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Marathon performance: why training intensity balance matters
What is the optimum balance between long-slow distance and higher intensity training for marathon runners? SPB looks at some fascinating new research and the answer may surprise you!
When it comes to putting together a marathon training program, there are many things to consider. “How many weeks of training preparation are needed?”, “How often should I train?”, “How long should my longest run be?” are all questions where the answer will depend very much on the individual background and circumstances of the runner. Regardless of these questions however, the two most important factors that will determine your performance are how many miles per week you accumulate (volume) and how much of this volume is performed at a hard or easy pace – more technically known as ‘training intensity distribution’.
Common approaches
A commonly used approach by many non-elite runners seeking to improve performance is to focus on moderate intensity training(1), which is hard enough to push the body out of its comfort zone and promote gains in endurance, but not so hard that exhaustion ensues. Compared to a training regime of mainly long, slow distance training, this approach almost always leads further gains in fitness and performance. But is this kind of training intensity distribution really optimal?
Over the past decade or so, evidence from elite athletes such as triathletes, cyclists and runners suggests that for maximum performance gains, there could be a better way. This better way revolves around a concept known as ‘polarized training’(2-4). The polarized approach to training proposes that endurance athletes spend a large proportion of their training time working at low intensity (ie in the ‘easy’ purely aerobic zone – zone 1) and a small proportion at a very high intensity (near maximum power output – zone 3) with very little time spent training at or near to lactate threshold (zone 2 – see table 1).
Table 1: Training zones and intensities
|
Zone |
Sometimes known as: |
Subjective feel: |
Typical blood lactate |
Typical heart rate |
|
1 |
‘Aerobic’, ‘easy’, ‘recovery’, ‘long slow distance’ etc |
Easy – you feel like you can keep going and going |
Less than 2mmol per litre (mM/L) |
Under 80% and typically around 70-75% of maximum |
|
2 |
‘Threshold training’, ‘intensive endurance’ etc |
Moderately hard – hard (you know you’ve had a workout) |
Between 2 and 4mmol per litre (mM/L) |
Around 80-85% of maximum |
|
3 |
‘Very high intensity’, ‘race pace’ etc |
Very, very hard (you won’t want to stay in this zone for long!) |
More than 4mmol per litre (mM/L) |
Significantly over 85% of maximum |
The polarized theory of training uses the concept of three ‘intensity zones’ - 1, 2 and 3. Studies on elite athletes such as runners and rowers suggest that the best way of achieving maximum endurance potential is to spend the bulk of training time in zone 1, at least some time in zone 3 but not to spend too much time in zone 2 (the moderately hard zone).
Theory and practice
The theory behind a polarized approach is that it provides an excellent ‘aerobic foundation’ for endurance performance, yet allows for high-intensity work that really stimulates training adaptation (ie aerobic fitness gains) without excessive fatigue. This is in contrast to the moderate-intensity distribution approach, where much of the time training is intense enough to induce fatigue but never hard enough to provide the intense training stimulus needed to make maximum fitness gains.
However, while this polarized approach sounds logical and appealing, much of the evidence supporting its use is derived from elite athletes – not from amateur or recreational athletes. The question then is whether a polarized approach is best for all athletes, regardless of training status? It turns out that there’s conflicting evidence on what kind of training intensity distribution might work best for amateur and recreational athletes.
For example, a study on ‘well-trained but not elite’ cross-country skiers, runners and cyclists compared four different approaches to endurance training over a 9-week period(5). These were as follows:
· High-volumes of steady-state training (the default mode for many endurance athletes!)
· Threshold training
· Polarised training
· Interval training (high-intensity intervals)
The results showed that it was the polarised training regime that produced the biggest improvement in aerobic power (up by 11.7%), followed by high-intensity intervals (up by 4.8%). In addition, the gains in peak power and times to exhaustion managed by the athletes in an incremental test were greatest in the polarised group (17.8% longer), and the amount of power the athletes could produce at a blood lactate level of 4mmol/L (a measure of maximum sustainable power) was increased most in the polarised group (by 8.1%).
Question marks
While the results above are impressive, other studies have questioned whether a polarized approach really is best for amateur athletes. A study by Spanish scientists on amateur triathletes compared two groups who performed the same total training volume but who followed two different training intensity distributions (see figure 1)(6):
· Polarized – 84.4%/4.3%/11.2% distribution of total training time for zones 1,2 and 3, respectively (typical profile of intensity distribution recommended for elite endurance athletes).
· Pyramidal – 77.9%/18.8%/3.3% distribution of total training time for zones 1,2 and 3, respectively (the typical kind of intensity distribution followed by non-elite endurance athletes when left to their own devices).
The key finding was that no significant differences were observed between the polarized and pyramidal race times, and both training distributions showed produced significant fitness gains in the triathletes – in all three disciplines. In fact, the pyramidal group showed a statistically significant improvement in maximum running speed at lactate threshold and maximum aerobic speed - gains that led the pyramidal group to turn in slighter faster times in the Half-Ironman race.
Figure 1: Time percentage in each zone by segment during specific training period
Another study examined six weeks of a training intervention comparing a polarized intensity distribution to a moderate training intensity distribution where recreational athletes performed 40% of their training at medium intensity (zone 2) and 60% at low intensity (zone 1)(7). In particular, the researchers investigated how these two distributions affected sub-maximal and maximal performance indices during running and cycling in non-elite triathletes who were averaging around 11 hours of total training per week. It found that while both groups notably improved their second lactate threshold (the intensity at which fatiguing lactate begins to rapidly accumulate in muscles) by around 2.8% and their running performance by around 5.4%, neither cycling nor running performances in the two groups differed between the two groups after the intervention. In plain English, both of the training interventions produced the same benefits - or to put it another way, the polarized approach was NOT any superior to the commonly used moderate-intensity training distribution.
Given that data on the optimum training intensity distribution for amateur and recreational endurance athletes is scarce and conflicting, are there any other ways to discover what might work best? Some researchers have looked not at individual studies, but what the research as a whole says. For example, a 2022 systematic review study on the training intensity distributions of middle- and long-distance runners concluded that a combination of high-volume at low-intensity (over 70% of overall training volume) and low-volume at threshold and high-intensity interval training (under 30%) is necessary to optimize endurance training adaptations(8). However, this data was derived from a wide ranging mix of athlete ability levels, so its relevance to amateur and recreational athletes is unclear.
Look back to look forward
To try and answer the question of what training intensity distribution might work best for amateur and recreational runners and other endurance athletes, a team of Brazilian and Spanish researchers have taken a reverse approach in a new study just published(9). Instead of looking at different training interventions that produce different outcomes, they looked at the outcomes first, then delved backwards to see what kind of training intensity distribution had produced the most successful outcomes.
Published in the International Journal of Sports Medicine, this study looked retrospectively at the training session data from the 16 weeks preceding 151,813 marathon races completed by 119,452 runners, almost all of whom were competing as recreational or amateur athletes. The researchers gathered together the training diary data from the 119,000+ runners and analyzed it for the training intensity distribution – ie what proportion of the runner’s training was conducted in zone 1, zone 2 and zone 3. They then compared the training intensity distribution data to each runner’s performance(s) in the marathon(s) they ran to see how training intensity distribution impacted subsequent performance.
What they found
The data analysis revealed quite a lot of unexpected information, including the following:
· The most common training intensity distribution approach was pyramidal (most time training in zone 1, with some time in zone two and least time of all in zone three), which was adopted by over 80% of runners with the fastest marathon times.
· The amount of training time completed in zone 2 and zone 3 remained relatively stable across performance levels, but the proportion of time spent in zone 1 was higher in progressively faster groups.
· There was a strong and significant negative correlation between marathon time, total training volume and the proportion of training volume performed in zone 1. In plain English, the faster marathon runners clocked up greater training volumes, and spent proportionately more of that training volume in zone 1!
· Runners who spent proportionately more time training in zones 2 and 3 tended to record slower marathon times, with higher proportions of zone 2 and 3 training leading to slower times.
· The average training volume across all runners was 45km (28 miles) per week, but the fastest runners under two and a half hours) accumulated three or more times the volume of slower runners.
In summary, this data showed that accumulating lots of training time in zone 1 was the key to good marathon performance rather than focusing on higher-intensity work. But when high-intensity work was carried out, a pyramidal structure with more zone 2 time than zone 3 seemed to produce faster times.
Implications for distance runners
Every runner is different and responds slightly differently to a training stimulus. Therefore, making blanket training recommendations is fraught with difficulty. However, the research detailed in this article suggests that unlike elite athletes, amateur endurance athletes competing over longer distances may not fare as well if they adopt a polarized training approach. Instead, using a pyramidal training intensity distribution is likely to yield better performance gains. It’s still recommended that the bulk of training is carried out in zone 1, but instead less work is done in zone 3 than in zone 2.
Talking of zone 1 training, the data above from retrospective analysis of marathon performances is fascinating. The main finding was that it was zone 1 volume and proportion that primarily determined finish times. The runners with the fastest times accumulated more zone 1 training hours and performed proportionately more time in zone 1 than the slower runners! Although this might seem counterintuitive, it wasn’t that these fast runners did no zone 2 and 3 training – just that it comprised only a small % of total time. Upping the proportion of zone 2 and 3 training predicted slower times – not faster times.
As to why, the explanation is likely twofold: firstly, building a great aerobic base with high levels of zone 1 training is the foundation of endurance performance, especially over longer distances such as the marathon. In addition, marathon performance is heavily dependent on the aerobic power to weight ratio. Lots of long steady-state training runs helps burn calories and fat, thereby shedding excess weight. This automatically helps marathon performance, even if other aspects of endurance fitness remain unchanged.
There are also the ‘conditioning factors’; amateur and recreational runners need to be able to run for up to four hours or maybe more without resting. Building up superb local muscle endurance and resilience in the legs really helps with this process. In addition, an improved ability to derive energy from fat and training the muscles to store more carbohydrate (glycogen) can also help runners in the late stages of a marathon. Overall then, if you’re an amateur runner looking for a marathon PB, building up your zone 1 training volume is likely to pay greater dividends than focusing on high-intensity work!
References
1. Int J Sports Physiol Perform. 2014 Mar; 9(2):332-9
2. Int J Sports Physiol Perform. 2014 Jan;9(1):93-9
3. Int J Sports Physiol Perform. 2012 Jun;7(2):103-12
4. Front Physiol. 2014 Feb 4;5:33. doi: 10.3389/fphys.2014.000335
5. Front Physiol. 2014 Feb 4;5:33
6. Journal of Sports Science and Medicine (2019) 18, 708-715
7. Front Physiol. 2020 Nov 12;11:534688
8. Int J Sports Med. 2022 Apr;43(4):305-316
9. Sports Med. 2024 Dec 1. doi: 10.1007/s40279-024-02137-7. Online ahead of print
Andrew Hamilton
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