Table 1 Overview of Smoothness metrics identified from the literature

Index of curvature (IC)

[]

1

E3

Trajectory

[33]

Standard deviation in 2D plane (SD_XY)

[]

1

E3

Trajectory

[72]

Number of sub-movements (NOS)

[]

1

Velocity

[37]

Speed metric (SM)

[]

15

Velocity

[14]

Normalized reaching speed (NRS)

[]

2

E4 (SM)

Velocity

[35]

Movement arrest period ratio (MAPR)

[]

3

Velocity

[34]

Tent Metric (TM)

[]

1

E2

Velocity

[14]

Velocity Arc Length (VAL)

[]

1

Velocity

[4]

Correlation Metric (CM)

[]

2

Velocity

[38]

Peaks Metric (Peaks)

[]

61

Acceleration

[39]

Number of Movement Units (NMU)

[]

3

E4a (Peaks)

Acceleration

[73]

Number of peaks normalized by movement duration (NPt)

[s⁻¹]

1

E1

Acceleration

[40]

Number of peaks normalized by movement distance (NPd)

[m⁻¹]

3

E1

Acceleration

[41]

Inverse number of peaks and valleys (IPV)

[]

1

Acceleration

[44]

Acceleration metric (AM)

[]

2

E1

Acceleration

[35]

Integrated absolute jerk (IAJ)

[ms⁻²]

2

E1

Jerk

[74]

Mean absolute jerk (MAJ)

[ms⁻³]

2

E1

Jerk

[33]

Mean absolute jerk normalized by peak speed (MAJPS)

[s⁻²]

7

E1

Jerk

[14]

Integrated squared jerk (ISJ)

[m²s⁻⁵]

1

E1

Jerk

[75]

Root mean squared jerk metric (RMSJ)

[ms⁻³]

1

E1

Jerk

[76]

Normalized integrated jerk (NIJ)

[ms⁻³ \(\sqrt{\mathrm{s}}\)]

1

E1

Jerk

[77]

Dimensionless squared jerk (DSJt)

[]

12

Jerk

[3]

Log dimensionless squared jerk (LDSJt)

[]

1

Jerk

[5]

Dimensionless squared jerk (DSJm)

[]

1

E4a (DSJt)

Jerk

[2]

Dimensionless squared jerk (DSJb)

[]

1

Jerk

[4]

Log dimensionless squared jerk (LDSJb)

[]

1

Jerk

[4]

Rotational jerk (RJ)

[]

1

E3

Jerk

[48]

Spectral metric (SPMR)

[]

1

Frequency

[49]

Spectral method (SPM)

[]

1

Frequency

[1]

Spectral arc length 2012 (SPAL)

[]

8

Frequency

[4]

Spectral arc length (SPARC)

[]

1

Frequency

[6]

Combined smoothness metric (CSM)

[− −]^b

1

E1

Other

[78]