In vivo moment arm lengths for hip extensor muscles at different angles of hip flexion

Moment arm lengths of three hip extensor muscles, the gluteus maximus, the hamstrings and the adductor magnus, were determined at hip flexion angles from 0 degrees to 90 degrees by combining data from ten autopsy specimens and from twenty patients, the latter examined by computed tomography. A straight-line muscle model for muscle force was used for the hamstrings and adductor magnus, and for the gluteus maximus a two-segment straight-line muscle force model was used. With the joint in its anatomical position the moment arm of the gluteus maximus to the bilateral motion axis averaged 79 mm, for the hamstrings 61 mm and for the adductor magnus 15 mm. The moment arm of gluteus maximus decreased with increasing hip flexion angle. The hamstrings showed an increase in moment arm length up to an average of 35 degrees hip flexion and then a decrease with increasing hip flexion angle. The corresponding figures for the adductor magnus moment arm showed an increase up to 75 degrees and then a decrease. Statistical analysis revealed significant differences in moment arm length between men and women.     

Adductor muscles of the thigh of crab-eating monkeys (Macaca fascicularis)

On the basis of 44 hindlimbs of 14 male and 14 female crab-eating monkeys (Macaca fascicularis), the morphology of the adductor muscles of the thigh was described and some functional indices were calculated. The results obtained from this study agreed generally with those of otherMacaca species reported by various authors. For the classification and nomenclature of the adductors, the criteria proposed byUhlmann (1967, 1968) was well adapted to the crab-eating monkey. The adductors comprise the m. gracilis, m. pectineus, m. adductor longus, pars longa and pars brevis of m. adductor brevis, pars lata and pars minima of m. adductor magnus and m. obturatorius externus. In males, the adductors are generally inserted further down the femur, and the insertions of pars brevis of the m. adductor brevis and pars minima of the m. adductor magnus have longer attachments to the femur than in females. The arrangement of each adductor muscle and of each fasciculus of a thigh muscle may invoke a principle of organization.     

Molar occlusion and jaw mechanics of the Eocene primate Adapis

Wear facets on molars of the Eocene primate Adapis magnus are described. Striations on these wear facets indicate three separate directions of mandibular movement during mastication. One direction corresponds to a first stage of mastication involving orthal retraction of the mandible. The remaining two directions correspond to buccal and lingual phases of a second stage of mastication involving a transverse movement of the mandible. The mechanics of jaw adduction are analysed for both the orthal retraction and transverse stages of mastication. During the orthal retraction stage the greatest component of bite force is provided by the temporalis muscles acting directly against the food with the mandible functioning as a link rather than as a lever. A geometrical argument suggests that during the transverse stage of mastication bite force is provided by the temporalis muscles of both sides, the ipsilateral medial and lateral pterygoid muscles, and the contralateral masseter muscle.     

Comparative assessment of the ischial morphology of Victoriapithecus macinnesi

An almost complete primate ischium was recovered from middle Miocene (ca. 15 ma) deposits of Maboko Island (Kenya) in 1987. The specimen shows numerous similarities to the ischial morphology of extant cercopithecids and is attributed to Victoriapithecus macinnesi (Von Koenigswald, 1969), the early Old World monkey best known from Maboko Island. The Victoriapithecus ischium provides the first evidence of early Old World monkey pelvic girdle anatomy. The ischium is characterized by an obliquely oriented and broadly flaring tuberosity, a relatively small acetabulum with little ventrally directed curvature of its caudal portion, a long ischial body and a flange-like ischial spine positioned caudal to the rim of the acetabulum. In these features, Victoriapithecus most closely resembles the vervet monkey, Cercopithecus aethiops. The fossil specimen indicates that Victoriapithecus possessed ischial callosities, a mobile tail and adaptations for (possibly cursorial) quadrupedalism with an adducted posture of the thigh. The occurrence of ischial callosities in Victoriapithecus extends the documented antiquity of this feature in catarrhines by more than 12 million years and shows that the distinctive “sitting-sleeping” adaptations of Old World monkeys (Washburn, 1957) originated prior to the divergence of Colobinae and Cercopithecinae. Differences of developmental sequence and tissue composition indicate that the ischial pads of cercopithecids, hylobatids, and pongids may have arisen independently, through parallel evolution. Contrary to Strasser and Delson (1987), discontinuity of ischial callosities was probably the primitive condition for male cercopithecids.     

The musculature of the papuan frog Phrynomantis stictogaster (Anura,Microhylidae)

The musculature of Phrynomantis stictogaster, a burrowing Papuan microhylid frog, of the subfamily Asterophryinae, is described and compared with accounts of other frogs. P. stictogaster exhibits unusual characters: dense musculature investing an entirely adherent tongue; exceptionally massive jaw musculature; and hitherto underscribed attachments of some muscles in the manus and pes. The presence of an accessory tendon to the M. glutaeus magnus and the pattern of distal thigh tendons confirm previous diagnosis of the Microhylidae, but the presence of an accessory head to M. adductor magnus is a condition previously not noted in the family. Features of the hyoid, pectoral, and thigh muscles resemble those of members of the subfamilies Dyscophinae, Microhylinae, and Spenophryninae.     

Skull allometry in the marine toad,Bufo marinus

Scaling predictions pioneered by A.V. Hill state that isometric changes in kinematics result from isometric changes in size. These predictions have been difficult to support because few animals display truly isometric growth. An exception to this rule is said to be the toads in the genus Bufo, which can grow over three orders of magnitude. To determine whether skull shape increases isometrically, I used linear measurements and geometric morphometrics to quantify shape variation in a size series of 69 skulls from the marine toad, B. marinus. Toads ranged in body mass from 1.8 gm to a calculated 1,558.9 gm. Of all linear measurements (S/V length, skull width, skull length, levator mass, depressor mass, adductor foramen area), only the area of the adductor foramen increased faster than body mass; the remaining variables increased more slowly. In addition, modeling the lower jaw as a lever‐arm system showed that the lengths of the closing in‐ and out‐levers scaled isometrically with body mass despite the fact that the skull itself is changing allometrically. Geometric morphometrics discerned areas of greatest variability with increasing body mass at the rear of the skull in the area of the squamosal bone and the adductor foramen. This increase in area of the adductor foramen may allow more muscle to move the relatively greater mass of the lower jaw in larger toads, although adductor mass scales with body mass. If B. marinus feeds in a similar manner to other Bufo, these results imply that morphological allometry may still result in kinematic isometry. J. Morphol. 241:115–126, 1999. © 1999 Wiley‐Liss, Inc.     

Cranial morphology and adaptations in Eocene Adapidae. I. Sexual dimorphism in Adapis magnus and Adapis parisiensis

Adapis is one of the best known lemuriform fossil primates. Quantitative analysis of all well-preserved crania of Adapis magnus (n = 8) and Adapis parisiensis (n = 12) together with maxillary and mandibular dentitions preserving canines corroborates Stehlin's hypothesis that Adapis was sexually dimorphic. Males are from 13% to 16% larger than females in cranial length, corresponding to a weight dimorphism estimated at 44% to 56%, and have relatively broader skulls with more prominent sagittal and nuchal crests. Canine dimorphism ranges from 13% to 19%, which is equal to or only slightly greater than that expected as a result of body size dimorphism (i.e., relative canine dimorphism is slight or nonexistent). By comparison with living primates, the observed body size dimorphism in Adapis implies a polygynous breeding system. Cebus apella is a diurnal arboreal living primate with moderate body size dimorphism and slight relative canine dimorphism and one can speculate that Adapis lived in polygynous multimale troops of moderate size like those of C. appella. Adapis extends the geological history of sexual dimorphism and polygyny in primates back to the Eocene. Extant lemuriform primates are generally not dimorphic or polygynous and they clearly do not adequately represent the range of social adaptations present in Eocene primates. The evolutionary lineage from Adapis magnus to Adapis parisiensis exhibits reduction in body size and in relative canine size, and phyletic dwarfing in Adapis is possibly an adaptive response to increasing climatic seasonality and environmental instability in the late Eocene and early Oligocene.     

Fibre types in the locomotory muscles of an antarctic teleost,Notothenia rossii

Summary The metabolic and structural differentiation of locomotory muscles of Notothenia rossii has been investigated. In this species sustained locomotion is achieved by sculling with enlarged pectoral fins (labriform locomotion), whilst the segmental myotomal muscle is reserved for burst activity. Red, white and subepidermal fibres can be distinguished in the trunk by histochemical and ultrastructural criteria. The main pectoral muscle (m. adductor profundus) consists entirely of red fibres. These three main fibres types show differences in histochemical staining profiles, capillarization, myofibril shape and packing, and lipid and mitochondrial content. The fractional volume of mitochondria amounts to 38% for pectoral, 30% for red myotomal and 1.9% for white myotomal fibres. Enzyme activities of red pectoral muscle are consistent with a higher potential for aerobic glucose and fatty acid oxidation than for the red myotomal fibres. Mg²⁺ Ca²⁺ -myofibrillar ATPase activities are similar for red pectoral and myotomal muscles and approximately half of those white fibres. Specialisations of N. rossii muscles associated with labriform swimming and locomotion at Antarctic temperatures are discussed.     

Rotational moment arms of the medial hamstrings and adductors vary with femoral geometry and limb position: implications for the treatment of internally rotated gait

Persons with cerebral palsy frequently walk with a crouched, internally rotated gait. Spastic medial hamstrings or adductors are presumed to contribute to excessive hip internal rotation in some patients; however, the capacity of these muscles to produce internal rotation has not been adequately investigated. The purpose of this study was to determine the hip rotation moment arms of the medial hamstrings and adductors in persons with femoral anteversion deformities who walk with a crouched, internally rotated gait. A musculoskeletal model with a "deformable" femur was developed. This model was used, in conjunction with kinematic data obtained from gait analysis, to calculate the muscle moment arms for combinations of joint angles and anteversion deformities exhibited by 21 subjects with cerebral palsy and excessive hip internal rotation. We found that the semimembranosus, semitendinosus, and gracilis muscles in our model had negligible or external rotation moment arms when the hip was internally rotated or the knee was flexed -- the body positions assumed by the subjects during walking. When the femur was excessively anteverted, the rotational moment arms of the adductor brevis, adductor longus, pectineus, and proximal compartments of the adductor magnus in our model shifted toward external rotation. These results suggest that neither the medial hamstrings nor the adductors are likely to contribute substantially to excessive internal rotation of the hip and that other causes of internal rotation should be considered when planning treatments for these patients.     

Effect of knee joint angle on individual hamstrings morphology quantified using free-hand 3D ultrasonography

Exercise responses and injury rates differ between individual hamstrings and this may be linked with their morphology. The aim of this study was to compare muscle length and tendon dimensions between the individual hamstrings at two knee joint angles using free hand three-dimensional ultrasound (3D US). Muscle-tendon length and distal tendon cross-sectional area (CSA), volume, length and echogenicity of biceps femoris long (BFlh) and short (BFsh) head, semimembranosus (SM) and semitendinosus (ST) of 16 individuals were measured using free-hand 3D US at 0° (full extension) and 45° of knee flexion. ST showed the greatest length than all muscles and BFsh the lowest (p < 0.05). No difference was observed between SM and BFlh length (p > 0.05). Of the four muscles, ST tendon was longer, with less volume and CSA but greater echogenicity than the other tendons. In contrast, SM and BFlh showed shorter tendons and lower echogenicity but a greater volume and CSA than ST (p < 0.05). Muscle and tendon lengthened from 45° to 0° knee flexion angle (p < 0.05) but this change was not statistically different between individual hamstrings (p > 0.05). Freehand 3D US indicated that hamstring muscle length and distal tendon dimensions differ between individual hamstrings. All muscles and tendons lengthened as the knee was extended but this change was similar for all individual hamstrings.     

Architecture of the hind limb muscles of cats: Functional significance

Force, velocity, and displacement properties of a muscle are determined in large part by its architectural design. The relative effect of muscle architecture on these physiological variables was studied by determining muscle weight, fiber length, average sarcomere length, and approximate angle of pinnation for 24 cat hind limb muscles. Muscle lengths ranged from 28.3 to 144 mm, whereas fiber lengths ranged from 8.4 to 105.5 mm. Generally, fiber to muscle length ratios were similar throughout a muscle. Estimated angles of pinnation of muscle fibers varied from 0 to 21° with most having an angle of less than 10°. The cross-sectional area of the knee extensors was similar to the knee flexors (16.43 vs. 16.83 cm²) whereas the cross-sectional area of the ankle extensors was more than six times greater than the ankle flexors (18.59 vs. 2.83 cm²). There was a 6.7-fold difference in the maximal force between muscles, when normalized to a constant weight, that could be attributed to architectural features. Rations of wet weight to predicted maximal tetanic tension for each muscle and group were calculated to compare the relative priority of muscle force versus muscle length-velocity for a given mass of muscle. These ratios varied from 0.4 to 4.84. The ratios suggest that velocity and/or displacement is a priority for the hamstrings, whereas force is a priority for the quadriceps and lower leg muscles. As much as a 12.6-fold difference in maximal velocity between muscles can be attributed to differences in fiber lengths. This can be compared to approximately a 2.5-fold difference in maximal velocity reported to occur as a result of biochemical (intrinsic) differences.     

The retro-articular process, streptostyly and the caecilian jaw closing system

Caecilians have two functionally separate sets of jaw closing muscles. The jaw adductor muscles are parallel fibered muscles positioned close to the jaw joint and their lever mechanics suggests they are well suited to rapidly closing the jaws. A second set of muscles, the hypaxial interhyoideus posterior (IHP), levers the jaws closed by pulling on the retroarticular process (RA) of the lower jaw. Models of the lower jaw point out that the angle and length of the RA has a profound effect on the closure force exerted by the IHP. The caecilian skull is streptostylic – the quadrate-squamosal apparatus (QSA) moves relative to the rest of the skull, a condition that seems at odds with a well-ossified cranium. Modeling the contribution of this streptostylic suspension of the lower jaw shows that rotational freedom of the QSA amplifies the force of the IHP by redirecting force applied along the low axis of the lower jaw. Measurements from several species and life stages of preserved caecilians reveal a large variation in predicted bite force (as a multiple of IHP force) with age and phylogeny.     

Structure and direction of jaw adductor muscles as herbivorous adaptations in <Emphasis Type="Italic">Neotoma mexicana</Emphasis> (Muridae,Rodentia)

The herbivorous adaptations of the jaw adductor muscles in Neotoma mexicana were clarified by a comparative study with an unspecialized relative, Peromyscus maniculatus. In P. maniculatus, the anterior part of the deep masseter arises entirely from the lateral side of an aponeurosis, i.e., superior zygomatic plate aponeurosis, whereas N. mexicana has an additional aponeurosis for this part of the muscle, and the fibers attach on both sides of the superior zygomatic plate aponeurosis. Although the structure of the temporalis muscle is nearly identical in the two genera, a clear aponeurosis of origin occurs only in N. mexicana. These characteristics allow fibrous tissues to be processed with a large occlusal force. The deep masseter, internal pterygoid, and external pterygoid muscles of N. mexicana incline more anterodorsally than those of P. maniculatus. The transverse force component of these muscles relative to whole muscle force is smaller in N. mexicana than in P. maniculatus, with the exception of the internal pterygoid. The anterior part of the temporalis muscle of N. mexicana is specialized to produce occlusal pressure. These findings suggest that in N. mexicana a large anterior force is required to move the heavy mandible, due to the hypsodont molars, against frictional force from food, and that the posterior pull of the temporalis, which adjusts the forward force by the other jaw adductor muscles to a suitable level, need not be large for the mandibular movement.     

Sensorimotor transformation from light reception to phototactic behavior inDrosophila larvae (Diptera: Drosophilidae)

In this paper we examine theDrosophila melanogaster larval response to light. We survey the morphology of the larval visual and motor systems in relation to larval locomotory behavior and phototaxis. In addition, this paper proposes a model of sensorimotor transformation and examines the reversal in taxis occurring at theD. melanogaster larval wnadering stage.     

Anatomy of the feeding apparatus of the lemon shark,Negaprion brevirostris

The anatomy of the feeding apparatus of the lemon shark, Negaprion brevirostris, is investigated by gross dissection, computer axial tomography, and histological staining. The muscles and ligaments of the head associated with feeding are described. The upper and lower jaws are suspended by the hyoid arch, which in turn is braced against the chondrocranium by a complex series of ligaments. In addition, various muscles and the integument contribute to the suspension and stability of the jaws. The dual jaw joint is comprised of lateral and medial quadratomandibular joints that resist lateral movement of the upper and lower jaws on one another. This is important during feeding involving vigorous head shaking. An elastic ethmoplatine ligament that unites the anterior portion of the upper jaw to the neurocranium is involved with upper jaw retraction. The quadratomandibularis muscle is divided into four divisions with a bipinnate fiber arrangement of the two large superficial divisions. This arrangement would permit a relatively greater force per unit volume and reduce muscle bulging of the jaw adductor muscle in the spatially confined cheek region. Regions of relatively diffuse integumental ligaments overlying the adductor mandibulae complex and the levator palatoquadrati muscle, interspersed with localized regions of longer tendonlike attachments between the skin and the underlying muscle, permit greater musculoskeletal movement relative to the skin. The nomenclature of the hypobranchial muscles is discussed. In this shark they are comprised of the unsegmented coracomandibularis and coracohyoideus, and the segmented coracoarcualis. © 1995 Wiley-Liss, Inc.     

The effect of elevated levels of thyroxine on the aerobic capacity of locomotor muscles of the tufted duck,Aythya fuligula

Following extended periods of relative inactivity, or prior to migration, birds are able to increase the aerobic capacity of their locomotory muscles. Thyroid hormones may influence this process. A preliminary study was undertaken to assess the ability of elevated levels of thyroxine to increase the aerobic capacity of the locomotory and cardiac muscles of adult tufted ducks. Administration of thyroxine in the food for 8 weeks had little effect on body mass or on the masses of the pectoralis, semitendinosus and iliofibularis muscles, although there were increases in resting oxygen consumption and in the mass of the cardiac ventricles. The maximum activity of the aerobic enzyme, citrate synthase, was significantly greater in the left ventricle, liver, and iliofibularis muscles (P<0.005) of treated birds. However, while there was clearly no difference in activity in the semimembranosus leg muscle, that of the pectoralis was not quite significant (P=0.078). It is concluded that addition of supra-physiological levels of exogenous thyroxine may induce a differential increase in the maximum activity of citrate synthase in the locomotor muscles of the tufted duck, which is correlated with the fibre type composition of these muscles. These results are consistent with those found in studies on rats, with slow oxidative fibres being the most sensitive, and fast glycolytic fibres the least sensitive, to thyroxine treatment.Abbreviations BM body mass - CS citrate synthase - CYTOX cytochrome c oxidase - FG last glycolytic - FOG fast oxydative glycolytic - VO₂ oxygen consumption - SO slow oxidative - T₄ thyroxine - T₃ triiodothyronine     

EMG activity during positive-pressure treadmill running

Success has been demonstrated in rehabilitation from certain injuries while using positive-pressure treadmills. However, certain injuries progress even with the lighter vertical loads. Our purpose was to investigate changes in muscle activation for various lower limb muscles while running on a positive-pressure treadmill at different amounts of body weight support. We hypothesized that some muscles would show decreases in activation with greater body weight support while others would not.Eleven collegiate distance runners were recruited. EMG amplitude was measured over 12 lower limb muscles. After a short warm-up, subjects ran at 100%, 80%, 60%, and 40% of their body weight for two minutes each. EMG amplitudes were recorded during the final 30 s of each stage.Most muscles demonstrated lower amplitudes as body weight was supported. For the hip adductors during the swing phase and the hamstrings during stance, no significant trend appeared.Positive-pressure treadmills may be useful interventions for certain injuries. However, some injuries, such as hip adductor and hamstring tendonitis or strains may require alternative cross-training to relieve stress on those areas. Runners should be careful in determining how much body weight should be supported for various injuries to return to normal activity in the shortest possible time.     

Cranial muscles of the anurans leiopelma hochstetteri and ascaphus truei and the homologies of the mandibular adductors in lissamphibia and other gnathostomes

The frogs Ascaphus truei and Leiopelma hochstetteri are members of the most basal lineages of extant anurans. Their cranial muscles have not been previously described in full and are investigated here by dissection. Comparison of these taxa is used to review a controversy regarding the homologies of the jaw adductor muscles in Lissamphibia, to place these homologies in a wider gnathostome context, and to define features that may be useful for cladistic analysis of Anura. A new muscle is defined in Ascaphus and is designated m. levator anguli oris. The differences noted between Ascaphus and Leiopelma are in the penetration of the jaw adductor muscles by the mandibular nerve (V³). In the traditional view of this anatomy, the paths of the trigeminal nerve branches define homologous muscles. This scheme results in major differences among frogs, salamanders, and caecilians. The alternative view is that the topology of origins, insertions, and fiber directions are defining features, and the nerves penetrate the muscle mass in a variable way. The results given here support the latter view. A new model is proposed for Lissamphibia, whereby the adductor posterior (levator articularis) is a separate entity, and the rest of the adductor mass is configured around it as a folded sheet. This hypothesis is examined in other gnathostomes, including coelacanth and lungfish, and a possible sequence for the evolution of the jaw muscles is demonstrated. In this system, the main jaw adductor in teleost fish is not considered homologous with that of tetrapods. This hypothesis is consistent with available data on the domain of expression of the homeobox gene engrailed 2, which has previously not been considered indicative of homology. Terminology is discussed, and “adductor mandibulae” is preferred to “levator mandibulae” to align with usage in other gnathostomes. J. Morphol., 2011. © 2011 Wiley‐Liss, Inc.     

Locomotory efficiency in the predation strategies of the British Notonecta (Hempitera,Heteroptera)

Summary Locomotory efficiency and potential has been studied in three species of the waterboatman Notonecta in relation to the predation strategies of these bugs.Morphometric analysis, estimating likely relative drag forces, mechanical advantages of the swimming legs and leg length/body length ratios allowed an estimation of locomotory efficiency of the three bugs on the basis of their structural features.A study of the effect of activity on the respiration rate investigated how the predators locomotory abilities were reflected in their physiology.Finally, the relative locomotory abilities of the three predators were compared behaviourly be examining pursuit and attack success after free swimming prey in simple and complex environments.Differences were found between the three predator species which were consistent for the three experimental methods and these were successfully related to the predation strategies and habitat selection of the bugs.