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Updated: Jul 14, 2026

In Vivo Canine Muscle Function Assay
Published on: April 5, 2011
Epaxial muscle function in trotting dogs.
D A Ritter1, P N Nassar, M Fife
1Biology Department, Heidelberg College, 310 E. Market Sreet, Tiffin, OH 44883, USA. Dale_Ritter@Brown.edu
Mammalian epaxial muscles, crucial for locomotion, were studied in dogs. These muscles primarily counteract trunk flexion during the hindlimb support phase, rather than stabilizing against ground reaction forces.
Area of Science:
- Comparative biomechanics
- Vertebrate locomotion
- Mammalian anatomy
Background:
- Epaxial muscles are a key differentiator in mammals, yet their precise role in locomotion remains unclear.
- Understanding epaxial muscle function is vital for comprehending terrestrial vertebrate movement.
Purpose of the Study:
- To investigate the locomotor function of epaxial muscles (iliocostalis, longissimus dorsi, multifidus) in dogs.
- To elucidate the role of these muscles in trunk movement and stability during trotting.
Main Methods:
- Recorded electrical activity of epaxial muscles at lumbar and thoracic sites in trotting dogs.
- Quantified footfall patterns and trunk kinematics using high-speed video analysis.
- Measured ground reaction forces using force plates to correlate muscle activity with locomotor mechanics.
Main Results:
- Epaxial muscles exhibited a biphasic (double-burst) activity pattern, with exceptions in the thoracic iliocostalis.
- Muscle activity peaked during the latter half of the ipsilateral hindlimb support phase (30% of cycle) and contralateral hindlimb support phase (15% of cycle).
- Analysis suggested epaxial muscles counteract trunk flexion, not directly stabilize against ground forces.
Conclusions:
- Epaxial muscles play a significant role in controlling sagittal plane trunk dynamics during locomotion.
- The findings challenge previous assumptions about epaxial muscle function in trunk stabilization.
- Further research, including loading experiments, supports the hypothesis of epaxial muscles counteracting trunk rebound.
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