Table 3 Gait parameters extracted from the gait cycles of the subjects included in the study.
From: Integration of smart insoles for gait assessment in exoskeleton assisted rehabilitation
Type | Name | Description | Equation | References | |
|---|---|---|---|---|---|
Kinematic | Stride time | Duration in seconds between the initial contact of one foot to the next contact of the same foot. It is expressed in seconds | \(\frac{\sum _{e}^{E}{e_{END} - e_{START}}}{fs},\)\(\quad E = \{IC, LR, MSt, TSt, Sw\}\) | where E is the set of events composing the stride, END and START are the last and first index for the event e, and fs is the sampling frequency | |
Stance time | Duration during which a foot is in contact with the ground during a single gait cycle. It is expressed in seconds | \(\frac{\sum _{e}^{E}{e_{END} - e_{START}}}{fs},\)\(\quad E = \{IC, LR, MSt, TSt\}\) | where E is the set of events composing the stance phase, END and START are the last and first index for the event e, and fs is the sampling frequency | ||
Swing time | Duration during which the foot is off the ground and swinging forward in the air during a single gait cycle. It is expressed in seconds | \(\frac{Sw_{END} - Sw_{START}}{fs}\) | where \(Sw_{END}\) and \(Sw_{START}\) are the last and first index of the swing phase, and fs is the sampling frequency | ||
Stance percentage | Proportion of the gait cycle spent in the stance phase, expressed as a percentage | \(\frac{\text {Stance time}}{\text {Stride time}} \times 100\) | |||
Swing percentage | Proportion of the gait cycle spent in the swing phase, expressed as a percentage | \(\frac{\text {Swing time}}{\text {Stride time}} \times 100\) | |||
Single support time | Duration when only one foot is in contact with the ground during a gait cycle. It is expressed in seconds | \(\sum \frac{1}{fs} \quad \text {if} \ \ x_l \in \text {St} \wedge x_r \in \text {Sw},\)\(\quad \forall x \in GC\) | where fs is the sampling frequency, \(e_l\) and \(e_r\) are the left and right foot event respectively, and St and Sw are the stance and swing phases | ||
Double support time | Duration during which both feet are in contact with the ground during a gait cycle. It is expressed in seconds | \(\sum \frac{1}{fs} \quad \text {if} \ \ e_l \in \text {St} \wedge e_r \in \text {St},\)\(\quad \forall e \in GC\) | where fs is the sampling frequency, \(e_l\) and \(e_r\) are the left and right foot event respectively, and St is the stance phase | ||
Single support percentage | Proportion of the gait cycle spent in single support, expressed as a percentage | \(\frac{\text {Single support time}}{\text {Stride time}} \times 100\) | |||
Double support percentage | Proportion of the gait cycle spent in double support, expressed as a percentage | \(\frac{\text {Double support time}}{\text {Stride time}} \times 100\) | |||
Kinetic | COP ML | It is the Centre of Pressure on the Mediolateral sagittal plane. | \(\frac{\sum {F_i X_i}}{\sum {F_i}}\) | where \(F_i\) is the force applied to the i-th pressure sensor and \(X_i\) is the sensor’s position on the mediolateral plane | |
COP AP | It is the Centre of Pressure on the Anterior-posterior sagittal plane. | \(\frac{\sum {F_i Y_i}}{\sum {F_i}}\) | where \(F_i\) is the force applied to the i-th pressure sensor and \(Y_i\) is the sensor’s position on the anterior-posterior plane | ||
Range COP ML | Amplitude of mediolateral COP displacement. It is expressed in cm | \(max_{n,m}|ML_n - ML_m|\) | where ML represents the COP ML | ||
Range COP AP | Amplitude of anterior-posterior COP displacement. It is expressed in cm | \(max_{n,m}|AP_n - AP_m|\) | where AP represents the COP AP | ||
Planar deviation | Average distance of each COP point from the mean COP position in the transverse plane. It is expressed in cm | \(\sqrt{\text {RMS}(\text {ML})^2 + \text {RMS}(\text {AP}^2)}\) | where RMS is the root mean square, ML is the COP ML, and AP is the COP AP | ||
Confidence ellipse area | Area of the ellipse that contains 95% of the COP points in the transverse plane. It is expressed in \(\text {cm}^2\) | \(\pi \sqrt{\lambda _1 \lambda _2} \chi ^2_{2, 0.95}\) | where \(\lambda _1\) and \(\lambda _2\) are the eigenvalues of the covariance matrix, and \(\chi ^2_{2, 0.95}\) is the chi-squared value for 2 degrees of freedom at the 95% confidence level | ||
Principal sway direction | Angle between 0° and 90°, between the anterior-posterior axis and the direction of the main eigenvector produced by the Principal Component Analysis (PCA). It is expressed in degrees | \(arccos(\frac{|v_2|}{\sqrt{v_1^2 + v_2^2}}) \times \frac{180}{\pi }\) | where \(v=(v_1, v_2)\) denotes the eigenvector associated with the highest variance produced by the PCA of the COP | ||
