L4 B Intervals
For those who are not familiar with the term L4B it simply refers to a slightly more controlled L4 interval pace. If L4 = 5k race pace (15-20 min effort), then L4B = 10k race pace (25-35 min effort)
It is a common misconception that the harder we do our L4 intervals the better, when in reality much of the new science indicates that this is not the case. Most sports physiologists now agree that it is not necessarily the intensity of your L4 intervals that matter, rather the amount of quality on-time logged per session.
L4 is typically categorized as 90% - 100% of max heart rate. L4B breaks things down even further and really focuses on the 90% - 92% range (or the 6 – 7 mmol of lactic acid range). This is an effective training model because by isolating the very bottom of our L4 heart rate zone we are able to do plan sessions with slightly longer intervals and potentially more of them therefore further increasing our Vo2max than if we were to be hammering closer to our max.
Session:
5-6 x 5 minutes L4B (mid distance race pace)
Terrain: Rolling but with plenty of climbing
Warm Up:
15 minutes easy
5 minutes L2
5 minutes easy with accelerations
5 minutes dynamic stretching
(can also use morning mechanics skate or classic as part of your warm-up routine)
Intervals:
5 – 6 x 5 min with 3 minutes rest between intervals
Having a good feeling of where your lactate threshold is will make finding your L4 B pace a bit easier. If you don’t have a heart rate monitor, no stress. I like to focus on easing into each interval so my heart rate elevates naturally to threshold during the first minute. Once at threshold I increase the pace just a touch to bump my heart rate up a few beats. It’s not an all out race-pace, but comfortable and fast. Easy enough to maintain for the next 4 minutes of each interval.
For most individuals a good L4B pace is just 2-3 heart beats above their L3 pace
Goals:
Log more L4 on-time than an all our hammer L4 session. Logging 25 – 30 minutes of L4B can have a big impact increasing Vo2max and improve overall fitness.
Lactate goal: 6-8 mmol
