PURPOSEThe loads applied on the musculoskeletal system during the long jump takeoff step are not well established for nonamputee athletes or athletes with a lower extremity amputation. Information on ...joint loading and potential injury mechanisms is important for improving training or rehabilitation protocols, prosthetic design, and the general understanding of the long jump.
METHODSThree-dimensional takeoff step kinematics and kinetics were used for inverse dynamic model calculations on three male athletes with and seven male athletes without a below the knee amputation (BKA). Athletes with BKA used their affected leg as their takeoff leg.
RESULTSDespite equivalent long jump performance, ground reaction force application characteristics were widely different, and calculated joint loads were significantly lower in athletes with BKA compared with nonamputee athletes during the takeoff step. The takeoff step of the long jump for athletes with BKA seems to be dominated by sagittal plane movements, whereas it involves sagittal plane movement and compensatory joint work in the frontal plane for nonamputee athletes.
CONCLUSIONSCoaches and athletes should adapt training protocols to the unique musculoskeletal loading patterns of long jumpers with or without a BKA. Specifically, nonamputee athletes should strengthen the muscles responsible for hip and knee extension, as well as for frontal plane stabilization, early in the season to avoid injuries. The presented data enable clinicians to identify potential causes of pain or injury more differentially in both groups of athletes and might stimulate future research in the field of robotics and prosthetic components. Furthermore, the altered joint mechanics of athletes with BKA versus nonamputees serves as an explanation for their previously described more effective takeoff step.
Running-prostheses have enabled exceptional athletes with bilateral leg amputations to surpass Olympic 400 m athletics qualifying standards. Due to the world-class performances and relatively fast ...race finishes of these athletes, many people assume that running-prostheses provide users an unfair advantage over biologically legged competitors during long sprint races. These assumptions have led athletics governing bodies to prohibit the use of running-prostheses in sanctioned non-amputee (NA) competitions, such as at the Olympics. However, here we show that no athlete with bilateral leg amputations using running-prostheses, including the fastest such athlete, exhibits a single 400 m running performance metric that is better than those achieved by NA athletes. Specifically, the best experimentally measured maximum running velocity and sprint endurance profile of athletes with prosthetic legs are similar to, but not better than those of NA athletes. Further, the best experimentally measured initial race acceleration (from 0 to 20 m), maximum velocity around curves, and velocity at aerobic capacity of athletes with prosthetic legs were 40%, 1-3% and 19% slower compared to NA athletes, respectively. Therefore, based on these 400 m performance metrics, use of prosthetic legs during 400 m running races is not unequivocally advantageous compared to the use of biological legs.
People have debated whether athletes with transtibial amputations should compete with nonamputees in track events despite insufficient information regarding how the use of running-specific prostheses ...(RSPs) affect athletic performance. Thus, we sought to quantify the spatiotemporal variables, ground reaction forces, and spring-mass mechanics of the fastest athlete with a unilateral transtibial amputation using an RSP to reveal how he adapts his biomechanics to achieve elite running speeds. Accordingly, we measured ground reaction forces during treadmill running trials spanning 2.87 to 11.55 m/s of the current male International Paralympic Committee T44 100- and 200-m world record holder. To achieve faster running speeds, the present study’s athlete increased his affected leg (AL) step lengths ( P < 0.001) through longer contact lengths ( P < 0.001) and his unaffected leg (UL) step lengths ( P < 0.001) through longer contact lengths ( P < 0.001) and greater stance average vertical ground reaction forces ( P < 0.001). At faster running speeds, step time decreased for both legs ( P < 0.001) through shorter ground contact and aerial times ( P < 0.001). Unlike athletes with unilateral transtibial amputations, this athlete maintained constant AL and UL stiffness across running speeds ( P ≥ 0.569). Across speeds, AL step lengths were 8% longer ( P < 0.001) despite 16% lower AL stance average vertical ground reaction forces compared with the UL ( P < 0.001). The present study’s athlete exhibited biomechanics that differed from those of athletes with bilateral and without transtibial amputations. Overall, we present the biomechanics of the fastest athlete with a unilateral transtibial amputation, providing insight into the functional abilities of athletes with transtibial amputations using running-specific prostheses.
NEW & NOTEWORTHY The present study’s athlete achieved the fastest treadmill running trial ever attained by an individual with a leg amputation (11.55 m/s). From 2.87 to 11.55 m/s, the present study’s athlete maintained constant affected and unaffected leg stiffness, which is atypical for athletes with unilateral transtibial amputations. Furthermore, the asymmetric vertical ground reaction forces of athletes with unilateral transtibial amputations during running may be the result of leg length discrepancies.
People with unilateral transtibial amputation (TTA) using a passive-elastic prosthesis exhibit lower positive affected leg trailing work (AL trail W pos ) and a greater magnitude of negative ...unaffected leg leading work (UL lead W neg ) during walking than non-amputees, which may increase joint pain and osteoarthritis risk in the unaffected leg. People with TTA using a stance-phase powered prosthesis (e.g., BiOM, Ottobock, Duderstadt, Germany) walk with increased AL trail W pos and potentially decreased magnitude of UL lead W neg compared to a passive-elastic prosthesis. The BiOM includes a passive-elastic prosthesis with a manufacturer-recommended stiffness category and can be tuned to different power settings, which may change AL trail W pos, UL lead W neg, and the prosthesis effective foot length ratio (EFLR). Thirteen people with TTA walked using 16 different prosthetic stiffness category and power settings on a level treadmill at 0.75–1.75 m/s. We constructed linear mixed effects models to determine the effects of stiffness category and power settings on AL trail W pos, UL lead W neg, and EFLR and hypothesized that decreased stiffness and increased power would increase AL trail W pos , not change and decrease UL lead W neg magnitude, and decrease and not change prosthesis EFLR, respectively. We found there was no significant effect of stiffness category on AL trail W pos but increased stiffness reduced UL lead W neg magnitude, perhaps due to a 0.02 increase in prosthesis EFLR compared to the least stiff category. Furthermore, we found that use of the BiOM with 10% and 20% greater than recommended power increased AL trail W pos and decreased UL lead W neg magnitude at 0.75–1.00 m/s. However, prosthetic power setting depended on walking speed so that use of the BiOM increased UL lead W neg magnitude at 1.50–1.75 m/s compared to a passive-elastic prosthesis. Ultimately, our results suggest that at 0.75–1.00 m/s, prosthetists should utilize the BiOM attached to a passive-elastic prosthesis with an increased stiffness category and power settings up to 20% greater than recommended based on biological ankle values. This prosthetic configuration can allow people with unilateral transtibial amputation to increase AL trail W pos and minimize UL lead W neg magnitude, which could reduce joint pain and osteoarthritis risk in the unaffected leg and potentially lower the metabolic cost of walking.
Prosthetic stiffness likely affects the walking biomechanics of toddlers and children with leg amputations, but the actual stiffness values for prostheses are not reported by manufacturers or in ...standardized testing procedures.
We measured axial (kA) and torsional (kT) stiffness from four brands of pediatric prosthetic feet (Trulife, Kingsley Mfg. Co., TRS Incorporated, and College Park Industries) over a range of foot sizes.
We applied forces and torques onto prostheses with a materials testing machine that replicated those exhibited in vivo by using the kinetics measured from four non-amputee toddlers (2–3years) during walking.
Across brands, kA averaged 35.2kN/m during heel loading, was more stiff during midfoot loading (121.8kN/m, P<0.001) and less stiff during forefoot loading (11.8kN/m, P=0.013). kA was similar across brands with no statistically significant effect of prosthetic foot size, with the exception of the TRS feet. Plantarflexion torsional stiffness (kT1), was not statistically different across brands. For every 1cm increase in foot size, kT1 increased 0.16kN·m/rad (P<0.001). College Park prostheses had 4.54kN·m/rad lower dorsiflexion torsional stiffness (kT2) (P<0.001) compared to other brands. For every 1cm increase in foot size, the kT2 applied on the foot increased 0.63kN·m/rad.
The axial and torsional stiffness testing methods are reproducible and should be adopted by prosthetic foot manufacturers. Axial and torsional stiffness values of commercially available prosthetic feet should be publically reported to health practitioners to ensure evidence-based decisions and meet the specific needs of each patient with a leg amputation.
•Prosthetic stiffness affects the gait of toddlers and children with leg amputations.•We present methods to measure axial and torsional stiffness in prosthetic feet.•We compared four of the most commonly prescribed brands of pediatric prostheses.•Prosthetists should select pediatric prosthetic feet based on objective measures.
Passive-elastic prosthetic feet are manufactured with numerical stiffness categories and prescribed based on the user's body mass and activity level, but mechanical properties, such as stiffness ...values and hysteresis are not typically reported. Since the mechanical properties of passive-elastic prosthetic feet and footwear can affect walking biomechanics of people with transtibial or transfemoral amputation, characterizing these properties can provide objective metrics for comparison and aid prosthetic foot prescription and design.
We characterized axial and torsional stiffness values, and hysteresis of 33 categories and sizes of a commercially available passive-elastic prosthetic foot model Össur low-profile (LP) Vari-flex with and without a shoe. We assumed a greater numerical stiffness category would result in greater axial and torsional stiffness values but would not affect hysteresis. We hypothesized that a greater prosthetic foot length would not affect axial stiffness values or hysteresis but would result in greater torsional stiffness values. We also hypothesized that including a shoe would result in decreased axial and torsional stiffness values and greater hysteresis.
Prosthetic stiffness was better described by curvilinear than linear equations such that stiffness values increased with greater loads. In general, a greater numerical stiffness category resulted in increased heel, midfoot, and forefoot axial stiffness values, increased plantarflexion and dorsiflexion torsional stiffness values, and decreased heel, midfoot, and forefoot hysteresis. Moreover, for a given category, a longer prosthetic foot size resulted in decreased heel, midfoot, and forefoot axial stiffness values, increased plantarflexion and dorsiflexion torsional stiffness values, and decreased heel and midfoot hysteresis. In addition, adding a shoe to the prosthetic foot resulted in decreased heel and midfoot axial stiffness values, decreased plantarflexion torsional stiffness values, and increased heel, midfoot, and forefoot hysteresis.
Our results suggest that manufacturers should adjust the design of each category to ensure the mechanical properties are consistent across different sizes and highlight the need for prosthetists and researchers to consider the effects of shoes in combination with prostheses. Our results can be used to objectively compare the LP Vari-flex prosthetic foot to other prosthetic feet to inform their prescription, design, and use for people with a transtibial or transfemoral amputation.
Abstract During level-ground walking, mechanical work from each leg is required to redirect and accelerate the center of mass. Previous studies show a linear correlation between net metabolic power ...and the rate of step-to-step transition work during level-ground walking with changing step lengths. However, correlations between metabolic power and individual leg power during step-to-step transitions while walking on uphill/downhill slopes and at different velocities are not known. This basic understanding of these relationships between metabolic demands and biomechanical tasks can provide important information for design and control of biomimetic assistive devices such as leg prostheses and orthoses. Thus, we compared changes in metabolic power and mechanical power during step-to-step transitions while 19 subjects walked at seven slopes (0°, +/−3°, +/−6°, and +/−9°) and three velocities (1.00, 1.25, and 1.50 m/s). A quadratic model explained more of the variance ( R2 =0.58–0.61) than a linear model ( R2 =0.37–0.52) between metabolic power and individual leg mechanical power during step-to-step transitions across all velocities. A quadratic model explained more of the variance ( R2 =0.57–0.76) than a linear model ( R2 =0.52–0.59) between metabolic power and individual leg mechanical power during step-to-step transitions at each velocity for all slopes, and explained more of the variance ( R2 =0.12–0.54) than a linear model ( R2 =0.07–0.49) at each slope for all velocities. Our results suggest that it is important to consider the mechanical function of each leg in the design of biomimetic assistive devices aimed at reducing metabolic costs when walking at different slopes and velocities.
Purpose
we determined the metabolic and biomechanical effects of adding mass to the running-specific prosthesis (RSP) and biological foot of individuals with a unilateral transtibial amputation (TTA) ...during running.
Methods
10 individuals (8 males, 2 females) with a TTA ran on a force-measuring treadmill at 2.5 m/s with 100 g and 300 g added to their RSP alone or to their RSP and biological foot while we measured their metabolic rates and calculated peak vertical ground reaction force (vGRF), stance-average vGRF, and step time symmetry indices.
Results
for every 100 g added to the RSP alone, metabolic power increased by 0.86% (
p
= 0.007) and for every 100 g added to the RSP and biological foot, metabolic power increased by 1.74% (
p
<
0.001) during running. Adding mass had no effect on peak vGRF (
p
= 0.102), stance-average vGRF (
p
= 0.675), or step time (
p
= 0.413) symmetry indices. We also found that the swing time of the affected leg was shorter than the unaffected leg across conditions (
p
<
0.007).
Conclusions
adding mass to the lower limbs of runners with a TTA increased metabolic power by more than what has been reported for those without an amputation. We found no effect of added mass on biomechanical asymmetry, but the affected leg had consistently shorter swing times than the unaffected leg. This suggests that individuals with a TTA maintain asymmetries despite changes in RSP mass and that lightweight prostheses could improve performance by minimizing metabolic power without affecting asymmetry.
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