Part 1 of this article outlined the extensive osseous adaptations around the hip that occurred in the development of a habitual bipedal gait in modern humans. The shortest summary of these osseous ...changes is 'double extension', i.e. extension of both the hip joint and the lumbar spine. Not surprisingly, these osseous changes went hand in hand with major muscular changes. The primary changes that accompanied the double extension were changes in relative muscle volume for the quadriceps, gluteus maximus and hamstrings, changes in moment arms for the iliopsoas, gluteus maximus and hamstrings, a change in function for the gluteus medius and minimus, while the functional anatomy of the adductors and hip rotators changed only slightly. The effect of these osseous and muscular changes was improved energy efficiency of human bipedal walking and (long distance) running. However, this occurred at the expense of maximum power, characteristic for activities such as tree climbing (in the apes), but equally so for sprinting. Recognizing these changes and their consequences may help us better understand and treat soft-tissue disorders around the hip.
This study gives a qualitative and quantitative description of the different terrestrial locomotor modes of a group of white-handed gibbons (
Hylobates lar) from the Wild Animal Park Planckendael, ...Belgium. The gibbons were filmed during voluntary locomotion on a grassy and smooth substrate and on a pole. These video images allowed us to define seven different gait types, based on spatial and temporal footfall patterns. Consequent digitization of the video images (
n
=
254) yielded duty factors, stride lengths, and stride frequencies of the fore- and hind limbs during locomotion at a wide range of speeds. These spatiotemporal gait characteristics were regressed against velocity, and the regression lines of the different gait types were compared. In addition, gibbon bipedalism was compared with bonobo (
Pan paniscus) and human bipedalism. Gibbons appear to be very versatile animals, using a bipedal, tripedal, or quadrupedal gait during terrestrial travel with an overlapping speed range. The spatiotemporal characteristics of these gaits are largely similar, although they have clearly distinct footfall patterns. Bipedal walking on the pole is slightly different from terrestrial bipedalism, but differences between substrate types (grass vs. catwalk) are subtle. During bipedalism, gibbons increase both stride length and frequency to increase speed, just as humans and bonobos do, but at a given speed, gibbons take relatively larger strides at lower rates. Bipedal walking in gibbons also appears to be relatively fast—gibbons could keep on walking at speeds where humans have to start running. Apparently, adaptations for arboreal locomotion have not constrained the terrestrial locomotor abilities of gibbons. This may indicate that the step from an arboreal ancestral ape to a terrestrial, upright bipedal hominin might not be difficult and that structural specializations are not a prerequisite for adopting a (non-habitual) bipedal gait.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The storage and recovery of elastic strain energy in the musculoskeletal systems of locomoting animals has been extensively studied, yet the external environment represents a second potentially ...useful energy store that has often been neglected. Recent studies have highlighted the ability of orangutans to usefully recover energy from swaying trees to minimise the cost of gap crossing. Although mechanically similar mechanisms have been hypothesised for wild leaping primates, to date no such energy recovery mechanisms have been demonstrated biomechanically in leapers. We used a setup consisting of a forceplate and two high-speed video cameras to conduct a biomechanical analysis of captive gibbons leaping from stiff and compliant poles. We found that the gibbons minimised pole deflection by using different leaping strategies. Two leap types were used: slower orthograde leaps and more rapid pronograde leaps. The slower leaps used a wider hip joint excursion to negate the downward movement of the pole, using more impulse to power the leap, but with no increase in work done on the centre of mass. Greater hip excursion also minimised the effective leap distance during orthograde leaps. The more rapid leaps conversely applied peak force earlier in stance where the pole was effectively stiffer, minimising deflection and potential energy loss. Neither leap type appeared to usefully recover energy from the pole to increase leap performance, but the gibbons demonstrated an ability to best adapt their leap biomechanics to counter the negative effects of the compliant pole.
When gibbons travel through the forest canopy, brachiation is alternated with short bipedal bouts over horizontal boughs. We know, from previous research, that brachiation is a very efficient ...locomotor mode that makes use of a pendulum-like exchange of energy, but to date, nothing is known about the dynamics of hylobatid bipedalism. We wondered if gibbons also make use of an efficient gait mechanism during bipedal locomotion. To investigate this, we calculated oscillations of the centre of mass (COM), energy fluctuations, recovery rates and power outputs from the 3D ground reaction forces. These ground reaction forces were collected during spontaneous bipedal locomotion of four untrained white-handed gibbons (Hylobates lar) over an instrumented walkway (with an AMTI force plate). Excursions of the COM are relatively large during hylobatid bipedalism and the fluctuations of potential and kinetic energy are largely in-phase. Together with the low inverted pendulum recovery rates, this points to a spring-mass mechanism during bipedal locomotion. Although the well-developed Achilles tendon of gibbons seems to be a good candidate for the storage and recoil of elastic energy, this is not supported by kinematical data of the ankle joint. Instead, we suggest that the knee extensor muscle tendon unit functions as an energy-saving mechanism during hylobatid bipedalism, but detailed anatomical data is needed to confirm this suggestion. At low speeds gibbons use either pendular or spring mechanics, but a clear gait transition as seen in most quadrupedal mammals is absent. At moderate to high velocities, gibbons use a bouncing gait, generally without aerial phases. This supports the view that aerial phases are not a prerequisite for spring-mass mechanics and reinforces the claim that duty factor alone should not be used to distinguish between a walk and run.
The distance that animals leap depends on their take-off angle and velocity. The velocity is generated solely by mechanical work during the push-off phase of standing-start leaps. Gibbons are capable ...of exceptional leaping performance, crossing gaps in the forest canopy exceeding 10 m, yet possess none of the adaptations possessed by specialist leapers synonymous with maximizing mechanical work. To understand this impressive performance, we recorded leaps of the gibbons exceeding 3.7 m. Gibbons perform more mass-specific work (35.4 J kg−1) than reported for any other species to date, accelerating to 8.3 ms−1 in a single movement and redefining our estimates of work performance by animals. This energy (enough for a 3.5 m vertical leap) is 60 per cent higher than that achieved by galagos, which are renowned for their remarkable leaping performance. The gibbons' unusual morphology facilitates a division of labour among the hind limbs, forelimbs and trunk, resulting in modest power requirements compared with more specialized leapers.
Muscles facilitate skeletal movement via the production of a torque or moment about a joint. The magnitude of the moment produced depends on both the force of muscular contraction and the size of the ...moment arm used to rotate the joint. Hence, larger muscle moment arms generate larger joint torques and forces at the point of application. The moment arms of a number of gibbon hind limb muscles were measured on four cadaveric specimens (one Hylobates lar, one H. moloch and two H. syndactylus). The tendon travel technique was used, utilizing an electro‐goniometer and a linear voltage displacement transducer. The data were analysed using a technique based on a differentiated cubic spline and normalized to remove the effect of body size. The data demonstrated a functional differentiation between voluminous muscles with short fascicles having small muscle moment arms and muscles with longer fascicles and comparatively smaller physiological cross‐sectional area having longer muscle moment arms. The functional implications of these particular configurations were simulated using a simple geometric fascicle strain model that predicts that the rectus femoris and gastrocnemius muscles are more likely to act primarily at their distal joints (knee and ankle, respectively) because they have short fascicles. The data also show that the main hip and knee extensors maintain a very small moment arm throughout the range of joint angles seen in the locomotion of gibbons, which (coupled to voluminous, short‐fascicled muscles) might help facilitate rapid joint rotation during powerful movements.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Extensive osseous adaptations of the lumbar spine, pelvis, hip and femur characterize the emergence of the human bipedal gait with its 'double extension' of the lumbar spine and hip. To accommodate ...lumbar lordosis, the pelvis was 'compacted', becoming wider and shorter, as compared with the non-human apes. The hip joint acquired a much more extended position, which can be seen in a broader evolutionary context of verticalization of limbs. When loaded in a predominantly vertical position, the femur can be built lighter and longer than when it is loaded more horizontally because bending moments are smaller. Extension of the hip joint together with elongation of the femur increases effective leg length, and hence stride length, which improves energy efficiency. At the hip joint itself, the shift of the hip's default working range to a more extended position influences concavity at the head-neck junction and femoral neck anteversion.
Gibbons utilize a number of locomotor modes in the wild, including bipedalism, leaping and, most of all, brachiation. Each locomotor mode puts specific constraints on the morphology of the animal; in ...some cases these may be complementary, whereas in others they may conflict. Despite several studies of the locomotor biomechanics of gibbons, very little is known about the musculoskeletal architecture of the limbs. In this study, we present quantitative anatomical data of the hind limb for four species of gibbon (Hylobates lar, H. moloch, H. pileatus and Symphalangus syndactylus). Muscle mass and fascicle lengths were obtained from all of the major hind limb muscles and the physiological cross‐sectional area was calculated and scaled to remove the effect of body size. The results clearly indicate that, for all of the species studied, the major hip, knee and ankle extensors are short‐fascicled and pennate. The major hip and knee flexors, however, are long‐fascicled, parallel muscles with relatively small physiological cross‐sectional areas. We hypothesize that the short‐fascicled muscles could be coupled with a power‐amplifying mechanism and are predominantly useful in leaping. The long‐fascicled knee and hip flexors are adapted for a wide range of joint postures and can play a role in flexing the legs during brachiation.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
This study investigates the foot and ankle myology of gibbons and bonobos, and compares it with the human foot. Gibbons and bonobos are both highly arboreal species, yet they have a different ...locomotor behaviour. Gibbon locomotion is almost exclusively arboreal and is characterized by speed and mobility, whereas bonobo locomotion entails some terrestrial knuckle‐walking and both mobility and stability are important. We examine if these differences in locomotion are reflected in their foot myology. Therefore, we have executed detailed dissections of the lower hind limb of two bonobo and three gibbon cadavers. We took several measurements on the isolated muscles (mass, length, physiological cross sectional area, etc.) and calculated the relative muscle masses and belly lengths of the major muscle groups to make interspecific comparisons. An extensive description of all foot and ankle muscles is given and differences between gibbons, bonobos and humans are discussed. No major differences were found between the foot and ankle musculature of both apes; however, marked differences were found between the ape and human foot. The human foot is specialized for solely one type of locomotion, whereas ape feet are extremely adaptable to a wide variety of locomotor modes. Apart from providing interesting anatomical data, this study can also be helpful for the interpretation of fossil (pre)hominids.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Clinically locating the point of no rotation to determine the subtalar joint axis location by applying pressure on the plantar surface of the foot was described by Kirby in 1987 but was never ...validated. We sought to extend a previously validated mechanical model to cadaver feet and to examine the intratester and intertester reliability.
Four testers with different levels of experience determined the subtalar joint axis location and moved the subtalar joint through its range of motion, capturing the movement using kinematic analysis. The comparison of the spatial subtalar joint axis location as determined by palpation between and within testers determined the intertester and intratester reliability. The helical axis method was performed to validate the model.
The intrarater reliability varied from a high of α = 0.96 to a low of α = 0.26 for the slope and was, in general, high (α = 0.78-0.95) for the intersection. The interrater reliability scored moderate to high, depending on the specific cadaver specimen. Concerning the exact location of the subtalar joint axis, no significant difference was found between the results determined by different testers and the helical axis method.
The palpation technique as part of the subtalar joint axis location and rotational equilibrium theory proposed by Kirby is a reliable and valid clinical tool. Experience in performing the palpation technique has a positive influence on the accuracy of the results. In the context of evidence-based practice, this technique could be a standard tool in the examination of patients with lower-limb-related pathologic disorders.
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