Endurance Training Plan (Week 2) – The 10% Rule That Will Keep You Safe

The first week laid the foundation—your body got used to regular, low-intensity exercise. Now comes the moment when we start building real aerobic capacity: increasing the volume. This is one of the most critical moments of the entire training block, because this is exactly where most runners make a key mistake—they increase their mileage by 30–40% all at once, and by the third week they’re already dealing with periostitis or a pulled calf muscle.

That’s why we stick to a conservative but reliable rule: weekly volume increases by 10–15% compared to the previous week—never more. The body (tendons, ligaments, bones) adapts more slowly than the cardiovascular system—you’ll see cardiovascular improvements in just a few weeks, but connective tissue needs months of gradual stress. A slower increase in volume now is an investment that will save you from having to take a forced break later in the training block.

Strategy for Week 2: Gradual increase, same intensity

• The intensity remains the same as in Week 1 —still strictly Zones 1–2, no intervals. The only variable we’re working with is volume.
• The long run sees the most significant increase—add 10–15 minutes compared to last week. The long run has the greatest impact on aerobic adaptation.
• Strength training 2×/week continues; we’re slightly increasing the load (RPE 7 instead of 6) while maintaining the number of repetitions.
• Monitor your heart rate, not just your pace—if your heart rate increases at the same slow pace compared to last week, it’s a sign of insufficient recovery, not a reason to pick up the pace.

Nutrition and Recovery: Supporting Increasing Physical Demands

As mileage increases, so does the strain on joints, tendons, and mineral balance.

1. Comprehensive joint nutrition —glucosamine and collagen support the resilience of tendons and cartilage against the repeated impact that comes with increased mileage.
2. Magnesium —essential for muscle function and preventing cramps, the risk of which increases with training volume and sweating.

What to Expect Next

By the third week, your aerobic base is considered sufficiently developed, and high-quality training returns to the plan for the first time. We’ll show you what the first interval training session looks like within the polarized training method—and why it makes up only 20% of the weekly volume.