Muscle weakness and functional limitations in an ethnically diverse sample of older adults

Collective Weakness and Fluidity in Weakness Status Associated With Basic Self-Care Limitations in Older Americans

Aims

To examine the associations of 1) absolute and normalized weakness cut-points, 2) collective weakness categories, and 3) changes in weakness status on future activities of daily living (ADL) limitations in older Americans.

Methods

The analytic sample included 11,656 participants aged ≥65-years from the 2006-2018 waves of the Health and Retirement Study. ADL were self-reported. A handgrip dynamometer measured handgrip strength (HGS). Males were classified as weak if their HGS was <35.5-kg (absolute), <0.45-kg/kg (body mass normalized), or <1.05-kg/kg/m2 (body mass index (BMI) normalized); females were considered weak if their HGS was <20.0-kg, <0.337-kg/kg, or <0.79-kg/kg/m2. Collective weakness categorized those below 1, 2, or all 3 absolute and normalized cut-points. These collective categories were also used to classify observed changes in weakness status over time (onset, persistent, progressive, recovery).

Results

Older Americans below absolute and normalized weakness cut-points had greater future ADL limitations odds: 1.34 (95% confidence interval (CI): 1.22-1.47) for absolute, 1.36 (CI: 1.24-1.50) for BMI normalized, and 1.56 (CI: 1.41-1.73) for body mass normalized. Persons below 1, 2, or 3 cut-points had 1.36 (CI: 1.19-1.55), 1.60 (CI: 1.41-1.80), and 1.70 (CI: 1.50-1.92) greater odds for future ADL limitations, respectively. Those in each changing weakness classification had greater future ADL limitation odds: 1.28 (CI: 1.01-1.62) for onset, 1.53 (CI: 1.22-1.92) for persistent, 1.72 (CI: 1.36-2.19) for progressive, and 1.34 (CI: 1.08-1.66) for recovery.

Conclusions

The presence of weakness, regardless of cut-point and change in status over time, was associated with greater odds for future ADL limitations.

Relative Sit-to-Stand Muscle Power Predicts an Older Adult's Physical Independence at Age of 90 Yrs Beyond That of Relative Handgrip Strength, Physical Activity, and Sedentary Time: A Cross-sectional Analysis

OBJECTIVES

Muscle power is important for an older adult's physical independence and can be easily estimated using the sit-to-stand test. This investigation aimed to assess whether muscle power estimated using the sit-to-stand test could identify older adults at risk of losing physical independence beyond handgrip strength, physical activity, and sedentary time and to develop minimal sit-to-stand power thresholds.

DESIGN

Physical independence was assessed cross-sectionally in older adults using a composite physical function questionnaire. Muscle power was calculated using the 30-sec sit-to-stand test. Muscle strength was determined using a handgrip dynamometer. Physical activity and sedentary time were assessed by accelerometry. Multiple logistic regression was used to assess the independent association between sit-to-stand power and projected physical independence ( n = 737). Receiver operator characteristic curves were used to develop sit-to-stand power cut points ( N = 1748).

RESULTS

Sit-to-stand power proved to be the best predictor of physical independence in later life regardless of handgrip strength, physical activity, and sedentary time (standardized B = 0.45, -0.02, 0.12, -0.28, respectively). Sex- and age-specific cutoffs for sit-to-stand power had good discriminatory ability (area under the curve = 0.75-0.78 [women], 0.76-0.82 [men]).

CONCLUSIONS

Sit-to-stand power can be used as a simple and practical screening tool to assess an older adult's future physical independence.

Effects of resistance training combined with balance training on physical function among older adults: a protocol for a randomised controlled trial

INTRODUCTION

The world's population is ageing. Age-related declines in physical function negatively affect the quality of life but may be ameliorated by certain types of exercise. The purpose of this study is to investigate the effects of combining resistance training (RT) with balance training on physical function in older community-dwelling adults to provide a reference for this type of exercise compared with other exercises and to provide a theoretical basis for optimising exercise plans to improve physical function among older adults.

METHODS

This single-blind randomised controlled trial will recruit 66 community dwelling adults 60-89 years of age with normal cognition. Participants will be randomly assigned to one of three groups: RT, RT combined with balance training or a control group with usual daily activities. Exercise interventions will be conducted in three 45 min sessions per week for 24 weeks. Primary physical function outcomes will be assessed using the timed up and go test, usual walking speed, maximal walking speed, 30 s chair stand and 30 s arm curl. Secondary assessments will be conducted using the 2 min step test, back scratch test and chair sit-and-reach test. All physical function assessments will be performed at baseline and after 12 and 24 weeks of exercise interventions. Exercise intensity will be monitored to maintain moderate intensity by heart rate, ratings of perceived exertion and OMNI-Resistance Exercise Scale. Data that conform to a normal distribution will be expressed as means±SD, otherwise as medians and interquartile intervals. Pretest, mid-test and post-test outcomes will be analysed for within-group and between-group comparisons using two-way repeated measures analyses of variance.

ETHICS AND DISSEMINATION

This proposal was reviewed and approved by the Shanghai University of Sport Research Ethics Committee (102772021RT067). The results will be disseminated to the trial participants and as a peer-reviewed publication.

TRIAL REGISTRATION NUMBER

ChiCTR2200056090.

Physical Function in Middle-aged and Older Adults With Type 1 Diabetes: Long-term Follow-up of the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications Study

OBJECTIVE

To describe the prevalence and clinical correlates of functional limitations in middle-aged and older adults with long-standing type 1 diabetes.

RESEARCH DESIGN AND METHODS

Functional limitations were assessed for 1,094 participants in the Epidemiology of Diabetes Interventions and Complications (EDIC) study, a multicenter, longitudinal, observational follow-up of participants with type 1 diabetes randomly assigned to intensive or conventional diabetes therapy during the Diabetes Control and Complications Trial (DCCT). The primary outcome measure was a score <10 on the Short Physical Performance Battery (SPPB). The secondary outcome, self-reported functional limitation, was assessed by written questionnaire. Logistic regression models were used to assess associations of both outcomes with demographic and clinical factors (glycemic and nonglycemic factors, micro- and macrovascular complications, DCCT cohort, and treatment assignment).

RESULTS

Participants were 53% male, with mean ± SD age 59.5 ± 6.8 years and diabetes duration 37.9 ± 4.9 years. The prevalence of SPPB score <10 was 21%. The prevalence of self-reported functional limitations was 48%. While DCCT treatment assignment was not associated with physical function outcomes measured ∼25 years after the end of the DCCT, the time-weighted mean DCCT/EDIC HbA1c was associated with both outcomes. Other clinical factors associated with both outcomes in multivariable analyses were BMI, general psychological distress, and cardiac autonomic neuropathy.

CONCLUSIONS

Almost half of the middle-aged and older adults with long-standing type 1 diabetes reported functional limitations, which were associated with higher HbA1c and BMI, general psychological distress, and cardiac autonomic neuropathy. Future research is needed to determine whether these findings are generalizable.

Musculoskeletal Morbidity Among Adults Living With Spina Bifida and Cerebral Palsy

Background

Individuals living with cerebral palsy (CP) or spina bifida (SB) are at heightened risk for chronic health conditions that may develop or be influenced by the impairment and/or the process of aging.

Objectives

The objective of this study was to compare the incidence of and adjusted hazards for musculoskeletal (MSK) morbidities among adults living with and without CP or SB.

Methods

A retrospective, longitudinal cohort study was conducted among adults living with (n = 15,302) CP or SB and without (n = 1,935,480) CP or SB. Incidence estimates of common MSK morbidities were compared at 4 years of enrollment. Survival models were used to quantify unadjusted and adjusted hazard ratios for incident MSK morbidities. The analyses were performed in 2019 to 2020.

Results

Adults living with CP or SB had a higher 4-year incidence of any MSK morbidity (55.3% vs. 39.0%) as compared to adults without CP or SB, and differences were to a clinically meaningful extent. Fully adjusted survival models demonstrated that adults with CP or SB had a greater hazard for all MSK disorders; this ranged from hazard ratio (HR) 1.40 (95% CI, 1.33 to 1.48) for myalgia to HR 3.23 (95% CI, 3.09 to 3.38) for sarcopenia and weakness.

Conclusion

Adults with CP or SB have a significantly higher incidence of and risk for common MSK morbidities as compared to adults without CP or SB. Efforts are needed to facilitate the development of improved clinical screening algorithms and early interventions to reduce risk of MSK disease onset/progression in these higher risk populations.

Design Considerations for Immersive Virtual Reality Applications for Older Adults: A Scoping Review

Immersive virtual reality (iVR) has gained considerable attention recently with increasing affordability and accessibility of the hardware. iVR applications for older adults present tremendous potential for diverse interventions and innovations. The iVR literature, however, provides a limited understanding of guiding design considerations and evaluations pertaining to user experience (UX). To address this gap, we present a state-of-the-art scoping review of literature on iVR applications developed for older adults over 65 years. We performed a search in ACM Digital Library, IEEE Xplore, Scopus, and PubMed (1 January 2010–15 December 2019) and found 36 out of 3874 papers met the inclusion criteria. We identified 10 distinct sets of design considerations that guided target users and physical configuration, hardware use, and software design. Most studies carried episodic UX where only 2 captured anticipated UX and 7 measured longitudinal experiences. We discuss the interplay between our findings and future directions to design effective, safe, and engaging iVR applications for older adults.

Linear association between grip strength and all-cause mortality among the elderly: results from the SHARE study

BACKGROUND

Grip strength had become a potential tool for clinical assessments, while the predictive value of the grip strength of community-based populations had some limitations.

AIMS

To identify the shapes of the association between grip strength and all-cause mortality in the Survey of Health, Ageing and Retirement in Europe (SHARE) cohort.

METHODS

Based on the SHARE cohort, 13,231 subjects aged 65 years and older were included in this study. Cox models with penalized splines (P-splines) were employed to characterize the shapes of the association between grip strength and all-cause mortality with the adjustment of covariates including sociodemographic characteristics, health characteristics, behavioral habits, and illness status. Then grip strength was analyzed as a categorical variable in quintile to examine the impact of low grip strength on all-cause mortality.

RESULTS

Inversely linear associations were found between grip strength and mortality both in males and females after adjustment for covariates. The hazard ratios (HRs) and their 95% confidence intervals (CIs) for each 5 kg decrease in grip strength to all-cause mortality were 1.11 (1.06-1.18) in males and 1.17 (1.08-1.28) in females. In comparison with subjects in the fifth quintile, the adjusted HRs and 95% CIs of all-cause mortality in the first quintile was 2.39 (1.79-3.19) in males and 1.84 (1.34-2.51) in females. Which were statistically significant in the second quintile compared with the fifth quintile [Males: 2.06 (1.56, 2.74), Females: 1.83 (1.35, 2.48)].

CONCLUSIONS

Grip strength is inversely linear association with all-cause mortality and the low grip strength at the first and second quintile are a robust predictor of all-cause mortality.

Factors associated with functional capacity in the elderly enrolled in the Family Health Strategy

The study investigated the prevalence of functional capacity decline and its associated factors in the older people enrolled in the Family Health Strategy (ESF) in a city in the south of Minas Gerais. This is an observational, cross-sectional, population-based study with 406 elderly (70.49 years ± 6.77). The functional capacity was evaluated by the Short Physical Performance Battery (SPPB), and its associated factors were evaluated by a structured questionnaire including sociodemographic, economic, clinical and physical aspects. The analysis of plasma levels of inflammatory mediators was performed by the ELISA method. Multiple linear regression was used for the analyses (p < 0.05). The prevalence of functional decline in the sample was 57.6% and factors associated with functional capacity were advanced age, female gender, number of medications, depressive symptoms, high plasma concentrations of the soluble receptor of tumor necrosis factor alpha 1 (sTNFR1) and low handgrip strength. The results demonstrated that functional capacity was associated with a network of multidimensional factors. This study contributes to the practice of ESF professionals by indicating the main factors that can guide actions to promote and prevent the decline of functional capacity in the elderly population.

Handgrip Strength Asymmetry and Weakness are Differentially Associated with Functional Limitations in Older Americans

Background: Handgrip strength (HGS) is a convent measure of strength capacity and associated with several age-related health conditions such as functional disability. Asymmetric strength between limbs has been linked to diminished function. Therefore, both HGS asymmetry and weakness could be associated with functional disability. We examined the associations of HGS asymmetry and weakness on functional limitations in a nationally representative sample of older Americans. Methods: Data were analyzed from 2689 adults ≥ 60 years who participated in the 2011–2012 and 2013–2014 waves of the National Health and Nutrition Examination Survey. Weakness was defined as HGS < 26 kg for men and < 16 kg for women. Asymmetry was determined from the ratio of the dominant and non-dominant HGS. Those with HGS ratio 0.9–1.1 were considered as having HGS symmetry, and those outside this range had asymmetry. Results: Compared to those with symmetric HGS and were not weak, those with weakness alone, and both weakness and HGS asymmetry had 2.47 (95% confidence interval [CI]: 1.14–5.35) and 3.93 (CI: 1.18–13.07) greater odds for functional limitations, respectively. However, HGS asymmetry alone was not associated with functional limitations (odds ratio: 0.80; CI: 0.62–1.03). Conclusion: The use of HGS asymmetry in protocols could improve the prognostic value of handgrip dynamometers.

Absolute and Body Mass Index Normalized Handgrip Strength Percentiles by Gender, Ethnicity, and Hand Dominance in Americans

BACKGROUND

Gender and ethnicity are factors which influence strength, and hand dominance could be a critical component of handgrip strength (HGS) testing. Providing such HGS percentiles across the lifespan may help to identify weakness-related health concerns. We sought to generate growth charts and curves for HGS by gender and ethnicity in a nationally-representative sample of Americans aged 6-80 years.

METHODS

Data from 13,617 participants in the 2011-2012 and 2013-2014 waves of the National Health and Nutrition Examination Survey were analyzed. HGS was measured with a handgrip dynamometer. Age, gender, ethnicity, and hand dominance were self-reported. Body Mass Index (BMI) was calculated from height and body mass. Measures of absolute HGS and HGS normalized to BMI were separately included in parametric quantile regression analyses for determining the 10th-90th percentiles across ages by gender and ethnicity. Similar models were also conducted by hand dominance.

RESULTS

Differences in absolute HGS and HGS normalized to BMI quantiles across ages existed for each ethnicity regardless of gender. In men, absolute HGS generally increased until about 25 years of age, began to decline around age 30 years, and regressed into older adulthood. In women, absolute HGS appeared to rise starting at age 6 years, peaked between 20 and 30 years of age, but was maintained into mid-life before declining in older adulthood. Similar results were found for HGS normalized to BMI.

CONCLUSIONS

Our findings provide percentile charts for HGS capacity that could be utilized for comparing individual measures of HGS to those from a United States population-representative sample.

Resistance Training for Older Adults: Position Statement From the National Strength and Conditioning Association

Fragala, MS, Cadore, EL, Dorgo, S, Izquierdo, M, Kraemer, WJ, Peterson, MD, and Ryan, ED. Resistance training for older adults: position statement from the national strength and conditioning association. J Strength Cond Res 33(8): 2019-2052, 2019-Aging, even in the absence of chronic disease, is associated with a variety of biological changes that can contribute to decreases in skeletal muscle mass, strength, and function. Such losses decrease physiologic resilience and increase vulnerability to catastrophic events. As such, strategies for both prevention and treatment are necessary for the health and well-being of older adults. The purpose of this Position Statement is to provide an overview of the current and relevant literature and provide evidence-based recommendations for resistance training for older adults. As presented in this Position Statement, current research has demonstrated that countering muscle disuse through resistance training is a powerful intervention to combat the loss of muscle strength and muscle mass, physiological vulnerability, and their debilitating consequences on physical functioning, mobility, independence, chronic disease management, psychological well-being, quality of life, and healthy life expectancy. This Position Statement provides evidence to support recommendations for successful resistance training in older adults related to 4 parts: (a) program design variables, (b) physiological adaptations, (c) functional benefits, and (d) considerations for frailty, sarcopenia, and other chronic conditions. The goal of this Position Statement is to a) help foster a more unified and holistic approach to resistance training for older adults, b) promote the health and functional benefits of resistance training for older adults, and c) prevent or minimize fears and other barriers to implementation of resistance training programs for older adults.

Daily Protein Intake and Distribution of Daily Protein Consumed Decreases Odds for Functional Disability in Older Americans

Objective: We sought to determine whether daily protein intake and protein distribution across eating occasions were associated with functional disability in a national sample of older Americans. Methods: Data from 8,070 adults aged ≥60 years from the 2007-2016 waves of the National Health and Nutrition Examination Survey were included. Protein intake and functional capacity was self-reported. A daily protein recommendation of ≥1.0 g/kg/day was utilized. The daily protein recommendation was then spread-out across four meals, whereby a ≥0.25 g/kg/meal threshold was used. Results: Those meeting the daily protein recommendation had 0.78 (95% confidence interval [CI] = [0.65, 0.93]) decreased odds for functional disability. Persons meeting the protein intake threshold per eating occasion for one, two, three, and four occasions had 0.60 (CI = [0.38, 0.95]), 0.48 (CI = [0.30, 0.77]), 0.47 (CI = [0.29, 0.77]), and 0.39 (CI = [0.20, 0.75]) decreased odds for functional disability, respectively. Discussion: Protein consumption seems to be important for preserving function in older Americans.

Effects of muscular strength training and growth hormone (GH) supplementation on femoral bone tissue: analysis by Raman spectroscopy, dual-energy X-ray absorptiometry, and mechanical resistance

The aim of the present study was to verify the effects of muscular strength training and growth hormone (GH) supplementation on femoral bone tissue by Raman spectroscopy (Raman), dual-energy X-ray absorptiometry (DXA), and mechanical resistance (F-max) analysis. A total of 40 male Wistar animals, 60 days old, were used. The animals were distributed into four groups: control (C), control with GH (GHC), muscular strength training (T), and muscular strength training with GH (GHT). Blood samples were collected for the quantification of creatine kinase (CK-MB) and the femurs were removed for analysis by Raman, DXA, and F-max. A more pronounced increase in the bone mineral components was verified in the T group, for all the variables obtained by the Raman (calcium, phosphate, amide, and collagen). In addition, for animals submitted to GH supplementation, there was a reduction in the variable bone mineral density (BMD) obtained by the DXA (p < 0.05). Finally, the animals that received GH supplementation presented a higher F-max, but without statistical significance (p > 0.05). It was concluded that animals that received GH supplementation demonstrated a decrease in BMD. In addition, T alone was able to promote increased calcium, phosphate, amide, and collagen compounds in bone tissue.

Role of physical performance measures for identifying functional disability among Chinese older adults: Data from the China Health and Retirement Longitudinal Study

Background

Functional disability is a common health burden in older adults and follows a hierarchical pattern. Physical performance measures are useful for the objective estimation of functional disability. This study primarily aimed to compare the validity of handgrip strength and gait speed, alone and in combination, for recognizing the functional disability among Chinese older adults. This study also aimed to stratify the functional disability according to the criterion-referenced values of handgrip strength and gait speed.

Methods

We selected 6127 respondents from the 2011 wave of the China Health and Retirement Longitudinal Study. Here, we defined functional disability as needing any help in any items of activities of daily living (ADL) and instrumental activities of daily living (IADL). To assess the validity of physical performance measures alone and in combination for the recognition of functional disability, we conducted the receiver operating characteristic analysis.

Results

Compared with handgrip strength, the gait speed could better discriminate ADL disability and showed a satisfactory discriminant validity (area under the curve ≥ 0.7) in men. However, this finding was not found in the recognition of IADL disability. When combining these two measures, the parallel test showed a high sensitivity with a poor specificity, whereas the serial test showed a perfect specificity with a poor sensitivity.

Conclusion

We developed the hierarchical cut-off values of handgrip strength and gait speed for identifying and stratifying the functional disability among Chinese adults over 60 years old. The speed test was superior to handgrip strength in identifying ADL disability. The parallel tests of those with high sensitivity perhaps could help identify the functional disability. Further work on cost-utility analysis is warranted.

Reference values for handgrip strength and their association with intrinsic capacity domains among older adults

OBJECTIVE

The purposes of this study were three-fold: (i) to describe handgrip strength in older individuals aged ≥60 years in Colombia; (ii) to identify sex-specific and age-specific muscle weakness cut-off points in older adults; and (iii) to determine the odds of adverse events for each of the intrinsic capacity domains for individuals with handgrip strength greater than the muscle weakness cut-off points, as compared with their weaker counterparts.

METHODS

A cross-sectional study was conducted in Colombia, among 5237 older adults aged ≥60 years old (58.5% women, 70.5 ± 7.8 years), according to 'SABE Survey 2015'. Handgrip strength data were obtained with a Takei dynamometer. Sociodemographic variables, five domains of intrinsic capacity (i.e. locomotion, vitality, cognition, psychological, and sensory), and medical conditions were assessed and analyzed. Adjustments variables were age, ethnicity, socio-economic status, urbanicity, body mass index, smoking status, alcohol intake, drug use, physical activity, and co-morbid chronic diseases. Sex-stratified analyses were conducted with logistic regression models.

RESULTS

Handgrip strength was greater among men than among women (26.7 ± 8.5 vs. 16.7 ± 5.7 kg, respectively, P < 0.001) at all ages. Weak handgrip strength cut-off points ranged from 17.4 to 8.6 and from 10.1 to 4.9 in men and women, respectively. Overall, participants with optimal handgrip strength had better intrinsic capacity [in men, odds ratio (OR) = 0.62, 95% confidence interval (CI) 0.53 to 0.71; P < 0.001; and in women, OR = 0.79, 95% CI 0.68 to 0.92; P = 0.002] than their weaker counterparts. Also, men with optimal handgrip strength had a lower risk of hospitalization (OR = 0.47, 95% CI 0.29 to 0.78; P = 0.004) than their weaker counterparts.

CONCLUSIONS

This study is the first to describe handgrip strength values and cut-off points for muscle weakness among a nationally representative sample of Colombian older adults by age and sex. After categorizing older adults as weak or not weak based on the handgrip cut-off points, non-weakness was associated with a decreased odds of intrinsic capacity impairments. These cut-off points may be good candidates for clinical assessment of risks to physical and mental health in older Colombian adults.

The Association Between Differing Grip Strength Measures and Mortality and Cerebrovascular Event in Older Adults: National Health and Aging Trends Study

The purpose of this study was to compare the predictive capacity of different post-processing methods of hand grip strength (GS) for mortality and incident cerebrovascular events in older adults. A sample of 4,143 participants aged 65 years and older was included from the National Health and Aging Trends Study (NHATS) and followed for 6 years. GS measures included baseline (i.e., round 1) (1) absolute GS, (2) GS divided by body mass (NGS_mass), and (3) GS divided by body mass index (NGS_BMI), as well as (4) change in absolute GS from round 1 to round 2 (GS_1-2). Cox proportional hazards regression models were used to examine the association between sex- and age group-specific tertiles of GS measures (weak, moderate-strength, strong) with mortality (n = 641) and incident cerebrovascular events (n = 329). Absolute GS (hazard ratio [HR] = 1.83; 95% confidence interval [CI] = 1.51–2.22), NGS_mass (HR = 1.46; 95% CI = 1.21–1.76), and NGS_BMI (HR = 1.50; 95% CI = 1.24–1.82) were each associated with mortality among weak participants, but not GS_1-2 (HR = 1.10; 95% CI = 0.99–1.46). NGS_mass (HR = 1.54; 95% CI = 1.19–2.01) and NGS_BMI (HR = 1.37; 95% CI = 1.06–1.79) were both associated with incident cerebrovascular event among weak participants, but not absolute GS (HR = 1.12; 95% CI = 0.86–1.47) or GS_1-2 (HR = 1.11; 95% CI = 0.85–1.44). Absolute GS, NGS_mass, and NGS_BMI were each associated with mortality, whereas only NGS_mass and NGS_BMI were associated with cerebrovascular event. These findings suggest that different post-processing methods of GS may have differing predictive capacity in the elderly depending on the outcome of interest; however, since NGS measures were associated with both mortality and cerebrovascular events, they may be considered advantageous for screening in older adults.

Handgrip Strength and Health in Aging Adults

Handgrip strength (HGS) is often used as an indicator of overall muscle strength for aging adults, and low HGS is associated with a variety of poor health outcomes including chronic morbidities, functional disabilities, and all-cause mortality. As public health initiatives and programs target the preservation of muscle strength for aging adults, it is important to understand how HGS factors into the disabling process and the sequence of health events that connect low HGS with premature mortality. Such information will help to inform interventions designed to slow the disabling process and improve health outcomes for those at risk for muscle weakness. Further, unraveling the disabling process and identifying the role of weakness throughout the life course will help to facilitate the adoption of HGS measurements into clinical practice for healthcare providers and their patients. The purposes of this article were to (1) highlight evidence demonstrating the associations between HGS and clinically relevant health outcomes, (2) provide directions for future research in HGS and health, and (3) propose a sequence of health-related events that may better explain the role of muscle weakness in the disabling process.