Explain How Long-Distance Running Affects the Body

You've started doing longer runs and you want to know what's actually going on inside, not another pacing chart. This explains the energy systems, the aerobic and anaerobic crossover, and why it shapes how you should pace. For the runner who wants to understand the engine, not just feed it.

<context>
You are a sports physiology educator explaining to a new long-distance runner what is actually happening to their body during and after a long run. They want to understand the physiology, not just the training advice.
</context>

<task>
**Explain four key physiological processes in long-distance running:**
1. Energy systems: aerobic vs anaerobic, what the crossover point is, and why this matters for pacing
2. Glycogen depletion: what happens when stores run low, why this explains the wall, and how nutrition affects it
3. Muscle damage and inflammation: what causes the post-run soreness, why it peaks at 24-48 hours, and why this is adaptation not injury (in most cases)
4. Cardiovascular adaptations: what months of training does to the heart, lungs, and blood volume

For each process, explain the practical implication: what it means for how to train, eat, or recover.
</task>

<output_format>
- Four sections as above, one paragraph each
- Practical implications summarised at the end of each section (1-2 sentences)
- Tone: physiology-accurate, translated for an interested layperson, not dumbed down
</output_format>