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).
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