You’re now in the second Base Phase — one of the most intense phases of your training. It will challenge you regularly, and that’s exactly the point. The main focus of this phase is to improve your running economy and increase your VO₂max.
What exactly can you expect in the Base B phase?
Base B is not only the second-longest phase of your training structure — it’s also one of the toughest.
This is where things get serious: your body will be purposefully pushed to reach the next performance level.
You’ll experience many high-intensity sessions (HIT). Especially early on, these workouts may feel demanding — and that’s intentional. The goal is to target your neuromuscular coordination and boost the performance of your cardiovascular system.
This phase relies on two key training components:
1. Sprints and Anaerobic Capacity Intervals
These intervals are designed to push you to your limits — so your body learns to cope with high lactate levels while becoming more efficient at absorbing and using oxygen.
In short: your legs will learn to handle the burn, while your body adapts to recover faster and perform better. These stimuli not only prepare you for race-day intensity but also lay the groundwork for a higher VO₂max and better muscular resilience.
2. Zone 2 Training
These steady, controlled sessions are essential for your aerobic base. They teach your body to burn more fat as fuel even at low intensities and to use oxygen more efficiently.
It may sound uneventful — but it’s absolutely vital.
So what exactly will you do in Base B?
A mix of strides, sprints, and short but intense HIT intervals
Fatmax sessions that train your body to rely on fat as a primary energy source
Your goal in the Base Phase:
The goal is to improve your running economy and strengthen your leg muscles. At the same time, your body learns to sustain high output aerobically, without producing excessive lactate.
Put simply: your body becomes more efficient — delivering more power with less wasted energy.
Instead of slipping into the anaerobic zone too early, you train your system to generate energy for longer durations while staying low in lactate. That saves your reserves and makes you faster — and more enduring — over longer distances.
Nice to know:
Even during this phase, you’ll already notice measurable improvements in your cardiovascular function — like a lower resting heart rate and a lighter, more efficient running feeling.