High Peak Power Output Research Articles

13 μm emission InAs/AlSb quantum cascade lasers with high slope efficiency and peak output power enabled by diagonal transition design

Long wavelength InAs/AlSb quantum cascade lasers (QCLs) emitting at 13 μm, based on a diagonal transition scheme design through band structure engineering, have been grown and fabricated. This band structure engineering focuses on enhancing transition efficiency and suppressing carrier leakage. Our 3-mm-long, 25-μm-wide InAs/AlSb QCL has achieved a slope efficiency of 210 mW/A and a maximum peak power of 515 mW, despite encountering a substantial waveguide loss of 27 cm−1 and a relatively high threshold of 4.8 kA/cm2, due to the elevated residual doping level. Our InAs/AlSb QCL devices have demonstrated record-breaking performance in terms of slope efficiency, maximum peak power, and injection efficiency. Cavity length analysis suggests that reducing the residual doping by half could pave the way for achieving continuous wave output power in the realm of hundreds of milliwatts at room temperature for our designed 13 μm QCLs.

Are There Sex Differences in Anaerobic Performance Following a Dynamic Warm-Up? A Randomized, Counterbalanced, and Crossover Design Study

The increasing trend of females participating in elite and historically male-dominated sports has also resulted in a rise in females performing dynamic warm-ups (DWs). DW is a widely used practice in hockey. However, there is scarce evidence describing how DWs impact subsequent anaerobic performance and whether this response differs between sexes. This study aimed to determine sex differences in anaerobic performance when preceded by a DW. Twenty National Collegiate Athletics Association Division-II hockey players (n = 20, 10 female) completed a Wingate Anaerobic Test (WAnT) preceded by a DW or no warm-up in a randomized, counterbalanced order and followed a crossover design. The DW was ∼8 min long and consisted of 13 movements that targeted prime muscles and joints involved in ice skating. The WAnT consisted of a 30-s, maximal effort sprint against 7.5% of the participant’s body mass performed on a cycle ergometer. Peak power output (PPO), relative peak power (RPP), mean anaerobic power (MP), and fatigue index (FI) evaluated anaerobic performance during the WAnT. There were no significant differences between male and female scores following DW. MP was significantly higher in males and females, but PPO, RPP, and FI were not when a DW preceded the WAnT. In both conditions, males had higher PPO and MP than females, while there were no sex differences in RPP and FI. In conclusion, performing a DW before a WAnT improved MP for females and males with no adverse effects on PPO, RPP, and FI. This study suggests that DW might benefit hockey players independently of sex.

Dual Mode TENG with Self‐Voltage Multiplying Circuit for Blue Energy Harvesting and Water Wave Monitoring

AbstractAs the most extensive natural energy on earth, ocean wave energy is regarded as a difficult energy to be fully and efficiently utilized because of its low frequency and multi‐direction movement. Herein, a versatile blue energy triboelectric nanogenerator (VBE‐TENG) fabricated by using dual‐mode output terminals with charge excitation strategy is reported, which can harvest varying water‐wave energy effectively. Benefiting from the rolling ball on a specific track and the compression rebound characteristics of a spring sheet steel, the carrier can be driven along a specific path through random ocean wave energy, and then the energy is converted into electricity by VBE‐TENG. A high peak output power of 34.3 mW is obtained, 2.5 times as much as that of current highest record based on a device unit in blue energy TENG. In addition, the TENG can light 256 LEDs and continuously power commercial electronic devices in wave environments. The average peak voltage of contact‐separation TENG is converted into virtual signal via Labview software to provide wave height monitoring as a self‐powered sensing system. This work provides a new approach in blue energy TENG toward practical applications.

Metabolic Cost and Mechanical Efficiency of a Novel Handle-Based Device for Wheelchair Propulsion.

To investigate differences in metabolic cost and gross mechanical efficiency of a novel handlebased wheelchair propulsion device and to compare its performance with conventional push-rim propulsion. Double-group comparative study between 2 different propulsion methods. Eight paraplegic individuals and 10 non-disabled persons. Participants performed the same exercise using a push-rim device and the novel handle-based device on a wheelchair- based test rig. The exercise consisted of a combined submaximal and maximal test. Power output, oxygen uptake, ventilation, respiratory exchange ratio and heart rate were recorded continuously during the tests. Analysis of variance was performed to determine the effects of group, mode and on power output. Submaximal exercise resulted in a higher efficiency for the novel device and significant main effects of propulsion mode on all investigated parameters, except heart rate. On the respiratory exchange ratio, a significant interaction effect was found for both mode and group. The maximal exercise resulted in a higher peak power output and lower peak heart rate during propulsion using the handle-based device. A significant main effect on mode for mean peak power output, ventilation and heart rate was also observed. Wheelchair propulsion using the handle-based device resulted in lower physical responses and higher mechanical efficiency, suggesting that this novel design may be well suited for indoor use, thereby offering an attractive alternative to pushrim wheelchairs.

Study of Generation of Singlet Oxygen in Human Saliva <i>in vitro</i> Under the Action of Nanosecond Pulsed Laser Radiation

Background. The development of new laser devices for use in the treatment of complex dental pathology and microsurgery of the oral cavity with unique parameters with the ability to generate nanosecond pulsed radiation in a quasi-monochromatic radiation band is necessary. The high peak output power per pulse allows laser light to penetrate deeper into biological media without significant heating. The possibility of excitation of singlet oxygen without the use of endogenous photosensitizers is an indisputable advantage of such laser generators.
 Aims study of singlet oxygen generation in human oral fluid in vitro depending on the parameters of nanosecond pulsed laser radiation with a wavelength of ~1265 nm.
 Methods. We used a laser device with a main infrared (IR) emitter with a wavelength approximately corresponding to the oxygen absorption maximum (~1265 nm) with the generation of nanosecond pulsed radiation. A study was carried out to study the generation of singlet oxygen in the human oral fluid and the washing out of the oral fluid by the fading of the trap in solutions under the action of laser radiation before irradiation, after 30 and 60 min. The laser radiation parameters were set as follows: power 1 W, nanosecond pulsed radiation with a pulse duration of 400 ns and a frequency of 0.5, 1.0, 1.5 and 2.0 MHz in comparison with the continuous radiation mode.
 Results. It has been established that nanosecond laser radiation leads to the oxidation of a chemical singlet oxygen trap solubilized with sodium dodecyl sulfate (0.05 M SDS) detergent in the oral fluid and saliva flushing from the oral cavity. In pulsed nanosecond modes, laser radiation is more efficient than in continuous mode. With an increase in the repetition frequency, an increase in the effect by an average of 10% compared to a lower frequency was observed and the effect with a maximum frequency of 2.0 MHz was almost 50% higher than when using continuous radiation in all studies. A decrease in optical density at 414 nm was reliably observed in samples with oral fluid washing, the effect was 0.07 0.01 for 60 min of exposure. In the oral fluid, the effect with the same parameters was slightly lower and amounted to 0.05 0.03.
 Conclusions. The rate of fading of the trap in the saliva wash turned out to be 1.3 times faster than in water with detergent, which may indicate the activation of photoacceptors and their oversaturation with oxygen when using aqueous dilution of the oral fluid. The maximum effect was observed when using laser radiation with a pulse repetition rate of 2.0 MHz.

High-peak-power picosecond deep-UV laser sources.

Ultrafast deep-UV laser sources have extensive applications across a wide number of fields, whether biomedicine, photolithography, industrial processing, or state-of-the-art scientific research. However, it has been challenging to obtain deep-UV laser sources with high conversion efficiency and output peak power. Here, we simultaneously demonstrated high-peak-power picosecond deep-UV laser sources at two typical wavebands of 263.2 and 210.5 nm via the efficient fourth- and fifth-harmonic generation. The highest peak power of 263.2 and 210.5 nm laser radiations were up to 2.13 GW (6.72 ps) and 1.38 GW (5.08 ps). The overall conversion efficiencies from the fundamental wave to the fourth and fifth harmonic were up to 42.9% and 28.8%, respectively. The demonstrated results represent the highest conversion efficiencies and output peak powers of picosecond deep-UV laser sources at present to our knowledge. Additionally, we also systematically characterized the deep-UV optical properties of typical birefringent and nonlinear borate crystals, including α-BaB2O4, β-BaB2O4, LiB3O5, and CsLiB6O10 crystals. The experiments and obtained numerous new optical data in this work will contribute to the generation of ultrahigh-peak-power deep-UV and vacuum-UV laser sources and crucial applications in both science and industry, such as high-energy-density physics, material science, and laser machining.

Physiological Responses and Performance During a 3-Minute Cycle Time Trial: Standard Paced Versus All-Out Paced.

To compare performance and physiological responses between a standard-paced 3-minute time trial (TTSP, ie,pacing based on normal intention) and a consistently all-out-paced 3-minute time trial (TTAOP). Sixteen well-trained male cyclists completed the TTSP and TTAOP, on separate days of testing, on a cycling ergometer with power output and respiratory variables measured. Time trials were preceded by 7 × 4-minute submaximal stages of increasing intensity with the linear relationship between power output and metabolic rate used to estimate the contribution from aerobic and anaerobic energy resources. The time course of anaerobic and aerobic contributions to power output was analyzed using statistical parametric mapping. Mean power output was not different between the 2 pacing strategies (TTSP = 417 [43] W, TTAOP = 423 [41] W; P = 0.158). TTAOP resulted in higher peak power output (P < .001), mean ventilation rate (P < .001), mean heart rate (P = .044), peak accumulated anaerobically attributable work (P = .026), post-time-trial blood lactate concentration (P = .035), and rating of perceived exertion (P = .036). Statistical parametric mapping revealed a higher anaerobic contribution to power output during the first ∼30 seconds and a lower contribution between ∼90 and 170 seconds for TTAOP than TTSP. The aerobic contribution to power output was higher between ∼55 and 75 seconds for TTAOP. Although there was no significant difference in performance (ie,mean power output) between the 2 pacing strategies, differences were found in the distribution of anaerobically and aerobically attributable power output. This implies that athletes can pace a 3-minute maximal effort very differently but achieve the same result.

Efficient self-powered piezoelectric energy harvesting interface circuit with wide rectified voltage

Synchronized Switching Harvesting on Inductor (SSHI) and Synchronous Electric Charge Extraction (SECE) are two classic interface circuit techniques for Piezoelectric energy harvesting. But the former has high peak output power with narrow rectified voltage range, while the latter has wide rectified voltage range with lower peak output power. This paper presents a self-powered interface circuit for piezoelectric energy harvesting to achieve a good balance between the two. The proposed interface circuit is based on the Series-SSHI (S–SSHI) and SECE. The circuit proposed can harvest energy through S–SSHI and SECE in positive and negative half cycles, respectively. Moreover, the figure of merit (FOM), optimal rectified voltage range (ORVR) and region of interest (SRoI) of simulation and experiment results are discussed. The maximum FOM of the proposed circuit is as high as 2.15, which is 1.68 times that of the SECE, and it can reach 6 times the ORVR of the S–SSHI. SRoI factor of the proposed circuit show that the proposed method has better performance. In addition, the circuit shows a simpler implementation compared with state-of-the-art designs.

25.4 kW, 1.9 ns passively Q-switched 1522 nm Er:Yb:LuAl3(BO3)4 pulse microlaser at 100 Hz.

Passively Q-switched Er:Yb:LuAl3(BO3)4 pulse microlasers were investigated at a low repetition frequency of 10-200 Hz. End-pumped by a 975.6 nm quasi-continuous-wave laser diode with pump pulse width of 0.5 ms and period of 10 ms, a stable 1522 nm pulse microlaser with single pulse energy of 48.3 μJ, duration of 1.9 ns, repetition frequency of 100 Hz, peak output power of 25.4 kW and beam quality factor less than 1.2 was realized at a pump beam waist diameter of 260 μm. This eye-safe passively Q-switched pulse microlaser with high peak output power and narrow duration can be used in the portable laser rangefinder.

Acute effects of exercise on cerebrovascular response and cognitive performance in individuals with stable coronary heart disease

BackgroundIndividuals with coronary heart disease (CHD) exhibit cognitive deficits and cerebrovascular dysfunctions, and are at higher risk of developing dementia. Cognitive function in individuals with CHD has never been studied during acute aerobic exercise. Given the increasing popularity of training at high peak power output (PPO), its impact on cerebrovascular and cognitive functions in individuals with CHD should be further studied. MethodThirty-eight individuals with CHD and 16 healthy controls completed two exercise bouts at 30% and 70% of their individualized PPO on an ergocycle while performing a cognitive task including non-executive and executive conditions. Variations of oxy- deoxy-hemoglobin, and total hemoglobin concentrations were measured on left prefrontal cortex at both PPO using near-infrared spectroscopy. ResultsCognitive task performances were equivalent between groups at all intensity levels. Individuals with CHD exhibited larger variation of deoxyhemoglobin in the executive condition and larger variation in total hemoglobin concentration in all task conditions compared to healthy controls at 70% of PPO. ConclusionExercising at high intensity seems to have a larger impact on cerebral blood volume in CHD patients compared to healthy age-matched controls. Higher exercise intensity has negative impacts on cerebral blood volume variations during a cognitive task in CHD patients and could potentially lead to other neurocognitive dysfunctions. Other studies are needed to determine if a cognitive task administered during an exercise test could help identify individuals with CHD at higher risk of developing cognitive decline.

Ku-Band 70-/30-W-Class Internally Matched GaN Power Amplifiers With Low IMD3 Over a Wide Offset Frequency Range of Up To 400 MHz

This study describes the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ku</i> -band 70- and 30-W-class internally matched gallium nitride (GaN) power amplifiers (PAs) for multi-carrier satellite communications (SatComs). The GaN PAs maintain low third-order intermodulation distortion (IMD3) over a wide offset frequency range of up to 400 MHz, whereas in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ku</i> -band, one PA can deliver a high peak output power of approximately 70 W and the other PA, a peak output power of higher than 30 W. To realize a wide offset frequency operation, our proposed output-matching circuit includes three different types of difference-frequency short circuits, two of which are embedded into a tournament-shaped output-matching circuit inside the PA package and the rest is embedded into the drain bias feed placed outside the package. To verify the short-circuit design and its effectiveness, two different power classes (70 and 30 W), <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ku</i> -band GaN PAs, were designed and fabricated, and then, their output transfer characteristics focusing on IMD3 were measured. The measurements show that the 70-W-class GaN PA achieves a peak output power of 48.6 dBm while maintaining a linear output power of over 40 dBm and an IMD3 of less than −26 dBc over wide offset frequencies ranging from 1 to 400 MHz. The 30-W-class GaN PA maintains a linear output power of over 36.3 dBm and an IMD3 of less than −27 dBc over wide offset frequencies of up to approximately 600 MHz. To the best of the authors’ knowledge, these PAs have a record output power level over a wide frequency range of 1–400 MHz or higher under the condition of a low IMD3 of less than −25 dBc, compared to previously reported <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ku</i> -band GaN PAs used for multi-carrier SatComs.

Investigation on free-piston motion and power generation of a dual-piston air-driven expander linear generator

In this paper, an experimental test rig has been developed by utilising the free-piston linear generator (FPLG) principle of a dual-piston air-driven system. The mechanical energy of the FPLG is converted into electric power through a linear generator. The piston motion, root mean square (RMS) power output, operating frequency, system stability and the conversion efficiency of the FPLG at various inlet pressure and valve opening duration (VOD) are duly discussed in the paper. It is noticed that the piston displacement (stroke) is associated with the VOD and inlet pressure, which have the greatest effect on the FPLG motion characteristics. A long VOD leads to a high piston speed, causing high peak power output. However, the RMS power shows an approximately linear decline with the increase in VOD due to the free-piston dwelling for a certain time at the dead centre position before the exhaust process starts. The FPLG can be achieved a maximum RMS power of 120 W when the inlet pressure is 8 bar and VOD is 30 ms. When the inlet pressure changed from 8 bar to 5 bar, the FPLG operating frequency shows a similar trend and values because it is associated with the piston velocity and stroke. The FPLG Cycle-to-Cycle variation (COV) is low when the inlet pressure is high, and the system stability increases with decreases in VOD. As the VOD increases, the indicated efficiency and work to electrical efficiency increase, whereas the thermal to work efficiency decreases. The maximum indicated efficiency, work to electrical efficiency and thermal to work efficiency achieved are 59.9%, 14.7% and 14.6 %, respectively.

A High Peak Output Power and High Power Conversion Efficiency SIMIMO Converter Using Optimal on-Time Control and Hybrid Zero Current Switching for Energy Harvesting Systems in IoT Applications

This article proposes a single inductor multi-input multioutput (SIMIMO) converter with high peak output power and power conversion efficiency for energy harvesting systems in Internet of Things (IoT) applications. The proposed SIMIMO converter consists of inputs with four harvesters and a battery, and outputs with 1.8 V output, 3.3 V output, and a battery. The optimal on -time control method is proposed to optimally adjust the on time required to energize the inductor, thus increasing the peak output power to cover a wide distance range. In addition, the hybrid zero-current-switching (ZCS) method is proposed to adaptively calibrate the offset of the ZCS comparator, thus improving the power conversion efficiency. The proposed SIMIMO converter is fabricated using 0.18-μm standard bipolar-CMOS-DMOS (BCD) process technology with 1.8- and 5-V devices. The measurement results show that the peak output power is achieved to be 462 mW, and the peak power conversion efficiencies at 1.8 V output, 3.3 V output, and battery are 89.2%, 84.5%, and 86.4%, respectively. Moreover, the quiescent current of the power management controller, which controls the proposed converter, is achieved to be only 1.6 μA. Therefore, the proposed SIMIMO converter is suitable for energy harvesting systems in various IoT applications.

Retraining and Nutritional Strategy of an Endurance Master Athlete Following Hip Arthroplasty: A Case Study.

Retraining and resuming competition following surgery is challenging for athletes due to the prolonged period of reduced physical activity and subsequent alteration of body composition and physical performance. This is even more challenging for master athletes who endure the additional effect of aging. Within this context, the purpose of this study was to evaluate the feasibility and benefits that evidence-based nutritional and training recommendations could have on the time course of reconditioning and retraining following hip arthroplasty in an endurance master triathlete. During 38 weeks (from 6 weeks prior to surgery through to the return to competition in week 32), the athlete was provided with detailed training and nutritional recommendations. Dietary intake (via the remote food photographic method), body composition (via DXA), peak oxygen uptake (VO2peak), peak power output (PPO), cycling efficiency (GE), and energy availability (EA) were assessed 6 weeks pre- and 8, 12, 18, 21, and 25-weeks post-surgery. Training load was quantified (via TRIMP score and energy expenditure) daily during the retraining. Total body mass increased by 8.2 kg (attributable to a 3.5–4.6 kg increase in fat mass and lean mass, respectively) between week −6 and 8 despite a reduction in carbohydrate (CHO) intake post-surgery (<3.0 g/kg body mass/day). This was accompanied with a decrease in VO2peak, PPO, and GE due to a drop in training load. From week 7, the athlete resumed training and was advised to increase gradually CHO intake according to the demands of training. Eventually the athlete was able to return to competition in week 32 with a higher PPO, improved VO2peak, and GE. Throughout retraining, EA was maintained around 30 kcal/kg Lean Body Mass/day, protein intake was high (~2 g/kg/day) while CHO intake was periodized. Such dietary conditions allowed the athlete to maintain and even increase lean mass, which represents a major challenge with aging. Data reported in this study show, for the first time, the conditions required to recover and return to endurance competition following hip surgery.

The large piezoelectricity and high power density of a 3D-printed multilayer copolymer in a rugby ball-structured mechanical energy harvester

A 3D-printed multilayer copolymer rugby ball-structured energy harvester is prepared, and a high peak output power of 16.4 mW cm−2 is obtained.

Design of a Novel Piezoelectric Energy Harvester Based on Integrated Multistage Force Amplification Frame

This paper proposes a novel integrated multistage energy harvester to scavenge the mechanical energy from human footstep during walking. The device involves a four-stage force amplification using wedge mechanism, leverage mechanism, half-bridge mechanism, and bridge-type force amplifier. It is devised to magnify the input force exerted on a piezoelectric stack so as to enhance the power output. By fully exploiting the characteristics of the force amplification frame, the harvester also provides the function of position protection, which enables the bearing of large load and thereby protecting the piezoelectric stack. By this, the maximum displacement input is restricted to a certain range to ensure the walking comfort. A static analytical model of the energy harvester is established through the force analysis based on the stiffness matrix method. The main architectural parameters of the device are optimized by adopting a multiobjective genetic algorithm with ANSYS software. Moreover, a prototype is fabricated for experimental investigation. Experimental results show that the harvester exhibits a large force amplification ratio of 17.9 and high-peak power output of 50.8 mW across a matched resistor.

Effects of Load on Peak Power Output Fatigue During the Bench Throw.

Boffey, D, Sokmen, B, Sollanek, K, Boda, W, and Winter, S. Effects of load on peak power output fatigue during the bench throw. J Strength Cond Res 33(2): 355-359, 2019-The ability to create power is an important variable for athletic success. No study to date has compared peak power output (PPO) fatigue across multiple sets and with different loads with the bench throw. This study aimed to begin the process of establishing empirical upper-body power training guidelines for moderately strong athletes by determining how load (30, 45, and 60% 1 repetition maximum [1RM]) affects PPO (Watts) dropoff during 3 sets of 10 repetitions of the bench throw. Ten resistance-trained male volunteers ([mean ± SD]: age 20.58 ± 1.36 years, height 176.05 ± 9.09 cm, body mass 78.65 ± 9.93 kg, bench press 1RM 99.79 ± 18.52 kg) performed 3 sets of 10 repetitions of the bench throw with one of the 3 loads during 3 weekly sessions. A Humac 360 device collected concentric phase PPO data during each repetition. The data were analyzed using one-way (treatment) and 2-way (treatment × time) repeated-measures analysis of variance. A significant decrease in PPO was observed during repetitions 5-7 at 30%, 3-4 at 45%, and 2-3 at 60% 1RM. Based on the results of this study, coaches who want to maximize power should potentially keep sets of upper-body plyometrics within these repetition ranges. The authors recommend that moderately strong athletes perform the bench throw on a Smith machine at 45% or 60% 1RM to produce high PPO over multiple sets.

On-chip supercontinuum generation in nanostructured Ge11.5As24Se64.5 chalcogenide waveguides using Panda-ring resonator

The on-chip scale microring circuit is proposed to numerically investigate the supercontinuum (SC) generation of light power. The device is formed by the chalcogenide Panda-ring resonator with the nanoscale planar waveguide using Ge11.5As24Se64.5chalcogenide glass channel waveguide, air-clad and MgF2glass for lower cladding. The waveguide is designed to exhibit normal dispersion along with a low-energy pumped at 1.55 μm using a short pulse, which has the duration of 50 fs and peak power ranging from 1 W to 100 W. The numerical result obtained has shown a good-quality SC generation of both the spectral bandwidth and high output peak power. All SC spectral extended to more than 13 μm by cumulative Kerr nonlinearities. The obtained results can be useful for developing new experimental work in the important area of SC generation on compact chip broadband sources, which can be used in both infrared and radio wave applications.

Relationship between skeletal muscle contractile properties and power production capacity in female Olympic rugby players

This study aimed to determine which contractile properties measured by tensiomyography (TMG) could better differentiate athletes with high- and low-power values, as well as to analyse the relationship between contractile properties and power production capacity. The contractile properties of the vastus medialis (VM), rectus femoris (RF) and vastus lateralis (VL) of an Olympic women’s Rugby Sevens team (n = 14) were analysed before a Wingate test in which their peak power output (PPO) was determined. Athletes were then divided into a high-power (HP) and a low-power (LP) group. HP presented an almost certainly higher PPO (9.8 ± 0.3 vs. 8.9 ± 0.4 W kg−1, ES = 3.00) than LP, as well as a very likely lower radial displacement (3.39 ± 1.16 vs. 5.65 ± 1.50 mm, ES = 1.68) and velocity of deformation (0.08 ± 0.02 vs. 0.13 ± 0.03 mm ms−1, ES = 1.87) of the VL. A likely lower time of delay was observed in HP for all analysed muscles (ES > 0.60). PPO was very largely related to the radial displacement (r = −0.75, 90% CI = −0.90 to −0.44) and velocity of deformation (r = −0.70, 90% CI = −0.87 to −0.34) of the VL. A large correlation was found between PPO and the time of delay of the VL (r = −0.61, 90% CI = −0.84 to −0.22). No correlations were found for the contractile properties of RF or VM. These results highlight the importance of VL contractile properties (but not so much those of RF and VM) for maximal power production and suggest TMG as a practical technique for its evaluation.

Sprint performance and propulsion asymmetries on an ergometer in trained high- and low-point wheelchair rugby players.

The purpose of this study was to examine the propulsion asymmetries of wheelchair athletes while sprinting on an instrumented, dual-roller ergometer system. Eighteen experienced wheelchair rugby players (8 low point (LP) (class ≤1.5) and 10 high point (HP) (class ≥2.0)) performed a 15-second sprint in their sports wheelchair on the instrumented ergometer. Asymmetry was defined as the difference in distance and power output (PO) between left and right sides when the best side reached 28m. Propulsion techniques were quantified based on torque and velocity data. HP players covered an average 3m further than the LP players (P=.002) and achieved faster sprint times than LP players (6.95±0.89 vs 8.03±0.68seconds, P=.005) and at the time the best player finished (5.96seconds). Higher peak POs (667±108 vs 357±78W, P=.0001) and greater peak speeds that were also evident were for HP players (4.80±0.71 vs 4.09±0.45m/s, P=.011). Greater asymmetries were found in HP players for distance (1.86±1.43 vs 0.70±0.65m, P=.016), absolute peak PO (P=.049), and speed (0.35±0.25 vs 0.11±0.10m/s, P=.009). Although HP players had faster sprint times over 28m (achieved by a higher PO), high standard deviations show the heterogeneity within the two groups (eg, some LP players were better than HP players). Quantification of asymmetries is important not only for classifiers but also for sports practitioners wishing to improve performance as they could be addressed through training and/or wheelchair configuration.