Amputee Christine 12 PORTABLE
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The energy cost of gait (C) is greater in amputee than in normal subjects. Our objective was to assess the influence of lower speed, inefficient pendulum mechanism and disturbed smoothness of centre of body mass (CM(b)) displacement on C in unilateral amputees and to have a better understanding the relationship between these variables. Twelve adult patients (six traumatic transfemoral and six vascular transtibial amputees) participated in the study. Lower limb kinematics, displacement of CM(b), mechanical work done by the muscles to move the CM(b) and the segments due to their movements relative to the CM(b), efficiency of the pendulum mechanism, and C were assessed simultaneously in the 12 amputees walking at their self-selected speed. Our results show that C depended on gait speed, and efficiency of pendulum-like mechanism of walking but did not depend on the smoothness of CM(b). The use of only a single variable to explain the extra cost in amputee gait could sometimes be misleading.
Accepting the award Dr. Kelly recounted Dick Traum's remarkable story. As an athlete at Horace Mann he was a wrestling team co-captain who coached others, and track team member who took on some of the tougher tasks of discus and shot. "He always took one for the team," said Dr. Kelly. After he was injured, it was a quote from educator Horace Mann that Traum learned at the School that pushed him to turn his disability into ability, for himself, and today, for the myriad people that Achilles International has helped directly. The quote was "Be ashamed to die until you have won some victory for humanity," Dr. Kelly told those gathered at the dinner. "When Dick Traum ran into the pages of history as the first amputee to complete a marathon, he won a victory for himself. The inspiration he provided countless other disabled, whether athlete or not, and the leadership he applied to founding and growing the Achilles organization, made that victory the win for humanity that we celebrate tonight. A high school athlete who led his team, took one for his team, and reached out to Horace Mann School alumni and students to be part of the worldwide team that grew from the Achilles Track Club he founded into Achilles International. We thank you Dick, and all of Achilles for honoring us tonight, but it is our School that is honored to be on your team."
Efficient walking or running requires symmetrical gait. Gait symmetry is one of the key factors in efficient human dynamics, kinematics and kinetics. The desire of individuals with a lower-limb amputation to participate in sports has resulted in the development of energy-storing-and-returning (ESR) feet. This paper analyses a case study to show the effect of symmetry and asymmetry as well as energy transfer efficiency during periodic jumping between simulated bilateral and unilateral runners. A custom gait analysis system is developed as part of this project to track the motion of the body of a physically active subject during a set of predefined motions. Stance and aerial times are accurately measured using a high speed camera. Gait frequency, the level of symmetry and the non-uniform displacement between left and right foot and their effects on the position of the Centre of Mass (CM) were used as criteria to calculate both peak energies and transformation efficiency. Gait asymmetry and discrepancy of energy transfer efficiency between the intact foot and the ESR are observed. It is concluded that unilateral runners require excessive effort to compensate for lack of symmetry as well as asymmetry in energy transfer, causing fatigue which could be a reason why bilateral amputee runners using ESR feet have a superior advantage over unilateral amputees.
Limb kinematics in transtibial amputee subjects are similar to those for individuals with sound limbs while kinematics for transfemoral amputees show a large gait asymmetry between contralateral limbs [6]. Physiological function is similar between amputee and intact limb subjects while mechanical function in sprinting differs between these two categories [7]. ESR prostheses allow amputees to reach the same energy cost when running as able-bodied persons [2]. Brüggemann et al. [3] showed that lower inertial properties of a prosthesis result in less mechanical work in lifting and accelerating the legs. Hobara et al. [8] discussed some advantages of ESR such as shorter swing time and longer contact lengths and disadvantages such as lower ground reaction force [9] and higher injury risks.
Noroozi et al. [4], studied the dynamic characteristics of Elite Blade composite feet, demonstrating the performance enhancing characteristics of these feet when used by a bilateral amputee in the latter stages of longer distance races such as 200 and 400 m. Vinney et al. [10] showed mathematical/FEA modelling of the ESR foot as means of performing inverse dynamics to be used to pre-set or tune the foot for walking, jogging, running and sprinting. Noroozi et al. [11] showed that modal analysis of the mass and foot system clearly determined the three main parameters in dynamic response: frequency, mode shape and damping. Noroozi et al. [12] also developed the basic theories behind the dynamic elastic response of these feet to cyclic and impulse excitation and also demonstrated their response to impulse synchronisation, which can result in a trampoline effect.
Current technology is not ready to provide perfectly symmetric gait for unilateral amputees. The difference between unilateral and bilateral dynamics when using ESR feet needs to be investigated further to determine participation of amputee athletes on both ethical [13] and physiological considerations [3, 7]. Further concerns have been raised about how this technology will be judged in the future to ensure ethical inclusion of such technology in disability sports [14]. This is also substantiated by Hassani et al. [15], who showed statistically that bilateral amputee using ESR feet dominated the Paralympic Games post 2008, when these ESR feet were first introduced.
By definition, asymmetry, or lack of symmetry, appears to be a relevant for differentiating normal from pathological gaits. Gait asymmetry is often described as a ratio of the kinematic or kinetic parameters between the right and left sides [16]. Different parameters have been used to determine gait asymmetry for amputees such as ratio index [17], coefficients of variation [18], correlation coefficients [19], symmetry index [20], variance ratios [21], principal component analysis [22], and root-mean-square difference [23], symmetry angle [24], butterfly plot [25] and autocorrelation coefficient [26]. According to Kaufman et al. [16], most of these tools have major limitations because they do not provide a measurement of the symmetry magnitude. Hence, the asymmetry effect cannot be quantified. This study proposes to use the jumping frequency and gait efficiency associated with displacement of centre of mass (CM) to investigate and quantify the asymmetry effect between the bilateral and unilateral amputees.
It is known that energetic costs of locomotion depend largely on body size, gait and speed. For example, previous research has shown that the energetic cost of walking and running increases progressively with the speed of movement [27]. Differences in energetic cost for different gait patterns such as running and walking have been also demonstrated [28, 29]. Energy consumption is commonly measured using heart rate and oxygen consumption, which can be further used in the analysis of the percent MHR (Maximum Heart Rate) and gait efficiency. However, it is difficult with these methods to detect the change due to large variability and therefore only suitable to be used as indicator of overall effort. Hall [30] and Rocha-Vieira [31] showed that the oscillation of the CM on the vertical plane is higher when running compared to walking, leading to a higher energy expenditure. A detailed discussion about the mechanical energy consequences for changes of the CM at different gravity values and walking speeds can be found in Cavagna et al. [32]. CM displacement is proportional to the energy expenditure of the person while jumping according to previous studies. The gait energy transfer efficiency for jumping activities is equal to displacement of CM during the aerial phase (output mechanical energy) divided by CM displacement at stance phase (input stored energy). In this study, the vertical oscillation of CM is used to evaluate the energy transfer efficiency between the simulated bilateral and unilateral amputees and the penalty in energy consumption needed to overcome the lack of gait symmetry.
Recent studies in this field have failed to propose a better model or improved understanding of the science involved. The effect of various parameters on the overall outcome is still undetermined. Therefore the gaps in the technology needed to achieve symmetric gait in in all classes of amputees still exists.
Movement of half of the trampoline was constrained by placing a rigid wooden box below one side of it, having the same height of trampoline. In this way one side of the trampoline (below one leg) acts like a rigid floor surface (known as the ground) while the other side (below the other leg) maintain its spring/elastic effect. The box was adjusted to minimise the leg length discrepancy during stance. If one foot bounces on the ground and one on trampoline, it will result in excessive use of energy to compensate for the lack of symmetry in energy consumption. Therefore, the effect of one of the key parameters behind difference in performance between unilateral and bilateral amputees in longer distance races could be investigated.
The results indicated that an able-bodied person and bilateral amputee require minimum effort to keep jumping frequency constant (i.e., the case where both feet contacting the ground/trampoline) compare to the unilateral amputee (i.e., the case where one foot contacting the ground and another foot contacting the trampoline). 2b1af7f3a8