# Study 000D Abstract

This study asked whether the six-year altered-mechanics adaptation program aligned more strongly with `broad normalization` or with `selective adaptation through selective expression`.

Using packaged outputs from `Study 000A`, `Study 000B`, `Microstudy B`, and `Study 000C`, the study tested six evidence families: ecological breadth, mechanical gain pathway, higher-demand probe behavior, constraint persistence, internal cost, and robustness after full-data correction.

All six evidence families aligned more strongly with `selective expression`.

The later system showed narrowed successful running expression rather than broader outdoor tolerance. Running share of structured hours rose from `21.00%` in `2025` to `84.18%` in `2026`, while treadmill share of running miles rose from `92.78%` to `98.74%`. Later speed gain remained turnover-led, with cadence contributing `62.42%` of the cadence-stride speed gain. In later higher-demand outdoor probes, cadence stayed above expected while stride remained below expected in `5/5` runs. Efficiency improved, but unexplained burden did not disappear: speed-per-HR improved while late HR residuals remained positive and later outdoor HR residuals averaged `8.67%`.

The corrected full-data pass in `Study 000C` refined ecology wording but did not overturn the main model.

The strongest supported conclusion is that this altered-mechanics system followed a `selective adaptation model`: successful running expression became narrower, more stabilized, more turnover-dependent, and only partially less costly, rather than broadly normalizing across contexts.