How we plan L3 intervals

We know threshold/ L3 training is an important building block of our fitness. Without an efficient threshold base, we cannot reach our true fitness potential during the winter racing months. While the terms L3 and threshold tend to be interchangeable in xc training we want to make one very important clarification. Both L3 and threshold interval  training should be done BELOW lactate threshold for best results not necessarily AT lactate threshold. For some athletes this might be 3-4 heart beats below anaerobic threshold and for some it might be 6-10 heart beats lower. It really depends on individual physiology. (for more information in training zones check out our Training Zones Explained entry. 

From May through July NTS will typically recommend at least 4 threshold sessions per month (more on the Elite plan). Threshold sessions will continue in August through November but with the addition of more L4 (race pace) intensity each week. L3 intervals are a staple of our weekly training throughout the summer but how do we know how much to do? Should each interval session be the same? 

The answer to these questions will depend on your age, training history, and the type of races you are training for. Everyone however should have some progression with their threshold on-time throughout the off-season in order to improve their aerobic capacity. 

What is on-time? On-time refers to the total amount of time 'going hard' during the interval session. So a 3 x 10 minute interval session logs 30 minutes of on-time regardless of how much recovery an athlete takes between intervals. 

You might ask: Well, my heart rate is not exactly in L3 for the entire 10 minute interval. Do I still count that as on-time? 

My answer is yes. Despite new technology that allows heart rate monitoring apps to record the exact number of minutes and seconds within a heart rate zone, the actual interval on-time is what is important. There is often some lag time to get your heart rate up when you start the interval but that's ok, it's the time spent at the prescribed pace that is important. 

A general guideline is that young athletes should progress their threshold on-time to reflect the distances that they race in the winter. (5k, 10k, 15k, 30k, 50k etc.) We also want to think about intensity on-time in relation to how many hours per year an athlete is training. At NTS we prescribe a polarized training model with pyramidal intensity distribution. Meaning, 85-90% of our training is done at an easy intensity and only 10-15% is done at a high intensity including L3 and L4. So intensity on-time must remain an appropriate percentage of total hours trained per year. 

For example, youth skiers (ages 16 and under) can benefit from threshold training as much as an elite skier but their on-time should be considerably less. For youth skiers who primarily race 5-10km races, and who train less than 500 hours per year,  I recommend starting the summer with 15-20 minutes of on-time and building up to 25 – 35 minutes. 

As skiers mature, build up a yearly training base, and begin to race longer events this can be reflected in the amount of interval on-time they log each session. Older junior athletes (>16 yrs), senior athletes, and elite masters can build from 30 minutes of on-time to 60 minutes throughout the summer. Athletes who plan to focus on 30K – 50K+ events can even build up to the occasional 60 – 80 minutes of on time in a single session by July and August. These sessions should be done sparingly and with adequate fueling and recovery built into the plan. 

A skier’s L3 interval on-time should coincide with the periodization of their total monthly training volume. Meaning, as an athlete’s total hours climb from May, June, July, August, so should their monthly threshold on-time. When we cut back on training hours for easy weeks, we should also do so with our threshold on-time and reduce the total load for the week. 

Below is a likely progression for an elite level skier racing events in the 10-30k+ range 

May – 30 minutes of L3 each session 

June – 40 to 45 minutes of L3 each session (30 on easy weeks) 

July – 45 to 60 minutes of L3 each session (40 on easy weeks) 

August – 50 – 60 minutes of L3 each session (35 -40 on easy weeks) 

September through November – interval on time will vary depending on total amount of intensity in the week. For weeks with lots of L4/race intensity reduce L3 on-time to 40 minutes. For big volume weeks increase to mid-summer levels 50 – 60 minutes. 

The beauty of L3 training is that we have A LOT of flexibility in interval length. We can split up 30-60 minutes of on-time in all kinds of ways. The most common L3 interval length is 5-12 minutes in duration with 2-3 minutes of recovery. The exact recovery time is not crucial, but logging QUALITY intervals is. This means generally younger athletes might consider sticking to intervals below 8 minutes in duration. Older athletes who have more strength and higher efficiency can play around with intervals in the 10-15 minute range. 15+ minute intervals are often what we refer to as steady-state training. And elite level athletes will occasionally log continuous L3 time in longer bouts. 

5 x 5 minutes w/ 2 min recovery 

7-10 minute intervals w/ 3 minutes recovery 

10 – 20 minute intervals w/ 4 minutes recovery 

2-3 x 20 minutes steady state (short breaks for feeding and drinking) 

Members will notice that in most weekly training recommendations NTS prescribes a specific interval repetition and recovery time in our plans. These intervals will progress in a way that allows our bodies to absorb these important interval session throughout the summer and fall.  Well planned L3 training will help our bodies build and strengthen mitochondria, allowing us to carry more oxygen in our blood.