Laurie's Blogs.

I want to preface this blog by staying that there is a study that has come out recently that is actually a follow-up / tag on study to this one.  The new study is about trotting, but reviewing available literature, I found this study about walking and realized that I hadn't reported on it before.  So, to me, it seems that this was a good starting point.  Next week, we'll look into the more recent study.  Enjoy!

Shoulder pathology is a frequent reason for presentation to veterinary sports medicine and rehabilitation practices. Surveys and retrospective studies have identified the shoulder as a commonly injured joint in agility, flyball, racing, canicross, and sled dogs. Supraspinatus and bicipital tendinopathies are among the conditions often managed conservatively. The authors note that standardized rehabilitation protocols for shoulder injury are lacking, while controlled walking on level ground, inclines, or declines is recommended in nearly every recovery program.

Most canine electromyography (EMG) studies of therapeutic exercise have examined hindlimb musculature. Forelimb data during early recovery tasks such as incremental incline and decline treadmill walking have been limited. Cain and colleagues designed this study to measure peak and average activity of selected thoracic-limb muscles during walking at five treadmill positions: level, 5% incline, 10% incline, 5% decline, and 10% decline. They hypothesized that forelimb muscle activity would be higher during decline walking than level walking and lower during incline walking.

Study design

Twelve clinically sound dogs were enrolled after orthopedic and neurologic examination and force-platform screening for asymmetry. Usable EMG recordings were obtained from nine dogs. Walking speed was 3.0 km/h. Fine-wire EMG was used for the supraspinatus. Surface EMG was used for the scapular portion of the deltoideus, biceps brachii, and the lateral head of the triceps brachii. Signals from ten gait cycles at each position were processed and compared.

Findings

The hypothesis was only partly supported.

Average supraspinatus activity increased during decline walking relative to level walking. Reported increases were 14.5% at 5% decline and 29.4% at 10% decline, with an additional increase between the two decline grades. Average supraspinatus activity decreased between 5% and 10% incline.

Average and peak deltoideus activity also increased during decline walking. The authors reported larger average increases at the steeper decline.

Peak and average activity of the biceps brachii and of the lateral head of the triceps brachii did not differ significantly across treadmill positions. Trends for the triceps resembled the supraspinatus pattern (higher on decline, lower on incline) but did not reach statistical significance.

Discussion points from the paper

The authors interpret the decline-related increase in supraspinatus and deltoideus activity as consistent with greater forelimb braking and stabilization demand when walking downhill. They interpret the reduction in average supraspinatus activity with a steeper incline as consistent with reduced forelimb deceleration demand as work is shifted caudally.

They emphasize two practical observations drawn from their data. First, incremental changes in treadmill grade (5% versus 10%) altered average supraspinatus activity. Second, decline walking increased both average and peak deltoideus activity. They state that these effects should be considered when developing therapeutic exercise plans for dogs with shoulder injury.

The absence of significant biceps and lateral triceps changes at a walk is discussed as a finding in its own right. The authors note that steeper grades or other tasks may be required to alter those muscles, and that sample-size limitations and surface-EMG artifact may have reduced the ability to detect smaller effects.

Limitations identified in the paper include a reduced number of acceptable EMG recordings after signal dropout, possible differences between treadmill and over-ground walking, within-dog variability, and the use of sound dogs rather than clinical shoulder cases.

Conclusion of the paper

Decline walking increased muscle activity in the supraspinatus and deltoideus. Incline walking reduced average supraspinatus activity between the 5% and 10% grades. Biceps brachii and lateral triceps activity did not change significantly across the five walking positions tested. The authors conclude that incremental treadmill positions at the walk provide information that can be used when planning exercise for canine shoulder conditions.

Reference

Cain, R. M., Stanford, K., Drum, M., Richards, J., Levine, D., Millis, D., & Ursini, T. (2025). Forelimb muscle activity during level and progressive incline and decline walking in dogs and implications for rehabilitation. Frontiers in Veterinary Science, 12, Article 1649009. https://doi.org/10.3389/fvets.2025.1649009