Patterns of strain and activation in the thigh muscles of goats across gaits during level locomotion

2011

Phil. Trans. R. Soc. B

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Over the past 30 years, studies of single muscles have revealed complex patterns of regional variation in muscle architecture, activation, strain and force. In addition, muscles are often functionally integrated with other muscles in parallel or in series. Understanding the extent of this complexity and the interactions between muscles will profoundly influence how we think of muscles in relation to organismal function, and will allow us to address questions regarding the functional benefits (or lack thereof ) and dynamics of this complexity under in vivo conditions. This paper has two main objectives. First, we present a cohesive and integrative review of regional variation in function within muscles, and discuss the functional ramifications that can stem from this variation. This involves splitting regional variation into passive and active components. Second, we assess the functional integration of muscles between different limb segments by presenting new data involving in vivo measurements of activation and strain from the medial gastrocnemius, iliotibialis cranialis and iliotibialis lateralis pars preacetabularis of the helmeted guinea fowl (Numida meleagris) during level running on a motorized treadmill. Future research directions for both of these objectives are presented.

Section: Functional Heterogeneity Within Musclesmentioning

confidence: 99%

Functional and architectural complexity within and between muscles: regional variation and intermuscular force transmission

Higham

2011

Phil. Trans. R. Soc. B

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“…A previous analysis of the net external (ground reaction) moments and work at the knee and ankle has provided some evidence that goats actively modulate joint work with surface grade; in particular, measurements on three goats showed that muscular moments at the knee and ankle contributed more positive work during uphill running and more negative work during downhill running then they did during level running (Lee et al, 2008). In another study on goats, Gillis and colleagues measured patterns of strain and activation in the biceps femoris and vastus lateralis muscles during level locomotion and showed that the amount of fascicle stretching and shortening (and presumably fascicle work) varied depending on locomotor speed (Gillis et al, 2005). Our ongoing research builds upon and extends these previous studies.…”

Section: Introductionmentioning

confidence: 99%

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

Arnold

Lee

Journal of Experimental Biology

2013

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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.

“…Although fascicle strain rate varies with flight speed, the generally uniform contractile properties of the pectoralis across a range of flight speeds [27,29] (figure 3) reflect the strikingly uniform fibretype characteristics of the avian pectoralis [21 -23]. This is in contrast to the much larger change in fascicle shortening velocity with running speed that occurs in the leg muscles of terrestrial animals [51][52][53][54].…”

mentioning

confidence: 99%

Muscle function in avian flight: achieving power and control

2011

Phil. Trans. R. Soc. B

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104

Flapping flight places strenuous requirements on the physiological performance of an animal. Bird flight muscles, particularly at smaller body sizes, generally contract at high frequencies and do substantial work in order to produce the aerodynamic power needed to support the animal's weight in the air and to overcome drag. This is in contrast to terrestrial locomotion, which offers mechanisms for minimizing energy losses associated with body movement combined with elastic energy savings to reduce the skeletal muscles' work requirements. Muscles also produce substantial power during swimming, but this is mainly to overcome body drag rather than to support the animal's weight. Here, I review the function and architecture of key flight muscles related to how these muscles contribute to producing the power required for flapping flight, how the muscles are recruited to control wing motion and how they are used in manoeuvring. An emergent property of the primary flight muscles, consistent with their need to produce considerable work by moving the wings through large excursions during each wing stroke, is that the pectoralis and supracoracoideus muscles shorten over a large fraction of their resting fibre length (33-42%). Both muscles are activated while being lengthened or undergoing nearly isometric force development, enhancing the work they perform during subsequent shortening. Two smaller muscles, the triceps and biceps, operate over a smaller range of contractile strains (12-23%), reflecting their role in controlling wing shape through elbow flexion and extension. Remarkably, pigeons adjust their wing stroke plane mainly via changes in whole-body pitch during take-off and landing, relative to level flight, allowing their wing muscles to operate with little change in activation timing, strain magnitude and pattern.