Walking energetics, fatigability, and fatigue in older adults: the study of energy and aging pilot

Assessment of fatigue and its impact in chronic liver disease

Patient-reported outcomes (PROs), such as health-related quality of life (HRQL), are important outcome measures for patients with chronic liver diseases (CLDs). Presence of cirrhosis and advanced liver disease have been associated with worsened HRQL and fatigue. On the other hand, some patients with earlier stages of CLD also experience fatigue, causing PRO impairment. Treatment for some CLDs may improve HRQL and, sometimes, levels of fatigue. We aimed to provide an in-depth expert review of concepts related to fatigue and HRQL in patients with primary biliary cholangitis, hepatitis C virus and MASLD (metabolic dysfunction-associated steatotic liver disease). A panel of experts in fatigue and CLD reviewed and discussed the literature and collaborated to provide this expert review of fatigue in CLD. Herein, we review and report on the complexity of fatigue, highlighting that it is comprised of peripheral (neuromuscular failure, often in conjunction with submaximal cardiorespiratory function) and central (central nervous system dysfunction) causes. Fatigue and HRQL are measured using validated self-report instruments. Additionally, fatigue can be measured through objective tests (e.g. grip strength). Fatigue has deleterious effects on HRQL and one's ability to be physically active and socially engaged but does not always correlate with CLD severity. Treatments for hepatitis C virus and MASLD can improve levels of fatigue and HRQL, but current treatments for primary biliary cholangitis do not seem to affect levels of fatigue. We conclude that obtaining PRO data, including on HRQL and fatigue, is essential for determining the comprehensive burden of CLD and its potential treatments.

Perceived Fatigability, Fatigue, and Mortality in Mid-to-Late Life in the Baltimore Longitudinal Study of Aging

INTRODUCTION/PURPOSE

Fatigue is an established prognostic indicator of mortality risk. It remains unknown whether fatigability anchored to a physical task is a more sensitive prognostic indicator and whether sensitivity differs by prevalent chronic conditions.

METHODS

A total of 1076 physically well-functioning participants 50 yr or older in the Baltimore Longitudinal Study of Aging self-reported fatigue (unusual tiredness or low energy) and had perceived fatigability assessed after a standardized treadmill walk. All-cause mortality was ascertained by proxy contact and National Death Index linkage. Cox proportional hazards models estimated associations of perceived fatigability and fatigue with all-cause mortality, adjusting for demographic and clinical covariates. Interactions by chronic conditions were also examined.

RESULTS

Each 1 SD higher in perceived fatigability, unusual tiredness, or low energy was associated with a higher relative hazard of all-cause mortality after covariate adjustment (fatigability: hazard ratio (HR), 1.18 (95% confidence interval (CI), 1.03-1.36); unusual tiredness: HR, 1.25 (95% CI, 1.08-1.44); low energy: HR, 1.27 (95% CI, 1.10-1.46)). Models had similar discrimination ( P > 0.14 for all). Perceived fatigability was associated with mortality risk among participants free of arthritis or osteoarthritis who otherwise appeared healthy (no arthritis: HR, 1.45 (95% CI, 1.15-1.84); arthritis: HR, 1.09 (95% CI, 0.92-1.30); P -interaction = 0.031). Unusual tiredness was associated with mortality among those with a history of diabetes (no diabetes: HR, 1.16 (95% CI, 0.97-1.38); diabetes: HR, 1.65 (95% CI, 1.22-2.23); P -interaction = 0.045) or pulmonary disease (no pulmonary disease: HR, 1.22 (95% CI, 1.05-1.43); pulmonary disease: HR, 2.15 (95% CI, 1.15-4.03); P -interaction = 0.034).

CONCLUSIONS

Higher perceived fatigability and fatigue symptoms were similarly associated with higher all-cause mortality, but utility differed by chronic condition. Perceived fatigability might be useful for health screening and long-term mortality risk assessment for well-functioning adults. Alternatively, self-reported fatigue seems more disease-specific with regard to mortality risk.

Mediating effects of depression on sleep disturbance and frailty in older adult type 2 diabetes patients in the community

Introduction

With the progressive aging of the population, frailty is now a significant challenge in geriatrics research. A growing amount of evidence suggests that sleep disturbance and depression have independent effects on frailty, although the underlying mechanisms are not yet clear. This study aimed to investigate the mediating role of depression in the relationship between sleep disturbance and frailty in older adult patients with type 2 diabetes (T2DM) in the community.

Method

Purposive sampling was used to collect face-to-face data from 342 community-dwelling T2DM patients in Chengdu, Sichuan Province, China, between February and May 2023. The Pittsburgh Sleep Quality Index (PSQI) scale was used to evaluate sleep quality, the Simple Geriatric Depression Scale (GDS-15) was used to evaluate depressive symptoms, and the FRAIL Scale (FRAIL) was used to evaluate frailty. Linear regression equation and bootstrap self-sampling were used to verify the mediating role of depressive symptoms in sleep disturbance and frailty.

Result

The study found that sleep disturbance had a direct positive effect with frailty [β = 0.040, 95% CI: (0.013, 0.069)]. Additionally, depression had a direct positive effect on frailty [β = 0.130, 95% CI: (0.087, 0.173)], and depression was found to partially mediate the relationship between sleep disturbance and frailty.

Conclusion

Poor sleep quality and frailty are common in patients with T2DM. To reduce the frailty of older adult T2DM patients, all levels of society (government, medical institutions, and communities) must pay more attention to mental health. A variety of interventions should be considered to improve sleep quality and depression, which in turn may prevent or control frailty.

Impact of balance on the energetic cost of walking and gait speed

BACKGROUND

Examine the relationship between balance test performance and the energetic cost of walking (ECW) and gait speed.

METHODS

Cross-sectional and longitudinal analyses of data from the Baltimore Longitudinal Study of Aging. Men (48%) and women aged 60-96 years enrolled in the BLSA between 2007 and 2020 (n = 1132). Balance was assessed using narrow walk (NW) and progressive standing balance tests (SB). ECW measured during 2.5-min usual paced walk while participants wore a portable indirect calorimeter. Gait speed assessed over 6-m. Each test parameterized using validated methods. Statistical analysis to compare balance measures to ECW, and gait speed used generalized logistic regression models and adjustments for age, sex, race, height, weight, and comorbidities.

RESULTS

Cross-sectionally, mean ECW was higher and gait speed slower in persons who failed the NW than those who passed (0.189 vs. 0.164 mL/kg/m, p < 0.0001 and 0.96 vs. 1.15 m/s, p < 0.0001, respectively). Mean ECW was increasingly higher and gait speed slower over three progressively challenging SB tests (0.207 vs. 0.171 vs. 0.164 mL/kg/m, p < 0.0001 and 0.95 vs. 1.05 vs. 1.15 m/s, p < 0.0001). Over an average 2.4 years, those who declined in SB and NW had a higher ECW and slower gait speed than persons who maintained performance (SB: 0.18 vs. 0.160 mL/kg/m, p = 0.0003, and 1.00 vs. 1.13 m/s, p = <0.001; NW: 0.175 vs. 0.160 mL/kg/m, p = 0.002, and 1.04 vs. 1.14 m/s, p = 0.001). Persons who improved had lower ECW and faster gait speed than those who failed at both visits (SB: 0.169 vs. 0.240 mL/kg/m, p = 0.0002, and 0.99 vs. 0.94 m/s, p = 0.67, NW: 0.163 vs. 0.195 mL/kg/m, p = 0.0005, and 1.10 vs. 0.92 m/s, p < 0.001).

CONCLUSION

Instability contributes to higher ECW and slower gait speed which suggests that rehabilitation efforts to improve balance may help maintain function further into older adulthood and delay mobility limitation.

Cardiopulmonary Exercise Testing in a Prospective Multicenter Cohort of Older Adults: The Study of Muscle, Mobility and Aging (SOMMA)

BACKGROUND

Cardiorespiratory fitness (CRF) measured by peak oxygen consumption (VO2peak) declines with aging and correlates with mortality and morbidity. Cardiopulmonary Exercise Testing (CPET) has long been the criterion method to assess CRF, but its feasibility, efficacy and reliability in older adults is unclear. The large, multicenter Study of Muscle, Mobility and Aging (SOMMA) employed CPET to evaluate the mechanisms underlying declines in mobility with aging among community-dwelling older adults. Our primary objective was to design and implement a CPET protocol in older adults that was dependable, safe, scientifically valuable, and methodologically reliable.

METHODS

CPET was performed using treadmill exercise in 875 adults ≥70 years. A composite protocol included a symptom-limited peak exercise phase and two submaximal phases to assess cardiopulmonary ventilatory indices during 1) participants' preferred walking speed and 2) at slow walking speed of 1.5 mph (0.67 m/s). An adjudication process was in place to review tests for validity if they met any prespecified criteria (VO2peak <12.0 ml/kg/min; maximum heart rate (HR) <100 bpm; respiratory exchange ratio (RER) <1.05 and a rating of perceived exertion <15). A repeat test was performed in a subset (N=30) to assess reproducibility.

RESULTS

CPET was safe and well tolerated, with 95.8% of participants able to complete the VO2peak phase of the protocol. Only 56 (6.4%) participants had a risk alert during any phase of testing and only two adverse events occurred during the peak phase: a fall and atrial fibrillation. The average ± standard deviation for VO2peak was 20.2 ± 4.8 mL/kg/min, peak HR 142 ± 18 bpm, and peak RER 1.14 ± 0.09. VO2peak and RER were slightly higher in men than women. Adjudication was indicated in 47 participants; 20 were evaluated as valid, 27 as invalid (18 had a data collection error, 9 did not reach VO2peak). Reproducibility of VO2peak was high (intraclass correlation coefficient=0.97).

CONCLUSIONS

CPET was feasible, effective and safe for community-dwelling older adults, many of whom had multimorbidity and frailty. These data support a broader implementation of CPET to provide important insight into the role of CRF and its underlying determinants in aging and age-related conditions and diseases.

Clinical Perspective

What Is New?: Performing cardiopulmonary exercise testing in a community dwelling older adult with multimorbidities or frailty is feasible and exceptionally safe under highly trained exercise physiologists and physician supervision.Reproducibility of VO2peak among community-dwelling older adults with significant clinical complexity was high (intraclass correlation coefficient=0.97).The VO2peak observed was comparable to established normative data for older adults, and adds merit to the limited data collected on VO2peak norms in older adults.What Are the Clinical Implications?: Ventilatory gas collection during clinical cardiac stress testing may be valuable to plan of care in routine management of older adults due to the important role of aerobic fitness on morbidity and mortality.Cardiopulmonary exercise testing can provide insight into the role of cardiorespiratory fitness and its underlying determinants in aging and age-related conditions and diseases.

Muscle Endurance and Self-Perceived Fatigue Predict Decline in Gait Speed and Activities of Daily Living After 1-Year Follow-Up: Results From the BUTTERFLY Study

BACKGROUND

Fatigue might influence the losses in activities of daily living (ADL). When fatigue parameters are present before the experience of losses in ADL and gait speed, they can be used as early warning signals. This study aimed to explore the predictive value of muscle endurance and fatigue on changes in ADL and gait speed in community-dwelling older adults aged 80 and older.

METHODS

Three hundred twenty four community-dwelling older adults aged 80 and older of the BUTTERFLY study were assessed after 1 year for muscle endurance, self-perceived fatigue, ADL, and gait speed. Exploratory factor analysis (EFA) was performed to explore, whether there is an underlying arrangement of the fatigue parameters. Mediating logistic regression analyses were used to investigate whether muscle endurance mediated by self-perceived fatigue predicts the decline in gait speed and ADL after 1-year follow-up.

RESULTS

EFA indicated a 2-factor model (muscle endurance factor and self-perceived fatigue factor) and had a moderate fit (X2: 374.81, df: 2, comparative fit index; 0.710, Tucker-Lewis index (TLI): 0.961, root mean square error of approximation [90%]: 0.048 [0.00-0.90]). Muscle endurance mediated by self-perceived fatigue had an indirect effect on the prediction of decline in Basal-ADL (-0.27), Instrumental-ADL (-0.25), and gait speed (-0.28) after 1-year follow-up.

CONCLUSION

This study showed that low muscle endurance combined with high self-perceived fatigue can predict changes in ADL after 1-year follow-up. These parameters might be very suitable for use in evaluating intrinsic capacity and can help to reduce the limitations in clinical usage of the vitality domain in the framework of intrinsic capacity.

Dual Roles of Cardiorespiratory Fitness and Fatigability in the Life-Space Mobility of Older Adults: The Study of Muscle, Mobility and Aging (SOMMA)

BACKGROUND

Cardiorespiratory fitness and perceived fatigability are interrelated components of physical capacity that may jointly influence movement within one's living environment (life-space mobility). We examined whether fitness and fatigability were associated with life-space mobility in community-dwelling older adults, and whether the association of fitness with life-space varied by the level of perceived fatigability.

METHODS

Participants were from the Study of Muscle, Mobility and Aging (SOMMA) baseline cohort (N = 775, mean age 76.1 years). Life Space Assessment scores incorporated level, frequency, and assistance used (personal, devices) for life-space mobility. Fitness was measured as VO2peak from symptom-limited treadmill testing. Fatigability cut-points included: (i) Borg Rating of Perceived Exertion (RPE) ≥ 10 after a fixed-speed (1.5 mph) treadmill test, (ii) the Pittsburgh Fatigability Scale (PFS) Physical ≥ 15, and (iii) PFS Mental ≥ 13. The total count of cut-points was used as a composite fatigability measure (range: 0-3). Linear regressions were adjusted for demographic, lifestyle, and health confounders.

RESULTS

Better fitness was associated with greater life-space, but the association plateaued at higher fitness levels (VO2peak > 18). Life-space was significantly lower for individuals meeting ≥2 fatigability criteria (vs none), attributable mainly to more severe physical, but not mental, fatigability. In moderation analyses, the fitness-life-space association was significant only for those with RPE ≥ 10 but did not differ by PFS.

CONCLUSION

Fitness below a critically low threshold was associated with limited life-space mobility, suggesting that certain older individuals may need to operate close to their maximum aerobic capacity to traverse daily environments; these associations were driven by those with more severe physical fatigability.

Quasi-passive lower limbs exosuit: an in-depth assessment of fatigue, kinematic and muscular patterns while comparing assistive strategies on an expert subject's gait analysis

Wearable robots are becoming a valuable solution that helps injured, and elderly people regain mobility and improve clinical outcomes by speeding up the rehabilitation process. The XoSoft exosuit identified several benefits, including improvement of assistance, usability, and acceptance with a soft, modular, bio-mimetic, and quasi-passive exoskeleton. This study compares two assistive configurations: (i) a bilateral hip flexion (HA, hips-assistance) and (ii) a bilateral hip flexion combined with ankle plantarflexion (HAA, hips-ankles-assistance) with the main goal of evaluating compensatory actions and synergetic effects generated by the human- exoskeleton interaction. A complete description of this complex interaction scenario with this actuated exosuit is evaluated during a treadmill walking task, using several indices to quantify the human-robot interaction in terms of muscular activation and fatigue, metabolic expenditure, and kinematic motion patterns. Evidence shows that the HAA biomimetic controller is synergetic with the musculature and performs better concerning the other control strategy. The experimentation demonstrated a metabolic expenditure reduction of 8% of Metabolic Equivalent of Task (MET), effective assistance of the muscular activation of 12.5%, a decrease of the muscular fatigue of 0.6% of the mean frequency, and a significant reduction of the compensatory actions, as discussed in this work. Compensatory effects are present in both assistive configurations, but the HAA modality provides a 47% reduction of compensatory effects when considering muscle activation.

Efficacy and tolerability of an endogenous metabolic modulator (AXA1125) in fatigue-predominant long COVID: a single-centre, double-blind, randomised controlled phase 2a pilot study

Background

'Long COVID' describes persistent symptoms, commonly fatigue, lasting beyond 12 weeks following SARS-CoV-2 infection. Potential causes include reduced mitochondrial function and cellular bioenergetics. AXA1125 has previously increased β-oxidation and improved bioenergetics in preclinical models along with certain clinical conditions, and therefore may reduce fatigue associated with Long COVID. We aimed to assess the efficacy, safety and tolerability of AXA1125 in Long COVID.

Methods

Patients with fatigue-dominant Long COVID were recruited in this single-centre, double-blind, randomised controlled phase 2a pilot study completed in the UK. Patients were randomly assigned (1:1) using an Interactive Response Technology to receive either AXA1125 or matching placebo in a clinical-based setting. Each dose (33.9 g) of AXA1125 or placebo was administered orally in a liquid suspension twice daily for four weeks with a two-week follow-up period. The primary endpoint was the mean change from baseline to day 28 in the phosphocreatine (PCr) recovery rate following moderate exercise, assessed by ³¹P-magnetic resonance spectroscopy (MRS). All patients were included in the intention to treat analysis. This trial was registered at ClinicalTrials.gov, NCT05152849.

Findings

Between December 15th 2021, and May 23th 2022, 60 participants were screened, and 41 participants were randomised and included in the final analysis. Changes in skeletal muscle phosphocreatine recovery time constant (τ_PCr) and 6-min walk test (6MWT) did not significantly differ between treatment (n = 21) and placebo group (n = 20). However, treatment with AXA1125 was associated with significantly reduced day 28 Chalder Fatigue Questionnaire [CFQ-11] fatigue score when compared with placebo (least squares mean difference [LSMD] -4.30, 95% confidence interval (95% CI) -7.14, -1.47; P = 0.0039). Eleven (52.4%, AXA1125) and four (20.0%, placebo) patients reported treatment-emergent adverse events; none were serious or led to treatment discontinuation.

Interpretation

Although treatment with AXA1125 did not improve the primary endpoint (τ_PCr-measure of mitochondrial respiration), when compared to placebo, there were significant improvements in fatigue-based symptoms among patients living with Long COVID following a four-week treatment period. Further multicentre studies are needed to validate our findings in a larger cohort of patients with fatigue-dominant Long COVID.

Funding

Axcella Therapeutics.

Faster triceps surae muscle cyclic contractions alter muscle activity and whole body metabolic rate

Hundred years ago, Fenn demonstrated that when a muscle shortens faster, its energy liberation increases. Fenn's results were the first of many that led to the general understanding that isometric muscle contractions are energetically cheaper than concentric contractions. However, this evidence is still primarily based on single fiber or isolated (ex vivo) muscle studies and it remains unknown whether this translates to whole body metabolic rate. In this study, we specifically changed the contraction velocity of the ankle plantar flexors and quantified the effects on triceps surae muscle activity and whole body metabolic rate during cyclic plantar flexion (PF) contractions. Fifteen participants performed submaximal ankle plantar flexions (∼1/3 s activation and ∼2/3 s relaxation) on a dynamometer at three different ankle angular velocities: isometric (10° PF), isokinetic at 30°/s (5-15° PF), and isokinetic at 60°/s (0-20° PF) while target torque (25% MVC) and cycle frequency were kept constant. In addition, to directly determine the effect of ankle angular velocity on muscle kinematics we collected gastrocnemius medialis muscle fascicle ultrasound data. As expected, increasing ankle angular velocity increased gastrocnemius medialis muscle fascicle contraction velocity and positive mechanical work (P < 0.01), increased mean and peak triceps surae muscle activity (P < 0.01), and considerably increased net whole body metabolic rate (P < 0.01). Interestingly, the increase in triceps surae muscle activity with fast ankle angular velocities was most pronounced in the gastrocnemius lateralis (P < 0.05). Overall, our results support the original findings from Fenn in 1923 and we demonstrated that greater triceps surae muscle contraction velocities translate to increased whole body metabolic rate.NEW & NOTEWORTHY Single muscle fiber studies or research on isolated (ex vivo) muscles demonstrated that faster concentric muscle contractions yield increased energy consumption. Here we translated this knowledge to muscle activation and whole body metabolic rate. Increasing ankle angular velocity increased triceps surae contraction velocity and mechanical work, increasing triceps surae muscle activity and substantially elevating whole body metabolic rate. Additionally, we demonstrated that triceps surae muscle activation strategy depends on the mechanical demands of the task.

Outdoor gyms and physical function: A cross-sectional comparative study between active and sedentary older adults

Outdoor gyms (OG) are public places designed for physical activity, especially for older adults. This is a cross-sectional study that aimed to compare morphofunctional characteristics of sedentary and active older adults regarding OG. The participants consisted of 194 older people divided into three groups: sedentary (n = 76, mean age = 70.5 ± 6.4 years, 38.7% male); OG + walking (n = 86; mean age = 69 ± 6.1 years; male 50.6%); and OG (n = 32; mean age = 70.3 ± 8.3 years; male 56.3%). Socioeconomic and morphofunctional characteristics, anthropometric measurements, body composition, and functional tests were collected. For comparison among groups ANOVA, for categorical variables the chi-square test or Fisher's exact test, and to verify factors related to gait speed logistic regression were used. We found that sedentary older adults had lower educational level and lower prevalence of polypharmacy. OG + walking participants had lower waist circumference and fat percentage, and better gait speed. Older people in the OG + walking were less likely to show gait difficulty (i.e., <1.0 m/s) in reference to the sedentary group. In addition, strength and better performance on the Timed Up and Go were also associated with gait speed >1 m/s. It is understood that the higher volume of physical activity performed by OG + walking may be one of the reasons why they obtained better indicators in health aspects. The findings, especially regarding the characterization of profiles of older adults who use OG, leads to the definition of public policies aimed at the real needs of this public.

Developing and pilot testing a frailty-focused education and communication training workshop

Objective

To describe development and pilot testing of a multi-modal frailty-focused education and communication training workshop for health care clinicians.

Methods

Pilot testing was conducted via two workshops (#1:face-to-face [2019], #2:virtual [2020]). Participants: convenience sample of clinicians and students who volunteered. Workshop #1 included registered nurses working in an acute care and one medical student (N=14); #2: nursing students enrolled in an APRN program. Design: Pre/post observational study. Data analysis: descriptive statistics, paired t-tests and Wilcoxon rank test.

Results

Statistically significant increases in frailty knowledge (#1: p = 0.02, d = 0.44; #2: p = 0.006, d = 0.55) and self-reported competency with older adult interactions (#1: p < 0.001, d = 0.62; #2: p = 0.001, d = 0.63) were reported for both workshops. Post course evaluations of the workshop were positive, with scores ranging from 3.5-3.9 (range: 0-4) for increased understanding of the concept of frailty, communication to support health-related behavior, and best practice empathic communication skills.

Conclusion

The FCOM workshop was successful. Participants gained knowledge and skills for use in working with older adults across the aging continuum from non-frail to frail.

Innovation

Our FCOM training workshop expands prior communication training on shared decision-making with frail individuals to a broader population of all older adults.

Intrinsic motoneuron excitability is reduced in soleus and tibialis anterior of older adults

Age-related deterioration within both motoneuron and monoaminergic systems should theoretically reduce neuromodulation by weakening motoneuronal persistent inward current (PIC) amplitude. However, this assumption remains untested. Surface electromyographic signals were collected using two 32-channel electrode matrices placed on soleus and tibialis anterior of 25 older adults (70 ± 4 years) and 17 young adults (29 ± 5 years) to investigate motor unit discharge behaviors. Participants performed triangular-shaped plantar and dorsiflexion contractions to 20% of maximum torque at a rise-decline rate of 2%/s of each participant's maximal torque. Pairwise and composite paired-motor unit analyses were adopted to calculate delta frequency (ΔF), which has been used to differentiate between the effects of synaptic excitation and intrinsic motoneuronal properties and is assumed to be proportional to PIC amplitude. Soleus and tibialis anterior motor units in older adults had lower ΔFs calculated with either the pairwise [-0.99 and -1.46 pps; -35.4 and -33.5%, respectively] or composite (-1.18 and -2.28 pps; -32.1 and -45.2%, respectively) methods. Their motor units also had lower peak discharge rates (-2.14 and -2.03 pps; -19.7 and -13.9%, respectively) and recruitment thresholds (-1.50 and -2.06% of maximum, respectively) than young adults. These results demonstrate reduced intrinsic motoneuron excitability during low-force contractions in older adults, likely mediated by decreases in the amplitude of persistent inward currents. Our findings might be explained by deterioration in the motoneuron or monoaminergic systems and could contribute to the decline in motor function during aging; these assumptions should be explicitly tested in future investigations.

Traits and treadmills: Association between personality and perceived fatigability in well-functioning community-dwelling older adults

Physical fatigability, or susceptibility to physical fatigue, is strongly associated with aging, disease, and disability. Over the lifecourse, personality traits are also connected to numerous age-related vulnerabilities and resistance-yet, their longitudinal association with fatigability remains unknown. Well-functioning community-dwelling volunteers aged ≥50 (N = 995) from the Baltimore Longitudinal Study of Aging (BLSA) were assessed over an average of 2 years on personality traits (NEO-PI-R; openness, conscientiousness, extraversion, agreeableness, and neuroticism) and perceived fatigability [Borg Rating of Perceived Exertion (RPE) after a 5-min slow treadmill walk; 6 (low) to 20 (high) exertion]. Linear and multinomial logistic regression models examined cross-sectional associations [treating fatigability continuously and by RPE category: low (6-7), intermediate (8-9), and high (10+)]. Generalized estimating equations (GEE) tested longitudinal associations. All models were adjusted for demographics and comorbid conditions. In cross-sectional models, openness, β = -.09 RPE (SE =.03); p < .01, conscientiousness, β = -.07 (.03); p < .05, and extraversion, β = -.10 (.03); p < .01, were negatively associated with fatigability. In parallel, lower openness, OR: .98, 95% CI [.96-1.00], conscientiousness, OR: .98, 95% CI [.96-1.00], and extraversion, OR: .97, 95% CI [.95-.99], corresponded with higher odds of having high versus low fatigability. In longitudinal models (mean follow-up time 2 ± 2 years), openness, conscientiousness, and extraversion associations remained significant and did not change over time (Trait × Year p values > .34). Together, findings suggest that personality plays a role in the perceived tolerance of fatigue in well-functioning older adults. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Ratings of Perceived Exertion During Walking: Predicting Major Mobility Disability and Effect of Structured Physical Activity in Mobility-Limited Older Adults

BACKGROUND

This study evaluated the association between ratings of perceived exertion (RPE) of walking and major mobility disability (MMD), as well as their transitions in response to a physical activity (PA) compared to a health education (HE) program.

METHODS

Older adults (n = 1633) who were at risk for mobility impairment were randomized to structured PA or HE programs. During a 400 m walk, participants rated exertion as "light" or "hard." An MMD event was defined as the inability to walk 400 m. MMD events and RPE values were assessed every 6 months for an average of 2.6 years.

RESULTS

Participants rating their exertion as "hard" had a nearly threefold higher risk of MMD compared with those rating their exertion as "light" (HR: 2.61, 95% CI: 2.19-3.11). The association was held after adjusting for disease conditions, depression, cognitive function, and walking speed (HR: 2.24, 95% CI: 1.87-2.69). The PA group was 25% more likely to transition from "light" to "hard" RPE than the HE group (HR: 1.25, 95% CI: 1.05-1.49). Additionally, the PA group was 27% (HR: 0.73, 95% CI: 0.55 - 0.97) less likely to transition from a "hard" RPE to inability to walk 400 m and was more likely to recover their ability to walk 400 m by transitioning to a "hard" RPE (HR: 2.10, 95% CI: 1.39-3.17) than the HE group.

CONCLUSIONS

Older adults rating "hard" effort during a standardized walk test were at increased risk of subsequent MMD. A structured PA program enabled walking recovery, but was more likely to increase transition from "light" to "hard" effort, which may reflect the greater capacity to perform the test.

Effects of Short- and Long-Term Aerobic-Strength Training and Determinants of Walking Speed in the Elderly

BACKGROUND/AIMS

Walking speed (WS) is an objective measure of physical capacity and a modifiable risk factor of morbidity and mortality in the elderly. In this study, we (i) determined effects of 3-month supervised aerobic-strength training on WS, muscle strength, and habitual physical activity; (ii) evaluated capacity of long-term (21 months) training to sustain higher WS; and (iii) identified determinants of WS in the elderly.

METHODS

Volunteers (F 48/M 14, 68.4 ± 7.1 years) completed either 3-month aerobic-strength (3 × 1 h/week, n = 48) or stretching (active control, n = 14) intervention (study A). Thirty-one individuals (F 24/M 7) from study A continued in supervised aerobic-strength training (2 × 1 h/week, 21 months) and 6 (F 5/M 1) became nonexercising controls.

RESULTS

Three-month aerobic-strength training increased preferred and maximal WS (10-m walk test, p < 0.01), muscle strength (p < 0.01) and torque (p < 0.01) at knee extension, and 24-h habitual physical activity (p < 0.001), while stretching increased only preferred WS (p < 0.03). Effect of training on maximal WS was most prominent in individuals with baseline WS between 1.85 and 2.30 m·s-1. Maximal WS measured before intervention correlated negatively with age (r = -0.339, p = 0.007), but this correlation was weakened by the intervention (r = -0.238, p = 0.06). WS progressively increased within the first 9 months of aerobic-strength training (p < 0.001) and remained elevated during 21-month intervention (p < 0.01). Cerebellar gray matter volume (MRI) was positively associated with maximal (r = 0.54; p < 0.0001) but not preferred WS and explained >26% of its variability, while age had only minor effect.

CONCLUSIONS

Supervised aerobic-strength training increased WS, strength, and dynamics of voluntary knee extension as well as habitual physical activity in older individuals. Favorable changes in WS were sustainable over the 21-month period by a lower dose of aerobic-strength training. Training effects on WS were not limited by age, and cerebellar cortex volume was the key determinant of WS.

Longitudinal Association Between Energy Regulation and Fatigability in Mid-to-Late Life

BACKGROUND

Deficits in energy production and utilization have been linked to higher fatigue and functional decline with aging. Lesser known is whether individuals with a combination of low peak energy capacity and high energy costs for mobility (eg, impaired energy regulation) are more likely to experience the onset and progression of high fatigability with aging.

METHODS

Participants in the Baltimore Longitudinal Study of Aging (n = 651, 49.0% male, mean age 71.9, range 50-94) with ≥2 visits who completed fatigability (Borg rating of perceived exertion [RPE] after a 5-minute 1.5 mph treadmill walk), slow walking energy expenditure (VO2 mL/kg/min), and peak walking energy expenditure (VO2 mL/kg/min), testing between 2007 and 2018. The longitudinal association between each measure of energy expenditure, a ratio of energy cost-to-capacity, and perceived fatigability was modeled using mixed effects models adjusted for age, body composition, and comorbidities. Time to higher perceived fatigability (RPE ≥ 10) was modeled using Cox proportional hazards models.

RESULTS

In continuous analyses, higher slow walking energy expenditure (p < .05) and a higher cost ratio (p ≤ .001) were associated with greater perceived fatigability over time. Cox proportional hazards models using tertiles of the cost ratio suggest that, compared to those in the lowest tertile, those in the middle and highest tertiles had 1.89 (95% confidence interval [CI]: 1.57-5.16) and 2.85 (95% CI: 1.05-3.40) times greater risk of developing higher fatigability, respectively.

CONCLUSION

Findings suggest that strategies to prevent fatigability should consider methods to improve energy regulation by targeting both the independent and combined effects of declining peak capacity and rising energy costs for mobility with aging.

A Moderated-Mediation Model of the Relationship between Dietary Satisfaction and Fatigue in Older Adults with Diabetes: The Role of Meal Planning and Depressive Symptoms

Little research has examined the pathways between psychological factors and fatigue in older adults with diabetes. This study explored the pathways between diet-related quality of life and depressive symptoms in predicting fatigue using a moderated-mediation model. A convenience sample of adults ≥65 years (n = 127) with diabetes completed a cross-sectional survey including measures of fatigue severity, diet-related quality of life, and depressive symptoms, and a moderated-mediation analysis assessed the relationships between them. Diet satisfaction was negatively related to fatigue, which was mediated by depressive symptoms. In the moderated-mediation model, diet satisfaction had a conditional effect on fatigue through the mediating effect of depressive symptoms, moderated by meal planning difficulty. At higher levels of perceived meal planning difficulty, lower diet satisfaction was indirectly associated with higher fatigue through depressive symptoms, but this pathway was non-significant at lower levels. Findings suggest that supportive care for diet therapy might improve psychological outcomes in older adults with diabetes, especially for those having difficulties with daily dietary practice. Meal planning difficulties in the dietary management of diabetes accompanied by low diet satisfaction may lead to negative psychological outcomes. Monitoring satisfaction and burdens associated with dietary practices could improve fatigue in this population.

Use of Functional Linear Models to Detect Associations between Characteristics of Walking and Continuous Responses Using Accelerometry Data

Various methods exist to measure physical activity. Subjective methods, such as diaries and surveys, are relatively inexpensive ways of measuring one’s physical activity; however, they are prone to measurement error and bias due to self-reporting. Wearable accelerometers offer a non-invasive and objective measure of one’s physical activity and are now widely used in observational studies. Accelerometers record high frequency data and each produce an unlabeled time series at the sub-second level. An important activity to identify from the data collected is walking, since it is often the only form of activity for certain populations. Currently, most methods use an activity summary which ignores the nuances of walking data. We propose methodology to model specific continuous responses with a functional linear model utilizing spectra obtained from the local fast Fourier transform (FFT) of walking as a predictor. Utilizing prior knowledge of the mechanics of walking, we incorporate this as additional information for the structure of our transformed walking spectra. The methods were applied to the in-the-laboratory data obtained from the Developmental Epidemiologic Cohort Study (DECOS).

Epidemiology of Perceived Physical Fatigability in Older Adults: The Long Life Family Study

BACKGROUND

Fatigability is a construct that measures whole-body tiredness anchored to activities of a fixed intensity and duration; little is known about its epidemiology and heritability.

METHODS

Two generations of family members enriched for exceptional longevity and their spouses were enrolled (2006-2009) in the Long Life Family Study (LLFS). At Visit 2 (2014-2017, N = 2,355) perceived physical fatigability was measured using the 10-item self-administered Pittsburgh Fatigability Scale (PFS), along with demographic, medical, behavioral, physical, and cognitive risk factors.

RESULTS

Residual genetic heritability of fatigability was 0.263 (p = 6.6 × 10-9) after adjustment for age, sex, and field center. PFS physical scores (mean ± SD) and higher physical fatigability prevalence (% PFS ≥ 15) were greater with each age strata: 60-69 (n = 1,009, 11.0 ± 7.6, 28%), 70-79 (n = 847, 12.5 ± 8.1, 37%), 80-89 (n = 253, 19.3 ± 9.9, 65.2%), and 90-108 (n = 266, 28.6 ± 9.8, 89.5%), p < .0001, adjusted for sex, field center, and family relatedness. Women had a higher prevalence of perceived physical fatigability compared to men, with the largest difference in the 80-89 age strata, 74.8% versus 53.5%, p < .0001. Those with greater body mass index, worse physical and cognitive function, and lower physical activity had significantly higher perceived physical fatigability.

CONCLUSIONS

Perceived physical fatigability is highly prevalent in older adults and strongly associated with age. The family design of LLFS allowed us to estimate the genetic heritability of perceived physical fatigability. Identifying risk factors associated with higher perceived physical fatigability can inform the development of targeted interventions for those most at risk, including older women, older adults with depression, and those who are less physically active.

Body Mass Index, Physical Activity Habits and Physical Function Contribute to Fatigue in the Rest Home Residents

BACKGROUNDS

Fatigue is a common complaint in older adults living in rest homes. The aim of this study was to investigate the factors associated with fatigue among older adults living in a rest home.

METHODS

This cross-sectional study was carried out with a total of 92 older adults. Fatigue was evaluated by the Fatigue Severity Scale (FSS). The sociodemographic characteristics, quadriceps and handgrip strength, functional capacity and physical function were assessed using a structured questionnaire, digital dynamometers, 6-minute walking test and Short Physical Performance Battery, respectively.

RESULTS

The prevalence of fatigue was 67.4%. FSS showed significant correlations with age, female gender, body mass index, physical activity habits, quadriceps strength, handgrip strength, functional exercise capacity, and physical function. However, in the regression analysis, only body mass index, physical activity habits and physical function were responsible for 51% of the variance in fatigue among rest home residents. Physical activity habits and physical function were the best predictors of fatigue explaining 47.5% of variance.

CONCLUSION

This study demonstrated that body mass index, physical activity habits and physical function contributed to fatigue in rest home residents. These factors can be used to identify individuals at high risk of fatigue and to attenuate fatigue levels.

Using the NIH symptom science model to understand fatigue and mitochondrial bioenergetics

The symptom of fatigue is prevalent among patients with chronic diseases and conditions such as congestive heart failure and cancer. It has a significant debilitating impact on patients' physical health, quality of life, and well-being. Early detection and appropriate assessment of fatigue is essential for diagnosing, treating, and monitoring disease progression. However, it is often challenging to manage the symptom of fatigue without first investigating the underlying biological mechanisms. In this narrative review, we conceptualize the symptom of fatigue and its relationship with mitochondrial bioenergetics using the National Institute of Health Symptom Science Model (NIH-SSM). In particular, we discuss mental and physical measures to assess fatigue, the importance of adenosine triphosphate (ATP) in cellular and organ functions, and how impaired ATP production contributes to fatigue. Specific methods to measure ATP are described. Recommendations are provided concerning how to integrate biological mechanisms with the symptom of fatigue for future research and clinical practice to help alleviate symptoms and improve patients' quality of life.

Assessing physical performance and physical activity in large population-based aging studies: home-based assessments or visits to the research center?

Background

The current study aims to compare correlations between a range of measures of physical performance and physical activity assessing the same underlying construct in different settings, that is, in a home versus a highly standardized setting of the research center or accelerometer recording. We also evaluated the selective attrition of participants related to these different settings and how selective attrition affects the associations between variables and indicators of health, functioning and overall activity.

Methods

Cross-sectional analyses comprising population-based samples of people aged 75, 80, and 85 years living independently in Jyväskylä, Finland. The AGNES study protocol involved the following phases: 1) phone interview (n = 1886), 2) face-to-face at-home interview (n = 1018), 3) assessments in the research center (n = 910), and 4) accelerometry (n = 496). Phase 2 and 3 included walking and handgrip strength tests, and phase 4 a chest-worn and thigh-worn accelerometer estimating physical activity and assessing posture, respectively, for 3–10 days in free-living conditions.

Results

Older people with poorer health and functioning more likely refrained from subsequent study phases, each requiring more effort or commitment from participants. Paired measures of walking speed (R = 0.69), handgrip strength (R = 0.85), time in physical activity of at least moderate intensity (R = 0.42), and time in upright posture (R = 0.30) assessed in different settings correlated with each other, and they correlated with indicators of health, functioning and overall activity. Associations were robust regardless of limitations in health and functioning, and low overall activity.

Conclusions

Correlational analyses did not clearly reveal one superior setting for assessing physical performance or physical activity. Inclusion of older people with early declines in health, functioning and overall activity in studies on physical performance and physical activity is feasible in terms of study outcomes, but challenging for recruitment.

Fatigue-Related Factors for Community-Dwelling Older Adults with Diabetes: A Theory-Guided Multi-Dimensional Approach Using the Dynamic Biopsychosocial Model

Older adults with diabetes appear more susceptible to fatigue compared to younger adults with diabetes or healthy older adults, since aging and diabetes independently and synergistically influence fatigue. Few studies have investigated fatigue in older adults with diabetes using a multidimensional approach. This study explored the influences of physical, psychological, interpersonal, and contextual factors on diabetes fatigue using a dynamic biopsychosocial model. Face-to-face surveys were administered to community-dwelling older adults with diabetes and included variables across four domains (i.e., physical, psychological, interpersonal, and contextual factors). Univariate analyses and multiple linear regression were used. The mean fatigue score was 3.94 (standard deviation (SD) = 1.81) out of 7, and the prevalence of fatigue was 48.8%. Significant differences in fatigue severity by psychological, interpersonal, and contextual factors were found. Comorbidity and psychological factors were significant predictors of fatigue in the model, explaining 31.9% of the variance. As nearly half the sample experienced moderate or severe fatigue, which was significantly influenced by both comorbidity and psychological factors, including depression, sleep quality, and diet-related psychological characteristics, assessing patients' psychological status may be important. Awareness of fatigue could be incorporated into dietary interventions for older adults with diabetes.

Randomized Controlled Trial of Exercise to Improve Walking Energetics in Older Adults

Background and Objectives

Mobility limitation is common and has been linked to high energetic requirements of daily activities, including walking. The study objective was to determine whether two separate forms of exercise could reduce the energy cost of walking and secondary outcomes related to activity and participation domains among older adults with mobility limitation.

Research Design and Methods

Community-dwelling older adults with self-reported mobility limitation (n = 72) were randomized to 12 weeks of twice-weekly, group-based, instructor-led timing and coordination, aerobic walking, or stretching and relaxation (active control) programs. The primary outcome was the energy cost of walking (mL O₂/kg/m), assessed by a 5-minute treadmill walking test (0.8 m/s). Secondary outcomes were fatigability, physical activity, endurance, physical function, and life-space. Baseline-adjusted ANCOVAs were used to determine mean differences between exercise and control groups at 12 and 24 weeks.

Results

Exercise session attendance was high: 86% for timing and coordination, 81% for aerobic walking, and 90% for stretching and relaxation. At 12 weeks, timing and coordination reduced the mean energy cost of walking by 15% versus stretching and relaxation (p = .008). Among those with high baseline cost, timing and coordination reduced mean energy cost by 20% versus stretching and relaxation (p = .055). Reductions were sustained at 24 weeks. Aerobic walking had no effect on the energy cost of walking at 12 or 24 weeks. At 12 weeks, there was a trend toward faster gait speed (by 0.1 m/s) in timing and coordination versus stretching and relaxation (p = .074). Fatigability, physical activity, endurance, physical function, and life-space did not change with timing and coordination or aerobic walking versus stretching and relaxation at 12 or 24 weeks.

Discussion and Implications

Twelve weeks of timing and coordination, but not aerobic walking, reduced the energy cost of walking among older adults with mobility limitation, particularly among those with high baseline energy cost; reductions in energy cost were sustained following training cessation. Timing and coordination also led to a trend toward faster gait speed.

Validation of the Spanish version of the Pittsburgh Fatigability Scale for older adults

BACKGROUND

The Pittsburgh Fatigability Scale (PFS) is the only validated scale for measuring perceived fatigability in older adults.

AIMS

We validated the PFS Spanish version by assessing convergent validity with respect to several measures of physical performance, physical activity, physical function and disability.

METHODS

A cross-sectional validation study of 79 community-dwelling older adults aged 70 and older from Barcelona, Spain was included. Translation-retrotranslation was performed. Convergent validity was assessed in relation to physical activity and performance measurements, and analyzed with Spearman correlation coefficients, a linear trend test and non-linear regression. We also assessed the discriminant validity of the PFS physical score between participants with different physical activity and performance levels.

RESULTS

Higher PFS physical scores were inversely associated with the Short Physical Performance Battery (r = - 0.5, p < 0.001) and weak to moderately correlated with gait speed (r = 0.38, p = 0.001), and self-reported weekly walking time (r = 0.24, p = 0.035).

CONCLUSION

The PFS is a novel, brief instrument to assess fatigability in Spanish-speaking older adults, with good convergent validity against physical performance measurements. Thus, the PFS can be used in Spanish-speaking populations.

Development and Psychometric Evaluation of a Fatigability Index for Full-Time Wheelchair Users With Spinal Cord Injury

OBJECTIVE

To develop and evaluate psychometrically a self-reported instrument assessing physical fatigability (PF) and mental fatigability (MF) in adults with spinal cord injury (SCI).

DESIGN

Cross-sectional.

SETTING

Peer-support groups at rehabilitation centers, online support groups.

PARTICIPANTS

Adults with SCI (N=464) in the United States.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

The dimensional structure was assessed by confirmatory factor analysis. The relationship between item responses and fatigability was measured with item response theory (graded response model). Reliability was measured with test information functions. Differential item functioning was evaluated with Wald chi-square tests and the weighted area between the curves. Construct validity was assessed using the known groups method.

RESULTS

An 82-item pool was developed from prior qualitative research and consultations with rehabilitation experts. A non-probability sample (N=464) was used to evaluate the psychometric properties of the PF and MF scales. The item pool was reduced to 75 based on factor loadings and R². Both scales are primarily unidimensional, despite moderate multidimensionality. There is good discrimination overall: 18 PF items and 26 MF items have high or very high discrimination power (slopes > 1.35). The measurement precision in the theta range -2.0 to 2.5 is the equivalent of 0.94 reliability for PF and 0.91 for MF. For both measures, F statistics P values were significant at P<.01, and means were higher for those with paraplegia vs quadriplegia, and for those with incomplete paraplegia.

CONCLUSIONS

The Fatigability Index is the first instrument designed to assess physical and mental fatigability in adults with SCI. The index highlights causes of fatigue and areas requiring immediate intervention. Development of short-forms and further research on representative samples are necessary.

Personality and Walking Speed Across Adulthood

Walking speed is one marker of health in adulthood. Although personality may contribute to gait speed, there is limited longitudinal data on this association. Thus, the present study examined whether personality traits are prospectively associated with walking speed among middle aged and older adults. Participants were adults aged from 25 to 100 years old ( N > 15,000) drawn from the Wisconsin Longitudinal Study Graduate and Sibling samples, the Midlife in the United States Survey, the Health and Retirement Study, and the National Health and Aging Trends Survey. Across most samples and in a meta-analysis, lower neuroticism and higher extraversion, conscientiousness, and openness at baseline were prospectively related to faster gait speed. In the HRS, lower neuroticism and higher extraversion, conscientiousness, and openness were related to slower gait speed decline. This study provides robust evidence that walking speed in adulthood reflects, in part, the individual’s personality.

Evaluating Walking Intensity with Hip-Worn Accelerometers in Elders

PURPOSE

Accelerometer activity counts are used to objectively categorize physical activity levels. We examined the association between accelerometer activity counts and metabolic effort in older adults.

METHODS

Forty-five older adults (76.3 ± 5.1 yr) completed a 400-m walk at both a usual and a rapid pace. A portable metabolic unit measured pulmonary gas exchange, whereas a hip-worn accelerometer measured activity counts. Participants were categorized as either a "slow walker" or a "fast walker" based on the threshold of 1.0 m·s during usual-pace walking.

RESULTS

Activity counts during rapid (r = 0.62, P < 0.01) but not usual-pace (r = 0.24, P = 0.11) walking were significantly associated with METs. Slow walkers attained only half the activity counts of fast walkers during each walk condition (P < 0.01), while at the same time achieving between 82% and 90% of their MET level.

CONCLUSION

Accelerometers may misclassify the activity level of functionally impaired older adults with slow walking speed.

Evaluation of fatigability measurement: Integrative review

Fatigability is defined as the extent of fatigue in the context of activity and differs from the term used in exercise literature to describe muscle endurance characteristics. Many fatigability measures are available, but no studies have thoroughly evaluated them for adequate incorporation of fatigability concepts. This integrative review provides an overall assessment of existing fatigability measures and then evaluates each in depth. A database search and hand search produced 14 studies for review. Fatigability measurement took three forms: self-reported fatigability, perceived fatigability (self-reported fatigue following a defined performance test), and performance fatigability (performance deterioration). Of 17 measures identified, validity and/or reliability was reported for six (35.3%), and no measure was used in more than one study. Fatigability measures have been correlated with clinical measures, indicating that fatigability should be measured during routine clinical health screening. Refinement of measures and additional fatigability data collection will improve understanding and treatment of fatigue.

Biological Aging and the Future of Geriatric Psychiatry

Advances in understanding the biological bases of aging have intellectually revitalized the field of geriatric psychiatry and broadened its scope to include promoting successful aging and studying resilience factors in older adults. To describe the process by which this paradigm shift has occurred and illustrate its implications for treatment and research of late-life brain disorders, late-life depression is discussed as a prototype case. Prior phases of geriatric psychiatry research were focused on achieving depressive symptom relief, outlining pharmacokinetic and pharmacodynamic differences between older and younger adults, and identifying moderators of treatment response. Building on this work, current geriatric psychiatry researchers have begun to disentangle the etiologic complexity in late-life depression by focusing on the causative aging-related processes involved, identifying both neurobiological and behavioral intermediates, and finally delineating depression subtypes that are distinguishable by their underlying biology and the treatment approach required. In this review, we discuss several age-related processes that are critical to the development of late-life mood disorders, outline implications of these processes for the clinical evaluation and management of later-life psychiatric disorders, and finally put forth suggestions for better integrating aging and developmental processes into the National Institute of Mental Health's Research Domain Criteria.

Fatigue in Parkinson's disease

Fatigue is one of the most common nonmotor symptoms in Parkinson's disease and may affect a wide range of everyday activities, cause disability and reduce quality of life. It occurs at every stage of PD, and once present will often persist and may worsen over time. Lack of a consensus of definition and classification, and a range of different self-reporting scales has so far made the study of fatigue challenging. We review a unifying taxonomy for defining fatigue in clinical and research contexts as well as case definition criteria for PD-related fatigue. The potential causes of fatigue in PD are discussed as are recommendations for treatment.

Assessing Fatigability in the Lab and in Daily Life in Older Adults With Osteoarthritis Using Perceived, Performance, and Ecological Measures

BACKGROUND

Fatigue in older adults is associated with functional decline and reduced participation in daily life; however, it is not well characterized. Examining fatigue within activity performance, or "fatigability," is a recommended approach to begin to understand fatigue and its underlying mechanisms. This study examined the construct validity of lab-based measures of fatigability and compared these measures with fatigability in daily life (termed ecological fatigability).

METHODS

Participants with osteoarthritis and fatigue (n = 163) underwent laboratory assessments, completed questionnaires, and wore accelerometers for 7 days while tracking symptoms and behaviors. Lab-based fatigability measures were quantified using the 6-minute walk test. Perceived fatigability was assessed by asking participants before and after the test to report: (i) fatigue severity and (ii) perceived exertion. Performance fatigability was calculated using change in walking speed divided by total distance walked. Ecological fatigability was calculated from the 7-day assessment in which fatigue severity was reported five times a day and physical activity was continuously measured. Additional ecological measures (eg, self-pacing) were examined.

RESULTS

Lab-based perceived and performance fatigability measures were highly inter-correlated, moderately correlated with gait speed and metabolic measures, and weakly correlated with physical activity. Although ecological fatigability was weakly correlated with lab-based measures, participants with high fatigability on lab-based measures demonstrated more self-pacing behaviors than participants with low fatigability.

CONCLUSION

Lab-based fatigability measures are related to physical capacity measured both in the lab and daily life. Lab-based fatigability measures provide important information regarding daily life fatigability useful for future intervention development.

Effect of Strength Training on Oxidative Stress and the Correlation of the Same with Forearm Vasodilatation and Blood Pressure of Hypertensive Elderly Women: A Randomized Clinical Trial

The aim of the study was to evaluate the effect of strength training on oxidative stress and the correlation of the same with forearm vasodilatation and mean blood pressure of hypertensive elderly women, at rest (basal) and during a static handgrip exercise. Insufficiently active hypertensive elderly women (N = 25; mean age = 66.1 years) were randomized into a 10 week strength training group (n = 13) or control (n = 12) group. Plasma malondialdehyde (MDA), total antioxidant capacity (TAC), plasma nitrite (NO2-), forearm blood flow (FBF), mean blood pressure (MBP) and vascular conductance ([FBF / MBP] x 100) were evaluated before and after the completion of the interventions. The strength training group increased the TAC (pre: Median = 39.0; Interquartile range = 34.0-41.5% vs post: Median = 44.0; Interquartile range = 38.0-51.5%; p = 0.006) and reduced the MDA (pre: 4.94 ± 1.10 μM vs post: 3.90 ± 1.35 μM; p = 0.025; CI-95%: -1.92 --0.16 μM). The strength training group increased basal vascular conductance (VC) (pre: 3.56 ±0.88 units vs post: 5.21 ±1.28 units; p = 0.001; CI-95%: 0.93-2.38 units) and decreased basal MBP (pre: 93.1 ±6.3 mmHg vs post: 88.9 ±5.4 mmHg; p = 0.035; CI-95%: -8.0 --0.4 mmHg). Such changes were also observed during static handgrip exercise. A moderate correlation was observed between changes in basal VC and MBP with changes in NO2- (ΔVC → r = -0.56, p = 0.047; ΔMBP → r = -0.41, p = 0.168) and MDA (ΔVC → r = 0.64, p = 0.019; ΔMBP → r = 0.31, p = 0.305). The strength training program reduced the oxidative stress of the hypertensive elderly women and this reduction was moderately correlated with their cardiovascular benefits.

TRIAL REGISTRATION

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Metabolic Rate and Perceived Exertion of Walking in Older Adults With Idiopathic Chronic Fatigue

BACKGROUND

Fatigue is a common complaint in older adults, often not associated with underlying medical conditions. The purpose of this study was to investigate metabolic rate (MR) of walking, walking performance, and perception-based exertion during walking in older adults with and without idiopathic chronic fatigue (ICF).

METHODS

20 older adults (aged 70.8±4.9 years), reporting 2 SD above normative values of the Functional Assessment of Chronic Illness Therapy-Fatigue scale and without overt health conditions that explained their symptoms, were compared with 25 age-matched older adults (73.2±5.1 years) without fatigue symptoms. Participants walked 400 m at a rapid pace on a 20-m course. On a separate visit, oxygen consumption was measured during treadmill test at standard (40.2 m/min), preferred paces (40-83 m/min) and peak capacity. Ratings of perceived exertion (RPE) were measured at each treadmill stage and after each lap of the 400-m walk test.

RESULTS

During the 400-m walk test, individuals with ICF showed lower overall walking speed and reported a steady increase in RPE with no change observed in non-fatigued group (1.63±1.72 vs 0.27±0.68, p < .01). Similar findings on RPE were noted on treadmill test. Gross MR, mass-specific MR, mass-specific net MR, and MR as a percent of peak oxygen consumption of walking were similar between groups during standard, preferred paces and peak capacity on treadmill.

CONCLUSIONS

This study suggests that ICF in older adults is not related to elevated metabolic cost of walking. Higher RPE without concomitant decreases in performance indicate a potential disconnect between metabolic output and sensations during movement.

The relationship between mitochondrial function and walking performance in older adults with a wide range of physical function

BACKGROUND

Age related declines in walking performance may be partly attributable to skeletal muscle mitochondrial dysfunction as mitochondria produce over 90% of ATP needed for movement and the capacity for oxidative phosphorylation decreases with age.

METHODS

Participants were from two studies: an ancillary to the Lifestyle Interventions and Independence for Elders (LIFE) Study (n=33), which recruited lower functioning participants (Short Physical Performance Battery [SPPB], 7.8±1.2), and the Study of Energy and Aging-Pilot (SEA, n=29), which enrolled higher functioning (SPPB, 10.8±1.4). Physical activity was measured objectively using the Actigraph accelerometer (LIFE) and SenseWear Pro armband (SEA). Phosphocreatine recovery following muscle contraction of the quadriceps was measured using (31)P magnetic resonance spectroscopy and ATPmax (mM ATP/s) was calculated. Walking performance was defined as time (s) to walk 400m at a usual-pace. The cross-sectional association between mitochondrial function and walking performance was assessed using multivariable linear regression.

RESULTS

Participants were 77.6±5.3years, 64.2% female and 67.2% white. ATPmax was similar in LIFE vs. SEA (0.52±0.14 vs. 0.55±0.14, p=0.31), despite different function and activity levels (1.6±2.2 vs.77.4±73.3min of moderate activity/day, p<0.01). Higher ATPmax was related to faster walk-time in SEA (r(2)=0.19, p=0.02,); but not the LIFE (r(2)<0.01, p=0.74) cohort.

CONCLUSIONS

Mitochondrial function was associated with walking performance in higher functioning, active older adults, but not lower functioning, sedentary older adults.

Rising Energetic Cost of Walking Predicts Gait Speed Decline With Aging

BACKGROUND

Slow gait is a robust biomarker of health and a predictor of functional decline and death in older adults, yet factors contributing to the decline in gait speed with aging are not well understood. Previous research suggests that the energetic cost of walking at preferred speed is inversely associated with gait speed, but whether individuals with a rising energetic cost of walking experience a steeper rate of gait speed decline has not been investigated.

METHODS

In participants of the Baltimore Longitudinal Study of Aging, the energetic cost of overground walking at preferred speed (mL/kg/m) was assessed between 2007 and 2014 using a portable indirect calorimeter. The longitudinal association between the energetic cost of walking and usual gait speed over 6 meters (m/s) was assessed with multivariate linear regression models, and the risk of slow gait (<1.0 m/s) was analyzed using Cox proportional hazards models.

RESULTS

The study population consisted of 457 participants aged 40 and older who contributed 1,121 person-visits to the analysis. In fully adjusted models, increases in the energetic cost of walking predicted the rate of gait speed decline in those older than 65 years (β = -0.008 m/s, p < .001). Moreover, those with a higher energetic cost of walking (>0.17mL/kg/m) had a 57% greater risk of developing slow gait compared with a normal energetic cost of walking (≤0.17mL/kg/m; adjusted hazard ratio = 1.57, 95% confidence interval: 1.01-2.46).

CONCLUSIONS

These findings suggest that strategies to maintain walking efficiency hold significant implications for maintaining mobility in late life. Efforts to curb threats to walking efficiency should focus on therapies to treat gait and balance impairments, and reduce clinical disease burden.

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

BACKGROUND

For older adults, falls are a serious health problem, with more than 30% of people older than 65 suffering a fall at least once a year. One element often overlooked in the assessment of falls is whether a person's balance, walking ability, and overall falls risk is affected by performing activities of daily living such as walking.

OBJECTIVE

This study assessed the immediate impact of incline walking at a moderate pace on falls risk, leg strength, reaction time, gait, and balance in 75 healthy adults from 30 to 79 years of age. Subjects were subdivided into 5 equal groups based on their age (group 1, 30-39 years; group 2, 40-49 years; group 3, 50-59 years; group 4, 60-69 years; group 5, 70-79 years).

METHODS

Each person's falls risk (using the Physiological Profile Assessment), simple reaction time, leg strength, walking ability, and standing balance were assessed before and after a period of incline walking on an automated treadmill. The walking task consisted of three 5-minute trials at a faster than preferred pace. Fatigue during walking was elicited by increasing the treadmill incline in increments of 2° (from level) every minute to a maximum of 8°.

RESULTS

As predicted, significant age-related differences were observed before the walking activity. In general, increasing age was associated with declines in gait speed, lower limb strength, slower reaction times, and increases in overall falls risk. Following the treadmill task, older adults exhibited increased sway (path length 60-69 years; 10.2 ± 0.7 to 12.1 ± 0.7 cm: 70-79 years; 12.8 ± 1.1 to 15.1 ± 0.8 cm), slower reaction times (70-79 years; 256 ± 6 to 287 ± 8 ms), and declines in lower limb strength (60-69 years; 36 ± 2 to 31 ± 1 kg: 70-79 years; 32.3 ± 2 to 27 ± 1 kg). However, a significant increase in overall falls risk (pre; 0.51 ± 0.17: post; 1.01 ± 0.18) was only seen in the oldest group (70-79 years). For all other persons (30-69 years), changes resulting from the treadmill-walking task did not lead to a significant increase in falls risk.

CONCLUSIONS

As most falls occur when an individual is moving and/or fatigued, assessing functional properties related to balance, gait, strength, and falls risk in older adults both at rest and following activity may provide additional insight.

Body Acceleration as Indicator for Walking Economy in an Ageing Population

BACKGROUND

In adults, walking economy declines with increasing age and negatively influences walking speed. This study aims at detecting determinants of walking economy from body acceleration during walking in an ageing population.

METHODS

35 healthy elderly (18 males, age 51 to 83 y, BMI 25.5±2.4 kg/m2) walked on a treadmill. Energy expenditure was measured with indirect calorimetry while body acceleration was sampled at 60Hz with a tri-axial accelerometer (GT3X+, ActiGraph), positioned on the lower back. Walking economy was measured as lowest energy needed to displace one kilogram of body mass for one meter while walking (WCostmin, J/m/kg). Gait features were extracted from the acceleration signal and included in a model to predict WCostmin.

RESULTS

On average WCostmin was 2.43±0.42 J/m/kg and correlated significantly with gait rate (r2 = 0.21, p<0.01) and regularity along the frontal (anteroposterior) and lateral (mediolateral) axes (r2 = 0.16, p<0.05 and r2 = 0.12, p<0.05 respectively). Together, the three variables explained 46% of the inter-subject variance (p<0.001) with a standard error of estimate of 0.30 J/m/kg. WCostmin and regularity along the frontal and lateral axes were related to age (WCostmin: r2 = 0.44, p<0.001; regularity: r2 = 0.16, p<0.05 and r2 = 0.12, p<0.05 respectively frontal and lateral).

CONCLUSIONS

The age associated decline in walking economy is induced by the adoption of an increased gait rate and by irregular body acceleration in the horizontal plane.

Gait energetic efficiency in older adults with and without knee pain: results from the Baltimore Longitudinal Study of Aging

With aging, customary gait patterns change and energetic efficiency declines, but the relationship between these alterations is not well understood. If gait characteristics that develop with aging explain part of the decline in energetic efficiency that occur in most aging individuals, then efforts to modify these characteristics could delay or prevent mobility limitation. This study characterizes gait patterns in older persons with and without knee pain and tests the hypothesis that changes in gait characteristics due to knee pain are associated with increased energetic cost of walking in older adults. Study participants were 364 men and 170 women aged 60 to 96 years enrolled in the Baltimore Longitudinal Study of Aging (BLSA), of whom 86 had prevalent knee pain. Gait patterns were assessed at participant self-selected usual pace in the gait laboratory, and the energetic cost of walking was assessed by indirect calorimetry during self-selected usual pace walking over 2.5 min in a tiled corridor using a portable equipment. Participants with knee pain were less energetically efficient than those without pain (oxygen consumption 0.97 vs. 0.88 ml/(10 m · 100 kg); p = 0.002) and had slower gait speed and smaller range of motion (ROM) at the hip and knee joints (p < 0.05, for all). Slower gait speed and lower knee ROM in participants with knee pain and longer double support time and higher ankle ROM in participants without knee pain were associated with lower energetic efficiency (p < 0.05, for all). Slower gait speed and lower knee ROM were correlates of knee pain and were found to mediate the association between age and oxygen consumption. Although knee pain is associated with a higher energetic cost of walking, gait characteristics associated with energetic efficiency differ by pain status which suggests that compensatory strategies both in the presence and absence of pain may impact gait efficiency.