The impact of water depth and speed on muscle fiber activation of healthy dogs walking in a water treadmill

Background Water treadmills are frequently used in the rehabilitation of dogs, for example with the purpose of re-building muscular strength after surgery. However, little is known about how different water depths and velocities affect the muscular workload during aquatic locomotion. This study used acoustic myography to assess hind limb muscle fiber activation in 25 healthy large-breed dogs walking in a water treadmill. Acoustic myography sensors were attached to the skin over the vastus lateralis of the quadriceps and the biceps femoris muscles. The dogs walked at two velocities (30 and 50 m/min) and four water depths: bottom of the pads, hock, stifle and mid-femur. Acoustic myograph signals were analyzed for changes in three muscle function parameters: efficiency/coordination (E-score) and spatial (S-score) and temporal (T-score) summation. Results Differences between E, S, and T were statistically significant compared across different speeds (30, 50) and water levels (0, 1, 2, 3) using a one-way ANOVA with multiple comparisons (Tukey; Geisser-Greenhouse correction) as well as a two-tailed one sample t-test. At 50 m/min in water at the mid-femur, the biceps femoris was less efficient (P < 0.001) and recruited more fibers (P = 0.01) at a higher firing rate (P = 0.03) compared to working in shallower water, while the vastus lateralis was also less efficient (P < 0.01), but spatial and temporal summation did not change significantly. At 30 m/min, biceps efficiency was reduced (P < 0.01) when water was at the mid-femur compared to the bottom of the pads level. Walking in stifle- or hock-deep water did not show increased muscle activation for either muscle compared to walking in water at the bottom of the pads. Conclusion More muscle activation was required to walk in water at a depth at the level of the mid-femur compared to shallower water, and this exercise was more demanding for the biceps femoris, a muscle engaged in propulsion, than for vastus lateralis. These findings may help practitioners towards making more precise rehabilitation protocols.

Effect of tibial plateau levelling osteotomy and rehabilitation on muscle function in cruciate-deficient dogs evaluated with acoustic myography

The objective of the study was to determine the function of the biceps femoris, quadriceps, gastrocnemius and semitendinosus muscles at the walk in dogs with unilateral clinical cruciate disease and palpable joint instability. To compare function before and after a tibial plateau levelling osteotomy (TPLO) procedure, and after six weeks of subsequent rehabilitation therapy. Fourteen adult client-owned dogs with cranial cruciate ligament deficiency (CCLD). Orthopaedic examination, temporospatial gait analysis and acoustic myography (AMG) recordings were made at three time points: before TPLO, and post-operatively at two and eight weeks. A rehabilitation program started 2 weeks after surgery and was either in-clinic along with in-home rehabilitation or in-home only. Statistics included: repeated measures ANOVA and paired t-tests. Significance was set at P<0.05. When comparing the affected versus the unaffected limb in the CCLD dogs, there were no significant differences found in AMG values between baseline and other time points for the quadriceps and semitendinosus muscles. The gastrocnemius and biceps femoris muscles had a significant change in spatial summation (S) score over time. The gastrocnemius (S) score was not significantly different to the unaffected limb by 8 weeks post TPLO. There was no significant effect of rehabilitation method on S score. Dogs with in-clinic rehabilitation regained more symmetry in thigh circumference versus in-home only. Lameness parameters improved but did not completely resolve in all dogs by week 8 post TPLO. The function of the gastrocnemius muscles in affected limbs was significantly different to normal limbs at baseline and 2 weeks post TPLO but not at 8 weeks. Thigh symmetry, but no other parameters, was improved with the addition of in-clinic rehabilitation.

Altered muscle activation in agility dogs performing warm-up exercises: an acoustic myography study

Agility is physically demanding and dogs encounter a considerable risk of injury during training and competition. Pre-performance warm-up is used routinely among human athletes to prepare the tissues for these physical demands, but in canine sports evidence for effects of warm-up is lacking. The aim of this study was to investigate the effects of warm-up in dogs on two major muscles involved in locomotion. It was hypothesised that, after warm-up, the muscles would be used more efficiently (more fibre resting time/total time), recruit fewer fibres (reduced spatial summation) and/or activated with a lower firing frequency (reduced temporal summation). The following factors ‘sex, age, weight, height, training level and agility experience’ were evaluated for their potential impact on muscle function parameters. Fourteen large (≥46 cm at the withers) agility dogs of different breeds and training levels performed a 5 min warm-up program three times, with a 2 min break between the programs for recording purposes. Acoustic myography sensors were attached on the skin over the muscles m. triceps brachii (TB) and m. gluteus superficialis (GS). Recordings of muscle activity were made, while the dogs trotted before warm-up and after each 5 min warm-up program. The dogs used TB more efficiently after 5 min (P<0.05), 10 min (P<0.05) and 15 min (P<0.001) of exercise compared to pre-warm-up values. No changes were found in the activity of GS. For well-trained dogs, TB recruited fewer muscle fibres after 10 and 15 min of warm-up compared to dogs that trained less than 1 h weekly (P<0.03). For dogs with more than 2 years of experience, GS had a lower firing frequency before and after 10 min warm-up compared to dogs with less experience. The results indicate that warm-up alters muscle activation by an increased muscular efficiency. Training level and experience have an influence on muscle function parameters.