The sled dog is one of the most studied canine athletes in veterinary and physiological research.

Since the 1990s, dozens of studies have been conducted on dog populations participating in major ultra-endurance races, particularly the Iditarod Trail Sled Dog Race in Alaska and the Yukon Quest.

Today, this data constitutes a solid scientific body of knowledge on energy expenditure, musculoskeletal injuries, digestive disorders, and the specific metabolism of these animals.

In France, mushing is developing in three distinct forms:

• organized competition,
• personal leisure,
• commercial tourism.

These three contexts involve very different levels of physical constraint for the dogs but share common health challenges that veterinary literature can now accurately document.

The French context: FFST, FFPTC and supervised practices

In France, sled dog and dog traction sports are mainly organized around two structures.

The French Federation of Sled, Ski/MTB-joëring and Canicross Sports (FFST), created in 1986, is the delegated federation for the disciplines concerned and a member of the International Federation of Sleddog Sports (IFSS).

It welcomes traction dogs of various morphologies, including Alaskan Husky or Eurohound crossbreeds, in its competitions.

The French Federation of Pulka and Sled Dogs (FFPTC), created in 1984, presents itself as a federation dedicated to Nordic breeds; its regulations limit certain race categories to the six recognized Nordic breeds or, depending on the categories, to dogs typical of these breeds.

The disciplines practiced include snow sledding in sprint, mid-distance, and long-distance, as well as canicross, skijoring, bikejoring, and dryland disciplines on land.

The FFST was founded following a split within the FFPTC, with a number of clubs rejecting the principle of excluding Alaskan-type crossbreed dogs.

The FFST's technical regulations specify that harnesses must be well-fitting, made of flexible webbing, and padded at least around the neck and chest, to allow for respiratory amplitude consistent with the effort.

Breeds used: a contrasting overview

The breeds involved in sled dog and dog traction sports cover a very wide spectrum, ranging from ancestral Nordic breeds to crossbreed competition dogs specifically developed for performance.

The Siberian Husky is one of the most common breeds in France for recreational mushing. An FCI Group 5, Section 1 breed (Nordic sled dogs), it is characterized by a light morphology, moderate sexual dimorphism, and the ability to exert moderate speed over long distances.

Its popularity as a pet far exceeds the mushing sphere, which raises issues of suitability between the needs of the breed and the living conditions offered.

The Alaskan Malamute is a significantly heavier breed, weighing between 34 and 43 kg according to the FCI standard, historically selected for pulling heavy loads over moderate distances.

Less suited to speed competitions than the Husky, it is still used for recreational sledding and pulka. Its robust constitution and specific health profile, particularly endocrinological, warrant specific attention, which will be discussed later.

The Greenland Dog (Groenlandhund) is one of the oldest Nordic breeds, traditionally used in the Arctic for hunting and transportation. Robust, independent, with a capacity to work in extreme temperatures, it is present in some traditional mushing kennels but is poorly represented in modern competition.

The Samoyed, an FCI breed from the same group, is renowned for its endurance and cold tolerance. Historically used as a sled dog and herd guard dog in Siberia, it is now more present as a pet and in recreational sports than in high-level competition.

The Alaskan Husky deserves special mention. It is not a breed recognized by the FCI: it is a lineage of dogs empirically selected for over a century by North American competitive mushers, by crossing high-endurance breeds according to the desired aptitudes (Siberian Husky, Greyhound, Pointer, Labrador).

Alaskan Huskies dominate major ultra-endurance races such as the Iditarod and the Yukon Quest.

A genetic study on the breed composition and performance factors of the Alaskan Husky highlights that selection based on performance criteria has produced an animal metabolically distinct from pure Nordic breeds (Huson et al., BMC Genetics, 2010, PMID 20649949). It is on this population that the vast majority of available scientific data has been produced.

Visual representation of the different breeds mentioned above

Physiological constraints: extraordinary energy expenditure

The first physiological characteristic documented in ultra-endurance sled dogs is their extraordinary energy expenditure.

A reference study measured, using the doubly labeled water method, the total energy expenditure of 18 Alaskan dogs participating in a 490 km race at temperatures between -35°C and -10°C.

The total measured energy expenditure was 47,100 ± 5,900 kJ per dog per day, or approximately 11,250 ± 1,409 kcal, and the sustained metabolic rate of these dogs during the race was among the highest ever documented in a large mammal (Hinchcliff et al., American Journal of Veterinary Research, 1997, PMID 9401699).

Subsequent data confirm that the total energy expenditure of a sled dog during a race can exceed 500 kcal/kg of body weight over multi-day events (Davis, Integrative and Comparative Biology, 2021, PMID 33871632).

To meet these needs, the diet of dogs in ultra-endurance competitions is highly enriched in lipids and proteins.

Work carried out during the Yukon Quest confirms that energy requirements during the race are greater than 41,840 kJ (10,000 kcal) per dog per day under extreme racing conditions.

A remarkable result, stemming from a series of studies by Michael Davis's team (Oklahoma State University), concerns the glucocentric metabolism of these dogs.

Contrary to what a high-fat diet might suggest, recent data indicate that well-conditioned ultra-endurance dogs maintain a glucose-centered metabolism as their primary muscle fuel during submaximal exercise, with numerous conditioning-related adaptations aimed at preserving glucose supply despite a lipid-dominated diet (Davis, 2021).

This mechanism is still the subject of active research.

Documented pathologies: musculoskeletal injuries

Musculoskeletal injuries are the primary medical cause leading to the withdrawal of dogs from major ultra-endurance races.

A study of 989 dogs that participated in the Yukon Quest International between 2018 and 2020 analyzed the veterinary medical records of 711 dogs that were part of teams that completed the race.

Among them, 51.3% had at least one abnormality in their records during the race. Among the orthopedic injuries identified, shoulder injuries were the most frequent (n = 77), followed by carpal injuries (n = 59) and pelvic limb injuries (n = 32).

Carpal injuries were the most frequent among dogs that finished the race (71 out of 85 cases): 54.6% of dogs with carpal injuries were able to finish the race, compared to only 10.5% of dogs with shoulder injuries.

In total, 66.6% of dogs with an orthopedic injury were withdrawn from the race (Hattendorf, Davis, Hansen, Frontiers in Veterinary Science, 2024, PMID 38476168).

Carpal injury deserves particular attention in this context.

The dog's carpus is exposed to intense biomechanical stresses during repeated traction efforts over thousands of kilometers.

Carpal ligament lesions, which can progress to carpal hyperextension, are a well-described orthopedic pathology in active athletic dogs (Beierer, Veterinary Clinics of North America Small Animal Practice, 2021, PMID 33451806). In the context of sledding, surface conditions (hardened snow, ice, uneven terrain) exacerbate mechanical stresses with each paw strike.

Stress fractures, sprains, tendon tears, and muscle injuries are also documented in the literature on working and endurance dogs, with variations depending on the discipline practiced and terrain conditions.

In competition, there is a list of prohibited substances and methods established by the IFSS: a dog requiring treatment with a substance on this list must be withdrawn from the race by the race veterinarian.

Documented pathologies: paw pads and cold surfaces

Paw pads are a specific area of vulnerability for sled dogs, subjected to thousands of kilometers of direct contact with snow, ice, and abrasive surfaces. A biochemical and histopathological study of 26 Alaskan Huskies that covered 170 miles on snow documented tissue changes in the paw pads after exertion in the cold.

The forelimbs were subjected to a higher level of physical stress than the hindlimbs.

Wet snow and temperatures near 0°C caused more tissue stress than dry, hard snow at very negative temperatures (Bradley et al., Veterinary Dermatology, 1996, DOI 10.1111/j.1365-3164.1996.tb00247.x). This data highlights that surface conditions are not all equivalent in terms of paw pad risk, and that outings in thawing conditions can be more detrimental to the paw pads than outings in very cold weather.

Regular checking of the paw pad condition before and after each outing is a constant recommendation in all available field protocols. The use of protective booties is documented under certain conditions, provided they do not impair grip on unstable surfaces.

Documented pathologies: exercise-induced gastric ulcers

One of the most well-documented pathologies in competitive sled dogs is exercise-induced gastritis and gastric ulcers, referred to as Exercise-Induced Gastric Disease (EIGD). A review published in Frontiers in Veterinary Science synthesizes over fifteen years of studies on this topic (Davis and Williamson, Frontiers in Veterinary Science, 2016, PMID 27092307). Convergent data from seven distinct studies show that, in unmedicated sled dogs, between 50 and 70% exhibit endoscopically visible gastric lesions after at least one day of intense exercise, whether during long-distance training, mid-distance races, or ultra-endurance races. The mechanistic hypothesis currently accepted links exercise hyperthermia to an alteration of the gastric mucosal barrier as an early event in pathogenesis.

Gastric ulcers and their complications, including aspiration pneumonia and chronic blood loss, have been identified as a cause of death in competition. A study conducted on dogs participating in the 2002 Iditarod showed that omeprazole (proton pump inhibitor, 20 mg orally every 24 hours) significantly reduced the mean gastric severity score compared to placebo (0.65 vs 1.09, p = 0.028), but was associated with more frequent diarrhea (54% vs 21%, p = 0.017). Additional studies compared the efficacy of famotidine and omeprazole in racing conditions, concluding that omeprazole was superior in preventing severe lesions, with practical constraints related to its administration on an empty stomach in difficult field conditions (Davis et al., JVIM, 2003, PMID 12683615; Williamson et al., JVIM, 2007, PMID 17939544).

This pathology has also been identified in working dogs performing less extreme activities, particularly detection dogs subjected to simulated patrols. Therefore, it is not exclusively linked to ultra-endurance races.

Thyroid update: calibrating interpretation of test results

An important clinical peculiarity concerns thyroid hormone levels in sled dogs. A study measured thyroid parameters in 86 retired Alaskan dogs (9-13 years old), considered healthy on clinical examination and with no history of diagnosed hypothyroidism. The results show that 38% had total T4 below standard reference values, 45% had free T4 below, and 37% had T3 below, despite the absence of anti-thyroglobulin antibodies and TSH values within normal ranges. The authors conclude that sled dogs, whether active or retired, have their own population-specific thyroid reference values, and that applying standard reference values can lead to erroneous diagnoses of hypothyroidism (Frye et al., Frontiers in Veterinary Science, 2022, PMC9237528).

This observation is consistent with data establishing that T4 and free T4 concentrations vary significantly by breed: Siberian Huskies and Samoyeds exhibit higher average values than Golden Retrievers or Collies, while Alaskan Malamutes fall at an intermediate level (Hegstad-Davies et al., Journal of Veterinary Diagnostic Investigation, 2015, PMID 26472744).

In contrast, large-scale epidemiological data from a cohort of 905,553 dogs in the United Kingdom confirm that Alaskan Malamutes have an odds ratio of 9.71 for hypothyroidism diagnosis compared to crossbreeds, placing them fourth among the highest-risk breeds (O'Neill et al., Canine Medicine and Genetics, 2022, PMID 36217196).

These two sets of data are not contradictory: the Alaskan Malamute is indeed a breed predisposed to clinical hypothyroidism, but the interpretation of thyroid profiles in active or retired sled dogs requires reference values adapted to their population, to avoid over-diagnosis or under-diagnosis.

Leisure and Canicross: Different Constraints, Same Vigilance

The vast majority of available scientific data on sled dogs comes from populations in ultra-endurance competitions. Dogs participating in recreational mushing, canicross, or ski-joring at an amateur level are subjected to constraints of much lower intensity, but certain general principles apply.

Managing physical condition outside of the snow season is a documented practical issue: dryland disciplines (canicross, canicross biking, dog scootering) are used to maintain physical condition throughout the year.

Progressive training, pre-exercise warm-up, and post-exercise recovery are preventive practices consistent with available data in working dog populations, even if few studies have specifically evaluated them in recreational mushing dogs.

Weight monitoring is particularly relevant for Nordic breeds in a recreational or companion context: these breeds, selected for metabolic efficiency in conditions of limited rations, can gain weight easily when their activity level decreases. Excess weight exacerbates joint stress and metabolic risks.

The risk of heatstroke should not be overlooked outside of winter conditions. Nordic breeds are morphologically and physiologically adapted to cold, with dense coats and thermoregulation optimized for cold environments. In dryland disciplines practiced in hot or moderate temperatures, their ability to dissipate heat is limited, and the risk of exercise-induced hyperthermia is real.

Sled Dog Tourism: Regulation and Animal Welfare

Tourism activities with sled dogs, offered in alpine resorts, the Vosges, and the Pyrenees, constitute a commercial activity distinct from competitive sport and personal leisure.

In France, they fall under general animal welfare law and, depending on the exact operating procedures, may be subject to the obligations set out in Article L214-6-1 of the Rural and Maritime Fishing Code. 

The ACACED (Certificate of Knowledge for Companion Animals of Domestic Species), issued since 2016 by the DRAAF (Regional Directorate for Food, Agriculture, and Forestry) replacing the former CCAD, is now one of the reference systems for demonstrating the knowledge required for several professional activities involving companion animals.

When the activity takes place in communal forest areas not open to public traffic, a ministerial response published in the Official Journal of the Senate in September 2022 indicates that it is up to the municipality to authorize the activity through a forest occupation agreement, intended in particular to frame the authorized itineraries, the beneficiary's obligations, and liability issues.

In terms of animal welfare, tourist activities raise specific issues related to the repetition of efforts.

Unlike competition dogs led by an experienced musher who adapts the load in real-time, tourist dogs often make several outings a day with novice audiences, under varying guiding conditions, during a short and intensive winter season.

The daily repetition of these outings constitutes cumulative musculoskeletal stress whose preventive management remains poorly documented in scientific literature but falls within the same mechanisms as those highlighted in working dog populations.

Pad monitoring, body condition monitoring, musculoskeletal status, and adaptation of workload to climatic conditions and terrain are vigilant points consistent with available data, regardless of the level of practice.

Tourist mushing in France currently does not have a formalized sectoral animal welfare framework comparable to that existing for certain commercial equestrian activities. The applicable framework is based essentially on general animal protection obligations.

Prevention and Best Practices

Documented or recommended preventive practices for active sled dogs include regular orthopedic check-ups to detect early joint and ligament damage, systematic paw pad checks before and after each outing, year-round body condition management, warm-up and recovery protocols, and adaptation of distances and intensities to climatic conditions and the individual animal's fitness.

For dogs involved in long-distance competitions, the prevention of exercise-induced gastric ulcers is part of race veterinary protocols, with documented use of omeprazole in compliance with the list of prohibited substances and methods established by the IFSS.

For Nordic breed dogs in recreational or companion practice, the interpretation of biological assessments must take into account the specificities of these breeds, particularly for thyroid values in Alaskans and Nordic breeds, whose norms are not superimposable on standard reference values.

In Conclusion

Sled dogs constitute one of the most studied athletic populations in sports veterinary medicine.

Available data document exceptional exercise physiology, with one of the highest energy expenditures ever measured in a mammal, and well-characterized specific pathologies: musculoskeletal injuries dominated by shoulder and carpal injuries, exercise-induced gastric ulcers, and foot injuries related to cold surfaces.

For the practicing veterinarian in France, the diversity of breeds and practices requires adapting the clinical approach to each animal's profile: ultra-endurance competition dogs, recreational Nordic dogs, or tourist dogs do not present the same constraints or the same reference biological values.

Main Sources

1. FFST, federal presentation and technical regulations 2024-2025
2. FFPTC, federal presentation and race regulations
3. FCI standards n°270 (Siberian Husky), n°243 (Alaskan Malamute) and n°212 (Samoyed)
4. Huson et al., BMC Genetics, 2010, PMID 20649949
5. Hinchcliff et al., American Journal of Veterinary Research, 1997, PMID 9401699
6. Davis, Integrative and Comparative Biology, 2021, PMID 33871632
7. Hattendorf et al., Frontiers in Veterinary Science, 2024, PMID 38476168
8. Beierer et al., Veterinary Clinics of North America: Small Animal Practice, 2021, PMID 33451806
9. Bradley et al., Veterinary Dermatology, 1996, DOI 10.1111/j.1365-3164.1996.tb00247.x
10. Davis & Williamson, Frontiers in Veterinary Science, 2016, PMID 27092307
11. Davis et al., JVIM, 2003, PMID 12683615
12. Williamson et al., JVIM, 2007, PMID 17939544
13. Frye et al., Frontiers in Veterinary Science, 2022, PMC9237528
14. Hegstad-Davies et al., Journal of Veterinary Diagnostic Investigation, 2015, PMID 26472744
15. O'Neill et al., Canine Medicine and Genetics, 2022, PMID 36217196
16. Code rural et de la pêche maritime, article L214-6-1
17. DRAAF, ACACED
18. Sénat, réponse ministérielle sur les chiens de traîneaux dans l'espace forestier, 2022