Why Don’t Sled Dogs Ever Get Tired?

Why Don’t Sled Dogs Ever Get Tired?

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Sled dogs are the best endurance athletes in the world thanks to a weird quirk in their metabolism.

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To learn more about this topic, start your googling with these keywords:

Glycolysis: The process by which glycogen is broken down into energy.
Anaerobic metabolism: The creation of energy through the combustion of carbohydrates in the absence of oxygen.
Aerobic metabolism: The creation of energy through the breakdown of fats, proteins, and carbohydrates.
ATP: The principal molecule for storing and transferring energy in cells.
Baseline Vital Signs: A subject’s temperature, pulse, respiration, blood pressure, pain, and pulse oximetry.

Credits (and Twitter handles):
Script Writer: David Goldenberg (@dgoldenberg)
Script Editor: Emily Elert (@eelert)
Video Illustrator: Ever Salazar (@eversalazar)
Video Director: Kate Yoshida (@KateYoshida)
Video Narrator: Kate Yoshida (@KateYoshida)
With Contributions From: Henry Reich, Alex Reich, Peter Reich
Music by: Nathaniel Schroeder:


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McDougall, C. (2011). Born To Run.

McKenzie, M., Holbrook, T., Williamson, T., Royer, C., Valberg, S. ,Hinchcliff, K., Jose-Cunilleras, J., Nelson, S., Willard, M., and Davis, M. (2005). Recovery of Muscle Glycogen Concentrations in Sled Dogs during Prolonged Exercise. Medicine and Science in Sports and Exercise. 37(8). 1307-1312. Retrieved from:

Poole, D. and Erickson, H. (2011). Highly Athletic Terrestrial Mammals: Horses and Dogs. Comprehensive Physiology. 6:57. 1-37. Retrieved from:

Gerth, N., Redman, P., Speakman, J., Jackson, S., and Stark, J.M. (2010). Energy metabolism of Inuit sled dogs. Journal of Comparative Physiology. 180: 577-589. Retrieved from:

Miller, B., Drake, J., Peelor, F.,, Biela, L., Geor, R., Hinchcliff, K., Davis, M., Hamilton, K. (2015). Participation in a 1000-mile race increases the oxidation of carbohydrate in Alaskan sled dogs. Journal of Applied Physiology. 118(12):1502-1509. Retrieved from:

McKenzie, Ericka. (2017). Professor of large animal internal medicine at the Oregon State University College of Veterinary Medicine. Personal Communication.

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