Motor performance and motor learning as a function of age and fitness

Association Between Physical Activity and Performance in Skill Learning Among Older Adults Based on Cognitive Function

BACKGROUND/OBJECTIVES

Most older adults experience cognitive and physical functioning problems; however, they require the ability to learn skills in response to age-related or social environmental changes for independent living. This study aimed to clarify the associations between age-related physical activity and performance in skill learning tasks based on cognitive function.

METHODS

Fifty-eight adults participated in this study and were divided into two groups: the control group (aged under 65 years) and older adult group (aged over 65). All the participants performed two-skill learning exercises based on cognitive function. Habitual exercise was measured using an accelerometer and a self-reported questionnaire.

RESULTS

At baseline, the scores on skill tasks were lower in the older adult group than in the control group and were associated with habitual exercise and motor performance. Skill acquisition, observed in both groups, was associated with age and self-reported physical activity. Retention of the acquired skill was not associated with habitual exercise, and it declined significantly in the older group.

CONCLUSIONS

Skill acquisition was maintained regardless of age; however, the ability to retain the acquired skills decreased among the older adults. Habitual physical activity was associated with skill acquisition but not the retention of the acquired skill. Significance/Implications: The study findings highlight the association between habitual exercise and motor skill learning in older adults, providing insight for practitioners in the rehabilitation and health care fields.

Older and younger adults differ in time course of skill acquisition but not in overall improvement in a bimanual visuomotor tracking task

Manual motor performance declines with age, but the extent to which age influences the acquisition of new skills remains a topic of debate. Here, we examined whether older healthy adults show less training-dependent performance improvements during a single session of a bimanual pinch task than younger adults. We also explored whether physical and cognitive factors, such as grip strength or motor-cognitive ability, are associated with performance improvements. Healthy younger (n = 16) and older (n = 20) adults performed three training blocks separated by short breaks. Participants were tasked with producing visually instructed changes in pinch force using their right and left thumb and index fingers. Task complexity was varied by shifting between bimanual mirror-symmetric and inverse-asymmetric changes in pinch force. Older adults generally displayed higher visuomotor force tracking errors during the more complex inverse-asymmetric task compared to younger adults. Both groups showed a comparable net decrease in visuomotor force tracking error over the entire session, but their improvement trajectories differed. Young adults showed enhanced visuomotor tracking error only in the first block, while older adults exhibited a more gradual improvement over the three training blocks. Furthermore, grip strength and performance on a motor-cognitive test battery scaled positively with individual performance improvements during the first block in both age groups. Together, the results show subtle age-dependent differences in the rate of bimanual visuomotor skill acquisition, while overall short-term learning ability is maintained.

Scoliosis and Lower Limb Inequality: To Lift or Not to Lift, That Is the Question

In subjects with scoliotic alterations of the spine, asymmetrical lengths of the lower limbs are frequently observed, a condition commonly referred to as leg length inequality (LLI) or discrepancy (LLD). This asymmetry can induce pelvic misalignments, manifested by an asymmetric height of the iliac crests, and consequently an alteration of the spine's axis. Although correcting this discrepancy might appear to be a straightforward solution, further investigation may reveal other indications. The purpose of this article is to aid clinicians confronted with the decision of whether to compensate for an LLI in individuals with scoliosis, encompassing both adolescents and adults. It presents a literature review on the incidence of LLIs in the general population, distinguishing between structural LLI (sLLI) and functional LLI (fLLI) types of LLIs, and quantifying their magnitude with clinical and instrumental evaluation. Additionally, it links these two types of LLIs to the type of scoliosis (structural or functional). From a clinical perspective, it also examines the compensatory mechanisms employed by the pelvis in the presence of structural or functional LLIs in order to draw useful indications for therapeutic decisions. Moreover, it proposes an additional evaluation parameter in the coronal plane, namely the central sacral vertical line (CSVL), to aid in the decision-making process regarding LLI compensation. Although this parameter has been documented in the literature, it has been little associated with LLIs. The findings indicate that scoliotic discrepancies should be compensated (conservatively or surgically) only when the imbalance of the femoral heads is on the same side as the imbalance of the sacrum and the iliac crests; this corrective action should result in a reduction of the overhang in the coronal plane.

Frontoparietal function and underlying structure reflect capacity for motor skill acquisition during healthy aging

While capacity for motor skill acquisition changes with healthy aging, there has been little consideration of how age-related changes in brain function or baseline brain structure support motor skill acquisition. We examined: (1) age-dependent changes in functional reorganization related to frontoparietal regions during motor skill acquisition, and (2) whether capacity for motor skill acquisition relates to baseline white matter microstructure in frontoparietal tracts. Healthy older and younger adults engaged in 4 weeks of skilled motor practice. Resting-state functional connectivity (rsFC) assessed functional reorganization before and after practice. Diffusion tensor imaging indexed microstructure of a frontoparietal tract at baseline, generated by rsFC seeds. Motor skill acquisition was associated with decreases in rsFC in healthy older adults and increases in rsFC in healthy younger adults. Frontoparietal tract microstructure was lower in healthy older versus younger adults, yet it was negatively associated with rate of skill acquisition regardless of group. Findings indicate that age-dependent alterations in frontoparietal function and baseline structure of a frontoparietal tract reflect capacity for motor skill acquisition.

Learning vs. minding: How subjective costs can mask motor learning

When learning new movements some people make larger kinematic errors than others, interpreted as a reduction in motor-learning ability. Consider a learning task where error-cancelling strategies incur higher effort costs, specifically where subjects reach to targets in a force field. Concluding that those with greater error have learned less has a critical assumption: everyone uses the same error-canceling strategy. Alternatively, it could be that those with greater error may be choosing to sacrifice error reduction in favor of a lower effort movement. Here, we test this hypothesis in a dataset that includes both younger and older adults, where older adults exhibited greater kinematic errors. Utilizing the framework of optimal control theory, we infer subjective costs (i.e., strategies) and internal model accuracy (i.e., proportion of the novel dynamics learned) by fitting a model to each population's trajectory data. Our results demonstrate trajectories are defined by a combination of the amount learned and strategic differences represented by relative cost weights. Based on the model fits, younger adults could have learned between 65-90% of the novel dynamics. Critically, older adults could have learned between 60-85%. Each model fit produces trajectories that match the experimentally observed data, where a lower proportion learned in the model is compensated for by increasing costs on kinematic errors relative to effort. This suggests older and younger adults could be learning to the same extent, but older adults have a higher relative cost on effort compared to younger adults. These results call into question the proposition that older adults learn less than younger adults and provide a potential explanation for the equivocal findings in the literature. Importantly, our findings suggest that the metrics commonly used to probe motor learning paint an incomplete picture, and that to accurately quantify the learning process the subjective costs of movements should be considered.

Differences in Health-Related Physical Fitness and Academic School Performance in Male Middle-School Students in Qatar: A Preliminary Study

This study examined the differences in the level of physical fitness and academic performance among male middle-school children based on different body status categories. A total of 69 male children [age: 12.4 ± 0.7 years; body mass: 58.5 ± 7.2 kg; height: 1.62 ± 0.09 m; and body mass index (BMI): 22.4 ± 3.3 kg/m²] participated and were divided into BMI age-adjusted groups (i.e., lowest, middle, and highest BMI). Height, mass, BMI, stork test of static balance, 10 and 15 m sprint as an indicator for speed, hand-grip strength test, agility T-half test, medicine ball throw (MBT), and the Yo-Yo Intermittent Recovery Test level 1 (Yo-Yo IR1) were assessed. School records were retrieved for grade point averages (GPA) of mathematics, science, and Arabic. We found significant group differences regarding anthropometric (height: ηp2 = 0.24, mass: ηp2 = 0.33, and BMI: ηp2 = 0.66), physical (sprint 10 m: ηp2 = 0.26), and academic (mathematics: ηp2 = 0.19 and science: ηp2 = 0.15) performance parameters. The largest difference (p < 0.001) was observed between the lowest and highest group for the 10 m sprint. All pairwise differences were between the lowest and highest BMI group or the lowest and middle BMI group. No relevant (r > 0.5) correlation between parameters of different dimensions (e.g., anthropometric vs. physical performance parameters) was found. In conclusion, the highest BMI group exhibited similar physical and academic performances than the lowest group. Thus, these data emphasize the importance and appropriateness to engage young Qatari schoolchildren in physical activity as it associates with superior academic performance.

Bayesian Estimation of Potential Performance Improvement Elicited by Robot-Guided Training

Improving human motor performance via physical guidance by an assist robot device is a major field of interest of the society in many different contexts, such as rehabilitation and sports training. In this study, we propose a Bayesian estimation method to predict whether motor performance of a user can be improved or not by the robot guidance from the user's initial skill level. We designed a robot-guided motor training procedure in which subjects were asked to generate a desired circular hand movement. We then evaluated the tracking error between the desired and actual subject's hand movement. Results showed that we were able to predict whether a novel user can reduce the tracking error after the robot-guided training from the user's initial movement performance by checking whether the initial error was larger than a certain threshold, where the threshold was derived by using the proposed Bayesian estimation method. Our proposed approach can potentially help users to decide if they should try a robot-guided training or not without conducting the time-consuming robot-guided movement training.

Aerobic exercise and aerobic fitness level do not modify motor learning

Motor learning may be enhanced when a single session of aerobic exercise is performed immediately before or after motor skill practice. Most research to date has focused on aerobically trained (AT) individuals, but it is unknown if aerobically untrained (AU) individuals would equally benefit. We aimed to: (a) replicate previous studies and determine the effect of rest (REST) versus exercise (EXE) on motor skill retention, and (b) explore the effect of aerobic fitness level (AU, AT), assessed by peak oxygen uptake (VO2peak), on motor skill retention after exercise. Forty-four participants (20-29 years) practiced a visuomotor tracking task (acquisition), immediately followed by 25-min of high-intensity cycling or rest. Twenty-four hours after acquisition, participants completed a motor skill retention test. REST and EXE groups significantly improved motor skill performance during acquisition [F(3.17, 133.22) = 269.13, P = 0.001], but had no group differences in motor skill retention across time. AU-exercise (VO2peak = 31.6 ± 4.2 ml kg-1 min-1) and AT-exercise (VO2peak = 51.5 ± 7.6 ml kg-1 min-1) groups significantly improved motor skill performance during acquisition [F(3.07, 61.44) = 155.95, P = 0.001], but had no group differences in motor skill retention across time. Therefore, exercise or aerobic fitness level did not modify motor skill retention.

Cognitive Function Improvements Mediate Exercise Intervention Effects on Physical Performance in Acutely Hospitalized Older Adults

OBJECTIVES

An individualized, multicomponent exercise program is effective to reverse the functional and cognitive decline that frequently occur during acute care hospitalization in older patients. The aim was to determine whether improvements in cognition mediate improvements in physical function in acutely hospitalized older patients.

DESIGN

A single-center, single-blind randomized clinical trial.

SETTING AND PARTICIPANTS

Acute care for elderly (ACE) unit in a tertiary public hospital in Navarre (Spain). Hospitalized patients were randomly assigned to an exercise intervention (n = 185) or usual-care group (n = 185). The intervention consisted of a multicomponent exercise-training program performed during 5 to 7 consecutive days (2 sessions/day). The usual-care group received habitual hospital care, which included physical rehabilitation when needed.

MEASURES

The main endpoints were changes in cognitive function assessed by the Mini-Mental State Examination test and verbal fluency ability, and changes in physical performance by the Short Physical Performance Battery from baseline to discharge. Mediation regression models were generated using ordinary least squares with the PROCESS version 3.2 to determine links between exercise-induced improvements.

RESULTS

Mediation regression model analysis indicated a significant and direct beneficial effect of physical exercise on physical function (β = 2.14; P < .0001), and a significant indirect effect of global cognitive function on the direct effect (indirect effect = 0.26; 0.10 to 0.49). Verbal fluency ability also had an indirect effect (0.32; 0.16 to 0.53) on the positive effect of exercise-training on physical function.

CONCLUSIONS AND IMPLICATIONS

Cognitive function enhancements mediate physical function improvements in acutely hospitalized older adults after an individualized, multicomponent exercise-training program. ClinicalTrials.gov registration (NCT02300896).

Explaining Individual Differences in Fine Motor Performance and Learning in Older Adults: The Contribution of Muscle Strength and Cardiovascular Fitness

It remains controversial whether aging influences motor learning and whether physiological factors, such as local strength or fitness, are associated with fine motor performance and learning in older adults (OA). OA (n = 51) and young adults (YA, n = 31) performed a short-term motor learning session using a precision grip force modulation task. The rate of improvement of OA compared with YA was steeper with respect to performance variability and temporal precision. Both age groups showed positive transfer during an unpracticed variant of the force modulation task. Local muscle strength (pinch and grip strength) and high cardiovascular fitness positively predicted fine motor performance, whereas initial performance, muscle strength, and motor fitness (heterogeneous motor test battery) negatively predicted rate of improvement. Analyses indicated potentials, but also limits of plasticity for OA.

How does ageing affect grasp adaptation to a visual-haptic size conflict?

Previous research suggests that the ability to adapt motor behaviour to sudden environmental changes may be impaired in older adults. Here, we investigated whether the adaptation of grasping behaviour in response to a visual-haptic size conflict is also affected by increasing age. 30 older and 18 young adults were instructed to grasp a hidden block whilst viewing a second block in a congruent position. Initially block sizes were equal, but after a set number of trials a sensory conflict was introduced by covertly changing the hidden block for a smaller or larger block. The scale and speed of maximum grasp aperture adaptation to the increase or decrease in the size of the hidden block was measured. Older adults successfully adapted to the visual-haptic size conflict in a similar manner to young adults, despite a tendency to adapt less when the hidden block increased in size. This finding is attributed to the physical capabilities of the grasping hand of older adults, rather than an effect of age-related sensory or cognitive decline. The speed of grasp adaptation did not differ between age groups; however, awareness of the visual-haptic conflict lead to faster adaptation. These findings suggest that sensorimotor adaptation for grasping is intact for cognitively healthy older adults.

Exercise-Induced Neuroplasticity: A Mechanistic Model and Prospects for Promoting Plasticity

Aerobic exercise improves cognitive and motor function by inducing neural changes detected using molecular, cellular, and systems level neuroscience techniques. This review unifies the knowledge gained across various neuroscience techniques to provide a comprehensive profile of the neural mechanisms that mediate exercise-induced neuroplasticity. Using a model of exercise-induced neuroplasticity, this review emphasizes the sequence of neural events that accompany exercise, and ultimately promote changes in human performance. This is achieved by differentiating between neuroplasticity induced by acute versus chronic aerobic exercise. Furthermore, this review emphasizes experimental considerations that influence the opportunity to observe exercise-induced neuroplasticity in humans. These include modifiable factors associated with the exercise intervention and nonmodifiable factors such as biological sex, ovarian hormones, genetic variations, and fitness level. To maximize the beneficial effects of exercise in health, disease, and following injury, future research should continue to explore the mechanisms that mediate exercise-induced neuroplasticity. This review identifies some fundamental gaps in knowledge that may serve to guide future research in this area.

Does physical activity benefit motor performance and learning of upper extremity tasks in older adults? - A systematic review

Upper extremity motor performance declines with increasing age. However, older adults need to maintain, learn new and relearn known motor tasks. Research with young adults indicated that regular and acute physical activity might facilitate motor performance and motor learning processes. Therefore, this review aimed to examine the association between chronic physical activity and acute bouts of exercise on motor performance and motor learning in upper extremity motor tasks in older adults. Literature was searched via Cochrane library, PubMED, PsycINFO and Scopus and 27 studies met all inclusion criteria. All studies dealt with the influence of chronic physical activity on motor performance or motor learning, no appropriate study examining the influence of an acute bout of exercise in older adults was found. Results concerning the association of chronic physical activity and motor performance are mixed and seem to be influenced by the study design, kind of exercise, motor task, and exercise intensity. Regarding motor learning, a high physical activity or cardiovascular fitness level seems to boost the initial phase of motor learning; results differ with respect to motor retention. Overall, (motor-coordinative) intervention studies seem to be more promising than cross-sectional studies.

Role of Age in Relation between Two Kinds of Abilities and Performance in Acquisition of New Motor Skill

Better understanding of age-related differences in skilled performance was the focus of analyses of cognitive-performance scores-relationships in acquisition of a new motor skill. 31 younger adults and 33 older adults were tested on both a cognitive and a psychomotor test. Then, they were asked to learn a juggling task over 12 sessions of 20 min. Analysis indicated age-related differences in the rate of learning. Acquisition by the younger adult group was significantly faster than that by the older adult group. This difference was also reflected in the relationship of cognition and performance for the two age groups. Motor execution for the older adults seemed to require more psychomotor ability, especially at the end of the learning sessions, and was dependent on cognitive control. This trend is consistent with the perspective that cognitive predictors of performance are related to age.

Task complexity and maximal isometric strength gains through motor learning

This study compared the effects of a simple versus complex contraction pattern on the acquisition, retention, and transfer of maximal isometric strength gains and reductions in force variability. A control group (N = 12) performed simple isometric contractions of the wrist flexors. An experimental group (N = 12) performed complex proprioceptive neuromuscular facilitation (PNF) contractions consisting of maximal isometric wrist extension immediately reversing force direction to wrist flexion within a single trial. Ten contractions were completed on three consecutive days with a retention and transfer test 2‐weeks later. For the retention test, the groups performed their assigned contraction pattern followed by a transfer test that consisted of the other contraction pattern for a cross‐over design. Both groups exhibited comparable increases in strength (20.2%, P < 0.01) and reductions in mean torque variability (26.2%, P < 0.01), which were retained and transferred. There was a decrease in the coactivation ratio (antagonist/agonist muscle activity) for both groups, which was retained and transferred (35.2%, P < 0.01). The experimental group exhibited a linear decrease in variability of the torque‐ and sEMG‐time curves, indicating transfer to the simple contraction pattern (P < 0.01). The control group underwent a decrease in variability of the torque‐ and sEMG‐time curves from the first day of training to retention, but participants returned to baseline levels during the transfer condition (P < 0.01). However, the difference between torque RMS error versus the variability in torque‐ and sEMG‐time curves suggests the demands of the complex task were transferred, but could not be achieved in a reproducible way.

This study examines the effect of task complexity on the acquisition, retention, and transfer of increases in maximal strength and decreases in force variability, which is novel. Simple agonist‐only contractions are compared to a more complex reversal contraction pattern as used during proprioceptive neuromuscular facilitation (PNF). The goal was to determine if the more complex contraction pattern interferes with the strength gains and reduced variability by impeding the development of agonist‐antagonist coordination.

Improving finger coordination in young and elderly persons

We studied the effects of a single practice session of a variable task with subject-specific adjustments of task difficulty (instability) on indices of multi-finger coordination in young and elderly persons. The main hypothesis was that practicing such a task would lead to contrasting changes in the amounts of two components of variance estimated across repetitive trials within the uncontrolled manifold (UCM) hypothesis: V UCM that had no effect on total force and V ORT that affected total force. In addition, we also expected to see strong transfer effects to a different task. A variable task with graded instability was designed to encourage use of variable solutions during the accurate production of total force with two fingers. The subjects practiced with the index and middle fingers pressing on individual force sensors. Overall, the older subjects showed lower indices of performance and higher indices of both V UCM and V ORT. After about 1 h of practice, both groups showed an increase in the index of involuntary force production by non-task fingers (enslaving). Both groups improved the indices of performance. The two variance indices showed opposite effects of practice: V ORT dropped with practice, while V UCM increased leading to an increase in the total amount of variance in the space of commands to fingers and in the index of force-stabilizing synergy. Performance in a simpler, non-practiced task improved, but there was no transfer of the changes in the structure of variance. Specifically, both variance components, V ORT and V UCM, dropped in the non-practiced task. The results show that the neural system responsible for synergies stabilizing important features of performance is highly adaptable to practice of tasks designed to encourage use of variable solutions. We view the results as highly promising for future use in populations with impaired coordination characterized by low synergy indices.

Slower adaptation to driving simulator and simulator sickness in older adults

BACKGROUND AND AIMS

Methods of assessing driving abilities in the elderly are urgently needed. Although the driving simulator (DS) appears to be a safe and cost-effective method of objectively evaluating driving performance, it may pose adaptation problems for elderly adults. In this study, we examined age-related adaptation deficits on the DS.

METHODS

Healthy young adults (n=15) and healthy elderly persons (n=17) completed some neuropsychological tests, and then performed a road-tracking task with the DS, which was repeated four times (Trials 1-4).

RESULTS

After simulated driving in DS, simulator sickness (SS) was observed in 18.8% of participants. The frequency of SS was 29.4% in elderly adults and 6.7% in young adults, and 17.6% of the elderly participants dropped out of the experiment. Performance on the Necker cube copying task was significantly correlated with the onset of SS. Driving performance also showed a significant interaction between group and trial, for both driving accuracy and vehicle speed. In addition, the performance of elderly adults significantly improved between trials 1 and 4, reaching a plateau in trial 4, whereas that of young adults did not change across trials.

CONCLUSION

This study provides preliminary evidence of slower adaptation to a DS-based driving task by older adults, which was associated with cognitive aging. Age affected driving accuracy and velocity when a road-tracking task was simply repeated. It is concluded that the capacity of elderly people to adapt to DS environments should be taken into consideration when evaluating their performance on DS tasks.

Parental perspectives on leg length discrepancy

This study investigated perspectives of 58 parents on leg length discrepancy (LLD) of their children using a questionnaire survey. There were significant differences in the pain/comfort (P=0.021) and global function subscales (P=0.013) of the pediatric outcomes data collection instrument between the idiopathic LLD and posttraumatic LLD groups. Significant differences in the items with regard to the satisfaction with appearance (P=0.012), preference for surgical treatment (P<0.001), effect on happiness (P=0.004), and concerns over possible operations (P=0.010) were observed between the LLD of 2 cm or more and LLD of less than 2 cm groups. Logistic regression showed that the only significant contributing factor to a willingness to seek treatment was the amount of LLD (P=0.004).

Age effects on rotational hand action

We investigated age-related differences in finger coordination during rotational hand actions. Two hypotheses based on earlier studies were tested: higher safety margins and lower synergy indices were expected in the elderly. Young and elderly subjects held a handle instrumented with five six-component force sensors and performed discrete accurate pronation and supination movements. The weight of the system was counterbalanced with another load. Indices of synergies stabilizing salient performance variables, such as total normal force, total tangential force, moments produced by these forces, and total moment of force were computed at two levels of a hypothetical control hierarchy, at the virtual finger-thumb level and at the individual finger level. At each level, synergy indices reflected the normalized difference between the sum of the variances of elemental variables and variance of their combined output, both computed at comparable phases over repetitive trials. The elderly group performed the task slower and showed lower safety margins for the thumb during the rotation phase. Overall, the synergy indices were not lower in the elderly group. In several cases, these indices were significantly higher in the elderly than in the younger participants. Hence, both main hypotheses have been falsified. We interpret the unexpectedly low safety margins in the elderly as resulting from several factors such as increased force variability, impaired feed-forward control, and the fact that there was no danger of dropping the object. Our results suggest that in some natural tasks, such as the one used in this study, healthy elderly persons show no impairment, as compared to younger persons, in their ability to organize digits into synergies stabilizing salient performance variables.

Effect of simulated leg length discrepancy on plantar pressure distribution in diabetic patients with neuropathic foot ulceration

OBJECTIVE

To study the effect of a minor degree of artificially induced leg length discrepancy (LLD) on plantar pressure distribution in diabetic patients with neuropathic foot ulceration.

METHOD

In-shoe plantar pressure distributions were measured on the ulcerated foot during walking using F-scan (Tekscan Inc.). To simulate minor LLD, the contralateral leg length was changed by asking patients to walk under three different conditions: wearing shoe of the same sole thickness (NLLD), walking with a bare foot (20mm long leg) and wearing a 40mm-high platform-sole shoe (20mm short leg). These three different walking conditions were compared in a randomised, single-blinded crossover design.

RESULTS

The study included 28 diabetic patients with neuropathic foot ulcers (53.7 ± 6.8 years; 16 males, 12 female). Notably, the peak pressure and pressure time integral (PTI) were the most affected parameters. PTI significantly increased beneath total foot, mid-foot, 2nd, 3rd, 4th and 5th metatarsal heads (MTHs), and 3rd toe, when the 20mm short leg was simulated (79.4 ± 21.1; 61.5 ± 32.3; 59.9 ± 36.5; 69 ± 42.1; 70.6 ± 42.3; 63.9 ± 33.7; 40.± 33.2 kPa·s, respectively), compared with NLLD (73.7 ± 19.9; 55.524; 51.8 ± 30.1; 58.4 ± 37.6; 60.3 ± 39.5; 57.2 ± 32.3; 36.9 ± 33.3 kPa·s, respectively).

CONCLUSION

The short leg of diabetic patients with neuropathic foot ulcers will be subjected to greater pressure load, primarily beneath the total foot, mid-foot and 2nd, 3rd, 4th and 5th metatarsal heads. As such, care should be taken to avoid minor LLD, as it could inadvertently develop on using offloading devices.

DECLARATION OF INTEREST

The authors have nothing to declare.

The motor-learning process of older adults in eccentric bicycle ergometer training

This study describes the motor-learning process of older individuals during the course of a training intervention on a motor-driven eccentric bicycle ergometer. Seventeen women and 16 men (64 ± 6 yr) took part in a 10-wk training program. Uniformity of force production and consistency of timing were used to describe their motor performance. The results suggested that participants improved the coefficient of variation of peak force during the intervention (measured at the 2nd, 4th, 6th, 8th, 10th, 12th, and the 18th training sessions). They reached a fairly constant level of motor performance around the 12th training session (5 wk). Age and sex affected improvements in the early phases of the learning process to an extent, but the differences diminished by the end of the intervention. These results suggest that the force control of continuous eccentric muscle contractions improves as a result of training in older adults.

The effect of haptic guidance, aging, and initial skill level on motor learning of a steering task

In a previous study, we found that haptic guidance from a robotic steering wheel can improve short-term learning of steering of a simulated vehicle, in contrast to several studies of other tasks that had found that the guidance either impairs or does not aid motor learning. In this study, we examined whether haptic guidance-as-needed can improve long-term retention (across 1 week) of the steering task, with age and initial skill level as independent variables. Training with guidance-as-needed allowed all participants to learn to steer without experiencing large errors. For young participants (age 18–30), training with guidance-as-needed produced better long-term retention of driving skill than did training without guidance. For older participants (age 65–92), training with guidance-as-needed improved long-term retention in tracking error, but not significantly. However, for a subset of less skilled, older subjects, training with guidance-as-needed significantly improved long-term retention. The benefits of guidance-based training were most evident as an improved ability to straighten the vehicle direction when coming out of turns. In general, older participants not only systematically performed worse at the task than younger subjects (errors ∼3 times greater), but also apparently learned more slowly, forgetting a greater percentage of the learned task during the 1 week layoffs between the experimental sessions. This study demonstrates that training with haptic guidance can benefit long-term retention of a driving skill for young and for some old drivers. Training with haptic guidance is more useful for people with less initial skill.

Improved sensorimotor adaptation after exhaustive exercise is accompanied by altered brain activity

Acute exercise has been shown to exhibit different effects on human sensorimotor behavior; however, the causes and mechanisms of the responses are often not clear. The primary aim of the present study was to determine the effects of incremental running until exhaustion on sensorimotor performance and adaptation in a tracking task. Subjects were randomly assigned to a running group (RG), a tracking group (TG), or a running followed by tracking group (RTG), with 10 subjects assigned to each group. Treadmill running velocity was initially set at 2.0 m s(-1), increasing by 0.5 m s(-1) every 5 min until exhaustion. Tracking consisted of 35 episodes (each 40 s) where the subjects' task was to track a visual target on a computer screen while the visual feedback was veridical (performance) or left-right reversed (adaptation). Resting electroencephalographic (EEG) activity was recorded before and after each experimental condition (running, tracking, rest). Tracking performance and the final amount of adaptation did not differ between groups. However, task adaptation was significantly faster in RTG compared to TG. In addition, increased alpha and beta power were observed following tracking in TG but not RTG although exhaustive running failed to induce significant changes in these frequency bands. Our results suggest that exhaustive running can facilitate adaptation processes in a manual tracking task. Attenuated cortical activation following tracking in the exercise condition was interpreted to indicate cortical efficiency and exercise-induced facilitation of selective central processes during actual task demands.

A meta-regression to examine the relationship between aerobic fitness and cognitive performance

Many studies have been conducted to test the potentially beneficial effects of physical activity on cognition. The results of meta-analytic reviews of this literature suggest that there is a positive association between participation in physical activity and cognitive performance. The design of past research demonstrates the tacit assumption that changes in aerobic fitness contribute to the changes in cognitive performance. Therefore, the purpose of this meta-analysis was to use meta-regression techniques to statistically test the relationship between aerobic fitness and cognitive performance. Results indicated that there was not a significant linear or curvilinear relationship between fitness effect sizes (ESs) and cognitive ESs for studies using cross-sectional designs or posttest comparisons. However, there was a significant negative relationship between aerobic fitness and cognitive performance for pre-post comparisons. The effects for the cross-sectional and pre-post comparisons were moderated by the age group of the participants; however, the nature of this effect was not consistent for the two databases. Based on the findings of this meta-analytic review, it is concluded that the empirical literature does not support the cardiovascular fitness hypothesis. To confirm the findings of this review, future research should specifically test the dose-response relationship between aerobic fitness and cognitive performance. However, based upon the findings of this review, we also encourage future research to focus on other physiological and psychological variables that may serve to mediate the relationship between physical activity and cognitive performance.

Differential effects of age on sequence learning and sensorimotor adaptation

Although many studies have documented declines in the ability of the elderly to learn new manual motor skills, studies have not directly compared the capacity of older adults to learn sequences versus adapt to sensorimotor perturbations within the context of the same task paradigm, despite differences in the underlying neural mechanisms and strategic processes supporting the two types of learning. The purpose of the current study was to exploit these task differences in an effort to determine whether aging results in a generalized or more specific skill learning deficit. Groups of young and older adult subjects learned to make a sequence of actions, adapted to one of two visuomotor rotations, or adapted to an altered gain of display, all while performing the same basic manual joystick aiming task. While the older adults exhibited normal sequence learning in comparison to the young adults, they exhibited impairments in all three of the adaptation tasks. These deficits in adaptation for the older adults were associated with hypometric movements and reduced velocity modulation in comparison to that seen in the younger adults. These data suggest that older adults may have greater difficulty with learning cerebellar-mediated motor skills.

Relationship between sensorimotor adaptation and cognitive functions in younger and older subjects

We investigated whether deficits of adaptive improvement in seniors are related to an age-dependent decay of the brain's executive functions. Younger and older subjects completed a battery of cognitive tests, and preformed aimed arm movements before and during exposure to rotated visual feedback. In accordance with previous work, we found that adaptive improvement during exposure was degraded in seniors, while the transfer of adaptation to a new motor task was not. This pattern of findings confirms that strategic control but not sensorimotor recalibration is affected by old age. Using multiple linear regression (MLR) to extract separate executive components from our test battery, we found that basic response speed and decision-making, but not the inhibition of prepotent responses or mental flexibility, were degraded in our older subjects. Again using MLR, we found that degraded adaptive improvement in our seniors was partly related to the decay of basic response speed and decision-making, and partly to age-dependent phenomena not addressed by our cognitive-test battery. Finally, we observed that interindividual variability of cognition and adaptive improvement was larger in old than in young subjects, which could explain why some previous studies found degraded adaptation in seniors while others did not.

Components of sensorimotor adaptation in young and elderly subjects

Previous studies have found that sensorimotor adaptation to visual distortions is degraded in seniors compared with younger subjects, whereas after-effects on removal of the distortion are age-independent. The latter finding was interpreted as evidence that adaptive recalibration is not affected by old age, and that the observed degradation is therefore due to impairment of strategic control. However, after-effects are not a reliable measure of recalibration, because they can be artificially inflated by perseveration, a characteristic symptom in old age. The present work therefore introduces a test of recalibration which is insensitive to perseveration. Twelve young and twelve old subjects executed center-out pointing movements while visual feedback about their fingertip was either veridical (baseline), 60-deg rotated (adaptation), or absent (after-effect). They also executed tracking movements toward an unpredictably moving object before and after the pointing task. Seniors adapted less than younger subjects but their after-effects were not degraded. More importantly, transfer of adaptation from a pointing to a tracking task was not degraded in seniors. The latter outcome documents, in a more compelling fashion than previous work, that recalibration in the elderly is not impaired, and that the observed deficit of adaptation is therefore most probably because of impaired strategic control. This conclusion is supported by two additional findings: compared with young subjects our seniors performed less well on a cognitive screening test and acquired no explicit knowledge about the nature of the imposed visual distortion.

Five clinical tests to assess balance following ball exercises and treadmill training in adult persons with intellectual disability

BACKGROUND

Incidence rates of falling increase progressively with aging. Preventing or delaying the onset of functional decline is a crucial important goal, because more individuals with intellectual disability (ID) are living well into their sixth and seventh decades. The question of whether walking and ball exercises can effect balance performance has never been reported. This pilot study was conducted to determine the effects of therapeutic training on improving balance capabilities in adults with mild ID.

METHODS

The study included 13 women and 4 men, aged 50-67 years (mean age 56.5 years) residing in a residential care center. Five clinical tests were used to determine the "real" picture of the locomotor function and balance before and after the training protocol. Baseline values were determined using 2 control groups of age-matched adults with and without ID. The tests included modified get-up-and-go, full turn, forward reach, sit-to-stand, and one-legged standing. Therapeutic training for 6 months included dynamic ball exercises and treadmill walking with a 2-3% positive inclination.

RESULTS

Participants in the program showed little to no improvement in terms of their static and dynamic balance compared to their initial values. Thus, only 2 of the tests showed statistical significance.

CONCLUSIONS

Lack of improvement was noted in both postural and balance control in adults with mild ID as a result of 6 months of intervention by means of ball exercise and treadmill training.

Visuomotor adaptation in normal aging

Visuomotor adaptation to a gradual or sudden screen cursor rotation was investigated in healthy young and elderly subjects. Both age groups were equally divided into two subgroups; one subgroup was exposed to 11.25 degrees step increments of visual feedback rotation, every 45 trials (up to a total of 90 degrees), whereas a second subgroup was subjected to 90 degrees rotation from the onset of exposure. Participants performed discrete, horizontal hand movements to virtual targets in four randomized directions. Targets appeared on a computer screen in front of them, and a board prevented vision of the hand at all times. Differential effects of aging on visuomotor adaptation were found, depending on the time course of the visual distortion. In both age groups, early exposure to the sudden visual feedback distortion resulted in typical spiral-like trajectories, which became straighter by late exposure. However, the final adaptation level was reduced in the aged group, although the aftereffects were similar. When subjects were exposed to the gradual distortion, no statistically significant differences in measures of adaptation with advancing age were found. In this case, both age groups appeared to adapt equally. However, after removal of the distortion, elderly subjects showed reduced aftereffects as compared with the young group. These findings suggest differential effects of aging on adaptation to gradual versus sudden visual feedback distortions, and may help to explain the conflicting results obtained in previous visuomotor adaptation studies.

Sensorimotor adaptation in young and elderly humans

Our brain's capacity for adaptation allows us to interact meaningfully with an ever-changing environment. Experimental evidence suggests that the time course of sensorimotor adaptation is preserved or only moderately degraded in old age, and that seniors benefit from a previous adaptive experience even more than younger subjects. However, experimental evidence suggests that sensorimotor adaptation seems to be associated with a higher computational load in the elderly. We discuss two possible explanations for this pattern of findings: Older adults may take longer to consolidate newly gained information into long-term motor memory, or they may have problems to utilize supplementary (e.g. cognitive) strategies. In any case, the age-related deficits were relatively mild. If these deficits are related to an increased computational load, it should be possible to reduce them by extended practice on adaptation tasks.

Leg length discrepancy

The role of leg length discrepancy (LLD) both as a biomechanical impediment and a predisposing factor for associated musculoskeletal disorders has been a source of controversy for some time. LLD has been implicated in affecting gait and running mechanics and economy, standing posture, postural sway, as well as increased incidence of scoliosis, low back pain, osteoarthritis of the hip and spine, aseptic loosening of hip prosthesis, and lower extremity stress fractures. Authors disagree on the extent (if any) to which LLD causes these problems, and what magnitude of LLD is necessary to generate these problems. This paper represents an overview of the classification and etiology of LLD, the controversy of several measurement and treatment protocols, and a consolidation of research addressing the role of LLD on standing posture, standing balance, gait, running, and various pathological conditions. Finally, this paper will attempt to generalize findings regarding indications of treatment for specific populations.

Effects of limb-length discrepancy on gait economy and lower-extremity muscle activity in older adults

BACKGROUND

The amount of limb-length discrepancy necessary to adversely affect gait parameters in older adults is unknown, with information being largely anecdotal. This investigation was conducted to determine the effects of limb-length discrepancy on gait economy and lower-extremity muscle activity in older adults.

METHODS

Forty-four men and women ranging in age from fifty-five to eighty-six years with no evidence of limb-length discrepancy of >1 cm participated in the study. Subjects walked on a treadmill at a self-selected normal walking pace with artificial limb-length discrepancies of 0, 2, 3, and 4 cm applied in a randomly selected order. Indirect calorimetry was used to measure oxygen consumption and minute ventilation. Electromyography was used to measure muscle activity of the right and left quadriceps femoris, plantar flexors, gluteus maximus, and gluteus medius. Heart rate, the rating of perceived exertion, and frequency of gait compensation patterns were also measured.

RESULTS

There was a significant increase in oxygen consumption and the rating of perceived exertion with 2, 3, and 4-cm artificial limb-length discrepancies; a significant increase in heart rate, minute ventilation, and quadriceps activity in the longer limb with 3 and 4-cm artificial limb-length discrepancies; and a significant increase in plantar flexor activity in the shorter limb with a 4-cm artificial limb-length discrepancy compared with the same parameters with no artificial limb-length discrepancy.

CONCLUSIONS

Both oxygen consumption and the rating of perceived exertion were greater with a 2-cm artificial limb-length discrepancy than they were with no artificial limb-length discrepancy. There appears to be a breakpoint between 2 and 3 cm of artificial limb-length discrepancy in older adults with regard to the effects on most other physiological parameters. A 3-cm artificial limb-length discrepancy is likely to induce significant quadriceps fatigue in the longer limb. Elderly patients with substantial pulmonary, cardiac, or neuromuscular disease may have difficulty walking with a limb-length discrepancy as small as 2 cm.

Influence of cholinergic system on motor learning during aging in mice

Three, 12- and 20-month-old C57Bl6 mice, reared in standard conditions or in an enriched environment, were administered subcutaneously either scopolamine hydrobromide (SIGMA), 0.6 and 1.2 mg kg(-1), or physiological saline 15 min before testing their motor skills (muscular strength, dynamic equilibrium and motor coordination) and motor learning abilities (number of trials needed to reach a learning criterion on a rotorod rotating at 27 revolutions per min). The results demonstrated a lack of correlation between motor skill scores and between motor skill and motor learning scores, suggesting that the rotorod training procedure measures motor learning and not motor skills or is insensitive to changes in motor skills. They also demonstrated that motor skills decreased with age but were insensitive to environmental rearing and to scopolamine. In contrast, the learning scores, which also decreased with age, were very sensitive to scopolamine, particularly in the oldest mice. These results are discussed according to the role of cholinergic system in motor learning during aging.

Prism adaptation in normal aging: slower adaptation rate and larger aftereffect

The effect of aging on prism adaptation, a motor learning paradigm, was evaluated. Different measures were obtained from a task consisting of throwing clay balls to a target in front of the subjects before, during, and after wearing prisms that deviate the visual field by several degrees. When performing the task without wearing the prisms, the aged subjects showed a larger hit variance, whereas the young subjects hit closer to the target. When donning the prisms, the aged group adapted more slowly than the controls, although after throwing all the balls both groups showed the same adaptation levels. After removing the prisms, the aged group showed a larger aftereffect. These findings suggest that the aftereffect requires the involvement of non-cognitive and cognitive processes and indicate that both adaptation and aftereffect are influenced by aging.

Bcl-2 transgenic mice with increased number of neurons have a greater learning capacity

Transgenic mice overexpressing Bcl-2 in their neurons have an increased number of neurons. To assess whether this increased number of neurons leads to increased learning capacity we have used the Hebb-Williams maze which provides a measure of learning suitable for the study of small animals. We have demonstrated that bcl-2 transgenic mice learn faster and are more accurate in this maze. They required fewer trials to complete the maze and committed fewer errors. The transgenic mice were also faster than the wildtype mice, in particular the older mice. Prior to learning both groups of mice behaved in a similar way. These results show that bcl-2 transgene expression enhances learning capacity in mice by increasing the number of neurons.