Direct biomechanical manipulation of human gait stability: A systematic review.

People fall more often when their gait stability is reduced. Gait stability can be directly manipulated by exerting forces or moments onto a person, ranging from simple walking sticks to complex wearable robotics. A systematic review of the literature was performed to determine: What is the level of evidence for different types of mechanical manipulations on improving gait stability? The study was registered at PROSPERO (CRD42020180631). Databases Embase, Medline All, Web of Science Core Collection, Cochrane Central Register of Controlled Trials, and Google Scholar were searched. The final search was conducted on the 1st of December, 2022. The included studies contained mechanical devices that influence gait stability for both impaired and non-impaired subjects. Studies performed with prosthetic devices, passive orthoses, and analysing post-training effects were excluded. An adapted NIH quality assessment tool was used to assess the study quality and risk of bias. Studies were grouped based on the type of device, point of application, and direction of forces and moments. For each device type, a best-evidence synthesis was performed to quantify the level of evidence based on the type of validity of the reported outcome measures and the study quality assessment score. Impaired and non-impaired study participants were considered separately. From a total of 4701 papers, 53 were included in our analysis. For impaired subjects, indicative evidence was found for medio-lateral pelvis stabilisation for improving gait stability, while limited evidence was found for hip joint assistance and canes. For non-impaired subjects, moderate evidence was found for medio-lateral pelvis stabilisation and limited evidence for body weight support. For all other device types, either indicative or insufficient evidence was found for improving gait stability. Our findings also highlight the lack of consensus on outcome measures amongst studies of devices focused on manipulating gait.

Reaction moments matter when designing lower-extremity robots for tripping recovery.

Balance recovery after tripping often requires an active adaptation of foot placement. Thus far, few attempts have been made to actively assist forward foot placement for balance recovery employing wearable devices. This study aims to explore the possibilities of active forward foot placement through two paradigms of actuation: assistive moments exerted with the reaction moments either internal or external to the human body, namely 'joint' moments and 'free' moments, respectively. Both paradigms can be applied to manipulate the motion of segments of the body (e.g., the shank or thigh), but joint actuators also exert opposing reaction moments on neighbouring body segments, altering posture and potentially inhibiting tripping recovery. We therefore hypothesised that a free moment paradigm is more effective in assisting balance recovery following tripping. The simulation software SCONE was used to simulate gait and tripping over various ground-fixed obstacles during the early swing phase. To aid forward foot placement, joint moments and free moments were applied either on the thigh to augment hip flexion or on the shank to augment knee extension. Two realizations of joint moments on the hip were simulated, with the reaction moment applied to either the pelvis or the contralateral thigh. The simulation results show that assisting hip flexion with either actuation paradigm on the thigh can result in full recovery of gait with a margin of stability and leg kinematics closely matching the unperturbed case. However, when assisting knee extension with moments on the shank, free moment effectively assist balance but joint moments with the reaction moment on the thigh do not. For joint moments assisting hip flexion, placement of the reaction moment on the contralateral thigh was more effective in achieving the desired limb dynamics than placing the reaction on the pelvis. Poor choice of placement of reaction moments may therefore have detrimental consequences for balance recovery, and removing them entirely (i.e., free moment) could be a more effective and reliable alternative. These results challenge conventional assumptions and may inform the design and development of a new generation of minimalistic wearable devices to promote balance during gait.

Probiotics for maintenance of remission in ulcerative colitis.

BACKGROUND: Ulcerative colitis is an inflammatory condition affecting the colon, with an annual incidence of approximately 10 to 20 per 100,000 people. The majority of people with ulcerative colitis can be put into remission, leaving a group who do not respond to first- or second-line therapies. There is a significant proportion of people who experience adverse effects with current therapies. Consequently, new alternatives for the treatment of ulcerative colitis are constantly being sought. Probiotics are live microbial feed supplements that may beneficially affect the host by improving intestinal microbial balance, enhancing gut barrier function and improving local immune response. OBJECTIVES: The primary objective was to determine the efficacy of probiotics compared to placebo, no treatment, or any other intervention for the maintenance of remission in people with ulcerative colitis. The secondary objective was to assess the occurrence of adverse events associated with the use of probiotics. SEARCH METHODS: We searched CENTRAL, MEDLINE, Embase, and two other databases on 31 October 2019. We contacted authors of relevant studies and manufacturers of probiotics regarding ongoing or unpublished trials that may be relevant to the review, and we searched ClinicalTrials.gov. We also searched references of trials for any additional trials. SELECTION CRITERIA: Randomised controlled trials (RCTs) that compared probiotics against placebo or any other intervention, in both adults and children, for the maintenance of remission in ulcerative colitis were eligible for inclusion. Maintenance therapy had to be for a minimum of three months when remission has been established by any clinical, endoscopic,histological or radiological relapse as defined by study authors. DATA COLLECTION AND ANALYSIS: Two review authors independently conducted data extraction and 'Risk of bias' assessment of included studies. We analysed data using Review Manager 5. We expressed dichotomous and continuous outcomes as risk ratios (RRs) and mean differences (MDs) with 95% confidence intervals (CIs). We assessed the certainty of the evidence using the GRADE methodology. MAIN RESULTS: In this review, we included 12 studies (1473 randomised participants) that met the inclusion criteria. Participants were mostly adults. The studies compared probiotics to placebo, probiotics to 5-aminosalicylic acid (5-ASA) and a combination of probiotics and 5-ASA to 5-ASA. The studies ranged in length from 12 to 52 weeks. The average age of participants was between 32 and 51, with a range between 18 and 88 years. Seven studies investigated a single bacterial strain, and five studies considered mixed preparations of multiple strains. The risk of bias was high in all except three studies due to selective reporting, incomplete outcome data and lack of blinding. This resulted in low- to very low-certainty of evidence. It is uncertain if there is any difference in occurrence of clinical relapse when probiotics are compared with placebo (RR 0.87, 95% CI 0.63 to 1.18; 4 studies, 361 participants; very low-certainty evidence (downgraded for risk of bias, imbalance in baseline characteristics and imprecision)). It is also uncertain whether probiotics lead to a difference in the number of people who maintain clinical remission compared with placebo (RR 1.16, 95% CI 0.98 to 1.37; 2 studies, 141 participants; very low-certainty evidence (downgraded for risk of bias, imbalance in baseline characteristics and imprecision)). When probiotics are compared with 5-ASA, there may be little or no difference in clinical relapse (RR 1.01, 95% CI 0.84 to 1.22; 2 studies, 452 participants; low-certainty evidence) and maintenance of clinical remission (RR 1.06, 95% CI 0.90 to 1.25; 1 study, 125 participants; low-certainty evidence). It is uncertain if there is any difference in clinical relapse when probiotics, combined with 5-ASA are compared with 5-ASA alone (RR 1.11, 95% CI 0.66 to 1.87; 2 studies, 242 participants; very low-certainty evidence (downgraded due to risk of bias and imprecision)). There may be little or no difference in maintenance of remission when probiotics, combined with 5-ASA, are compared with 5-ASA alone (RR 1.05, 95% CI 0.89 to 1.24; 1 study, 122 participants; low-certainty evidence). Where reported, most of the studies which compared probiotics with placebo recorded no serious adverse events or withdrawals due to adverse events. For the comparison of probiotics and 5-ASA, one trial reported 11/110 withdrawals due to adverse events with probiotics and 11/112 with 5-ASA (RR 1.02, 95% CI 0.46 to 2.25; 222 participants; very low-certainty evidence). Discontinuation of therapy was due to gastrointestinal symptoms. One study (24 participants) comparing probiotics combined with 5-ASA with 5-ASA alone, reported no withdrawals due to adverse events; and two studies reported two withdrawals in the probiotic arm, due to avascular necrosis of bilateral femoral head and pulmonary thromboembolism (RR 5.29, 95% CI 0.26 to 107.63; 127 participants; very low-certainty evidence). Health-related quality of life and need for additional therapy were reported infrequently. AUTHORS' CONCLUSIONS: The effectiveness of probiotics for the maintenance of remission in ulcerative colitis remains unclear. This is due to low- to very low-certainty evidence from poorly conducted studies, which contribute limited amounts of data from a small number of participants. Future trials comparing probiotics with 5-ASA rather than placebo will better reflect conventional care given to people with ulcerative colitis. Appropriately powered studies with a minimum length of 12 months are needed.

Probiotics for induction of remission in ulcerative colitis.

BACKGROUND: Ulcerative colitis is an inflammatory condition affecting the colon, with an annual incidence of approximately 10 to 20 per 100,000 people. The majority of people with ulcerative colitis can be put into remission, leaving a group who do not respond to first- or second-line therapies. There is a significant proportion of people who experience adverse effects with current therapies. Consequently, new alternatives for the treatment of ulcerative colitis are constantly being sought. Probiotics are live microbial feed supplements that may beneficially affect the host by improving intestinal microbial balance, enhancing gut barrier function and improving local immune response. OBJECTIVES: To assess the efficacy of probiotics compared with placebo or standard medical treatment (5-aminosalicylates, sulphasalazine or corticosteroids) for the induction of remission in people with active ulcerative colitis. SEARCH METHODS: We searched CENTRAL, MEDLINE, Embase, and two other databases on 31 October 2019. We contacted authors of relevant studies and manufacturers of probiotics regarding ongoing or unpublished trials that may be relevant to the review, and we searched ClinicalTrials.gov. We also searched references of trials for any additional trials. SELECTION CRITERIA: Randomised controlled trials (RCTs) investigating the effectiveness of probiotics compared to standard treatments or placebo in the induction of remission of active ulcerative colitis. We considered both adults and children, with studies reporting outcomes of clinical, endoscopic, histologic or surgical remission as defined by study authors DATA COLLECTION AND ANALYSIS: Two review authors independently conducted data extraction and 'Risk of bias' assessment of included studies. We analysed data using Review Manager 5. We expressed dichotomous and continuous outcomes as risk ratios (RRs) and mean differences (MDs) with 95% confidence intervals (CIs). We assessed the certainty of the evidence using the GRADE methodology. MAIN RESULTS: In this review, we included 14 studies (865 randomised participants) that met the inclusion criteria. Twelve of the studies looked at adult participants and two studies looked at paediatric participants with mild to moderate ulcerative colitis, the average age was between 12.5 and 47.7 years. The studies compared probiotics to placebo, probiotics to 5-ASA and a combination of probiotics plus 5-ASA compared to 5-ASA alone. Seven studies used a single probiotic strain and seven used a mixture of strains. The studies ranged from two weeks to 52 weeks. The risk of bias was high for all except two studies due to allocation concealment, blinding of participants, incomplete reports of outcome data and selective reporting. This led to GRADE ratings of the evidence ranging from moderate to very low. Probiotics versus placebo Probiotics may induce clinical remission when compared to placebo (RR 1.73, 95% CI 1.19 to 2.54; 9 studies, 594 participants; low-certainty evidence; downgraded due to imprecision and risk of bias, number needed to treat for an additional beneficial outcome (NNTB) 5). Probiotics may lead to an improvement in clinical disease scores (RR 2.29, 95% CI 1.13 to 4.63; 2 studies, 54 participants; downgraded due to risk of bias and imprecision). There may be little or no difference in minor adverse events, but the evidence is of very low certainty (RR 1.04, 95% CI 0.42 to 2.59; 7 studies, 520 participants). Reported adverse events included abdominal bloating and discomfort. Probiotics did not lead to any serious adverse events in any of the seven studies that reported on it, however five adverse events were reported in the placebo arm of one study (RR 0.09, CI 0.01 to 1.66; 1 study, 526 participants; very low-certainty evidence; downgraded due to high risk of bias and imprecision). Probiotics may make little or no difference to withdrawals due to adverse events (RR 0.85, 95% CI 0.42 to 1.72; 4 studies, 401 participants; low-certainty evidence). Probiotics versus 5-ASA There may be little or no difference in the induction of remission with probiotics when compared to 5-ASA (RR 0.92, 95% CI 0.73 to 1.16; 1 study, 116 participants; low-certainty evidence; downgraded due to risk of bias and imprecision). There may be little or no difference in minor adverse events, but the evidence is of very low certainty (RR 1.33, 95% CI 0.53 to 3.33; 1 study, 116 participants). Reported adverse events included abdominal pain, nausea, headache and mouth ulcers. There were no serious adverse events with probiotics, however perforated sigmoid diverticulum and respiratory failure in a patient with severe emphysema were reported in the 5-ASA arm (RR 0.21, 95% CI 0.01 to 4.22; 1 study, 116 participants; very low-certainty evidence). Probiotics combined with 5-ASA versus 5-ASA alone Low-certainty evidence from a single study shows that when combined with 5-ASA, probiotics may slightly improve the induction of remission (based on the Sunderland disease activity index) compared to 5-ASA alone (RR 1.22 CI 1.01 to 1.47; 1 study, 84 participants; low-certainty evidence; downgraded due to unclear risk of bias and imprecision). No information about adverse events was reported. Time to remission, histological and biochemical outcomes were sparsely reported in the studies. None of the other secondary outcomes (progression to surgery, need for additional therapy, quality of life scores, or steroid withdrawal) were reported in any of the studies. AUTHORS' CONCLUSIONS: Low-certainty evidence suggests that probiotics may induce clinical remission in active ulcerative colitis when compared to placebo. There may be little or no difference in clinical remission with probiotics alone compared to 5-ASA. There is limited evidence from a single study which failed to provide a definition of remission, that probiotics may slightly improve the induction of remission when used in combination with 5-ASA. There was no evidence to assess whether probiotics are effective in people with severe and more extensive disease, or if specific preparations are superior to others. Further targeted and appropriately designed RCTs are needed to address the gaps in the evidence base. In particular, appropriate powering of studies and the use of standardised participant groups and outcome measures in line with the wider field are needed, as well as reporting to minimise risk of bias.

Experimental estimation of energy absorption during heel strike in human barefoot walking.

Metabolic energy expenditure during human gait is poorly understood. Mechanical energy loss during heel strike contributes to this energy expenditure. Previous work has estimated the energy absorption during heel strike as 0.8 J using an effective foot mass model. The aim of our study is to investigate the possibility of determining the energy absorption by more directly estimating the work done by the ground reaction force, the force-integral method. Concurrently another aim is to compare this method of direct determination of work to the method of an effective foot mass model. Participants of our experimental study were asked to walk barefoot at preferred speed. Ground reaction force and lower leg kinematics were collected at high sampling frequency (3000 Hz; 1295 Hz), with tight synchronization. The work done by the ground reaction force is 3.8 J, estimated by integrating this force over the foot-ankle deformation. The effective mass model is improved by dropping the assumption that foot-ankle deformation is maximal at the instant of the impact force peak. On theoretical grounds it is clear that in the presence of substantial damping that peak force and peak deformation do not occur simultaneously. The energy absorption results, due the vertical force only, corresponding to the force-integral method is similar to the results of the improved application of the effective mass model (2.7 J; 2.5 J). However the total work done by the ground reaction force calculated by the force-integral method is significantly higher than that of the vertical component alone. We conclude that direct estimation of the work done by the ground reaction force is possible and preferable over the use of the effective foot mass model. Assuming that energy absorbed is lost, the mechanical energy loss of heel strike is around 3.8 J for preferred walking speeds (≈ 1.3 m/s), which contributes to about 15-20% of the overall metabolic cost of transport.

Short range stiffness elastic limit depends on joint velocity.

Muscles behave as elastic springs during the initial strain phase, indicated as short range stiffness (SRS). Beyond a certain amount of strain the muscle demonstrates a more viscous behavior. The strain at which the muscle transits from elastic- to viscous-like behavior is called the elastic limit and is believed to be the result of breakage of cross-bridges between the contractile filaments. The aim of this study was to test whether the elastic limit, measured in vivo at the wrist joint, depended on the speed of lengthening. Brief extension rotations were imposed to the wrist joint (n=8) at four different speeds and at three different levels of voluntary torque using a servo controlled electrical motor. Using a recently published identification scheme, we quantified the elastic limit from measured joint angle and torque. The results showed that the elastic limit significantly increased with speed in a linear way, indicating to a constant time of approximately 30 ms before cross-bridges break. The implications for movement control of the joint are discussed.