Abstract The harmonic ratio (HR), derived from the Fourier analysis of trunk accelerations, has been described in various ways as a measure of walking smoothness, walking rhythmicity, or dynamic ...stability. There is an increasing interest in applying the HR technique to investigate the impact of various pathologies on locomotion; however, explanation of the method has been limited. The aim here is to present a clear description of the mathematical basis of HRs and an understanding of their interpretation. We present harmonic theory, the interpretation of the HR using sinusoidal signals, and an example using actual trunk accelerations and harmonic analyses during limb-loading conditions. We suggest that the HR method may be better defined, not as a measure of rhythmicity or stability, but as a measure of step-to-step symmetry within a stride.
Abstract Accelerometry (ACC) shows promise as an easily implemented clinical measure of balance. The purpose of the study was to estimate test–retest reliability of ACC measures and determine the ...relationship between ACC measured at the pelvis and underfoot center of pressure (COP) measures during sensory organization test (SOT) conditions. Eighty-one subjects were recruited from the community with no known orthopedic or vestibular deficits (19–85 years). Subjects completed three consecutive, ninety second trials for each of the six SOT conditions, while wearing the accelerometer. ACC and COP time series were described by calculating the normalized path length, root mean square (RMS), and peak-to-peak values. The test–retest reliability of the three measures within each SOT condition was estimated over three trials using the intraclass correlation coefficient. ACC and COP test–retest reliability were similar, ranging from 0.63 to 0.80 using ACC and 0.42 to 0.81 using COP for the measure of normalized path length. Linear regression between ACC and COP measures showed significant correlation under almost every SOT condition using both single and average measures across trials. The degree of association between COP and ACC was equivalent when using the first trial or the 3-trial average, suggesting that one trial may be sufficient. The use of accelerometry may have value in estimating balance function and minimizing clinical evaluation time.
The purpose of this study was to evaluate the expression of Notch-induced transcription factors (NTFs) HEY1, HES1 and SOX9 in colorectal cancer (CRC) patients to determine their clinicopathologic and ...prognostic significance.
Levels of HEY1, HES1 and SOX9 protein were measured by immunohistochemistry in a nonmalignant and malignant tissue microarray of 441 CRC patients, and the findings correlated with pathologic, molecular and clinical variables.
The NTFs HEY1, HES1 and SOX9 were overexpressed in tumours relative to colonic mucosa (OR=3.44, P<0.0001; OR=7.40, P<0.0001; OR=4.08 P<0.0001, respectively). HEY1 overexpression was a negative prognostic factor for all CRC patients (HR=1.29, P=0.023) and strongly correlated with perineural and vascular invasion and lymph node (LN) metastasis. In 5-fluorouracil (5-FU)-treated patients, the tumour overexpression of SOX9 correlated with markedly poorer survival (HR=8.72, P=0.034), but had no predictive effect in untreated patients (HR=0.70, P=0.29). When HEY1, HES1 and SOX9 expression were combined to predict survival with chemotherapy, in treated patients there was an additive increase in the risk of death with each NTF overexpressed (HR=2.09, P=0.01), but no prognostic import in the untreated patient group (HR=0.74, P=0.19).
The present study is the first to discover that HEY1 overexpression correlates with poorer outcome in CRC, and NTF expression is predictive of CRC patient survival with 5-FU chemotherapy. If confirmed in future studies, testing of NTF expression has the potential to enter routine pathological practice for the selection of patients to undergo chemotherapy alone or in combination with Notch inhibitors.
Footwear outsole design is an important factor for shoe-floor friction and for preventing slipping. Shoes with small, uniformly-separated tread blocks (often included on slip-resistant shoes) have ...decreased slip risk due to their increased friction and better under-shoe fluid drainage. However, these traction performance metrics (friction and fluid drainage) diminish with wear. This study quantifies shoe traction performance in response to natural wear and compares the relationship between common wear metrics: time, distance walked, and worn region size (WRS). Participants wore two pairs of shoes in the workplace for up to 11 months and the distance walked was tracked with a pedometer. After each month of wear, traction performance and WRS of each shoe were measured. Traction performance was quantified by the under-shoe available coefficient of friction and fluid force during a simulated slip test. Increased wear (months worn, distance walked, and WRS) was associated with decreased traction performance. A WRS of 800 mm
2
was associated with reductions in friction of 16-38% and increases in fluid force by 286-528%. Three and six months of wear were associated with WRS values of 251 mm
2
and 462 mm
2
and distances of 203 km and 519 km, respectively. A walking distance of 500 km was associated with a WRS of 406 mm
2
. This study showed that all of these wear metrics are good indicators of shoe traction performance loss. Thus, the most practical metric in a particular application can be selected. We argue that WRS may be the best indicator due to variations in wear rate from the user and environment. Therefore, tracking footwear usage and monitoring outsole wear can aid in shoe replacement recommendations to reduce slips and falls.
Abstract Pregnant women are at an increased risk of experiencing a fall. Numerous anatomical, physiological, and hormonal alterations occur during pregnancy, but the influence of these factors on ...dynamic postural stability has not been explored. The purpose of this study was to examine dynamic postural stability in pregnant women during their second and third trimesters as well as in a group of non-pregnant control women. Methods Eighty-one women (41 pregnant, 40 controls) participated stood on a force plate that translated anteroposteriorly at small, medium, and large magnitudes. Reaction time and center of pressure (COP) movement during the translations were analyzed. Trimester, perturbation direction, and perturbation magnitude were the independent variables in a mixed-model analysis of variance on each of the following dependent variables: reaction time, initial sway, total sway, and sway velocity. Results Reaction time to the perturbation was not significantly different between the groups. Initial sway, total sway, and sway velocity were significantly less during the third trimester than during the second trimester and when compared to the non-pregnant controls ( P <0.05). No differences were found in any of the measures between the pregnant women in their second trimesters and the control group. Conclusion Alterations in sway responses to perturbations are seen in the third trimester in healthy women with uncomplicated pregnancies. Further study is needed to examine the biomechanical and physiological reasons behind this altered dynamic postural stability.
Please cite this paper as: McCrory J, Chambers A, Daftary A, Redfern M. Dynamic postural stability in pregnant fallers and non‐fallers. BJOG 2010;117:954–962.
Objective To compare dynamic postural ...stability in pregnant women who have fallen during their pregnancies with those who have not, and with a group of non‐pregnant women.
Design The study was both longitudinal and cross‐sectional. A cohort of pregnant women were followed through their second and third trimesters. A non‐pregnant control group was used for comparison.
Setting University‐based laboratory.
Population A total of 81 women (41 pregnant and 40 controls) participated. Twenty‐nine pregnant women completed the protocol.
Methods Data were collected on the pregnant women in the middle of their second and third trimesters. Pregnant women were surveyed about their daily activities, exercise participation, and fall history. Postural reaction time and centre of pressure (COP) movement data, in response to translational perturbations, were collected using a force plate. A mixed‐model analysis of variants (ANOVA) was performed on each of the dependent variables (α = 0.05). Chi‐square analysis was performed to determine if exercise participation altered the likelihood of a subject experiencing a fall (α = 0.05).
Main outcome measures Reaction time, initial sway, total sway, and sway velocity.
Results Fifty‐two percent of our pregnant subjects experienced a fall. Initial sway response, total sway, and sway velocity were smaller in the pregnant fallers than in the non‐fallers and control participants (P < 0.05). Thirty‐one of the pregnant subjects participated in regular exercise. Sedentary pregnant women were more likely to experience a fall than those who exercised.
Conclusions Dynamic balance is altered in pregnant women who have fallen compared with non‐fallers and controls. Exercise may play a role in fall prevention in pregnant women.
This study investigated the association between slip severity and pre-slip gait characteristics of younger and older subjects. Sixteen younger and eleven older healthy adults walked onto an ...unexpectedly slippery surface. Slip severity was categorized as either hazardous or non-hazardous using a 1.0 ms peak slip velocity threshold. The results showed that hazardous slips were associated with greater step lengths (normalized by leg length) (SLR), larger and more rapidly changing foot - floor angles (FFA) at heel strike, and increased cadence across the two subject groups. Older subjects were found to walk with shorter SLR and with smaller and more slowly changing FFA at heel strike compared to younger subjects. However, both younger and older subjects experienced hazardous slips at the same rate. A logistic regression model relating SLR and cadence to slip severity predicted that increased SLR and decreased cadence would result in increased probability of hazardous slip (R
2
= 0.45, χ
2
= 15.30, p<0.01). A second logistic regression model relating FFA with slip severity predicted that increased FFA would result in increased probability of hazardous slip (R
2
= 0.53, χ
2
= 16.55, p<0.01). These results suggest that gait characteristics prior to foot contact play an important role in the severity of an ensuing slip. The finding that older adults experienced hazardous slips at the same rate as young adults even though their SLR and FFA are smaller suggests that age is also playing a role in other aspects of postural control that impact slip severity.
•Passive support mode demonstrated its advantages in increased strength of the IPC.•Active support mode decreased the postural sway to a greater extent.•More partnership based methods should be ...considered for balance rehabilitation.•Postural control can be responsive to social factors.
Caregiver–patient interaction relies on interpersonal coordination during support provided by a therapist to a patient with impaired control of body balance.
The purpose of this study was to investigate in a therapeutic context active and passive participant involvement during interpersonal support in balancing tasks of increasing sensorimotor difficulty.
Ten older adults stood in semi-tandem stance and received support from a physical therapist (PT) in two support conditions: 1) physical support provided by the PT to the participant’s back via an instrumented handle affixed to a harness worn by the participant (“passive” interpersonal touch; IPT) or 2) support by PT and participant jointly holding a handle instrumented with a force-torque transducer while facing each other (“active” IPT). The postural stability of both support conditions was measured using the root-mean-square (RMS) of the Centre-of-Pressure velocity (RMS dCOP) in the antero-posterior (AP) and medio-lateral (ML) directions. Interpersonal postural coordination (IPC) was characterized in terms of cross-correlations between both individuals’ sway fluctuations as well as the measured interaction forces.
Active involvement of the participant decreased the participant’s postural variability to a greater extent, especially under challenging stance conditions, than receiving support passively. In the passive support condition, however, stronger in-phase IPC between both partners was observed in the antero-posterior direction, possibly caused by a more critical (visual or tactile) observation of participants’ body sway dynamics by the therapist. In-phase cross-correlation time lags indicated that the therapist tended to respond to participants’ body sway fluctuations in a reactive follower mode, which could indicate visual dominance affecting the therapist during the provision of haptic support.
Our paradigm implies that in balance rehabilitation more partnership-based methods promote greater postural steadiness. The implications of this finding with regard to motor learning and rehabilitation need to be investigated.
Abstract This gait study characterizes the trailing leg's biomechanical response to slips. Twenty-eight healthy participants divided into two age groups (20–33 years and 55–67 years) were asked to ...walk in two conditions: a known dry floor and a glycerol-contaminated floor expected to be dry, inducing an unexpected slip of the leading foot at heel contact. Four slip-related trailing leg response strategies were identified, ranging from a minimal disruption of the swing phase to a premature (∼50 ms after toe off) interruption of the swing phase. Aging effects were minimal. The response of the leading/slipping leg preceded that of the trailing limb. The magnitude of the trailing leg's response was associated with that of the knee in the leading/slipping leg, suggesting interlimb coordination. The corrective moment at the knee of the trailing leg was also correlated with that measured at the hip in the same leg, suggesting intralimb coordination. The specific trailing leg's strategy used in a slip is partially determined by pre-slip walking patterns and early stance slip dynamics.
A significant number of injuries in the workplace is attributed to slips and falls. Biomechanical responses to actual slip events determine whether the outcome of a slip will be recovery or a fall. ...The goal of this study was to examine lower extremity joint moments and postural adjustments for experimental evidence of corrective strategies evoked during slipping in an attempt to prevent falling. Sixteen subjects walked onto a possibly oily vinyl tile floor, while ground reaction forces and body motion were recorded at 350
Hz. The onset of corrective reactions by the body in an attempt to recover from slips became evident at about 25% of stance and continued until about 45% into stance, i.e. on average between 190 and 350
ms after heel contact. These reactions included increased flexion moment at the knee and extensor activity at the hip. The ankle, on the other hand, acted as a passive joint (no net moment) during fall trials. Joint kinematics showed increased knee flexion and forward rotation of the shank in an attempt to bring the foot back towards the body. Once again, the ankle kinematics appeared to play a less dominant role (compared to the knee) in recovery attempts. This study indicates that humans generate corrective reactions to slips that are different than previously reported responses to standing perturbations translating the supporting surface.
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