Limb and back muscle activity adaptations to tripedal locomotion in dogs

Abstract

Alterations in muscle recruitment are key to the functional plasticity of the mammalian locomotor system. One particularly challenging situation quadrupeds may face is when the functionality of a limb is reduced or lost. To better understand how mammals manage in such situations and which muscular adaptations they exhibit when locomoting on three legs, we recorded the activity patterns of two limb and one back extensor muscle in nine dogs using surface electromyography. We compared the timing and the level of recruitment before and after the loss of a hindlimb was simulated. Both the intensity and the timing of the activity changed significantly in the m. vastus lateralis of the remaining hindlimb, consistent with this limb bearing a greater proportion of the body weight as well as with previously reported kinematic changes. In accordance with the greater body weight supported by the forelimbs, the m. triceps brachii showed first and foremost an increased level of excitation. The very asymmetrical changes in the timing and the level of activity in the m. longissimus dorsi reflects the highly asymmetrical functional requirements imposed on the trunk and the pelvis when one hindlimb is no longer involved in the production of locomotor work while the other hindlimb partially compensates the loss. Integration of our electromyographical findings with kinetic and kinematic results illustrates that dogs exhibited a well-coordinated response to the functional requirements of tripedalism and underlines the importance of moment-to-moment modulation in muscular recruitment for the functional plasticity of the mammalian locomotor system.

Displacement of center of mass in dogs in response to foot sensory stimulation

“…This is similar to previously reported shifts in body‐weight distribution after forelimb amputation 30 . In addition, the CoM shifted forward and to the opposite side of the median plane when a hindlimb was suspended, resembling body‐weight shifts observed after hindlimb amputation 31 . We compared body weight before and after suspension to confirm that suspension did not create an artifact in body weight.…”

“…30 In addition, the CoM shifted forward and to the opposite side of the median plane when a hindlimb was suspended, resembling body-weight shifts observed after hindlimb amputation. 31 We compared body weight before and after suspension to confirm that suspension did not create an artifact in body weight. According to previous reports, the change in the CoM to restore balance is caused by compensatory responses controlled by internal or external mechanisms, and similar results were observed in our study.…”

Kinematic adaptions to induced short-term pelvic limb lameness in trotting dogs

“…Invited by the observations that dogs shift their centre of body mass, alter their external forces, adapt their temporal gait parameters and change the recruitment patterns of their limb and back extensor muscles in strikingly similar ways when coping with a partial or total loss of limb function [ 10 , 12 , 33 , 35 – 37 ], we hypothesized that dogs may utilize similar principles to biomechanically compensate for reduced or lost limb functions. If that were true, we would expect the gait alterations observed when limb load was reduced ([ 10 ]; this study) to be suggestive of the gait changes observed when limb load was zero [ 16 , 36 ].…”

The effect of limb amputation on standing weight distribution in the remaining three limbs in dogs

“…It is possible that other underlying pathology was present that could have affected our results. However, several recent studies describing kinetic changes after limb amputation have similarly used a physical examination as a screening tool for neurological and orthopaedic disease (3)(4)(5)(6).…”

“…In addition, forelimb amputees tend to have more difficulty maintaining their balance, whereas hindlimb amputees tend to have more difficulty gaining speed (3,4). In addition, electromyographic data suggest that dogs compensate to a three-limbed gait with a significant increase in vastus lateralis and triceps brachii activity as compared to other hindlimb and forelimb muscle groups, respectively (5). Another study of kinetics and kinematics after limb amputation revealed that there is a significant increase in weight bearing on each remaining limb, but no significant changes in range of motion of the remaining joints (6).…”