Descriptor | CoDA transform | Statistical modelling | Risk of closure?* | Risk of collinearity? | Handles closure? | Handles collinearity? | Relationship assumptions | Allow investigation of longitudinal associations (eg, Cox regression) | Interpretation relative to guidelines? (eg, 150 min/week of MVPA) |

Average acceleration | No | Linear | No | No | NA | NA | Linear | Yes | No |

Time-use descriptors | No | Linear | Yes | Yes | No | No | Linear | Yes | Yes |

Yes | Linear | Yes | Yes | Yes | In part† | Log-linear | Yes | Yes | |

No | ISO | Yes | Yes | Yes | No | Linear | Yes | Yes | |

No | MPA | Yes | Yes | No | No | Linear | Not at the moment | Yes | |

Yes | MPA | Yes | Yes | Yes | Yes | Log-linear | Not at the moment | Yes | |

Intensity spectrum | No | Linear | Yes | Yes | No | No | Linear | Yes | Yes‡ |

Yes | Linear | Yes | Yes | Yes | In part† | Log-linear | Yes | Yes‡ | |

No | ISO | Yes | Yes | Yes | No | Linear | Yes | Yes‡ | |

No | MPA | Yes | Yes | No | No | Linear | Not at the moment | Yes‡ | |

Yes | MPA | Yes | Yes | Yes | Yes | Log-linear | Not at the moment | Yes‡ | |

Intensity gradient | No | Linear | No | No | NA | NA | Linear | Yes | No |

No | FDA | No | No | NA | NA | Fewer assumptions than other models | Yes | Yes§ | |

MX metrics | No | Linear | Yes | Yes | No | No | Linear | Yes | Yes‡ |

No | MPA | Yes | Yes | No | Yes | Linear | Not at the moment | Yes‡ | |

Other acceleration functions | No | FDA | No | No | NA | NA | Fewer assumptions than other models | Yes | Yes§ |

*Closure refers to whether a certain descriptor is a specific part of the daily time constraint (ie, it is measured in time per day).

†Indicates that it solves the collinearity due to the closure, but collinearity can still exist across the CoDA-transformed variables.

‡Indicates that the interpretation is made through a post-hoc application of validated cut-points to identify the PA intensity (eg, MVPA).

§Indicates that more work is needed on the interpretation of functional data analysis, an example can be found elsewhere.39

CoDA, compositional data analysis; FDA, functional data analysis; ISO, isotemporal substitution models; MPA, multivariate pattern analysis; MVPA, moderate-to-vigorous PA; MX, acceleration above which a person’s most active X minutes/time are spent; NA, not applicable; PA, physical activity.