Determination of the internal piezoelectric potentials and indium concentration in InGaN based quantum wells grown on relaxed InGaN pseudo-substrates by off-axis electron holography

Micro light emitting diodes have been grown by metal organic vapor phase epitaxy on standard GaN and partly relaxed InGaNOS substrates with the purpose of incorporating higher concentrations of indium for identical growth conditions. Green emission has been demonstrated at wavelengths of 500 nm for the GaN template and 525 and 549 nm for the InGaNOS substrates, respectively. The structure, deformation, indium concentration and piezoelectric potentials have been measured with nm-scale spatial resolution in the same specimens by transmission electron microscopy. We show by off-axis electron holography that the piezoelectric potential and information about the indium concentration from the mean inner potential are obtained simultaneously. By separating the components using a model, we show that for higher concentrations of indium in the quantum wells (QWs) grown on InGaNOS substrates, the piezoelectric potentials are reduced. The measurements of the indium concentrations by electron holography have been verified by combining energy dispersive x-ray spectrometry, x-ray diffraction and from the tensile deformation made by precession electron diffraction. A discussion of the limitations of these advanced aberration-corrected transmission electron microscopy techniques when applied to nm-scale QW structures is given.

Functional outcomes in adult patients with herpes simplex encephalitis admitted to the ICU: a multicenter cohort study

PURPOSE

We aimed to study the association of body temperature and other admission factors with outcomes of herpes simplex encephalitis (HSE) adult patients requiring ICU admission.

METHODS

We conducted a retrospective multicenter study on patients diagnosed with HSE in 47 ICUs in France, between 2007 and 2017. Fever was defined as a body temperature higher or equal to 38.3 °C. Multivariate logistic regression analysis was used to identify factors associated with poor outcome at 90 days, defined by a score of 3-6 (indicating moderate-to-severe disability or death) on the modified Rankin scale.

RESULTS

Overall, 259 patients with a score on the Glasgow coma scale of 9 (6-12) and a body temperature of 38.7 (38.1-39.2) °C at admission were studied. At 90 days, 185 (71%) patients had a poor outcome, including 44 (17%) deaths. After adjusting for age, fever (OR = 2.21; 95% CI 1.18-4.16), mechanical ventilation (OR = 2.21; 95% CI 1.21-4.03), and MRI brain lesions > 3 lobes (OR = 3.04; 95% CI 1.35-6.81) were independently associated with poor outcome. By contrast, a direct ICU admission, as compared to initial admission to the hospital wards (i.e., indirect ICU admission), was protective (OR = 0.52; 95% CI 0.28-0.95). Sensitivity analyses performed after adjustment for functional status before admission and reason for ICU admission yielded similar results.

CONCLUSIONS

In HSE adult patients requiring ICU admission, several admission factors are associated with an increased risk of poor functional outcome. The identification of potentially modifiable factors, namely, elevated admission body temperature and indirect ICU admission, provides an opportunity for testing further intervention strategies.

In Vitro Inhibition of Platelet Aggregation by Bile Salts

In a series of in vitro experiments, the influence of bile salts on platelet aggregation by ADP or by collagen and on serotonin-14C release by collagen, was studied.

Sodium salts of the following bile acids showed a clear inhibitory effect: glycochenodeoxycholic acid, taurochenodeoxycholic acid, glycocholic acid, taurocholic acid and cholic acid. Lowering the pH of the platelet-rich plasma resulted in decreased platelet aggregation by ADP and by collagen. Bile salts further enhanced the inhibitory effect of pH change. In contrast the sodium salt of chenodeoxycholic acid was the sole aggregation inducing bile salt we studied. Relating the above studies to the clinical situation of upper gastroduodenal mucosal haemorrhage, we suggest that biliary reflux as well as the acidic environment may contribute to a poor haemostatic response by impaired platelet aggregation in the upper gastrointestinal tract of otherwise normal human subjects.

Inhibitory Effect of Acetylsalicylic Acid on Human Platelet Function in Normal Volunteers and in Women Using a Combined Oral Contraceptive Regime

Six parameters related to the release reaction were measured simultaneously in 10 human volunteers prior to the intake of one single dose of 1 g acetylsalicylic acid and 1, 4, 5, 6 and 7 days later: ΔE5 with diluted collagen, ΔE10 with Thrombofax® and the serotonin-14C release by undiluted and diluted collagen, by Thrombofax and by bovine plasma. The duration of the inhibitory effect varied according to the test used. It was the most prolonged (through the 7th day) if serotonin-14C release by diluted collagen was measured.

A systematic investigation of the platelet release reaction in women taking a combined oral contraceptive was also performed. There were no statistically significant differences from a control group. No difference in acetylsalicylic acid sensitivity, measured 24 hours after intake of 1 g of aspirin, could be demonstrated.

Limitations of the Activated Partial Thromboplastin Time for Determination of Plasma Heparin Concentration and Half-Life in Human Subjects

In vivo heparin concentrations and half-life were estimated in 20 human subjects, after a single intravenous injection.

The method, used for heparin determination, is based on the activated partial thromboplastin time. The test plasmas are diluted in plasma of the same subject obtained before heparin administration. In this way the heparin concentrations are reduced to measurable levels between 0.1 I. U./ml and 0.8 I. U./ml. Indeed a linear relationship between log activated partial thromboplastin time and heparin concentrations from 0.1 to 0.8 I. U./ml can be computed. Different half-lives were found in 13 of the 20 subjects examined when different dilution factors were used. This seems an important limitation for the examination of the pharmacokinetics of heparin.

A simple ultra-high-performance liquid chromatography-high resolution mass spectrometry assay for the simultaneous quantification of 15 antibiotics in plasma

Antibiotic (ATB) treatment of critically ill patients with pathophysiological injuries remains a challenge due to the constant increase in antimicrobial resistance. Therapeutic drug monitoring (TDM) is advised for ATB dose adjustments to avoid suboptimal concentrations and dose-related adverse effects. Therefore, a single and reliable analytical method for a broad selection of ATBs was developed using a high-resolution mass spectrometry (HRMS) platform for frequent use in intensive care units. An UHPLC assay coupled to high resolution accurate mass acquisition has been developed for the quantification of penicillins (amoxicillin, oxacillin, piperacillin, and ticarcillin), cephalosporines (cefepime, cefotaxime, ceftazidime, and ceftriaxone), carbapenems (ertapenem, imipenem, and meropenem), lincosamide (clindamycin), quinolones (ofloxacin and ciprofloxacin) and tazobactam. Plasma samples (100μL) were spiked with an internal standard solution followed by protein precipitation. Separation was achieved on an Accucore C18 column, which enabled sample analysis every 9min. All compounds were detected in electrospray positive ion mode and quantified with a linear regression between 0.5 and 32mg/L (r2>0.998). Overall precision and accuracy did not exceed 15%. No significant matrix effect was observed for the studied ATBs. Stored stock solutions at -20°C were stable for 6 months, except for amoxicillin and imipenem. Analytes in plasma were stable for 24h under ambient conditions as well as in post-preparation in an autosampler, except for amoxicillin and imipenem. This HRMS assay provides the simultaneous quantification of 15 ATB; it fulfills the usual quality criteria and was successfully applied for routine TDM of ATBs. The method is based on a full scan acquisition, and it would be easy to add other compounds to the present panel in the future, as this assay has already been proven to be efficient for different classes of compounds.

Initiation of forward gait with lateral occurrence of emotional stimuli: general findings and relevance for pedestrians crossing roads

With reference to theoretical models regarding links between emotions and actions, the present study examined whether the lateral occurrence of an emotional stimulus influences spatial and temporal parameters of gait initiation in 18 younger and 18 older healthy adults. In order to simulate road-crossing hazard for pedestrians, slides of approaching cars were used and they were presented in counterbalanced order with threatening slides from the International Affective Picture System (IAPS) and control slides of safe walking areas. Each slide was presented on the left side of the participant once the first step was initiated. The results evidenced medio-lateral shifts to the left for the first step (right foot) and to the right for the second step (left foot). These shifts were both modulated by the slide contents in such a way that the resulting distance between the screen and the foot (right or left) was larger with the IAPS and traffic slides than with the control slides. The slides did not affect the base of support, step length, step velocity and time of double support. Advancing age influenced the subjective impact of the slides and gait characteristics, but did not modulate medio-lateral shifts. The data extend evidence of fast, emotional modulation of stepping, with theoretical and applied consequences.

Determination of toxic elements (mercury, cadmium, lead, tin and arsenic) in fish and shellfish samples. Risk assessment for the consumers

Although fish intake has potential health benefits, the presence of metal contamination in seafood has raised public health concerns. In this study, levels of mercury, cadmium, lead, tin and arsenic have been determined in fresh, canned and frozen fish and shellfish products and compared with the maximum levels currently in force. In a further step, potential human health risks for the consumers were assessed. A total of 485 samples of the 43 most frequently consumed fish and shellfish species in Andalusia (Southern Spain) were analyzed for their toxic elements content. High mercury concentrations were found in some predatory species (blue shark, cat shark, swordfish and tuna), although they were below the regulatory maximum levels. In the case of cadmium, bivalve mollusks such as canned clams and mussels presented higher concentrations than fish, but almost none of the samples analyzed exceeded the maximum levels. Lead concentrations were almost negligible with the exception of frozen common sole, which showed median levels above the legal limit. Tin levels in canned products were far below the maximum regulatory limit, indicating that no significant tin was transferred from the can. Arsenic concentrations were higher in crustaceans such as fresh and frozen shrimps. The risk assessment performed indicated that fish and shellfish products were safe for the average consumer, although a potential risk cannot be dismissed for regular or excessive consumers of particular fish species, such as tuna, swordfish, blue shark and cat shark (for mercury) and common sole (for lead).

The "Swiss Statement": who knows about it? How do they know? What are its effects on people living with HIV/AIDS?

The publication of the "Swiss Statement" in 2008 shook the international HIV prevention and advocacy scene. HIV behavioral research has provided us with some studies focusing on the potential changes that new prevention strategies can produce, but results are not conclusive. Besides, there is a lack of data concerning awareness of these kinds of prevention strategies on real-life settings, studying mainly the behavior of people recruited in different types of trials (e.g., circumcision, pre and post-exposure prophylaxis). The present study aims to (1) identify the factors associated with awareness of the "Swiss Statement" among PLWHA, (2) determine in which setting they became aware of it, and (3) look for potential, behavioral, and/or emotional changes as a consequence of this awareness. In order to achieve these three objectives, we used the data collected by a community-based survey called "HIV, Hepatitis and you." In order to determine the factors associated with the awareness of the Swiss Statement, univariate and multivariate logistic regression were performed. Main results show that among the 997 HIV-positive people answering the questionnaire, 57% knew about the Swiss Statement, and that their main source of information was the associative setting, while 30% declared having found out about it from their doctor. As for the factors associated with the awareness of the Swiss Statement, we found that the following variables were significantly associated with such awareness: living in stable housing, having a CD4 count above 350 cell/mm(3), having an undetectable viral load, being in contact with a HIV-solidarity network, feeling of belonging to the LGBT community, and filling out the questionnaire online. The results of this study point out that interventions addressed to improve access to health-related information for PLWHA facing socioeconomical difficulties and isolation are strongly needed.

Secular trends and dynamics of hospital associated methicillin-resistant Staphylococcus aureus

We performed an 11-year retrospective analysis of consecutive nonduplicate methicillin-resistant Staphylococcus aureus (MRSA) clinical isolates in two neighbouring hospitals in the Paris area. MRSA isolates were classified according to resistance (R) to fluoroquinolones (Fq), kanamycin (K), tobramycin (T) and gentamicin (G). The yearly number of MRSA isolates (3446 in total) decreased, from approximately 350 in 1997–2002 to 212 in 2007. Four patterns (P) were found: P1 (KTGFq R, n = 776), P2 [KTFq R; G susceptible (S), n = 1630], P3 (Fq R; KTG S, n = 397) and P4 (Fq S; any KTG susceptibility, n = 201). P1 predominated in 1997 (183 isolates) then dropped sharply (nine in 2007); P2 and P4 remained stable over time; and P3 increased from 13 isolates in 1997 to 72 in 2007. Patterns were significantly and positively associated with several variables, independently of the year of collection: P1, age < 80 years, male gender, intensive care unit stay, and hospital onset; P3, age > 80 years and stay in intermediate or long-term care wards; and P4, age < 40 years, stay in an obstetric ward, and imported cases. Molecular typing of 79 isolates in 2005 and 2007 using multilocus sequence typing, spa type, and SCCmec showed that P1, P2 and P3 isolates were mainly clonal, whereas P4 isolates were more diverse. P1 comprised mainly ST247-I isolates, P2 mainly ST8-IVc, and P3 mainly ST8-IVc and ST5-VI. In conclusion, the epidemiology of MRSA in Paris is changing rapidly at the local level, with phenotypically defined clones being substituted by others, with associations existing between changes in specific patient populations or circumstances.

Genesis of a KPC-producing Klebsiella pneumoniae after in vivo transfer from an imported Greek strain

We document here the in vivo transfer of bla(KPC-2) between intensive care unit-acquired and a commensal strain of K. pneumoniae in a French patient after his repatriation from Greece. This first report of an emerging KPC-producing strain in France raises further concerns about the spread of carbapenem resistance among Enterobacteriaceae.

Effect of trunk inclination on lower limb joint and lumbar moments in able men during the stance phase of gait

BACKGROUND

Though the effect of imposed trunk posture affects walking patterns little is known about the effect of natural orientation of the trunk on gait. The objectives of this study are to test if the lower limb joint and thoraco-lumbar moments are similar in subjects who maintain an average natural forward or backward trunk inclination during gait and verify if the lower limbs are equally affected.

METHODS

Twenty-five young men were divided according to their natural backward or forward trunk inclination during level walking. Ankle, knee, hip and thoraco-lumbar moments were calculated by an inverse dynamic approach for the two limbs. A two-way ANOVA was performed on peak lower limb moments. A one-way ANOVA was performed on thoraco-lumbar peak moments.

FINDINGS

There was a main effect for both trunk inclinations and lower limb sides but no interaction. For the forward leaners, the duration of hip extension moment was longer (P<0.001) while the hip flexion moment was 1.3 times smaller (P<0.001). Differences between the lower limb sides were noted in all joints but at push-off of the stance phase only. The two thoraco-lumbar extension moments were, respectively, 1.4 times higher for the forward leaners while the two flexion moments were approximately 1.4 times higher for the backward leaners.

INTERPRETATIONS

The backward leaners propel themselves with a strong hip flexor activity at push-off while the forward leaners use their hip muscles throughout stance. These results support the idea that trunk inclinations and moment variations are associated with the type of walking patterns.

Heat-treated Saccharomyces cerevisiae for antimony speciation and antimony(III) preconcentration in water samples

An analytical method was developed for antimony speciation and antimony(III) preconcentration in water samples. The method is based on the selective retention of Sb(III) by modified Saccharomyces cerevisiae in the presence of Sb(V). Heat, caustic and solvent pretreatments of the biomass were investigated to improve the kinetics and thermodynamics of Sb(III) uptake process at room temperature. Heating for 30 min at 80 degrees C was defined as the optimal treatment. Antimony accumulation by the cells was independent of pH (5-10) and ionic strength (0.01-0.1 mol L(-1)). 140 mg of yeast and 2h of contact were necessary to ensure quantitative sequestration of Sb(III) up to 750 microg L(-1). In these conditions, Sb(V) was not retained. Sb(V) was quantified in sorption supernatant by inductively coupled plasma mass spectrometry (ICP-MS) or inductively coupled plasma optical emission spectrometry (ICP-OES). Sb(III) was determined after elution with 40 mmol L(-1) thioglycolic acid at pH 10. A preconcentration factor close to nine was achieved for Sb(III) when 100mL of sample was processed. After preconcentration, the detection limits for Sb(III) and Sb(V) were 2 and 5 ng L(-1), respectively, using ICP-MS, 7 and 0.9 microg L(-1) using ICP-OES. The proposed method was successfully applied to the determination of Sb(III) and Sb(V) in spiked river and mineral water samples. The relative standard deviations (n=3) were in the 2-5% range at the tenth microg L(-1) level and less than 10% at the lowest Sb(III) and Sb(V) tested concentration (0.1 microg L(-1)). Corrected recoveries were in all cases close to 100%.

Speciation of selenium in a commercial dietary supplement by liquid chromatography coupled with inductively coupled plasma-mass spectrometry (ICP-MS)

Size exclusion and anion-exchange chromatographies coupled with inductively coupled plasma-mass spectrometry (ICP-MS) were used for the speciation of selenium (Se) in a dietary supplement. A sequential extraction method resulted in 85% recovery of Se and 78% of the Se extracted could be identified. The results obtained show that selenomethionine and its oxide are the predominant compounds, while selenite and selenomethylcysteine are present at low concentrations. Methane seleninic acid, probably arising from the oxidation of selenomethylcysteine, accounted for 22% of total Se. High-molecular-weight compounds, probably proteins, were detected in sodium dodecyl sulfate (SDS) and driselase extracts by size exclusion chromatography.

Extracellular Production of Hydrogen Selenide Accounts for Thiol-assisted Toxicity of Selenite against Saccharomyces cerevisiae

Administration of selenium in humans has anticarcinogenic effects. However, the boundary between cancer-protecting and toxic levels of selenium is extremely narrow. The mechanisms of selenium toxicity need to be fully understood. In Saccharomyces cerevisiae, selenite in the millimolar range is well tolerated by cells. Here we show that the lethal dose of selenite is reduced to the micromolar range by the presence of thiols in the growth medium. Glutathione and selenite spontaneously react to produce several selenium-containing compounds (selenodiglutathione, glutathioselenol, hydrogen selenide, and elemental selenium) as well as reactive oxygen species. We studied which compounds in the reaction pathway between glutathione and sodium selenite are responsible for this toxicity. Involvement of selenodiglutathione, elemental selenium, or reactive oxygen species could be ruled out. In contrast, extracellular formation of hydrogen selenide can fully explain the exacerbation of selenite toxicity by thiols. Indeed, direct production of hydrogen selenide with D-cysteine desulfhydrase induces high mortality. Selenium uptake by S. cerevisiae is considerably enhanced in the presence of external thiols, most likely through internalization of hydrogen selenide. Finally, we discuss the possibility that selenium exerts its toxicity through consumption of intracellular reduced glutathione, thus leading to severe oxidative stress.

New separation method for organic and inorganic selenium compounds based on anion exchange chromatography followed by inductively coupled plasma mass spectrometry

We describe a new method for separating the organic and inorganic selenocompounds methaneseleninic acid, selenite, selenate, methylselenocysteine, selenocystine as well as both selenomethionine and its oxidized form. The separation is performed on a Hamilton PRP-X100 column. According to the literature, the oxidized form of selenomethionine-which is easily formed-is eluted close to the dead volume when this column is used. The choice of parahydroxybenzoic acid as mobile phase enabled us to elute all of these species after this oxidized form, resulting in better identification and quantification. The factors determining separation (eluent concentration, pH, gradient) were optimized via an experimental design. Application of the method to yeast and commercial tablets showed that the principal Se compound present was selenomethionine, which was also present in its oxidized form.

Economic bismuth-film microsensor for anodic stripping analysis of trace heavy metals using differential pulse voltammetry

Stripping analysis has been widely recognised as a powerful tool in trace metal analysis. Its remarkable sensitivity is attributed to the combination of a preconcentration step coupled with pulse measurements that generate an extremely high signal-to-background ratio. Mercury-based electrodes have traditionally been used to achieve high reproducibility and sensitivity in the stripping technique. Because of the toxicity of mercury, however, new alternative electrode materials are highly desired, particularly for on-site monitoring. Use of thin films of bismuth deposited on platinum or glassy-carbon substrates has recently been proposed as a possible alternative to mercury--bismuth is "environmentally friendly", of low toxicity, and is in widespread pharmaceutical use. In this paper the preparation of economic bismuth-film microelectrodes by electrodeposition on a copper substrate and their application to heavy metal analysis are described. Bismuth-film electrodes were prepared by potentiostatic electrodeposition. Optimum conditions for chemical and electrochemical deposition to obtain an adherent, reproducible, and robust deposit were determined. The suitability of such microelectrodes for analysis of heavy metals was evaluated by anodic stripping voltammetry of cadmium. The analytical performance of bismuth-film electrodes for anodic stripping voltammetry of heavy metals was evaluated for non-deaerated solutions containing Cd2+, Pb2+, and Zn2+ ions. Well-defined peaks with low background current were obtained by use of differential pulse voltammetry. Linear calibration plots were obtained for Cd2+ in acidified tap water at concentrations ranging from 2 x 10(-8) to 1 x 10(-7) mol L(-1) and from 1 x 10(-7) to 1 x 10(-6) mol L(-1) with relative standard deviations of 5% (n = 15) at the 1 x 10(-7) mol L(-1) level. The method was then successfully used to monitor the Cd2+ content of plant extracts and validated by polarographic and ICP-MS measurements. These results open the possibility of using bismuth-coated copper electrodes as an alternative to mercury-based electrodes for analysis of heavy metals. The main problem remaining, which prevents on-site monitoring of heavy metals, is the need to use slightly acidic media, because formation of bismuth hydroxide on the film surface above pH 4.3 leads to non-reproducible measurements. Further experiments will be performed to discover whether electrode conditioning can be used to enable reproducible measurement in on-site monitoring of cadmium in natural waters. Moreover, further study should be conducted to evaluate the potential of BiFE for analysis of several pollutants of interest that are usually determined electrochemically by using mercury-based electrodes.

[Coasting and ovarian stimulation protocols in high-responder patients undergoing assisted conception]

Over-responsive patients are at risk of ovarian hyperstimulation, which may lead to severe complications. The choice of ovarian stimulation protocol or the use of a coasting (gonadotrophins suspension) with its associated risk of too strong ovarian response will be discussed herein. As for in vitro fertilization stimulation protocols, the best are probably those which use steadily increasing low doses of gonadotrophins, associated to GnRH agonists (low-dose protocols) or those which complete a double hypophyseal inhibition (estro-progestative association and GnRH agonists). GnRH antagonists may also reduce the risk of ovarian hyperstimulation, by estradiol drop. Outside the context of in vitro fertilization GnRH continuous administration or low -dose gonadotrophin stimulation are the best options. A coasting will be performed when an excess follicle response is documented. Under strict hormonal follow-up and within four days it allows achieving a high rate of pregnancy with a lower risk of hyperstimulation. Compared to other therapies of hyperstimulation syndrome, the coasting allows to avoid cycle cancellation or freezing of all embryos.

Effect of Body Morphology on Standing Balance in Adolescent Idiopathic Scoliosis

OBJECTIVES

The objective of this study was to determine the effect of body somatotype on standing balance in girls with adolescent idiopathic scoliosis (AIS) who are under observation but not wearing a body brace.

DESIGN

In all, 74 girls participated in this study to form the able-bodied (n = 36) and the AIS (n = 38) groups, having an average age of 13 yrs. Quiet standing balance was tested using a force platform. Afterward, subjects in each group were divided according to their dominant body somatotype, namely endomorphs (fatness), mesomorphs (muscular), or endomorphic ectomorphs (lean).

RESULTS

The center of pressure measured in the anteroposterior position was closer to the heels for the AIS ectomorphic group by approximately 14 mm (P = 0.00497). Only the AIS mesomorphic group displayed a statistically significant 12-mm shift to the right in their center of pressure (P = 0.01211) compared with the able-bodied girls of the same morphotype. In the endomorphic group, the sway area was statistically higher for the scoliotic subjects (P = 0.00839). The distances traveled by the AIS subjects were all statistically longer for all three body morphologic somatotypes.

CONCLUSION

Different postural responses seem to be dependent on body somatotypes. The endomorphic AIS girls had a larger sway area than their able-bodied counterparts while maintaining a similar center of pressure position. The AIS ectomorphic girls had a tendency to lean further back than a comparable able-bodied group. This could be emphasizing a hypokyphotic trunk attitude and increasing the risk of spinal deformity progression. The AIS mesomorphic subjects characterized by a large muscular and bony structure had a tendency to position their center of mass more to their right, indicating less postural adaptability and a stiffer trunk.

Main functional roles of knee flexors/extensors in able-bodied gait using principal component analysis (I)

This study was undertaken to demonstrate how principal component analysis (PCA) can be used to detect the main functional structure of actions taken by knee flexors/extensors during able-bodied gait. PCA was applied as a classification and curve structure detection method for knee sagittal muscle moment developed during walking of 20 young, healthy male subjects. Over 90% of the information provided by the first three principal components (PCs) was chosen for further biomechanical interpretation. PCA was able to identify the three main functional contributions of knee sagittal muscle moment during able-bodied gait, namely control balance, foot clearance/limb preparation and shock absorption.

Gait pattern classification of healthy elderly men based on biomechanical data

OBJECTIVES

To distinguish the gait patterns of young subjects from those of elderly men using three-dimensional (3D) gait data, to determine if elderly subjects displayed other than a typical gait pattern, and to identify which parameters best describe them.

DESIGN

Nonrandomized study in which video and force plate data were collected at the subject's own free walking speed and used in a 3D inverse dynamic model. Cluster analysis was chosen to identify the gait families, and analyses of variance were performed to determine which parameters were different.

SETTING

A gait laboratory.

PARTICIPANTS

The sample of convenience involved a single but mixed group consisting of 16 able-bodied elderly subjects (mean age, 62yrs) and 16 able-bodied young subjects aged between 20 and 35 years.

MAIN OUTCOME MEASURES

Phasic and temporal gait parameters, as well as the 3D muscle powers developed in the joints of the right lower limb during the gait cycle.

RESULTS

The walking patterns in elderly subjects were found to be different from those of the young adults. Three elderly gait families or groups forming a specific gait pattern were identified, and differences were found in the phasic and temporal parameters as well as in 6 peak muscle powers. Four of the peak powers occurred in the sagittal plane, and half of them were related to the hip.

CONCLUSIONS

Biomechanical parameters can be used to classify the gait patterns of young and elderly men using cluster analysis rather than age alone. The muscle powers in elderly subjects are perturbed throughout the gait cycle and not only at push-off. It appears that the plane in which the peak powers occurred was related to their occurrence in the gait cycle. Variability in the gait patterns of elderly subjects could reflect natural adaptations or compensations. These should not be indicative of a deficient gait or be misconstrued as some age-related pathology.