Training Zones Explained (updated)
Training Zones Explained:
By Andy Newell
Cross-country ski training relies on the training zone model more than most endurance sports. Why? Ski racing has more variables than most endurance sports.
We don’t compete on a track, pool, or road where the surface or environment can be controlled. There is no such thing as an Olympic standard kilometer pace in cross-country skiing to measure ourselves off of. Snow conditions are different every race and most race loops have a wide variety of climbing and decent.
Combine these variables with the fact that skiing has two very different techniques, classic and skate, terrain variations among venues, and we are left with a sport that is extremely hard to measure.
These factors make it difficult to correlate a specific pace to a specific effort on skis. This is why skiers use training zones (or Levels) to guide sessions and as a tool to track our yearly training.
While there is some variation globally, skiers use 5-7 training zones (levels). Commonly, zones 1-5 are determined by a heart rate corresponding to a lactic acid level in the blood. At higher intensities our muscle tissues create more lactic acid, at lower intensities our body can buffer this lactic acid more effectively.
Zones 6 and 7 are rarely tracked by skiers outside of the World Cup level. You can see from the table below, zones 6 and 7 refer to speed and overspeed training. Think about doing a 10-30 second max effort. Your heart rate might not get very high, but the effort is maximal. Some skiers track these efforts by recording how many speed reps they do each week or by tracking the time spent doing speed training.
Below is a table outlining training zones from the USSA coaches manual. This table shows the goal of each zone and does a nice job explaining the pacing 'feel' of each zone. It is a little outdated when it comes to lactic acid levels which we will explain later.
(USSA coaches manual)
Lactic acid is not the only biomarker used to determine training zones. The use of ventilation has become more popular in the last decade as an alternative to measuring training zones with just lactic acid and heart rate. Historically, ventilation machines were used to measure Vo2Max but were big, difficult to celebrate, and generally confined to a laboratory setting.
Now physiologist are using smaller mobile ventilatory measuring devices on a larger scale. This type of zone testing focuses on identifying ventilatory thresholds. (VT1 and VT2).
For more info on ways to measure training zones check out Tom Cuddy's Calibrated Coaching
Here is an example of testing data that combines lactic acid, heart rate, and ventilation measurements.
Ventilatory thresholds create 3 distinct zones separated by two distict metabolic shifts. (This is why sometimes we hear physiologist talking about the benefits of zone 2 training.) You can see how these correspond to a 5 zone training model below:
Which way of determining training zones is best? The short answer is that they are both great. Most elite skiers still tend to use a lactic acid testing protocol because blood samples are easy to replicate in the field. Lactic acid monitors are generally cheap and easy to use compared to a face mask and ventilation unit. It's easy to have a group of athletes all doing intervals together and a coach can 'spot check' their lactic acid. This is more difficult with ventilation measuring.
It’s important to remember that training zones are moving targets and your lactic acid at a specific heart rate can vary on a daily basis. Is your L1 the same running vs. skate skiing vs. double poling? Probably not. Factors such as hydration and altitude can affect training zones for a given session. This is why spot checks at the elite level are important, but it also shows the importance of teaching athletes to feel their training zones more effectively.
One thing that ventilation testing has taught us over the years is that lactic acid and heart rate can vary tremendously among athletes. 2.5 mmol of lactic acid can feel very different for one athlete versus another. This is why the old USSA coaches manual table is a bit outdated. We are now learning that we should not assign rigid lactic acid limits to training zones, especially zones 2 and 3. For some skiers a perfect zone 3 (L3) pace could be 2.5-3 mmol of lactic acid, for others it might be 3-4 mmil of lactic acid. One shift we definitly have noticed over the years is that athletes who do their zone 3 training at a controlled pace see better aerobic results. For most this means keeping their lactic acid below 4 mmol and recognizing that training zones are not rigid, instead these zones overlap one another. I like the Stephen Seiler table below as a good example:
Do all skiers need to monitor training zones?
For developing U16 athletes simply starting to think about different paces is adequate. Most youth skiers lack the strength and fitness to make zone training worthwhile. Most 12 year olds I know have two paces, fast and barely moving. As skiers build strength, fitness, and efficiency within their technique they can begin to explore specific intensities during training. Typically around the age of 16 skiers can begin to feel the difference between an easy pace that can be sustained for 60-90 minutes and a race pace. Next athletes will learn to distinguish between a hard race pace (L4) and a L3 pace that can be sustained for 40-60 minutes. This means that blood lactate and metabolic testing is not really appropriate for athletes until they are in high school or even later.
For Junior athletes, developing skiers, and most master racers I still think going by 'feel' is an adequate way to gauge intensity levels. Here is a simple way to determine your levels:
Level 1: can chat comfortably while training
Level 2: can hear yourself breath (feel good training)
Level 3: long distance controlled race pace (can sustain for 45+ minutes continuously without much fatigue)
Level 4: fast paced short distance race pace (can sustain for 20 minutes)
Level 5: max effort, speed
As athletes progress, learning to ski with proper technique in L1 will become easier but it does take time and is not a realistic expectation for developing athletes. A good guide when searching for the correct L3 interval pace is to start on the easy side and build into the session for the best results. Doing L3 intervals too hard is a very common mistake for athletes trying to make fitness gains. If you have questions about your personal training zones feel free to reach out.