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Training in Zone 2: building the base

What is ‘Zone 2’?

Zone 2 is the training intensity used to bring enhanced general aerobic fitness. It is training that is often associated with the phrase ‘building the base’. Without full development of this base, the rest of the training an athlete does has a very fragile foundation. Indeed, training in Zone 2 gives you the ability to withstand higher training loads (volume and intensity).

The upper boundary of Zone 2 is the ‘lactate threshold’. This is the first threshold, where blood lactate first starts to increase away from resting levels. Typically, this zone occurs between 55 and 70% of an athletes’ VO2max. The best way to identify your own lactate threshold is to visit a sports science laboratory, Dr Helen Carter explains the protocol for a lactate threshold test in this video. Alternatively, you can approximate your training zones with a simple field test, using either your heart rate monitor and/or your power meter.

Why should we use Zone 2 training?

Lactate_Threshold

Training in Zone 2 is important to build basic aerobic fitness, our endurance base. Most endurance athletes would benefit from spending a proportion of their time developing this base, regardless of event duration, or their fitness profile. Training in Zone 2 enables the athlete to ‘push up’ their lactate threshold from below. It is only when you have completely ‘pushed up’ the lactate threshold can you then switch over into Zone 3 to begin ‘pulling it up’ (as described in Pushing and Pulling). One of the biggest mistakes athletes (and coaches) make is to not fully exploit Zone 2: not doing so risks blunting the potential improvements in fitness, and also, exposes the athlete to breaking down with increased training loads later on in the periodised year.

A coach may suggest a longer period of time in Zone 2 when a rider’s strengths / weaknesses profile suggests its need. Elite cyclists can see their LT at 75% of VO2max, whilst the average club rider may struggle to pass 65%. Two athletes of the same VO2max expressing different lactate thresholds possess different endurance ability – the higher your lactate threshold, the harder you can exercise without producing lactic acid, and the longer you can withstand fatigue. The other scenario that may move a rider toward more Zone 2 training is when the chosen event speciality is between 3 to 5 hours: so longer road racing events, and longer distance time trialling (i.e. 100 miles).

A common use of Zone 2 training is when high volume / low stress training is needed. This can be when an athlete needs to lose fat mass, or when a break from higher intensity training is needed, without a compromise in endurance. The body is able to recover very quickly from Zone 2 rides – making it an ideal zone to use alongside other event preparation e.g. when an endurance event track rider is doing two sessions a day.

What part of the periodised year would I train in Zone 2?

The obvious place in the periodised year to use Zone 2 is in the transition time following the end of season break. Base miles may begin in November, and carry on into December – the Zone 2 work allowing aerobic fitness to be developed before the more serious Zone 3 / endurance capacity training enters the programme. Typically, an athlete would benefit from 10 to 12 weeks of training in Zone 2. The latter part of this block would begin to see integration of Zone 3 blocks. In practise, there are no hard and fast rules for periodisation and it is likely that zone 2 training will play a big part in any endurance athletes program throughout the year. At the 2010 PBscience Winter workshop, Dan talked through some of key considerations in planning your training in a presentation entitled Approaches to Periodisation.

What are the benefits to training in Zone 2?

In a recent study of endurance runners1, it was found that the training programme incorporating a greater proportion of Zone 2 type work lead to greater overall training gains in the 5 month period studied. And this is not uncommon. Indeed, a recent study in Sport Science laboratories at Brighton observed a 15% improvement in lactate threshold in just 6 weeks of Zone 2 type training! Even though most athletes have a higher initial fitness than those generally recruited to research studies, we could assume an improvement in physiological function will follow training of this type.

In one study of elite professional cyclists2, pre-competition training (which consisted of ~75% of sub-threshold training) brought about marked changes in the biochemical processes during exercise. Summarising the research literature of the past 30 years (some of which has used analysis of muscle tissue) endurance training (of the intensity equating to Zone 2) brings about the following physiological adaptations:

  • Increased plasma volume
  • Increased mitochondrial enzymes within the muscles
  • Increased capillarisation of the muscles
  • Increased muscle glycogen storage
  • Increased use of fat for energy production
  • Inter-conversion of fibre type towards slow twitch biochemical profile

All of the above bring about a reduced blood lactate accumulation for a given workload: predominantly by reducing lactic acid production in the muscle, but also possibly by increasing clearance of lactate from the system too.

Zone 2 may also prove to be a useful intensity to help freshen up an athlete’s psychological state. We may also see pedalling skills improved, and therefore improved efficiency. More on this in another PBscience factsheet! Essentially, we can see that adaptations from Zone 2 exercise help get the body best prepared for exercising regularly – optimising the engine. What we won’t see are improvements in other aspects of the system – so don’t expect to see your VO2max change very much after Zone 2 training blocks!

What can we expect from Zone 2 training?

In a standard base endurance ride, an athlete training in Zone 2 is likely to experience the following:

  • Requires a little concentration to maintain in the upper part of the zone
  • Breathing more regular than at low effort (zone 1) but conversation can be continued whilst riding.
  • A low sensation of leg effort whilst exercising, but awareness of ‘having done something’ immediately post ride
  • Quick recovery, and can soon repeat the same effort (as long as nutrition is taken care of).

Key factors to remember when using this training zone

Zone 2 is not a taxing training intensity in itself: the main challenges to the athlete arise during repeated sessions, and the accumulating effects. After all, if the training didn’t impact on you somehow, it would not be a training session! Keep in mind:Snow_riding

  • Nutritional aspects – training just under the lactate threshold is the intensity where fat oxidation rates are at their highest (at ~40g per hour). However, there is also a high reliance on muscle glycogen utilisation (upto 70g per hour). With the longer rides in this zone being 4 hours or so, by this point, the athlete will be challenging their carbohydrate stores. Indeed, exercise intensity (and therefore quality of training) will be compromised if the athlete neglects carbohydrate ingestion prior to- and during exercise. Look to take in about 60g of carbohydrate per hour.
  • Time between sessions – as the muscular stress is low (and little muscle damage is induced) the major consideration is regaining the energy you have expended (if energy balance is required). Ensure you focus on post session nutrition to optimise glycogen resynthesis. You should be ready to train again within 12 hours, and almost completely recovered within 24 hours.
  • Impact on other training – Zone 2 training should not compromise other training if you have built up to the set volume in a steady and progressive manner. Four hours is not overly challenging if you have adapted to 2 hour and 3 hour rides first. It is not uncommon for athletes to also be attending to weight training / general conditioning at the same time in the periodised year. In most cases, it is advisable to perform the conditioning work prior to your ‘on the bike’ session: in order to make sure you are not compromising conditioning work training with glycogen depleted muscles.

Typical sessions

Training in Zone 2 would involve sessions of typically 2 to 4 hours. Your training week may involve frequent 2 hour rides, but 4 hour rides may be used more sparingly (maximum 2 per week for the average club athlete). The coach may use this endurance base training to also work on other aspects of the athlete’s profile.

Session 1: Steady endurance ride, 2.5 hours

  • Ø 15 minute warm up progressing through Zone 1 to Zone 2
  • Ø 2 hours of working consistently at the top end of Zone 2, maintaining a constant effort up and down hills (variable speed)
  • Ø 15 minute cool down, returning to Zone 1.

Session 2: Steady endurance ride with blocks of cadence work, 3 hours

  • Ø 15 minute warm up progressing through Zone 1 to Zone 2
  • Ø 2 hours of working consistently at the top end of Zone 2, including 4 x 10 minute blocks at a cadence >100rpm. Have at least 15 minutes of normal pedalling between blocks.
  • Ø 15 minute cool down, returning to Zone 1.

You will often see Zone 2 blocks within other sessions throughout the year, therefore, it’s a good intensity to become familiar with!

REFERENCES

1.   Esteve-Lanao et al. J Strength Cond Res 2007, 21, 943-949.

2.   Lucia et al. Jpn J Physiol 2000, 50, 381-388.