Measuring fingerpad deformation during active object manipulation.

During active object manipulation, the finger-object interactions give rise to complex fingertip skin deformations. These deformations are in turn encoded by the local tactile afferents and provide rich and behaviorally relevant information to the central nervous system. Most of the work studying the mechanical response of the finger to dynamic loading has been performed under a passive setup, thereby precisely controlling the kinematics or the dynamics of the loading. However, to identify aspects of the deformations that are relevant to online control during object manipulation, it is desirable to measure the skin response in an active setup. To that end, we developed a device that allows us to monitor finger forces, skin deformations, and kinematics during fine manipulation. We describe the device in detail and test it to precisely describe how the fingertip skin in contact with the object deforms during a simple vertical oscillation task. We show that the level of grip force directly influences the fingerpad skin strains and that the strain rates are substantial during active manipulation (norm up to 100%/s). The developed setup will enable us to causally relate sensory information, i.e. skin deformation, to online control, i.e. grip force adjustment, in future studies.NEW & NOTEWORTHY We present a novel device, a manipulandum, that enables to image the contact between the finger and the contact surface during active manipulation of the device. The device is tested in a simple vertical oscillation task involving 18 participants. We demonstrate that substantial surface skin strains take place at the finger-object interface and argue that those deformations provide essential information for grasp stability during object manipulation.

Recognizing Manual Activities Using Wearable Inertial Measurement Units: Clinical Application for Outcome Measurement.

The ability to monitor activities of daily living in the natural environments of patients could become a valuable tool for various clinical applications. In this paper, we show that a simple algorithm is capable of classifying manual activities of daily living (ADL) into categories using data from wrist- and finger-worn sensors. Six participants without pathology of the upper limb performed 14 ADL. Gyroscope signals were used to analyze the angular velocity pattern for each activity. The elaboration of the algorithm was based on the examination of the activity at the different levels (hand, fingers and wrist) and the relationship between them for the duration of the activity. A leave-one-out cross-validation was used to validate our algorithm. The algorithm allowed the classification of manual activities into five different categories through three consecutive steps, based on hands ratio (i.e., activity of one or both hands) and fingers-to-wrist ratio (i.e., finger movement independently of the wrist). On average, the algorithm made the correct classification in 87.4% of cases. The proposed algorithm has a high overall accuracy, yet its computational complexity is very low as it involves only averages and ratios.

Determinants of Social Participation at 1, 3, and 6 Months Poststroke in Benin.

OBJECTIVE: To build a model of prediction of social participation of community-dwelling stroke survivors in Benin at 1 month, 3 months, and 6 months. DESIGN: An observational study with evaluations at 1 month, 3 months, and 6 months poststroke. Correlational analyses and multivariate linear regressions were performed. SETTING: Outpatient rehabilitation centers in Benin. PARTICIPANTS: A volunteer sample of 91 stroke patients was enrolled at baseline; 64 (70%) patients completed all the study (N=64): 70% male and 52% right hemiparesis. INTERVENTION: Not applicable. MAIN OUTCOME MEASURES: Participants were evaluated with the Participation Measurement Scale, ACTIVLIM-Stroke (activities of daily living [ADL]), Stroke Impairment Assessment Set, 6-minute walk test, Hospital Anxiety and Depression Scale, and the modified Rankin Scale. RESULTS: The significant predictors of social participation after controlling the confounders were the following: at 1 month ADL (0.4 [0.3, 0.6]) and depression (‒0.6 [‒0.8, ‒0.2]) with total model R2=0.44; at 3 months ADL (0.58 [0.4, 0.7]) and depression (‒0.58 [‒0.5, ‒0.7]) with total model R2=0.65; and at 6 months ADL (0.31 [0.2, 0.5]), impairments (‒0.82 [‒0.5, ‒0.7]), and depression (‒0.94 [‒0.8, ‒0.2]) with total model R2=0.78. CONCLUSIONS: Using socioculturally tailored tools, the present study identified ADL performance (ACTIVLIM-Stroke), depression (Hospital Anxiety Depression Scale), and overall impairments (Stroke Impairment Assessment Set) as the significant determinants of social participation (Participation Measurement Scale) poststroke in Benin. These findings will be a valuable resource for rehabilitation stakeholders in evaluating interventions, programs, and policies designed to encourage social participation for stroke patients.

Optimal use of limb mechanics distributes control during bimanual tasks.

Bimanual tasks involve the coordination of both arms, which often offers redundancy in the ways a task can be completed. The distribution of control across limbs is often considered from the perspective of handedness. In this context, although there are differences across dominant and nondominant arms during reaching control ( Sainburg 2002 ), previous studies have shown that the brain tends to favor the dominant arm when performing bimanual tasks ( Salimpour and Shadmehr 2014 ). However, biomechanical factors known to influence planning and control in unimanual tasks may also generate limb asymmetries in force generation, but their influence on bimanual control has remained unexplored. We investigated this issue in a series of experiments in which participants were instructed to generate a 20-N force with both arms, with or without perturbation of the target force during the trial. We modeled the task in the framework of optimal feedback control of a two-link model with six human-like muscles groups. The biomechanical model predicted a differential contribution of each arm dependent on the orientation of the target force and joint configuration that was quantitatively matched by the participants' behavior, regardless of handedness. Responses to visual perturbations were strongly influenced by the perturbation direction, such that online corrections also reflected an optimal use of limb biomechanics. These results show that the nervous system takes biomechanical constraints into account when optimizing the distribution of forces generated across limbs during both movement planning and feedback control of a bimanual task. NEW & NOTEWORTHY Here, we studied a bimanual force production task to examine the effects of biomechanical constraints on the distribution of control across limbs. Our findings show that the central nervous system optimizes the distribution of force across the two arms according to the joint configuration of the upper limbs. We further show that the underlying mechanisms influence both movement planning and online corrective responses to sudden changes in the target force.

Responsiveness of the ACTIVLIM-CP questionnaire: measuring global activity performance in children with cerebral palsy.

AIM: To investigate the responsiveness of the ACTIVLIM-CP questionnaire after two evidence-based interventions for children with cerebral palsy (CP). METHOD: Seventy-five children with CP either participated in an intensive motor-skill learning intervention (hand-arm bimanual intensive therapy including lower extremities [HABIT-ILE], n=47) or received botulinum neurotoxin-A (BoNT-A) injection(s) into lower extremities combined with conventional physical therapy (n=28). All children were assessed three times: at baseline (T0 ; before HABIT-ILE/the day of BoNT-A injection), at T1 (last day of HABIT-ILE/6wks after BoNT-A injection), and at follow-up (T2 ; 3-4mo after the beginning of intervention). Parents completed ACTIVLIM-CP and three other activity questionnaires. Responsiveness was analysed using group (based on intervention), subgroup (based on gross motor function level), and individual approaches. RESULTS: For the HABIT-ILE group, significant improvements in ACTIVLIM-CP were observed for the T0 -T1 period (p<0.001) but not for the T1 -T2 period. No significant changes were found in the BoNT-A group during assessments (p=0.84). In the subgroup analysis for the HABIT-ILE group (T0 -T1 ), greater changes were demonstrated for children in Gross Motor Function Classification System levels III and IV (p<0.001, effect size=1.36). The individual approach was congruent with the group approach. INTERPRETATION: ACTIVLIM-CP demonstrated high responsiveness after HABIT-ILE, showing that this scale may be used to investigate global activity performance in clinical trials focusing on improving daily life activities. WHAT THIS PAPER ADDS: Good responsiveness of ACTIVLIM-CP questionnaire during intensive motor-skill learning intervention. Higher responsiveness for children in Gross Motor Function Classification System (GMFCS) levels III and IV versus I and II after intensive intervention. ACTIVLIM-CP is useful to identify children improving their performance after botulinum neurotoxin-A injection.

Tracking Changes in Participation With Participation Measurement Scale in Community-Dwelling Stroke Survivors in Africa.

OBJECTIVE: To investigate responsiveness of the Participation Measurement Scale (PM-Scale) for the measurement of participation of stroke survivors. DESIGN: A 6-month observational study with 3 evaluation time points. Responsiveness of the PM-Scale was investigated over a period of 6 months. SETTING: Rehabilitation centers. PARTICIPANTS: Stroke survivors (N =64); mean age ± SD, 56.9±12.6 years; sex, 45 men (70%). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Participants were evaluated using the PM-Scale. The modified Rankin Scale was used to categorize the overall disability level for each participant. RESULTS: The mixed-effect model analysis showed a significant difference in the participation over time (χ2=35.04; df=2; P<.001). In addition, the model exhibited significant effects of the sex, age, and disability at enrollment on the subjects' participation levels. Furthermore, the PM-Scale detected different levels of changes in the entire cohort over time (small change, effect size [ES]=0.33; moderate change, ES=0.67; and large change, ES=1). The PM-Scale also facilitated the classification of the participants into discriminative categories such as important improvement (t score≥1.96; 1.8≤ES≤2.13), moderate improvement (0

Measuring Participation After Stroke in Africa: Development of the Participation Measurement Scale.

OBJECTIVE: To develop a valid stroke-specific tool, named the Participation Measurement Scale (PM-Scale), for the measurement of participation after stroke. DESIGN: Observational study and questionnaire development. SETTING: Outpatient rehabilitation centers. PARTICIPANTS: Patients with stroke (N=276; mean age, 58.5±11.1y; 57% men). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Participants completed a 100-item experimental questionnaire of the PM-Scale. Items were scored as "not at all," "weakly," or "strongly." The Hospital Anxiety and Depression Scale was used to evaluate depression, and the modified Rankin Scale was used to categorize the severity of disability on the basis of observation. RESULTS: After successive Rasch analyses using unrestricted partial credit parameterization, a valid, unidimensional, and linear 22-item scale for the measurement of participation was constructed. All 22 items fulfilled the measurement requirements of overall and individual item and person fits, category discrimination, invariance, and local response independence. The PM-Scale showed good internal consistency (person separation index, .93). The test-retest reliability of item difficulty hierarchy (r=.96; P<.001) and patient location (r=.99; P<.001) were excellent. This patient-based scale covers all 9 International Classification of Functioning, Disability and Health domains of participation. CONCLUSIONS: The PM-Scale has good psychometric qualities and provides accurate measures of participation in patients with stroke in Africa.

Measuring changes of manual ability with ABILHAND-Kids following intensive training for children with unilateral cerebral palsy.

AIM: ABILHAND-Kids is a parent-reported questionnaire measuring manual ability in children with cerebral palsy (CP). Its psychometric properties have been established, with the exception of responsiveness, which is examined here. METHOD: In this cohort study, 98 children (46 males, 52 females; range 6-19y, mean 11y, standard deviation [SD] 3.3y) with unilateral CP underwent three assessments of upper extremity function: at baseline (T1); after 80 to 90 hours of intensive training (T2); and at follow-up (T3). The responsiveness was analyzed using global, group (based on age and on Manual Ability Classification System [MACS] level), and individual approaches during two time periods (T1-T2 and T2-T3). Effect size was used to quantify magnitude of changes. RESULTS: The global approach showed significant improvements between T1 and T2 (p<0.001) but not between T2 and T3 (p=0.222). In the group analyses, effect size and SRM demonstrated large changes in younger children (6-12y, n=52, mean change=1.06 logit, effect size >0.8) and small changes in the older children (13-19y, n=46, mean change=0.71 logit, effect size >0.4). Children in MACS level II demonstrated larger changes than children in MACS level I or III. INTERPRETATION: The ABILHAND-Kids exhibited responsiveness in detecting changes after intensive training. Therefore, this scale is potentially useful in assessing the functional status of children with unilateral CP in clinical trials.

Biological inflammatory markers mediate the effect of preoperative pain-related behaviours on postoperative analgesics requirements.

BACKGROUND: The predictive value of an individual's attitude towards painful situations and the status of his immune system for postoperative analgesic requirements are not well understood. These may help the clinician to anticipate individual patient's needs. METHODS: Sixty patients, who underwent a laparoscopic cholecystectomy under standardised general anaesthesia, were included. The total analgesic requirements during the first 48 h were the primary endpoint (unitary dosage, UD). The individual's attitude towards imaginary painful situations was measured with the Situational Pain Scale (SPS). The emotional status was assessed by the Hospital Anxiety and Depression Scale (HADS) and the inflammatory status by the neutrophil-to-lymphocyte ratio (NLR). RESULTS: Univariate analyses revealed a significant association between UD and SPS, HADS and NLR. A negative relationship between SPS and NLR (NLR = 0.820-0.180*SPS;R(2) = 0.211;P < 0.001) and a positive relationship between SPS and HADS (HADS = 14.8 + 1.63*SPS; R(2) = 0.159;P = 0.002) were observed. A multiple linear regression analysis showed that the contribution of NLR to the UD was the most effective. A mediation analysis showed a complete mediation of the effect of SPS on UD (R(2) = 0.103;P = 0.012), by the NLR (SPS on NLR: R(2) = 0.211;P = <0.001), the HADS (SPS on HADS: R(2) = 0.159;P = 0.002). The variance in UD explained by the SPS was indirect and amounts to 46% through NLR and to 34% through HADS. CONCLUSIONS: In this series, preoperative pain-related attitudes (SPS) were associated with the postoperative analgesic requirements (UD) after a cholecystectomy. Eighty per cent of this effect was mediated by the HADS and the NLR.

Measuring functional recovery in stroke patients: the responsiveness of ACTIVLIM-stroke.

BACKGROUND AND PURPOSE: To determine the efficacy of the ACTIVLIM-Stroke questionnaire in detecting changes in functional status of stroke patients. METHOD: Sixty-eight Benin and Belgian stroke patients participated in this 2-month longitudinal study, involving baseline and follow-up assessments. Outcome measures combined ACTIVLIM-Stroke questionnaire, Barthel Index (BI), 6-minute-walk test (6MWT) and modified Rankin scale (MRS). Responsiveness of ACTIVLIM-Stroke was investigated through different methodological approaches and compared with BI, 6MWT and MRS. Statistical analyses were performed using the paired t tests, effect size (ES) and correlation tests. RESULTS: ACTIVLIM-Stroke detected changes in the whole sample (p<0.001, ES=0.78) and even in a subgroup of patients (p<0.001, ES=0.29) that were classified as stable according to the MRS. Moreover, ACTIVLIM-Stroke permitted the classification of patients into more discriminative groups, including those showing an important improvement (p<0.001, ES=1.87), a slight but non-clinically meaningful improvement (p<0.001, ES=0.38), and no improvement (p=0.1, ES=0.11), demonstrating its high sensitivity to change. Furthermore, there were concordant relationships between ACTIVLIM-Stroke change and any observed changes in BI, 6MWT and MRS scores (r≥0.50, p<0.001), confirming the external responsiveness of ACTVLIM-Stroke. CONCLUSIONS: ACTIVLIM-Stroke showed good responsiveness and can detect accurately clinical changes in the functional status of stroke patients. The BI and the 6MWT were also responsive and may provide complementary information while investigating change in functional status. However, in addition to being highly sensitive to change, ACTIVLIM-Stroke presents significant methodological advantages for quantifying functional changes in stroke patients.

Assessing locomotion ability in West African stroke patients: validation of ABILOCO-Benin scale.

OBJECTIVE: To calibrate and validate the Benin version of ABILOCO, a Rasch-built scale developed to assess locomotion ability in stroke patients. DESIGN: Prospective study and questionnaire development. SETTING: Rehabilitation centers. PARTICIPANTS: Stroke patients (N=230; mean age ± SD, 51.1±11.6 y; 64.3% men). INTERVENTION: Not applicable. MAIN OUTCOME MEASURES: Participants completed a preliminary list of 36 items including the 13 items of ABILOCO. Items were scored as "impossible," "difficult," or "easy." The mobility subdomain of FIM (FIM-mobility), the Functional Ambulation Classification (FAC), the 6-minute walk test (6MWT), and the 10-meter walk test (10MWT) were used to evaluate and elucidate the validity of the ABILOCO-Benin scale. RESULTS: Successive Rasch analyses led to the selection of 15 items that define a unidimensional, invariant, and linear measure of locomotion ability in stroke patients. This modified version of the ABILOCO scale, named ABILOCO-Benin, showed an excellent internal consistency, with a Person Separation Index of .93, and excellent test-retest reliability with high intraclass correlation coefficients of .95 (P<.001) for item difficulty and .93 (P<.001) for subject measures. It also presented good construct validity compared with FAC, FIM-mobility, 6MWT, and 10MWT (r≥.75, P<.001). CONCLUSIONS: ABILOCO-Benin presents good psychometric properties. It allows valid, reliable, and objective measurements of locomotion ability in stroke patients.

Fast grip force adaptation to friction relies on localized fingerpad strains.

During object manipulation, humans adjust the grip force to friction, such that slippery objects are squeezed more firmly than sticky ones. This essential mechanism to keep a stable grasp relies on feedback from tactile afferents innervating the fingertips, that are sensitive to local skin strains. To test if this feedback originates from the skin-object interface, we asked participants to perform a grip-lift task with an instrumented object able to monitor skin strains at the contact through transparent plates of different frictions. We observed that, following an unbeknown change in plate across trials, participants adapted their grip force to friction. After switching from high to low friction, we found a significant increase in strain inside the contact arising ~100 ms before the modulation of grip force, suggesting that differences in strain patterns before lift-off are used by the nervous system to quickly adjust the force to the frictional properties of manipulated objects.

A haptic illusion created by gravity.

Human dexterity requires very fine and efficient control of fingertip forces, which relies on the integration of cutaneous and proprioceptive feedback. Here, we examined the influence of gravity on isometric force control. We trained participants to reproduce isometric vertical forces on a dynamometer held between the thumb and the index finger in normal gravity and tested them during parabolic flight creating phases of microgravity and hypergravity, thereby strongly influencing the motor commands and the proprioceptive feedback. We found that gravity creates the illusion that upward forces are larger than downward forces of the same magnitude. The illusion increased under hypergravity and was abolished under microgravity. Gravity also affected the control of the grip force employed to secure the grasp. These findings suggest that gravity biases the haptic estimation of forces, which has implications for the design of haptic devices to be used during flight or space activities.

Effect of mixed and collective physical activity in chronic stroke rehabilitation: A randomized cross-over trial in low-income settings.

BACKGROUND: The prevalence of physical inactivity after stroke is high and exercise training improves many outcomes. However, access to community training protocols is limited, especially in low-income settings. OBJECTIVE: To investigate the feasibility and efficacy of a new intervention: Circuit walking, balance, cycling and strength training (CBCS) on activity of daily living (ADL) limitations, motor performance, and social participation restrictions in people after stroke. METHODS: Forty-six community-dwelling individuals with chronic stroke who were no longer in conventional rehabilitation were randomized into an immediate CBCS group (IG; initially received CBCS training for 12 weeks in phase 1), and a delayed CBCS group (DG) that first participated in sociocultural activities for 12 weeks. In phase 2, participants crossed over so that the DG underwent CBCS and the IG performed sociocultural activities. The primary outcome was ADL limitations measured with the ACTIVLIM-Stroke scale. Secondary outcomes included motor performance (balance: Berg Balance Scale [BBS], global impairment: Stroke Impairment Assessment Set [SIAS] and mobility: 6-minute and 10-metre walk tests [6MWT and 10mWT] and psychosocial health [depression and participation]). Additional outcomes included feasibility (retention, adherence) and safety. RESULTS: ADL capacity significantly improved pre to post CBCS training (ACTIVLIM-stroke, +3,4 logits, p < 0.001; effect size [ES] 0.87), balance (BBS, +21 points, p < 0.001; ES 0.9), impairments (SIAS, +11 points, p < 0.001; ES 0.9), and mobility (+145 m for 6MWT and +0.37 m/s for 10mWT; p < 0.001; ES 0.7 and 0.5 respectively). Similar improvements in psychosocial health occurred in both groups. Adherence and retention rates were 95% and 100%, respectively. CONCLUSION: CBCS was feasible, safe and improved functional independence and motor abilities in individuals in the chronic stage of stroke. Participation in CBCS improved depression and social participation similarly to participation in sociocultural activities. The benefits persisted for at least 3 months after intervention completion. PROTOCOL REGISTRATION NUMBER: PACTR202001714888482.

Translation and cross-cultural adaptation of the Brazilian version of the PM-Scale: A specific measure of participation after stroke.

BACKGROUND: The PM-Scale was developed specifically to assess participation in individuals after stroke based on the concepts contained in the International Classification of Functioning, Disability and Health. However, this measure is only available in English and French. OBJECTIVE: To translate and cross-culturally adapt the PM-Scale to Brazilian Portuguese, followed by the validation and testing of reliability of the translated version. METHODS: The translation process followed standard guidelines. Preliminary test-retest reliability was determined using the intraclass correlation coefficient (ICC2,1). The Rasch model was employed to analyse the validity, unidimensionality, invariance, and internal consistency of the Brazilian version of the PM-Scale. RESULTS: The final translated version of the PM-Scale presented appropriate semantic, idiomatic, cultural, and conceptual equivalence. The preliminary analysis revealed excellent intra-observer and inter-observer reliability (ICC2,1 = 0.91; 95%CI: 0.83, 0.95 and ICC2,1 = 0.81; 95%CI: 0.64, 0.89, respectively). The analysis of the Rasch model revealed only one erratic item. An excellent overall fit was found for items (mean ± SD = 0.01 ± 1.02) and adequate fit was found for persons (mean ± SD = 1.16 ± 0.88). Internal consistency was considered adequate (person separation index = 1.77, reliability = 0.76). No significant invariance was found with regards to the personal characteristics of the sample (p > 0.05). CONCLUSION: The Brazilian version of the PM-Scale is a valid, unidimensional, linear, reliable scale for measuring participation in stroke survivors and can be administered in less than five minutes.

ACTIVLIM-Stroke: a crosscultural Rasch-built scale of activity limitations in patients with stroke.

BACKGROUND AND PURPOSE: This study describes the development of a Rasch-built scale measuring activity limitations in stroke patients, named ACTIVLIM-Stroke. METHOD: This new Rasch-built measure was constructed based on stroke patients' perceptions of difficulty in performing daily activities. Patients were recruited from inpatient and outpatient rehabilitation departments in Belgium and Benin. A 73-item questionnaire was completed by 204 participants. A random subsample of 83 subjects was given the questionnaire a second time. Data were analyzed using RUMM2030 software. RESULTS: After successive Rasch analyses, the ACTIVLIM-Stroke questionnaire, a unidimensional and linear 20-item measure of activity limitations, was constructed. All 20 items fulfilled Rasch requirements (overall and individual item fit, category discrimination, invariance, local response independence, and nonredundancy in item difficulty). This simple patient-based scale encompasses a large range of activities related to self-care, transfer, mobility, manual ability, and balance. The ACTIVLIM-Stroke questionnaire exhibited high internal validity, excellent internal consistency, and good crosscultural validity. The test-retest reliability of item difficulty hierarchy (intraclass correlation coefficient=0.99) and patient location (intraclass correlation coefficient=0.92) were both excellent. Furthermore, it showed good external construct validity using correlations with the Functional Independence Measure motor and the Barthel Index and a higher discriminating capacity than either of these widely used indices. CONCLUSIONS: The ACTIVLIM-Stroke questionnaire has good psychometric qualities and provides accurate measures of activity limitations in patients with stroke. It is recommended for evaluating clinical and research interventions in patients with stroke, because it provides a higher discrimination and might be more sensitive to change.

PWC 75%/kg, a fitness index not linked to resting heart rate: testing procedure and reference values.

OBJECTIVES: To develop a fitness index unlinked to resting heart rate and suitable for clinical use, and to obtain reference values of this new index for healthy subjects. DESIGN: Cross-sectional study. SETTING: Research laboratory. PARTICIPANTS: A volunteer sample of healthy subjects (N=100; 50 men; age range, 20-70y) randomly recruited from the general community. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Participants performed a submaximal, multistage cycle ergometer test. A new fitness index, the physical working capacity at 75% of the predicted maximal heart rate per kilogram of body weight (PWC(75%)/kg), was calculated. Its concordance with a previously described fitness index and its relationship with age were examined, as well as differences attributable to sex and lifestyle. Reference values of the PWC(75%)/kg (mean ± SD and 95% confidence interval) were calculated and categorized by age classes of 10 years and by sex. RESULTS: The intraclass correlation coefficient (ICC) between PWC(75%)/kg and the working capacity index at 65% of the heart rate reserve per kilogram of body weight (WCI(65%HRreserve)/kg) was very high (ICC=.96, P<.001), indicating that the fitness index can be estimated without measuring the resting heart rate. PWC(75%)/kg decreased as age increased. The average PWC(75%)/kg was significantly higher in men than in women (P<.001), and in active than in inactive subjects (P<.01). CONCLUSIONS: This study presents a new fitness index, the PWC(75%)/kg, which is suitable for measuring fitness in active and sedentary people aged 20 to 70 years. It may also be a suitable fitness index for selected chronically ill individuals. This study also provides reference values of the PWC(75%)/kg obtained from healthy men and women.

Effectiveness of walking training on balance, motor functions, activity, participation and quality of life in people with chronic stroke: a systematic review with meta-analysis and meta-regression of recent randomized controlled trials.

PURPOSE: To review and quantify the effects of walking training for the improvement of various aspects of physical function of people with chronic stroke. METHODS: We conducted a systematic search and meta-analysis of randomized controlled trials (RCTs) of chronic stroke rehabilitation interventions published from 2008 to 2020 in English or French. Of the 6476-screened articles collated from four databases, 15 RCTs were included and analyzed. We performed a meta-regression with the total training time as dependent variable in order to have a better understanding of how did the training dosage affect the effect sizes. RESULTS: Treadmill walking training was more effective on balance and motor functions (standardized mean difference (SMD)=0.70[0.02, 1.37], p = 0.04) and 0.56[0.15, 0.96], p = 0.007 respectively). Overground walking training improved significantly walking endurance (SMD = 0.38[0.16, 0.59], p < 0.001), walking speed (MD = 0.12[0.05, 0.18], p < 0.001), participation (SMD = 0.35[0.02, 0.68], p = 0.04) and quality of life (SMD = 0.46[0.12, 0.80], p = 0.008). Aquatic training improved balance (SMD = 2.41[1.20, 3.62], p < 0.001). The Meta-regression analysis did not show significant effect of total training time on the effect sizes. CONCLUSION: Treadmill and overground walking protocols consisting of ≥30 min sessions conducted at least 3 days per week for about 8 weeks are beneficial for improving motor impairments, activity limitations, participation, and quality of life in people with chronic stroke.Implications for rehabilitationTreadmill walking training is effective for improving balance and motor functions.Overground walking training improved significantly walking endurance, walking speed, participation and quality of life.Treadmill and overground walking protocols consisting of ≥30 min sessions conducted at least 3 days per week for about 8 weeks are beneficial for improving motor impairments, activity limitations, participation, and quality of life in patient with chronic stroke.

Normal and tangential forces combine to convey contact pressure during dynamic tactile stimulation.

Humans need to accurately process the contact forces that arise as they perform everyday haptic interactions such as sliding the fingers along a surface to feel for bumps, sticky regions, or other irregularities. Several different mechanisms are possible for how the forces on the skin could be represented and integrated in such interactions. In this study, we used a force-controlled robotic platform and simultaneous ultrasonic modulation of the finger-surface friction to independently manipulate the normal and tangential forces during passive haptic stimulation by a flat surface. To assess whether the contact pressure on their finger had briefly increased or decreased during individual trials in this broad stimulus set, participants did not rely solely on either the normal force or the tangential force. Instead, they integrated tactile cues induced by both components. Support-vector-machine analysis classified physical trial data with up to 75% accuracy and suggested a linear perceptual mechanism. In addition, the change in the amplitude of the force vector predicted participants' responses better than the change of the coefficient of dynamic friction, suggesting that intensive tactile cues are meaningful in this task. These results provide novel insights about how normal and tangential forces shape the perception of tactile contact.

Grip Force is Adjusted at a Level That Maintains an Upper Bound on Partial Slip Across Friction Conditions During Object Manipulation.

Dexterous manipulation of objects heavily relies on the feedback provided by the tactile afferents innervating the fingertips. Previous studies have suggested that humans might take advantage of partial slip, localized loss of grip between the skin and the object, to gauge the stability of a contact and react appropriately when it is compromised, that is, when slippage is about to happen. To test this hypothesis, we asked participants to perform point-to-point movements using a manipulandum. Through optical imaging, the device monitored partial slip at the contact interface, and at the same time, the forces exerted by the fingers. The level of friction of the contact material was changed every five trials. We found that the level of grip force was systematically adjusted to the level of friction, and thus partial slip was limited to an amount similar across friction conditions. We suggest that partial slip is a key signal for dexterous manipulation and that the grip force is regulated to continuously maintain an upper bound on partial slip across friction conditions.