At-home computerized executive-function training to improve cognition and mobility in normal-hearing adults and older hearing aid users: a multi-centre, single-blinded randomized controlled trial.

BACKGROUND: Hearing loss predicts cognitive decline and falls risk. It has been argued that degraded hearing makes listening effortful, causing competition for higher-level cognitive resources needed for secondary cognitive or motor tasks. Therefore, executive function training has the potential to improve cognitive performance, in turn improving mobility, especially when older adults with hearing loss are engaged in effortful listening. Moreover, research using mobile neuroimaging and ecologically valid measures of cognition and mobility in this population is limited. The objective of this research is to examine the effect of at-home cognitive training on dual-task performance using laboratory and simulated real-world conditions in normal-hearing adults and older hearing aid users. We hypothesize that executive function training will lead to greater improvements in cognitive-motor dual-task performance compared to a wait-list control group. We also hypothesize that executive function training will lead to the largest dual-task improvements in older hearing aid users, followed by normal-hearing older adults, and then middle-aged adults. METHODS: A multi-site (Concordia University and KITE-Toronto Rehabilitation Institute, University Health Network) single-blinded randomized controlled trial will be conducted whereby participants are randomized to either 12 weeks of at-home computerized executive function training or a wait-list control. Participants will consist of normal-hearing middle-aged adults (45-60 years old) and older adults (65-80 years old), as well as older hearing aid users (65-80 years old, ≥ 6 months hearing aid experience). Separate samples will undergo the same training protocol and the same pre- and post-evaluations of cognition, hearing, and mobility across sites. The primary dual-task outcome measures will involve either static balance (KITE site) or treadmill walking (Concordia site) with a secondary auditory-cognitive task. Dual-task performance will be assessed in an immersive virtual reality environment in KITE's StreetLab and brain activity will be measured using functional near infrared spectroscopy at Concordia's PERFORM Centre. DISCUSSION: This research will establish the efficacy of an at-home cognitive training program on complex auditory and motor functioning under laboratory and simulated real-world conditions. This will contribute to rehabilitation strategies in order to mitigate or prevent physical and cognitive decline in older adults with hearing loss. TRIAL REGISTRATION: Identifier: NCT05418998. https://clinicaltrials.gov/ct2/show/NCT05418998.

Kinematics and muscle activation patterns during a maximal voluntary rate activity in healthy elderly and young adults.

BACKGROUND: Maximal voluntary rate (MVR) performance tasks can provide important age-related information to the limiting factors associated with movement and the development of fatigue. AIM: To determine whether kinematic and muscle activation patterns during an MVR task differ between young and older adults. METHODS: We continuously measured frequency, amplitude, peak velocity, index of co-contraction and median frequencies of the index finger flexors and extensors during a 20-s MVR task in 10 young and 10 older subjects. RESULTS: Index finger amplitude and peak velocity in flexion and extension were significantly lower in the older group. During the MVR, amplitude was maintained in the old (1-4 s, 53.2° ± 2.8° vs. 15-19 s, 48.6° ± 3.2°, ns) but not in the younger group (1-4 s, 64.9° ± 4.9° vs. 15-19 s, 59.4° ± 3.3°; p = 0.001). Frequency declined in the young (1-4 s, 5.2 ± 0.24 Hz vs. 15-19 s, 4.4 ± 0.25 Hz; p = 0.001) and old (1-4 s, 4.6 ± 0.17 Hz vs. 15-19 s, 4.0 ± 0.15 Hz; p = 0.01). Similarly, peak flexion velocity of the young (1-4 s, 1.77 ± 0.07 × 103 °/s vs. 15-19 s, 1.01 ± 0.07 × 103 °/s, p = 0.01) and older groups (1-4 s, 1.04 ± 0.07 × 103 °/s vs. 15-19 s, 0.78 ± 0.06 × 103 °/s; p = 0.016) as well as peak extension velocity of the young (1-4 s, 1.01 ± 0.053 × 103 °/s vs. 15-19 s, 0.78 ± 0.06 × 103 °/s, p = 0.01) and older groups (1-4 s, 0.72 ± 0.04 × 103 °/s vs. 15-19 s, 0.58 ± 0.05 × 103 °/s, p = 0.012) significantly decreased throughout the MVR. Median frequency of the flexors and extensors were maintained and were not different between groups. Only the older group experienced an increase in the index of co-contraction. CONCLUSION: The changes in kinematics over time are not a result of a decrease in pre-post test force or velocity, but rather central factors affecting movement coordination.

Integration of active pauses and pattern of muscular activity during computer work.

Submaximal isometric muscle contractions have been reported to increase variability of muscle activation during computer work; however, other types of active contractions may be more beneficial. Our objective was to determine which type of active pause vs. rest is more efficient in changing muscle activity pattern during a computer task. Asymptomatic regular computer users performed a standardised 20-min computer task four times, integrating a different type of pause: sub-maximal isometric contraction, dynamic contraction, postural exercise and rest. Surface electromyographic (SEMG) activity was recorded bilaterally from five neck/shoulder muscles. Root-mean-square decreased with isometric pauses in the cervical paraspinals, upper trapezius and middle trapezius, whereas it increased with rest. Variability in the pattern of muscular activity was not affected by any type of pause. Overall, no detrimental effects on the level of SEMG during active pauses were found suggesting that they could be implemented without a cost on activation level or variability. Practitioner Summary: We aimed to determine which type of active pause vs. rest is best in changing muscle activity pattern during a computer task. Asymptomatic computer users performed a standardised computer task integrating different types of pauses. Muscle activation decreased with isometric pauses in neck/shoulder muscles, suggesting their implementation during computer work.

The Effects of Age and Hearing Loss on Dual-Task Balance and Listening.

Objectives: Among older adults (OA), hearing loss is associated with an increased risk for falls. The aim of the present study was to experimentally investigate the cognitive compensation hypothesis, wherein decreased auditory and motor functioning are compensated by the recruitment of cognitive resources. Method: Twenty-nine younger adults (YA), 26 OA, and 32 OA with age-related hearing loss (ARHL) completed a dual-task paradigm consisting of cognitive and balance recovery tasks performed singly and concurrently. The auditory stimuli were presented with or without background noise. Results: Both older adult groups performed significantly worse than YA on the cognitive task in noisy conditions and ARHL also demonstrated disproportionate negative effects of dual-tasking and noise. The kinematic data indicated that OA and ARHL demonstrated greater plantarflexion when compared with YA. Conversely, YA showed greater hip extension in response to dual-tasking. Discussion: The cognitive and balance results suggest that YA were able to flexibly allocate their attention between tasks, whereas ARHL exhibited prioritization of posture over cognitive performance.

The effect of simultaneously and sequentially delivered cognitive and aerobic training on mobility among older adults with hearing loss.

BACKGROUND: Older adults exhibit declines in auditory and motor functioning, which are compensated for through the recruitment of cognitive resources. Cognitive or physical training alone has been shown to improve cognitive functioning and transfer to motor tasks, but results are mixed when these are combined in studies of healthy older adults, and few studies have included those with age-related hearing loss (ARHL), who are at a higher risk of falls. RESEARCH QUESTION: To examine format effects in mixed training, we used a repeated measures intervention design to compare the efficacy of Simultaneous and Sequential multimodal training formats. METHODS: 42 older adults (Mage = 68.05, SDage = 4.65, females = 26) with (ARHL) and without hearing loss (OAH) completed an intervention study consisting of 12 sessions of multimodal training (computerized cognitive dual-task and recumbent aerobic cycling). Participants were randomly assigned to either the Simultaneous (concurrent cognitive and aerobic) or Sequential training group (cognitive followed by aerobic) and completed assessments of single- and dual-task mobility concurrent with an auditory working memory task. Training gains were assessed with repeated measures ANOVAs using magnitude of improvement from pre- to post-training on primary outcome measures as the dependent variable. RESULTS: Gains in auditory working memory were greater in the Sequential group than Simultaneous particularly among OAH. ARHL participants were unaffected by format. While all participants improved on a measure of chair rises, there was no benefit to standing balance. The results demonstrate an advantage to Sequential training, suggesting a benefit to focusing on each task in isolation. SIGNIFICANCE: The gains noted in the ARHL indicate the potential benefit of incorporating cognitive remediation into traditional audiological rehabilitation. Moreover, it is important to consider the cost of dividing attention when combining training.

Test-retest reliability of a balance testing protocol with external perturbations in young healthy adults.

External perturbations are utilized to challenge balance and mimic realistic balance threats in patient populations. The reliability of such protocols has not been established. The purpose was to examine test-retest reliability of balance testing with external perturbations. Healthy adults (n=34; mean age 23 years) underwent balance testing over two visits. Participants completed ten balance conditions in which the following parameters were combined: perturbation or non-perturbation, single or double leg, and eyes open or closed. Three trials were collected for each condition. Data were collected on a force plate and external perturbations were applied by translating the plate. Force plate center of pressure (CoP) data were summarized using 13 different CoP measures. Test-retest reliability was examined using intraclass correlation coefficients (ICC) and Bland-Altman plots. CoP measures of total speed and excursion in both anterior-posterior and medial-lateral directions generally had acceptable ICC values for perturbation conditions (ICC=0.46 to 0.87); however, many other CoP measures (e.g. range, area of ellipse) had unacceptable test-retest reliability (ICC<0.70). Improved CoP measures were present on the second visit indicating a potential learning effect. Non-perturbation conditions generally produced more reliable CoP measures than perturbation conditions during double leg standing, but not single leg standing. Therefore, changes to balance testing protocols that include external perturbations should be made to improve test-retest reliability and diminish learning including more extensive participant training and increasing the number of trials. CoP measures that consider all data points (e.g. total speed) are more reliable than those that only consider a few data points.

A reproducible method for studying three-dimensional knee kinematics.

The methods used in movement analysis often rely on the definition of joint coordinate systems permitting three-dimensional (3D) kinematics. The first aim of this research project was to present a functional and postural method (FP method) to define a bone-embedded anatomical frame (BAF) on the femur and tibia, and, subsequently, a knee joint coordinate system. The repeatability of the proposed method was also assessed. Using FP method to define the BAFs, 4 kinematic parameters (flexion/extension, abduction/adduction, tibial internal/external rotation, and antero-posterior translation) were computed for 15 subjects walking on a treadmill. The repeatability for all four kinematic parameters was then assessed, using intra- and inter-observer settings. After pooling the results for all observers, the mean repeatability value ranged between 0.4 degrees and 0.8 degrees for rotation angles and between 0.8 and 2.2 mm for translation.

Effect of ski binding parameters on knee biomechanics: a three-dimensional computational study.

INTRODUCTION: Downhill skiing is a relatively safe sport, but many potentially avoidable injuries do occur. Whereas tibia and ankle injuries have been declining, severe knee sprains usually involving the anterior cruciate ligament (ACL) have increased from the 1970s to the 1990s. The goal of the present study was to evaluate the effect of the position of the binding pivot point and binding release characteristics on ACL strain during a phantom-foot fall. METHODS: We computed ACL strain using a biomechanical computer knee model to simulate the phantom-foot ACL-injury mechanism. This mechanism, which is one of the most common mechanisms of ACL injury in downhill skiing, occurs when the weight of the skier is on the inner edge of the ski during a backward fall, resulting in a sharp uncontrolled inward turn of the ski. RESULTS: The model predicts, that under simulated phantom-foot conditions, a binding with fast-release characteristics with a pivot positioned in front of the center of the boot produces less strain on the ACL. Current bindings have their pivot point approximately at the center of the heel radius. A pivot positioned at the back of the binding is more effective for sensing loads that occur at the tip of the ski. However, it is less effective for sensing loads that occur at the tail of the ski and, therefore, offers less protection during a phantom-foot fall. CONCLUSION: A binding with two pivot points, one positioned in front and the other at the back, could sense twist loads applied to the ski both at the front and at the back, and might, therefore, be a solution to reduce the occurrence of ACL injuries.

The hygienist's role in improving children's oral health throughout their development.

Improving oral hygiene in children is one of the most challenging aspects of the preventive dental practice because their dentition, dexterity, and emotional maturity are simultaneously developing. This article discusses the role of the hygienist in providing oral health care and education in the context of developing preventive care programs that can be tailored to meet the needs of children in different age groups. Particular attention will be given to identifying proven approaches to motivating children and their parents to respond positively to oral health advice and hygiene instruction.

Unilateral eccentric exercise of the knee flexors affects muscle activation during gait.

Uni-lateral muscle soreness is common yet the effects on gait or electromyographic (EMG) activity are unknown. The purpose of our study was to induce delayed onset muscle soreness (DOMS) in the knee flexor group and measure the resultant change in EMG activity and knee motion during gait. Nine healthy subjects participated in the study. Measures of function, evoked tenderness of the biceps femoris, as well as knee angle, and EMG activity during gait were assessed prior and 48 h after an eccentric exercise protocol. DOMS was induced unilaterally in the knee flexors using an isokinetic dynamometer and subjects exercised until they could not generate 50% of their maximal voluntary isometric contraction (MVIC). There was a significant decrease in biceps femoris activity after DOMS during the last phase of gait. Moreover, there was a day × phase interaction for gastrocnemius activity with the last two phases displaying an increase in activity. There was no significant change in knee angle during gait. The decrease in biceps femoris activity as well as the increase in gastrocnemius activity could be evidence of a protective mechanism designed to decrease activity of the sore muscle while increasing the activity of a synergistic muscle.

Direction-dependent neck and trunk postural reactions during sitting.

Postural reactions in healthy individuals in the seated position have previously been described and have been shown to depend on the direction of the perturbation; however the neck response following forward and backward translations has not been compared. The overall objective of the present study was to compare neck and trunk kinematic, kinetic and electromyographic (EMG) stabilization patterns of seated healthy individuals to forward and backward translations. Ten healthy individuals, seated on a chair fixed onto a movable platform, were exposed to forward and backward translations (distance=0.15m, peak acceleration=1.2m/s(2)). The head and trunk kinematics as well as the EMG activity of 16 neck and trunk muscles were recorded. Neck and trunk angular displacements were computed in the sagittal plane. The centers of mass (COMs) of the head (HEAD), upper thorax (UPTX), lower thorax (LOWTX) and abdomen (ABDO) segments were also computed. Moments of force at the C7-T1 and L5-S1 levels were calculated using a top-down, inverse dynamics approach. Forward translations provoked greater overall COM peak displacements. The first peak of moment of force was also reached earlier following forward translations which may have played a role in preventing the trunk from leaning backwards. These responses can be explained by the higher postural threat imposed by a forward translation.

Whiplash-associated disorders affect postural reactions to antero-posterior support surface translations during sitting.

Previous studies have shown that individuals with WAD display decreased postural stability during standing and walking tasks. However, their ability to maintain seated upright posture has never been investigated. The objective of this study was to characterize kinematic and electromyographic postural stabilization patterns in individuals with chronic WAD and to compare these patterns with those in an able-bodied control group. Ten individuals with WAD and an age- and gender-matched group of healthy individuals were exposed to sudden forward and backward support surface translations while they were seated. Neck and trunk muscle activity and angular displacements as well as centers of mass (COMs) linear displacements at four levels of the head and trunk were computed. The displacement onset of the combined head, arms and trunk COM was significantly delayed in persons with WAD. However, their peak trunk angles were smaller and were reached sooner. In the WAD group, the activation onset of the lumbar erector spinae was less affected by perturbation direction and the sternocleidomastoid muscle, a neck flexor, showed a trend towards being activated later, compared to the healthy group. These results suggest that individuals with WAD may alter stretch reflex threshold and/or elicit a learned response for pain avoidance that may be direction-specific. Such findings highlight the importance of assessing both spatial and temporal characteristics across different levels of the spinal musculoskeletal system to evaluate multidirectional postural responses in WAD individuals.

A paradigm to assess postural responses triggered by anteroposterior translations in healthy seated individuals.

Postural adjustments following mechanical perturbations have been studied in healthy seated humans. However, little is known on the minimal intensity that should be used to provoke a reaction. This knowledge could be essential to assess seated postural deficits in some pathological populations. The goal of the present study was to identify a low-intensity perturbation that could elicit postural reactions in healthy seated individuals. Six healthy participants sat on an adapted ergonomic chair fixed on a moveable support surface that was submitted to forward and backward translations. The head and trunk kinematics as well as the activity of sixteen neck and trunk muscles were recorded. The head, arm and trunk center of mass was computed using kinematics and standard anthropometric tables. We found that ramp displacements with an acceleration profile reaching a maximal value of 1.17 m/s(2) elicited reliable kinematic and electromyographic reactions across participants. Head and trunk segments initially responded opposite to the direction of translation, then reversed direction. Median peak-to-peak angular displacements in the neck, head and trunk, respectively, reached 3.6 degrees, 7.0 degrees and 7.1 degrees for forward translations, and 4.0 degrees, 8.2 degrees and 7.0 degrees for backward translations. For forward translations, neck and trunk flexor muscles were activated first, followed by the extensor muscles, whereas for backward translations, extensor muscles were activated first, followed by flexors. Although this perturbation is of low-intensity compared to those typically used previously to evoke postural reactions, this stimulus is sufficient to elicit a reliable response. We suggest that such a perturbation could be used to assess the physical condition of individuals with neck injuries.

Referent configuration of the body: a global factor in the control of multiple skeletal muscles.

In addition to local biomechanical and reflex factors influencing muscle activation, global factors may be used by the nervous system to control all muscles in a coherent and task-specific way. It has been hypothesized that a virtual or referent (R) configuration of the body determined by muscle recruitment thresholds specified by neural control levels is such a factor. Due to the threshold nature of the R configuration, the activity of each muscle depends on the difference between the actual (Q) and the R configuration of the body. The nervous system modifies the R configuration to produce movement. One prediction of this hypothesis is that the Q and R configurations may match each other, most likely in movements with reversals in direction, resulting in a minimum in the electromyographic (EMG) activity level of muscles involved. The depth of the minima is constrained by the degree of coactivation of opposing muscle groups. Another prediction is that EMG minima in the activity of multiple muscles may occur not only when the movement is assisted but also when it is opposed by external forces (e.g., gravity). To verify these predictions, we analyzed EMG patterns of 16-21 functionally diverse muscles of the legs, trunk, and arms during jumping and stepping in place. One EMG minimum in the activity of all muscles regularly occurred near the apex of the jump. A minimum was also observed near the point of transition of the body from flexion to extension leading to a jump. During stepping in place, the activity of muscles of each side of the body was usually minimized near the beginning and near the end of the stance phase as well as during the maximum elevation of the foot. Since EMG minima occurred not only during gravity-assisted but also gravity-opposed movement reversals, it is concluded that neural factors (such as matching between the Q and R) rather than mechanical factors are responsible for minimizing the EMG activity in these movements.

Interjoint coordination in lower limbs during different movements in humans.

Redundancy is associated with the ability of the nervous system to select different interjoint coordinations and movement trajectories to achieve the same motor goal. The nervous system may coordinate multiple degrees of freedom (DF) by combining them in a task-specific way to control them as a unit or synergy. Some movements may be accomplished using only one synergy, whereas other movements may employ several synergies. To investigate the problem of interjoint coordination, we applied principal component (PC) analysis to eight types of movement in healthy male subjects: forward squats, backward squats, sideways squats, squats on one leg, walking three steps, stepping in place, going up a step, and going down a step. Angular changes in four DF were analyzed: thigh flexion-extension, knee flexion-extension, ankle flexion-extension, thigh abduction-adduction, with the former three DF investigated in all movements. For many movements, two synergies were sufficient to account for more than 95% of DF angular excursions. Squatting on one leg could be described using only one synergy (99%). The angle between the vectors representing PCs for movements produced with the right and left legs could be less than 10 degrees for some movements but could reach 25 degrees for other movements. The nervous system may thus use somewhat different interjoint coordinations while producing movements on the right and the left sides. The angle between the first PCs of different movements could be smaller than 10 degrees. Thus there may be a common but adjustable basic synergy that is used to produce different movements. Additional synergies provide the transition from one movement to another.