There is increasing interest in assessing the behaviors of companion dogs in their routine environment, at home with their owners, and many of these behaviors are associated with a dog's degree of activity.1–3 Mobility and spontaneous activity can be altered such that owners notice a decrease in dog activity with conditions such as cardiac disease or osteoarthritis or an increase in dog movements with conditions that cause pruritus.2–5 An objective method to assess the degree of activity in dogs in their typical environment could be useful for monitoring disease status or the efficacy of an intervention designed to treat a disease or its signs.
Activity monitors have been used to record locomotor activity rhythms in laboratory dogs (predominantly Beagles),6–9 and they can be used in companion animals to determine the efficacy of interventions or to monitor the progression of disease by comparing 7-day intervals of activity over time.4,10,11 In Beagles, age and housing environment can affect degree of activity.6–9 In companion dogs, the home environment affects activity as well. Dogs appear to have increased activity on weekends versus weekdays, presumably because of increased availability of owners for interaction.11 To the authors' knowledge, the effect of age on the counts measured by an activity monitor in companion dogs has not been investigated.
An additional potential confounding variable in the assessment of degree of activity in companion dogs is body conformation. Various accelerometers have been extensively investigated as a means of monitoring physical activity in humans. Factors such as body type and locomotor characteristics are important sources of inter-subject variation. Consequently, these devices must be validated for different populations (eg, children of various ages, adolescents, or adults).12–16 The intersubject variation reported for humans has implications for the use of accelerometers for monitoring activity in dogs given the enormous amount of natural variation in body length, body circumference, and limb length in this species. This aspect of activity monitoring in dogs has not been addressed in investigations that have involved laboratory subjects, presumably because of the uniformity of conformation among Beagles. However, it is important to know whether any aspect of signalment or body conformation could confound the results of activity monitoring in companion dogs if these monitors are to be used as an outcome assessment tool for evaluation of the presence, progression, or treatment of disease. If confounding variables are identified, they can be controlled for in the design and the statistical analysis of studies in which activity monitors are used.
The purpose of the study reported here was to evaluate the effect of signalment and body conformation on the outcome of activity monitoring in a heterogeneous group of companion dogs. Our hypothesis was that when given some control over the amount of effort involved in their activity (ie, trotting on stairs), older dogs would have lower activity counts than younger dogs. In addition, we hypothesized dogs with shorter limbs would have higher activity counts than dogs with longer limbs when performing the same activities.
Actical Activity Monitor, Philips Respironics Co, Bend, Ore.
Stata, version 10, StataCorp, College Station, Tex.
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