What you train is what you get: About the rationale of training zones in endurance sports

Clénin German E.
Sportmedizinisches Zentrum Ittigen b.Bern, Ittigen, Switzerland

Introduction

Physical activity has clear benefits on human health in many different ways. Among the different types of activities, it seems to be aerobic exercise that is best suited to achieve metabolic and cardiovascular effects. Aerobic exercise such as endurance training brings health effects such as improved metabolism, reduced cardiovascular risk, and reduced all-cause mortality and cardiovascular morbidity and mortality [1,2,3,4]. Endurance sports are characterized by repetitive contractions of larger muscle groups for a certain duration [5]. Classical examples are running, cycling, swimming, walking and hiking in summer, and cross-country skiing, ski-mountaineering, snowshoeing and winter-walking in winter.

On a regular basis before duration before ­intensity

Depending on the discipline endurance training is easy to access and practice, e.g. put on your running shoes or take your bike and off you go. Training starts from the very first minute. But how about frequency, duration and intensity?
For endurance sports it is important to practice on a regular basis. Two to three times per week seems to be a reasonable approach, as time for recovery is certainly sufficient and a training effect with supercompensation can be expected. When an athlete progresses with the number of training years this frequency can continuously be developed and raised to much higher numbers of training sessions per week, in elite sports eventually up to two training units per day [6,7].
Duration for an endurance training starts with the first minute. But logically it is a duration of around 20min which is needed to have a certain effect on the metabolic, musculoskeletal and cardiovascular system. From there one may develop the duration of training further up to 30min, 45-60min and so on.
If it comes to put things in a good order it is as mentioned above: Training practice on a regular basis is the most important. Then duration of the training can be developed progressively. And after that intensity can be addressed [8,9].

Five zones of intensity – where do they come from?

As figure 1 shows physiologically three ranges may be differentiated:
I. Until the Aerobic Threshold (AeT)/Ventilatory Threshold 1 (VT1)
II. In between AeT/VT1 and Anaerobic Threshold (AnT)/Ventilatory Threshold 2 (VT2), MLSS (maximal lactate steady state)
III. Above AnT/VT2/MLSS

However, in training practice it is a five-zone model which is largely used in many endurance sports [10,11]. In cycling, especially since power measurement on the bike came in, it is exceptionally even a seven-zone model [8].
In the mostly used five zone model the initial three ranges are refined and split into the five zones: Range 1 forms Zone 1 and Zone 2. Zone 4, anaerobic threshold, as it is particularly important, has its own zone [12]. Zone 3 in between Zone 2 and 4. And eventually Zone 5 above and beyond anaerobic threshold. Figure 1 and figure 2 are based on the same test data and allow this direct comparison and transition from three ranges to the five zones.
Table 1 explains the expected heart rate (in % of max HR), lactate levels and typical effective work time within the intensity zone. As lactate production is very individual and depending on muscle fiber composition (fast twitch fibers producing higher amounts of lactate) as well as on the sports discipline lactate levels may vary a lot and need an individual approach [12]: Athletes with a high percentage of slow twitch fibres, having practiced endurance sports for years may have a lactate range (resting to max values) of 0.8– 6mmol/l, the majority of athletes overall a range of roughly 0.8–12mmol/l, and athletes with a reasonably high amount of fast twitch fibres, with a training over years in long sprint disciplines (e.g. 400m, 800m) a range of 0.8–18mmol/l [8,12].

What is trained in what zone?

The five intensity zones as described above differ in muscle metabolism, impact and consequences on the locomotor, metabolic, cardiorespiratory, and fuel system and on neuromuscular stimulation and recruitment. In training planning and development of athletes’ performance this knowledge on expected adaptations is intentionally used in order to progress [8,11,13]. Please compare for this purpose Table 2.

Zone 1, the so called “active recovery” zone isn’t the most attractive, but it’s quite foundational for structural adaptations, movement patterns and technique. It lies also an aerobic foundation, especially when done with volume and intention.
Zone 2, the zone of “aerobic endurance” is essential for all endurance sports. It’s the intensity which fosters most capillarisation of working muscles as well as density of intracellular mitochondria. As fuel system is fat oxidation predominant. It is the zone which is responsible for the infrastructure of an endurance athlete’s performance.
Zone 3, or “transitional zone” is as the name tells in between aerobic endurance and anaerobic threshold. Fuel wise still predominantly aerobic with still a reasonable percentage of fat metabolism but carbohydrate burning (glycolysis) is ramping up. As it is an intermediate thing Zone 3 is also called the grey zone and for instance in the polarized training model athlete leave this zone intentionally out. However, when done intentionally it may improve aerobic power and tempo control on this very specific level.
Zone 4, the famous “anaerobic threshold” zone is the zone where a typical competitive rhythm, speed or performance can be hold for 30min, in well trained individuals longer. The fuel contribution is mixed, aerobic and anaerobic, it therefore fosters lactate clearance. As the movement pattern, metabolic demand, neuromuscular stimulation are all close to what is asked in competition this threshold pace is very interesting for athletes [14,15].
Zone 5, the so called “VO₂max” or “anaerobic power” zone. The lactate formation is maximal, neuromuscular stimulation and recruitment, too. Fuel wise it is primarily anaerobic glycolysis with little aerobic contribution running the engine. And yes, it increases VO₂max as it recruits high threshold motor units and brings all performance relevant systems to their critical limit [14,15].

What is the optimal distribution to be successful?

In health promotion the main goal is to find people’s motivation to get them moving. It is about practising moderate activity on a daily basis, e.g. thirty minutes five times per week, and if possible, find with them a sport discipline that suits them for 2-3 times per week. Focus is clearly on practising physical activity on a regular basis, continuously.
In recreational sports things may be started: It is the frequency on a regular basis which is key: Three times per week if possible. Admitting that the person is ready to invest three hours per week for three training session, a proposition might be to plan three training sessions of one hour each in zone 2. Zone 2 forms the training zone, where the foundation for endurance sports is laid: Angiogenesis (capillarisation), mitochondrial biogenesis, as well as glucose and fatty acid transporters from the blood into the muscle cell are mediated by endurance training in general, in particular in doing so repetitively on aerobic endurance level (zone 2) [7,16]. It seems however obvious that already by varying slightly the duration, one longer run of 80min, one of 60min and one of 40min, and choosing zone 2 for the first two and zone 3 or 4 for the last may be more efficient for training adaptations as a progressive slight overload and a variety provide a novel and better stimulus. Training is furthermore more attractive and interesting for the athlete.
In ambitious recreational sports and elite sports, the question of optimal training distribution is since many years and continuously debated and content of many publications [10,11,14,15,16,17]. Getting the balance perfectly right seems to challenging. A couple of general guidelines are: Athletes are responding individually, but even on this level frequent low intensity and longer duration training is effective in stimulating physiological adaptations. An 80:20 percent ratio of low (Zone 1, 2, 3) to high intensity training (Zone 4 and 5) is common and shows excellent results among endurance athletes. For tolerating and responding well to a progressive and substantial increase in training intensity over the short term there is a basic endurance base built from high training volumes needed [16,17]. High intensity type of specific exercise is a critical component of all successful endurance athletes, two units per week appearing to be the optimal positive stimulus [10,11].

Practical counselling by the sportsmed physician

In a sports and exercise medicine clinic there are many opportunities to do training counselling after injuries or illnesses with athletes, or individuals looking for advice as they want to start a recreational training program or, last but not least, even sedentary patients asking what to do next to improve their health issues. Clearly, also in training counselling practice makes perfect, therefore it is beyond the scope of this article to be able to do training counselling for ambitious or even elite athletes as there are specific skills and a lot of experience needed. However, have a look at the practical examples below, where in A a health promotion person, in B a recreational athlete, and in C an elite athlete is presented.

Practical examples

A) 45y old overweight lady, wants to lose some weight and to get a bit more active. Up to now, no structured physical activity. She likes dancing and to move with music (HEALTH PROMOTION).
On a regular basis: –Try to plan a weekly training program 2-3 times sport activities, as a dancing lesson (e.g. Zumba) and two walking sessions, possibly nordic walking if interested
Duration: Zumba 1h, 2 x Walking or Nordic Walking 30-45minutes
Intensity: Not important yet. Possibly, if interested, ­explaining the five zones and recommending Zone 2.

B) 38y recreational runner, wants to run on a regular basis popular road race like the Kerzerslauf, GP of Berne, Murtenlauf etc. Is ready to train 3-4 times per week (RECREATIONAL LEVEL).
On a regular basis: Plan four training session per week: one long jog, one extensive run, one unit with focus on intensity, and one last combined unit (running and strength) with a focus on core stability, trunk muscles and legs.
Duration/Intensity:
– long Jog 90min in zone 2,
– one unit focusing on intensity (Zone 4 or 5) – warm up 15min – e.g. 4x 4min interval with 3min of pause in between, cool down 15min
– one-unit 60min in zone 2
– one combined unit, 15min running Warm-up Zone 1, 45min strength with focus on core stability, trunk and leg muscles. 10min cool down zone 1.

C) 23y female orienteering runner, national level, training 9 times per week, total of 11 training hours, of this 7h running (6units), one strength training, two alternative endurance units (ELITE LEVEL).
On a regular basis: – Weekly training program with these 7h of running in 6 units. Plan one rest day, without any training at all. One long jog of 90min, one day with two running sessions (one very easy, and one a Zone 5 session) and another day with a Zone 4 unit. Try to separate these heavier training loads with a calmer day in between. Try to respect the 80%–20% rule. This means 80% of training time mostly in Zone 2 (possibly also Zone 1 or 3) and 20% of training time in Zone 4 or
Zone 5.
Duration/Intensity:
– Long jog 90min, Zone 2
– Two other extensive runs of 60min, Zone 2
– One unit focusing on anaerobic threshold (Zone 4), 15min warm-up, 30-40min at the anaerobic threshold, 10min cool down – (in weeks with competitions, the competition may replace this unit)
– One unit focusing on speed, running above threshold (Zone 5), 15min warm-up, 4 times a series of 10 repetitions of 15 sec-15sec-15sec- etc alternating high-speed running vs leisurely moving.
– The same day as this zone 5 unit an easy run, zone 2, of 30-45min.

Proposition of a training diagram for counselling

In table 3 you find a diagram or little algorithm which lines out the most important steps in training counselling in endurance sports. It first asks what the person is already doing, what the goals are and the available time. It points out the important passages within endurance training, leads through the training zones with the possibility to add individual values, e.g. for heart rate or pace. It then ends with the space to write down and fix the next three steps to put things in practice.

Corresponding author

German E. Clénin, Dr. med. et MME
Sportmedizinisches Zentrum Ittigen bei Bern
Haus des Sports, Talgutzentrum 27, 3063 Ittigen
http://www.smzbi.ch
german.clenin@smzbi.ch

References

1. Ekelund U, Ward HA, Norat T, et al. Physical activity and all-cause mortality across levels of overall and abdominal adiposity in European men and women: the European Prospective Investigation into Cancer and Nutrition Study (EPIC). Am J Clin Nutr 2015; 101: 613–621.
2. Joyner MJ, Green DJ. Exercise protects the cardiovascular system: effects beyond traditional risk factors. J Physiol 2009; 587: 5551–5558.
3. Lavie CJ, Arena R, Swift DL, et al. Exercise and the cardiovascular system: clinical science and cardiovascular outcomes. Circ Res 2015; 117: 207–219.
4. Lee DC, Pate RR, Lavie CJ, et al. Leisure-time running reduces all-cause and cardiovascular mortality risk. J Am Coll Cardiol 2014; 64: 472–481.
5. Morici G, Gruttad’Auria CI, Baiamonte P, Mazzuca E, Castrogiovanni A, Bonsignore MR. Endurance training: is it bad for you? Breathe (Sheff). 2016 Jun;12(2):140-7. doi: 10.1183/20734735.007016. PMID: 27408632; PMCID: PMC4933620.
6. Hausswirth Ch, Y. Le Meur. Physiological Demands of Endurance Performance. 2012 in Endurance Training Science and Practice by Inigo Mujika, Vitoria Gasteiz, Basque Country, 3–10.
7. Coffey V.G. The Molecular Bases of Endurance Training Adaptation. 2012 in Endurance Training Science and Practice by Inigo Mujika, Vitoria Gasteiz, Basque Country, 119–126.
8. Manual Leistungsdiagnostik, Swiss Olympic, Ittigen b. Bern, 2015.
9. Wehrlin J. Auf dem Weg zur richtigen Intensität. Mobile 3/02, Magg­lingen, Switzerland. 10–13, 2002.
10. Seiler S. Training Intensity Distribution. 2012 in Endurance Training Science and Practice by Inigo Mujika, Vitoria Gasteiz, Basque Country, 29–39.
11. Seiler KS, Kjerland GØ. Quantifying training intensity distribution in elite endurance athletes: is there evidence for an “optimal” distribution? Scand J Med Sci Sports. 2006 Feb;16(1):49-56. doi: 10.1111/j.1600-0838.2004.00418.x. PMID: 16430681.
12. Clenin G.E. Leistungsdiagnostik im Ausdauersport – anaerobe Schwelle, VO2 max, aerobe Kapazität – wohin geht die Reise? Swiss Sports & Exercise Medicine, 67 (1), 6–14, 2019.
13. Pyne D.B., P.U.Saunders. Testing and Assessing Adaptation to Endurance Training. 2012 in Endurance Training Science and Practice by Inigo Mujika, Vitoria Gasteiz, Basque Country, 183–190.
14. Kenneally M, Casado A, Santos-Concejero J. The Effect of Periodization and Training Intensity Distribution on Middle- and Long-Distance Running Performance: A Systematic Review. Int J Sports Physiol Perform. 2018 Oct 1;13(9):1114–1121. doi: 10.1123/ijspp.2017-0327. Epub 2018 Oct 18. PMID: 29182410.
15. Campos Y, Casado A, Vieira JG, Guimarães M, Sant’Ana L, Leitão L, da Silva SF, Silva Marques de Azevedo PH, Vianna J, Domínguez R. Training-intensity Distribution on Middle- and Long-distance Runners: A Systematic Review. Int J Sports Med. 2022 Apr;43(4):305–316. doi: 10.1055/a-1559-3623. Epub 2021 Nov 8. PMID: 34749417.
16.  Hegner J., Training fundiert erklärt: Handbuch der Trainingslehre, Ingold Verlag 2009.
17. Schütz R. Orientierungslauf, Laufen. Broschüre J+S, BASPO, Magg­lingen, Switzerland, 2018.