In Equi-Pro, several gaits are detected: walk, trot, canter left/right, tölt and pace. Each gait is characterized by a footfalls pattern and has specific suspension possibilities (moments where no hooves are on the ground), as well as Lateral and Diagonal Advanced Placements (LAP, DAP), also called lateral and diagonal dissociation, respectively. These are the timing differences describing the duration between two limbs hoof-on events. For example at trot, a negative DAP describes an earlier hind limb landing compared to the diagonal front limb, which is often described as a higher gait quality.
In this article, we describe for each gait the stride of interest, its footfalls pattern and which stance/swing phases are used to calculate Suspension, LAP and DAP.
Walk
Stride of interest
Walk strides of interest should start with LHon events and finish after the following RFoff, as illustrated by the dotted box on the stance-swing figure below.
/!\ To calculate the stride duration, we use Limbon(striden+1) – Limbon(striden).
Footfall pattern
Walk is a symmetrical, lateral four-beat gait without suspension. The footfall pattern is the following: LH→LF→RH→RF→LH→…
Figure 1 – Footfalls pattern at walk represented with hooves (left) and stance (full rectangles) and swing (empty dotted rectangles) phases (right) for several strides. Each black rectangle (right) represents a stride of interest to compute DAP and LAP.
Suspension, DAP, LAP
At walk, there is no suspension as there are always at least two limbs in contact with the ground.
While there is not much evidence that DAP or LAP can be useful for lameness classification, providing these values to researchers can help identify patterns in the future.
- DAP LH-RF: LHon(striden) – RFon(striden)
- DAP RH-LF: RHon(striden) – LFon(striden+1)
- LAP LH-LF: LHon(striden) – LFon(striden)
- LAP RH-RF: RHon(striden) – RFon(striden)
Figure 2 – Footfalls pattern at walk represented for one stride with stance (full rectangles) and swing (empty dotted rectangles) phases. DAP and LAP computed at walk are shown with arrows.
Trot
Stride of interest
Trot stride of interest should start with the earliest LH-RF diagonal hoof-on event (LHon or RFon) and finish after the following latest RH-LF hoof-off event (RHoff or LFoff) as illustrated by the dotted rectangle on the stance-swing figure below.
/!\ To calculate the stride duration, we use Limbon(striden+1) – Limbon(striden).
Footfall pattern
Trot is a symmetrical two-beat diagonal gait, with a suspension phase. The footfall pattern is the following: LH-RF → suspension → RH-LF → suspension → LH-RF → …
Figure 3 – Footfalls pattern at trot represented with hooves (left) and stance (full rectangles) and swing (empty dotted rectangles) phases (right) for several strides. Each black rectangle (right) represents a stride of interest to compute Suspensions and DAP.
Suspension, DAP
During trot, there are two suspension phases: the one after LH-RF lift-off and the one after RH-LF lift-off.
To calculate the suspension phases, we first need to identify which limb of the diagonal is leaving the ground last and which limb of the following diagonal is touching the ground first.
It is also possible that there is no suspension after one or the other diagonal.
- Suspension LH-RF to RH-LF: RH/LFon(striden) – LH/RFoff(striden)
- Suspension RH-LF to LH-RF: LH/RFon(striden+1) – RH/LFoff(striden)
- DAP LH-RF: LHon(striden) – RFon(striden)
- DAP RH-LF: RHon(striden) – LFon(striden)
In trot, DAP can be interesting for gait quality assessment. DAP is always calculated between the diagonal pair of limbs of the same stride, as shown in the example below.
Figure 4 – Footfalls pattern at trot represented for one stride with stance (full rectangles) and swing (empty dotted rectangles) phases. DAP and suspensions computed at trot are shown with arrows.
Canter – Left
Stride of interest
/!\ Canter Left stride starts with the RHon event and finish after the LFoff event, as illustrated below.
/!\ To calculate the stride duration, we use RHon(striden+1) – RHon(striden).
Footfall pattern
Canter is an asymmetrical three-beat running gait. At left canter, the footfall pattern is:
RH → LH-RF → LF → Suspension → RH → …
Figure 5 – Footfalls pattern at left canter represented with hooves (left) and stance (full rectangles) and swing (empty dotted rectangles) phases (right) for several strides. Each black rectangle (right) represents a stride of interest to compute Suspension and DAP.
Suspension, DAP
Suspension happens after LF leaves the ground until the next RH hoof on event, as illustrated below. DAP can also happen between RF and LH hoof on of the same stride.
- Suspension LF to RH: RHon(striden+1) – LFoff(striden)
- DAP LH-RF: LHon(striden) – RFon(striden)
Figure 6 – Footfalls pattern at left canter represented for one stride with stance (full rectangles) and swing (empty dotted rectangles) phases. DAP and suspension computed at trot are shown with arrows.
Canter – right
Stride of interest
/!\ Right Canter stride starts with the LHon event and finishes after the RFoff event, as illustrated below.
/!\ To calculate the stride duration, we use LHon(striden+1) – LHon(striden).
Footfall pattern
Canter is an asymmetrical three-beat gait. At right canter, the footfall pattern is:
LH → RH-LF → RF → Suspension → LH → …
Figure 7 – Footfalls pattern at right canter represented with hooves (left) and stance (full rectangles) and swing (empty dotted rectangles) phases (right) for several strides. Each black rectangle (right) represents a stride of interest to compute Suspension and DAP.
Suspension, DAP
Suspension happens after RF leaves the ground until the next LH touches the ground, as illustrated below. DAP can also happen between LF and RH hoof on of the same stride.
- Suspension RF to LH: LHon(striden+1) – RFoff(striden)
- DAP RH-LF: RHon(striden) – LFon(striden)
Figure 8 – Footfalls pattern at right canter represented for one stride with stance (full rectangles) and swing (empty dotted rectangles) phases. DAP and suspension computed at canter are shown with arrows.
Tölt
Stride of interest
Tölt strides starts at LHon events and stop after the following RFoff event, as illustrated below.
/!\ To calculate the stride duration, we use Limbon(striden+1) – Limbon(striden).
Footfall pattern
Tölt is a symmetrical four-beat gait, with the following footfall pattern:
LH → LF → RH → RF → LH → …
It differs from walk by its higher speed, the presence of unipedal support and the absence of tripedal support (in true tölt).
Figure 9 – Footfalls pattern at tölt represented with hooves (left) and stance (full rectangles) and swing (empty dotted rectangles) phases (right) for several strides. Each black rectangle (right) represents a stride of interest to compute LAP and DAP.
Suspension, LAP, DAP
There is no suspension in tölt. LAP and DAP can be interesting to consider, especially to differentiate between true tölt, tölt with lateral couplets (shorter LAP) and mixed tölt as used in Smit et al. 2023.
- LAP LH-LF: LHon(striden) – LFon(striden)
- LAP RH-RF: RHon(striden) – RFon(striden)
- DAP LH-RF: LHon(striden) – RFon(striden)
- DAP RH-LF: RHon(striden) – LFon(striden+1)
Figure 10 – Footfalls pattern at tölt represented for one stride with stance (full rectangles) and swing (empty dotted rectangles) phases. LAD and DAP computed at tölt are shown with arrows.
Pace
Stride of interest
Pace strides start at LH/LFon event and stop after the following RH/RFoff event, as illustrated below.
/!\ To calculate the stride duration, we use Limbon(striden+1) – Limbon(striden).
Footfall pattern
Pace is a symmetrical two-beat lateral gait, with the following footfall pattern:
LH-LF → suspension → RH-RF → suspension → LH-LF → …
Figure 11 – Footfalls pattern at pace represented with hooves (left) and stance (full rectangles) and swing (empty dotted rectangles) phases (right) for several strides. Each black rectangle (right) represents a stride of interest to compute Suspension and LAP.
Suspension, LAP
During pace, there are two suspension phases: the one after LH-LF lift-off and the one after RH-RF lift-off. To calculate the suspension phases, we first need to identify which limb of the lateral pair is leaving the ground last and which limb of the following lateral pair is touching the ground first. It is also possible that there is no suspension after one or the other diagonal.
In a similar fashion to trot with DAP, it can be interesting to look at LAP and suspension at pace.
- LAP LH-LF: LHon(striden) – LFon(striden)
- LAP RH-RF: RHon(striden) – RFon(striden)
- Suspension LH-LF to RH-RF: RH/RFon(striden) – LH/LFoff(striden)
- Suspension RH-RF to LH-LF: LH/LFon(striden+1) – RH/RFoff(striden)
Figure 12 – Footfalls pattern at pace represented for one stride with stance (full rectangles) and swing (empty dotted rectangles) phases. LAP and suspensions computed at pace are shown with arrows.
