Sylvester Stallone, the creative genius behind the universally known and beloved boxer Rocky Balboa, was recently honored with the Golden Globe for the best supporting actor in his seventh “Rocky” film Creed. Mr. Stallone may yet again be awarded an Academy Award [Rocky won Best Picture in 1977], in now-realized recognition of his talents as an actor.
In Rocky IV, during the dwindling days of the cold war in the 1980’s, Rocky battles Drago, with superhuman strength and rage, to avenge the death of his one-time-foe Apollo Creed, who had become a friend and mentor to Rocky after their last fight. Rocky travels to Siberia for hard labor training and natural physical challenges to fight against Drago. Rocky pulls a sled, loaded with rocks and his brother-in-law and best friend Paulie, as part of his strength and endurance training (see how Rocky pulls his sled). This inspired our team of scientists and engineers to devise a similar challenge for animals walking and running on the DigiGait Imaging System treadmill.
We now offer a MICE SLED, a kit which enables researchers to have their mice pull a sled loaded with up to 300% of their body weight as they walk and run. The sled readily attaches or detaches from a simple harness that gently adheres to the base of the subject’s tail. You will find that postural and kinematic metrics of gait are significantly affected by pulling a sled. For example, while the stride length of a mouse may not be greatly affected by pulling ~50% of its body weight, the duration of the stance phase is significantly increased.
Gait analysis in humans is routinely applied to aid in the diagnosis and treatment of numerous motor dysfunction conditions, such as muscular dystrophy, Parkinson’s disease, nerve injury, and stroke. DigiGait has revolutionized how animal models of human movement disorders are studied. Gone are paper and ink, whereby an animal might leave a few footprints for manual determination of stride length and stance width. DigiGait provides numerous kinematic and postural metrics to describe strength, mobility, balance, and coordination. Of course, these characteristics are affected by challenges of daily living – inclines and declines, surface properties, and obstacles.
DigiGait now empowers researchers to investigate how changes in the walking environment can affect the gait of animals. For example, analysis of hoof landing and stride parameters in harness trotter horses running on different tracks of a sand beach (from wet to dry) and on an asphalt road, demonstrate that the walking surface properties affect loading and kinematics (1). Sled dogs routinely pull more than 100% of their body weight for extended periods of time, greatly increasing metabolic demands. Research shows that sled dogs fed blueberries while exercising as compared to those provided a control diet while exercising, may be better protected against oxidative damage (2). Dietary energy requirements are highly dependent on the load pulled, terrain and ambient temperature (3). These types of questions in murine models are simply not possible without the DigiGait technology. DigiGait provides researchers to explore how the walking environment – incline, decline, load pulling, and obstacles – affect locomotion, to better translate the preclinical research models to human conditions.
Figure 2 illustrates how pulling a sled loaded with 50% of the animal’s body weight significantly affects paw placement angle [left panel] and propulsion duration [right panel] of the hind limbs of adult B6 mice [n=8; walking speed 20 cm/s, up 12 deg incline].
1. Chateau et al. Biomechanical analysis of hoof landing and stride parameters in harness trotter horses running on different tracks of a sand beach (from wet to dry) and on an asphalt road. Equine Vet J Suppl. 2010; (38):488-95. Take me to the abstract
2. Dunlap et al. Total antioxidant power in sled dogs supplemented with blueberries and the comparison of blood parameters associated with exercise. Comp Biochem Physiol A Mol Integr Physiol. 2006;143(4):429-34. Take me to the article
3. Loftus JP et al. Energy requirements for racing endurance sled dogs. J Nutr Sci. 2014 Sep 30;3:e34. Take me to the article