Peak Power Research Articles

Chitosan-based anion exchange membranes for fuel cell application: Enhanced hydration & durability to dry-wet cycling

Herein, a new type of anion exchange membranes (AEMs) based on chitosan (CS) and poly(4-vinylbenzyl chloride) (PVB) polymers is reported. Depending on whether the PVB side chains are mono-cationic (quaternized PVB, QPVB) or di-cationic (di-quaternized PVB, DQPVB), the AEMs are denoted as QPVB@CS and DQPVB@CS, respectively. Due to the lateral aggregation of chitosan chains assisted by hydrogen bonds, the in-plane expansion is limited (1.4–11.5 % at 80 °C), resulting in excellent mechanical properties of AEMs (dry tensile strength of 55.2–81.0 MPa). And after 10 dry-wet cycles, the AEMs maintain their appearance and show improved mechanical properties. Due to high through-plane swelling degree, AEMs effectively retaining water (water uptake of 272.5–501.5 % at 80 °C) in the AEMs. DQPVB@CS AEMs, with their higher ion content, exhibit superior ionic conductivity (74.2–116.5 mS cm−1 at 80 °C) compared to QPVB@CS (27.7–44.3 mS cm−1 at 80 °C) and achieve a peak power density of 729.6 mW cm−2 in an anion exchange membrane fuel cell (AEMFC), versus 128.1 mW cm−2 for QPVB@CS-2. To the best of our knowledge, the AEMs developed in this study represent the first example of AEMs prepared from chitosan gel membranes, achieving anisotropic swelling degree, high water uptake, and excellent dry-wet cycling resistance without the need for additional chemical cross-linking.

Experimental Investigation of Energy Consumption in Select Micromobility Vehicles

<div>This study provides a detailed energy consumption analysis of two popular micromobility vehicles—an e-scooter and an e-bike—under various conditions, including steady-state and dynamics scenarios. Employing a custom-built data acquisition system, the research tested these vehicles in throttle mode, additionally assessing the e-bike across three pedal-assist levels. The findings reveal that the e-bike operates significantly more efficiently than the e-scooter, with both vehicles demonstrating peak power outputs significantly exceeding their rated values. Furthermore, the study explores how cargo affects the e-bike’s energy use, along with the charging and discharging behaviors of both platforms. Notably, the e-scooter exhibited a considerable battery self-depletion rate, a characteristic not observed on the e-bike.</div>

Dissipative soliton resonance in a normal dispersion all-polarization-maintaining thulium-doped fiber laser

We report a first demonstration of dissipative soliton resonance (DSR) in a normal dispersion thulium-doped fiber laser (TDFL) constructed entirely of polarization-maintaining fibers. A nonlinear fiber loop mirror with a combination of normal and anomalous dispersion fibers inside the loop ensures a self-starting mode-locking operation in the DSR regime. The oscillator generated linearly polarized optical pulses with a fundamental repetition frequency of 5.735 MHz and a nearly constant peak power clamped at ∼ 4.35 W. The pulse duration extends from 217 ps to 6 ns, when the pump power increases from 417 mW to 1.86 W. The maximum average output power of the DSR pulses was 151 mW, corresponding to the single pulse energy of 26 nJ.

Formation and conversion of high-peak-power structured beams by an Nd:YVO4/Cr4+:YAG laser subject to tight-focusing off-axis pumping

A compact Nd:YVO4/Cr4+:YAG passively Q-switched laser in a near-hemispherical resonator is exploited to realize high-peak-power pulsed beams with high spatial degrees of freedom. Beneficial from the advantages of strong intracavity beam focusing as well as the point-like excitation condition for the proposed cavity design, various high-order structured pulses as coherent superpositions of multiple degenerate eigenmodes are stably generated under different off-axis pump schemes. Besides, by employing external-cavity astigmatic mode conversion (AMC), the oval-shaped and chessboard-like structured pulses under on-axis and 1D off-axis pumping are transformed into exotic modes with polygonal and figure-eight-shaped envelopes to further enrich the spatial complexity of the generated fields. With well-defined beam structures that are reconstructed using the analytical resonant wave functions of the resonator, the phase structures of AMC pulsed fields are numerically resolved to present a variety of singularity arrays. Experimental results reveal that the overall peak power of the on-axis and off-axis generated structured pulses respectively exceeds 600 W and 1 kW while maintaining good pulse train stability with peak-to-peak amplitude fluctuation to be less than 10% and 15%.

Highly-Branched PtCu Nanocrystals with Low-Coordination for Enhanced Oxygen Reduction Catalysis.

Low-coordination platinum-based nanocrystals emanate great potential for catalyzing the oxygen reduction reactions (ORR) in fuel cells, but are not widely applied owing to poor structural stability. Here, several PtCu nanocrystals (PtCu NCs) with low coordination numbers were prepared via a facile one-step method, while the desirable catalyst structures were easily obtained by adjusting the reaction parameters. Wherein, the Pt1Cu1 NCs catalyst with abundant twin boundaries and high-index facets displays 15.25 times mass activity (1.647 A mgPt -1 at 0.9 VRHE) of Pt/C owing to the abundant effective active sites, low-coordination numbers and appropriate compressive strain. More importantly, the core-shell and highly developed dendritic structures in Pt1Cu1 NCs catalyst give it an extremely high stability with only 17.2% attenuation of mass activity while 61.1% for Pt/C after the durability tests (30 000 cycles). In H2-O2 fuel cells, Pt1Cu1 NCs cathode also exhibits a higher peak power density and a longer-term lifetime than Pt/C cathode. Moreover, theoretical calculations imply that the weaker adsorption of intermediate products and the lower formation energy barrier of OOH* in Pt1Cu1 NCs collaboratively boost the ORR process. This work offers a morphology tuning approach to prepare and stabilize the low-coordination platinum-based nanocrystals for efficient and stable ORR.

Novel optimized models to enhance performance forecasting of grid-connected PERC PV string operating under semi-arid climate conditions

This study focuses on modeling and forecasting the performance of a grid-connected photovoltaic (PV) string, aiming to enhance the accuracy of output power prediction, which is crucial for the effective management and stability of the electrical grid. While previous research has extensively examined PV modules, there is a notable lack of studies specifically targeting PV string behaviors, especially in harsh climates prevailing in semi-arid regions. This study addresses this gap by investigating the modeling and performance prediction of a Passivated Emitter Rear Cell (PERC) PV string under semi-arid climate conditions using analytical and predictive approaches based on both implicit and explicit models as Single Diode Model (SDM), Das Model (DM), Boutana et al. Model (BM) and Power Law Model (PLM). New mathematical models of DM and BM shape parameters versus temperature and irradiance along with novel analytical formulas giving DM shape parameters as a function of PV metrics have been introduced. The proposed approaches are validated using real measurements of a PERC PV string incorporating 12 JKM405M-72H PV modules operating at Green Energy Park (GEP) research facility in Morocco. The reliability of these approaches is assessed by comparing I-V curves, P-V curves and peak power generated and predicted by SDM, DM, BM and PLM to actual measurements. The comparison reveals that generated and predicted outcomes align well with measured data, with an average value of Normalized Root Mean Square Error (NRMSE) not exceeding 4.16 % for all models throughout the day. The findings indicate that the proposed approaches effectively predict the performance of the PERC PV string, accounting for climatic influences and providing insights into optimizing PV system performance, thereby contributing to improved grid stability in semi-arid regions.

Effects of concurrent heat and hypoxic training on cycling anaerobic capacity in men

Physical training in heat or hypoxia can improve physical performance. The purpose of this parallel group study was to investigate the concurrent effect of training performed simultaneously in heat (31 °C) and hypoxia (FIO2 = 14.4%) on anaerobic capacity in young men. For the study, 80 non-trained men were recruited and divided into 5 groups (16 participants per group): control, non-training (CTRL); training in normoxia and thermoneutral conditions (NT: 21 °C, FIO2 = 20.95%); training in normoxia and heat (H: 31 °C, FIO2 = 20.95%); training in hypoxia and thermoneutral conditions (IHT: 21 °C, FIO2 = 14.4%), and training in hypoxia and heat (IHT + H: 31 °C, FIO2 = 14.4%). Before and after physical training, the participants performed the Wingate Test, in which peak power and mean power were measured. Physical training lasted 4 weeks and the participants exercised 3 times a week for 60 min, performing interval training. Only the IHT and IHT + H groups showed significant increases in absolute peak power (p < 0.001, ES = 0.36 and p = 0.02, ES = 0.26, respectively). There were no significant changes (p = 0.18) after training in mean power. Hypoxia appeared to be an environmental factor that significantly improved peak power, but not mean power. Heat, added to hypoxia, did not increase cycling anaerobic power. Also, training only in heat did not significantly affect anaerobic power. The inclusion of heat and/or hypoxia in training did not induce negative effects, i.e., a reduction in peak and mean power as measured in the Wingate Test.

Thermally robust hierarchical nanofiber triboelectric yarns for efficient energy harvesting in firefighting E-textiles

Textile-based triboelectric nanogenerators (TENGs) face challenges in achieving high performance and fulfilling functional requirement for special applications. This paper presents the development of a high-performance, thermally robust hierarchical polyimide (PI) nanofiber triboelectric yarns with a charge-trapping interlayer for application in firefighting E-textiles. The hierarchical nanofiber yarns, comprising a stainless-steel core electrode, a PI/MXene interlayer and PI outer tribo-layer, exhibit enhanced triboelectric performance due to the charge-trapping capabilities of MXene, which preventing the recombination of triboelectric and induced charges. When the MXene content in the charge-trapping interlayer reached 1 wt%, the corresponding TENG achieved its optimal output performance, with an output voltage of 153 V and a current of 13.13 μA and a peak power density of 0.84 W/m2 under optimal conditions. It also demonstrates exceptional thermal stability, maintaining stable output at temperatures up to 400 °C. The integration of the TENG into E-textiles enables real-time monitoring of firefighters’ physical activities and location tracking, significantly enhancing their safety and operational efficiency in fire scenarios. Additionally, the TENG powers electroluminescent yarns, improving visibility in dense smoke and dust environments. This research opens new avenues for the application of smart wearable systems in high-temperature environments, providing effective strategies for ensuring the safety of firefighters in fire rescue operations.

Neural and muscular contributions to the age-related differences in peak power of the knee extensors in men and women.

The mechanisms for the loss in limb muscle power output in old (60-79 yr) and very old (≥80 yr) adults and whether the mechanisms differ between men and women are not well understood. We compared maximal peak power of the knee extensor muscles between young, old, and very old men and women and identified the neural and muscular factors contributing to the age-related differences in power. Thirty-one young (22.9 ± 3.0 yr, 15 women), 82 old (70.3 ± 4.9 yr, 38 women), and 16 very old adults (85.8 ± 4.2 yr, 9 women) performed maximal isokinetic contractions at 14 different velocities (30-450°/s) to identify peak power. Voluntary activation (VA) and contractile properties were assessed with transcranial magnetic stimulation to the motor cortex and electrical stimulation of the femoral nerve. The age-related loss in peak power was ∼6.5 W·yr-1 for men (R2 = 0.62, P < 0.001), which was a greater rate of decline (P = 0.002) than the ∼4.2 W·yr-1 for women (R2 = 0.77, P < 0.001). Contractile properties were the most closely associated variables with peak power for both sexes, such as the rate of torque development of the potentiated twitch (men: R2 = 0.69, P < 0.001; women: R2 = 0.57, P < 0.001). VA was weakly associated with power in women (R2 = 0.13, P = 0.012) but not in men (P = 0.191). Similarly, neuromuscular activation [rates of electromyography (EMG) rise] during the maximal power contraction was associated with power in women (R2 = 0.07, P = 0.042) but not in men (P = 0.456). These data suggest that the age-related differences in maximal peak power of the knee extensor muscles are due primarily to factors within the muscle for both sexes, although neural factors may play a minor role in older women.NEW & NOTEWORTHY The greater age-related loss in power relative to the loss in muscle mass of the knee extensors was primarily due to factors altering the contractile properties of the muscle for both old and very old (≥80 yr) adults. The mechanisms for the decrements in power with aging appear largely similar for men and women, although neural factors may play more of a role in older women.

In Vitro Comparison of Pulsed-Thulium:YAG, Holmium:YAG, and Thulium Fiber Laser.

Objective: To characterize the pulse characteristics and risk of fiber fracture (ROF) of the pulsed-Thulium:YAG (p-Tm:YAG) laser and to compare its ablation volumes (AVs) against Holmium:Yttrium-Aluminium-Garnet (Ho:YAG) laser and Thulium fiber laser (TFL). Materials and Methods: p-Tm:YAG (100 W-Thulio, Dornier-Medtech©, Germany) was characterized using single-use 272 μm core-diameter-fibers. p-Tm:YAG characterization included pulse shape, duration, and peak power (PP) studies. ROF was assessed after 5 minutes of continuous laser activation (CLA) at five decreasing fiber bend radii (1, 0.9, 0.75, 0.6, and 0.45 cm). p-Tm:YAG, Ho:YAG (120 W-Cyber-Ho, Quanta®, USA), and TFL (60 W-TFLDrive, Coloplast®, Denmark) AVs were compared using a 20-mm linear CLA at 2 mm/second velocity in contact with 20 mm3 hard stone phantoms (HSP) and soft stone phantoms (SSP) (15:3 and 15:5 water to powder ratio, respectively) fully submerged in saline at 0.5 J-20 Hz or 1 J-10 Hz. After CLA, phantoms underwent three-dimensional (3D) micro-scanning (CT) and subsequent 3D segmentation to estimate the AVs, using 3DSlicer©. Each experiment was performed in triplicate. Results: p-Tm:YAG presents a uniform pulse profile in all of the available preset modes. PP ranged from 564 to 2199 W depending on pulse mode. No laser fiber fracture occurred at any bend radius. p-Tm:YAG achieved similar mean AVs to TFL and Ho:YAG for HSP (8.96 ± 3.1 vs 9.78 ± 1.1 vs 8.8 ± 2.8 mm3, p = 0.67) but TFL was associated with higher AVs compared with p-Tm:YAG and Ho:YAG (12.86 ± 1.85 vs 10.12 ± 1.89 vs 7.56 ± 2.21 mm3, p = 0.002) against SSP. AVs for HSP increased with pulse energy for p-Tm:YAG and Ho:YAG and (11.56 ± 1.8 vs 6.36 ± 0.84 mm3 and 11.27 ± 1.98 vs 6.34 ± 0.55 mm3, p = 0.03 and p = 0.02), whereas AVs for SSP were similar across laser settings for all laser sources. AVs with TFL were similar across laser settings for both phantom types. Conclusion: p-Tm:YAG combines intermediate PP between Ho:YAG and TFL, a uniform pulse profile, no ROF with increasing deflection and effective ablation rates. Further clinical studies are needed to confirm these in vitro results.

Physiological and Performance Adaptations to Varying Rest Distributions During Short Sprint Interval Training Trials in Female Volleyball Players: A Comparative Analysis of Interindividual Variability.

This study aimed to examine the impact of different rest periods between short sprint interval training (SSIT) trials on the physiological and performance adaptations of female volleyball players. Twenty-four trained collegeathletes volunteered to participate in this study and were randomly assigned to 3 SSIT groups with different work-to-rest ratios (1:2 [5-s run:10-s rest], 1:4 [5-s run:20-s rest], and 1:6 [5-s work:30-s rest]). Before and after 6-week training, physiological parameters (maximum oxygen uptake, first and second ventilatory thresholds, and peak and mean power output) and physical performance measures (ie,countermovement vertical jump, 10-m sprint, and T-test change-of-direction speed) were evaluated. After the training period, all groups improved (P = .001) their sport-related performance and physiological parameters, ranging from moderate to very large effect sizes. Comparative analysis of the magnitude of training effects indicated thatthe 1:6 SSIT group had in a significantly greater change in countermovement vertical jump (P = .007), 10-m sprint (P = .014), peak power output (P = .019), and mean power output (P = .05) compared with 1:2 SSIT group. By contrast, the 1:2 SSIT group demonstrated significantly (P = .022) greater changes in maximum oxygen uptake than the 1:6 SSIT group. However, the change-of-direction speed and changes infirst and second ventilatory thresholds were the same among the groups (P > .05). When performing SSIT, longer rest intervals are suitable for physical and anaerobic performance, and shorter rest periods are appropriate for enhancing the cardiorespiratory fitness of female volleyball players' performance.

Acute Effects Of Blood Flow Restriction On Peak Power Across Gender, Athletic Status, Body Composition

Acute Effects Of Blood Flow Restriction On Peak Power Across Gender, Athletic Status, Body Composition

Broadband nanotubes-based nonlinear modulators for erbium- and thulium-doped lasers

Carbon-based nanomaterials have become a long-term research hotspot in the fields of material science and nanotechnology. Carbon nanotubes as one-dimensional nanomaterials have shown great application value in the fields of electronics and optoelectronics. Herein, stable mode-locked pulsed lasers in both 1.5- and 2-μm bands were achieved by combining and balancing the stimulated emission effect of rare-earth ions and saturable absorption effect of carbon nanotubes. In the Er-doped fiber laser, pulses with a SNR of 61 dB and a peak power of 2.97 W were achieved at the wavelength of 1565.8 nm. Meanwhile, bound states were observed in the same laser, where the time delay of pulses was adjustable from 9.84 to 21.77 ps by tuning the pump power and polarization state. In the Tm-doped laser, output pulses were obtained at the wavelength of 1921.0 nm with a 60-dB SNR and a 12.82-W peak power. These results demonstrate that carbon nanotubes are ideal candidates for saturable absorber in mode-locked fiber lasers, which can be applied to a variety of applications, including fiber optic sensing, optical communication, and nanoscale processing.

Effects of low and high dietary nitrate intake on human saliva, plasma and skeletal muscle nitrate and nitrite concentrations and their functional consequences

Dietary nitrate (NO3-) supplementation has been shown to reduce blood pressure (BP), improve exercise performance, and alter the oral microbiome. Following a "control" diet (CON), we manipulated dietary NO3- intake to examine the effect of a short-term (7-day) low NO3- diet (LOW) followed by a 3-day high NO3- diet (HIGH), compared to a 7-day standard (STD) NO3- diet followed by HIGH, on saliva, plasma, and muscle [NO3-] and nitrite [NO2-], BP, and cycling exercise performance in healthy young adults. We also examined the effect of LOW on the oral microbiome. Saliva [NO3-] and [NO2-], and plasma [NO3-] were significantly lower than CON following LOW (all P<0.05) but there was no change in plasma [NO2-] or muscle [NO3-] and [NO2-] (all P>0.05). Following HIGH, saliva and plasma [NO3-] and [NO2-], and muscle [NO3-], were significantly elevated above CON, LOW and STD (all P<0.05), but there was no difference between CON-LOW-HIGH and CON-STD-HIGH (P<0.05). BP and exercise performance were not altered following LOW (P>0.05). HIGH significantly reduced systolic and diastolic BP compared to CON when preceded by STD (both P<0.05) but not when preceded by LOW (P>0.05). Peak (+4%) and mean (+3%) power output during sprint cycling was significantly improved following HIGH (both P<0.05), with no differences between CON-LOW-HIGH and CON-STD-HIGH (both P>0.05). LOW altered the oral microbiome composition, including decreases in relative abundances of phylum Proteobacteria and genus Neisseria. The findings indicate that a short-term low NO3- diet lowers plasma but not skeletal muscle [NO3-]. The maintenance of plasma [NO2-] and muscle [NO3-] and [NO2-] following LOW may be indicative of their importance to biological functions, including BP regulation and exercise performance.

Muscle and tendon morphology of a world strongman and deadlift champion.

This study compared the muscle and tendon morphology of an extraordinarily strong individual, a World's Strongest Man and deadlift champion (WSM), with that of various other athletic, trained, and untrained populations. The WSM completed the following: 1) 3.0-T MRI scans, to determine the volume of 22 individual lower limb muscles, 5 functional muscle groups, patellar tendon (PT) cross-sectional area (CSA), and PT moment arm; and 2) countermovement jumps (CMJ) and isometric midthigh pull (IMTP) contractions. The WSM was compared with previously assessed groups from our laboratory (muscle and tendon) and the wider research literature (CMJ and IMTP). The WSM's CMJ peak power (9,866 W) and gross (9,171 N) and net (7,480 N) IMTP peak forces were higher than any previously published values. The WSM's overall measured leg muscle volume was approximately twice that of untrained controls (+96%) but with pronounced anatomical variability in the extent of muscular development. The plantar flexor group (+120%) and the guy rope muscles (sartorius, gracilis, and semitendinosus: +140% to +202%), which stabilize the pelvis and femur, demonstrated the largest differences relative to that of untrained controls. The WSM's pronounced quadriceps size (greater than or equal to twofold vs. untrained) was accompanied by modest PT moment arm differences and, notably, was not matched by an equivalent difference in PT CSA (+30%). These results provide novel insight into the musculotendinous characteristics of an extraordinarily strong individual, which may be toward the upper limit of human variation, such that the WSM's very pronounced lower limb muscularity also exhibited distinct anatomical variability and with muscle size largely uncoupled from tendon size.NEW & NOTEWORTHY Lower-body muscle size of an extraordinarily strong individual, a World's Strongest Man and deadlift champion (WSM), was approximately twice that of controls but was underpinned by pronounced anatomical variability in the extent of muscular development (+23-202%): the plantar flexor group and guy rope muscles demonstrating the largest differences. The WSM's quadriceps size (more than or equal to twice that of controls) contrasted with modest differences in patella tendon moment arm (+18%) and was uncoupled from patellar tendon size (+30%).

S-N co-doped porous carbon as metal-free ORR electrocatalysts in zinc-air batteries

The implementation of zinc-air batteries (ZABs) requires the creation of economically feasible electrocatalysts for the oxygen reduction reaction (ORR) process. In this work, sulfur-nitrogen co-doped porous carbon materials (S-N-PC) were synthesized using a straightforward approach including ball milling followed by calcination without solvent. The optimized S-N-PC 1000 demonstrates exceptional ORR performance in 0.1 M KOH, with a half-wave potential of 0.870 V that outperforms commercial Pt/C. Furthermore, it exhibits remarkable durability and exceptional methanol resistance. The S-N-PC 1000 performs excellent performance as an air cathode in ZABs, exhibiting a peak power density of 159.26 mW cm−2 and outstanding stability for up to 720 h. Additionally, the energy efficiency decreases by only 2.52 % after undergoing more than 2000 cycles of charging and discharging at 5 mA cm−2. This study offers a novel concept for the development of eco-friendly porous carbon catalysts for ZABs.

Development of an efficient bifunctional electrocatalyst based on Co/CoSe2 nanoparticles embedded in N, Se co-doped carbon for AEMFC and rechargeable Zn-air battery

We suggest a hollow-structured N, Se dual-doped carbon framework embedded with Co/CoSe2 nanoparticles (Co/CoSe2@NSeC) as highly efficient bifunctional electrocatalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The prepared electrocatalyst exhibits high electrochemical active surface area attributed to its unique hollow/porous structure and defective heteroatom doping sites. Furthermore, the strongly coupled heterojunction between Co and CoSe2 species not only provides abundant and highly active sites but also generates built-in electric field, thereby promoting electron transfer during the electrocatalytic reaction. Based on the above considerations, the prepared catalyst shows excellent bifunctional electrocatalytic performance. Leveraging the excellent ORR activity of Co/CoSe2@NSeC, alkaline exchange membrane fuel cells (AEMFC) with the Co/CoSe2@NSeC as air cathode exhibits high power density of 171.23 mW cm2. Furthermore, the rechargeable Zn-air battery employing the Co/CoSe2@NSeC shows high specific capacity (729.4 mAh gZn−1), peak power density (192.88 mW cm2), and sustained stability over 300 cycles.

Peak Power Properties of Band-Limited Signals: With Pulse Shaping or Windowing

Peak Power Properties of Band-Limited Signals: With Pulse Shaping or Windowing

Optimized-selenization preparation and laser Q-switching characteristics of layered PtSe2

Abstract PtSe2 has high carrier mobility, excellent electrical and optical properties, and high potential in the field of optoelectronic devices. In this paper, the conventional selenization method is optimized and a single-temperature zone preparation is used to prepare large-area and homogeneous PtSe2 thin-film materials on sapphire substrates in a shorter time and at a lower temperature. The prepared sample is characterized by optical microscopy, atomic force microscopy, Raman spectroscopy and Z-scan method. The saturable absorption properties of layered PtSe2 as a passive Q-switched are investigated in a solid-state laser. The results show that the PtSe2 thin film material is synthesized at 400 °C for 1 h to cover the entire one-inch sapphire wafer with a thickness of about 25 nm and the surface roughness is 13.1 nm. The modulation at 1064 nm yielded an output pulse with a maximum repetition frequency of 688.47 kHz, corresponding to a pulse width of 202.5 ns, a peak power of 7.35 W, a single-pulse energy of 1.51 μJ, and a stable pulse train.

The effect of prosthetic foot stiffness category on intact limb knee loading associated with osteoarthritis in people with transtibial amputation

Lower limb prosthesis users are at an increased risk of developing osteoarthritis in their intact knee. There is a scarcity of literature examining how the stiffness properties of commercially available prosthetic feet impact gait mechanics, including knee loading biomechanical variables that have been associated with the development of osteoarthritis. This study aimed to isolate the effect of commercial prosthetic foot stiffness on intact knee loading, prosthetic foot–ankle biomechanics, and user perception. Seventeen males with unilateral transtibial amputation were fit with three consecutive foot stiffness categories of a standardized energy-storing prosthetic foot in a randomized order and while blinded to foot condition. Biomechanical and self-report data were collected during level-ground walking in a motion analysis laboratory. As prosthetic foot stiffness increased, contralateral knee external adduction moment significantly decreased between stiff vs. medium and stiff vs. soft foot conditions. Prosthetic foot rollover radius increased as foot stiffness increased. However, prosthetic foot–ankle push-off peak power and work decreased as foot stiffness increased. On average, users favored the medium stiffness condition and were able to correctly identify the foot stiffness condition. Overall, these results raise questions about the relative contributions of foot stiffness and ankle push-off power to changes in contralateral knee loading. The findings contribute to our understanding of the relationships between prosthetic foot mechanical properties and gait biomechanical variables at the contralateral knee when prosthetic foot stiffness is modified without a corresponding alignment adjustment.