You’ve now reached the final – and longest – part of the Base Phase. This last section still includes high intensities, but some things are changing.
What can you expect in the Base C Phase?
Base C is the longest of the three Base Phases – and it has one clear goal: to improve your VO₂max and increase your overall performance.
In simple terms: your body should learn to take in more oxygen and use it more efficiently – so you can run longer, faster, and stronger without hitting your threshold too early.
To achieve that, this phase focuses on two key training elements:
1. VO₂max Intervals
This time, longer intervals are introduced to really challenge your oxygen transport and utilization. These sessions are intense but incredibly effective: your muscles learn to make use of the additional oxygen that previous HIT sessions helped you absorb better.
Compared to anaerobic capacity intervals, these workouts may feel slightly less muscle-fatiguing – but they still push your limits.
2. Zone 2 and Fatmax Training
Zone 2 sessions build your aerobic base and teach your body to rely more on fat as a fuel source – especially during prolonged efforts. Since very little lactate is produced here, your efficiency increases without leading to fatigue.
Fatmax intervals are especially useful for improving your metabolic flexibility – a key factor for endurance performance.
This is the phase where your solid base turns into real fitness.
What to expect in Base C:
Longer VO₂max intervals
Zone 2 and Fatmax sessions to build endurance and oxygen efficiency
A focus on staying strong under prolonged, moderate stress
Your goals in this phase:
Build mental strength to push through long, demanding intervals
Lower your heart rate thanks to improved oxygen uptake
Find joy in longer runs and sustained efforts
Nice to know:
This phase includes your first key workout – a session that prepares you for your very first half marathon. Use it to test how well your training is working. It will likely challenge you, but that’s exactly the point.
Good luck – you’ve got this! 💪