Posterior single-stepping thresholds are prospectively related to falls in older women.

BACKGROUND: Falls are a leading cause of injury in older women. Stepping thresholds quantify balance-reaction capabilities. It is unclear how such evaluations predict falls in comparison to, or as a complement to, other objective measures of gait, standing postural control, strength, and balance confidence. AIMS: The objective of this study was to determine if stepping thresholds are prospectively related to falls in older women. METHODS: For this prospective cohort study, 125 ambulatory, community-dwelling women, age ≥ 65 years were recruited. Using a treadmill to deliver perturbations to standing participants, we determined anteroposterior single- and multiple-stepping thresholds. Here, thresholds represent the minimum perturbation magnitudes that consistently evoke one step or multiple steps. In addition, gait kinematics, obstacle-crossing kinematics, standing sway measures, unipedal stance time, the functional reach, lower extremity isometric strength, grip strength, balance confidence, and fall history were evaluated. Falls were prospectively recorded for one year. RESULTS: Seventy-four participants (59%) fell at least once. Posterior single-stepping thresholds were the only outcome that predicted future fall status (OR = 1.50, 95% CI 1.01-2.28; AUC = .62). A multivariate approach added postural sway with eyes closed as a second predictive variable, although predictive abilities were not meaningfully improved. DISCUSSION: These results align with the previous evidence that reactive balance is a prospective indicator of fall risk. Unlike previous studies, strength scaled to body size did not contribute to fall prediction. CONCLUSION: Posterior single-stepping thresholds held a significant relationship with future fall status. This relationship was independent of, and superior to that of, other measures of standing balance, gait, strength, and balance confidence.

Enhancing hydrogen production through anode fed-batch mode and controlled cell voltage in a microbial electrolysis cell fully catalysed by microorganisms.

A microbial electrolysis cell (MEC) fully catalysed by microorganisms is an attractive technology because it incorporates the state-of-the-art concept of converting organic waste to hydrogen with less external energy input than conventional electrolysers. In this work, the impact of the anode feed mode on the production of hydrogen by the biocathode was studied. In the first part, three feed modes and MEC performance in terms of hydrogen production were evaluated. The results showed the highest hydrogen production under the continuous mode (14.6 ± 0.4), followed by the fed-batch (12.7 ± 0.4) and batch (0 L m-2 cathode day-1) modes. On one hand, the continuous mode only increased by 15% even though the hydraulic retention time (HRT) (2.78 h) was lower than the fed-batch mode (HRT 5 h). A total replacement (fed-batch) rather than a constant mix of existing anolyte and fresh medium (continuous) was preferable. On the other hand, no hydrogen was produced in batch mode due to the extensive HRT (24 h) and bioanode starvation. In the second part, the fed-batch mode was further evaluated using a chronoamperometry method under a range of applied cell voltages of 0.3-1.6 V. Based on the potential evolution at the electrodes, three main regions were identified depending on the applied cell voltages: the cathode activation (<0.8 V), transition (0.8-1.1 V), and anode limitation (>1.1 V) regions. The maximum hydrogen production recorded was 12.1 ± 2.1 L m-2 cathode day-1 at 1.0 V applied voltage when the oxidation and reduction reactions at the anode and cathode were optimal (2.38 ± 0.61 A m-2). Microbial community analysis of the biocathode revealed that Alpha-, and Deltaproteobacteria were dominant in the samples with >70% abundance. At the genus level, Desulfovibrio sp. was the most abundant in the samples, showing that these microbes may be responsible for hydrogen evolution.

Effect of upper extremity constraints on functional and dynamic postural control in children with hemiplegic cerebral palsy.

PURPOSE: To compare the effects of upper extremity constraints on functional and dynamic postural control in children with hemiplegic cerebral palsy. MATERIALS AND METHODS: Twelve children with hemiplegic cerebral palsy and 12 typically developing children ages 5 to 12 years (GMFCS I-II) were evaluated with the Timed Up and Go (TUG) and Biodex Balance System during three upper extremity (UE) conditions: 1) Free UEs (no constraints), 2) Simple UE constraint (unaffected/dominant UE constrained with a sling), and 3) Difficult UE constraint (Simple constraint plus the other UE holding cup of water). RESULTS: The UE condition had significant effects on Overall Stability Index (OSI) (F(2,44) = 24.899, p < .001), Medial-Lateral Stability Index (MLSI) (F(2,44) = 4.380, p = .018), Anterior-Posterior Stability Index (F(2,44) = 6.187, p = .004), and TUG scores (F(2,44) = 113.372, p < .001). Group was significant for OSI (F(1,22) = 7.906, p = .010), MLSI (F(1,22) = 13.113, p = .002), and TUG (F(1,22) = 36.282, p < .001). CONCLUSIONS: The upper extremity appears to have a role in maintaining functional balance and postural stability in children with hemiplegic cerebral palsy and should be considered during intervention programs.

IMU, sEMG, or their cross-correlation and temporal similarities: Which signal features detect lateral compensatory balance reactions more accurately?

BACKGROUND AND OBJECTIVE: Falls are the leading cause of fatal and non-fatal injuries among seniors worldwide. While laboratory evidence supports the view that impaired ability to execute compensatory balance responses (CBRs) is linked to an increased risk of falling, existing unsupervised fall risk assessment methods are mainly focused on detecting changes in spatio-temporal gait parameters over time rather than naturally-occurring CBR events. To address the gap in available methods, this paper compares the capability of machine learning-based models trained on the kinematic data from inertial measurement units (IMU) and surface electromyography (sEMG) features to detect lateral CBRs, to ultimately address detection of CBRs in free-living conditions. Moreover, we propose a novel "Hybrid" feature set, which considers cross-correlation and temporal similarities between the normalized kinematic and sEMG signals. METHODS: Focusing on frontal plane perturbations, a classifier to automatically: 1) detect lateral CBRs during normal gait, and 2) identify type (i.e., crossover, sidestep) using data from three wearable IMUs and 4 sEMG signals from the thigh (i.e., biceps femoris, rectus femoris) and lower leg muscles (i.e., gastrocnemious, tibialis anterior) was developed. In total, 600 trials (including 358 lateral CBRs) from 7 young, healthy adults were analyzed. The effects of feature type (IMU, sEMG, Hybrid) and sensor placement on the random forest-based classifier performance were investigated. RESULTS: CBR detection (i.e., CBR vs normal gait) accuracies (leave-one-subject-out cross validation) were 83.95% and 99.21% using sEMG-based and IMU-based features, respectively, which dropped to 72.17% and 84.83% for the multiclass identification (i.e., side-step vs cross-over vs normal gait) problem. Findings yielded shank as the best overall location for the multiclass problem, and chest as the most accurate for CBR detection. In general, adding sEMG and Hybrid features to IMUs yielded incremental improvements in CBR detection and type identification (87.03% leave-one-subject-out cross-validation for type identification). CONCLUSION: The findings of this study demonstrate that IMU-based features are favourable over sEMG and Hybrid features for the task of CBR detection, with incremental value for type identification. Evidence presented suggests that Hybrid features may increase performance for other wearable sensor applications (e.g. activity recognition systems).

The contribution of counter-rotation movements during fall recovery: A validation study.

Three mechanisms of maintaining standing stability include M1 - moving the COP within the base of support, M2 - segment counter-rotation, and M3 - applying an external force. To date, the contributions of these mechanisms have not been quantified for the response to an external postural disturbance. The purpose of this study was to evaluate the construct validity of measures that quantify the M2 contribution to anteroposterior fall recovery. We evaluated the whole-body rotation contribution, as well as a measure specific to arm motion (MARMS). With segment counter-rotation as the main focus of this study, we examined standing feet-in-place responses to treadmill-induced falls. The treatment validity of our measures was assessed by comparing unconstrained responses to those with constrained arm motion. The convergent validity of our measures was assessed by correlating peak shoulder flexion and extension velocities with counter-rotation contributions. Eleven unimpaired participants responded to anteroposterior belt accelerations from a treadmill, and the M2 and MARMS contributions were quantified from three-dimensional segment motion. The treatment validity of these measures was partially supported. Constraining the arms reduced M2 for anterior, but not posterior falls. Conversely, MARMS was reduced for posterior, but not anterior falls. Convergent validity was supported for MARMS (r = 0.64-0.78), but not M2 (r = -0.40 to -0.15). These results support the use of MARMS over M2 when interested in the role of arm motion. Given that arm constraints did not change the contribution of MARMS during a forward fall, unimpaired participants may not necessarily rely on arm motion as part of their recovery strategy in this context.

Influence of Kinesitherapy on Balance Reactions in Patients with Ischemic Stroke in the Chronic Period.

AIM: The study aims to trace the influence of specialized kinesitherapeutic methodology (SKTM) on balance reactions in patients with ischemic stroke in the chronic period (ISChP). MATERIAL AND METHODS: A prospective, multicenter study with 56 patients with ISChP. Evaluation of balance reactions using Berg Balance Scale - BBS, includes implementation of 14 tasks with increasing difficulty reflecting the usual activities of everyday life. The first 5 assignments are used to assess the main balance potential and the remaining 9 (6th to 14th task) include more sophisticated balance tasks. RESULTS: The patients were found with a significant improvement in balance opportunities, according to the scale of Berg. Compared to initial data there is a significant increase in the number of points in the measured indicators for functional and static balance. In absolute terms, positive change is most pronounced during the 1st month with a level of significance of p <0.001. CONCLUSION: The applied specialized kinesitherapeutic methodology continued later as adapted exercise program at home, and significantly improved equilibrium reactions in patients with postural disorders because of ischemic stroke and is with a supportive prolonged exposure.

Effect of airway control by glottal structures on postural stability.

Maintenance of upright posture involves complex neuromotor processes that include control of thoracic and abdominal pressures. Control of airflow by glottal structures is a primary determinant of thoracic pressure and may have a role in control of postural stability. This study aimed to investigate the effect of modulation of airway control on upright postural stability during postural perturbations. Standing balance was gently perturbed in the sagittal plane during 7 breathing/voicing tasks that ranged from completely closed (breath-hold), to partially opened (voicing) or completely open (sigh) glottal conditions in 11 healthy adults. Dependent measures were peak amplitude of displacement of the thorax and center of pressure (CoP). When the glottis was completely open during sigh, thoracic displacement in response to the perturbation was greater than in all other conditions, regardless of direction of perturbation (post hoc, all P < 0.002). The absolute amplitude of CoP displacement was greater with backward perturbation (main effect, Direction P = 0.001) and was greater at both extremes of glottal modulation (glottis closed and completely open) than when the glottis was partially opened during counting out loud (post hoc, all P < 0.04). These results show that airway modulation affects postural control during upright perturbations. The thorax was more stable when the glottis was engaged than when it was required to remain open, whereas control of CoP displacement appeared more optimal during the natural dynamic mid-range airway modulation of voicing. These data suggest that glottal control influences balance, and that glottal control strategies may be an important consideration for patients with breathing and/or balance disorders.