Joint work and power associated with acceleration and deceleration in tammar wallabies ( Macropus eugenii )

SUMMARYGoats and other quadrupeds must modulate the work output of their muscles to accommodate the changing mechanical demands associated with locomotion in their natural environments. This study examined which hindlimb joint moments goats use to generate and absorb mechanical energy on level and sloped surfaces over a range of locomotor speeds. Ground reaction forces and the three-dimensional locations of joint markers were recorded as goats walked, trotted and galloped over 0, +15 and −15deg sloped surfaces. Net joint moments, powers and work were estimated at the goatsʼ hip, knee, ankle and metatarsophalangeal joints throughout the stance phase via inverse dynamics calculations. Differences in locomotor speed on the level, inclined and declined surfaces were characterized and accounted for by fitting regression equations to the joint moment, power and work data plotted versus non-dimensionalized speed. During level locomotion, the net work generated by moments at each of the hindlimb joints was small (less than 0.1Jkg -1 body mass) and did not vary substantially with gait or locomotor speed. During uphill running, by contrast, mechanical energy was generated at the hip, knee and ankle, and the net work at each of these joints increased dramatically with speed (P<0.05). The greatest increases in positive joint work occurred at the hip and ankle. During downhill running, mechanical energy was decreased in two main ways: goats generated larger knee extension moments in the first half of stance, absorbing energy as the knee flexed, and goats generated smaller ankle extension moments in the second half of stance, delivering less energy. The goatsʼ hip extension moment in mid-stance was also diminished, contributing to the decrease in energy. These analyses offer new insight into quadrupedal locomotion, clarifying how the moments generated by hindlimb muscles modulate mechanical energy at different locomotor speeds and grades, as needed to accommodate the demands of variable terrain.

Section: Discussionsupporting

confidence: 81%

Modulation of joint moments and work in the goat hindlimb with locomotor speed and surface grade

Arnold

Lee

Biewener

2013

“…Inverse dynamic analyses have shown that work done at proximal joints increased during periods of acceleration (McGowan et al, 2005;Roberts and Scales, 2004), when locomoting on an incline (Roberts and Belliveau, 2005), and when jumping (Aerts, 1998;Dutto et al, 2004a;Jacobs et al, 1996). Muscle work from proximal hindlimb muscles also increases in response to greater energy demands trotting up hill in horses , turkeys (Gabaldón et al, 2004), guinea fowl (Daley and Biewener, 2003) and tammar wallabies (Biewener et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

Joint work and power for both the forelimb and hindlimb during trotting in the horse

Dutto

Hoyt

Clayton

et al. 2006

SUMMARY The net work of the limbs during constant speed over level ground should be zero. However, the partitioning of negative and positive work between the fore- and hindlimbs of a quadruped is not likely to be equal because the forelimb produces a net braking force while the hindlimb produces a net propulsive force. It was hypothesized that the forelimb would do net negative work while the hindlimb did net positive work during trotting in the horse. Because vertical and horizontal impulses remain unchanged across speeds it was hypothesized that net work of both limbs would be independent of speed. Additionally because the major mass of limb musculature is located proximally,it was hypothesized that proximal joints would do more work than distal joints. Kinetic and kinematic analysis were combined using inverse dynamics to calculate work and power for each joint of horses trotting at between 2.5 and 5.0 m s–1. Work done by the hindlimb was indeed positive (consistently 0.34 J kg–1 across all speeds), but, contrary to our hypothesis, net work by the forelimb was essentially zero (but also independent of trotting speed). The zero net work of the forelimb may be the consequence of our not being able to account, experimentally, for the negative work done by the extrinsic muscles connecting the scapula and the thorax. The distal three joints of both limbs behaved elastically with a period of energy absorption followed by energy return. Proximal forelimb joints (elbow and shoulder) did no net work, because there was very little movement of the elbow and shoulder during the portion of stance when an extensor moment was greatest. Of the two proximal hindlimb joints, the hip did positive work during the stride,generating energy almost throughout stance. The knee did some work, but like the forelimb proximal joints, had little movement during the middle of stance when the flexion moment was the greatest, probably serving to allow the efficient transmission of energy from the hip musculature to the ground.

“…Hopping macropodids, whilst clearly bouncing, deviate from our assumptions as the stance phase is decidedly asymmetric: leg angle and leg length are much greater at footon than at foot-off (McGowan et al, 2005), and the peak vertical GRF is significantly greater (36%) than that predicted using a sine wave (Kram and Dawson, 1998). In addition, kangaroos use large contact angles.…”

Section: Limitationsmentioning

confidence: 56%

Prediction of kinetics and kinematics of running animals using an analytical approximation to the planar spring-mass system

Robilliard

Wilson

2005

SUMMARY The spring-mass model is often used to describe bouncing gaits. Although at first inspection the mechanical system appears simple, the solution to the motion cannot be derived easily. An analytical solution would provide a fast and intuitive method to determine the kinetic and kinematics of the centre of mass of terrestrial animals during over-ground steady state locomotion. Here,an analytical approximation using sine wave simplifications for the motion is presented. The analytical solution was almost indistinguishable from the numerical solution across initial leg angles of 17.5–30°; percentage differences between the analytical solution and the numerical solution were less than 1% for total mechanical energy, centre of mass position, total limb compression and centre of mass velocity and less than 2% different for resultant limb force and vertical acceleration of the centre of mass. The solution matched the relationship between stance time and speed collected from a trotting racehorse and accurately characterised previously published biological data. This study has shown that a simple analytical solution can predict the kinetics and kinematics of a spring-mass system over the range of biologically relevant sweep angles and horizontal velocities, and could be used to further understanding of limb deployment and gait selection. Using this analytical solution not only the force profile but also the changes in mechanical energy can be calculated from easily observed morphological and kinematic data.