Do older adults perceive postural constraints for reach estimation?

UNLABELLED: BACKGROUND/STUDY CONTEXT: Recent evidence indicates that older persons have difficulty mentally representing intended movements. Furthermore, in an estimation of reach paradigm using motor imagery, a form of mental representation, older persons significantly overestimated their ability compared with young adults. The authors tested the notion that older adults may also have difficulty perceiving the postural constraints associated with reach estimation. METHODS: The authors compared young (Mage = 22 years) and older (Mage = 67) adults on reach estimation while seated and in a more postural demanding standing and leaning forward position. The expectation was a significant postural effect with the standing condition, as evidenced by reduced overestimation. RESULTS: Whereas there was no difference between groups in the seated condition (both overestimated), older adults underestimated whereas the younger group once again overestimated in the standing condition. CONCLUSION: From one perspective, these results show that older adults do perceive postural constraints in light of their own physical capabilities. That is, that group perceived greater postural demands with the standing posture and elected to program a more conservative strategy, resulting in underestimation.

Bilateral transfer for learning to control timing but not for learning to control fine force.

This study examined the characteristics of bilateral transfer of learning to control timing and fine force from a dominant limb to a nondominant limb. 20 right-handed college students (12 women, 8 men; M age = 21.5 yr., SD = 2.3) learned a sequential task consisting of timing and force control. Each participant completed a pre-test of the task with both hands and then performed 100 practice trials with the dominant hand. A post-test was conducted 1 hr. later. The results showed that after training, participants learned to control the timing and force. Nevertheless, only the time-control learning was transferred to the untrained hand, whereas the force-control learning did not transfer to the untrained hand.

Spontaneity competes with intention to influence the coordination dynamics of interpersonal performance tendencies.

Research has shown that spontaneous visual coupling supports frequency entrainment, phase attraction, and intermittent interpersonal coordination when co-actors are switched from a no-vision (NV) to vision (V) context. In two experiments, co-actors started in a NV context while producing the same or different amplitude movements. The same amplitude resulted in similar self-paced frequencies, while different amplitudes resulted in disparate frequencies. In experiment 1, co-actors were instructed to maintain amplitude while receiving no instructions to coordinate their actions. Frequency and phase entrainment was limited in the V context even when co-actors started the NV context with the same amplitude. In experiment 2, co-actors were instructed to maintain amplitude and intentionally coordinate together, but not at a specific pattern. Significant frequency modulations occurred to maintain amplitude as the co-actors sought to coordinate their actions. With the open-ended instructions, co-actors produced in-phase and anti-phase coordination along with intermittent performance exhibited by shifts between a variety of stable relative phase patterns. The proposed hypotheses and findings are discussed within the context of a shared manifold representation for joint action contexts, with the coordination dynamics expressed by the HKB model of relative phase serving to conceptualization the representations in the shared manifold.

Visual Cues for a Steadier You: Visual Feedback Methods Improved Standing Balance in Virtual Reality for People with Balance Impairments.

Users of head-mounted displays (HMDs) for virtual reality (VR) sometimes have balance issues since HMDs impede their view of the outside world. This has a greater impact on people with balance impairments since many rely more heavily on their visual cues to keep their balance. This is a significant obstacle to the universal usability and accessibility of VR. Although previous studies have verified the imbalance issue, not much work has been done to diminish it. In this study, we investigated how to increase VR balance by utilizing additional visual cues. To examine how different visual approaches (static, rhythmic, spatial, and center of pressure (CoP) based feedback) affect balance in VR, we recruited 100 people (50 with balance impairments due to multiple sclerosis and 50 without balance impairments) across two different geographic locations (United States and Bangladesh). All people completed both standing visual exploration as well as standing reach and grasp tasks. Results demonstrated that static, rhythmic, and CoP visual feedback approaches enhanced balance significantly ( ) in VR for people with balance impairments. The methods described in this study could be applied to design more accessible virtual environments for people with balance impairments.

Effect of visual field presentation on action planning (estimating reach) in children.

In this article, the authors examined the effects of target information presented in different visual fields (lower, upper, central) on estimates of reach via use of motor imagery in children (5-11 years old) and young adults. Results indicated an advantage for estimating reach movements for targets placed in lower visual field (LoVF), with all groups having greater difficulty in the upper visual field (UpVF) condition, especially 5- and 7-year-olds. Complementing these results was an overall age-related increase in accuracy. Based in part on the equivalence hypothesis suggesting that motor imagery and motor planning and execution are similar, the findings support previous work of executed behaviors showing that there is a LoVF bias for motor skill actions of the hand. Given that previous research hints that the UpVF may be bias for visuospatial (perceptual) qualities, research in that area and its association with visuomotor processing (LoVF) should be considered.

Visual landmarks and response delay in estimates of reach.

Visual background information may facilitate visually guided and memory guided estimates of reach, as estimates have been linked to the mental representation of action. Right-handed adults were asked to give verbal estimates of distance reachability using motor imagery in conditions with no visual background or with visual background. In each condition, four delays were used: 0, 1, 2, and 4 sec. There were no distinctions between conditions; however, comparisons at each delay were significantly different at 2 and 4 sec. With each delay, participants displayed significantly less error when the visual background was presented. These findings are consistent with the notion that motor simulation approximates motor planning and execution.

Individual goals interact with dyad goals to constrain and facilitate the formation of interpersonal patterns of coordination.

Two experiments were undertaken to examine the spontaneous and intentional formation of interpersonal coordination patterns within dyads. In both experiments, each individual in a dyad was given a pre-set amplitude goal of tracing a 3 cm or 15 cm line to maintain over a trial. Smaller amplitudes were associated with faster movement frequencies compared to larger amplitudes in both experiments. All trials started with the partners in the dyads not seeing each other, and at the half-way point within a trial vision of the partner was provided. In experiment 1, each individual was told to watch their partners hand in the view segment, yet maintain the amplitude goal. The pre-set amplitude goals limited the emergence of spontaneous interpersonal coordination in the form of frequency-locking and phase-entrainment. In experiment 2, the individuals in the dyad were told to intentionally coordinate at either a defined in-phase or anti-phase pattern of coordination when entering the view segment of a trial. All dyads formed the required coordination patterns at a 1:1 frequency-locking across 90% of trials when entering the view segment. However, the pre-set amplitudes still influenced performance of individuals in terms of movement amplitude and frequency modulations when intentionally forming the required coordination patterns. The proposed hypotheses and the interpretation of the results are framed within the coordination dynamics theory of perception-action processes.

Elderly may benefit more from motor imagery training in gaining muscle strength than young adults: A systematic review and meta-analysis.

Objective: The current review was aimed to determine the effectiveness of mental imagery training (MIT) on the enhancement of maximum voluntary muscle contraction (MVC) force for healthy young and old adults. Data sources: Six electronic databases were searched from July 2021 to March 2022. Search terms included: "motor imagery training," "motor imagery practice," "mental practice," "mental training," "movement imagery," "cognitive training," "strength," "force," "muscle strength," "performance," "enhancement," "improvement," "development," and "healthy adults." Study selection and data extraction: Randomized controlled trials of MIT in enhancing muscle strength with healthy adults were selected. The decision on whether a study met the inclusion criteria of the review was made by two reviewers independently. Any disagreements between the two reviewers were first resolved by discussion between the two reviewers. If consensus could not be reached, then it would be arbitrated by a third reviewer. Data synthesis: Twenty-five studies including both internal MIT and external MIT were included in meta-analysis for determining the efficacy of MIT on enhancing muscle strength and 22 internal MIT were used for subgroup analysis for examining dose-response relationship of MIT on MVC. Results: MIT demonstrated significant benefit on enhancing muscle strength when compared with no exercise, Effect Size (ES), 1.10, 95% confidence interval (CI), 0.89-1.30, favoring MIT, but was inferior to physical training (PT), ES, 0.38, 95% CI, 0.15-0.62, favoring PT. Subgroup analysis demonstrated that MIT was more effective for older adults (ES, 2.17, 95% CI, 1.57-2.76) than young adults (ES, 0.95, 95% CI, 0.74-1.17), p = 0.0002, and for small finger muscles (ES, 1.64, 95% CI, 1.06-2.22) than large upper extremity muscles (ES, 0.86, 95% CI, 0.56-1.16), p = 0.02. No significant difference was found in the comparison of small finger muscles and large lower extremity muscles, p = 0.19 although the ES of the former (ES, 1.64, 95% CI, 1.06-2.22) was greater than that of the later (ES, 1.20, 95%, 0.88-1.52). Conclusion: This review demonstrates that MIT has better estimated effects on enhancing MVC force compared to no exercise, but is inferior to PT. The combination of MIT and PT is equivalent to PT alone in enhancing muscle strength. The subgroup group analysis further suggests that older adults and small finger muscles may benefit more from MIT than young adults and larger muscles.

Calibrating Wrist-Worn Accelerometers for Physical Activity Assessment in Preschoolers: Machine Learning Approaches.

BACKGROUND: Physical activity (PA) level is associated with multiple health benefits during early childhood. However, inconsistency in the methods for quantification of PA levels among preschoolers remains a problem. OBJECTIVE: This study aimed to develop PA intensity cut points for wrist-worn accelerometers by using machine learning (ML) approaches to assess PA in preschoolers. METHODS: Wrist- and hip-derived acceleration data were collected simultaneously from 34 preschoolers on 3 consecutive preschool days. Two supervised ML models, receiver operating characteristic curve (ROC) and ordinal logistic regression (OLR), and one unsupervised ML model, k-means cluster analysis, were applied to establish wrist-worn accelerometer vector magnitude (VM) cut points to classify accelerometer counts into sedentary behavior, light PA (LPA), moderate PA (MPA), and vigorous PA (VPA). Physical activity intensity levels identified by hip-worn accelerometer VM cut points were used as reference to train the supervised ML models. Vector magnitude counts were classified by intensity based on three newly established wrist methods and the hip reference to examine classification accuracy. Daily estimates of PA were compared to the hip-reference criterion. RESULTS: In total, 3600 epochs with matched hip- and wrist-worn accelerometer VM counts were analyzed. All ML approaches performed differently on developing PA intensity cut points for wrist-worn accelerometers. Among the three ML models, k-means cluster analysis derived the following cut points: ≤2556 counts per minute (cpm) for sedentary behavior, 2557-7064 cpm for LPA, 7065-14532 cpm for MPA, and ≥14533 cpm for VPA; in addition, k-means cluster analysis had the highest classification accuracy, with more than 70% of the total epochs being classified into the correct PA categories, as examined by the hip reference. Additionally, k-means cut points exhibited the most accurate estimates on sedentary behavior, LPA, and VPA as the hip reference. None of the three wrist methods were able to accurately assess MPA. CONCLUSIONS: This study demonstrates the potential of ML approaches in establishing cut points for wrist-worn accelerometers to assess PA in preschoolers. However, the findings from this study warrant additional validation studies.

A question of intention in motor imagery.

We examined the question-is the intention of completing a simulated motor action the same as the intention used in processing overt actions? Participants used motor imagery to estimate distance reachability in two conditions: Imagery-Only (IO) and Imagery-Execution (IE). With IO (red target) only a verbal estimate using imagery was given. With IE (green target) participants knew that they would actually reach after giving a verbal estimate and be judged on accuracy. After measuring actual maximum reach, used for the comparison, imagery targets were randomly presented across peripersonal- (within reach) and extrapersonal (beyond reach) space. Results indicated no difference in overall accuracy by condition, however, there was a significant distinction by space; participants were more accurate in peripersonal space. Although more research is needed, these findings support an increasing body of evidence suggesting that the neurocognitive processes (in this case, intention) driving motor imagery and overt actions are similar.

Do children perceive postural constraints when estimating reach or action planning?

Estimation of whether an object is reachable from a specific body position constitutes an important aspect in effective motor planning. Researchers who estimate reachability by way of motor imagery with adults consistently report the tendency to overestimate, with some evidence of a postural effect (postural stability hypothesis). This idea suggests that perceived reaching limits depend on an individual's perceived postural constraints. Based on previous work with adults, the authors expected a significant postural effect with the Reach 2 condition, as evidenced by reduced overestimation. Furthermore, the authors hypothesized that the postural effect would be greater in younger children. They then tested these propositions among children aged 7, 9, and 11 years by asking them to estimate reach while seated (Reach 1) and in the more demanding posture of standing on 1 foot and leaning forward (Reach 2). Results indicated no age or condition difference, therefore providing no support for a postural effect. When the authors compared these data to a published report of adults, a developmental difference emerged. That is, adults recognize the perceived postural constraint of the standing position resulting in under- rather than overestimation, as displayed in the seated condition. Although preliminary, these observations suggest that estimates of reach (action planning) continue to be refined between late childhood and young adulthood.

Testing the distinctiveness of visual imagery and motor imagery in a reach paradigm.

We examined the distinctiveness of motor imagery (MI) and visual imagery (VI) in the context of perceived reachability. The aim was to explore the notion that the two visual modes have distinctive processing properties tied to the two-visual-system hypothesis. The experiment included an interference tactic whereby participants completed two tasks at the same time: a visual or motor-interference task combined with a MI or VI-reaching task. We expected increased error would occur when the imaged task and the interference task were matched (e.g., MI with the motor task), suggesting an association based on the assumption that the two tasks were in competition for space on the same processing pathway. Alternatively, if there were no differences, dissociation could be inferred. Significant increases in the number of errors were found when the modalities for the imaged (both MI and VI) task and the interference task were matched. Therefore, it appears that MI and VI in the context of perceived reachability recruit different processing mechanisms.

Is perceived motor competence a constraint in children's action planning?

A form of action representation of developmental interest is reach estimation-the perceptual and cognitive judgment of whether an object is within or out of reach. A common observation among children is overestimation, which, speculatively, has been linked to perceived motor competence (PMC). The authors examined the PMC effect on reachability among 7-, 9-, and 11-year-old children. The authors predicted that with higher PMC, participants would display greater overestimation and that this outcome would show a developmental trend with younger children displaying greater overestimation complementing higher PMC scores. Results revealed no age differences in total error for reach, and all age groups overestimated. Regarding PMC, the 7-year-old childrens' scores were significantly higher than those of their older counterparts. However, relation analyses revealed no support for the idea that PMC was significantly associated with reachability. The findings suggested that a general measure of PMC is not a good predictor of childrens' action planning through reach estimation. Furthermore, if PMC in some form is a psychological constraint, future studies should be tied to context-specific measures of perceived abilities in relation to the specificity of the task.

Estimation of reach in peripersonal and extrapersonal space: a developmental view.

This study explored the developmental nature of action processing via estimation of reach in peripersonal and extrapersonal space. Children 5 to 11 years of age and adults were tested for estimates of reach to targets presented randomly at seven midline locations. Target distances were scaled to the individual based on absolute maximum reach. While there was no difference between age groups for total error, a significant distinction emerged in reference to space. With children, significantly more error was exhibited in extrapersonal space; no difference was found with adults. The groups did not differ in peripersonal space; however, adults were substantially more accurate with extrapersonal targets. Furthermore, children displayed a greater tendency to overestimate. In essence, these data reveal a body-scaling problem in children in estimating reach in extrapersonal space. Future work should focus on possible developmental differences in use of visual information and state of confidence.

Examining the effects of postural constraints on estimating reach.

The tendency to overestimate has consistently been reported in studies of reachability estimation. According to one of the more prominent explanations, the postural stability hypothesis, the perceived reaching limit depends on the individual's perceived postural constraints. To test that proposition, the authors compared estimates of reachability of 38 adults (a) in the seated posture (P1) and (b) in the more demanding posture of standing on one foot and leaning forward (P2). Although there was no difference between conditions for total error, results for the distribution and direction of error indicated that participants overestimated in the P1 condition and underestimated in the P2 condition. It therefore appears that perceived postural constraints could be a factor in judgments of reachability. When participants in the present study perceived greater postural demands, they may have elected to program a more conservative strategy that resulted in underestimation.

Effects of Physical Practice and Imagery Practice on Bilateral Transfer in Learning a Sequential Tapping Task.

Recent research on bilateral transfer suggests that imagery training can facilitate the transfer of motor skill from a trained limb to that of an untrained limb above and beyond that of physical practice. To further explore this effect, the present study examined the influence of practice duration and task difficulty on the extent to which imagery training and physical training influences bilateral transfer of a sequential key pressing task. In experiment 1, participants trained on the key pressing task using their non-dominant arm under one of three conditions (physical practice, imagery practice, and no practice). In a subsequent bilateral transfer test, participants performed the sequential task using their untrained dominant arm in either an original order or mirror-ordered sequence. In experiment 2, the same procedures were followed as in experiment 1 except that participants trained with their dominant arm and performed the bilateral transfer task with their non-dominant arm. Results indicated that with extended practice beyond what has been employed in previous studies, physical practice is more effective at facilitating bilateral transfer compared to training with imagery. Interestingly, significant bilateral transfer was only observed for transfer from the non-dominant to the dominant arm with no differences observed between performing the task in an original or mirror ordered sequence. Overall, these findings suggest that imagery training may benefit bilateral transfer primarily at the initial stages of learning, but with extended training, physical practice leads to larger influences on transfer.

HIV/AIDS in Lebanese prisons: challenges and proposed actions.

PURPOSE: The purpose of this paper is to discuss the extent of human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) crisis in Lebanese prisons, propose functional reforms for Roumieh prisons (the country's largest male top-security prison), and outline the main challenges to HIV/AIDS prevention, intervention, and treatment. DESIGN/METHODOLOGY/APPROACH: All recommendations were based on previous successful stories, international prison standards as well as cultural considerations. FINDINGS: This paper argues that prevention and interventions starts within the prison community including inmates, guards, and other prison and provision of appropriate health care, education, and prison infrastructure. SOCIAL IMPLICATIONS: These strategies are not only important in limiting prevention and transmission of HIV/AIDS, but also contribute in optimizing quality of life within the prison system. ORIGINALITY/VALUE: This paper is the first of its kind to discuss the prison situation in Lebanese prisons in terms of public health promotion and reforms.

Determination of Anaerobic Threshold by Heart Rate or Heart Rate Variability using Discontinuous Cycle Ergometry.

The purpose was to determine if heart rate (HR) and heart rate variability (HRV) responses would reflect anaerobic threshold (AT) using a discontinuous, incremental, cycle test. AT was determined by ventilatory threshold (VT). Cyclists (30.6±5.9y; 7 males, 8 females) completed a discontinuous cycle test consisting of 7 stages (6 min each with 3 min of rest between). Three stages were performed at power outputs (W) below those corresponding to a previously established AT, one at W corresponding to AT, and 3 at W above those corresponding to AT. The W at the intersection of the trend lines was considered each metric's "threshold". The averaged stage data for Ve, HR, and time- and frequency-domain HRV metrics were plotted versus W. The W at the "threshold" for the metrics of interest were compared using correlation analysis and paired-sample t-test. In all, several heart rate-related parameters accurately reflected AT with significant correlations (p≤0.05) were observed between AT W and HR, mean RR interval (MRR), low and high frequency spectral energy (LF and HR, respectively), high frequency peak (fHF), and HFxfHF metrics' threshold W (i.e., MRRTW, etc.). Differences in HR or HRV metric threshold W and AT for all subjects were less than 14 W. The steady state data from discontinuous protocols may allow for a true indication of steady-state physiologic stress responses and corresponding W at AT, compared to continuous protocols using 1-2 min exercise stages.

Association between imagined and actual functional reach (FR): a comparison of young and older adults.

Recent studies indicate that the ability to mentally represent action using motor imagery declines with advanced age (>64 years). As the ability to represent action declines, the elderly may experience increasing difficulty with movement planning and execution. Here, we determined the association between estimation of reach via use of motor imagery and actual FR. Young adults (M=22 years) and older adults (M=66 years) estimated reach while standing with targets randomly presented in peripersonal (within actual reach) and extrapersonal (beyond reach) space. Imagined responses were compared to the individual's scaled maximum reach. FR, also while standing, was assessed using the standardized Functional Reach Test (FRT). Results for total score estimation accuracy showed that there was no difference for age; however, results for mean bias and distribution of error revealed that the older group underestimated while the younger group overestimated. In reference to FR, younger adults outperformed older adults (30 versus 14in.) and most prominent, only the younger group showed a significant relationship between estimation and FR. In addition to gaining insight to the effects of advanced age on the ability to mentally represent action and its association with movement execution, these results although preliminary, may have clinical implications based on the question of whether motor imagery training could improve movement estimations and how that might affect actual reach.

Míranos! Look at us, we are healthy! An environmental approach to early childhood obesity prevention.

BACKGROUND: Obesity prevention research is sparse in young children at risk for obesity. This study tested the effectiveness of a culturally tailored, multicomponent prevention intervention to promote healthy weight gain and gross motor development in low-income preschool age children. METHODS: Study participants were predominantly Mexican-American children (n = 423; mean age = 4.1; 62% in normal weight range) enrolled in Head Start. The study was conducted using a quasi-experimental pretest/posttest design with two treatment groups and a comparison group. A center-based intervention included an age-appropriate gross motor program with structured outdoor play, supplemental classroom activities, and staff development. A combined center- and home-based intervention added peer-led parent education to create a broad supportive environment in the center and at home. Primary outcomes were weight-based z-scores and raw scores of gross motor skills of the Learning Achievement Profile Version 3. RESULTS: Favorable changes occurred in z-scores for weight (one-tailed p < 0.04) for age and gender among children in the combined center- and home-based intervention compared to comparison children at posttest. Higher gains of gross motor skills were found in children in the combined center- and home-based (p < 0.001) and the center-based intervention (p < 0.01). Children in both intervention groups showed increases in outdoor physical activity and consumption of healthy food. Process evaluation data showed high levels of protocol implementation fidelity and program participation of children, Head Start staff, and parents. CONCLUSION: The study demonstrated great promise in creating a health-conducive environment that positively impacts weight and gross motor skill development in children at risk for obesity. Program efficacy should be tested in a randomized trial.