What Science says: polarised training

Introduction

      How to train to perform well in races? In a nutshell “you have to train a lot and train smart” (Seiler and Tonnessen, 2009). While it is rather easy “train a lot” and find your limits before overtraining (because training volume is a one-dimension problem, if not optimally you either train too much or not enough), “training smart” is less straightforward because training modes are multiple: you can vary the training frequency, the activity type, the duration, the intensity, the number of bouts and the recovery between them if you do intervals, etc. One of the most discussed aspects of training is the intensity distribution. Should we train most of the time at a low intensity with occasional surges in intensity? Should we train most of the time at the intensity which corresponds to the race pace? In the recent years an intensity distribution called “polarised training” has been widely discussed, with many articles and books claiming that it is the optimal intensity distribution.

      Here I will review part of the scientific literature dealing with training intensity and polarised training. I do not want to give any advice on how you should train, but instead give you rationale information so that you can make choices about your training based on scientific evidence and introduce a discussion about the logic behind different training intensities.

What is polarised training?

      Scientific data on how athletes train are hard to obtain. Professional athletes and their coaches are reluctant to alter training for the sake of science because decreased performance due to a less efficient program could compromise a season or a career. Sufficient sample sizes are hard to get because of this and because of inclusion criteria (did the athlete complete the whole program? Did he record a sufficient amount of data?), so even if differences are found between training programs statistical significance is not always reached because of small number of subjects included in the analysis. These issues are part of the reasons why studies describing the training of elite athletes emerged only recently, more or less since early 2000s. The training intensity distribution of athletes is often reported according to a three zones classification based on heart rate recordings. Zone 1 contains efforts below the aerobic threshold, zone 2 efforts between the aerobic and anaerobic thresholds and zone 3 efforts above the anaerobic threshold. Although this classification is much simpler compared to the actual zones used by athletes and coaches during training (up to 8 zones, Seiler and Tonnessen 2009), the zones boundaries are linked to true physiological changes in metabolism and make comparisons between studies less arbitrary.

      Descriptive (contrary to experimental) retrospective studies have monitored the training of elite level athletes of various sports: cross-country skiing (Seiler and Kjerland 2006, Tonnessen 2014), rowing (Fiskerstrand and Seiler 2004, Guellich 2009), running (Billat 2001) and cycling (Lucia 2000, Schumacher and Mueller 2002, Zapico 2007). The training intensities of these athletes show two main types of distribution. Some studies (Seiler and Kjerland 2006, Fiskerstrand and Seiler 2004, Guellich 2009, Billat 2001) show a polarised distribution, that is to say a distribution looking like 75 % of time in zone 1, 5 % in zone 2 and 20 % in zone three or 75/5/20. The other studies (Tonnessen 2014, Lucia 2000, Schumacher and Mueller 2002, Zapico 2007) show a pyramidal distribution, something looking like 75/20/5. It is important to note that among these four studies that show a pyramidal intensity distribution, three of them we conducted with cyclists. To my knowledge there are no other retrospective analyses of how elite cyclists train, so the scientific literature suggests that in general, elite cyclist training follows such a pattern. Of course, training is periodised and the intensity distribution varies along the year, with the competition period putting emphasis on zone 3 (Tonnessen 2014 reports a slighlty polarised distribution during the competition period).

Why some athletes do polarised training?

      An overlooked aspect of these retrospective studies is that most training happens in zone 1. Yes, a polarised distribution shows that a lot of training happens in zone 3 but most of it happens in zone 1 (up to 95 % as reported in Guellich 2009, and interestingly this was regardless of the training period). Additionally, an important information present in these studies is that elite athletes training volume is huge, and training volume is a primary determinant of performance (Seiler and Tonnessen 2009). To illustrate this point, Fiskerstrand and Seiler 2004 show that the annual training of international level Norwegian rowers grew from around 900 hours in the 70s to around 1100 hours in the 90s. The increase in volume was realized mainly through an increase in zone 1 training. These athletes also train following a polarised distribution, and this may be a strategy to achieve very high training volume while preventing overtraining. Similar conclusions were reached in reports studying Ironman athletes (Munoz 2014b). Far from being “junk miles” as sometimes claimed, the intensity reached in zone 1 by elite athletes actually corresponds to a high energy flux, similar to the VO2max or threshold of sedentary or intermediate athletes (Esteve-Lanao 2007).

      An experimental study reported by Stoggl and Sperlich (2014) prescribed different training distributions to elite athletes and monitored the progress before and after the training intervention. In short, athletes following a polarised training programme improved markers of endurance performance more than athletes following a threshold programme. The authors suggest that at this level, further performance enhancement are easier to achieve through increase in high intensity training because the volume of training is already close to the limit of what the people can take and any additionnal volume fails to provoke significant physiological adaptations. Polarised training would then appear as a strategy to enhance performance further by shifting the high intensity training from threshold to higher intensities and spending the remaining time below or at the aerobic threshold, as an active recovery. Training at threshold intensity is a powerful tool to enhance performance but at a high level it might have a poor risk/reward ratio if used to build up fitness, compared to VO2max intensities.

It should be noted that in certain sports (cycling ?) the race-relevant movement is best achieved at race pace, which is often close to threshold intensity in endurance sports. So despite the advantages of polarise training, for the sake of learning or refining motor skills threshold training has an important role.

Is polarised training good for everyone?

      Experimental studies using sedentary or moderately trained subjects showed mixed results. Some studies showed benefits from threshold training (Denis 1984, Londeree 1997), others compared a polarised program to a threshold program and showed greater performance improvement following a polarised program (Esteve-Lanao 2007, Neil 2012, Munoz 2014a). However, all studies acknowledge the importance of threshold training at some point of the training periodisation, so it should not be concluded threshold training is useless.

Important issues regarding the use of a polarised training program by sedentary (for health benefits) or moderately trained athletes are its practicability outside the laboratory without a coach and specific equipment (especially for sedentary who would not want to buy anything else than a pair of running shoes!), its benefits over the medium to long term (several months to several years) and its safety. Without coaching supervision, people tend to have their easy training too hard and their hard training too easy, making all training sessions fall into the same monotone intensity (Seiler and Tonnessen 2009).

      A study (Gillen 2016) compared the benefits of sprint interval training program (3x20 seconds all-out with 2 minutes rest) versus moderate intensity training (45 minutes at 75 % of maximum heart rate), with three training sessions per week for 12 weeks. Both training programs produced similar health improvements despite the fact that sprint interval training required 5 times less training time than moderate intensity training.

      It is well known that high intensity training triggers quick improvements in performance but on the other hand these improvement quickly reach a plateau, making such a strategy arguable over the long term (Seiler and Tonnessen 2009).

     Zone 3 training leads to increased risk of “cardiac events”, especially in people with a limited aerobic endurance basis, and increased risk of injury (https://www.acsm.org/docs/brochures/high-intensity-interval-training.pdf). For this reason it is usually advised to begin a training program with an adaptation period lasting a month or so, during which the intensity of exercise is gradually increased.

Conclusions

      Polarised training is a training strategy that is used by elite athletes of some endurance sports (running, rowing and cross country skiing but apparently much less frequently in cycling) and which may allow them to balance high training volumes with high training intensities while avoiding overtraining. Although it makes the most sense for high training volumes, polarised training has shown some benefits for less trained athletes, although the performance gains are likely to be limited if not accompanied by a subsequent increase in training volume, which is one of the most important determinant of performance. Moreover, the very high intensities asked by polarised training are difficult to follow by untrained or moderately trained people and require a very high motivation. Also, health risks exist (cardiac events, repetitive strain injury, etc).

References

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Denis, C., Dormois, D., and Lacour, J.R. (1984). Endurance training, VO2 max, and OBLA: a longitudinal study of two different age groups. Int J Sports Med 5, 167–173.

Espen Tonnessen, S.S. (2009). Intervals, Thresholds, and Long Slow Distance: the Role of Intensity and Duration in Endurance Training. Sportscience 13, 32–53.

Esteve-Lanao, J., Foster, C., Seiler, S., and Lucia, A. (2007). Impact of training intensity distribution on performance in endurance athletes. J Strength Cond Res 21, 943–949.

Fiskerstrand, A., and Seiler, K.S. (2004). Training and performance characteristics among Norwegian international rowers 1970-2001. Scand J Med Sci Sports 14, 303–310.

Gillen, J.B., Martin, B.J., MacInnis, M.J., Skelly, L.E., Tarnopolsky, M.A., and Gibala, M.J. (2016). Twelve Weeks of Sprint Interval Training Improves Indices of Cardiometabolic Health Similar to Traditional Endurance Training despite a Five-Fold Lower Exercise Volume and Time Commitment. PLoS ONE 11, e0154075.

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Stöggl, T., and Sperlich, B. (2014). Polarized training has greater impact on key endurance variables than threshold, high intensity, or high volume training. Front Physiol 5, 33.

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