diff --git a/bincio/extract/parsers/fit.py b/bincio/extract/parsers/fit.py
index 5353107..d5e165b 100644
--- a/bincio/extract/parsers/fit.py
+++ b/bincio/extract/parsers/fit.py
@@ -147,11 +147,13 @@ def _normalise_sub_sport(value: Any) -> str | None:
     mapping = {
         "generic":           None,       # FIT default — unspecified
         "virtual_activity":  "indoor",
+        "virtual":           "indoor",
         "road":              "road",
         "mountain":          "mountain",
         "gravel_cycling":    "gravel",
         "cyclocross":        "gravel",
         "indoor_cycling":    "indoor",
+        "treadmill":         "indoor",
         "trail":             "trail",
         "track":             "track",
         "cross_country_skiing": "nordic",
diff --git a/bincio/extract/writer.py b/bincio/extract/writer.py
index d425c78..1eb3d30 100644
--- a/bincio/extract/writer.py
+++ b/bincio/extract/writer.py
@@ -277,8 +277,10 @@ def write_athlete_json(summaries: list[dict], output_dir: Path, athlete_config:
                     best[d] = w
         return [[d, w] for d, w in sorted(best.items())]
 
+    _INDOOR_SUB_SPORTS = {"indoor", "treadmill", "virtual"}
+
     def _is_outdoor(s: dict) -> bool:
-        return s.get("sub_sport") != "indoor"
+        return s.get("sub_sport") not in _INDOOR_SUB_SPORTS
 
     all_mmps = [s["mmp"] for s in summaries if s.get("mmp") and _is_outdoor(s)]
     mmps_365 = [s["mmp"] for s in summaries if s.get("mmp") and _is_outdoor(s) and s["started_at"] >= cutoff_365]
diff --git a/bincio/render/cli.py b/bincio/render/cli.py
index b2efaa4..489233e 100644
--- a/bincio/render/cli.py
+++ b/bincio/render/cli.py
@@ -105,6 +105,35 @@ def _bake_tracks(data: Path, handle: str | None = None) -> None:
             console.print(f"  [yellow]{user_dir.name}[/yellow]: bake_tracks failed: {exc}")
 
 
+def _rebuild_athlete_json(data: Path, handle: str | None = None) -> None:
+    """Rebuild athlete.json for one user or all users from their current index.json."""
+    import json
+    from bincio.extract.writer import write_athlete_json
+
+    targets = [data / handle] if handle else _user_dirs(data)
+    _COMPUTED = {"bas_version", "generated_at", "power_curve", "records", "best_climbs"}
+    for user_dir in targets:
+        index_path = user_dir / "index.json"
+        if not index_path.exists():
+            continue
+        try:
+            index_data = json.loads(index_path.read_text(encoding="utf-8"))
+            summaries = index_data.get("activities", [])
+            if not summaries:
+                continue
+            athlete_config: dict = {}
+            athlete_path = user_dir / "athlete.json"
+            if athlete_path.exists():
+                try:
+                    existing = json.loads(athlete_path.read_text(encoding="utf-8"))
+                    athlete_config = {k: v for k, v in existing.items() if k not in _COMPUTED}
+                except Exception:
+                    pass
+            write_athlete_json(summaries, user_dir, athlete_config)
+        except Exception as exc:
+            console.print(f"  [yellow]{user_dir.name}[/yellow]: rebuild_athlete failed: {exc}")
+
+
 def _write_root_manifest(data: Path) -> None:
     """Rewrite the root index.json shard manifest from current user dirs."""
     import json
@@ -207,6 +236,7 @@ def render(
     console.print(f"Data:  [cyan]{data}[/cyan]")
 
     _merge_edits(data, handle=handle)
+    _rebuild_athlete_json(data, handle=handle)
     _bake_tracks(data, handle=handle)
     _write_root_manifest(data)