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An exploration of the influence of diagonal dissociation and moderate changes in speed on locomotor parameters in trotting horses.

Hobbs SJ, Bertram JE, Clayton HM - PeerJ (2016)

Bottom Line: Discussion.The results indicate that at moderate speeds individual horses use dissociation patterns that allow them to maintain trunk pitch stability through management of the cranio-caudal location of the COP.During the hoof-ground collisions, reduced mechanical energy losses were found in hind-first dissociations compared to fully synchronous contacts.

View Article: PubMed Central - HTML - PubMed

Affiliation: Centre for Applied Sport and Exercise Sciences, University of Central Lancashire , Preston , Lancashire , United Kingdom.

ABSTRACT
Background. Although the trot is described as a diagonal gait, contacts of the diagonal pairs of hooves are not usually perfectly synchronized. Although subtle, the timing dissociation between contacts of each diagonal pair could have consequences on gait dynamics and provide insight into the functional strategies employed. This study explores the mechanical effects of different diagonal dissociation patterns when speed was matched between individuals and how these effects link to moderate, natural changes in trotting speed. We anticipate that hind-first diagonal dissociation at contact increases with speed, diagonal dissociation at contact can reduce collision-based energy losses and predominant dissociation patterns will be evident within individuals. Methods. The study was performed in two parts: in the first 17 horses performed speed-matched trotting trials and in the second, five horses each performed 10 trotting trials that represented a range of individually preferred speeds. Standard motion capture provided kinematic data that were synchronized with ground reaction force (GRF) data from a series of force plates. The data were analyzed further to determine temporal, speed, GRF, postural, mass distribution, moment, and collision dynamics parameters. Results. Fore-first, synchronous, and hind-first dissociations were found in horses trotting at (3.3 m/s ± 10%). In these speed-matched trials, mean centre of pressure (COP) cranio-caudal location differed significantly between the three dissociation categories. The COP moved systematically and significantly (P = .001) from being more caudally located in hind-first dissociation (mean location = 0.41 ± 0.04) through synchronous (0.36 ± 0.02) to a more cranial location in fore-first dissociation (0.32 ± 0.02). Dissociation patterns were found to influence function, posture, and balance parameters. Over a moderate speed range, peak vertical forelimb GRF had a strong relationship with dissociation time (R = .594; P < .01) and speed (R = .789; P < .01), but peak vertical hindlimb GRF did not have a significant relationship with dissociation time (R = .085; P > 0.05) or speed (R = .223; P = .023). Discussion. The results indicate that at moderate speeds individual horses use dissociation patterns that allow them to maintain trunk pitch stability through management of the cranio-caudal location of the COP. During the hoof-ground collisions, reduced mechanical energy losses were found in hind-first dissociations compared to fully synchronous contacts. As speed increased, only forelimb vertical peak force increased so dissociations tended towards hind-first, which shifted the net COP caudally and balanced trunk pitching moments.

No MeSH data available.


Related in: MedlinePlus

Comparison of relative COM velocity (black/grey-left vertical axis) and Dissociation Time (s) (red-right vertical axis) to variables identified in Table 2 for speed range data (n = 5 horses × 10 trials × 2 steps).(A) Mean COM Location, (B) Mean COP Location, (C) Peak GRFV F (N/kg), (D) Impulse F (Ns/kg), (E) Impulse H (Ns/kg), (F) MGRF at Tzero (Nm/kg), (G) MGRF Absorption (Nm/kg), (H) Mean Limb Angle H (deg), (I) Trunk Inclination (deg). The data from each horse is identified with the same symbol, so for each horse a different symbol is used.
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fig-4: Comparison of relative COM velocity (black/grey-left vertical axis) and Dissociation Time (s) (red-right vertical axis) to variables identified in Table 2 for speed range data (n = 5 horses × 10 trials × 2 steps).(A) Mean COM Location, (B) Mean COP Location, (C) Peak GRFV F (N/kg), (D) Impulse F (Ns/kg), (E) Impulse H (Ns/kg), (F) MGRF at Tzero (Nm/kg), (G) MGRF Absorption (Nm/kg), (H) Mean Limb Angle H (deg), (I) Trunk Inclination (deg). The data from each horse is identified with the same symbol, so for each horse a different symbol is used.

Mentions: The velocity of the speed-range dataset was between 2.43 and 4.23 ms−1. Relationships between locomotion parameters, dissociation time and relative COM velocity that were moderate to strong (R > .55) for either dataset are shown in Table 3 and Fig. 4. The relationship between dissociation time and relative COM velocity for speed-matched data was R = .119 and for the speed range data was R = .774. Mean COP location had the strongest relationship with dissociation time when data were speed-matched, but also had a strong relationship with relative COM velocity over the speed range (Table 3). MGRF at Tzero, MGRF during absorption and mean hind limb angle shared only moderate relationships with the speed-matched dataset, whereas trunk inclination had moderate relationships in both datasets. Conversely, forelimb vertical GRF had a strong relationship with dissociation time over the speed range (R = .594; P < .01) but not when speed-matched (R = .145; P > .05). Although only small differences in speed were recorded between horses in the speed-matched dataset, fore and hindlimb impulses were still found to have moderate to strong relationships with relative COM velocity, (with forelimb impulses just outside of the threshold criteria). None of the other functional, postural or balance parameters had moderate to strong relationships in either dataset. Figure 5 depicts mean COP location against relative COM velocity for the speed-range data showing the dissociations used by each horse for each step.


An exploration of the influence of diagonal dissociation and moderate changes in speed on locomotor parameters in trotting horses.

Hobbs SJ, Bertram JE, Clayton HM - PeerJ (2016)

Comparison of relative COM velocity (black/grey-left vertical axis) and Dissociation Time (s) (red-right vertical axis) to variables identified in Table 2 for speed range data (n = 5 horses × 10 trials × 2 steps).(A) Mean COM Location, (B) Mean COP Location, (C) Peak GRFV F (N/kg), (D) Impulse F (Ns/kg), (E) Impulse H (Ns/kg), (F) MGRF at Tzero (Nm/kg), (G) MGRF Absorption (Nm/kg), (H) Mean Limb Angle H (deg), (I) Trunk Inclination (deg). The data from each horse is identified with the same symbol, so for each horse a different symbol is used.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4933092&req=5

fig-4: Comparison of relative COM velocity (black/grey-left vertical axis) and Dissociation Time (s) (red-right vertical axis) to variables identified in Table 2 for speed range data (n = 5 horses × 10 trials × 2 steps).(A) Mean COM Location, (B) Mean COP Location, (C) Peak GRFV F (N/kg), (D) Impulse F (Ns/kg), (E) Impulse H (Ns/kg), (F) MGRF at Tzero (Nm/kg), (G) MGRF Absorption (Nm/kg), (H) Mean Limb Angle H (deg), (I) Trunk Inclination (deg). The data from each horse is identified with the same symbol, so for each horse a different symbol is used.
Mentions: The velocity of the speed-range dataset was between 2.43 and 4.23 ms−1. Relationships between locomotion parameters, dissociation time and relative COM velocity that were moderate to strong (R > .55) for either dataset are shown in Table 3 and Fig. 4. The relationship between dissociation time and relative COM velocity for speed-matched data was R = .119 and for the speed range data was R = .774. Mean COP location had the strongest relationship with dissociation time when data were speed-matched, but also had a strong relationship with relative COM velocity over the speed range (Table 3). MGRF at Tzero, MGRF during absorption and mean hind limb angle shared only moderate relationships with the speed-matched dataset, whereas trunk inclination had moderate relationships in both datasets. Conversely, forelimb vertical GRF had a strong relationship with dissociation time over the speed range (R = .594; P < .01) but not when speed-matched (R = .145; P > .05). Although only small differences in speed were recorded between horses in the speed-matched dataset, fore and hindlimb impulses were still found to have moderate to strong relationships with relative COM velocity, (with forelimb impulses just outside of the threshold criteria). None of the other functional, postural or balance parameters had moderate to strong relationships in either dataset. Figure 5 depicts mean COP location against relative COM velocity for the speed-range data showing the dissociations used by each horse for each step.

Bottom Line: Discussion.The results indicate that at moderate speeds individual horses use dissociation patterns that allow them to maintain trunk pitch stability through management of the cranio-caudal location of the COP.During the hoof-ground collisions, reduced mechanical energy losses were found in hind-first dissociations compared to fully synchronous contacts.

View Article: PubMed Central - HTML - PubMed

Affiliation: Centre for Applied Sport and Exercise Sciences, University of Central Lancashire , Preston , Lancashire , United Kingdom.

ABSTRACT
Background. Although the trot is described as a diagonal gait, contacts of the diagonal pairs of hooves are not usually perfectly synchronized. Although subtle, the timing dissociation between contacts of each diagonal pair could have consequences on gait dynamics and provide insight into the functional strategies employed. This study explores the mechanical effects of different diagonal dissociation patterns when speed was matched between individuals and how these effects link to moderate, natural changes in trotting speed. We anticipate that hind-first diagonal dissociation at contact increases with speed, diagonal dissociation at contact can reduce collision-based energy losses and predominant dissociation patterns will be evident within individuals. Methods. The study was performed in two parts: in the first 17 horses performed speed-matched trotting trials and in the second, five horses each performed 10 trotting trials that represented a range of individually preferred speeds. Standard motion capture provided kinematic data that were synchronized with ground reaction force (GRF) data from a series of force plates. The data were analyzed further to determine temporal, speed, GRF, postural, mass distribution, moment, and collision dynamics parameters. Results. Fore-first, synchronous, and hind-first dissociations were found in horses trotting at (3.3 m/s ± 10%). In these speed-matched trials, mean centre of pressure (COP) cranio-caudal location differed significantly between the three dissociation categories. The COP moved systematically and significantly (P = .001) from being more caudally located in hind-first dissociation (mean location = 0.41 ± 0.04) through synchronous (0.36 ± 0.02) to a more cranial location in fore-first dissociation (0.32 ± 0.02). Dissociation patterns were found to influence function, posture, and balance parameters. Over a moderate speed range, peak vertical forelimb GRF had a strong relationship with dissociation time (R = .594; P < .01) and speed (R = .789; P < .01), but peak vertical hindlimb GRF did not have a significant relationship with dissociation time (R = .085; P > 0.05) or speed (R = .223; P = .023). Discussion. The results indicate that at moderate speeds individual horses use dissociation patterns that allow them to maintain trunk pitch stability through management of the cranio-caudal location of the COP. During the hoof-ground collisions, reduced mechanical energy losses were found in hind-first dissociations compared to fully synchronous contacts. As speed increased, only forelimb vertical peak force increased so dissociations tended towards hind-first, which shifted the net COP caudally and balanced trunk pitching moments.

No MeSH data available.


Related in: MedlinePlus