Theoretical profile types and example He I λ10830 Å profiles observed in our data. Left column: theoretical profiles for the eight profile types described in Sect. 3.2. Middle and right columns: examples of each profile type in the Lupus and Upper Scorpius samples, respectively. The flux has been normalised to the continuum level in each source, and rescaled between ±1 for plotting. The grey horizontal line marks the continuum level at 0, while the vertical grey line denotes 0 km s⁻¹. We observe no pure emission or miscellaneous profile types in the Upper Scorpius sample.