Standing Research Articles

Uninterrupted prolonged sitting and arterial stiffness: moderating effect of prior aerobic exercise in physically active adults.

Prolonged sitting acutely increases arterial stiffness, with interruption strategies only providing limited success in offsetting these rises. Acute aerobic exercise is a potent stimulus to decrease arterial stiffness. However, limited information exists on the effectiveness of acute exercise to maintain arterial stiffness when performed prior to prolonged sitting, particularly within physically active individuals. Using a randomized crossover design, 22 young, active individuals (50% female) performed two conditions 30min of walking at 55-65% of heart rate reserve (EX) and 30min of standing (STAND) followed by 2.5-h of sitting. Brachial-femoral (bfPWV) and femoral-ankle pulse wave velocity (faPWV) were assessed at Baseline, post-exercise and pre-sitting (Pre), and post-sitting (Post) as estimates of central and peripheral arterial stiffness, respectively. For bfPWV, no interaction, condition, or time effects were observed. For faPWV, an interaction was present (p < 0.001); compared to Baseline, there was a 6.1% decrease for EX (- 0.4m/s, p < 0.001) and a 4.6% increase for STAND (0.3m/s, p = 0.016) for STAND such that there was an 11.3% difference between conditions at Pre (0.7m/s, p < 0.001). From Pre to Post, EX then increased by 11.7% (0.9m/s p < 0.001) while STAND remained unchanged, resulting in no difference between conditions (0.1m/s, p = 0.569). While aerobic exercise resulted in a significant decrease in faPWV prior to sitting, the prior exercise bout did not confer a protective effect against the deleterious effects of uninterrupted sitting. Future work should investigate the combined effect of prior exercise and sitting interruption strategies on markers of arterial stiffness.

Comparing remote and face-to-face assessments of physical performance in older adults: A reliability study

IntroductionOlder people often experience a decline in their physical performance. Tests have been approved to evaluate this performance in person. Yet, the constraints associated with in-person assessments (e.g. lack of medical facilities, pandemic lockdown, and contagion risk) are making us contemplate setting up assessments remotely. ObjectivesTo determine whether remote physical performance measurements of older adults are reliable and valid compared to face-to-face measurements. MethodsForty-five subjects aged 65 and over completed the normal/fast speed test (NWT/FWT), the unipodal balance test (UBT), the normal/fast timed up and go test (NTUG/FTUG), the 5 and 10 rep sit to stand test (5STS and 10STS), the 30 sec chair stand (30CS), the 2 minute step test (2MST) and the flexibility before standing (SAD) once face-to-face and twice remotely, by two different observers. The intraclass correlation coefficients (ICC), the standard errors of measurement (SEM%) and minimum detectable changes (MDC%) were calculated for both intra- and inter-observer conditions, to assess the relative and the absolute reliability. An ICC value exceeding 0.90 indicates a very high reliability, while an ICC between 0.70 and 0.89 signifies a high reliability. In clinical practice, a SEM % of less than 10% is considered acceptable. A smaller MDC % indicates a measurement that is more sensitive to detecting changes. ResultsIntra-observer relative reliability was very high (ICC>0.9) for the UBT, NWT, NTUG, FTUG, 5STS, 10STS, 30CS and the SAD; and high (ICC>0.7) for the 2MST and FWS. SEM% values ranged from 0% to 24.03% and MDC from 0% to 9.93%. Inter-observer relative reliability was considered very high (ICC>0.9) for all tests. SEM% values ranged from 0% to 17.68% and MDC from 0% to 7.32%. ConclusionOur findings demonstrate that remote assessments exhibited consistently high to very high levels of intra- and inter-observer relative reliability when compared to face-to-face assessments. Additionally, certain remote evaluations showed acceptable absolute reliability, making them viable alternatives for healthcare professionals when in-person assessments are not feasible in clinical practice.

The degree of engagement of cardiac and sympathetic arms of the baroreflex does not depend on the absolute value and sign of arterial pressure variations

Objective. The percentages of cardiac and sympathetic baroreflex patterns detected via baroreflex sequence (SEQ) technique from spontaneous variability of heart period (HP) and systolic arterial pressure (SAP) and of muscle nerve sympathetic activity (MSNA) burst rate and diastolic arterial pressure (DAP) are utilized to assess the level of the baroreflex engagement. The cardiac baroreflex patterns can be distinguished in those featuring both HP and SAP increases (cSEQ++) and decreases (cSEQ−−), while the sympathetic baroreflex patterns in those featuring a MSNA burst rate decrease and a DAP increase (sSEQ+−) and vice versa (sSEQ−+). The present study aims to assess the modifications of the involvement of the cardiac and sympathetic arms of the baroreflex with age and postural stimulus intensity. Approach. We monitored the percentages of cSEQ++ (%cSEQ++) and cSEQ−− (%cSEQ−−) in 100 healthy subjects (age: 21–70 years, 54 males, 46 females), divided into five sex-balanced groups consisting of 20 subjects in each decade at rest in supine position and during active standing (STAND). We evaluated %cSEQ++, %cSEQ−−, and the percentages of sSEQ+− (%sSEQ+−) and sSEQ−+ (%sSEQ−+) in 12 young healthy subjects (age 23 ± 2 years, 3 females, 9 males) undergoing incremental head-up tilt. Main results. We found that: (i) %cSEQ++ and %cSEQ−− decreased with age and increased with STAND and postural stimulus intensity; (ii) %sSEQ+− and %sSEQ−+ augmented with postural challenge magnitude; (iii) the level of cardiac and sympathetic baroreflex engagement did not depend on either the absolute value of arterial pressure or the direction of its changes. Significance. This study stresses the limited ability of the cardiac and sympathetic arms of the baroreflex in controlling absolute arterial pressure values and the equivalent ability of both positive and negative arterial pressure changes in soliciting them.

Effects of Increased Standing and Light-Intensity Physical Activity to Improve Postprandial Glucose in Sedentary Office Workers: Protocol for a Randomized Crossover Trial.

Prolonged bouts of sedentary time, independent from the time spent in engaging in physical activity, significantly increases cardiometabolic risk. Nonetheless, the modern workforce spends large, uninterrupted portions of the day seated at a desk. Previous research suggests-via improved cardiometabolic biomarkers-that this risk might be attenuated by simply disrupting sedentary time with brief breaks of standing or moving. However, this evidence is derived from acute, highly controlled laboratory experiments and thus has low external validity. This study aims to investigate if similar or prolonged cardiometabolic changes are observed after a prolonged (2-week) practice of increased brief standing and moving behaviors in real-world office settings. This randomized crossover trial, called the WorkWell Study, will compare the efficacy of two 2-week pilot intervention conditions designed to interrupt sitting time in sedentary office workers (N=15) to a control condition. The intervention conditions use a novel smartphone app to deliver real-time prompts to increase standing (STAND) or moving (MOVE) by an additional 6 minutes each hour during work. Our primary aim is to assess intervention-associated improvements to daily postprandial glucose using continuous glucose monitors. Our secondary aim is to determine whether the interventions successfully evoke substantive positional changes and light-intensity physical activity (LPA). Other outcomes include the feasibility and acceptability of the intervention conditions, fasting blood glucose concentration, femoral artery flow-mediated dilation (f-FMD), and systolic and diastolic blood pressure. The trial is ongoing at the time of submission. This study is a novel, randomized crossover trial designed to extend a laboratory-based controlled study design into the free-living environment. By using digital health technologies to monitor and prompt participants in real time, we will be able to rigorously test the effects of breaking up sedentary behavior over a longer period of time than is seen in traditional laboratory-based studies. Our innovative approach will leverage the strengths of highly controlled laboratory and free-living experiments to achieve maximal internal and external validity. The research team's multidisciplinary expertise allows for a broad range of biological measures to be sampled, providing robust results that will extend knowledge of both the acute and chronic real-life effects of increased standing and LPA in sedentary office workers. The WorkWell Study uses a rigorous transdisciplinary protocol that will contribute to a more comprehensive picture of the beneficial effects of breaking up sitting behavior. ClinicalTrials.gov NCT04269070; https://clinicaltrials.gov/study/NCT04269070. DERR1-10.2196/45133.

Characterization of Multiple Regimes of Cardiorespiratory Phase Synchronization in Athletes Undergoing Inspiratory Muscle Training.

Cardiorespiratory phase synchronization (CRPS) is defined as the stable occurrence of n heartbeats within m respiratory cycles according to the n:m phase locking ratio (PLR). Since CRPS is an intermittent phenomenon where different phase synchronization regimes and epochs of phase unlocking can alternate within the same recording, an index of CRPS ideally should assess all potential PLRs present in the recording. However, traditional approaches compute the synchronization index (SYNC%) over a single n:m PLR, namely the one that maximizes CRPS. In the present work, we tested a synchronization index assessing the total percentage of heartbeats coupled to the inspiratory onset regardless of phase locking regimes (SYNC%sum) and we compared its efficacy to the more traditional SYNC%. Analysis was carried out in a cohort of 25 male amateur cyclists (age: 20-40 yrs) undergoing inspiratory muscle training (IMT) at different intensities. CRPS was assessed before and after the IMT protocol, during an experimental condition known to modify CRPS, namely active standing (STAND). We found that after a moderate intensity IMT at 60% of the maximal inspiratory pressure, SYNC%sum could detect the decrease in CRPS following STAND. This result was not visible using the more traditional SYNC%. Therefore, we stress the significant presence of different phase locking regimes in athletes and the importance of accounting for multiple PLRs in CRPS analysis.Clinical Relevance- Multiple phase locking regimes contribute significantly to cardiorespiratory control in amateur cyclists especially after inspiratory muscle training of moderate intensity.

Evaluation of cardiovascular and cerebrovascular control mechanisms in postural orthostatic tachycardia syndrome via conditional transfer entropy: the impact of the respiratory signal type

Objective. Closed loop cardiovascular (CV) and cerebrovascular (CBV) variability interactions are assessed via transfer entropy (TE) from systolic arterial pressure (SAP) to heart period (HP) and vice versa and from mean arterial pressure (MAP) to mean cerebral blood velocity (MCBv) and vice versa. This analysis is exploited to assess the efficiency of baroreflex and cerebral autoregulation. This study aims at characterizing CV and CBV controls in postural orthostatic tachycardiac syndrome (POTS) subjects experiencing exaggerated sympathetic response during orthostatic challenge via unconditional TE and TE conditioned on respiratory activity (R). Approach. In 18 healthy controls (age: 28 ± 13 yrs; 5 males, 13 females) and 15 POTS individuals (age: 29 ± 11 yrs; 3 males, 12 females) we acquired beat-to-beat variability of HP, SAP, MAP and MCBv and two R signals, namely respiratory chest movement (RCM) and capnogram (CAP). Recordings were made at sitting rest and during active standing (STAND). TE was computed via vector autoregressive approach. Main results. We found that: (i) when assessing CV interactions, the increase of the TE from SAP to HP during STAND, indicating baroreflex activation, is detected solely when conditioning on RCM; (ii) when assessing CBV interactions, the impact of R on the TE computation is negligible; (iii) POTS shows baroreflex impairment during STAND; (iv) POTS exhibits a normal CBV response to STAND. Significance. TE is useful for detecting the impairment of specific regulatory mechanisms in POTS. Moreover, using different R signals highlights the sensitivity of CV and CBV controls to specific R aspects.

Novel Feature Extraction and Locomotion Mode Classification Using Intelligent Lower-Limb Prosthesis

Intelligent lower-limb prosthesis appears in the public view due to its attractive and potential functions, which can help amputees restore mobility and return to normal life. To realize the natural transition of locomotion modes, locomotion mode classification is the top priority. There are mainly five steady-state and periodic motions, including LW (level walking), SA (stair ascent), SD (stair descent), RA (ramp ascent), and RD (ramp descent), while ST (standing) can also be regarded as one locomotion mode (at the start or end of walking). This paper mainly proposes four novel features, including TPDS (thigh phase diagram shape), KAT (knee angle trajectory), CPO (center position offset) and GRFPV (ground reaction force peak value) and designs ST classifier and artificial neural network (ANN) classifier by using a user-dependent dataset to classify six locomotion modes. Gaussian distributions are applied in those features to simulate the uncertainty and change of human gaits. An angular velocity threshold and GRFPV feature are used in the ST classifier, and the artificial neural network (ANN) classifier explores the mapping relation between our features and the locomotion modes. The results show that the proposed method can reach a high accuracy of 99.16% ± 0.38%. The proposed method can provide accurate motion intent of amputees to the controller and greatly improve the safety performance of intelligent lower-limb prostheses. The simple structure of ANN applied in this paper makes adaptive online learning algorithms possible in the future.

Comparison of machine learning and deep learning-based methods for locomotion mode recognition using a single inertial measurement unit.

Locomotion mode recognition provides the prosthesis control with the information on when to switch between different walking modes, whereas the gait phase detection indicates where we are in the gait cycle. But powered prostheses often implement a different control strategy for each locomotion mode to improve the functionality of the prosthesis. Existing studies employed several classical machine learning methods for locomotion mode recognition. However, these methods were less effective for data with complex decision boundaries and resulted in misclassifications of motion recognition. Deep learning-based methods potentially resolve these limitations as it is a special type of machine learning method with more sophistication. Therefore, this study evaluated three deep learning-based models for locomotion mode recognition, namely recurrent neural network (RNN), long short-term memory (LSTM) neural network, and convolutional neural network (CNN), and compared the recognition performance of deep learning models to the machine learning model with random forest classifier (RFC). The models are trained from data of one inertial measurement unit (IMU) placed on the lower shanks of four able-bodied subjects to perform four walking modes, including level ground walking (LW), standing (ST), and stair ascent/stair descent (SA/SD). The results indicated that CNN and LSTM models outperformed other models, and these models were promising for applying locomotion mode recognition in real-time for robotic prostheses.

Directional sensitivity of dynamic cerebral autoregulation during spontaneous fluctuations in arterial blood pressure at rest

Directional sensitivity, the more efficient response of cerebral autoregulation to increases, compared to decreases, in mean arterial pressure (MAP), has been demonstrated with repeated squat-stand maneuvers (SSM). In 43 healthy subjects (26 male, 23.1 ± 4.2 years old), five min. recordings of cerebral blood velocity (bilateral Doppler ultrasound), MAP (Finometer), end-tidal CO2 (capnograph), and heart rate (ECG) were obtained during sitting (SIT), standing (STA) and SSM. A new analytical procedure, based on autoregressive-moving average models, allowed distinct estimates of the autoregulation index (ARI) by separating the MAP signal into its positive (MAP+D) and negative (MAP−D) derivatives. ARI+D was higher than ARI−D (p < 0.0001), SIT: 5.61 ± 1.58 vs 4.31 ± 2.16; STA: 5.70 ± 1.24 vs 4.63 ± 1.92; SSM: 4.70 ± 1.11 vs 3.31 ± 1.53, but the difference ARI+D–ARI−D was not influenced by the condition. A bootstrap procedure determined the critical number of subjects needed to identify a significant difference between ARI+D and ARI−D, corresponding to 24, 37 and 38 subjects, respectively, for SSM, STA and SIT. Further investigations are needed on the influences of sex, aging and other phenotypical characteristics on the phenomenon of directional sensitivity of dynamic autoregulation.

A Longitudinal Study of Quantitative Muscle Strength and Functional Motor Ability in Ambulatory Boys with Duchenne Muscular Dystrophy.

Duchenne muscular dystrophy (DMD) is an X-linked recessive genetic disorder, that is characterized by progressive muscle degeneration and loss of ambulation between 7-13 years of age. Novel pharmacological agents targeting the genetic defects and disease mechanisms are becoming available; however, corticosteroid (CS) therapy remains the standard of care. The purpose of this longitudinal study was to elucidate the effect of CS therapy on the rate of muscle strength and gross motor skill decline in boys with DMD and assess the sensitivity of selected outcome measures. Eighty-four ambulatory boys with DMD (49-180 months), 70 on CS, 14 corticosteroid naïve (NCS), participated in this 8-year multi-site study. Outcomes included; isokinetic dynamometry, the Standing (STD) and Walking/Running/jumping (WRJ) dimensions of the Gross Motor Function Measure (GMFM), and Timed Function Tests (TFTs). Nonlinear mixed modeling procedures determined the rate of change with age and the influence of steroids. Despite CS therapy the rate of decline in strength with age was significant in all muscle groups assessed. CS therapy significantly slowed decline in knee extensor strength, as the NCS group declined at 3x the rate of the CS group. Concurrently, WRJ skills declined in the NCS group at twice the rate of the CS group. 4-stair climb and 10 meter walk/run performance was superior in the boys on CS therapy. CS therapy slowed the rate of muscle strength decline and afforded longer retention of select gross motor skills in boys on CS compared to boys who were NCS. Isokinetic dynamometry, Walk/Run/Jump skills, and select TFTs may prove informative in assessing the efficacy of new therapeutics in ambulatory boys with DMD.

Comparison of Race Time-Differences Between and Within Para and Able-Bodied Cross-Country Skiers.

PurposeTo compare differences in race time (i.e., the average percent difference in race time for each skier compared to the winner, RTdiffs) between female and male Para and able-bodied (AB) skiers, and to examine whether RTdiffs change across seasons.MethodsRace data from World Cups (WCs), World Championships (WCHs), and Paralympic/Olympic Winter Games (PWG/OWGs) of the 2011–2020 seasons was extracted from the website of the International Paralympic Committee and the International Ski Federation. All individual distance races for female and male visually impaired standing (VI), physically impaired sitting (SIT) and standing (STAND), and AB skiers with ≥10 competitors were included in the analyses. We investigated the main effect of skiing groups (i.e., VI, STAND, SIT, and AB skiers) and sex on RTdiffs for top-3 and top-8 skiers. Furthermore, the main effect of season and skiing group on RTdiffs for top-3 and top-8 skiers were investigated. All models were adjusted for distance, skiing style (classical- and freestyle), and event type (WC, WCH, and PWG/OWG).ResultsRTdiffs were significantly larger in Para compared to AB skiers (top-3: 2.1 vs. 0.9%; top-8: 6.2 vs. 2.1%, all p < 0.01), and in female compared to male skiers (top-3: 1.8 vs. 1.3%; top-8: 4.9 vs. 3.5%, all p < 0.05). For top-3 skiers, RTdiffs did not significantly differ between the Para categories (all p > 0.2), while for top-8 skiers RTdiffs were significantly larger for VI compared to SIT and STAND (7.0 vs. 5.5 and 5.6%, respectively, all p < 0.05). RTdiffs were stable across the 2011–2020 seasons for top-3 skiers (VI: 1.7–3.6%, STAND: 1.1–2.2%, SIT: 1.0–3.9%, AB: 0.4–1.1%; all p > 0.1) and top-8 skiers (VI: 3.4–12.0%, STAND: 2.6–5.7%, SIT: 1.9–5.9%, AB: 0.1–1.7%; all p > 0.1).ConclusionThe larger RTdiffs in Para compared to AB skiers indicate larger variability in performance, which are in part disability related. Female skiers displayed larger RTdiffs than their male counterparts, indicating larger variability in performance among the female skiers. Our results provide insights about performance demands in Para cross-country skiing, which is of relevance for coaches and skiers.

Monitoring the Evolution of Asynchrony between Mean Arterial Pressure and Mean Cerebral Blood Flow via Cross-Entropy Methods.

Cerebrovascular control is carried out by multiple nonlinear mechanisms imposing a certain degree of coupling between mean arterial pressure (MAP) and mean cerebral blood flow (MCBF). We explored the ability of two nonlinear tools in the information domain, namely cross-approximate entropy (CApEn) and cross-sample entropy (CSampEn), to assess the degree of asynchrony between the spontaneous fluctuations of MAP and MCBF. CApEn and CSampEn were computed as a function of the translation time. The analysis was carried out in 23 subjects undergoing recordings at rest in supine position (REST) and during active standing (STAND), before and after surgical aortic valve replacement (SAVR). We found that at REST the degree of asynchrony raised, and the rate of increase in asynchrony with the translation time decreased after SAVR. These results are likely the consequence of the limited variability of MAP observed after surgery at REST, more than the consequence of a modified cerebrovascular control, given that the observed differences disappeared during STAND. CApEn and CSampEn can be utilized fruitfully in the context of the evaluation of cerebrovascular control via the noninvasive acquisition of the spontaneous MAP and MCBF variability.

Respiration is a Confounder of the Closed Loop Relationship Between Mean Arterial Pressure and Mean Cerebral Blood Flow.

This study tested the hypothesis that respiration (RESP) is a confounder or suppressor of the closed loop relationship responsible for the cerebrovascular dynamical interactions as assessed from spontaneous variability of mean arterial pressure (MAP) and mean cerebral blood flow (MCBF). The evaluation was carried out in the information domain via transfer entropy (TE) estimated through a linear model-based approach comparing TE markers computed solely over MAP and MCBF series with TE indexes accounting for the eventual action of RESP over MAP and MCBF. We considered 11 patients (age: 76±5 yrs, 7 males) undergoing surgical aortic valve replacement (SAVR) at supine resting (REST) and during active standing (STAND) before and after SAVR surgery. The decrease of the predictive ability of MCBF to MAP when accounting for RESP compared to the one assessed when disregarding RESP suggested that RESP is a confounder of the link from MCBF to MAP along the Cushing reflex instead of being a suppressor. This result was more evident in POST when autonomic control was dramatically depressed and in an unchallenged condition such as REST. RESP did not affect significantly the link from MAP to MCBF along the pressure-to-flow relationship. Clarification of the type of RESP influence on the MAP-MCBF closed loop relationship could favor a deeper characterization of cerebrovascular interactions and the comprehension of cerebral autoregulation mechanisms.Clinical Relevance- This study suggests that respiration is a confounder of the closed loop relationship between MAP and MCBF, especially of the flow-to-pressure causal link. This result might open new possibilities in elucidating the mechanisms of cerebral autoregulation in healthy and pathological populations.

P6. Spinopelvic alignment changes between seated and standing positions in pre and post total hip replacement patients

<h3>BACKGROUND CONTEXT</h3> The inter-relationship between the hip and spine has been increasingly studied in recent years, particularly as it pertains to the effect of spinal deformity and hip osteoarthritis (OA). Changing from standing (ST) to seated (SE) requires rotation of the femur from an almost vertical plane to the horizontal. OA of the hip significantly limits hip extension, resulting in less ability to recruit pelvic tilt (PT) in ST, and requiring increased PT in SE to compensate for loss of hip flexion. To date, the effect of total hip arthroplasty (THA) in altering spinopelvic SE and ST mechanics has not been reported. <h3>PURPOSE</h3> To investigate the change in spinopelvic alignment parameters between seated and standing positions in pre and post THA patients. <h3>STUDY DESIGN/SETTING</h3> Retrospective review at a single academic institution. <h3>PATIENT SAMPLE</h3> Adult patients undergoing THA with full body sitting and standing radiographs pre- and post-THA. <h3>OUTCOME MEASURES</h3> Spinopelvic alignment measures including pelvic incidence (PI), pelvic tilt (PT), T1 pelvic angle (TPA), sacral slope (SS), sagittal vertical axis (SVA), pelvic incidence and lumbar lordosis mismatch (PI-LL), and lumbar lordosis (LL). <h3>METHODS</h3> Patients ≥18yo undergoing THA for hip OA with full spine SE and ST radiographs pre and post THA were included. Spinopelvic alignment was analyzed pre-THA and post-THA in both ST and SE positions in a relaxed posture with the fingers on the clavicles. Paired t-test analysis was performed to compare Pre-and Post-THA groups. The effect of TL deformity (SVA>50, TPA>20, PI-LL>10) on these changes was also analyzed. Statistical significance set at p<0.05. <h3>RESULTS</h3> There were 192 patients assessed. 179 patients had thoracolumbar (TL) deformity; TPA>20 (N=46), PI-LL>10 (N=55), and SVA>50 (N=78). In standing position, patients have a significant reduction in SVA post THA vs pre THA (34.09±42.69 vs 45.03±46.87, p=0.001) as a result of an increase in PT (15.7±9.74 ᵒ vs 14.6±9.88ᵒ,p=0.028), without significant changes in spinal alignment parameters including lumbar lordosis (-51.26±14.59 vs -50.26±14.87, p=0.092), thoracic kyphosis (35.98±12.72 vs 35.40±13.16, p=0.180), sacral slope (38.15±10.77 vs 38.83±11.31, p=0.205), T1 pelvic angle (14.22±9.94 vs 14.51±10.13, p=0.053) and PI-LL mismatch (2.59±14.61 vs 3.35±14.92, p=0.183). This change in ST_SVA was larger in patients with TL deformity, specifically in those with SVA>50 (61.29±45.69 vs 89.48±35.91, p=0.001), in PI-LL > 10 (59.08±45.49 vs 73.36±48.50, p=0.001) and in TPA>20 subsets (62.14±49.94 vs 82.28±49.55, p=0.001). When moving from ST to SE, the ΔPT was reduced post THA (16.70±15.27ᵒ vs 20.85±17.27ᵒ, p=0.001) in addition to a smaller SE_PT vs pre-THA (32.41±14.47 vs 35.46±14.20, p=0.006). <h3>CONCLUSIONS</h3> Post Total Hip Arthroplasty (THA), patients demonstrated an increased recruitment of pelvic retroversion to achieve a better global balance by reduction in standing SVA. This compensation was achieved solely by greater mobility of their hip and pelvis, and without a significant change in spinal alignment. ST_SVA reduction was more pronounced in patients with thoracolumbar (TL) spinal deformity (SVA>50, TPA>20, PI-LL>10). On the converse, PT was reduced in sitting (SE) post-THA compared to pre-THA, and the compensatory change in PT was also reduced between ST and SE as a result of restoration of hip flexion. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

Abnormal Sympathetic Responses To Orthostasis After Concussion Explored Through Blood Pressure Variability

PURPOSE: Orthostasis causes a gravity-dependent redistribution of blood volume to the lower extremities. The baroreflex coordinates an effector response through the sympathetic nervous system (SNS) to the peripheral vasculature to buffer changes in systolic blood pressure (SBP). In autonomic dysfunction (AD), impaired or exaggerated responses may lead to orthostatic hypotension (OHypo) or hypertension (OHTN). AD is becoming an increasingly recognized consequence of an acute concussion injury. The purpose of this study was to evaluate the SNS responses to orthostasis in recently concussed athletes. METHODS: A prospective study was performed in 32 concussed college athletes (gender: 22 female, 10 male; age: 20 ± 1 yrs; height: 1.74 ± 0.11 m; weight: 74 ± 13 kg) and 14 athlete controls (gender: 8 female, 6 male; age: 20 ± 2 yrs; height: 1.70 ± 0.10 m; weight: 69 ± 13 kg). Beat-to-beat SBP was assessed digitally at rest for 10 minutes in the supine (SUP) position and then for 3 minutes in the standing (STND) position within 48 hours (48H) of concussion. The change in SBP (ΔSBP) was computed from the difference between SUP and the final 15 seconds of STND. ΔSBP was then categorized as Normal (NR: ΔSBP -19 to +19 mmHg); OHypo (SBP fall ≥20 mmHg); and, OHTN (SBP rise ≥20 mmHg) for each group. Fast-Fourier transform was performed and power calculated for the total, very low, low and high frequency power (TP, vLF, LF and HF, respectively) spectra in each position; the variables were log10 transformed for parametric analyses. RESULTS: Fourteen control and 14 concussion participants had a NR ΔSBP, whereas 11 concussion participants had OHypo and 7 had OHTN. There were no differences across these four groups for the TP, vLF, LF, and HF in the SUP position. In the STND position, TP (p < 0.0001), vLF (p < 0.0001), and HF (p < 0.05) were significant for the omnibus model. Bonferroni post hoc analyses revealed that the OHypo concussion group had a significantly lower TP and vLF than each of the 3 other groups, and the OHTN concussion group had a significant elevation and trend toward a significant elevation of HF compared to the OHypo and NR concussion groups, respectively. CONCLUSIONS: Different mechanisms appear to contribute to and influence AD during orthostasis within 48H of concussion injury.

The Effect of Wet Conditions and Surface Combat Swimming on Shooting.

Shooting ability is an important aspect of performance in some sports and is vital during a military operation. Load carriage, clothing, and equipment normally associated with fatigue and reduced field of vision or lack of stability at a specific point are important factors that affect the ability to aim when shooting. Additionally, gun support and equipment appear to differentially affect shooting ability with varying shooting positions. All of the studies examining these factors have taken place on dry land and not in water. However, up to date, no study has examined the effect of wet conditions, especially after surface combat swimming (sCS), on shooting ability in different shooting positions. The purpose of this study was to determine the effect of fatigue, produced by prolonged sCS, on a fighter's shooting ability. In addition, we investigated whether the effect of fatigue and wet conditions differed between the shooting positions. Forty-five participants performed 10 shots in a shooting simulator while standing (ST) and 10 shots while kneeling (KN). This was performed twice and in three conditions: dry, wet, and after 1,000 m of sCS. Wet conditions did not significantly affect shooting abilities. Surface combat swimming negatively affected shooting ability when both ST and KN. The reduction in the center of gravity (COG) of the shots after sCS was 3.7 ± 2.5% for ST and 3.5 ± 0.8% for KN (P < .01). This was accompanied by the increase in horizontal and vertical movement of the gun after the sCS (P < .01). Kneeling was more stable, as shown by a higher percentage of COG of the shots by 3.3 ± 0.1% (P < .01) and by fewer gun movements in both axes (P < .01). In conclusion, combat swimming affects shooting ability, both in ST and in KN positions. The KN position provides better stability and improved shooting ability.

Prediction of human gait activities using wearable sensors.

This paper aims to enhance the accuracy of human gait prediction using machine learning algorithms. Three classifiers are used in this paper: XGBoost, Random Forest, and SVM. A predefined dataset is used for feature extraction and classification. Gait prediction is determined during several locomotion activities: sitting (S), level walking (LW), ramp ascend (RA), ramp descend (RD), stair ascend (SA), stair descend (SD), and standing (ST). The results are gained for steady-state (SS) and overall (full) gait cycle. Two sets of sensors are used. The first set uses inertial measurement units only. The second set uses inertial measurement units, electromyography, and electro-goniometers. The comparison is based on prediction accuracy and prediction time. In addition, a comparison between the prediction times of XGBoost with CPU and GPU is introduced due to the easiness of using XGBoost with GPU. The results of this paper can help to choose a classifier for gait prediction that can obtain acceptable accuracy with fewer types of sensors.

Task-Related Hemodynamic Response Alterations During Slacklining: An fNIRS Study in Advanced Slackliners.

The ability to maintain balance is based on various processes of motor control in complex neural networks of subcortical and cortical brain structures. However, knowledge on brain processing during the execution of whole-body balance tasks is still limited. In the present study, we investigated brain activity during slacklining, a task with a high demand on balance capabilities, which is frequently used as supplementary training in various sports disciplines as well as for lower extremity prevention and rehabilitation purposes in clinical settings. We assessed hemodynamic response alterations in sensorimotor brain areas using functional near-infrared spectroscopy (fNIRS) during standing (ST) and walking (WA) on a slackline in 16 advanced slackliners. We expected to observe task-related differences between both conditions as well as associations between cortical activity and slacklining experience. While our results revealed hemodynamic response alterations in sensorimotor brain regions such as primary motor cortex (M1), premotor cortex (PMC), and supplementary motor cortex (SMA) during both conditions, we did not observe differential effects between ST and WA nor associations between cortical activity and slacklining experience. In summary, these findings provide novel insights into brain processing during a whole-body balance task and its relation to balance expertise. As maintaining balance is considered an important prerequisite in daily life and crucial in the context of prevention and rehabilitation, future studies should extend these findings by quantifying brain processing during task execution on a whole-brain level.

Intravenous Regional Limb Perfusion in Standing and Recumbent Horses: A Comparative Radiographic Study

Although pharmacokinetic studies of drugs administered by intravenous regional limb perfusion (IRLP) to treat equine orthopedic infections suggest efficient drug distribution in the limbs, it remains unclear whether drug perfusion is affected by the position of the horse during the procedure. This study compared the perfusion of a radiopaque contrast into tissues of the extremities of horses maintained in standing and recumbent positions during an IRLP. Radiopaque contrast was administered through IRLP into the cephalic vein of 10 healthy adult horses under general anesthesia and right lateral recumbency (RG) or under sedation and standing (SG). The same animals were used in both groups, respecting a two-week washout period. Sequential radiographic images were performed immediately at the beginning of contrast administration (T0) and after 10, 20, 30, 40, and 50 minutes. Tourniquets were removed after 30 minutes. The time required for the contrast to reach the hooves was compared between groups. Contrast reached the hooves faster in SG (114 ± 15 seconds) compared with RG (236 ± 29 seconds) (P < 0.5). SG showed more uniform perfusion of the limb vessels, whereas RG showed more deposition of the contrast in the lateral digital vein, with smaller amounts reaching the hooves. From T10 onward, soft tissue radiopacity increased, albeit more markedly in standing than in recumbent animals, remaining until T50. Contrast radiography evidenced that IRLP performed in standing position leads to a quicker and more uniform perfusion of the vasculature and a more noticeable diffusion to the tissues than in recumbent horses.

Standing Ready for the Next Surprise

Standing Ready for the Next Surprise