Home A column by Michael Beisty The Mature Distance Runner: Fundamentally Speaking Part Two: The Anaerobic Threshold

The Mature Distance Runner: Fundamentally Speaking Part Two: The Anaerobic Threshold

September 9, 2024

Disclaimer: Content herein does not constitute specific advice to the reader’s circumstance. It is only an opinion based on my perspective that others may learn from. Anyone of any age who engages in running should be in tune with their body and seek medical advice before embarking on any intensive activity (including changes to said activity) that may unduly extend them. This is critical should the aspiring athlete have underlying medical conditions and/or ongoing health issues requiring medication.

‘The bottom line is that training intensely is the key to success in sport, regardless of the age of the athlete.’ (Peter Reaburn PhD 2009)1

In this article I attempt to provide information in a simple fashion and minimise overly technical descriptions of physiological processes. To assist those who want a very high level of detail, I point you to the reference/sources listed at the end of the article.

There is some overlap between this topic and my previous article about the aerobic threshold. I apologise in advance for some minor repetition of content.

Introductory Information

Anaerobic threshold is, seemingly, a well understood concept. The focus on this threshold could be described as excessive in the world of middle-distance running, viewed by some as a shortcut to exceptional performance outcomes. Training at, or above, this threshold is a key consideration in the programs of all distance runners. In this article I identify aspects of the anaerobic threshold that may require attention as we age, and its application to training.

The personal views expressed in this article relate primarily to training for the 5 km to half marathon, which is the focus of my Soft Quality Program (SQP). Training for middle distance events and longer distance races like the marathon require different perspectives.

As a point of reference, in general, there are three methods of doing exercise2 that are relevant to the anaerobic threshold and assumed in this article:

Continuous running with no break or change in intensity;
Continuous-interval running with a change in intensity; and
Stop-start interval training where there are sets, reps and rest periods.

What is the Anaerobic Threshold

As stated in my previous article of the Fundamentally Speaking series, in exercise training terms a threshold is a level of effort that causes a physiological adaptation within the body and improvement in performance.3

The anaerobic threshold is where blood lactate increases rapidly, at a rate in excess of the body’s ability to remove it.4 It is also known as the inflection point or lactate threshold, and is the uppermost threshold of the aerobic training zone. It is the ‘highest sustained intensity of exercise for which measurement of oxygen uptake can account for the entire energy requirement.’

Anaerobic threshold training will improve a runner’s ability to breakdown and remove lactic acid (and tolerate hydrogen ion buildup), and is conducted at 80-85% of maximal heart rate (MHR).5

Reaburn6 explains anaerobic threshold in the following relatable terms: ‘This is the percentage of the athlete’s aerobic capacity that can be used at race pace – what I call the “hurt but hold” intensity……Above this pace the muscles start to produce lactic acid that upsets the muscle contraction process and slows the breakdown of carbohydrate so that energy production is compromised.’ He considers the anaerobic threshold a better predictor of endurance performance than VO2max.

Janssen notes7 that the resting heart rate, maximum heart rate, and the anaerobic threshold, all decrease linearly with age. A life trend that is immovable.

Tom Courtney outlasting Derek Johnson, with Audun Boysen and Arnie Sowell close behind.

On a semi-related note, I love the graphic description by Tom Courtney about how the onset

of extreme ‘lactic’ can actually feel in the fire of competition. Of the last stages of his 1956 Olympic 800 metres win he wrote: ‘It was a new kind of agony for me. My head was exploding, my stomach ripping and even the tips of my fingers ached. The only thing I could think was, “If I live, I will never run again.”’⁸

Research Studies

While research is occurring about exercise, cardiovascular and respiratory health, and older persons, there is a lack of evidenced based research about elite mature age endurance athletes and high intensity training.

By way of example, a review and meta-analysis conducted by Wu et al ⁹ examined the effect of high intensity interval training (HIIT) on healthy adults over 60 years of age. A range of health and fitness factors were considered, including peak oxygen consumption, VO_2peak (the highest amount of oxygen consumed at peak exercise). This review involved a literature search of scientific articles up until 25 July 2020. Some caution is warranted here, as the review excluded ‘high level’ athletes. HIIT was defined as training with intermittent bouts of activity conducted at 85% MHR.

It was found that HIIT substantially improved VO_2peakcompared to moderate intensity continuous training (MICT). It was also found that training periods >12 weeks, training frequencies of 2 sessions/week, session lengths of 40 minutes, 6 sets and repetitions, training times per repetition of >60 s, and rest times of <90 s were more effective for VO_2peak.

In my last article I also mentioned an extensive scoping review of research literature that captured 69 studies conducted since 2009, with a participant mean age of 65 and over (men and women), across a range of exercise modalities.¹⁰ This review cited that ‘HIIT can be an effective means of improving aerobic fitness in older adults, and that it may confer a small advantage over traditional endurance training.’ The authors went on to say that this was consistent with the literature about non-elderly adults that showed ‘HIIT may have a small benefit when compared to MICT on improving VO_2peak but that this improvement is likely to be increased by longer intervals and greater work to rest ratios, and in older or less fit subjects.’ Again, caution is warranted interpreting these results, as HIIT was not a clearly defined exercise protocol for the scoping review. In other words, there was considerable variability in the type of HIIT within the studies considered – in terms of length of intensive exercise, length of rest breaks, number of repetitions, frequency, and modality of exercise.

These two extensive reviews did not include elite endurance athletes. Instead, they examined the application of HIIT in elderly populations more generally, some healthy and active, and some not. The combined outcome of these reviews was that HIIT results in a discernible increase in VO_2peak, either substantially or marginally above increases gained from MICT or continuous aerobic activity.

Given the reviews were examining different participant sample types, with a wide variation of HIIT types, at best, I can only surmise that a similar physiological outcome may apply to elite mature age endurance athletes on some level? ie Engagement in HIIT = increase in VO_2peak.

A Masters Translation

4.1 Training Framework – The Zones

Many coaches and physiologists promote the use of training zone systems. The most prominent of these systems are based on power (functional threshold power or FTP), heart rate (lactate threshold heart rate or LTHR) and perceived exertion (PE).¹¹

I have noticed a preoccupation with heart rate training zones among the mature age cohort. This is understandable given the broader community emphasis on healthy ageing and support for a controlled and cautionary approach to exercise. Within the endurance fitness realm, it fits nicely within a concept of scientific training, the use of heart rate monitors and lactate readings guiding training sessions and the effort needed to achieve a particular training effect. The linear relationship between intensity and heart rate also makes it an attractive proposition for many.¹² So, logically, as a mature age competitor, I understand the reasons for such an approach. However, my personal preference is to rely on perceived effort, or feel, to gauge the intensity of my training. While no less valid, in this era of technology with a manic focus on performance measurement, I know that perceived effort can be difficult for some competitive mature age runners to come to terms with.

It must be said that there is plenty of variation in heart rate even for athletes of similar ability, of the same age, so use of heart rate-based training is highly individualistic. Despite my personal misgivings about the adoption of a heart rate training zone system, for the purpose of this article, it is useful to have this discussion, while referencing it against the anaerobic threshold. Peter Reaburn¹³ in his book The Masters Athlete, covers heart rate zones in an easy-to-understand manner. I have summarised the cogent points below (using ‘repetitions’ in place of the colloquial use of the term ‘intervals’):

Zone 1 is the recovery zone, low intensity and short duration.

Zone 2 is long slow distance or the aerobic ‘conversation pace’ zone, in the 65-75% of MHR range.

Zone 3 is the extensive endurance zone, performed at 75-80% MHR for long periods, that includes longer distance runs of 10-30 km and longer sets of repetitions. Usually conducted during preparatory phases.

Zone 4 is the ‘strong but comfortable’ intensive endurance zone, just below the ‘hurt but hold’ zone, previously described in this article. It is performed at 80-85% MHR, and duration is reduced. It includes shorter long runs of 5-20 km and more intense repetitions. Again, this is during a preparatory phase of training.

Zone 5 is the ‘hurt but hold’ intensity zone, at anaerobic threshold, performed at an elevated rate of 85-90% MHR. It includes continuous runs of 20 to 60-90 minutes and repetition training with short interval recoveries (half or less duration than the repetitions). And is performed, at the most, twice weekly.

Zone 6 is maximum aerobic training, with reduced volume of sessions, less repetitions but very high intensity, faster than planned race pace (90-100% MHR), and with long interval recoveries. Typically employed in the final pre-competition phase.

Zone 7 is speed training.

Zones 5 to 7 demand adequate recovery strategies to maximise the training effect.

[Note: There is some variation in description of the zones by different practitioners, and what they mean, particularly when referring to zones 4 and 5. For instance, some readers may be more familiar with the description of the seven zones as: Active Recovery, Endurance, Tempo, Threshold, VO_2max, Anaerobic Capacity and Neuromuscular Power.]

4.2 Implications for Training

4.2.1 The higher the training intensity above the anaerobic threshold (called the anaerobic training zone and described as lactic training) the greater the physiological adaptations. When combining a suitable mix of aerobic and anaerobic training this inevitably increases the workload for your lactate inflection point and your aerobic capacity.¹⁴

As you transition through the zones physiological adaptations occur, the most prominent being an elevation of VO₂max, a raising of the anaerobic threshold (and therefore tolerance to lactic acid), and improved speed endurance. As suggested by Reaburn, the art in all of this is to determine the optimal mix of faster work, having regard to frequency (how often?), intensity (how hard?), time/volume (how long?) and type (what to do?), abbreviated as FITT.¹⁵

4.2.2 I like Peter Magill’s comments about training for masters runners.¹⁶ He puts it in very simple terms: ‘There are no super-secret adjustments or workouts for masters runners. We have to do the same training as younger runners – just a little less of it, at a slightly reduced intensity, with a little more time between hard workouts.’ I agree with this sentiment and do not shy away from the need to conduct high intensity sessions. However, as many authoritative practitioners have indicated, by extension a degree of nuance is required as we travel through each decade, with appropriate tailoring of training programs to mitigate the risks that ageing can bring.

In addition, Friel states that high intensity training is more likely to reduce excess flab than long slow distance, and is beneficial for body composition and race results. Such workouts promote the production of anabolic steroids and burn more calories, and are particularly effective when combined with high-load strength training.¹⁷

4.2.3 Ideally, an optimal mix will support a progressive overload on your body and ensure adequate recovery. Working out this mix for the mature endurance athlete will depend upon individual capacities, gender and ageing considerations. For the sake of sustainability, and to mitigate overtraining and the risk of injury, I favour an overall conservative approach that supports gradual improvement in fitness and performance levels.

4.3 A Practical Application

4.3.1 Reaburn recommends the ageing athlete train largely in zones 2-4, transitioning into zones 5-7 depending on competition preparation and racing phases. He uses the caveat that higher intensity training in zones 5 and 6 should only ever be conducted by ‘healthy ageing athletes who have no cardiac risk factors, a training age of 2-3 years, are not prone to overuse injuries, and who have undertaken an extensive foundation phase.’¹⁸Indeed, on a personal note, to minimise the risk of cardiac complications in my sixties, I have dispensed with continuous ‘at threshold’ and tempo training runs and focus moreso on interval/repetition training.

Though races aren’t training, I have to acknowledge that when able, I race distances on the track of 2.4 km to 5 km at my weekly (Tuesday night) Newcastle Veterans Athletics Club competition. While they are low key events, I race hard, and you could argue that this equates to an anaerobic threshold training effort. I love to race and these short events help to develop superior endurance fitness for those longer efforts of 10km to half marathon that I participate in, only four times per year. They are also a useful means to gauge progression. In a Complex system such as my SQP, they are part of the ongoing program build. Sometimes they are a sharpener for an upcoming weekend peak race. And, if managed carefully when returning from injury, they can assist in a gradual return to form.

From Reaburn’s description of heart zone training, zone 3 is where faster repetitive work or interval sessions are introduced. My personal preference in my sixties is to largely conduct faster work in what I think is zone 4, based on my perceived effort, occasionally straying into zone 5. Zone 4 is what I call rhythm sessions. Typically, I use short rest intervals between repetitions. In my fifties I was doing more sessions in zone 5 and straying into zone 6.

Remaining in zones 4 and 5 requires patience in the development of speed endurance, resulting in the necessary physiological adaptation to deliver improvements in race performance. While zone 6 sessions can result in breakthrough performances as part of phased approaches, they can be a tipping point to overtraining and burnout if overdone, and/or if the aerobic base is low. The return on investment of this type of training is finite, and runners walk a fine line in finding the right balance.

My view, after much reading and plenty of practical experience, is that we tend to overdo the amount and extent of lactic training. Many of the practical philosophers point to the aerobic engine as the key driver of endurance fitness, aerobic training being the default for physiological renewal if overtraining occurs. And that lactic training is only required in very small doses during key phases of training, prior to peak racing periods. As Lydiard has said ‘No one will burn out doing aerobic running. It is too much anaerobic running, which the American scholastic athletic system tends to put young athletes through, that burns them out.’¹⁹

I remind the reader that interval training does not have to be done on a track. In actual fact, I do these sorts of sessions on flat dirt and grass trails, grass lands, football ovals and fields. I sometimes use non-conventional distances for reps like 530m, 670m, 180m, 330m etc to best fit my surroundings. It is the effect that is important, not the exactness of distance or the running surface. Running in a more natural environment, often in quiet settings, can assist in the enjoyment of your faster sessions. You tend to be more relaxed. Even moreso if you are not preoccupied with timing your sessions and you focus on listening to your body throughout the session.

4.3.2 Pure Speedwork

With increased age I have introduced regular alactic or pure speedwork sessions, as I have jettisoned the lactic sessions. These sessions entail bursts of 7 to 20 seconds at 98-99% maximum effort, with very long rest breaks to enable adequate recovery. The shortness of the reps means there is minimal, if any, lactate produced. While they are not all out sprints at 100% maximum effort, they are very fast, and there is a risk of injury should the mature runner not complete an adequate warm up. However, allowing for a period of adaptation, pure speedwork is a useful training strategy to develop an ability to run and relax at top speed.

The inclusion of pure speedwork can be a bonus for the mature athlete. It can be a less mentally taxing faster session that provides some variety in training, enabling the mature athlete to sneak in an extra quality session to their program on a weekly or fortnightly basis. It can also be interchanged with short hill reps and fartlek over undulating parklands that provide added strength work. While I support a lesser frequency of higher intensity work in the seventh decade/sixties, say one interval session per week, the introduction of speedwork is a value-added session that can reap significant benefits for racing performance. So, assuming the mature athlete is healthy, and not taking medication, an optimal training week in their sixties could be:

1 x short race (upper limit of 5km at a parkrun or local Masters track race), noting that this could revert to fortnightly or three-weekly in different phases;
1 x interval session (zone 4 or 5 depending on phase of training); and
1 x pure speedwork session (zone 7).

Reaburn²⁰ stresses the importance of ‘speed’ training for ageing athletes and describes how it enables the hard wiring of your brain to your muscles required for sprinting. He observes that ageing athletes tend to train at lower intensities and virtually never activate the fast twitch type II fibres found in sprinters, losing whatever capability that may have existed. He notes that speedwork ‘can help the ageing muscle and nerves to fire quickly.’ This means that when competing the mature endurance runner can better cope with distance racing speeds that are much slower than ‘sprint’ pace. I have found this to be true in my own racing, where the introduction of weekly speedwork sessions have brought me on relatively quickly, enabling me to race faster over 5km than I would have otherwise expected. And finding the race pace comparatively less demanding.

I also acknowledge that if you are not performing higher end anaerobic work, the introduction of pure speedwork can be challenging, because the neuromuscular adaptation required will be significant, a ‘shock to the system’ as you fire up your fast twitch sprinting fibres. This can result in a feeling of ‘clunkiness’ in your running for a few weeks while you transition to regular zone 7 speedwork. It also requires careful management. You need to have your antenna up for any inklings of potential leg injuries, and discomfort in your groin/lower abdomen and buttocks. However, based on my personal experience, I think the risk is worth the potential benefits.

Commonsense

One of my basic tenets of training has always been the need to exercise commonsense. With this in mind, I refer the reader to some advice from Reaburn that relates to FITT. At the risk of taking things out of context, I particularly like these excerpts from his Seven Deadly Mistakes Made by Masters Athletes²¹:

‘If there is one lesson I have learnt over the years, it’s how important the principle of ‘progressive overload’ is. Too many older athletes, particularly those new to sport or not having trained for years, train too hard, too long or too often….The key? Progressively increase how long, how often and how hard we train, and in that order.’

‘…intensity also brings with it tiredness, fatigue and an increased risk of injury. Prepare the body well for the hard work by developing a good base, getting the muscles and joints strong and then progressively building the intensity.’

‘…the stress response of exercise and life are the same. Thus, during times of psychological stress, cut back on the intensity, duration or frequency of training and, from my experience, in that priority order!’

‘While it’s great to train and be pushed in groups, there are times when we need to “do our own thing” and that thing is what our own bodies are telling us, not our minds!’

Concluding Comments

If you have reached this section, you will have found that I have broadly addressed some of the aspects of FITT. I don’t think it’s necessary to designate a percentage figure for an optimal proportion of high intensity training versus aerobic training, or a definitive split of zone 4 to zone 7 workloads. I think it is safe to say that at a base level, there is evidence that some form of high intensity interval training contributes to an increase in VO_2peak and aerobic capacity for older persons.

For competitive distance runners it is obvious that the shorter the racing distance the greater the need to perform some anaerobic threshold and above training. What that means for the total volume and extent of this type of training session will depend on ageing factors, gender and individual capacities. For a mature age distance runner, I think it is better to settle on a routine that includes a commitment to regular faster sessions, on some level. While the use of interval training to improve speed endurance consist of short reps (30-90 seconds) with short rest intervals (half or less the rep time) sessions²², if engaging in very high intensity interval sessions a good rule of thumb is to reduce the number of repetitions, and ensure adequate rest intervals between each rep.

In a previous article about Quality, I discussed in practical terms some related issues about high intensity training. Two years later my views about anaerobic threshold training remain unchanged for a mature athlete, namely that higher intensity should not extend to excessive use of lactic training within a Complex system. I support a gradual reduction in the use of lactic sessions moving through the M/W40 decade, favouring speed endurance training and anaerobic threshold sessions as an M/W 50 and beyond, complemented by pure speedwork, with just a dash of the anaerobic zone 6 work to hone race performance.

The trade-off for the virtual exclusion of zone 6 equivalent training is a more gradual progression of endurance fitness by a raising of the base aerobic threshold, a much slower increase to the anaerobic threshold and sustainable improvements in racing performance. Ultimately, I suggest that with increasing age from your fifties onwards it is a safer option to stay within zones 4 and 5 for high intensity work, primarily engaging in sub anaerobic threshold sessions rather than anaerobic lactic.

When you think about it, what I propose for a mature age runner is not too dissimilar from the training system used by the Ingebritsens’, which is characterised by high volume, moderate threshold-based interval training, and a small amount of high intensity speedwork. Albeit on a much-reduced scale, and age appropriate.

Though I am less enamoured by their use of lactate monitors and constant physiology testing, preferring to train based on perceived effort. And instinctively, I rail against the use of set ratings that are applied to the Perceived Exertion training zone system, instead opting for a more natural free-wheeling approach to intensity.

But then again, that’s just me.

References: