We are familiar with repetitive strain injuries or repetitive motion disorders which can afflict humans. These disorders include chronic muscle strain injuries, myalgia (chronic muscle pain) and tendinosis (tendon pathologies).

Likewise, our dogs can also experience similar muscle strain disorders. Animal studies have found that continued performance of a task resulted in an initial inflammatory response which is accompanied by pain and discomfort. With continued performance of the task, the injury progressed to degeneration of musculoskeletal and neural structures and / or fibrosis (development of excessive connective tissue) along with a decline in task performance.

What causes repetitive strain injuries in dogs?

The causes of repetitive strain injuries in dogs may include:

• Daily activities – Chasing a ball, running up and down stairs, jumping, running on slippery surfaces, jumping into and out of the car or furniture, digging, spinning
• Sports activities – Jumping (particularly landing), heeling on one side only, carrying heavy loads, turning repetitively in one direction, contacting a flyball box.
• Multiple small acute traumas (e.g. slips, bumps, trips) causing small injuries which have a cumulative effect.

Can massage and manual therapy reduce inflammation?

A study with rats investigated how manual therapy affects the body’s early inflammatory response and fibrogenic phases following performance of a repetitive task. It is thought that by attenuating inflammation in the early stage, the development of fibrosis and other symptoms can be prevented. The study predicted that rats performing repetitive tasks would exhibit behavioural changes indicative of pain along with increased activity in nociceptors (receptors of noxious stimuli) which is also an indicator of pain in the affected limb.

The study involved 34 rats that were divided into four groups as follows:

• Control group
• High repetition, high force task group (HRHF) – This group trained for five weeks before testing.
• High repetition, high force – treated group – This group was also trained for five weeks before testing. They received manual therapy three times per week during the testing period.
• Food restricted control group – This group were used only for weight comparison purposes.

The rats were trained to operantly perform a reaching and pulling task. The animals were required to reach, at shoulder height, and pull a lever, in doing so performing an isometric contraction. The rats were rewarded for each successful attempt. The task was voluntary, so the rats could choose to participate.

Following an initial five week training period, there was a three week performance phase. During this phase, the rats undertook four by .5 hour sessions in a day with 1.5 hours rest between sessions. The sessions were performed three days / week for the three week period.

During the test period, the treated group received a five minute manual therapy session per task performance day. The treatment comprised mobilisation of the forearm, skin rolling and stretching in both forelimbs.

How did massage and manual therapy affect task performance, inflammation and pain?

Task performance

• Reach rate (Reaches / minute) – The highest reach rates were observed in weeks 1 and 3 of the HRHF treated group.
• Reach impulse (Force exerted when pulling and grasp duration) – Highest reach impulse was observed in HRHF treated group in week 3.
• Number of successful attempts – The greatest number of attempts was observed in week 3 of the HRHF treated group.

Sensorimotor changes

• Grip strength – Grip strength declined after five weeks of the training period before manual therapy treatment commenced. The declines in grip strength observed in HRHF (untreated) group remained until the end of the testing period. However, in the treated group, grip strength was restored by week 3 (end of the testing period).
• Behaviour changes – There was a higher proportion of rats in the untreated HRHF group that showed behaviour changes including: * switching limbs to pull the lever * pulling with one or two digits so not fully gripped * forelimb guarding

Electrophysiology

The study examined the rats’ median nerve for ongoing activity in neurons. Ongoing activity indicates the presence persistent pain or discomfort. The proportion of nerve units with ongoing activity was higher in the HRHF group, 22% vs 0% in the control group and 8% in the HRHF group that received treatment.

Inflammation can induce ongoing activity in the nociceptor axons. The indicator for inflammation in the median nerve was the presence of CD68 macrophages which are immune-positive macrophages. The HRHF group showed a greater concentration of CD68 macrophages compared with the control and treated groups. There was also an increase in neutrophils in the HRHF group and not other groups.

Finally, when nerves are injured, collagen and connective tissue increases around the structure. An examination of the median nerve showed an increase in the insulating layer around the nerve fibre in the HRHF group. This group showed increased collagen around the median nerve branches at the wrist and forepaw distal to the wrist. Some of the treated group also showed some fibrosis however it was far more pronounced in the untreated group.

Tips to prevent repetitive strain injuries in dogs

Provide sufficient healing time

Providing dogs that perform repetitive tasks, sufficient time to rest and heal will enable inflammation from muscle strain to resolve itself. Accompanying rest with cryotherapy may aid the dog’s recovery.

For more information on when to use cold therapy, please see: http://www.fullstride.com.au/blog/cold-packs-for-dogs

Avoid unnecessary repetitive tasks

Where possible, manage the dog’s environment or ask the dog to perform alternative behaviours so they are not performing unnecessary repetitive tasks which may result in repetitive strain injuries.

Examples of managing the environment may include the following:

• Laying non-slip flooring to prevent slips and falls
• Installing baby gates so dogs negotiate stairs calmly and safely
• Installing steps or ramps to prevent jumping up and down from furniture or out of the car

Examples of alternative behaviours may include the following:

• Training the dog to perform behaviours on both sides or directions. For example, teaching the dog to spin in both directions, walking on your right side as well as your left, turning in both directions to pick up a ball or retrieve object.
• Introducing games that require more varied movement. For example, instead of throwing a ball for the dog to chase, ask the dog to find the ball hidden in an object or room in the house.

Introduce manual therapy as a preventative measure

This study concluded that introducing manual therapy (massage, stretching and mobilisations) prior to severe symptoms being observed prevents and restores injurious changes in function, task performance and tissue integrity. Treatment also prevents inflammation and neural fibrosis and therefore improves function and reduces the severity of symptoms of repetitive motion disorders.

This study showed that the manual therapy intervention prevented the following in rats performing a repetitive task:

• Functional declines – The treated group showed improved task performance through the course of the testing period as evidenced by increases in grip strength in week 3.
• Behaviour changes indicating discomfort
• Neural inflammation and extra-neural fibrosis

These results are contrasted with the untreated group which demonstrated the following symptoms:

• irregular ongoing neural activity consistent with the effect of inflammation on nociceptor axons within the peripheral nerves

• significantly greater number of activated macrophages in the median nerve indicating neuro-inflammation

• increased fibrosis around the median nerve branches which likely impedes normal sliding of the structures over another and may become a source of inflammation and pain when performing tasks.

The study concluded that repetitive task performance induces inflammation. It is thought that repetitively overloading the muscles causes injury and while inflammation is the body’s normal response to injury, without sufficient healing time, inflammation becomes persistent as it is re-introduced with each performance of the task. It is believed that chronic inflammation will lead to all the other symptoms observed in the current study.

To maintain your dog’s performance and mobility, Full Stride provides canine massage, treatments including mobilisation, stretching and passive range of motion. Treatments are offered in the dog’s home (within a service area) or at a treatment room on Brisbane’s north.

To find a qualified canine myofunctional therapist in your local area please see www.saena.com.au.

Until next time, enjoy your dogs.

Source:

Bove, G. M., Delany, S. P., Hobson, L., Cruz, G. E., Harris, M. Y., Amin, M., … & Barbe, M. F. (2019). Manual therapy prevents onset of nociceptor activity, sensorimotor dysfunction, and neural fibrosis induced by a volitional repetitive task. Pain, 160(3), 632-644.

Image by: Karsten Kettermann from Pixabay