Further Studies on Locomotion of the Cheetah

1. What they did

In 1959 Milton Hildebrand published a study of the running cheetah, based on a film from Walt Disney Productions. Here he corrects that study and adds new observations.

At an animal show in Ocala, Florida, a trained cheetah ran after a paper bag pulled along a 65-yard course, for rewards of meat. The cheetah seemed to treat it as a game, and usually ran at about 33 miles per hour (mph). The author filmed the cheetah with a high-speed camera taking 200 frames per second. Grass on the course was cleared so the feet could be seen on the ground, and chalk lines were laid across the track every 5 yards, so speed could be worked out directly from the film.

He filmed ten runs, two walking sequences and two trotting sequences. He also used a close-up Disney sequence of a walking cheetah from the film “African Lion” to study how the shoulder blade moves.

2. What they found

Corrections to the 1959 paper

• The Disney film had been shot at 64 frames per second, not 48 as the studio had reported. The cheetah’s top speed in that film is therefore about 56 mph, not 42 mph, with a stride lasting 0.28 second (about 3½ strides per second).
• Bending and straightening the spine adds about 15 inches (in.) to the stride twice per stride, not once. At high speed this adds about 6 mph.
• Published claims of much higher speeds for the Florida cheetah are wrong.

Slow gallop (about 33 mph) versus fast gallop (about 56 mph)

• Over nine runs the Florida cheetah ran 27.7 to 37.5 mph, averaging 33.0 mph. A stride took 0.29 to 0.34 second (average 0.31). Five stride lengths ranged from 12 to 16½ feet (ft), averaging 14.3 ft.
• At about 56 mph a stride took about 0.28 second and covered roughly 23 ft. So as the cheetah speeds up, the stride gets much longer but only slightly faster.
• The spine bends less at lower speed: the bent body was 73% of the stretched body length, against 67% in the fast Disney cheetah.
• At the slow gallop the cheetah spends more of each stride on the ground: on average 68% of the stride, against about 54% at the fast gallop.
• The two front feet were on the ground together for 19% of their combined contact time at the slow gallop; at the fast gallop the author had suggested there may be a fleeting moment between them. The hind feet were on the ground together for 39% at 30 to 35 mph, against about 23% at the fast gallop. Below about 15 mph the cheetah often put both hind feet down at nearly the same moment, like the half-bound of domestic cats.
• At the slow gallop either the leading or the trailing foot could stay on the ground longer, which differs from the author’s earlier conclusion.
• At slower speeds the feet follow similar paths but are not lifted as high.

Other motions of legs and feet

• The wrist and ankle bend sharply as the body passes over them (the forearm at about 110° to the front foot, the shank at 85 to 90° to the hind foot). This adds a final push to each step and keeps the shoulders and hips from rising and falling.
• At 30 to 35 mph the cheetah’s legs strike the ground at an angle about 12° more acute than a horse’s: the cheetah reaches further forward.
• Compared with the horse, the cheetah lifts its feet higher, reaches them further forward and back, and keeps them on the ground relatively longer.

Posture, lead changes, stopping and turning

• Body posture varied a great deal: sometimes a low crouch near the bait, sometimes bouncing strongly at shoulders and hips. The cheetah could run while looking back over one shoulder, and sometimes ran slowly sideways.
• The cheetah changed lead about once per run, even on a straight, clear course where each run took only six to eight strides.
• It could stop from at least 20 mph within a single stride: both front feet came down at about the same moment, then both hind feet, all four placed far forward with the toes spread. The sandy soil sprayed widely, and repeated stops dug a trough that had to be filled in from time to time.
• In sharp turns around a tree at the end of the course, the cheetah leaned so far that its body was at only about 29° to the ground (average of four records).
• The author found no link between movements of the tail and steering, although the tail was often raised just before a turn.
• Acceleration from a standing start could not be measured, because this cheetah turned onto the track from one side rather than bursting off the mark.

Walk and trot

• Representative strides (Figure 4): walking at 2.9 mph, about 4 ft 5 in. per stride; trotting at 12.7 mph, about 6 ft 4 in. per stride; galloping at 31.5 mph, about 13 ft 4 in. per stride (left lead); galloping at about 56 mph, about 22 ft 10 in. per stride (right lead). Each gait has eight phases.
• The trot is upright, even and springy, with one or two feet or none on the ground at a time. In the walk two, three or four feet support the body.
• Strides varied considerably from one to the next.

The shoulder blade in walking

• The shoulder blade moves a great deal over the ribcage: one point traces an oval about 2¾ in. long and 1¼ in. high; another traces a crescent about 3½ in. long. It rotates through about 26°.
• This movement lengthens each stride by about 4½ in.
• Because the cheetah’s front foot is short, bending the wrist alone does not shorten the foreleg enough. The shoulder joint is also carried about ¾ in. higher when the leg is under the body, so the chest glides forward without rising over the supporting leg.
• The upper edges of the two shoulder blades rise above the backbone and cross over the midline in turn, which is striking when a walking cheetah is seen from behind.

3. What they concluded

• Stride length and stride rate vary even at a single speed, but as the cheetah speeds up from about 33 to about 56 mph, the stride gets much longer while getting only slightly faster.
• The slow gallop differs from the fast gallop in stride length, use of the spine, how long the feet are on the ground, where the leading feet are placed, and the paths the feet follow.
• Bending the wrist and ankle, and in the foreleg also moving the shoulder blade, lets the cheetah take long strides without its body bouncing up and down.
• The author’s earlier estimate of shoulder blade rotation in the running cheetah was probably too low.
• “The more one studies the gaits of animals the more one is impressed by the range of variation.”

6. Other technologies, skills or innovations

• A high-speed electric motion picture camera taking 200 frames per second at exposures of 1/1000 of a second.
• Chalk lines across the course every 5 yards, so speed could be calculated directly from the film.
• To follow the shoulder blade, a clear plastic cut-out of the bone, made to exact scale, was laid over each projected film frame, and spots on the coat were used as fixed reference points so the drawings could be lined up.