# Study 000B Limitations

1. This is a single-subject within-system study and does not support population inference.
2. The HR residual model is intentionally simple and descriptive, not a validated physiology model.
3. The early and late comparison windows are matched by run count rather than elapsed time, spanning `93` versus `43` calendar days.
4. High-resolution running mechanics and session HR are concentrated in the later device-supported window.
5. Specialization correlations are descriptive and likely partly time-confounded.
6. HRV is available only late, which limits symmetric early-late comparison.
7. Sleep availability is slightly uneven across windows, and recovery markers are not equally mature in both periods.
8. The food layer is partial and late-window only, so it can only provide confound context rather than causal adjudication.
9. The study cannot prove exact physiological mechanism for the unexplained HR burden signal.