Force–velocity properties of two avian hindlimb muscles

Nelson, Frank E.; Gabaldón, Annette M.; Roberts, Thomas J.

doi:10.1016/j.cbpb.2004.02.004

Cited by 48 publications

(57 citation statements)

References 54 publications

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“…Although the strains during shortening and lengthening are significantly different between the anterior and posterior fascicles, the differences are relatively small and result in small differences in shortening velocity as a fraction of maximum shortening velocity (V max ). Based on the V max found for leg muscles in turkeys (Nelson et al, 2004) and adjusting for body size, the V max of the ILPO is expected to be ~15L 0 s -1 . Given this value, the maximum differences in velocity between the anterior and posterior regions represent only 2-3% of V max .…”

Section: Discussionmentioning

confidence: 99%

Mechanisms producing coordinated function across the breadth of a large biarticular thigh muscle

Carr

Ellerby

Rubenson

et al. 2011

Journal of Experimental Biology

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SUMMARYWe examined the hypothesis that structural features of the iliotibialis lateralis pars postacetabularis (ILPO) in guinea fowl allow this large muscle to maintain equivalent function along its anterior-posterior axis. The ILPO, the largest muscle in the hindlimb of the guinea fowl, is a hip and knee extensor. The fascicles of the ILPO originate across a broad region of the ilium and ischium posterior to the hip. Its long posterior fascicles span the length of the thigh and insert directly on the patellar tendon complex. However, its anterior fascicles are shorter and insert on a narrow aponeurosis that forms a tendinous band along the anterior edge of the muscle and is connected distally to the patellar tendon. The biarticular ILPO is actively lengthened and then actively shortened during stance. The moment arm of the fascicles at the hip increases along the anterior to posterior axis, whereas the moment arm at the knee is constant for all fascicles. Using electromyography and sonomicrometry, we examined the activity and strain of posterior and anterior fascicles of the ILPO. The activation was not significantly different in the anterior and posterior fascicles. Although we found significant differences in active lengthening and shortening strain between the anterior and posterior fascicles, the differences were small. The majority of shortening strain is caused by hip extension and the inverse relationship between hip moment arm and fascicle length along the anterior-posterior axis was found to have a major role in ensuring similar shortening strain. However, because the knee moment arm is the same for all fascicles, knee flexion in early stance was predicted to produce much larger lengthening strains in the short anterior fascicles than our measured values at this location. We propose that active lengthening of the anterior fascicles was lower than predicted because the aponeurotic tendon of insertion of the anterior fascicles was stretched and only a portion of the lengthening had to be accommodated by the active muscle fascicles.

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Section: Discussionmentioning

confidence: 99%

Mechanisms producing coordinated function across the breadth of a large biarticular thigh muscle

Carr

Ellerby

Rubenson

et al. 2011

Journal of Experimental Biology

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“…The protocols used for this muscle preparation are modified from a previous study (29). We independently measured muscle fiber velocity using sonomicrometry and whole-muscle velocity using a servomotor.…”

Section: Methodsmentioning

confidence: 99%

Variable gearing in pennate muscles

Azizi

Brainerd

Roberts

2008

Proc. Natl. Acad. Sci. U.S.A.

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296

406

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Muscle fiber architecture, i.e., the physical arrangement of fibers within a muscle, is an important determinant of a muscle's mechanical function. In pennate muscles, fibers are oriented at an angle to the muscle's line of action and rotate as they shorten, becoming more oblique such that the fraction of force directed along the muscle's line of action decreases throughout a contraction. Fiber rotation decreases a muscle's output force but increases output velocity by allowing the muscle to function at a higher gear ratio (muscle velocity/fiber velocity). The magnitude of fiber rotation, and therefore gear ratio, depends on how the muscle changes shape in the dimensions orthogonal to the muscle's line of action. Here, we show that gear ratio is not fixed for a given muscle but decreases significantly with the force of contraction (P < 0.0001). We find that dynamic muscle-shape changes promote fiber rotation at low forces and resist fiber rotation at high forces. As a result, gearing varies automatically with the load, to favor velocity output during low-load contractions and force output for contractions against high loads. Therefore, muscle-shape changes act as an automatic transmission system allowing a pennate muscle to shift from a high gear during rapid contractions to low gear during forceful contractions. These results suggest that variable gearing in pennate muscles provides a mechanism to modulate muscle performance during mechanically diverse functions.biomechanics ͉ force-velocity tradeoff ͉ gear ratio ͉ muscle architecture T he force, speed, and power that can be harnessed from skeletal muscles to power movement are ultimately limited by the mechanical behavior of myofibers, the muscles' contractile cells. Two features of the contractile behavior of myofibers that likely constrain locomotor performance are the well defined limits to contraction velocity and contractile force. The maximum shortening velocity of a myofiber can be characterized by allowing the muscle to contract against near-zero loads, and a maximum isometric force can be defined when a muscle contracts at a fixed length. To understand how these limits to speed and force at the level of skeletal muscle cells translate to limits to speed or force of movement requires a consideration of musculoskeletal components that modulate force and velocity ''downstream'' of the force-producing cells. The most familiar of these are the skeletal lever systems, which define the mechanical advantage (gearing) through which muscle force is transmitted (1, 2). Like any lever or gear, skeletal gearing influences the ratio of muscle force or velocity to output force or velocity.A less obvious potential gearing mechanism resides within the architecture of the muscles themselves (3). It is generally recognized that skeletal muscle architecture influences the force and velocity of a muscle, but in most cases, the analysis of the effects of muscle architecture on force or velocity output has been limited to predictions based on static anatomy. Dynamic changes...

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“…Triangulated representations of bony surfaces were imported into SIMM (MusculoGraphics, Inc., Santa Rosa, CA). Physiologic cross sectional areas (PCSA) were calculated for each muscle by dividing muscle volume by optimal fiber length (approximated as the fiber length during stance), and used to estimate maximal possible isometric forces by multiplying each muscle's PCSA by 30 N/cm 2 (Nelson et al 2004). These maximal forces, muscle pennation angles, optimal fiber lengths, tendon slack lengths (measured tendon length at rest in situ), and three-dimensional muscle coordinates relative to the bones were also input to SIMM.…”

Section: Methodsmentioning

confidence: 99%

“…Sagittal plane moment arms were exported for the knee, hock, and subtalar joints. Values of MDMF were determined using the standard SIMM length-tension and force-velocity curves with the maximal velocity set to 15 muscle lengths/sec, based on values measured for turkeys (Hill 1925;Nelson et al 2004). …”

Section: Methodsmentioning

confidence: 99%

Hip joint contact force in the emu (Dromaius novaehollandiae) during normal level walking

Goetz

Derrick

Pedersen

et al. 2008

Journal of Biomechanics

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The emu is a large, (bipedal) flightless bird that potentially can be used to study various orthopaedic disorders in which load protection of the experimental limb is a limitation of quadrupedal models. An anatomy-based analysis of normal emu walking gait was undertaken to determine hip contact forces for comparison with human data. Kinematic and kinetic data captured for two laboratoryhabituated emus were used to drive the model. Muscle attachment data were obtained by dissection, and bony geometries were obtained by CT scan. Inverse dynamics calculations at all major lowerlimb joints were used in conjunction with optimization of muscle forces to determine hip contact forces. Like human walking gait, emu ground reaction forces showed a bimodal distribution over the course of the stance phase. Two-bird averaged maximum hip contact force was approximately 5.5 times body weight, directed nominally axially along the femur. This value is only modestly larger than optimization-based hip contact forces reported in literature for humans. The interspecies similarity in hip contact forces makes the emu a biomechanically attractive animal in which to model loading-dependent human orthopaedic hip disorders.

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Force–velocity properties of two avian hindlimb muscles

Cited by 48 publications

References 54 publications

Mechanisms producing coordinated function across the breadth of a large biarticular thigh muscle

Mechanisms producing coordinated function across the breadth of a large biarticular thigh muscle

Variable gearing in pennate muscles

Hip joint contact force in the emu (Dromaius novaehollandiae) during normal level walking

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