A security proof of continuous-variable QKD using three coherent states

We introduce a ternary quantum key distribution (QKD) protocol and asymptotic security proof based on three coherent states and homodyne detection. Previous work had considered the binary case of two coherent states and here we nontrivially extend this to three. Our motivation is to leverage the practical benefits of both discrete and continuous (Gaussian) encoding schemes creating a best-of-both-worlds approach; namely, the postprocessing of discrete encodings and the hardware benefits of continuous ones. We present a thorough and detailed security proof in the limit of infinite signal states which allows us to lower bound the secret key rate. We calculate this is in the context of collective eavesdropping attacks and reverse reconciliation postprocessing. Finally, we compare the ternary coherent state protocol to other well-known QKD schemes (and fundamental repeaterless limits) in terms of secret key rates and loss.Comment: Close to the published versio

Comparison of two Borg exertion scales for monitoring exercise intensity in able-bodied participants, and those with paraplegia and tetraplegia

Study design Cross-sectional cohort study. Objectives To compare ratings of perceived exertion (RPE) on Borg's 6-20 RPE scale and Category Ratio 10 (CR10) in able-bodied (AB) participants during upper and lower body exercise, and recreationally active participants with paraplegia (PARA) and athletes with tetraplegia (TETRA) during upper body exercise only. Setting University and rehabilitation centre-based laboratories in UK and Netherlands. Methods Twenty-four participants were equally split between AB, PARA, and TETRA. AB performed maximal tests using cycle (AB-CYC) and handcycle (AB-HC) ergometry. PARA and TETRA performed maximal handcycle and wheelchair propulsion tests, respectively. Oxygen uptake (V?O-2) and blood lactate concentration were monitored throughout. RPE was rated each stage on Borg's RPE scale and CR10. Thresholds were identified according to log-V?O-2 plotted against log-blood lactate (LT1), and 1.5 mmol L-1 greater than LT1 (LT2). Results RPE from both scales were best fit against each other using a quadratic model, with high goodness of fit between scales that was independent of exercise mode and participant group (range R-2: 0.965-0.970, P < 0.005). Though percentage peak V?O-2 was significantly greater in TETRA (P < 0.005), there was no difference in RPE at LT1 or LT2 between groups on Borg's RPE scale or CR10. Conclusion Strong association between Borg's RPE scale and CR10 suggests they can be used interchangeably. RPE at lactate thresholds were independent of mode of exercise and level of spinal cord injury. However, inter-individual variation precludes from making firm recommendations about using RPE for prescribing homogenous exercise intensity

Managing shoulder pain in manual wheelchair users:a scoping review of conservative treatment interventions

Objective:To review the literature that has explored conservative treatments for the management of shoulder pain in manual wheelchair users.Methods:Five databases were systematically searched in february 2020 for terms related to shoulder pain and manual wheelchair use. Articles were screened and included if they investigated the conservative treatment of shoulder pain in wheelchair users. Participants’ physical characteristics, experimental design and primary and secondary outcome measures were extracted from studies. Studies were grouped according to treatment type to identify gaps in the literature and guide future research.Results:The initial search identified 407 articles, of which 21 studies met the inclusion criteria. Exercise-based treatment interventions were most prevalent (n = 12). A variety of exercise modalities were employed such as strengthening and stretching (n = 7), ergometer training (n = 3), Pilates classes (n = 1) and functional electrical stimulation (n = 1). Only three studies supplemented exercise with an additional treatment type. The Wheelchair Users Shoulder Pain Index was used by 18 studies as the primary measure of shoulder pain. Only seven of these included an objective measure of shoulder function. Participant characteristics varied among studies, and physical activity levels were frequently not reported.Conclusions:Despite the high prevalence of shoulder pain in manual wheelchair users, the number of studies to have explored conservative treatment types is low. Exercise is the most commonly used treatment, which is encouraging as physical inactivity can exacerbate other health conditions. Few studies have adopted interdisciplinary treatment strategies or included objective secondary measures to better understand the mechanisms of pain.<br

Effect of abdominal binding on respiratory mechanics during exercise in athletes with cervical spinal cord injury

West CR, Goosey-Tolfrey VL, Campbell IG, Romer LM. Effect of abdominal binding on respiratory mechanics during exercise in athletes with cervical spinal cord injury. J Appl Physiol 117: 36–45, 2014. First published May 22, 2014; doi:10.1152/japplphysiol.00218.2014.—We asked whether elastic binding of the abdomen influences respiratory mechanics during wheelchair propulsion in athletes with cervical spinal cord injury (SCI). Eight Paralympic wheelchair rugby players with motor-complete SCI (C5-C7) performed submaximal and maximal incremental exercise tests on a treadmill, both with and without abdominal binding. Measurements included pulmonary function, pressure-derived indices of respiratory mechanics, operating lung volumes, tidal flow-volume data, gas exchange, blood lactate, and symptoms. Residual volume and functional residual capacity were reduced with binding (77 18 and 81 11% of unbound, P 0.05), vital capacity was increased (114 9%, P 0.05), whereas total lung capacity was relatively well preserved (99 5%). During exercise, binding introduced a passive increase in transdiaphragmatic pressure, due primarily to an increase in gastric pressure. Active pressures during inspiration were similar across conditions. A sudden, sustained rise in operating lung volumes was evident in the unbound condition, and these volumes were shifted downward with binding. Expiratory flow limitation did not occur in any subject and there was substantial reserve to increase flow and volume in both conditions. V ˙ O2 was elevated with binding during the final stages of exercise (8 –12%, P 0.05), whereas blood lactate concentration was reduced (16 –19%, P 0.05). V ˙ O2/heart rate slopes were less steep with binding (62 35 vs. 47 24 ml/beat, P 0.05). Ventilation, symptoms, and work rates were similar across conditions. The results suggest that abdominal binding shifts tidal breathing to lower lung volumes without influencing flow limitation, symptoms, or exercise tolerance. Changes in respiratory mechanics with binding may benefit O2 transport capacity by an improvement in central circulatory function.This article has been made available through the Brunel Open Access Publishing Fund

Criterion Validity of a Field-Based Assessment of Aerobic Capacity in Wheelchair Rugby Athletes

Purpose: To confirm whether peak aerobic capacity determined during laboratory testing could be replicated during an on-court field-based test in wheelchair rugby (WR) players. Methods: Sixteen WR players performed an incremental speed-based peak oxygen uptake (V̇O2peak) test on a motorised treadmill (TM) and completed a Multi-stage Fitness Test (MFT) on a basketball court in a counter-balanced order while spirometric data were recorded. A paired t-test was performed to check for systematic error between tests. A Bland-Altman plot for V̇O2peak illustrated the agreement between the TM and MFT results and how this related to the boundaries of practical equivalence. Results: No significant differences between mean V̇O2peak were reported (TM:1.85±0.63 vs. MFT: 1.81±0.63 L.min-1; p=0.33). Bland-Altman plot for V̇O2peak suggests that the mean values are in good agreement at the group level; i.e., the exact 95% confidence limits for the ratio systematic error (0.95 to 1.02) are within the boundaries of practical equivalence (0.88 to 1.13) showing the group average TM and MFT values are interchangeable. However, consideration of the data at the level of the individual athlete suggests the TM and MFT results were not interchangeable because the 95% ratio limits of agreement either coincide with the boundaries of practical equivalence (upper limit) or fall outside (lower limit). Conclusions: Results suggest that the MFT provides a suitable test at a group level with this cohort of WR players for the assessment of V̇O2peak (range 0.97 – 3.64 L∙min-1), yet caution is noted for interchangeable use of values between tests for individual players

Releasing The Anti-inflammatory Potential of Paralysed Skeletal Muscle: The Circulating Cytokine Response to Voluntary Upper-limb Exercise With/Without The Addition of Functional Electrical Stimulation (FES)-evoked Lower-limb Contractions

Skeletal muscle is a rich store of inflammatory mediating ‘myokines’. Following release from contracting muscle, the myokine interleukin-6 (IL-6) promotes a circulating anti-inflammatory environment associated with a reduced risk of cardiovascular disease (CVD). The metabolic and functional consequences of lower-limb paralysis, including the gain in relative adiposity and physical inactivity, result in a high prevalence of CVD in individuals with a spinal cord injury (SCI). However, the magnitude of any contraction-induced myokine response in this population may be limited by the small active muscle mass of the upper-limb. The combination of voluntary, upper-limb exercise and involuntary, functional electrical stimulation (FES)-evoked lower-limb cycling termed ‘hybrid’ exercise, may augment the acute myokine response by activating a greater volume of muscle mass than upper-limb exercise alone. Five community-based individuals with motor complete, thoracic SCI (Age=44±15 years; Body mass=66.6±14.3 kg) and at least 3 months FES-evoked cycling experience volunteered to participate. On separate occasions, each participant performed 30 min of voluntary upper-limb, hand cycling exercise with (HYBRID) and without (ARM only) the addition of FES-evoked lower-limb cycling at a fixed workload. Blood samples were collected at rest, immediately post-exercise, and 1 and 2 h post-exercise. Plasma concentrations of IL-6, IL-10 and IL-1ra were subsequently determined by enzyme linked immunoassay. Estimated energy expenditure was significantly higher in HYBRID (154±25 kcal) than ARM (132±21 kcal) (P=0.01; ES=0.90). Plasma IL-6 concentrations were significantly elevated following HYBRID, with values 1 h and 2 h post-exercise significantly higher than rest and immediately post-exercise (P\u3c0.04). A small (~50%) non-significant increase in IL-6 was present 1 h and 2 h post-exercise following ARM, however concentrations were significantly higher in HYBRID than ARM at the same time points (P\u3c0.02). Plasma IL-10 concentrations were unaffected by exercise in ARM. Although not attaining statistical significance, there was a tendency for IL-10 concentrations to rise in HYBRID, with an 85% increase in IL-10 concentrations at 2 h post exercise. Plasma IL-1ra was unaffected by exercise in both trials. Initial findings suggest paralysed skeletal muscle releases the myokine IL-6 in response to electrically evoked contractions. Further, voluntary upper-limb exercise combined with involuntary lower-limb FES-evoked exercise had the tendency to elevate plasma concentrations of the anti-inflammatory cytokine IL-10; this effect was not present when performing arm exercise alone. Hybrid exercise may offer a method of maximising the anti-inflammatory potential of acute exercise in individuals with a SCI. The current findings require verification in a larger cohort

The validity and reliability of a novel indoor player tracking system for use within wheelchair court sports

The aim of the current study was to investigate the validity and reliability of a radio- frequency based system for accurately tracking athlete movement within the wheelchair court sports. Four wheelchair specific tests were devised to assess the system during i) static measurements ii) incremental fixed speeds iii) peak speeds, and iv) multi-directional movements. During each test, three sampling frequencies (4, 8 & 16 Hz) were compared to a criterion method for distance, mean and peak speeds. Absolute static error remained between 0.19-0.32 m across the session. Distance values (test ii) showed greatest relative error in 4 Hz tags (1.3%), with significantly lower errors seen in higher frequency tags (< 1.0%). Relative peak speed errors of < 2.0% (test iii) were revealed across all sampling frequencies in relation to the criterion (4.00 ± 0.09 m·sˉ¹). Results showed 8 and 16 Hz sampling frequencies displayed the closest to criterion values, whilst intra-tag reliability never exceeded 2.0% coefficient of variation (% CV) during peak speed detection. Minimal relative distance errors (< 0.2%) were also seen across sampling frequencies (test iv). To conclude, the indoor tracking system is deemed an acceptable tool for tracking wheelchair court match-play using a tag frequency of 8 or 16 Hz

Alterations in shoulder kinematics are associated with shoulder pain during wheelchair propulsion sprints

The study purpose was to examine the biomechanical characteristics of sports wheelchair propulsion and determine biomechanical associations with shoulder pain in wheelchair athletes. Twenty wheelchair court-sport athletes (age: 32 +/- 11 years old) performed one submaximal propulsion trial in their sports-specific wheelchair at 1.67 m/s for 3 min and two 10 s sprints on a dual-roller ergometer. The Performance Corrected Wheelchair User's Shoulder Pain Index (PC-WUSPI) assessed shoulder pain. During the acceleration phase of wheelchair sprinting, participants propelled with significantly longer push times, larger forces, and thorax flexion range of motion (ROM) than both the maximal velocity phase of sprinting and submaximal propulsion. Participants displayed significantly greater peak glenohumeral abduction and scapular internal rotation during the acceleration phase (20 +/- 9 degrees and 45 +/- 7 degrees) and maximal velocity phase (14 +/- 4 degrees and 44 +/- 7 degrees) of sprinting, compared to submaximal propulsion (12 +/- 6 degrees and 39 +/- 8 degrees). Greater shoulder pain severity was associated with larger glenohumeral abduction ROM (r = 0.59, p = 0.007) and scapular internal rotation ROM (r = 0.53, p = 0.017) during the acceleration phase of wheelchair sprinting, but with lower peak glenohumeral flexion (r = -0.49, p = 0.030), peak abduction (r = -0.48, p = 0.034), and abduction ROM (r = -0.44, p = 0.049) during the maximal velocity phase. Biomechanical characteristics of wheelchair sprinting suggest this activity imposes greater mechanical stress than submaximal propulsion. Kinematic associations with shoulder pain during acceleration are in shoulder orientations linked to a reduced subacromial space, potentially increasing tissue stress

The longitudinal relationship between shoulder pain and altered wheelchair propulsion biomechanics of manual wheelchair users

The purpose of this study was to investigate the longitudinal association between within-subject changes in shoulder pain and alterations in wheelchair propulsion biomechanics in manual wheelchair users. Eighteen (age 33 ± 11 years) manual wheelchair users propelled their own daily living wheelchair at 1.11 m.s-1 for three minutes on a dual-roller ergometer during two laboratory visits (T1 and T2) between 4 and 6 months apart. Shoulder pain was assessed using the Performance Corrected Wheelchair User's Shoulder Pain Index (PC-WUSPI). Between visits mean PC-WUSPI scores increased by 5.4 points and varied from - 13.5 to + 20.9 points. Of the eighteen participants, nine (50%) experienced increased shoulder pain, seven (39%) no change in pain, and two (11%) decreased pain. Increasing shoulder pain severity correlated with increased contact angle (r = 0.59, P = 0.010), thorax range of motion (r = 0.60, P = 0.009) and kinetic and kinematic variability. Additionally, increasing shoulder pain was associated with reductions in peak torque (r = -0.56, P = 0.016), peak glenohumeral abduction (r = -0.69, P = 0.002), peak scapular downward rotation (r = -0.68, P = 0.002), and range of motion in glenohumeral flexion/extension and scapular angles. Group comparisons revealed that these biomechanical alterations were exhibited by individuals who experienced increased shoulder pain, whereas, propulsion biomechanics of those with no change/decreased pain remained unaltered. These findings indicate that wheelchair users exhibit a protective short-term wheelchair propulsion biomechanical response to increases in shoulder pain which may temporarily help maintain functional independence

Scapular kinematic variability during wheelchair propulsion is associated with shoulder pain in wheelchair users

The purpose of this study was to investigate whether wheelchair propulsion biomechanics differ between individuals with different magnitudes of shoulder pain. Forty (age 36 11 years) manual wheelchair users propelled their own daily living wheelchair at 1.11 m.s(-1) for three minutes on a dual-roller ergometer. Shoulder pain was evaluated using the Performance Corrected Wheelchair User's Shoulder Pain Index (PC-WUSPI). Correlation analyses between spatio-temporal, kinetic and upper limb kinematic variables during wheelchair propulsion and PC-WUSPI scores were assessed. Furthermore, kinematic differences between wheelchair users with no or mild shoulder pain (n = 33) and moderate pain (n = 7) were investigated using statistical parametric mapping. Participant mean PC-WUSPI scores were 20.3 +/- 26.3 points and varied from zero up to 104 points. No significant correlations were observed between kinetic or spatio-temporal parameters of wheelchair propulsion and shoulder pain. However, lower inter-cycle variability of scapular internal/external rotation was associated with greater levels of shoulder pain (r = 0.35, P = 0.03). Wheelchair users with moderate pain displayed significantly lower scapular kinematic variability compared to those with mild or no pain between 17 and 51% of the push phase for internal rotation, between 31-42% and 77-100% of the push phase for downward rotation and between 28-36% and 53-65% of the push phase for posterior tilt. Lower scapular variability displayed by wheelchair users with moderate shoulder pain may reflect a more uniform distribution of repeated subacromial tissue stress imposed by propulsion. This suggests that lower scapular kinematic variability during propulsion may contribute towards the development of chronic shoulder pain. (C) 2020 Elsevier Ltd. All rights reserved