Spatial Contextual Information Modulates Affordance Processing and Early Electrophysiological Markers of Scene Perception.

Scene perception allows humans to extract information from their environment and plan navigation efficiently. The automatic extraction of potential paths in a scene, also referred to as navigational affordance, is supported by scene-selective regions (SSRs) that enable efficient human navigation. Recent evidence suggests that the activity of these SSRs can be influenced by information from adjacent spatial memory areas. However, it remains unexplored how this contextual information could influence the extraction of bottom-up information, such as navigational affordances, from a scene and the underlying neural dynamics. Therefore, we analyzed ERPs in 26 young adults performing scene and spatial memory tasks in artificially generated rooms with varying numbers and locations of available doorways. We found that increasing the number of navigational affordances only impaired performance in the spatial memory task. ERP results showed a similar pattern of activity for both tasks, but with increased P2 amplitude in the spatial memory task compared with the scene memory. Finally, we reported no modulation of the P2 component by the number of affordances in either task. This modulation of early markers of visual processing suggests that the dynamics of SSR activity are influenced by a priori knowledge, with increased amplitude when participants have more contextual information about the perceived scene. Overall, our results suggest that prior spatial knowledge about the scene, such as the location of a goal, modulates early cortical activity associated with SSRs, and that this information may interact with bottom-up processing of scene content, such as navigational affordances.

Effects of muscular and mental fatigue on spatiotemporal gait parameters in dual task walking in young, non-frail and frail older adults.

BACKGROUND: Dual-task (DT) walking is of great interest in clinical evaluation to evaluate frailty or cognitive declines in older adults. Frail older adults are known to adopt different walking strategy to overcome fatigue. However, no studies evaluated the effect of muscular or mental fatigue on dual-task walking strategy and the difference between frail and non-frail older adults. AIMS: Evaluate the effect of mental and muscular fatigue on spatio-temporal parameters in dual-task walking in young, non-frail and frail older adults. METHODS: 59 participants divided into 20 young (Y) (24.9 ± 3 years old), 20 non-frail (NF) (75.8 ± 4.9 years old) and 19 frail older adults (F) (81 ± 4.7 years old) performed single-task (ST) walking, single-task cognitive (serial subtraction of 3), and dual-task (subtraction + walking) for 1 min at their fast pace. Gait speed, step length, step length variability, stance and swing phase time, single and double support time, cadence, gait speed variability were recorded in single- and dual-task walking. The dual-task effect (DTE) was calculated as ((DT - ST)/ST) × 100). Generalized linear mixed models (GLMM) were used to compare the effects of mental and muscular fatigue on gait and cognitive variables between the groups. RESULTS: The DTE walking parameters were worse in F compared to NF or Y but no significant effect of fatigue were highlighted except for swing time and single support time DTEs. CONCLUSIONS: The results were mitigated but a clear difference in dual-task spatio-temporal parameters was found between F and NF which brings hope into the capacity of DT to better reveal frailty.

Validation of 3D Knee Kinematics during Gait on Treadmill with an Instrumented Knee Brace.

To test a novel instrumented knee brace intended for use as a rehabilitation system, based on inertial measurement units (IMU) to monitor home-based exercises, the device was compared to the gold standard of motion analysis. The purpose was to validate a new calibration method through functional tasks and assessed the value of adding magnetometers for motion analysis. Thirteen healthy young adults performed a 60-second gait test at a comfortable walking speed on a treadmill. Knee kinematics were captured simultaneously, using the instrumented knee brace and an optoelectronic camera system (OCS). The intraclass correlation coefficient (ICC) showed excellent reliability for the three axes of rotation with and without magnetometers, with values ranging between 0.900 and 0.972. Pearson's r coefficient showed good to excellent correlation for the three axes, with the root mean square error (RMSE) under 3° with the IMUs and slightly higher with the magnetometers. The instrumented knee brace obtained certain clinical parameters, as did the OCS. The instrumented knee brace seems to be a valid tool to assess ambulatory knee kinematics, with an RMSE of <3°, which is sufficient for clinical interpretations. Indeed, this portable system can obtain certain clinical parameters just as well as the gold standard of motion analysis. However, the addition of magnetometers showed no significant advantage in terms of enhancing accuracy.

How fiber dynamics of plantarflexor and dorsiflexor muscles based on EMG-driven approach can explain the metabolic cost at different gait speeds.

PURPOSE: The aim of this study was to investigate the fiber dynamics of plantarflexor and dorsiflexor muscles and their association with the net metabolic rate (NCw). METHODS: Metabolic, kinematic, kinetic, and electromyography measurements were made on seven young subjects while they walked on a force-plate instrumented treadmill at 1.00, 1.20, 1.40, 1.60, and 1.8 m/s for 1:30 min. The net metabolic rate was computed, and a one degree-of freedom EMG-driven approach was used to extract the force generation ability (Fability), and active force-length (fAL) and force-velocity (fV) multiplier of each muscle. A one-way (speeds) repeated measures ANOVA was performed for each muscle and a multiple linear regression model was used to explain NCw. RESULTS: Fability was significantly affected by gait speed for the GasMed and the SOL muscles. The decrease of Fability for the SOL and the GasMed was accompanied by a decrease in the force-velocity multiplier. The peak muscle force for the SOL increased for the lowest speed compared to the higher speed, and for the TibAnt increased at high speed compared to low speed. In addition, Fability fAL, and fV of the SOL predicted over 58% of NCw and FMax of the TibAnt accounts for 39.9% of the variance in NCw. CONCLUSION: The increase of NCw with gait speed over the preferred walking speed can be partially explained by the decreasing capacity of the SOL muscle to produce muscle force and more specifically by the force-velocity relationship and an increase in muscle force for the TibAnt.

Apathetic patients with neurocognitive disorders are more fatigued and fatigable.

BACKGROUND: Apathy is common in neurocognitive disorders (NCD) and manifests as reduced goal-directed behaviors and activities. A decrease in everyday activities can also be due to fatigue, another common symptom in NCD. The aim of this study was to investigate if apathetic patients with NCD are more fatigued and more fatigable. METHOD: A self-report questionnaire and clinical functional tests assessed fatigue and fatigability in 30 apathetic vs 26 non-apathetic NCD participants. The Fatigue Severity Scale (FSS) was administered and a 15-s sustained maximal handgrip contraction and a 6-min walk test (6MWT) were performed. RESULTS: Apathetic subjects had higher FSS scores. A decrease in performance was observed in apathetic participants during the sustained maximal handgrip contraction but not the 6MWT. CONCLUSION: Higher self-reported fatigue and greater fatigability during the sustained maximal handgrip contraction test in apathetic subjects suggest the importance of assessing these symptoms in apathetic subjects to properly guide treatment. CLINICAL TRIAL REGISTRATION: NCT04573712.

Sonoelastography to Assess Muscular Stiffness Among Older Adults and its Use for the Diagnosis of Sarcopenia: A Systematic Review.

Changes in muscle stiffness have been reported with sarcopenia. Sonoelastography is an accessible and non-radiating imaging technique allowing quantification of elastic properties of tissue. We performed a systematic review of the literature to investigate whether sonoelastography can be a reliable method to assess sarcopenia in older patients. We searched Medline, Google Scholar, Scopus, SpringerLink and Science direct from January 1, 1990 to April 1, 2020. Three independent review authors assessed trial eligibility, extracted the data, and assessed risk of bias. We intended to learn which types of elastography have been tested, if such measures are repeatable, and if they have been compared to the currently accepted diagnostic method. Ten studies met the inclusion criteria. Most followed a cross-sectional design with young and older adult subgroups. The gastrocnemius, rectus femoris, and vastus intermedius appeared most frequently. Nine of the included studies used shear wave elastography and one-strain elastography. The passive elastic constant was significantly greater in sarcopenic versus healthy subjects after passive stretching (124.98 ±â€Š60.82 vs. 46.35 ± 15.85, P = 0.004). However, even in non-sarcopenic patients, the age of the patient was responsible for about 45.5 % of the variance in SWV. Among ten included articles, four reported higher stiffness in the muscles of older adults, two reported lower stiffness, and four found no significant difference. Due to the substantial heterogenicity of actual data, we could not make any conclusions about the potential usefulness of elastography to assess sarcopenia. Further studies are needed, including a larger sample of older patients and using a standardized and reproducible protocol.

"Men are Better Than Women!" The Positive Effect of a Negative Stereotype Toward Women on a Self-Paced Cycling Exercise.

Previous research on the stereotype threat phenomenon has shown that inducing a negative stereotype toward a group debilitates motor performance despite the increase in motivation. Most of the studies focused on tasks requiring technical skills. However, what happens when the task does not require technical skills but focuses on energy expenditure? To examine this question, 34 male and female participants were assigned to a negative stereotype toward women and a nullified-stereotype condition and performed 20 min of self-paced cycling exercise. The authors hypothesized better performances when participants were assigned to the negative stereotype toward women condition than when assigned to the nullified-stereotype condition. As predicted, men and women increased their performances, accompanied by increases in heart rate. Concerning women, this result provides support for the notion that the effect of inducing a negative stereotype is task dependent, but further research is needed to more deeply investigate the mechanisms involved.

Fatigability in Patients With Multiple Sclerosis During Maximal Concentric Contractions.

OBJECTIVE: To compare quadriceps fatigability during maximal concentric contractions in persons with multiple sclerosis (MS) and healthy subjects. DESIGN: Observational study. SETTING: Hospital rehabilitation department. PARTICIPANTS: Persons with MS (n=38) and healthy subjects (n=14) were included (N=52). Torque of the knee flexor and extensor muscles and fatigability of the knee extensor muscles were evaluated using an isokinetic device. Surface electromyographic activity of the rectus femoris, vastus lateralis, biceps femoris, and semitendinosus muscles was recorded. INTERVENTIONS: None. MAIN OUTCOME MEASURE: Muscle fatigability (torque fatigue index). RESULTS: The torque fatigue index was lower in persons with MS than in healthy subjects, but when torque was normalized to maximal isometric peak torque, persons with MS and healthy subjects finished the fatigue protocol at exactly the same level of relative strength (50% of the maximal isometric peak torque). Moreover, the reduction in torque was primarily because of a reduction in neuromuscular efficiency, with no changes of coactivation of antagonist muscles. CONCLUSIONS: Although fatigue is a disabling symptom of MS, persons with MS develop less muscle fatigability than healthy subjects during repeated maximal concentric contractions, but they end up at the same level of relative strength.

Effect of a robotic restraint gait training versus robotic conventional gait training on gait parameters in stroke patients.

Kinematic and kinetic gait parameters have never been assessed following robotic-assisted gait training in hemiparetic patients. Previous studies suggest that restraint of the non-paretic lower limb during gait training could be a useful rehabilitation approach for hemiparetic patients. The aim of this study is to compare a new Lokomat(®) asymmetrical restraint paradigm (with a negative kinematic constraint on the non-paretic limb and a positive kinematic constraint on the paretic limb) with a conventional symmetrical Lokomat(®) training in hemiparetic subjects. We hypothesized that hip and knee kinematics on paretic side would be more improved after the asymmetrical Lokomat(®) training than after the conventional training. In a prospective observational controlled study, 26 hemiparetic subjects were randomized to one of the two groups Lokomat(®) experimental gait training (LE) or Lokomat(®) conventional gait training (LC). They were assessed using 3D gait analysis before, immediately after the 20 min of gait training and following a 20-min rest period. There was a greater increase in peak knee flexion on the paretic side following LE than LC (p = 0.04), and each type of training induced different changes in vertical GRF during single-support phase on the paretic side. Several other spatiotemporal, kinematic and kinetic gait parameters were similarly improved after both types of training. Lokomat(®) restrained gait training with a negative kinematic constraint on the non-paretic limb and a positive kinematic constraint on the paretic limb appears to be an effective approach to specifically improve knee flexion in the paretic lower limb in hemiparetic patients. This study also highlights spatiotemporal, kinematic and kinetic improvements after Lokomat(®) training, in hemiparetic subjects, rarely investigated before.

Effect of an overground training session versus a treadmill training session on timed up and go in hemiparetic patients.

BACKGROUND: Timed Up and Go (TUG) performance is reduced following stroke. Gait training improves gait-related activities in hemiparetic patients. However, no study has compared the impact of a single overground training session with a treadmill training session on gait-related activities (assessed by TUG). OBJECTIVE: To compare the immediate effect of a single overground training session versus a single treadmill training session on TUG performance in hemiparetic patients. METHODS: In this randomized controlled clinical trial, 56 hemiparetic patients were randomized to 1 or 2 distinct groups: a single gait training session overground (O group) or on a treadmill (T group). Time taken to perform the TUG (in seconds) was assessed before and immediately after the completion of each session. RESULTS: Time taken to perform the TUG decreased significantly, and to a similar extent, in both groups following the training session (O group, 5.9%; T group, 5.2%). CONCLUSIONS: An overground training session and a treadmill training session were equally effective in improving TUG performance in hemiparetic patients. Hemiparetic patients should be encouraged to walk regularly overground including turns for 20 minutes without stopping. This is an easy and inexpensive self-rehabilitation method to improve functional gait-related activities involved in the TUG test.

Assessing muscle quality as a key predictor to differentiate fallers from non-fallers in older adults.

BACKGROUND: Falling is an important public health issue because of its prevalence and severe consequences. Evaluating muscle performance is important when assessing fall risk. The study aimed to identify factors [namely muscle capacity (strength, quality, and power) and spatio-temporal gait attributes] that best discriminate between fallers and non-fallers in older adults. The hypothesis is that muscle quality, defined as the ratio of muscle strength to muscle mass, is the best predictor of fall risk. METHODS: 184 patients were included, 81% (n = 150) were women and the mean age was 73.6 ± 6.83 years. We compared body composition, mean grip strength, spatio-temporal parameters, and muscle capacity of fallers and non-fallers. Muscle quality was calculated as the ratio of maximum strength to fat-free mass. Mean handgrip and power were also controlled by fat-free mass. We performed univariate analysis, logistic regression, and ROC curves. RESULTS: The falling patients had lower muscle quality, muscle mass-controlled power, and mean weighted handgrip than the non-faller. Results showing that lower muscle quality increases fall risk (effect size = 0.891). Logistic regression confirmed muscle quality as a significant predictor (p < .001, OR = 0.82, CI [0.74; 0.89]). ROC curves demonstrated muscle quality as the most predictive factor of falling (AUC = 0.794). CONCLUSION: This retrospective study showed that muscle quality is the best predictor of fall risk, above spatial and temporal gait parameters. Our results underscore muscle quality as a clinically meaningful assessment and may be a useful complement to other assessments for fall prevention in the aging population.

Age-related effects on absolute and relative isokinetic knee extensor strength in community-dwelling older men and women at a French geriatric day hospital.

PURPOSE: Isokinetic knee extensor strength is poorly evaluated in geriatric day hospitals (GDHs), despite its potential functional significance compared to grip strength. This study aimed to investigate age-related effects on absolute and relative isokinetic knee extensor peak torque (KEPT) data in community-dwelling older GDH patients. METHODS: A total of 472 French GDH patients (179 men and 293 women, aged 75-94 years) participated in this study. Absolute and relative KEPT were measured at six distinct angular velocities between 0.52 and 3.14 rad/s. In addition, comfortable gait speed and grip strength were assessed. Participants were stratified by sex and age using 5-year intervals. One-way ANOVAs were used to examine age-related effects on KEPT values. Multiple linear regression models were employed to investigate the associations between gait speed and both mean KEPT values and grip strength, with separate models conducted on absolute and relative values. RESULTS: The recruited GDH patients presented lower absolute and relative KEPT values in comparison with established reference values for healthy community-dwelling older individuals, with men being consistently stronger than women. Notably, there was a significant decline in both absolute and relative KEPT values beyond the age of 85 for both sexes. Importantly, the multiple linear regression analyses conducted revealed a significant positive relationship between gait speed and mean KEPT values, surpassing the association with grip strength. CONCLUSIONS: These findings underscore the clinical importance of assessing isokinetic knee extensor strength in community-dwelling older GDH patients, particularly for tailoring personalized physical activity interventions.

Does a single gait training session performed either overground or on a treadmill induce specific short-term effects on gait parameters in patients with hemiparesis? A randomized controlled study.

BACKGROUND: Gait training for patients with hemiparesis is carried out independently overground or on a treadmill. Several studies have shown differences in hemiparetic gait parameters during overground versus treadmill walking. However, few studies have compared the effects of these 2 gait training conditions on gait parameters, and no study has compared the short-term effects of these techniques on all biomechanical gait parameters. OBJECTIVE: To determine whether a gait training session performed overground or on a treadmill induces specific short-term effects on biomechanical gait parameters in patients with hemiparesis. METHODS: Twenty-six subjects with hemiparesis were randomly assigned to a single session of either overground or treadmill gait training. The short-term effects on spatiotemporal, kinematic, and kinetic gait parameters were assessed using gait analysis before and immediately after the training and after a 20-minute rest. RESULTS: Speed, cadence, percentage of single support phase, peak knee extension, peak propulsion, and braking on the paretic side were significantly increased after the gait training session. However, there were no specific changes dependent on the type of gait training performed (overground or on a treadmill). CONCLUSION: A gait training session performed by subjects with hemiparesis overground or on a treadmill did not induce specific short-term effects on biomechanical gait parameters. The increase in gait velocity that followed a gait training session seemed to reflect specific modifications of the paretic lower limb and adaptation of the nonparetic lower limb.

Occurrence of fatigue induced by a whole-body vibration session is not frequency dependent.

The aim of this study was to determine whether neuromuscular adaptations (magnitude and location) induced by isometric exercise performed on an oscillating platform are dependent on whole-body vibration (WBV) frequency. Eleven young men performed 4 separate fatigue sessions of static squatting exercise at 3 frequencies of WBV (V20, V40, and V60) and 1 session without vibration (V0). Isometric torque and electromyographic activity of the vastus lateralis, rectus femoris, and biceps femoris were recorded during maximal voluntary and evoked contractions of the knee extensor muscles before and after each fatigue session to examine both peripheral and central adaptations. Isometric torque decreased significantly after each of the 4 frequency sessions (V0: -9.4 ± 6.1%, p = 0.003; V20: -8.1 ± 9.9%, p = 0.010; V40: -11.9 ± 12.7%, p = 0.011; and V60: -7.8 ± 9.2%, p = 0.001, respectively), but this reduction was not significantly different between frequencies. The torque produced by evoked contraction significantly decreased from pre-exercise values after each session (V0: -14.9 ± 15.6%, p = 0.012; V20: -15.8 ± 16.4%, p = 0.010; V40: -21.0 ± 14.3%, p = 0.004; and V60: -17.3 ± 11.6%, p = 0.005, respectively); however, there was no effect of vibration frequency. In both conditions, the maximal voluntary contraction torque reduction observed was mainly attributable to peripheral fatigue and was not because of central modifications of the neuromuscular system. The present study demonstrates that the frequency of vibration does not significantly influence the magnitude and location of neuromuscular fatigue, suggesting that adding WBV to static squat exercise (on a vertically oscillating platform) does not provide an additional training stimulus.

Effects of age, sex, frailty and falls on cognitive and motor performance during dual-task walking in older adults.

BACKGROUND: Dual-task (DT) walking is of great interest in clinical evaluation to evaluate the risk of falling or cognitive declines in older adults. However, it appears necessary to investigate deeply the confounding factors to better understand their impact on dual-task performance. OBJECTIVE: To evaluate the effect of age, sex, falls and frailty on cognitive and motor parameters in dual-task walking. SUBJECTS: 66 older participants (mean age = 75.5 ± 6.3; mean height = 165.8 ± 8.4 cm; mean weight = 68.4 ± 14 kgs) were split into groups based on their age, sex, fall and frailty status. METHODS: Participants performed single-task walking, single-task cognitive (serial subtraction of 3), and dual-task walking (subtraction + walking) for 1 min at their fast pace. Gait speed, step length, step length variability, stance and swing phase time, single and double support, cadence, step time variability and gait speed variability were recorded in single- and dual-task walking and used to calculate the dual-task effect (DTE) as ((DT - ST) / ST) ∗ 100). The cognitive score (DTEcog) was calculated as the number of correct responses minus errors. Generalized linear mixed models (GLMM) were used to compare the effects of falls, frailty, age and sex on gait and cognitive variables. RESULTS: The interaction frailty*sex and frailty*age were the major effect on the DTEs. Specifically, the DTE was higher in women than men and in the frail group compared to non-frail. CONCLUSIONS: The present findings provide a better understanding on the confounding factors explaining the behavior in DT that could be used to develop more effective dual-task clinical programs for community-living older adults.

Effects of individualized lower limb isokinetic strengthening in clinical rehabilitation of older post-stroke patients: A retrospective study.

OBJECTIVE: Muscle weakness in the lower limbs is a motor consequence of stroke that causes functional impairment. The aim of this study was to assess the effectiveness of an individualized isokinetic strengthening programme, using the moment-velocity profile, on functional recovery during post-stroke rehabilitation of older patients. A further objective was to describe the effects of the individualized isokinetic strengthening on muscular parameters. DESIGN: Retrospective study. PATIENTS: Older post-stroke patients. METHODS: Using the Barthel Index, functional abilities in basic daily tasks were assessed and retrospectively analysed for 88 patients in a post-stroke rehabilitation unit. Of these, 44 patients received conventional rehabilitation (conventional group) and 44 received individualized isokinetic strengthening in addition to conventional rehabilitation (isokinetic group). A 2-Group (isokinetic, conventional) × 2-Time (before, after intervention) repeated measures analysis of variance (ANOVA) was conducted. For muscular parameters, Student t-tests and Wilcoxon tests were performed. RESULTS: The Barthel Index score increased more in the isokinetic group (61.59 ± 26.34 to 88.18 ± 12.16) than in the conventional group (61.70 ± 26.5 to 76.93 ± 18.12). A significant Time × Group interaction was found (F(1,86) = 5.95, p = 0.02). In the isokinetic group all muscular parameters improved. CONCLUSION: This retrospective clinical study suggests that lower limb isokinetic strengthening, individualized using the moment-velocity profile, is clinically efficient for functional recovery during post-stroke rehabilitation of older patients. Intragroup effects of isokinetic strengthening also suggest benefits for muscular parameters.

Effect of a sex stereotype on cortical activity during a self-paced exercise: A motor-related cortical potential approach.

Recent research has shown that inducing a negative stereotype toward women does not always decrease the subsequent motor performance of women, but can increase it, especially during endurance tasks. The mechanisms involved are nonetheless still poorly understood. The main aim of the present study was to investigate the effect of a negative stereotype toward women on men's and women's performance during an endurance task, and to analyze the neuropsychological mechanisms involved through motor-related cortical potentials and motivation toward men/women. Thirty-four participants were assigned to a negative stereotype toward women condition and a nullified-stereotype condition and performed 80 self-paced intermittent isometric elbow contractions at a moderate perceived intensity. Results showed that women performed better when assigned to the negative stereotype toward women condition, they were more motivated to outperform men, and their MRCP amplitudes were higher in this same condition over the prefrontal cortex (i.e., FP1 and FP2). Concerning men, they also performed better when the negative stereotype toward women was induced. However, no effect emerged on motivation toward women and MRCP amplitudes. This study showed that inducing a negative stereotype during an endurance task led to a performance increase in women, which is contrary to the stereotype threat theory, strengthening the idea of a task-dependency effect when inducing a negative stereotype. This performance improvement observed in women may be caused by increased motivation to outperform men and a planning of the upcoming movement. Concerning men, more research is needed to clarify the mechanisms involved in such performance improvement.

How does apathy impact exploration-exploitation decision-making in older patients with neurocognitive disorders?

Apathy is a pervasive clinical syndrome in neurocognitive disorders, characterized by a quantitative reduction in goal-directed behaviors. The brain structures involved in the physiopathology of apathy have also been connected to the brain structures involved in probabilistic reward learning in the exploration-exploitation dilemma. This dilemma in question involves the challenge of selecting between a familiar option with a more predictable outcome, and another option whose outcome is uncertain and may yield potentially greater rewards compared to the known option. The aim of this study was to combine experimental procedures and computational modeling to examine whether, in older adults with mild neurocognitive disorders, apathy affects performance in the exploration-exploitation dilemma. Through using a four-armed bandit reinforcement-learning task, we showed that apathetic older adults explored more and performed worse than non-apathetic subjects. Moreover, the mental flexibility assessed by the Trail-making test-B was negatively associated with the percentage of exploration. These results suggest that apathy is characterized by an increased explorative behavior and inefficient decision-making, possibly due to weak mental flexibility to switch toward the exploitation of the more rewarding options. Apathetic participants also took longer to make a choice and failed more often to respond in the allotted time, which could reflect the difficulties in action initiation and selection. In conclusion, the present results suggest that apathy in participants with neurocognitive disorders is associated with specific disturbances in the exploration-exploitation trade-off and sheds light on the disturbances in reward processing in patients with apathy.

Does the Effect of Stereotypes in Older People Depend Upon Task Intensity?

This study examined the effect of negative and positive stereotypes on the strength produced by older adults at different perceived effort intensities, reflecting different levels of task difficulty. Fifty older women were randomly assigned to a positive stereotype, a negative stereotype, or a control condition. Before (T1) and after (T2) the stereotype manipulation, they were asked to perform a voluntary isometric contraction at a level of muscular effort that corresponded to four perceived effort intensities ("easy," "moderate," hard" and "very hard"). Results showed that participants attained greater strength during the easy and hard tasks after exposure to both positive and negative stereotypes. At the moderate and very hard intensities, stereotype induction did not significantly change the strength from the baseline performance. While these results are not fully in line with the stereotype threat theory, they provide evidence that task difficulty could modulate the effect of aging stereotypes during physical tasks.

A kinematic-geometric model based on ankles' depth trajectory in frontal plane for gait analysis using a single RGB-D camera.

The emergence of RGB-D cameras and the development of pose estimation algorithms offer opportunities in biomechanics. However, some challenges still remain when using them for gait analysis, including noise which leads to misidentification of gait events and inaccuracy. Therefore, we present a novel kinematic-geometric model for spatio-temporal gait analysis, based on ankles' trajectory in the frontal plane and distance-to-camera data (depth). Our approach consists of three main steps: identification of the gait pattern and modeling via parameterized curves, development of a fitting algorithm, and computation of locomotive indices. The proposed fitting algorithm applies on both ankles' depth data simultaneously, by minimizing through numerical optimization some geometric and biomechanical error functions. For validation, 15 subjects were asked to walk inside the walkway of the OptoGait, while the OptoGait and an RGB-D camera (Microsoft Azure Kinect) were both recording. Then, the spatio-temporal parameters of both feet were computed using the OptoGait and the proposed model. Validation results show that the proposed model yields good to excellent absolute statistical agreement (0.86 ≤ Rc ≤ 0.99). Our kinematic-geometric model offers several benefits: (1) It relies only on the ankles' depth trajectory both for gait events extraction and spatio-temporal parameters' calculation; (2) it is usable with any kind of RGB-D camera or even with 3D marker-based motion analysis systems in absence of toes' and heels' markers; and (3) it enables improving the results by denoising and smoothing the ankles' depth trajectory. Hence, the proposed kinematic-geometric model facilitates the development of portable markerless systems for accurate gait analysis.