Estimation of finger muscle tendon tensions and pulley forces during specific sport-climbing grip techniques

The present work displayed the first quantitative data of forces acting on tendons and pulleys during specific sport-climbing grip techniques. A three-dimensional static biomechanical model was used to estimate finger muscle tendon and pulley forces during the "slope" and the "crimp" grip. In the slope grip the finger joints are flexed, and in the crimp grip the distal interphalangeal (DIP) joint is hyperextended while the other joints are flexed. The tendons of the flexor digitorum profundus and superficialis (FDP and FDS), the extensor digitorum communis (EDC), the ulnar and radial interosseus (UI and RI), the lumbrical muscle (LU) and two annular pulleys (A2 and A4) were considered in the model. For the crimp grip in equilibrium conditions, a passive moment for the DIP joint was taken into account in the biomechanical model. This moment was quantified by relating the FDP intramuscular electromyogram (EMG) to the DIP joint external moment. Its intensity was estimated at a quarter of the external moment. The involvement of this parameter in the moment equilibrium equation for the DIP joint is thus essential. The FDP-to-FDS tendon-force ratio was 1.75:1 in the crimp grip and 0.88:1 in the slope grip. This result showed that the FDP was the prime finger flexor in the crimp grip, whereas the tendon tensions were equally distributed between the FDP and FDS tendons in the slope grip. The forces acting on the pulleys were 36 times lower for A2 in the slope grip than in the crimp grip, while the forces acting on A4 were 4 times lower. This current work provides both an experimental procedure and a biomechanical model that allows estimation of tendon tensions and pulley forces crucial for the knowledge about finger injuries in sport climbing.     

In vivo knee moments and shear after total knee arthroplasty

Tibiofemoral loading is very important in cartilage degeneration as well as in component survivorship after total knee arthroplasty. We have previously reported the axial knee forces in vivo. In this study, a second-generation force-sensing device that measured all six components of tibial forces was implanted in a 74-kg, 83-year-old male. Video motion analysis, ground reaction forces, and knee forces were measured during walking, stair climbing, chair-rise, and squat activities. Peak total force was 2.3 times body weight (BW) during walking, 2.5 x BW during chair rise, 3.0 x BW during stair climbing, and 2.1 x BW during squatting. Peak anterior shear force at the tibial tray was 0.30 x BW during walking, 0.17 x BW during chair rise, 0.26 x BW during stair climbing, and 0.15 x BW during squatting. Peak flexion moment at the tray was 1.9% BW x Ht (percentage of body weight multiplied by height) for chair-rise activity and 1.7% BW x Ht for squat activity. Peak adduction moment at the tray was -1.1% BW x Ht during chair-rise, -1.3% BW x Ht during squatting. External knee flexion and adduction moments were substantially greater than flexion and adduction moments at the tray. The axial component of forces predominated especially during the stance phase of walking. Shear forces and moments at the tray were very modest compared to total knee forces. These findings indicate that the soft tissues around the knee absorbed most of the external shear forces. Our results highlight the importance of direct measurements of knee forces.     

A method for in vivo measurements of implants used in the reconstruction of spinal fractures]

Little is known about the forces and moments acting on the spinal column during various movements and activities, and thus about the loading of implants used in the treatment of spinal fractures. A measuring method using an external fixation device was developed to determine the in vivo loading of spinal implants. On the basis of these data the forces acting on the spine can be calculated. The present paper describes this measuring method as applied to the fixation device, and initial experience with this device in a first application is presented.     

Hip contact forces and gait patterns from routine activities.

In vivo loads acting at the hip joint have so far only been measured in few patients and without detailed documentation of gait data. Such information is required to test and improve wear, strength and fixation stability of hip implants. Measurements of hip contact forces with instrumented implants and synchronous analyses of gait patterns and ground reaction forces were performed in four patients during the most frequent activities of daily living. From the individual data sets an average was calculated. The paper focuses on the loading of the femoral implant component but complete data are additionally stored on an associated compact disc. It contains complete gait and hip contact force data as well as calculated muscle activities during walking and stair climbing and the frequencies of daily activities observed in hip patients. The mechanical loading and function of the hip joint and proximal femur is thereby completely documented. The average patient loaded his hip joint with 238% BW (percent of body weight) when walking at about 4 km/h and with slightly less when standing on one leg. This is below the levels previously reported for two other patients (Bergmann et al., Clinical Biomechanics 26 (1993) 969-990). When climbing upstairs the joint contact force is 251% BW which is less than 260% BW when going downstairs. Inwards torsion of the implant is probably critical for the stem fixation. On average it is 23% larger when going upstairs than during normal level walking. The inter- and intra-individual variations during stair climbing are large and the highest torque values are 83% larger than during normal walking. Because the hip joint loading during all other common activities of most hip patients are comparably small (except during stumbling), implants should mainly be tested with loading conditions that mimic walking and stair climbing.     

Stair climbing is more critical than walking in pre-clinical assessment of primary stability in cementless THA in vitro

Pre-clinical testing of hip endoprostheses is a mandatory requirement before clinical release. Inadequate loading conditions may lead to lower elastic and plastic interface movements than those occurring post-operatively in vivo. This study investigated the influence of patient activity on the primary stability of cementless prostheses with a special emphasis on active simulation of muscle forces. A loading setup, based on validated musculo-skeletal analyses, was used to generate the hip contact force during walking and stair climbing by transmitting muscle forces through the femur. In addition, a loading configuration which only generated the hip contact force occurring during stair climbing at the prosthesis head was simulated. CLS prostheses were implanted in 18 composite femora and subjected to cyclical loading. The relative micro-movements at the bone-prosthesis interface were determined and appeared to be extremely sensitive to the specific patient activity. Compared to walking, stair climbing generated higher micro-movements, with pronounced axial and rotational components. Stair climbing with the femur loaded by the resultant hip contact force only exhibited a characteristic valgus tilt of the stem with significantly lower interface micro-movements than under active simulation of muscle forces. The analyses suggest that stair climbing induced the highest mechanical instability at the bone-prosthesis interface, a level which may compromise the necessary osseointegration process. Active simulation of muscle forces considerably affects the primary stability of cementless hip endoprostheses. Pre-clinical in vitro tests should therefore simulate stair climbing and include muscle activity in the assessment of initial implant stability, otherwise micro-movements may be underestimated and the primary stability overestimated.     

支持物倾角对攀援植物栝楼形态和生长的影响

支持物倾角的变化将引起攀援植物“自遮荫”程度的改变 ,从而影响植物的生长和行为。以攀援植物栝楼 ( Trichosantheskirilowii)为材料 ,通过实验生态学的方法 ,研究了 4种支持物倾角下植株的生长和觅食行为的差异。结果表明 :( 1 )不同生长发育期栝楼植株形态对自遮荫差异的可塑性反应程度不一 ,不同角度攀援生长植株在生长前期均比生长后期有较敏感的形态可塑性反应。 ( 2 )自遮荫程度随支持物倾角的增大而增强 ,较强自遮荫环境下植株比较弱自荫环境下的植株有更大的形态可塑性。 ( 3)比主茎长、比叶面积、生物量对叶片和叶柄的配置在 4种攀援生长形式间差异均不显著。不同角度攀援植株主要通过改变分枝数量、分枝形态和分枝生物量配置以适应支持物倾角的变化 ,这说明 ,自遮荫对植株形态和生物量配置仅产生有限的影响。 ( 4 )分枝能力、分枝数量以及分枝生物量配置均在大角度攀援生长中最大 ,且与小角度攀援生长植株间有显著差异。 ( 5 )水平攀援生长植株主要通过增大主茎生物量投资以充分占有生境 ,而大角度攀援生长植株则主要通过分枝茎扩展以占据有利生境 ,不同攀援生长植株有不同的觅食行为。     

A dynamic force analysis system for climbing of large primates

Registering substrate reaction forces from primates during climbing requires the design and construction of customized recording devices. The technical difficulties in constructing a reliable apparatus hinder research on the kinetics of primate locomotion. This is unfortunate since arboreal locomotion, especially vertical climbing, is an important component of the hominoid locomotor repertoire. In this technical paper, we describe a custom-built climbing pole that allows recordings of dynamic 3-dimensional forces during locomotion on horizontal and sloping substrates and during vertical climbing. The pole contains an instrumented section that can readily be modified and enables us to register forces of a single limb or multiple limbs in a broad range of primates. For verification, we constructed a similar set-up (which would not be usable for primates) using a conventional force plate. Data for a human subject walking on both set-ups were compared. The experimental set-up records accurate and reliable substrate reaction forces in three orthogonal directions. Because of its adjustability, this type of modular set-up can be used for a great variety of primate studies. When combining such kinetic measurements together with kinematic information, data of great biomechanical value can be generated. These data will hopefully allow biological anthropologists to answer current questions about primate behaviours on vertical substrates.     

Should tendon and aponeurosis be considered in series?

Fibres, aponeuroses, and tendons are often considered mechanically "in series" in skeletal muscles. This notion has led to oversimplified calculations of fibre forces from tendon forces, to incorrect derivations of constitutive laws for aponeuroses, and to misinterpretations of the recovery of elastic energy in stretch-shortening cycles of muscles. Here, we demonstrate theoretically, using examples of increasing complexity, that tendon and aponeurosis are not in series in a muscle fibre-aponeurosis-tendon complex. We then demonstrate that assuming the tendon and aponeurosis to be in series can lead to the appearance of mechanical work creation in these passive viscoelastic structures, a result that is mechanically impossible. Finally, we explain the mechanical role of the incompressible muscle matrix in force transmission from fibres to aponeuroses and tendon, and emphasize that incompressibility necessitates the introduction of extra forces necessary to maintain this constraint. Unfortunately, this requirement eliminates, for all but the simplest cases, a theoretical approach of muscle modeling based on intuitive free-body diagrams.     

Robot-based methodology for a kinematic and kinetic analysis of unconstrained,but reproducible upper extremity movement

Although arm movements play an important role in everyday life, there is still a lack of procedures for the analysis of upper extremity movement. The main problems for standardizing the procedure are the variety of arm movements and the difficult assessment of external hand forces. The first problem requires the predefinition of motions, and the second one is the prerequisite for calculation of net joint forces and torques arising during motion. A new methodology for measuring external forces during prespecified, reproducible upper extremity movement has been introduced and validated. A robot-arm has been used to define the motion and 6 degrees of freedom (DoF) force sensor has been attached to it for acquiring the external loads acting on the arm. Additionally, force feedback has been used to help keeping external loads constant. Intra-individual reproducibility of joint angles was estimated by using correlation coefficients to compare a goal-directed movement with robot-guided task. Inter-individual reproducibility has been evaluated by using the mean standard deviation of joint angles for both types of movement. The results showed that both inter- and intra-individual reproducibility have significantly improved by using the robot. Also, the effectiveness of using force feedback for keeping a constant external load has been shown. This makes it possible to estimate net joint forces and torques which are important biomechanical information in motion analysis.     

Effects of Pendular Waist on Gecko's Climbing: Dynamic Gait,Analytical Model and Bio-inspired Robot

Most quadruped reptiles,such as lizards,salamanders and crocodiles,swing their waists while climbing on horizontal or vertical surfaces.Accompanied by body movement,the centroid trajectory also becomes more of a zigzag path rather than a straight line.Inspired by gecko's gait and posture on a vertical surface,a gecko inspired model with one pendular waist and four active axil legs,which is called GPL model,is proposed.Relationship between the waist position,dynamic gait,and driving forces on supporting feet is analyzed.As for waist trajectory planning,a singular line between the supporting feet is found and its effects on driving forces are discussed.Based on the GPL model,it is found that a sinusoidal waist trajectory,rather than a straight line,makes the driving forces on the supporting legs smaller.Also,a waist close to the pygal can reduce the driving forces compared to the one near middle vertebration,which is in accord with gecko's body bending in the process of climbing.The principles of configuration design and gait planning are proposed based on theoretical analyses.Finally,a bio-inspired robot DracoBot is developed and both of the driving force measurements and climbing experiments reinforce theoretical analysis and the rationality of gecko's dynamic gait.     

Forces and moments telemetered from two distal femoral replacements during various activities.

Two distal femoral replacements were instrumented to measure axial force, torque and bending moments in the prosthesis shaft. Data are reported up to 2.5 years for the following activities: uni- and bi-lateral standing, walking, stair climbing and descending, treadmill walking, jogging and jumping. In the first subject the greatest averaged peak shaft forces found were: jogging 3.6Bodyweight (BW), stair descending 3.1BW, walking 2.8BW, treadmill walking 2.75BW, and stair ascending 2.8BW. Bending moments about the antero-posterior axis (varus-valgus) and medio-lateral axis (flexion-extension) peaked in the range 8.5-9.8 and 4.7-7.6BWcm respectively, over the follow-up period. Axial torques peaked in the range 0.2-1.3BWcm, outwardly directed. At most follow-up sessions, forces and moments during jogging were generally greater than those for other gait activities. In the second subject forces and moments were generally only 45-70% of those in the first subject, due to inadequate musculature around the knee. The data can be applied to the design and testing of distal femoral replacements and even to total knee replacements, and contributes to the knowledge of forces acting in the distal femur during activity.     

An instrumented shoe—A portable force measuring device

Effective protection from fracture for diseased or partially healed bones can be quantitatively developed only with a knowledge of the external forces applied to the bone. While force studies using force plates have documented the forces for certain activities, a more portable force measuring device is required to determine forces during most daily activities. The authors have developed an instrumented shoe with load cells attached directly to the shoe which measured orthogonal components of foot-to-ground forces and moments. Goniometers simultaneously monitor the position of the lower leg. The signals are transported to a system of loads acting at the lower leg. Typical load curves are presented.     

Bone morphogenetic proteins are involved in the pathobiology of synovial chondromatosis

Synovial chondromatosis is characterized by the formation of osteocartilaginous nodules (free bodies) under the surface of the synovial membrane in joints. Free bodies and synovium isolated from synovial chondromatosis patients expressed high levels of BMP-2 and BMP-4 mRNAs. BMP-2 stimulated the expression of Sox9, Col2a1, and Aggrecan mRNAs in free-body and synovial cells and that of Runx2, Col1a1, and Osteocalcin mRNAs in the free-body cells only. BMP-2 increased the number of alcian blue-positive colonies in the free-body cell culture but not in the synovial cell culture. Noggin suppressed the expression of Sox9, Col2a1, Aggrecan, and Runx2 mRNAs in both the free-body and synovial cells. Further, it inhibited Osteocalcin expression in the synovial cells. These results suggest that BMPs are involved in the pathobiology of cartilaginous and osteogenic metaplasia observed in synovial chondromatosis.     

Interpreting the Role of Climbing in Primate Locomotor Evolution: Are the Biomechanics of Climbing Influenced by Habitual Substrate Use and Anatomy?

Vertical climbing is widely accepted to have played an important role in the origins of both primate locomotion and of human bipedalism. Yet, only a few researchers have compared climbing mechanics in quadrupedal primates that vary in their degree of arboreality. It is assumed that primates using vertical climbing with a relatively high frequency will have morphological and behavioral specializations that facilitate efficient climbing mechanics. We test this assumption by examining whether time spent habitually engaged in climbing influences locomotor parameters such as footfall sequence, peak forces, and joint excursions during vertical climbing. Previous studies have shown that during climbing, the pronograde and semiterrestrial Macaca fuscata differs in these parameters compared to the more arboreal and highly specialized, antipronograde Ateles geoffroyi. Here, we examine whether a fully arboreal, quadrupedal primate that does not regularly arm-swing will exhibit gait and force distribution patterns intermediate between those of Macaca fuscata and Ateles geoffroyi. We collected footfall sequence, limb peak vertical forces, and 3D hindlimb excursion data for Macaca fascicularis during climbing on a stationary pole instrumented with a force transducer. Results show that footfall sequences are similar between macaque species, whereas peak force distributions and hindlimb excursions for Macaca fascicularis are intermediate between values reported for M. fuscata and Ateles geoffroyi. These results support the notion that time spent climbing is reflected in climbing mechanics, even though morphology may not provide for efficient mechanics, and highlight the important role of arboreal locomotor activity in determining the pathways of primate locomotor evolution.     

Tolerance of snakes to hypergravity

Sensitivity of carotid blood flow to increased gravitational force acting in the head-to-tail direction(+Gz) was studied in diverse species of snakes hypothesized to show adaptive variation of response. Tolerance to increased gravity was measured red as the maximum graded acceleration force at which carotid blood flow ceased and was shown to vary according to gravitational adaptation of species defined by their ecology and behavior. Multiple regression analysis showed that gravitational habitat, but not body length, had a significant effect on Gz tolerance. At the extremes, carotid blood flow decreased in response to increasing G force and approached zero near +1 Gz in aquatic and ground-dwelling species, whereas in climbing species carotid flow was maintained at forces in excess of +2 Gz. Tolerant (arboreal) species were able to withstand hypergravic forces of +2 to +3 Gz for periods up to 1 h without cessation of carotid blood flow or loss of body movement and tongue flicking. Data suggest that the relatively tight skin characteristic of tolerant species provides a natural antigravity suit and is of prime importance in counteracting Gz stress on blood circulation.     

Musculo-skeletal loading conditions at the hip during walking and stair climbing.

Musculo-skeletal loading plays an important role in the primary stability of joint replacements and in the biological processes involved in fracture healing. However, current knowledge of musculo-skeletal loading is still limited. In the past, a number of musculo-skeletal models have been developed to estimate loading conditions at the hip. So far, a cycle-to-cycle validation of predicted musculo-skeletal loading by in vivo measurements has not been possible. The aim of this study was to determine the musculo-skeletal loading conditions during walking and climbing stairs for a number of patients and compare these findings to in vivo data.Following total hip arthroplasty, four patients underwent gait analysis during walking and stair climbing. An instrumented femoral prosthesis enabled simultaneous measurement of in vivo hip contact forces. On the basis of CT and X-ray data, individual musculo-skeletal models of the lower extremity were developed for each patient. Muscle and joint contact forces were calculated using an optimization algorithm. The calculated peak hip contact forces both over- and under-estimated the measured forces. They differed by a mean of 12% during walking and 14% during stair climbing.For the first time, a cycle-to-cycle validation of predicted musculo-skeletal loading was possible for walking and climbing stairs in several patients. In all cases, the comparison of in vivo measured and calculated hip contact forces showed good agreement.Thus, the authors consider the presented approach as a useful means to determine valid conditions for the analysis of prosthesis loading, bone modeling or remodeling processes around implants and fracture stability following internal fixation.     

Bone contact forces on the distal tibia during the stance phase of running

Although the tibia is a common site of stress fractures in runners, the loading of the tibia during running is not well understood. An integrated experimental and modeling approach was therefore used to estimate the bone contact forces acting on the distal end of the tibia during the stance phase of running, and the contributions of external and internal sources to these forces. Motion capture and force plate data were recorded for 10 male runners as they ran at 3.5-4 m/s. From these data, the joint reaction force (JRF), muscle forces, and bone contact force on the tibia were computed at the ankle using inverse dynamics and optimization methods. The distal end of the tibia was compressed and sheared posteriorly throughout most of stance, with respective peak forces of 9.00+/-1.13 and 0.57+/-0.18 body weights occurring during mid stance. Internal muscle forces were the primary source of tibial compression, whereas the JRF was the primary source of tibial shear due to the forward inclination of the leg relative to the external ground reaction force. The muscle forces and JRF both acted to compress the tibia, but induced tibial shear forces in opposing directions during stance, magnifying tibial compression and reducing tibial shear. The superposition of the peak compressive and posterior shear forces at mid stance may contribute to stress fractures in the posterior face of the tibia. The implications are that changes in running technique could potentially reduce stress fracture risk.     

On Heels and Toes: How Ants Climb with Adhesive Pads and Tarsal Friction Hair Arrays

Ants are able to climb effortlessly on vertical and inverted smooth surfaces. When climbing, their feet touch the substrate not only with their pretarsal adhesive pads but also with dense arrays of fine hairs on the ventral side of the 3^rd and 4^th tarsal segments. To understand what role these different attachment structures play during locomotion, we analysed leg kinematics and recorded single-leg ground reaction forces in Weaver ants (Oecophylla smaragdina) climbing vertically on a smooth glass substrate. We found that the ants engaged different attachment structures depending on whether their feet were above or below their Centre of Mass (CoM). Legs above the CoM pulled and engaged the arolia (‘toes’), whereas legs below the CoM pushed with the 3^rd and 4^th tarsomeres (‘heels’) in surface contact. Legs above the CoM carried a significantly larger proportion of the body weight than legs below the CoM. Force measurements on individual ant tarsi showed that friction increased with normal load as a result of the bending and increasing side contact of the tarsal hairs. On a rough sandpaper substrate, the tarsal hairs generated higher friction forces in the pushing than in the pulling direction, whereas the reverse effect was found on the smooth substrate. When the tarsal hairs were pushed, buckling was observed for forces exceeding the shear forces found in climbing ants. Adhesion forces were small but not negligible, and higher on the smooth substrate. Our results indicate that the dense tarsal hair arrays produce friction forces when pressed against the substrate, and help the ants to push outwards during horizontal and vertical walking.     

Abigaille-Ⅲ： A Versatile,Bioinspired Hexapod for Scaling Smooth Vertical Surfaces

This paper presents a novel, legged robot, Abigaille-Ⅲ, which is a hexapod actuated by 24 miniature gear motors. This robot uses dual-layer dry adhesives to climb smooth, vertical surfaces. Because dry adhesives are passive and stick to various surfaces, they have advantages over mechanisms such as suction, claws and magnets. The mechanical design and posture of Abigaille-Ⅲ were optimized to reduce pitchback forces during vertical climbing. The robot＇s electronics were designed around a Field Programmable Gate Array, producing a versatile computing architecture. The robot was reconfigured for vertical climbing with both 5 and 6 legs, and with 3 or 4 motors per leg, without changes to the electronic hardware. Abigaille-Ⅲ demonstrated dexterity through vertical climbing on uneven surfaces, and by transferring between horizontal and vertical sur- faces. In endurance tests, Abigaille-Ⅲ completed nearly 4 hours of continuous climbing and over 7 hours of loitering, showing that dry adhesive climbing systems can be used for extended missions.     

Determination of muscle loading at the hip joint for use in pre-clinical testing

The stability of joint endoprostheses depends on the loading conditions to which the implant-bone complex is exposed. Due to a lack of appropriate muscle force data, less complex loading conditions tend to be considered in vitro. The goal of this study was to develop a load profile that better simulates the in vivo loading conditions of a "typical" total hip replacement patient and considers the interdependence of muscle and joint forces. The development of the load profile was based on a computer model of the lower extremities that has been validated against in vivo data. This model was simplified by grouping functionally similar hip muscles. Muscle and joint contact forces were computed for an average data set of up to four patients throughout walking and stair climbing. The calculated hip contact forces were compared to the average of the in vivo measured forces. The final derived load profile included the forces of up to four muscles at the instances of maximum in vivo hip joint loading during both walking and stair climbing. The hip contact forces differed by less than 10% from the peak in vivo value for a "typical" patient. The derived load profile presented here is the first that is based on validated musculoskeletal analyses and seems achievable in an in vitro test set-up. It should therefore form the basis for further standardisation of pre-clinical testing by providing a more realistic approximation of physiological loading conditions.