Qualitative comparison of bird and bat wakes has demonstrated significant differences in the structure of the far wake. Birds have been found to have a unified vortex wake of the two wings, while bats have a more complex wake with gradients in the circulation along the wingspan, and with each ...

We have studied the nocturnal flight behaviour of the common swift (Apus apus L.), by the use of a tracking radar. Birds were tracked from Lund University in southern Sweden during spring migration, summer roosting flights and autumn migration. Flight speeds were compared with predictions from flight mechanical and optimal ...

Directed aerial descent (i.e. gliding and manoeuvring) may be an important stage in the evolution of winged flight. Although hypothesized to occur in ancestrally wingless insects, such behaviour is unexplored in extant basal hexapods, but has recently been described in arboreal ants. Here we show that tropical arboreal bristletails (Archaeognatha) ...

The aim of this study was to use a subject-specific seven-link wobbling mass model of a gymnast, and a multi-layer model of a landing mat, to determine landing strategies that minimise ground reaction forces (GRF) and internal forces. Subject-specific strength parameters were determined that defined the maximum voluntary torque/angle/angular velocity ...

The aim of this study was to analyse the principal mechanics of circles. Seventeen university male gymnasts performed circles on an instrumented pommel horse model that enabled the pommel reaction forces to be recorded at 1000 Hz with two force plates. The circles were also videotaped using two digital video ...

Birds and bats have evolved powered flight independently, which makes a comparison of evolutionary 'design' solutions potentially interesting. In this paper we highlight similarities and differences with respect to flight characteristics, including morphology, flight kinematics, aerodynamics, energetics and flight performance. Birds' size range is 0.002-15 kg and bats' size range ...

REASONS FOR PERFORMING STUDY: Track surface quality is considered a risk factor of musculoskeletal injuries. Ground reaction force (GRF) measurement is a relevant approach to study the interaction between the hoof and the ground. Force plates are not adapted to compare different surfaces at high speed. A 3D dynamometric horseshoe ...

CONTEXT: Researchers have suggested that large landing forces, excessive quadriceps activity, and an erect posture during landing are risk factors for anterior cruciate ligament (ACL) injury. The influence of knee kinematics on these risk factors has been investigated extensively, but trunk positioning has received little attention. OBJECTIVE: To determine the ...

REASONS FOR PERFORMING STUDY: Inadequate track surfaces are believed to be a risk factor in the occurrence of musculoskeletal injuries, but quantification of the shocks and vibrations provoked by hoof impact on different ground surfaces (including new synthetic tracks) has been insufficiently documented in trotters under high-speed training conditions. OBJECTIVES: ...

Insectivorous echolocating bats face a formidable array of defenses employed by their airborne prey. One such insect defense is the ultrasound-triggered dive, which is a sudden, rapid drop in altitude, sometimes all the way to the ground. Although many previous studies have investigated the dynamics of such dives and their ...

The aim of this study was to determine whether elite 1500-m runners differ in their running kinematics from national-standard 1500-m runners. Six national-standard male runners (seasonal best: 3 min 49.2 s +/- 3.2 s) were assessed during the second lap of a 1500-m race. Their running kinematics was then compared ...

REASONS FOR PERFORMING STUDY: At rising trot the rider sits alternately down on one diagonal pair of limbs and rises up on the other. The possible effects on asymmetry of locomotion induced by rising trot have rarely been studied. OBJECTIVES: To demonstrate whether, and if so to what extent, rising ...

During locomotion, the human body exhibits inherent dynamic properties such as mass (M), stiffness (K) and damping (B). During the gait cycle, foot contact with the ground progresses from the heel to the toe. Contact forces between the foot and ground are defined as ground reaction forces (GRF). It is ...

The exotic beetle Ophraella communa LeSage was first found in 1996 in Japan and has rapidly expanded its distribution. This study examined the effect of several factors on the flight activity of this beetle and estimated its dispersal potential by measuring its flight time on a flight mill system. The ...

Ontogenetic and behavioral studies using birds currently do not document the early evolution of flight because birds (including juveniles) used in such studies employ forelimb oscillation frequencies over 10 Hz, forelimb stroke-angles in excess of 130 degrees , and possess uniquely avian flight musculatures. Living birds are an advanced morphological ...

Dynamic similarity is a widely used concept in the fluid mechanics field, and consists in placing two different-sized systems in equivalent experimental conditions. This enables removal of the effects of size and prediction of the behavior of a full size system from a scale model. The aim of this study ...

In team sports, such as basketball and volleyball, the players use different takeoff styles to make the vertical jump. The two-foot vertical jump styles have been classified according to the landing style and identified as hop style, when both feet touch the ground at the same time, and step-close style, ...

The purpose of this investigation was to examine the impact of training on the power-, force-, and velocity-time curves of the countermovement jump (CMJ) through both cross-sectional and longitudinal comparisons. The most novel aspect of this study was the analysis of these curves for the entire movement at a sampling ...

The purpose of this study was to investigate the effects of instructional and motivational self-talk on performance and the kinematics of the vertical jump. After completing a 10-minute warm-up on a stationary bike, 12 men (mean +/- SD; 20.8+/- 3.0 years, 77.8 +/- 13.5 kg, 1.78 +/- 0.07 m) and ...

Ion-sensitive, field-effect transistors (ISFET) have been useful biosensors in many applications. However, the signal-to-noise ratio of the ISFET is limited by its intrinsic, low-frequency noise. This paper presents an ISFET capable of utilizing lateral-bipolar conduction to reduce low-frequency noise. With a particular layout design, the conduction efficiency is further enhanced. ...

Here, we present a detailed analysis of the wing kinematics and wing deformations of desert locusts (Schistocerca gregaria, Forskål) flying tethered in a wind tunnel. We filmed them using four high-speed digital video cameras, and used photogrammetry to reconstruct the motion of more than 100 identified points. Whereas the hindwing ...

Delay onset of the vastus medialis obliquus (VMO) has often been reported to happen in people with patellofemoral pain (PFP). Previous studies revealed that a motion control shoe could check rearfoot pronation in overpronators. Literature suggested that movements of the lower leg could affect patellar tracking; thus motion control shoe ...

OBJECTIVE: To evaluate manual wheelchair propulsion across level ground conditions that are encountered during everyday life. DESIGN: Subjects included 14 individuals (13 with spinal cord injury [SCI], 1 with spina bifida) who were experienced manual wheelchair users and had no current upper extremity injury or pain complaints. Subjects propelled their ...

The aim of this study was to introduce a Newton-Euler inverse dynamics model that included reaction force and moment estimation at the lumbo-sacral (L5-S1) and thoraco-lumbar (T12-L1) joints. Data were collected while participants ran over ground at 3.8 m x s(-1) at three different stride lengths: preferred stride length, 20% ...

Cross-sectional study. The purpose of this study was to examine stroke characteristics of long-term manual wheelchair users during an extended manual wheelchair propulsion trial and the extent to which changes in propulsion biomechanics occurred. Human Engineering Research Laboratories, VA Rehabilitation Research and Development Center, VA Pittsburgh Healthcare Systems, Pittsburgh, PA, ...

The authors performed an experiment in which participants (N = 24) made judgments about maximum jump and reachability on ground surfaces with different elastic properties: sand and a trampoline. Participants performed judgments in two conditions: (a) while standing and after having recently jumped on the surface in question and (b) ...

This study compared the conventional track and a new one-handed track start in elite age group swimmers to determine if the new technique had biomechanical implications on dive performance. Five male and seven female GB national qualifiers participated (mean +/- SD: age 16.7 +/- 1.9 years, stretched stature 1.76 +/- ...

In earthquake hazard assessment studies, the focus is usually on horizontal ground motion. However, records from the 14 June 2008 Iwate-Miyagi earthquake in Japan, a crustal event with a moment magnitude of 6.9, revealed an unprecedented vertical surface acceleration of nearly four times gravity, more than twice its horizontal counterpart. ...

Evidence for the simplification of motor control of the limbs through a reduction in the number of degrees of freedom exists in areas of research such as neuroscience, robotics, and biomechanics. Human hopping in place can be modeled well with spring-mass dynamics and provides a tractable model by which to ...

OBJECTIVES: In this study, the effect of shoe degradation on running biomechanics by comparing the kinetics and kinematics of running in new and worn shoes was investigated. Three types of footwear using different cushioning technologies were compared. DESIGN: Longitudinal study. SETTING: Pre- and post-tests on overground running at 4.5 m ...

The aim of this study was to investigate the relationship between the kinematics and kinetics of a single-leg horizontal drop jump (SLDJ) to sprint performance. Twenty regional-level male team-sport athletes gave informed consent to participate in this study. All subjects performed a series of 25-m sprints (measured by dual-beam infrared ...

Flying a parabolic trajectory in an aircraft is one of the few ways to create freefall on Earth, which is important for astronaut training and scientific research. Here we review the physics underlying parabolic flight, explain the resulting flight dynamics, and describe several counterintuitive findings, which we corroborate using experimental ...

This study examined three visual strategies for timing the initiation of the landing flare based on perceptions of either: (a) a critical height above ground level; (b) a critical runway width angle (Psi); or (c) a critical time-to-contact (TTC) with the runway. Visual displays simulated landing approaches with trial-to-trial variations ...

The purpose of this article is to provide strength and conditioning practitioners with an understanding of the role of elastic energy in activities with high force and power requirements. Specifically, the article covers 1) the nature of elasticity and its application to human participants, 2) the role of elastic energy ...

The purpose of the present study was to analyze the effects of bad collocation of the wing tag on feather amelanosis, the heterophil-to-lymphocyte ratio, fluctuating asymmetry, and tonic immobility duration at 140 d of age in hens from the White-Faced Black Spanish breed. A total of 52 females were used. ...

Kinematic and kinetic methods (sacral marker, reconstructed pelvis, segmental analysis, and force platform methods) have been used to calculate the vertical excursion of the center of mass (COM) during movement. In this study we compared the measurement of vertical COM displacement yielded by different methods during able-bodied subjects' hopping at ...

To understand complex sensory-motor behavior related to object perception by echolocating bats, precise measurements are needed for echoes that bats actually listen to during flight. Recordings of echolocation broadcasts were made from flying bats with a miniature light-weight microphone and radio transmitter (Telemike) set at the position of the bat's ...

The unsteady flow and acoustic characteristics of the flapping wing are numerically investigated for a two-dimensional model of Bombus terrestris bumblebee at hovering and forward flight conditions. The Reynolds number Re, based on the maximum translational velocity of the wing and the chord length, is 8800 and the Mach number ...

An alternative method for the measurement of the total mechanical impulse of a vertically directed blast due to an explosive charge is presented. The method differs from apparatus that employ a vertically displaced mass (similar in principle to the ballistic pendulum) in that a relatively compact spring-damper system is employed ...

The time courses of wing and body kinematics of three freely hovering droneflies (Eristalis tenax) were measured using 3D high-speed video, and the morphological parameters of the wings and body of the insects were also measured. The measured wing kinematics was used in a Navier-Stokes solver to compute the aerodynamic ...

Quantify manual wheelchair propulsion effort during outdoor community ambulation. Case series. Thirteen individuals (12 with SCI, 1 with spina bifida) who were experienced manual wheelchair users and had no current upper extremity injury or pain complaints. Measurements were obtained from instrumented wheelchair rims during steady-state propulsion as subjects traversed outdoor ...

PURPOSE: In rowing, the athlete has to maximize power output and to minimize energy losses to processes unrelated to average shell velocity. The contribution of velocity efficiency (evelocity; the fraction of mechanical power not lost to velocity fluctuations) to rowing performance in relation to the contributions of maximum oxygen uptake ...

In competitive rowing, the fluctuations in boat velocity during the rowing cycle are associated with an increased water resistance of the boat as compared with a boat moving at a constant velocity. We aimed to quantify the influence of the increased water resistance on race time using a mathematical approximation, ...

Shock reduction has been well studied in moderate activities such as walking and running. However, there is a clear lack of research concerning shock wave transmission and reduction in more strenuous landing activities. In this study, we examined the impact of shock transmission and reduction in landing activities with varied ...

The purpose of the study was to provide practical suggestions on the effect of stretching on the maximal anaerobic power preceded by active or passive warm-up. To this aim, 15 relatively fit male subjects (age 23 +/- 0.2 years, height 177 +/- 2 cm, body mass 74 +/- 2 kg; ...

A prototype instrument for measuring astronaut body mass under microgravity conditions has been developed and its performance was evaluated by parabolic flight tests. The instrument, which is the space scale, is applied as follows. Connect the subject astronaut to the space scale with a rubber cord. Use a force transducer ...

Ascending or descending locomotion involves a change in potential energy (PE) and a corresponding change in power requirement. We sought to test whether the mechanical power required for steady ascending or descending flight is a simple sum of the power required for level flight and the power necessary for potential ...

To assess the effect of leg length on jumping ability in small insects, the jumping movements and performance of a sub-family of leafhopper insects (Hemiptera, Auchenorrhyncha, Cicadellidae, Ulopinae) with short hind legs were analysed and compared with other long-legged cicadellids (Hemiptera, Auchenorrhyncha, Cicadellidae). Two species with the same jumping characteristics ...

Gliding saves much energy, and to make large distances using only this form of flight represents a great challenge for both birds and people. The solution is to make use of the so-called thermals, which are localized, warmer regions in the atmosphere moving upwards with a speed exceeding the descent ...

BACKGROUND AND PURPOSE: Previous studies have demonstrated an increase in foot pronation with mileage in runners. Motion control footwear was designed to check excessive foot motions, but its clinical efficacy, especially in terms of pedographic analysis, has not been well reported. The purposes of this study were to investigate the ...