Walking-Induced Fatigue Leads to Increased Falls Risk in Older Adults

Perturbed walking balance recovery between premenopausal and postmenopausal females

BACKGROUND

Early postmenopausal females are at increased risk for falls and fragility fractures, despite often not meeting the diagnostic criteria for osteoporosis or showing noticeable declines in gait and balance.

METHODS

Fifteen premenopausal females (aged 35-53) and fifteen postmenopausal females (aged 50-66) participated in this study. The Gait Real-time Analysis Interactive Laboratory was utilized to simulate unexpected perturbations during walking. Variables comprising the number of contralateral limb steps, step length, width, height, stance time, and double support time were analysed and compared between the groups in both natural and perturbed gait using statistical parametric mapping.

FINDINGS

During the swing phase of the contralateral, unperturbed limb, most premenopausal females completed the swing phase without prematurely lowering their legs and taking additional steps with it. Conversely, most postmenopausal participants lowered their contralateral, unperturbed leg and took one or two steps with it before fully entering the swing phase and proceeding to the heel strike of the next gait cycle. Moreover, a smaller step width and shorter step height were observed during the perturbed gait cycle in the postmenopausal group compared to the premenopausal group.

INTERPRETATION

Menopausal status significantly impacted balance recovery strategies and gait spatial parameters during balance-challenging perturbed conditions. These findings highlight the importance of applying perturbations and using spatial parametric mapping in further research to better understand gait stability and its role in fall risk during early menopause.

The effect of exercise-induced muscle fatigue on gait parameters among older adults: a systematic review and meta-analysis

BACKGROUND

Exercise-induced fatigue is a common consequence of physical activities. Particularly in older adults, it can affect gait performance. Due to a wide variety in fatiguing protocols and gait parameters used in experimental settings, pooled effects are not yet clear. Furthermore, specific elements of fatiguing protocols (i.e., intensity, duration, and type of activity) might lead to different changes in gait parameters. We aimed to systematically quantify to what extent exercise-induced fatigue alters gait in community-dwelling older adults, and whether specific elements of fatiguing protocols could be identified.

METHODS

This systematic review and meta-analysis was conducted in accordance with the PRISMA guidelines. In April 2023, PubMed, Web of Science, Scopus, Cochrane and CINAHL databases were searched. Two independent researchers screened and assessed articles using ASReview, Rayyan, and ROBINS-I. The extracted data related to spatio-temporal, stability, and variability gait parameters of healthy older adults (55 +) before and after a fatiguing protocol or prolonged physical exercise. Random-effects meta-analyses were performed on both absolute and non-absolute effect sizes in RStudio. Moderator analyses were performed on six clusters of gait parameters (Dynamic Balance, Lower Limb Kinematics, Regularity, Spatio-temporal Parameters, Symmetry, Velocity).

RESULTS

We included 573 effect sizes on gait parameters from 31 studies. The included studies reflected a total population of 761 older adults (57% female), with a mean age of 71 (SD 3) years. Meta-analysis indicated that exercise-induced fatigue affected gait with a standardized mean change of 0.31 (p < .001). Further analyses showed no statistical differences between the different clusters, and within clusters, the effects were non-uniform, resulting in an (indistinguishable from) zero overall effect within all clusters. Elements of fatiguing protocols like duration, (perceived) intensity, or type of activity did not moderate effects.

DISCUSSION

Due to the (mainly) low GRADE certainty ratings as a result of the heterogeneity between studies, and possible different strategies to cope with fatigue between participants, the only conclusion that can be drawn is that older adults, therapist, and researchers should be aware of the small to moderate changes in gait parameters as a result of exercise-induced fatigue.

Effectiveness of Using a Digital Wearable Plantar Pressure Device to Detect Muscle Fatigue: Within-Subject, Repeated Measures Experimental Design

Background

Muscle fatigue, characterized by reduced force generation during repetitive contractions, impacts older adults doing daily activities and athletes during sports activities. While various sensors detect muscle fatigue via muscle activity, biochemical markers, and kinematic parameters, a real-time wearable solution with high usability remains limited. Plantar pressure monitoring detects muscle fatigue through foot loading changes, seamlessly integrating into footwear to improve the usability and compliance for home-based monitoring.

Objective

This study aimed to investigate the effects of muscle fatigue on plantar pressure measurements using a self-developed wearable plantar pressure system.

Methods

Twelve healthy participants completed a 5-minute calf muscle fatigue protocol. The plantar pressures and surface electromyography (sEMG) activity of the gastrocnemius muscles were recorded before and after exercise. The plantar pressures at 6 regions and the median frequency (MDF) of sEMG were analyzed to quantify fatigue.

Results

The self-developed foot pressure system showed a significant decrease in plantar pressure peak values at the heel of the left (P=.003) and right feet (P=.001) and at the lateral toe of the left (P=.001) and right feet (P=.026). A significant increase was observed at the metatarsal head of both the left foot (P=.001) and the right foot (P=.017). The MDF of sEMG signals significantly decreased in the left (P=.001) and right gastrocnemius (P<.001).

Conclusions

Plantar pressure changes and sEMG signals effectively detect gastrocnemius muscle fatigue using the proposed wearable system, supporting the development of a wearable solution for detecting muscle fatigue suitable for home-use.

Changes in lower extremity muscle coordination over a 30-minute walk do not differ by muscle fatigability

Muscle fatigue, the transient decrease in muscle power, leads to low levels of physical activity and an inability to perform activities of daily living. Altered muscle coordination in response to fatigue may contribute to impaired physical performance. We sought to determine whether lower extremity muscle coordination during gait changes differently depending on susceptibility to fatigue (i.e., fatigability). Thirty-one older adults completed muscle power testing before and after a 30-min walk, with the change in power used to categorize participants as more or less fatigable. We used non-negative matrix factorization to identify muscle modules from electromyography (EMG) from the 2nd minute as our measure of baseline muscle coordination. Changes in muscle coordination were determined by computing the variance in the 30th minute's EMG accounted for by the baseline modules across all muscles (tVAF) and in individual muscles (mVAF). We compared tVAF between the 2nd and 30th minutes of the walk in individuals who were more and less fatigable. We used mVAF to explore the contribution of changes in individual muscle activity to tVAF. There was a decrease in tVAF overall in response to the walk (p < 0.001; 92.3 ± 1.6 % vs. 89.0 ± 4.3 %) but this did not differ between groups (interaction p = 0.66). There were significant associations between mVAF and tVAF for knee extensor, knee flexor, and ankle dorsiflexor muscles. Our results suggest that muscle coordination changes over the course of a walk in older adults but that this change does not differ between more and less fatigable older adults.

Fatiguing exercise reduces cellular passive Young's modulus in human vastus lateralis muscle

Previous studies demonstrated that acute fatiguing exercise transiently reduces whole-muscle stiffness, which might contribute to increased risk of injury and impaired contractile performance. We sought to elucidate potential intracellular mechanisms underlying these reductions. To that end, the cellular passive Young's modulus was measured in muscle fibres from healthy, young males and females. Eight volunteers (four male and four female) completed unilateral, repeated maximal voluntary knee extensions until task failure, immediately followed by bilateral percutaneous needle muscle biopsy of the post-fatigued followed by the non-fatigued control vastus lateralis. Muscle samples were processed for mechanical assessment and separately for imaging and phosphoproteomics. Fibres were passively (pCa 8.0) stretched incrementally to 156% of initial sarcomere length to assess Young's modulus, calculated as the slope of the resulting stress-strain curve at short (sarcomere length = 2.4-3.0 µm) and long (sarcomere length = 3.2-3.8 µm) lengths. Titin phosphorylation was assessed by liquid chromatography followed by high-resolution mass spectrometry. The passive modulus was significantly reduced in post-fatigued versus control fibres from male, but not female, participants. Post-fatigued samples showed altered phosphorylation of five serine residues (four located within the elastic region of titin) but did not exhibit altered active tension or sarcomere ultrastructure. Collectively, these results suggest that acute fatigue is sufficient to alter phosphorylation of skeletal titin in multiple locations. We also found reductions in the passive modulus, consistent with prior reports in the literature investigating striated muscle stiffness. These results provide mechanistic insight contributing to the understanding of dynamic regulation of whole-muscle tissue mechanics in vivo. HIGHLIGHTS: What is the central question of this study? Previous studies have shown that skeletal muscle stiffness is reduced following a single bout of fatiguing exercise in whole muscle, but it is not known whether these changes manifest at the cellular level, and their potential mechanisms remain unexplored. What is the main finding and its importance? Fatiguing exercise reduces cellular stiffness in skeletal muscle from males but not females, suggesting that fatigue alters tissue compliance in a sex-dependent manner. The phosphorylation status of titin, a potential mediator of skeletal muscle cellular stiffness, is modified by fatiguing exercise. Previous studies have shown that passive skeletal muscle stiffness is reduced following a single bout of fatiguing exercise. Lower muscle passive stiffness following fatiguing exercise might increase risk for soft-tissue injury; however, the underlying mechanisms of this change are unclear. Our findings show that fatiguing exercise reduces the passive Young's modulus in skeletal muscle cells from males but not females, suggesting that intracellular proteins contribute to reduced muscle stiffness following repeated loading to task failure in a sex-dependent manner. The phosphorylation status of the intracellular protein titin is modified by fatiguing exercise in a way that might contribute to altered muscle stiffness after fatiguing exercise. These results provide important mechanistic insight that might help to explain why biological sex impacts the risk for soft-tissue injury with repeated or high-intensity mechanical loading in athletes and the risk of falls in older adults.

Assessing acute effects of two motor-cognitive training modalities on cognitive functions, postural control, and gait stability in older adults: a randomized crossover study

Background

The process of aging often accompanies a decline in cognitive function, postural control, and gait stability, consequently increasing the susceptibility to falls among older individuals. In response to these challenges, motor-cognitive training has emerged as a potential intervention to mitigate age-related declines.

Objective

This study aims to assess the acute effects of two distinct motor-cognitive training modalities, treadmill dual-task training (TMDT) and interactive motor-cognitive training (IMCT), on cognitive function, postural control, walking ability, and dual-task performance in the elderly population.

Method

In this randomized crossover study, 35 healthy elderly individuals (aged 60-75) participated in three acute training sessions involving TMDT, IMCT, and a control reading condition. Assessments of executive function, postural control, gait performance, and cognitive accuracy were conducted both before and after each session.

Results

Both TMDT and IMCT improved executive functions. Notably, IMCT resulted in a significant enhancement in correct response rates and a reduction in reaction times in the Stroop task (p < 0.05) compared to TMDT and the control condition. IMCT also led to an increase in dual-task gait speed (p < 0.001) and showed a trend towards improved cognitive accuracy (p = 0.07). Conversely, TMDT increased postural sway with eyes open (p = 0.013), indicating a potential detriment to postural control.

Conclusion

The findings suggest that IMCT holds greater immediate efficacy in enhancing cognitive function and gait stability among older adults compared to TMDT, with a lesser adverse impact on postural control. This underscores the potential of IMCT as a preferred approach for mitigating fall risk and enhancing both cognitive and physical functions in the elderly population.

Correlation between postural stability and fall risk in trans-femoral amputees due to muscle fatigue

[Purpose] This study aimed to establish a connection between postural stability and falling in individuals with transfemoral amputation (TFA), particularly with muscle fatigue. [Participants and Methods] Fourteen participants were recruited. Muscle fatigue was induced using a sit-to-stand (STS) fatigue protocol. Pre-fatigue and post-fatigue assessments were conducted using the Biodex Balance System (BBS). [Result] The findings of the study revealed significant increases in the postural stability index between the pre-fatigue and post-fatigue conditions for the TFA group, particularly in the overall stability index (OSI) and anterior-posterior stability index (APSI) components. The mean postural stability index scores for the TFA group exhibited a percentage increase of 65.2% for OSI, 52.7% for APSI, and 50% for medial-lateral stability index (MLSI). Furthermore, the TFA fall risk index surged by 61.4%. Regarding the relationships observed, a significant correlation emerged between fall risk and both OSI and APSI. [Conclusion] These findings underscore the impact of muscle fatigue on postural stability and an increase in fall risk among TFA. By mitigating the effects of muscle fatigue, therapists can play an important role in reducing the risk of falls and promoting better postural stability in this population.

Hamstrings-quadriceps strength ratio could be related to falls in community-living older adults

A prior study reported that the concentric strength imbalance between hamstrings and quadriceps is associated with falls in older adults. Given that the concentric strength may not be measured as conveniently as the isometric strength, it is meaningful to test whether the isometric hamstring-quadricep strength imbalance is related to falls among older adults. This study sought to explore whether the hamstrings-quadriceps ratio could differentiate fallers from non-fallers in community-dwelling older adults. One hundred and eleven older adults were included in this cross-sectional study. Their isometric knee joint strength capacity (extensors and flexors) was measured. Based on their fall history in the past year, they were classified as fallers (at least one fall) or non-fallers (no fall). The hamstrings-quadriceps ratio was compared between the faller and non-faller groups. The receiver operating characteristic analysis was used to determine the cutoff value of the hamstrings-quadriceps ratio able to best classify fallers and non-fallers. Fallers showed a significantly lower hamstrings-quadriceps ratio than non-fallers (p = 0.008). The receiver operating characteristic analysis identified 0.733 as the best ratio to differentiate fallers from non-fallers with an accuracy of 64.0 %. A 0.1-unit reduction in the hamstrings-quadriceps ratio increases the probability of falling by a factor of 1.30. The hamstrings-quadriceps ratio could be used as an additional fall risk factor when assessing the risk of falls among older adults. A smaller than 0.733 hamstring-quadriceps ratio may indicate a high risk of falls.

Analyzing population-level trials as N-of-1 trials: An application to gait

Studying individual causal effects of health interventions is important whenever intervention effects are heterogeneous between study participants. Conducting N-of-1 trials, which are single-person randomized controlled trials, is the gold standard for their analysis. As an alternative method, we propose to re-analyze existing population-level studies as N-of-1 trials, and use gait as a use case for illustration. Gait data were collected from 16 young and healthy participants under fatigued and non-fatigued, as well as under single-task (only walking) and dual-task (walking while performing a cognitive task) conditions. As a reference to the N-of-1 trials approach, we first computed standard population-level ANOVA models to evaluate differences in gait parameters (stride length and stride time) across conditions. Then, we estimated the effect of the interventions on gait parameters on the individual level through Bayesian repeated-measures models, viewing each participant as their own trial, and compared the results. The results illustrated that while few overall population-level effects were visible, individual-level analyses revealed differences between participants. Baseline values of the gait parameters varied largely among all participants, and the effects of fatigue and cognitive task were also heterogeneous, with some individuals showing effects in opposite directions. These differences between population-level and individual-level analyses were more pronounced for the fatigue intervention compared to the cognitive task intervention. Following our empirical analysis, we discuss re-analyzing population studies through the lens of N-of-1 trials more generally and highlight important considerations and requirements. Our work encourages future studies to investigate individual effects using population-level data.

Risk Factors Associated with Falls in Hospitalized Older Adults Patients

Background: Given the complexity of existing assessment methods and the scarcity of specialized geriatric healthcare professionals in China, this study aimed to investigate the risk factors for falls in hospitalized older adults patients. Methods: From July 2018 to July 2020, 112 older adults patients hospitalized in the Department of Geriatrics of our hospital were enrolled and grouped into the low-(n = 12), medium-(n = 58), and high-(n = 42) (fall) risk groups according to the Johns Hopkins Fall Risk Assessment. The patient's clinical characteristics, smoking, alcohol consumption, disease, falling history, osteoporosis medication, mobility, Barthel index, MMSE, and JHFRAT score were compared between groups. Results: The high-risk group had the oldest age, and the lowest weight, BMI, as well as highest rate of stroke history and sarcopenia among the three groups. Multivariate linear regression analysis revealed that stroke history (B = 2.66, 95% CI = [0.43, 4.89]; p = .020) and gait speed (B = -4.78, 95% CI = [-8.74, -0.76]; p = .020) were the significant factors associated with fall risk in hospitalized older adults patients. Conclusions: The results suggested that hospitalized older adults patients with stroke history and low gait speed had higher fall risk. These findings may be helpful for fall prevention in hospitalized older adults patients.

The effect of prolonged walking on leg muscle activity patterns and vulnerability to perturbations

Understanding the consequences and ecological relevance of muscle fatigue is important to guide the development of strategies to preserve independence. However, few studies have examined walking-related fatigue and the effects on walking instability. Our purpose was to investigate the effects of prolonged walking on leg muscle activity and vulnerability to balance perturbations. Eighteen healthy young adults completed a 30-min walking trial at their preferred walking speed while leg muscle activities were recorded. Before and after the 30-min walk, participants responded to five 5% body weight lateral force perturbations. Time-frequency analysis with wavelet transformation and principal component analyses assessed neuromuscular adaptations of muscles to prolonged walking. Following prolonged walking, we observed a time-dependent increase in EMG intensities at slower frequencies for the soleus and tibialis anterior and a decrease in mean amplitudes for the soleus, lateral gastrocnemius, and semitendinosus. Mean mediolateral CoM displacement following perturbations averaged 21% larger after the 30-min walk. Our results suggest that walking for 30 min at a comfortable speed elicits complex neuromuscular adaptations indicative of local muscle fatigue and an increased vulnerability to walking balance perturbations. These findings could inform fatigue monitoring systems or walking assistive devices aimed at reducing walking-related fatigue and maintaining independent mobility.

Acute short term effects of endurance and resistance training on balance control in patients with diabetic peripheral neuropathy

PURPOSE

Exercise training have numerous beneficial effects on the complications of diabetic peripheral neuropathy. Exercise training may cause immediate effects on balance control in DPN patients. This study aims to assess the Acute Short Term effects of endurance and resistance exercise training on balance control in DPN patients.

METHODS

In this study, 11 patients with DPN and 11 healthy subjects participated. Patients and healthy subjects did endurance and resistance training in two separate exercise sessions. Dynamic balance and functional balance test were assessed before and after the interventions. Independent t-test was used to compare balance indices before and after training, the intervention effects were examined using ANOVA repeated measure test. The statistical significance level was set at p < 0.05.

RESULTS

The results showed that dynamic and functional balance in DPN patients were significantly lower than in healthy subjects. Anterior-posterior stability and total stability indices and functional balance test deteriorated significantly after training.

CONCLUSION

Endurance or resistance training may lead to acute disturbance of dynamic and functional balance in DPN patients. Hence, immediately after exercise, patients with diabetes are at an increased risk of falling, therefore, preventive considerations are necessary.

Neighborhood Socioeconomic Status, Green Space, and Walkability and Risk for Falls Among Postmenopausal Women: The Women's Health Initiative

PURPOSE

This study estimated associations between neighborhood socioeconomic status (NSES), walkability, green space, and incident falls among postmenopausal women and evaluated modifiers of these associations, including study arm, race and ethnicity, baseline household income, baseline walking, age at enrollment, baseline low physical functioning, baseline fall history, climate region, and urban-rural residence.

METHODS

The Women's Health Initiative recruited a national sample of postmenopausal women (50-79 years) across 40 U.S. clinical centers and conducted yearly assessments from 1993 to 2005 (n = 161,808). Women reporting a history of hip fracture or walking limitations were excluded, yielding a final sample of 157,583 participants. Falling was reported annually. NSES (income/wealth, education, occupation), walkability (population density, diversity of land cover, nearby high-traffic roadways), and green space (exposure to vegetation) were calculated annually and categorized into tertiles (low, intermediate, high). Generalized estimating equations assessed longitudinal relationships.

RESULTS

NSES was associated with falling before adjustment (high vs. low, odds ratio, 1.01; 95% confidence interval, 1.00-1.01). Walkability was significantly associated with falls after adjustment (high vs. low, odds ratio, 0.99; 95% confidence interval, 0.98-0.99). Green space was not associated with falling before or after adjustment. Study arm, race and ethnicity, household income, age, low physical functioning, fall history, and climate region modified the relationship between NSES and falling. Race and ethnicity, age, fall history, and climate region modified relationships between walkability and green space and falling.

CONCLUSIONS

Our results did not show strong associations of NSES, walkability, or green space with falling. Future research should incorporate granular environmental measures that may directly relate to physical activity and outdoor engagement.

Relationship between postural stability and fall risk in young adult after lower limb muscle fatigue

Introduction: Muscle fatigue can reduce body balance and activity of daily living tasks. Therefore, this study aims to identify the correlation between postural stability and fall risk due to muscle fatigue. The components in postural stability include Overall Stability Index (OSI), Anterior-Posterior Stability Index (APSI), and Mediolateral Stability Index (MLSI). Design and Methods: A total of seven healthy adults aged 31.1±7.4 years were recruited in this study. The sit-to-stand (STS) protocol was used to induce lower limb muscle fatigue, while postural stability and fall risk were assessed using the Biodex Balance System (BBS) before and after muscle fatigue. Result: The result showed a significant increase in postural stability index after fatigue only for OSI with p<0.05, while no significant difference was found on APSI and MLSI with p=0.157 and p=0.109 respectively. However, the mean score for the postural stability index showed an increase in percentage with 47.8% in OSI, 26.3% in APSI and 46.8% in MLSI.  Furthermore,fall risk showed no significant differences with p=0.149, but the mean score data increased by 16.7% after fatigue. The correlation between fall risk and OSI was significant with p<0.05, while MLSI had a significant negative correlation with APSI (p<0.05). Conclusions: Based on the results, the young adults had reduced overall postural stability but were less affected by fall risk after muscle fatigue. The positive correlation between OSI and fall risk indicated that their overall postural stability can induce the fall risk after muscle fatigue. Therefore, young adults need to be aware of their fatigue symptoms during prolonged exercise that can increase fall risk potential.

Stiffness Optimal Modulation of a Variable Stiffness Energy Storage Hip Exoskeleton and Experiments on Its Assistance Effect

Lower limb energy storage assisted exoskeletons realize walking assistance by using the energy stored by elastic elements during walking. Such exoskeletons are characterized by a small volume, light weight and low price. However, energy storage assisted exoskeletons adopt fixed stiffness joints typically, which cannot adapt to changes of the wearer's height, weight, or walking speed. In this study, based on the analysis of the energy flow characteristics and stiffness change characteristics of lower limb joints during a human walking on flat ground, a novel variable stiffness energy storage assisted hip exoskeleton is designed, and a stiffness optimization modulation method is proposed to store most of the negative work done by the human hip joint when walking. Through the analysis of the surface electromyography signals of the rectus femoris and long head of the biceps femoris, it is found that the muscle fatigue of the rectus femoris is reduced by 8.5% under the optimal stiffness assistance condition, and the exoskeleton provides better assistance under the optimal stiffness assistance condition.

Falls During Inpatient Rehabilitation After Spinal Cord Injury: Characterization, Clock-Hour Visualization, and Time to Event Predictors

OBJECTIVES

To (1) determine fall characteristics (eg, cause, location, witnesses) of inpatients with spinal cord injury (SCI) and whether they were different for ambulatory persons vs wheelchair users; (2) visualize the total number of daily falls per clock-hour for different inpatients' features (eg, cause of injury, age); (3) compare clinical and demographic characteristics of inpatients who experienced a first fall event vs inpatients who did not experience such event; and (4) identify first fall event predictors.

DESIGN

Retrospective observational cohort study.

SETTING

Institution for inpatient neurologic rehabilitation.

PARTICIPANTS

Persons with SCI (N=1294) admitted to a rehabilitation facility between 2005 and 2022.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Functional independence measure (FIM), Hospital Anxiety and Depression Scale (HADS), American Spinal Injury Association Impairment Scale (AIS), and Spinal Cord Independence Measure (SCIM) at admission. Kaplan-Meier survival curves and Cox proportional hazards models were used.

RESULTS

A total of 502 fall events were experienced by 369 ambulatory inpatients (19.8%) and wheelchair users (80.2%) in 63.9% of cases being alone, with cause, situation, and location significantly different in both groups. Clock-hour visualizations revealed an absolute peak at 12 AM (complete or incomplete injuries, with paraplegia or tetraplegia) but a relative peak at 9 AM mainly including incomplete patients with paraplegia. Of the (n=1294) included patients, 16.8% experienced at least 1 fall. Fallen patients reported higher levels of HADS depression, lower total SCIM, and longer time since injury to admission, with no differences in age, sex, educational level, FIM (quasi-significant), and AIS grade. Multivariable Cox proportional hazards identified time since injury to admission and AIS grade D as significant predictors of first fall event.

CONCLUSIONS

Falls identification, characterization, and clock-hour visualization can support decisions for mitigation strategies specifically addressed to inpatients with SCI. Fall predictors were identified as a first step for future research.

Interaction between age and fatigue on antagonist muscle coactivation during an acute post-fatigue recovery phase

This study investigated the age-related changes in antagonist muscle coactivation of the biceps femoris (BF) during an acute recovery period following a leg extensor fatiguing protocol. Twenty-three young (mean ± SD: age = 25.1 ± 3.0 years) and twenty-three old men (age = 71.5 ± 3.9 years) participated. Surface electromyography (sEMG) was recorded from the BF muscles for antagonist muscle coactivation. Testing involved participants performing leg extension isometric maximal voluntary contractions (MVCs) and isokinetic MVCs at 240°·s^-1 at baseline (Pre) and again after the fatigue protocol at 0 (Post0), 7 (Post7), 15 (Post15), and 30 (Post30) minutes post fatigue. Root mean square (RMS) values were computed from the BF sEMG and were calculated as the first 200 ms from onset for the isometric (IsomCoact200ms) and dynamic isokinetic 240°·s^-1 (DynCoact200ms) MVCs, and for the final 10° of the leg extension (DynCoact10°) on the isokinetic 240°·s^-1 MVCs. Two-way ANOVAs [age group (young vs. old) × time (Pre vs. Post0 vs. Post7 vs. Post15 vs. Post30)] showed that DynCoact200ms had an effect for time (p = 0.018), with greater antagonist coactivation in Pre than Post0 (p = 0.009) and recovering by Post7 (p = 0.011) with no group differences. DynCoact10° had no age × time interaction (p = 0.070), but had a main effect for time (p = 0.020) with the Post0 being lower than the Pre. However, for this variable the young group showed a more severe Pre to Post0 fatigue decline (-45.9%) than the old group (-6.7%) indicating this may be a more sensitive variable for capturing age-related antagonist coactivation post-fatigue responses. Leg extensor fatigue affects some BF coactivation sEMG variables more than others, and any altered post-fatigue coactivation response recovers rapidly (<7 min) from baseline levels.

Gait balance control after fatigue: Effects of age and cognitive demand

BACKGROUND

Fatigue is a commonly mentioned symptom in older adults, and walking under the influence of fatigue frequently occurs in daily activities. Studies have reported individual effects from fatigue or cognitive demand on gait performance. However, the information on how fatigue and cognitive demand interact to affect gait balance control is still lacking.

RESEARCH QUESTION

How does fatigue affect walking balance control in young and older adults with and without performing a concurrent cognitive task?

METHODS

We collected and analyzed motion data from 17 young and 17 older adults, who performed over-ground walking with and without a concurrent working memory test, before and after been fatigued by performing repetitive sit-to-stand movements. Three-way ANOVAs were used for statistical analysis with Age (young and older adults), Fatigue (pre- and post-fatigue), and Task (single-task and dual-task) as factors.

RESULTS

From pre- to post-fatigue, an increased gait velocity was observed during dual-task walking regardless of age (p = .02). Only young adults demonstrated a significant increase in mediolateral center of mass displacement (M-L CoM) at post-fatigue (p = .019). Accuracies of the working memory test were not affected by Age, Task, or Fatigue.

SIGNIFICANCE

Our findings revealed that gait balance control, as measured by the M-L CoM, deteriorated post-fatigue in young adults. Older adults maintained their mediolateral body sway from pre-fatigue to post-fatigue. Fatigue effects were not further exacerbated during dual-task walking, and similar cognitive performance was maintained as performance fatigability increased.

Exploring the role of the left DLPFC in fatigue during unresisted rhythmic movements

Understanding central fatigue during motor activities is important in neuroscience and different medical fields. The central mechanisms of motor fatigue are known in depth for isometric muscle contractions; however, current knowledge about rhythmic movements and central fatigue is rather scarce. In this study, we explored the role of an executive area (left dorsolateral prefrontal cortex [DLPFC]) in fatigue development during rhythmic movement execution, finger tapping (FT) at the maximal rate, and fatigue after effects on the stability of rhythmic patterns. Participants (n = 19) performed six sets of unresisted FT (with a 3 min rest in‐between). Each set included four interleaved 30 s repetitions of self‐selected (two repetitions) and maximal rate FT (two repetitions) without rest in‐between. Left DLPFC involvement in the task was perturbed by transcranial static magnetic stimulation (tSMS) in two sessions (one real and one sham). Moreover, half of the self‐selected FT repetitions were performed concurrently with a demanding cognitive task, the Stroop test. Compared with sham stimulation, real tSMS stimulation prevented waning in tapping frequency at the maximal rate without affecting perceived levels of fatigue. Participants' engagement in the Stroop test just prior to maximal FT reduced the movement amplitude during this mode of execution. Movement variability at self‐selected rates increased during Stroop execution, especially under fatigue previously induced by maximal FT. Our results indicate cognitive‐motor interactions and a prominent role of the prefrontal cortex in fatigue and the motor control of simple repetitive movement patterns. We suggest the need to approach motor fatigue including cognitive perspectives.

We show the fundamental role of executive areas in fatigue caused by very simple repetitive movements. Fatigue developed less during the maximal frequency of movement production, while the left DLPFC received magnetic stimulation (in right‐handers). The role of cognitive‐motor interaction in fine motor control was also clear when participants engaged in cognitive tasks. At the clinical level, our work reinforces the need to treat fatigue from a comprehensive perspective.

Changes in trunk and head acceleration during the 6-minute walk test and its relation to falls risk for adults with multiple sclerosis

For persons with multiple sclerosis (MS), the general decline in neuromuscular function underlies diminished balance, impaired gait and consequently, increased risk of falling. During gait, optimal control of head motion is an important feature which is achieved partly through control of the trunk-neck region to dampen gait-related oscillations. The primary aim of this study was to examine the effect performing a 6-minute walk test (6MWT) has on head, neck and trunk accelerations in individuals with MS. This was addressed using a repeated measures generalized linear model. We were also interested in assessing whether the 6MWT has an impact on a person's falls risk and specific physiological measures related to falls. Finally the relation between the amplitude (i.e., mean RMS) of head and trunk accelerations and falls risk was examined using linear regression. The main results were that over the course of the 6MWT, individuals progressively slowed down coupled with a concurrent increase in gait-related upper body accelerations (p's > 0.05). Despite the increased acceleration, no significant changes in attenuation from the trunk to the head were observed, indicating that persons were able to maintain an optimal level of control over these oscillations. Performing the 6MWT also had a negative impact on posture, with falls risk significantly increasing following this test (p > 0.05). Interestingly, the overall falls risk values were strongly linked with vertical accelerations about the trunk and head, but not average walking speed during the 6MWT. Overall, performing the 6MWT leads to changes in walking speed, upper body acceleration patterns and increases in overall falls risk.

Foot angular kinematics measured with inertial measurement units: A reliable criterion for real-time gait event detection

Accurate and reliable real-time detection of gait events using inertial measurement units (IMUs) is crucial for (1) developing clinically meaningful gait parameters to differentiate normal and impaired gait or (2) creating patient-tailored gait rehabilitation strategies or control of prosthetic devices using feedback from gait phases. However, most previous studies focused only on algorithms with high temporal accuracy and neglected the importance of (1) high reliability, i.e., detecting only and all true gait events, and (2) real-time implementation. Thus, in this study, we presented a novel approach for initial contact (IC) and terminal contact (TC) detection in real-time based on the measurement of the foot orientation. Unlike foot/shank angular velocity and acceleration, foot orientation provides physiologically meaningful kinematic features corresponding to our observational recognition of IC and TC, regardless of the walking modality. We conducted an experimental study to validate our algorithm, including seven participants performing four walking/running activities. By analyzing 5,555 ICs/TCs recorded during the tests, only our algorithm achieved a sensitivity and precision of 100%. Our obtained temporal accuracy (mean ± standard deviation of errors ranging from 0 ± 3 to 6 ± 5 time samples; sampling frequency: 100 Hz) was better than or comparable to those reported in the literature. Our algorithm's performance does not depend on thresholds and gait speed/modality, and it can be used for feedback-based therapeutic gait training or real-time control of assistive or prosthetic technologies. Nevertheless, its performance for pathological gait must be validated in the future. Finally, we shared the codes and sample data on https://www.ncbl.ualberta.ca/codes.

Effect of Lower Limb Muscle Fatigue on Fall Risk for Transfemoral Amputee: A Pilot Study

Muscle fatigue is a decline in muscle maximum force during contraction and can influence the fall risk among people. This study is aimed at identifying the effect of fatigue on prospective fall risk in transfemoral amputees (TFA). Fourteen subjects were involved in this study with TFA (34.7 ± 8.1 yrs, n = 7) and normal subjects (31.1 ± 7.4 yrs, n = 7). Fatigue of lower limb muscles was induced with the fatigue protocol. Subjects were tested prefatigue and postfatigue using the standardized fall risk assessment. All results were calculated and compared between pre- and postfatigue to identify fatigue's effect on both groups of subjects. The results showed that the fall risk increased significantly during pre- and postfatigue for TFA (p = 0.018), while there were no significant differences in normal subjects (p = 0.149). Meanwhile, the fall risk between TFA and normal subjects for prefatigue (p = 0.082) and postfatigue (p = 0.084) also showed no significant differences. The percentage (%) of increased fall risk for TFA was 19.2% compared to normal subjects only 16.7%. However, 61.4% increased of % fall risk in TFA after fatigue by using the baseline of the normal subject as the normalized % of fall risk. The increasing fall risks for TFA after fatigue are three times higher than the potential fall risk in normal subjects. The result indicates that they need to perform more precautions while prolonging lower limb activities. These results showed the implications of fatigue that can increase the fall risk due to muscle fatigue from repetitive and prolonged activities. Therefore, rehabilitation programs can be done very safely and precisely so that therapists can pursue fitness without aggravating existing injuries.

The Acute Effects of Fast-Paced Walking on Isometric Peak Torque and Rate of Torque Development in Regularly Exercising and Inactive Older Women

This study aimed to examine the acute effects of fast-paced walking on isometric peak torque and rate of torque development (RTD) in regular exercising and inactive older women. Ten regular exercising (67 ± 4 years) and 10 inactive (68 ± 4 years) older women performed three isometric knee extension contractions before and after a control condition (quiet resting) and an experimental condition of fast-paced walking for 6 min. Peak torque and early (RTD100), late (RTD200), and maximum (peak RTD) RTD measurements were obtained from each contraction. Results showed no significant changes in peak torque, peak RTD, or RTD200 after walking for either group (p > .050). A significant decrease in RTD100 was observed after walking for the inactive group (p = .005) but not for the regular exercisers (p = .909). These findings highlight the importance of physical activity and suggest that a task as simple as walking may impair the rapid strength capacities of inactive older women.

An interrater reliability study of gait analysis systems with the dual task paradigm in healthy young and older adults

Background and aims

One reason for the controversial discussion of whether the dual task (DT) walking paradigm has an added value for diagnosis in clinical conditions might be the use of different gait measurement systems. Therefore, the purpose was 1) to detect DT effects of central gait parameters obtained from five different gait analysis devices in young and old adults, 2) to assess the consistency of the measurement systems, and 3) to determine if the absolut and proportional DT costs (DTC) are greater than the system-measurement error under ST.

Methods

Twelve old (72.2 ± 7.9y) and 14 young adults (28.3 ± 6.2y) walked a 14.7-m distance under ST and DT at a self-selected gait velocity. Interrater reliability, precision of the measurement and sensitivity to change were calculated under ST and DT.

Results

An age effect was observed in almost all gait parameters for the ST condition. For DT only differences for stride length (p < .029, ɳ²_p = .239) as well as single and double limb support (p = .036, ɳ²_p = .227; p = .034, ɳ²_p = .218) remained. The measurement systems showed a lower absolute agreement compared to consistency across all systems.

Conclusions

When reporting DT effects, the real changes in performance and random measurement errors should always be accounted for. These findings have strong implications for interpreting DT effects.

A PRELIMINARY ASSESSMENT OF PHYSICAL WORK EXPOSURES AMONG ELECTRONIC WASTE WORKERS AT AGBOGBLOSHIE, ACCRA GHANA

Occupational exposure associated with unstructured, informal e-waste recycling has received very limited attention. This study aimed to quantify the occupational physical exposures among informal e-waste workers at the largest e-waste site in Africa. A cross-sectional field survey of 163 male e-waste workers was conducted using a self-report occupational physical activity questionnaire, along with direct work observations, and pedometer estimates of walking activity for a subset of workers (n = 42). Results indicated significant differences in self-reported 7-day work exposures among the three main e-waste job categories, namely, collectors (n = 70), dismantlers (n = 73) and burners (n = 20). Prolonged walking, sitting and standing on five or more days in the workweek was frequently reported by collectors (87%), dismantlers (82%) and burners (60%), respectively. Nearly 90% of collectors and burners and 60% of dismantlers reported lifting and carrying on five or more days in the workweek. The exposure combinations identified suggest a risk for musculoskeletal disorders (MSDs). Findings call attention to the need for research examining potential associations between physical exposures and MSDs affecting e-waste workers in Agbogbloshie. The high exposure variability both between and within workers has implications for future exposure assessments conducted in unregulated, informal work settings.

Older adult pedestrian trauma: A systematic review, meta-analysis, and GRADE assessment of injury health outcomes from an aggregate study sample of 1 million pedestrians

This systematic review sought to assess older adult pedestrian injury severity, injury by anatomical location and incidence proportions, including comparisons to younger age groups when available and provide an analysis of the quality of the existing evidence. A structured search was conducted in PubMed, Embase, Scopus, CINAHL, PsycInfo, AMED, Web of Science, LILACS and TRID. STROBE was used to assess the reporting quality of the included studies. Random-effect model meta-analysis served to obtain pooled relative risk, incidence proportions and standardized mean differences for different outcomes due to pedestrian crashes comparing older and younger pedestrians, while meta-analyses could not be conducted for pedestrian falls. We screened 7460 records of which 60 studies (1,012,041 pedestrians) were included in the review. Injured pedestrians 60+ compared to those <60 were found to have a higher relative risk of severe injury (pooled relative risk RR 1.6, 95 % CI: 1.4-2.0 p < 0.001), critical care admission (pooled RR 1.5, 95 %CI: 1.3-1.8 p < 0.001), and fatality (pooled RR of 3.7, 95 % CI: 3.0-4.5 p < 0.001). Pedestrians 60+ also had higher incidence rates of pedestrian falls causing higher injury severity. GRADE was used to evaluate evidence quality, with the results suggesting that the overall quality of the evidence supporting these findings was low. Further research is needed to understand health risks associated with older pedestrian trauma and to develop effective risk management strategies.

Higher Fatigue Prospectively Increases the Risk of Falls in Older Men

Background and Objectives

Fatigue is a common complaint and shares many risk factors with falls, yet the independent contribution of fatigue on fall risk is unclear. This study’s primary aim was to assess the association between fatigue and prospective fall risk in 5642 men aged 64–100 enrolled in the Osteoporotic Fractures in Men Study (MrOS). The secondary aim was to examine the association between fatigue and recurrent fall risk.

Research Design and Methods

Fatigue was measured at baseline using the Medical Outcomes Study (short form) single-item question “During the past four weeks, how much of the time did you feel energetic?” Responses were then classified: higher fatigue = “none,” “a little,” or “some” of the time and lower fatigue = “a good bit,” “most,” or “all” of the time. We assessed falls using triannual questionnaires. Fall risk was examined prospectively over 3 years; recurrent falling was defined as at least 2 falls within the first year. Generalized estimating equations and multinomial logistic regression modeled prospective and recurrent fall risk as a function of baseline fatigue status, adjusted for demographics, medications, physical activity, and gait speed.

Results

Men with higher (26%) versus lower baseline fatigue were older (75.1 ± 6.2 vs 73.2 ± 5.7 years), 24% less active, and had worse physical function (gait speed = 1.09 ± 0.24 vs 1.24 ± 0.21 m/s), all p < .0001. Within 1 year, 25.4% (n = 1409) had fallen at least once, of which 47.4% (n = 668) were recurrent fallers. Men with higher versus lower fatigue had 25% increased fall risk (relative risk = 1.25, 95% CI: 1.14–1.36) over 3 years follow-up, but had 50% increased odds of recurrent falling (odds ratio = 1.50, 95% CI: 1.22–1.85) within the first year.

Discussion and Implications

Fatigue is an important risk factor of falling independent of established risk factors. Reductions in fatigue (ie, increased energy) may lessen the burden of falls in older men and provide a novel avenue for fall risk intervention.

Delayed Impairment of Postural, Physical, and Muscular Functions Following Downhill Compared to Level Walking in Older People

Transient symptoms of muscle damage emanating from unaccustomed eccentric exercise can adversely affect muscle function and potentially increase the risk of falling for several days. Therefore, the aims of the present study were to investigate the shorter- and longer-lasting temporal characteristics of muscle fatigue and damage induced by level (i.e., concentrically biased contractions) or downhill (i.e., eccentrically biased contractions) walking on postural, physical, and muscular functions in older people. Nineteen participants were matched in pairs for sex, age and self-selected walking speed and allocated to a level (n = 10, age = 72.3 ± 2.9 years) or downhill (n = 9, age = 72.1 ± 2.2 years) walking group. Postural sway, muscle torque and power, physical function (5× and 60 s sit-to-stand; STS), and mobility (Timed-Up-and-Go; TUG) were evaluated at baseline (pre-exercise), 1 min, 15 min, 30 min, 24 h, and 48 h after 30 min of level (0% gradient) or downhill (−10% gradient) walking on a treadmill. Following downhill walking, postural sway (+66 to 256%), TUG (+29%), 60 s STS (+29%), five times STS (−25%) and concentric power (−33%) did not change at 1–30 min post exercise, but were significantly different (p < 0.05) at 24 and48 h post-exercise when compared to baseline (p < 0.05). Muscle torque decreased immediately after downhill walking and remained impaired at 48 h post-exercise (−27 to −38%). Immediately following level walking there was an increase in postural sway (+52 to +98%), slower TUG performance (+29%), fewer STS cycles in 60 s (−23%), slower time to reach five STS cycles (+20%) and impaired muscle torque (−23%) and power (−19%) which returned to baseline 30-min after exercise cessation (p > 0.05). These findings have established for the first time distinct impairment profiles between concentric and eccentric exercise. Muscle damage emanating from eccentrically biased exercise can lead to muscle weakness, postural instability and impaired physical function persisting for several days, possibly endangering older adult’s safety during activities of daily living by increasing the risk of falls.

Effects of Manual Material Handling Workload on Measures of Fall Risk

OCCUPATIONAL APPLICATIONS We found, contrary to expectations, that performing a fatiguing simulated heavy manual material handling (MMH) task did not adversely affect the risk of trip-induced falls when compared to a less-fatiguing light MMH task. However, when considering these MMH tasks together rather than in comparison, our results provide evidence for adverse effects of fatigue on both gait and the ability to recover balance after tripping. The current results provide additional evidence that physical fatigue increases fall risk, start to clarify the mechanisms by which this increase occurs, and can help in developing and evaluating fall prevention strategies targeting these mechanisms.

Age-specific modulation of intermuscular beta coherence during gait before and after experimentally induced fatigue

We examined the effects of age on intermuscular beta-band (15-35 Hz) coherence during treadmill walking before and after experimentally induced fatigue. Older (n = 12) and younger (n = 12) adults walked on a treadmill at 1.2 m/s for 3 min before and after repetitive sit-to-stand, rSTS, to induce muscle fatigability. We measured stride outcomes and coherence from 100 steps in the dominant leg for the synergistic (biceps femoris (BF)-semitendinosus, rectus femoris (RF)-vastus lateralis (VL), gastrocnemius lateralis (GL)-Soleus (SL), tibialis anterior (TA)-peroneus longus (PL)) and for the antagonistic (RF-BF and TA-GL) muscle pairs at late swing and early stance. Older vs. younger adults had 43-62% lower GL-SL, RF-VL coherence in swing and TA-PL and RF-VL coherence in stance. After rSTS, RF-BF coherence in late swing decreased by ~ 20% and TA-PL increased by 16% independent of age (p = 0.02). Also, GL-SL coherence decreased by ~ 23% and increased by ~ 23% in younger and older, respectively. Age affects the oscillatory coupling between synergistic muscle pairs, delivered presumably via corticospinal tracts, during treadmill walking. Muscle fatigability elicits age-specific changes in the common fluctuations in muscle activity, which could be interpreted as a compensation for muscle fatigability to maintain gait performance.

The U-Shaped Relationship Between Levels of Bouted Activity and Fall Incidence in Community-Dwelling Older Adults: A Prospective Cohort Study

BACKGROUND

It remains uncertain whether the association between physical activity (PA) and falls is U-shaped, and few studies have explored the potential mediation of PA accumulation pattern.

METHODS

We measured PA in 671 community-dwelling older adults (82.7 ± 3.8 years) using wrist-worn accelerometer for 7 days. PA was further classified to bouted PA (≥10 minutes bout length) and sporadic PA (<10 minutes bout length) for subanalysis. Fall incidence in the following 12-month was recorded through tri-monthly telephone interviews. Classification and Regression Tree analysis was used to identify two optimal cutoff values of each PA measurement to predict falls. Participants were then divided into "inactive," "moderately active," and "highly active" groups accordingly. Negative binomial regression models were used to estimate the association between the PA measures and fall incidence.

RESULTS

Six hundred and thirty-nine participants completed 12-month follow-up. Ninety-three (14.6%) experienced a total of 118 falls. Inactive and highly active older adults had higher falls per person month relative to the moderately active group (inactive: incidence rate ratios [IRR] = 2.372, 95% confidence interval [CI] = 1.317-4.271; highly active: IRR = 2.731, 95% CI = 1.196-6.232). Subanalyses found similar significant finding with bouted PA (p < .001) but not sporadic PA (p ≥ .221). The association between bouted PA and falls remained significant even after adjusting fall incidence for bouted activity time (inactive: IRR = 3.636, 95% CI = 2.238-5.907; highly active: IRR = 1.823, 95% CI = 1.072-3.1). Further adjustments for fall-related risk factors did not meaningfully change the results.

CONCLUSION

A U-shaped relationship was identified between bouted but not sporadic PA and fall incidence. There is an approximately twofold increase in fall rate in highly active older adults even after adjusting for activity time.

Acute Effects of Single- Versus Double-Leg Postactivation Potentiation on Postural Balance of Older Women: An Age-Matched Controlled Study

AIMS

To compare the postactivation potentiation effects of isometric contraction until failure in double- and single-leg tasks on older women's balance.

METHODS

The one-legged balance test was performed before and immediately after a rise-to-toes task until the task failure. Older women were divided into two groups: a group performed the task with double leg (n = 43) and the other group with single-leg support (n = 55).

RESULTS

The single-leg group showed slower velocity of sway post rise-to-toes task (pre = 4.02 ± 1; post = 3.78 ± 1.15 m/s; p = .04) without differences for the center of pressure path length (pre = 79 ± 21; post = 75 ± 23 cm; p = .08). In the double-leg group, faster velocity of sway (pre = 4 ± 1.22; post = 4.25 ± 1.13; p = .03) and increased center of pressure path length (pre = 80 ± 24; post = 85 ± 23 cm; p = .03) were observed after the task.

CONCLUSIONS

The single-leg group showed improved balance outcomes due to postactivation potentiation, while the double-leg group showed worsened balance consistent with muscle fatigue.

Gait Performance in People with Symptomatic, Chronic Mild Traumatic Brain Injury

There is a dearth of knowledge about how symptom severity affects gait in the chronic (>3 months) mild traumatic brain injury (mTBI) population despite up to 53% of people reporting persisting symptoms after mTBI. The aim of this investigation was to determine whether gait is affected in a symptomatic, chronic mTBI group and to assess the relationship between gait performance and symptom severity on the Neurobehavioral Symptom Inventory (NSI). Gait was assessed under single- and dual-task conditions using five inertial sensors in 57 control subjects and 65 persons with chronic mTBI (1.0 year from mTBI). The single- and dual-task gait domains of Pace, Rhythm, Variability, and Turning were calculated from individual gait characteristics. Dual-task cost (DTC) was calculated for each domain. The mTBI group walked (domain z-score mean difference, single-task = 0.70; dual-task = 0.71) and turned (z-score mean difference, single-task = 0.69; dual-task = 0.70) slower (p < 0.001) under both gait conditions, with less rhythm under dual-task gait (z-score difference = 0.21; p = 0.001). DTC was not different between groups. Higher NSI somatic subscore was related to higher single- and dual-task gait variability as well as slower dual-task pace and turning (p < 0.01). Persons with chronic mTBI and persistent symptoms exhibited altered gait, particularly under dual-task, and worse gait performance related to greater symptom severity. Future gait research in chronic mTBI should assess the possible underlying physiological mechanisms for persistent symptoms and gait deficits.

Shoes with active insoles mitigate declines in balance after fatigue

Fatigue can induce postural instability and even lead to falls. However, most current methods to delay or reduce fatigue require long preparatory time, or large and expensive equipment. We propose a convenient method to alleviate postural instability due to fatigue. We paid attention to that fatigue and aging share similar neurophysiological deterioration of sensory-motor function. Considering that stochastic resonance via sub-sensory mechanical vibration increases postural stability in the elderly, we propose that sub-sensory insole vibration reduces the negative effect of fatigue on postural control. We performed experiments with 21 young and healthy adult participants, and demonstrated that insole vibration compensates for the loss of balance ability due to fatigue. The sub-sensory insole vibration restored both the area of center of pressure and the complexity of the time series of the motor output after fatigue to the pre-fatigue levels. The insole units generating the vibration were completely concealed in shoes and controlled by a smart phone. This compact implementation contrasts with the cumbersome procedure of current solutions to fatigue-induced postural instability.

Effects of experimentally induced fatigue on healthy older adults' gait: A systematic review

Introduction

While fatigue is ubiquitous in old age and visibly interferes with mobility, studies have not yet examined the effects of self-reported fatigue on healthy older adults’ gait. As a model that simulates this daily phenomenon, we systematically reviewed eleven studies that compared the effects of experimentally induced muscle and mental performance fatigability on gait kinematics, variability, kinetics, and muscle activity in healthy older adults.

Methods

We searched for studies in databases (PubMed and Web of Science) using Fatigue, Gait, and Clinical conditions as the main terms and extracted the data only from studies that experimentally induced fatigue by sustained muscle or mental activities in healthy older adults.

Results

Eleven studies were included. After muscle performance fatigability, six of nine studies observed increases in stride length, width, gait velocity (Effect Size [ES] range: 0.30 to 1.22), inter-stride trunk acceleration variability (ES: 2.06), and ankle muscle coactivation during gait (ES: 0.59, n = 1 study). After sustained mental activity, the coefficient of variation of stride outcomes increased (ES: 0.59 to 0.67, n = 1 study) during dual-task but not single-task walking.

Conclusion

Muscle performance fatigability affects spatial and temporal features of gait and, mainly, inter-stride trunk acceleration variability. In contrast, sustained mental activity tends only to affect step variability during dual tasking. A critical and immediate step for future studies is to determine the effects of self-reported fatigue on gait biomechanics and variability in healthy older adults to verify the viability of experimentally induced fatigue as a model for the study of gait adaptability in old age.

Development and Validation of the Norfolk Quality of Life Fatigue Tool (QOL-F): A New Measure of Perception of Fatigue

OBJECTIVES

To design a questionnaire to evaluate and distinguish between cognitive and physical aspects of fatigue in different age groups of "nondiseased" people and guide appropriate prevention and interventions for the impact of frailty occurring in normative aging.

STUDY DESIGN AND PARTICIPANTS

The Norfolk QOL-Fatigue (QOL-F) with items of cognitive and physical fatigue, anxiety, and depression from validated questionnaires including items from the Patient-Reported Outcomes Measure Information System (PROMIS) databank was developed. The preliminary QOL-F was administered to 409 healthy multiethnic local participants (30-80 years old) in 5 age groups.

METHODS

The authors distilled the item pool using exploratory (EFA) and confirmatory factor analysis (CFA). EFA identified 5 latent groups as possible factors related to problems due to fatigue, subjective fatigue, reduced activities, impaired activities of daily living (ADL), and depression.

RESULTS

CFA demonstrated good overall fit [χ²(172) = 1094.23, P < .001; Tucker-Lewis index = 0.978; root mean square error of approximation = 0.049] with factor loadings >0.617 and strong interfactor correlations (0.69-0.83), suggesting that fatigue in each domain is closely related to other domains and to the overall scale except for ADL. The 5-factor solution displayed good internal consistency (Cronbach α = 0.78-0.94). Total and domain scores were fairly equivalent in all age groups except for the 40 to 49-year-old group with better overall scores. In addition, 70 to 79-year-olds had better ADL scores. In item response analysis, factor scores in different age groups were similar, so age may not be a significant driver of fatigue scores. Fatigue scores were significantly higher in females than in males (P < .05).

CONCLUSIONS AND CLINICAL IMPLICATIONS

The developed Norfolk QOL-F tool demonstrated fatigue as a perceived cognitive phenomenon rather than an objective physical measure, suggesting mandatory inclusion of cognitive as well as physical measures in the evaluation of people as they age. QOL-F is able to distinguish QOL-F domain scores unique to different age groups, proposing clinical benefits from physical, balance, and cognitive interventions tailored to impact frailty occurring in normative aging.

Impacts of aquatic walking on arterial stiffness, exercise tolerance, and physical function in patients with peripheral artery disease: a randomized clinical trial

Peripheral artery disease (PAD) is an atherosclerotic disease that is associated with attenuated vascular function, cardiorespiratory capacity, physical function, and muscular strength. It is essential to combat these negative effects on health by incorporating lifestyle interventions to slow disease progression, such as exercise. We sought to examine the effects of aquatic walking exercise on cardiovascular function, cardiorespiratory capacity [maximal volume of oxygen consumption (V̇o_2max)], exercise tolerance [6-min walking distance (6MWD)], physical function, muscular strength, and body composition in patients with PAD. Patients with PAD (n = 72) were recruited and randomly assigned to a 12-wk aquatic walking training group (AQ, n = 35) or a control group (CON, n = 37). The AQ group performed walking and leg exercises in waist-to-chest-deep water. Leg arterial stiffness [femoral-to-ankle pulse wave velocity (legPWV)], heart rate (HR), blood pressure (BP), ankle-to-brachial index (ABI), V̇o_2max, 6MWD, physical function, muscular strength, body composition, resting metabolic rate (RMR), and flexibility were measured before and after 12 wk. There were significant group × time interactions (P < 0.05) after 12 wk for legPWV and HR, which significantly decreased (P < 0.05) in AQ, and V̇o_2max, 6MWD, physical function, and muscular strength, which significantly increased (P < 0.05) in AQ, compared with no changes in CON. There were no significant differences (P > 0.05) for BP, ABI, RMR, or flexibility after 12 wk. Interestingly, there was relatively high adherence (84%) to the aquatic walking exercise program in this population. These results suggest that aquatic walking exercise is an effective therapy to reduce arterial stiffness and resting HR and improve cardiorespiratory capacity, exercise tolerance, physical function, and muscular strength in patients with PAD.NEW & NOTEWORTHY The results of this study reveal for the first time that aquatic walking exercise can decrease arterial stiffness and improve exercise tolerance, cardiorespiratory capacity, and muscular strength in patients with peripheral artery disease (PAD). Aquatic walking exercise training demonstrates relatively high exercise adherence in this population. Aquatic walking exercise training may be a useful therapeutic intervention for improving physical function in patients with PAD.

The Effect of Yearly-Dose Vitamin D Supplementation on Muscle Function in Mice

Supplementation with vitamin D helps to alleviate weakness and fatigue seen with deficiency. However, large bolus doses appear to worsen the risk of falls. Whether this occurs as a direct result of muscle weakness is currently unknown. Thus, the aims of this study were to examine the muscle function following administration of high doses of vitamin D. Given the safety issues associated with bolus doses, experiments were conducted on C57BL6 mice. Mice at eight weeks of age with otherwise normal levels of vitamin D were supplemented for four weeks with a high dose (HIGH; n = 12) of vitamin D (20000 IU/kg food) designed to provide a year's worth of vitamin D. These mice were compared to another group who received that same yearly dose in a single bolus i.p. injection (YEAR; n = 12). Mice provided with standard mouse chow, which contained 1000 IU/kg food, and injected with the vitamin D vehicle were used as controls (CON; n = 16). Force and fatigue properties of hind limb fast- and slow-twitch muscles were measured. CON animals ingested vitamin D consistent with typical human supplementation. HIGH animals consumed significantly more food than the CON animals, such that they ingested more than a year's worth of vitamin D in four weeks. Despite this, there were few differences in the muscle function compared with CON. YEAR animals demonstrated lower absolute and relative forces in both muscles compared to the HIGH animals, as well as lower force during fatigue and early recovery. Large bolus doses of vitamin D appear to have detrimental effects on the skeletal muscle function, likely being a contributor to increased risk of falls observed with similar doses in humans. Mice ingesting the same amount over four weeks did not demonstrate the same deleterious effects, suggesting this may be a safe way to provide high vitamin D if required.

Differences in Cognitive-Motor Interference in Older Adults While Walking and Performing a Visual-Verbal Stroop Task

Objectives: Studies using the dual-task (DT) paradigm to explain age-related performance decline due to cognitive-motor interference (CMI) which causes DT costs (DTCs) revealed contradictory results for performances under DT conditions. This cross-sectional study analyzed whether differences in demographics, physical functioning, concerns of falling (CoF), and other mental factors can explain positive and negative DTCs in older adults while walking in DT situations.

Methodology: N = 222 participants (57–89 years) performed a single task (ST) and a DT walking condition (visual-verbal Stroop task) in randomized order on a treadmill. Gait parameters (step length, step width) were measured at a constant self-selected walking speed. Demographics [age, Mini Mental Status Examination (MMSE)], physical functioning (hand grip strength), CoF [Falls Efficacy Scale International (FES-I)], and mental factors [Short Form-12 (SF-12)] were assessed. An analysis of variance (ANOVA) was used to reveal subgroup differences. A four-step hierarchical regression analysis was conducted to identify which variables determine the DTC.

Results: Three subgroups were identified: (1) participants (n = 53) with positive DTCs (improvements under DT conditions); (2) participants with negative DTCs (n = 60) in all gait parameters; and (3) participants (n = 109) who revealed non-uniform DTCs. Baseline characteristics between the subgroups showed differences in age (F_(2,215) = 4.953; p = 0.008; η² = 0.044). The regression analysis revealed that physical functioning was associated with positive DTC and CoF with negative DTC.

Conclusion: The results confirmed a huge inter-individual variability in older adults. They lead us to suggest that factors causing performance differences in DTCs needs to be reassessed. Functional age seems to determine DTCs rather than calendric age. Psychological variables particularly seem to negatively influence DT performance.

Quedas recorrentes e fatores de risco em idosos institucionalizados

Resumo Queda recorrente representa alto risco de morbidade e mortalidade em idosos, principalmente institucionalizados, dado ao seu quadro de fragilidade e declínio funcional evidentes. O objetivo deste estudo é determinar a incidência e os fatores de risco relacionados a quedas recorrentes em idosos institucionalizados. Estudo longitudinal tipo coorte no período de um ano. Foram avaliados indivíduos com 60 anos ou mais residentes em 10 Instituições de Longa Permanência para Idosos, que deambulassem e possuíssem capacidade cognitiva preservada. Foi questionada a ocorrência de quedas nos últimos doze meses, considerando recorrentes a ocorrência de dois ou mais episódios neste período. Foram ainda coletadas variáveis referentes à instituição, condições sócio demográficas e de saúde do idoso através de questionários. Do total de 364 idosos, 130 foram incluídos. A incidência de quedas recorrentes foi de 26.9% (IC 95% = 22.4 – 31.5). A partir do Qui-quadrado e Regressão Logística, considerando o nível de significância de 5%, foi encontrada fadiga como fator de risco (p = 0.001; RR = 2.9) e uso de betabloqueadores como fator de proteção (p = 0.010; RR = 0.1). Conclui-se que queda recorrente é comum nas Instituições de Longa Permanência para Idosos e a fadiga representa fator de risco.

Effects of 10-week walking and walking with home-based resistance training on muscle quality, muscle size, and physical functional tests in healthy older individuals

Background

Older individuals have been shown to present muscle atrophy in conjunction with increased fat fraction in some muscles. The proportion of fat and connective tissue within the skeletal muscle can be estimated from axial B-mode ultrasound images using echo intensity (EI). EI was used to calculate the index of muscle quality. Walking, home-based weight-bearing resistance training, and its combinations are considered simple, easy, and practical exercise interventions for older adults. The purpose of this study was to quantify the effects of walking and walking with home-based resistance training on muscle quality of older individuals.

Methods

Thirty-one participants performed walking training only (W-group; 72 ± 5 years) and 33 participants performed walking and home-based resistance training (WR-group; 73 ± 6 years). This study was a non-randomized controlled trial with no control group. All participants were instructed to walk 2 or 3 sets per week for 10 weeks (one set: 30-min continuous walking). In addition, the WR-group performed home-based weight-bearing resistance training. EI was measured as a muscle quality index using axial B-mode ultrasound images of the rectus femoris and vastus lateralis of the mid-thigh. We further averaged these parameters to obtain the EI of the quadriceps femoris (QF). Participants further performed five functional tests: sit-ups, supine up, sit-to-stand, 5-m maximal walk, and 6-min walk.

Results

QF EI was significantly decreased in both groups after training (W-group 69.9 ± 7.4 a.u. to 61.7 ± 7.0 a.u., WR-group 64.0 ± 9.5 a.u. to 51.1 ± 10.0 a.u.; P < 0.05), suggesting improved muscle quality. QF EI was further decreased in the WR-group compared with the W-group. The sit-up test in both groups and the sit-to-stand and 5-m maximal walk tests in the W-group were significantly improved after training.

Conclusion

These results suggest that training-induced stimulation is associated with a decrease in EI in some thigh regions. Furthermore, the addition of home-based resistance training to walking would be effective for a greater reduction of EI.

Intraindividual Variability of Neuromotor Function Predicts Falls Risk in Older Adults and those with Type 2 Diabetes

This study was designed to examine the effect of increasing age and type 2 diabetes on the average responses and inter- and intraindividual variability of falls risk, reaction time, strength, and walking speed for healthy older adults and older persons with type 2 diabetes (T2DM). Seventy-five older individuals (controls) and 75 persons with T2DM aged between 50 and 79 years participated in the study. Assessments of falls risk, reaction time (RT), knee extension strength, and walking speed were conducted. The results revealed that advancing age for both control and T2DM groups was reflected by a progressive increase in falls risk, decreased leg strength and a decline (i.e., slowing) of reactions and gait speed. Conversely, the level of intraindividual variability for the RT, strength and gait measures increased with increasing age for both groups, with T2DM persons tending to be more variable compared to the healthy controls of similar age. In contrast to the intraindividual changes, measures of interindividual variability revealed few differences between the healthy elderly and T2DM individuals. Taken together, the findings support the proposition that intraindividual variability of neuromotor measures may be useful as a biomarker for the early detection of decline in physiological function due to age or disease.

Falls in older adults with multiple myeloma

OBJECTIVE

To examine the prevalence of falls, factors associated with falls and the relationship between falls and survival in older adults with multiple myeloma.

METHODS

In an analysis of the Surveillance, Epidemiology and End Results (SEER)-Medicare Health Outcomes Survey (MHOS)-linked database, we examined 405 older adults with multiple myeloma (MM) and 513 matched non-cancer controls. The primary outcome was self-reported within the past 12 months. Age, race, gender, symptoms, and comorbidities were self-reported in the MHOS. Survival was calculated from SEER data.

RESULTS

Of the patients with MM, 171 were within 1 year of diagnosis (cohort 1) and 234 were ≥1 year postdiagnosis (cohort 2). Patients in cohorts 1 and 2 were more likely to have fallen than controls (26% and 33% vs 23%, P = .012). On multivariate analysis, among patients with myeloma (combined cohorts 1 and 2), factors associated with falls included self-report of fatigue (aOR 2.52 [95% CI 1.34-4.93]), depression (aOR 1.90 [95% CI 1.14-3.18]), or poorer general health (aOR 1.86 [95% CI 1.05-3.36]). Falls were not associated with survival.

CONCLUSIONS

Older adults with MM have a greater prevalence of falls than matched controls. Self-reported fatigue, depression, and poorer general health are associated with greater odds of falls.

The effect of prolonged level and uphill walking on the postural control of older adults

Prolonged walking could alter postural control leading to an increased risk of falls in older adults. The aim of this study was to determine the effect of level and uphill prolonged walking on the postural control of older adults. Sixteen participants (64 ± 5 years) attended 3 visits. Postural control was assessed during quiet standing and the limits of stability immediately pre, post and post 15 min rest a period of 30 min walking on level and uphill (5.25%) gradients on separate visits. Each 30 min walk was divided into 3 10 min blocks, the limits of stability were measured between each block. Postural sway elliptical area (PRE: 1.38 ± 0.22 cm², POST: 2.35 ± 0.50 cm², p = .01), medio-lateral (PRE: 1.33 ± 0.03, POST: 1.40 ± 0.03, p = .01) and anterio-posterior detrended fluctuation analysis alpha exponent (PRE: 1.43 ± 0.02, POST: 1.46 ± 0.02, p = .04) increased following walking. Medio-lateral alpha exponent decreased between post and post 15 min' rest (POST: 1.40 ± 0.03, POST15: 1.36 ± 0.03, p = .03). Forward limits of stability decreased between the second walking interval and post 15 min' rest (Interval 2: 28.1 ± 1.6%, POST15: 25.6 ± 1.6%, p = .01) and left limits of stability increased from pre-post 15 min' rest (PRE: 27.7 ± 1.2%, POST15: 29.4 ± 1.1%, p = .01). The neuromuscular alterations caused by prolonged walking decreased the anti-persistence of postural sway and altered the limits of stability in older adults. However, 15 min' rest was insufficient to return postural control to pre-exercise levels.