Humeral retractor EMG during quadrupedal walking in primates

SUMMARY) on a motorized treadmill. Locomotor forces were modified by (1) adding mass to the trunk, (2) inclining the treadmill so that the dogs ran up-and downhill (3) adding mass to the wrists or (4) applying horizontally directed force to the trunk through a leash. When the dogs trotted at constant speed on a level treadmill, the primary protractor muscles of the forelimb exhibited activity during the last part of the ipsilateral support phase and the beginning of swing phase, a pattern that is consistent with the initiation of swing phase but not with active protraction of the limb during the beginning of support phase. Results of the force manipulations were also consistent with the protractor muscles initiating swing phase and contributing to active braking via production of a protractor moment on the forelimb when the dogs decelerate. A similar situation appears to be true for the major retractor muscles of the forelimb. The m. pectoralis profundus and the m. latissimus dorsi were completely silent during the support phase of the ipsilateral limb when the dogs ran unencumbered and exhibited little or no increase in activity when the dogs carried added mass on their backs to increase any retraction torque during the support phase of constant-speed running. The most likely explanation for these observations is that the ground force reaction vector is oriented very close to the fulcrum of the forelimb such that the forelimb functions as a compliant strut at the shoulder when dogs trot at constant speed on level surfaces. Because the moments at the fulcrum of the pectoral girdle appear to be small during the support phase of a trotting step, a case can be made that it is the activity of the extrinsic appendicular muscles that produce the swing phase of the forelimb that explain the coupled phase relationship between ventilatory airflow and the locomotor cycle in trotting dogs.

Section: Pectoralis Profundus and Latissimus Dorsi Musclescontrasting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Locomotor function of forelimb protractor and retractor muscles of dogs:evidence of strut-like behavior at the shoulder

Carrier

Deban

Fischbein

2008

“…Cartmill et al, 2002;Demes et al, 1994;Hanna et al, 2006;Kimura et al, 1979;Larson and Stern, 2008;Patel, 2009;Reynolds, 1985;Schmitt et al, 2006;Vilensky, 1983; see also Schmitt, 2003). This research has provided numerous insights into primate evolution.…”

Section: Introductionmentioning

confidence: 99%

The gaits of primates: center of mass mechanics in walking, cantering and galloping ring-tailed lemurs,Lemur catta

O’Neill

Schmitt

2012

SUMMARY Most primates, including lemurs, have a broad range of locomotor capabilities, yet much of the time, they walk at slow speeds and amble, canter or gallop at intermediate and fast speeds. Although numerous studies have investigated limb function during primate quadrupedalism, how the center of mass (COM) moves is not well understood. Here, we examined COM energy, work and power during walking, cantering and galloping in ring-tailed lemurs, Lemur catta (N=5), over a broad speed range (0.43–2.91 m s–1). COM energy recoveries were substantial during walking (35–71%) but lower during canters and gallops (10–51%). COM work, power and collisional losses increased with speed. The positive COM works were 0.625 J kg–1 m–1 for walks and 1.661 J kg–1 m–1 for canters and gallops, which are in the middle range of published values for terrestrial animals. Although some discontinuities in COM mechanics were evident between walking and cantering, there was no apparent analog to the trot–gallop transition across the intermediate and fast speed range (dimensionless v>0.75, Fr>0.5). A phenomenological model of a lemur cantering and trotting at the same speed shows that canters ensure continuous contact of the body with the substrate while reducing peak vertical COM forces, COM stiffness and COM collisions. We suggest that cantering, rather than trotting, at intermediate speeds may be tied to the arboreal origins of the Order Primates. These data allow us to better understand the mechanics of primate gaits and shed new light on primate locomotor evolution.

“…After the back-stimulation experiments, the free ends of the electrode wires were connected to a 112g, 4-channel, Bio-Sentry Telemetry FM telemetry transmitter, which was then attached to a non-restrictive harness and shirt worn by the subjects (e.g. Larson and Stern, 2007).…”

Section: Methodsmentioning

confidence: 99%

“…Boyer et al, 2007;Larson and Stern, 2007;Larson and Stern, 2009;Kingston et al, 2010). Briefly, using a Panasonic 5100HS color video camera with an electronic high-speed shutter, analog video of the subject's behavior was recorded at 60Hz on Fuji SVHS ST-120 videotapes using a Panasonic AG-5210 VCR.…”

Section: Methodsmentioning

confidence: 99%

Electromyography of wrist and finger flexor muscles in olive baboons (Papio anubis)

Patel

Larson

Stern

2012

Self Cite

SUMMARYSome non-human primates use digitigrade hand postures when walking slowly on the ground. As a component of an extended limb, a digitigrade posture can help minimize wrist joint moments thereby requiring little force production directly from wrist flexors (and/or from the assistance of finger flexors) to maintain limb posture. As a consequence, less active muscle volume would be required from these anti-gravity muscles and overall metabolic costs associated with locomotion could be reduced. To investigate whether the use of digitigrade hand postures during walking in primates entails minimal use of anti-gravity muscles, this study examined electromyography (EMG) patterns in both the wrist and finger flexor muscles in facultatively digitigrade olive baboons (Papio anubis) across a range of speeds. The results demonstrate that baboons can adopt a digitigrade hand posture when standing and moving at slow speeds without requiring substantial EMG activity from distal anti-gravity muscles. Higher speed locomotion, however, entails increasing EMG activity and is accompanied by a dynamic shift to a more palmigrade-like limb posture. Thus, the ability to adopt a digitigrade hand posture by monkeys is an adaptation for ground living, but it was never coopted for fast locomotion. Rather, digitigrady in primates appears to be related to energetic efficiency for walking long distances.