The telemetered electromyographic activity (EMG) of select hindlimb muscles of unrestrained cats during standing, walking, trotting, and galloping have been recorded. Simultaneous cinematographic records permitted close correlation of muscle activity and locomotor behavior. In general, the pattern of extensor activity of the ankle, knee, and hip during locomotion is fairly consistent, while that of the flexors is more variable.



Changes in basic EMG patterns from walk, to trot, to gallop are most evident in the two-jointed muscles associated with the knee and hip. Progressively greater variation of activity onset and cessation can be seen among extensor muscle groups from the walk, to trot, to gallop. Co-activation of the joint extensors and flexors, especially of the hip, at the end of the stance phase (E3) is slight in the walk, moderate in the trot, and considerable in the gallop. These EMG changes are necessary to meet the demands imposed upon the musculature at the faster gaits, particularly galloping, which include limb rigidity as related to loading, momentum as related to the limb's directional change from the stance phase to the swing phase, and lower spinal movements.



The peroneal muscles of the ankle and the gluteal muscles of the hip show extensor activity and act as joint stabilizers during locomotion. Both biceps femoris anterior muscle and biceps femoris posterior muscle show consistent hip extensor patterns at all gaits. During quiet standing, extensor activity about the knee, ankle, and metatarsophalangeal joints is evident; but the hip extensor and flexor musculature is remarkably silent.



EMG data for unrestrained cats are compared to those of dogs on a treadmill (Tokuriki, '73a,b, '74; Wentink, '76) and those recorded from decerebrate cats (mesencephalic preparation) during controlled locomotion (Gambaryan et al., '71). The EMG patterns from decerebrate cats are more consistent at the walk and gallop within functional groups of muscles at the ankle, knee, and hip than the EMG patterns observed in unrestrained cats or animals moving on a treadmill.

The cat step cycle: Electromyographic patterns for hindlimb muscles during posture and unrestrained locomotion

In domestic pigeons (Columba livia), the electrical activity of the major depressor muscle of the wing, the pectoralis (pars thoracicus), beings in late upstroke well before the wing begins its downstroke excursion. The two architecturally distinct heads of the pectoralis, the sternobrachialis and the thoracobrachialis, are differentially recruited during take-off, level flight and landing. In addition to wing depression, the sternobrachialis protracts the humerus and the thoracobrachialis retracts the humerus. At the point of transition from wing upstroke to downstroke, the pectoralis EMG signal typically exhibits a reduction in amplitude. The supracoracoideus, in addition to an expected EMG associated with wing elevation, is co-activated with the pectoralis about 50% of the time.

A functional analysis of the primary upstroke and downstroke muscles in the domestic pigeon (Columba livia) during flight.

To examine the functional roles played by the lumbar spine during overground stepping, seven adult cats were run in electromyographic (EMG) experiments. Recordings were made bilaterally from mm. iliocostalis, longissimus dorsi and multifidus at a single vertebral level (L3 ) and from m. rectus abdominis. Stepping movements were monitored synchronously either by videotape or by high speed cinematography. During alternate use of the hindlimbs (walking and trotting), both epaxial and abdominal muscles were active bilaterally and biphasically. During in-phase use of the hindlimbs (galloping and half-bounding), single bursts of activity were observed. Phasic bursts of activity in rectus abdominus were reciprocal to those of epaxial muscles. Second bursts of activity in either group were noted infrequently. Recordings from the same back muscle at several vertebral levels indicated little difference from these patterns. Movements of the lumbar spine during galloping and half-bounding steps, both angular and linear, are easily correlated with muscle activity patterns. Movements of the lumbar spine during walking and trotting show no particular pattern. Only small angular and linear movements are found. It is concluded that the lumbar spine contributes substantially to step length and limb speed during galloping and half-bounding steps and the epaxial and abdominal musculature may also act as elastic bodies. During walking and trotting steps, the epaxial muscles are proposed to act to stabilize the pelvic girdle to provide a firm base for limb muscles which arise on the pelvis and are synchronously active.

The functions of the lumbar spine during stepping in the cat.

Bipedality not only frees the hands for tool use but also enhances tool use by allowing use of the trunk for leverage in applying force and thus imparting greater final velocity to tools. Since the weight and acceleration of the trunk and forelimbs on the hindlimbs must be counteracted by muscles such as m. gluteus maximus that control pelvic and trunk movements, it is suggested that the large size of the cranial portion of the human gluteus maximus muscle and its unique attachment to the dorsal ilium (which is apparent in the Makapan australopithecine ilium) may have contributed to the effectiveness with which trunk movement was exploited in early hominid foraging activities. To test this hypothesis, the cranial portions of both right and left muscles were investigated in six human subjects with electromyography during throwing, clubbing, digging, and lifting. The muscles were found to be significantly recruited when the trunk is used in throwing and clubbing, initiating rotation of the pelvis and braking it as trunk rotation ceases and the forelimb accelerates. They stabilize the pelvis during digging and exhibit marked and prolonged activity when the trunk is maintained in partial flexion during lifting of heavy objects.

Gluteus maximus muscle function and the origin of hominid bipedality.

When exploring biological determinants of spontaneous physical activity (SPA), it is critical to consider whether methodological factors differentially affect rodents and the measured SPA. We determined whether acclimation time, sensory stimulation, vendor, or chamber size affected measures in rodents with varying propensity for SPA. We used principal component analysis to determine which SPA components (ambulatory and vertical counts, time in SPA, and distance traveled) best described the variability in SPA measurements. We compared radiotelemetry and infrared photobeams used to measure SPA and exploratory activity. Acclimation time, sensory stimulation, vendor, and chamber size independently influenced SPA, and the effect was moderated by the propensity for SPA. A 24-h acclimation period prior to SPA measurement was sufficient for habituation. Principal component analysis showed that ambulatory and vertical measurements of SPA describe different dimensions of the rodent's SPA behavior. Smaller testing chambers and a sensory attenuation cubicle around the chamber reduced SPA. SPA varies between rodents purchased from different vendors. Radiotelemetry and infrared photobeams differ in their sensitivity to detect phenotypic differences in SPA and exploratory activity. These data highlight methodological considerations in rodent SPA measurement and a need to standardize SPA methodology.

https://www.physiology.org/doi/pdf/10.1152/ajpregu.00479.2013

Methodological considerations for measuring spontaneous physical activity in rodents

Two recurring problems hampering investigations of muscular activity patterns during locomotion are electrical “noise” and movement artifact in the electromyographic (EMG) signal and proper synchronization of behavioral events to the EMG. A relatively simple technique for achieving these ends is presented. Vigorous locomotor movements of unrestrained animals are recorded on 16-mm film and synchronized with one or more EMGs from selected muscles with little electrical noise or movement artifact interference. The system employs telemetry which is compared to hardwire techniques.

/pdf/a-simple-technique-for-correlating-film-and-emg-in-382v13pz3v.pdf

G. E. Goslow

Papers

A simple technique for correlating film and EMG in locomotion studies