Effect of multiday endurance exercise on total body water and calculated body composition in racing sled dogs

Abstract

Prolonged multiday exercise in dogs is often associated with a caloric deficit that can lead to changes in body composition but may also result in an increase in lean body mass due to a conditioning effect. To test the hypothesis that multiday exercise decreases fat mass but increases lean body mass, body composition was measured using deuterium oxide dilution in a team of racing Alaskan sled dogs competing in a multiday race. Twelve dogs completed 961 km in 6 days, resulting in a 3% decrease in body mass (P=0.003) and 16% decrease in body fat (P=0.005), and an increase in total body water as a fraction of body mass (P=0.01). Within the study population, there was considerable dog-to-dog variation, with 2 dogs gaining fat mass and 2 dogs losing over 40% of their pre-race fat mass during the measurement period. These results confirm that dogs participating in multiday exercise events are at risk for loss of body fat reserve, likely due to a net calorie deficit. However, individual dog responses to an exercise challenge can be highly variable, emphasizing the need for careful assessment of individual dogs.

Thermal relations in sled dogs before and after exercise

“…Athletic animals are those that have an overall greater level of physical fitness, measured by VO 2max values that are above average, indicating superior aerobic endurance (Poole et al, 2005). Sled dogs in particular have been noted to burnup to 11,250 kcal/day during long term bouts of exercise, (Davis, 2021, 2023; Hinchliff et al, 1997). As a result, the heat dissipation requirements are so great that, in human athletes, effective thermoregulation is the most pressing challenge during physical activity due to the large number of muscles contracting, and generating heat (El Helou et al, 2012; Lieberman & Bramble, 2007).…”

“…Athletic animals are those that have an overall greater level of physical fitness, measured by VO 2max values that are above average, indicating superior aerobic endurance (Poole et al, 2005). Sled dogs in particular have been noted to burnup to 11,250 kcal/day during long term bouts of exercise, (Davis, 2021(Davis, , 2023Hinchliff et al, 1997).…”