training, Sportscience 13, 32-53, 2009 (sportsci.org/2009/ss.htm)

Here’s the link: http://www.sportsci.org/2009/ss.htm

Further references:

Enhancing Recovery, Preventing Underperformance in Athletes:    Michael Kellmann editor

Endurance in Sport, Volume II of the Encyclopaedia of Sports Medicine an IOC Medical Commission

                Publication:    Shephard and Åstrand editors.

Exercise and Sport Science:     Garrett Kirkendall

The Athlete’s Guide to Recovery:   Sage Rountree