Stiftung Tierärztliche Hochschule Hannover Die ontogenetische ...
Stiftung Tierärztliche Hochschule Hannover Die ontogenetische ... Stiftung Tierärztliche Hochschule Hannover Die ontogenetische ...
Studie II: Shift of the CoM in growing dogs 3.4. Animals and Methods Dogs Six male Beagle siblings (Canis lupus familiaris, Linnaeus 1758) from the same litter were used in this longitudinal study. The dogs were from a breeding colony of the University of Veterinary Medicine Hannover (Germany) and came to the Small Animal Clinic at the age of 9 weeks (i.e., PW9). During the study period, all dogs underwent two standard orthopedic exams, one at PW14 and one at PW50, which confirmed that the dogs were sound. For the gait analysis, the puppies were gently introduced to ambulating on the treadmill when they were 9 weeks old. All experiments were carried out in accordance with the German Animal Welfare guidelines and notice was given to the Ethics committee of Lower Saxony (Germany). Data collection GRF measurements started at PW9 and continued until PW51. Data were collected weekly up to PW20, fortnightly up to PW32 and monthly henceforth. Additionally to the GRF recordings, various morphometric measurements (e.g., segment and limb lengths) were taken for a related study (Helmsmüller et al., subm.) and the dogs were photographed in lateral perspective standing as balanced and square as possible (Fig. 1). From all recordings, data from PW11, 13, 19, 22, 26, 30, 43 and 51 were selected for further analysis. Two dogs could not participate in the data collection at PW19 and were therefore measured the following week (i.e., PW20). During GRF data collection, the dogs trotted on a horizontal treadmill with four separate belts and integrated force plates underneath each belt (Model 4060-08, Bertec Corporation, Columbus, OH, USA). Because of their small body size, the puppies trotted on one side of the treadmill allowing the forces exerted by the foreand the hindlimbs to be recorded separately (sample rate 1,000 Hz). Separate force curves for the left and the right limbs were nevertheless obtained because the duty factor was less than 0.5 during all recordings. To identify whether the right or the left 54
Studie II: Shift of the CoM in growing dogs limbs were exerting force, a digital camera synchronized with the GRF recordings imaged the dogs from the lateral perspective (NVGS60, Panasonic). Kinetic data were collected and analyzed using Vicon Nexus (Vicon Motion Systems Ltd., Oxford, UK). During each session, at least 3 trials per dog were obtained lasting about 30 seconds and covering approximately 65 strides. Of these, 10 valid steps (i.e., without overstepping) were analyzed per dog and age. The selected strides were not always consecutive because the dogs, particularly when very young, did not run as consistently as when they were older. Touch down and lift off events were determined manually using the vertical force curves; force threshold was set at 5% of the dog’s body weight. Then, the force data were time-normalized to 100% stance duration (i.e., 101 data points) using linear interpolation and exported to Microsoft Excel together with the temporal gait parameters (i.e., stance duration in s). Data analysis Vertical force data from the 10 steps were averaged per dog and normalized to the dog’s body weight (BW) using equation (1): (1) GRFs (%BW) = vertical force*100/(body mass*9.81 m/s2) The vertical GRF parameters compared among the ages were peak and mean vertical force as well as vertical impulse. Additionally, symmetry indices for the foreand hindlimbs, time to peak vertical force (in % stance duration) and the distribution of the dog’s body weight among the four limbs were determined. Body weight distribution was calculated using equation (2): (2) % BW bearing = vertical force of the limb/total vertical force of all limbs*100 Symmetry indices (SI) were determined using equation (3) (according to Herzog et al., 1989): (3) SI = 100 * (Xl - Xr)/(0.5* (Xl + Xr)) with X being the vertical force of the left (l) and right (r) fore- or hindlimb averaged across the ten steps. Furthermore, the ratio of the stance times of the fore- and hindlimbs (i.e., forelimb stance time divided by hindlimb stance time) were determined. 55
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Studie II: Shift of the CoM in growing dogs<br />
limbs were exerting force, a digital camera synchronized with the GRF recordings<br />
imaged the dogs from the lateral perspective (NVGS60, Panasonic).<br />
Kinetic data were collected and analyzed using Vicon Nexus (Vicon Motion<br />
Systems Ltd., Oxford, UK). During each session, at least 3 trials per dog were<br />
obtained lasting about 30 seconds and covering approximately 65 strides. Of these,<br />
10 valid steps (i.e., without overstepping) were analyzed per dog and age. The<br />
selected strides were not always consecutive because the dogs, particularly when<br />
very young, did not run as consistently as when they were older. Touch down and lift<br />
off events were determined manually using the vertical force curves; force threshold<br />
was set at 5% of the dog’s body weight. Then, the force data were time-normalized to<br />
100% stance duration (i.e., 101 data points) using linear interpolation and exported to<br />
Microsoft Excel together with the temporal gait parameters (i.e., stance duration in s).<br />
Data analysis<br />
Vertical force data from the 10 steps were averaged per dog and normalized to the<br />
dog’s body weight (BW) using equation (1):<br />
(1) GRFs (%BW) = vertical force*100/(body mass*9.81 m/s2)<br />
The vertical GRF parameters compared among the ages were peak and mean<br />
vertical force as well as vertical impulse. Additionally, symmetry indices for the foreand<br />
hindlimbs, time to peak vertical force (in % stance duration) and the distribution<br />
of the dog’s body weight among the four limbs were determined. Body weight<br />
distribution was calculated using equation (2):<br />
(2) % BW bearing = vertical force of the limb/total vertical force of all limbs*100<br />
Symmetry indices (SI) were determined using equation (3) (according to Herzog et<br />
al., 1989):<br />
(3) SI = 100 * (Xl - Xr)/(0.5* (Xl + Xr))<br />
with X being the vertical force of the left (l) and right (r) fore- or hindlimb averaged<br />
across the ten steps. Furthermore, the ratio of the stance times of the fore- and<br />
hindlimbs (i.e., forelimb stance time divided by hindlimb stance time) were<br />
determined.<br />
55
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