The cat step cycle: Hind limb joint angles and muscle lengths during unrestrained locomotion

Abstract

A cinematographic analysis of the unrestrained walking, trotting, galloping, jumping and landing movements of 11 adult cats was undertaken to provide previously unavailable information concerning the demands imposed on the nervous system for the control of low and high speed movements and the demands imposed by such natural movements on muscle performance and proprioceptive response.With due regard for the swing (F and El) and stance (E2 and E3) phases of the step cycle of an individual limb, single frame analysis of the film permitted measurement of instantaneous angles of the lower spine, hip, knee, ankle and metatarsophalangeal joints. Appropriate lever arm measurements were also made on 50 freshly dispatched cats and 25 cadavers such that the Law of Cosines could be used to calculate instantaneous lengths of select hind limb muscles that would apply to the natural movements of adult cats of small (1.5-2.5 Kg), intermediate (2.6-3.5 Kg) and large (3.6-4.5 Kg) size. Muscle displacements were analyzed relative to maximum and minimum i n situ lengths and the lengths associated with quiet standing. Use was also made of a previous electromyographic analysis of hind limb muscles during unrestrained locomotion (Engberg and Lundberg, '69).The sequential relations between the four phases of the step cycle are maintained as forward speed increases from walking (< 2 mph) to high speed galloping (> 16 mph). There are significant differences in the time consumed by each phase, however, with a greater reduction in the ES phase, little reduction in the E2 and E' phases and virtually no reduction in the F phase. When each phase is expressed as a relative percentage of the duration of the total step cycle, the greatest reduction is again in E3 with little change in the E2 phase. In contrast F and E' phases increase in the percent of time they occur in each cycle, with the greatest increase in the F phase. For all speeds, analysis of the phase relations between movements of various sections of the hind limb revealed a remarkable unity of knee and ankle joint movement. The hip joint is largely out of phase with the knee and ankle during E1 and E2, all three joints being in phase in F and E3. The digits are essentially out of phase with the other joints except in the stance phase of the gallop. Rates and extents of muscle displacement during natural movements are greater than might be anticipated when expressed in absolute mm's and mm/sec but not when considered in relation to maximum and minimum in situ length and the length associated with quiet standing (Ls). During stepping a progressive increase in forward speed results in: ( a ) a greater usage of muscles at lengths between Ls and maximum in situ length; ( b ) for knee and ankle extensors, pronounced increase in the lengthening contraction associated with the E2 (yield) phase of the step; and, ( c ) for both flexor and extensor muscles, an increased active phase of lengthening or near isometric contraction immediately prior to periods of active shortening. In contra...

Evidence for Specialized Rhythm-Generating Mechanisms in the Adult Mammalian Spinal Cord

“…During fictive locomotion occurring spontaneously, or in cats with a spinal transection, cycle period varied more with extension phase duration (i.e., extensor-dominated) (Frigon and Gossard, 2009); which closely resembles intact walking where cycle period varies with stance duration (Goslow et al, 1973;Grillner et al, 1979;Halbertsma, 1983;Grillner and Dubuc, 1988). Conversely, cycle period during fictive scratch varied with flexion phase duration (Figs.…”

“…During normal walking, cycle period is regulated by changing the duration of the extension phase (i.e., stance), while the flexion phase (i.e., swing) remains relatively invariant (Goslow et al, 1973;Grillner et al, 1979;Halbertsma, 1983). The same pattern is typically found during fictive locomotion in cats (Frigon and Gossard, 2009), except with electrical stimulation of the mesencephalic locomotor region (MLR) (Yakovenko et al, 2005).…”

Regulation by exercise of the pool of G4 acetylcholinesterase characterizing fast muscles: opposite effect of running training in antagonist muscles

“…and EMG studies (Goslow et al, 1973;Grillncr, 1975;Rasmussen et al, 1978). The less extensive analyses performed in the rat indicate that biomechanics of locomotion is basically the same in both quadrupeds (Gruner et al, 1980;Gardiner et al.…”

“…Activation of the ankle extensors CAST and PL begins when the hindlimb is extended toward the ground and continues and Gisiger -Opposite G, AChE Changes i n Trained Antagonist Fast Muscles throughout the phase during which the limb pushes the animal forward. The contraction of GAST and PL during this "stance phase" (Goslow et al, 1973) generates a significant part of the propulsive force. The ankle flexors, in turn, are activated throughout the "swing phase" (Goslow et al, 1973) during which the hindlimb is recovered and protracted forward, leading into the next stride.…”

“…The contraction of GAST and PL during this "stance phase" (Goslow et al, 1973) generates a significant part of the propulsive force. The ankle flexors, in turn, are activated throughout the "swing phase" (Goslow et al, 1973) during which the hindlimb is recovered and protracted forward, leading into the next stride. The biomechanical action of the ankle flexors is more complex than that of the extensors.…”