TABLE 2.

Categories and description of the phase-based micro variable defined on IMU data in global frame. The name of the functions used for micro variables extraction are abbreviated in parentheses.

Category	Description	Micro variables
Propulsion	Variables related to the amount of propulsion generated by the swimmer	Mean (Mean), range (Range) and standard deviation (SD) of $Ac{c}_X$ , $Ac{c}_Y$ and $Ac{c}_Z$ . Maximum (Max), integral (Int), and momentum change (Momentum) of $Ac{c}_Y$
Posture	Variables related to the body posture and drag effects on swimmer’ body	Mean, Range and SD of $\theta$ and $\phi$
Efficiency	Variables related to the efficiency of motion which can reflect in acceleration	Ratio of positive $Ac{c}_Y$ to $\left|Acc\right|$ (Eff_dir) or to negative $Ac{c}_Y$ (Eff), distance per stroke (DPS) in Swim phase
Duration/rate	Variables related to the duration of a phase or the rate of movement	Mean, Range and SD of $Gy{r}_X$ , $Gy{r}_Y$ and $Gy{r}_Z.$ phases and cycles duration. Kick rate and count in StPr phase. Stroke rate and count in Swim phase