Prediction of lumbar vertebral body compressive strength of overweight and obese older adults using morphed subject-specific finite-element models to evaluate the effects of weight loss.

BACKGROUND: Diet and exercise can promote weight loss in older adults; however, there is potential to increase fracture risk due to loss of bone mineral density (BMD) known to accompany weight loss. Weight loss effects on measures of bone quality and strength are currently unknown. AIMS: The purpose of this study is to develop subject-specific finite-element (FE) models of the lumbar spine and study the effect of intentional weight loss on bone strength in a pilot data set. METHODS: Computed tomography (CT) scans of the lumbar spine of 30 overweight and obese (mean BMI = 29.7 ± 3.9 kg/m2), older adults (mean age = 65.9 ± 4.6 years) undergoing an 18-month intentional weight loss intervention were obtained at baseline and post-intervention. Measures of volumetric BMD (vBMD) and variable cortical thickness were derived from each subject CT scan. Development of the subject-specific FE models of the lumbar spine involved model morphing techniques to accelerate the development of the models. vBMD-derived material properties and cortical thickness measures were directly mapped to baseline and post-intervention models. Bone strength was estimated through simulation of a quasi-static uniaxial compression test. RESULTS: From baseline to 18-month post-weight loss intervention, there were statistically significant decreases in estimated bone strength (6.5% decrease; p < 0.05). Adjusting for baseline bone measures and gender revealed no statistically significant correlations between weight change and change in vBMD, cortical thickness, or bone strength. CONCLUSION: Integration of CT-based measures and FE models with conventional areal BMD can improve the understanding of the effects of intentional weight loss on bone health.

Change in health-related quality of life and social cognitive outcomes in obese, older adults in a randomized controlled weight loss trial: Does physical activity behavior matter?

This article compared the effect of dietary weight loss administered alone (WL) or in combination with aerobic training (WL + AT) or resistance training (WL + RT) on health related quality of life, walking self-efficacy, stair climb self-efficacy, and satisfaction with physical function in older adults with cardiovascular disease or the metabolic syndrome. Participants (N = 249; M age = 66.9) engaged in baseline assessments and were randomly assigned to one of three interventions, each including a 6-month intensive phase and a 12-month follow-up. Those in WL + AT and WL + RT engaged in 4 days of exercise training weekly. All participants engaged in weekly group behavioral weight loss sessions with a goal of 7-10% reduction in body weight. Participants in WL + AT and WL + RT reported better quality of life and satisfaction with physical function at 6- and 18-months relative to WL. At month 6, WL + AT reported greater walking self-efficacy relative to WL + RT and WL, and maintained higher scores compared to WL at month 18. WL + AT and WL + RT reported greater stair climbing efficacy at month 6, and WL + RT remained significantly greater than WL at month 18. The addition of either AT or RT to WL differentially improved HRQOL and key psychosocial outcomes associated with maintenance of physical activity and weight loss. This underscores the important role of exercise in WL for older adults, and suggests health care providers should give careful consideration to exercise mode when designing interventions.

The effect of intervening hospitalizations on the benefit of structured physical activity in promoting independent mobility among community-living older persons: secondary analysis of a randomized controlled trial.

BACKGROUND: Among older persons, disability is often precipitated by intervening illnesses and injuries leading to hospitalization. In the Lifestyle Interventions and Independence for Elders (LIFE) Study, a structured moderate-intensity physical activity program, compared with a health education program, was shown to significantly reduce the amount of time spent with major mobility disability (MMD) over the course of 3.5 years. We aimed to determine whether the benefit of the physical activity program in promoting independent mobility was diminished in the setting of intervening hospitalizations. METHODS: We analyzed data from a single-blinded, parallel group randomized trial (ClinicalTrials.gov: NCT01072500). In this trial, 1635 sedentary persons, aged 70-89 years, who had functional limitations but were able to walk 400 m, were randomized from eight US centers between February 2010 and December 2013: 818 to physical activity (800 received intervention) and 817 to health education (805 received intervention). Intervening hospitalizations and MMD, defined as the inability to walk 400 m, were assessed every 6 months for up to 3.5 years. RESULTS: For both the physical activity and health education groups, intervening hospitalizations were strongly associated with the initial onset of MMD and inversely associated with recovery from MMD, defined as a transition from initial MMD onset to no MMD. The benefit of the physical activity intervention did not differ significantly based on hospital exposure. For onset of MMD, the hazard ratios (HR) were 0.79 (95% confidence interval [CI] 0.58-1.1) and 0.77 (0.62-0.95) in the presence and absence of intervening hospitalizations, respectively (P-interaction, 0.903). For recovery of MMD, the magnitude of effect was modestly greater among participants who were hospitalized (HR 1.5, 95% CI 0.71-3.0) than in those who were not hospitalized (HR 1.2, 95% CI 0.88-1.7), but this difference did not achieve statistical significance (P-interaction, 0.670). CONCLUSIONS: Intervening hospitalizations had strong deleterious effects on the onset of MMD and recovery from MMD, but did not diminish the beneficial effect of the LIFE physical activity intervention in promoting independent mobility. To achieve sustained benefits over time, structured physical activity programs should be designed to accommodate acute illnesses and injuries leading to hospitalizations given their high frequency in older persons with functional limitations. TRIAL REGISTRATION: ClinicalTrials.gov identifier NCT01072500 .

Effects of supervised exercise and dietary nitrate in older adults with controlled hypertension and/or heart failure with preserved ejection fraction.

Aerobic exercise training is an effective therapy to improve peak aerobic power (peak VO2) in individuals with hypertension (HTN, AHA/ACC class A) and heart failure patients with preserved ejection fraction (HFpEF). High nitrate containing beetroot juice (BRJ) also improves sub-maximal endurance and decreases blood pressure in both HTN and HFpEF. We hypothesized that combining an aerobic exercise and dietary nitrate intervention would result in additive or even synergistic positive effects on exercise tolerance and blood pressure in HTN or HFpEF. We report results from two pilot studies examining the effects of supervised aerobic exercise combined with dietary nitrate in patients with controlled HTN (n = 26, average age 65 ± 5 years) and in patients with HFpEF (n = 20, average age 69 ± 7 years). All patients underwent an aerobic exercise training regimen; half were randomly assigned to consume a high nitrate-containing beet juice beverage (BRJ containing 6.1 mmol nitrate for the HFpEF study consumed three times a week and 8 mmol nitrate for the HTN study consumed daily) while the other half consumed a beet juice beverage with the nitrate removed (placebo). The main result was that there was no added benefit observed for any outcomes when comparing BRJ to placebo in either HTN or HFpEF patients undergoing exercise training (p ≥ 0.14). There were within-group benefits. In the pilot study in patients with HFpEF, aerobic endurance (primary outcome), defined as the exercise time to volitional exhaustion during submaximal cycling at 75% of maximal power output, improved during exercise training within each group from baseline to end of study, 369 ± 149 s vs 520 ± 257 s (p = 0.04) for the placebo group and 384 ± 129 s vs 483 ± 258 s for the BRJ group (p = 0.15). Resting systolic blood pressure in patients with HFpEF also improved during exercise training in both groups, 136 ± 16 mm Hg vs 122 ± 3 mm Hg for the placebo group (p < 0.05) and 132 ± 12 mm Hg vs 119 ± 9 mm Hg for the BRJ group (p < 0.05). In the HTN pilot study, during a treadmill graded exercise test, peak oxygen consumption (primary outcome) did not change significantly, but time to exhaustion (also a primary outcome) improved in both groups, 504 ± 32 s vs 601 ± 38 s (p < 0.05) for the placebo group and 690 ± 38 s vs 772 ± 95 s for the BRJ group (p < 0.05) which was associated with a reduction in supine resting systolic blood pressure in BRJ group. Arterial compliance also improved during aerobic exercise training in both the HFpEF and the HTN patients for both BRJ and placebo groups. Future work is needed to determine if larger nitrate doses would provide an added benefit to supervised aerobic exercise in HTN and HFpEF patients.

Long-term effects of systemic gene therapy in a canine model of myotubular myopathy.

INTRODUCTION: X-linked myotubular myopathy (XLMTM), a devastating pediatric disease caused by the absence of the protein myotubularin, results from mutations in the MTM1 gene. While there is no cure for XLMTM, we previously reported effects of MTM1 gene therapy using adeno-associated virus (AAV) vector on muscle weakness and pathology in MTM1-mutant dogs. Here, we followed 2 AAV-infused dogs over 4 years. METHODS: We evaluated gait, strength, respiration, neurological function, muscle pathology, AAV vector copy number (VCN), and transgene expression. RESULTS: Four years following AAV-mediated gene therapy, gait, respiratory performance, neurological function and pathology in AAV-infused XLMTM dogs remained comparable to their healthy littermate controls despite a decline in VCN and muscle strength. CONCLUSIONS: AAV-mediated gene transfer of MTM1 in young XLMTM dogs results in long-term expression of myotubularin transgene with normal muscular performance and neurological function in the absence of muscle pathology. These findings support a clinical trial in patients. Muscle Nerve 56: 943-953, 2017.

Predictors of Change in Physical Function in Older Adults in Response to Long-Term, Structured Physical Activity: The LIFE Study.

OBJECTIVES: To evaluate the extent of variability in functional responses in participants in the Lifestyle Interventions and Independence for Elders (LIFE) study and to identify the relative contributions of intervention adherence, physical activity, and demographic and health characteristics to this variability. DESIGN: Secondary analysis. SETTING: Multicenter institutions. PARTICIPANTS: A volunteer sample (N=1635) of sedentary men and women aged 70 to 89 years who were able to walk 400m but had physical limitations, defined as a Short Physical Performance Battery (SPPB) score of ≤9. INTERVENTIONS: Moderate-intensity physical activity (n=818) consisting of aerobic, resistance, and flexibility exercises performed both center-based (2times/wk) and home-based (3-4times/wk) sessions or health education program (n=817) consisting of weekly to monthly workshops covering relevant health information. MAIN OUTCOME MEASURES: Physical function (gait speed over 400m) and lower extremity function (SPPB score) assessed at baseline and 6, 12, and 24 months. RESULTS: Greater baseline physical function (gait speed, SPPB score) was negatively associated with change in gait speed (regression coefficient ß=-.185; P<.001) and change in SPPB score (ß=-.365; P<.001), whereas higher number of steps per day measured by accelerometry was positively associated with change in gait speed (ß=.035; P<.001) and change in SPPB score (ß=.525; P<.001). Other baseline factors associated with positive change in gait speed and/or SPPB score include younger age (P<.001), lower body mass index (P<.001), and higher self-reported physical activity (P=.002). CONCLUSIONS: Several demographic and physical activity-related factors were associated with the extent of change in functional outcomes in participants in the LIFE study. These factors should be considered when designing interventions for improving physical function in older adults with limited mobility.

Gait speed response to aerobic versus resistance exercise training in older adults.

BACKGROUND: Little is known about the comparative effect of aerobic training (AT) versus resistance training (RT) on gait speed, a strong predictor of disability. AIMS: To compare the effect of AT versus RT on gait speed and other functional measures. METHODS: Overweight and obese [body mass index (BMI) ≥27.0 kg/m2] sedentary men and women aged 65-79 years engaged in 5 months of either 4 days/weeks moderate-intensity treadmill walking, AT, (n = 44) or 3 days/weeks moderate-intensity RT (n = 56). Usual-pace gait speed, fast-pace gait speed and short physical performance battery (SPPB) were evaluated in all participants before and after training. Peak oxygen consumption (VO2peak) was assessed in AT participants only, and knee extensor strength was assessed in RT participants. RESULTS: Both AT and RT resulted in clinically significant improvements in usual-pace gait speed (0.08 ± 0.14 and 0.08 ± 0.17 m/s, respectively, both p < 0.05) and SPPB (0.53 ± 1.40 and 0.53 ± 1.20 points, both p < 0.05) and chair rise time (-1.2 ± 3.2 and -1.7 ± 3.0 s, p < 0.05). Only AT improved fast-pace gait speed (0.11 ± 0.10 m/s, p < 0.05). In the RT participants, lower baseline knee strength was associated with less improvement in usual-pace gait speed. In AT participants, lower baseline VO2peak was associated with less improvement in chair rise time and self-reported disability. DISCUSSION: While both AT and RT improved usual-pace gait speed, only AT improved fast-pace gait speed. Lower baseline fitness was associated with less improvement with training. CONCLUSION: Research to directly compare which mode of training elicits the maximum improvement in older individuals with specific functional deficits could lead to better intervention targeting.

Effect of Structured Physical Activity on Overall Burden and Transitions Between States of Major Mobility Disability in Older Persons: Secondary Analysis of a Randomized Trial.

Background: The total time a patient is disabled likely has a greater influence on his or her quality of life than the initial occurrence of disability alone. Objective: To compare the effect of a long-term, structured physical activity program with that of a health education intervention on the proportion of patient assessments indicating major mobility disability (MMD) (that is, MMD burden) and on the risk for transitions into and out of MMD. Design: Single-blinded, parallel-group, randomized trial. (ClinicalTrials.gov: NCT01072500). Setting: 8 U.S. centers between February 2010 and December 2013. Participants: 1635 sedentary persons, aged 70 to 89 years, who had functional limitations but could walk 400 m. Intervention: Physical activity (n = 818) and health education (n = 817). Measurements: MMD, defined as the inability to walk 400 m, was assessed every 6 months for up to 3.5 years. Results: During a median follow-up of 2.7 years, the proportion of assessments showing MMD was substantially lower in the physical activity (0.13 [95% CI, 0.11 to 0.15]) than the health education (0.17 [CI, 0.15 to 0.19]) group, yielding a risk ratio of 0.75 (CI, 0.64 to 0.89). In a multistate model, the hazard ratios for comparisons of physical activity with health education were 0.87 (CI, 0.73 to 1.03) for the transition from no MMD to MMD; 0.52 (CI, 0.10 to 2.67) for no MMD to death; 1.33 (CI, 0.99 to 1.77) for MMD to no MMD; and 1.92 (CI, 1.15 to 3.20) for MMD to death. Limitation: The intention-to-treat principle was maintained for MMD burden and first transition out of no MMD, but not for subsequent transitions. Conclusion: A structured physical activity program reduced the MMD burden for an extended period, in part through enhanced recovery after the onset of disability and diminished risk for subsequent disability episodes. Primary Funding Source: National Institute on Aging, National Institutes of Health.

Self-reported Mobility in Older Patients Predicts Early Postoperative Outcomes after Elective Noncardiac Surgery.

BACKGROUND: Specific geriatric assessment tools may complement traditional perioperative risk stratification. The aim of this study was to evaluate whether self-reported mobility is predictive of postoperative outcomes in older patients undergoing elective noncardiac surgery. METHODS: Patients aged 69 yr or older (n = 197) underwent (1) traditional risk assessments (American Society of Anesthesiologists physical status classification and Revised Cardiac Risk Index), (2) five-point frailty evaluation, (3) self-reported mobility assessment using the Mobility Assessment Tool-short form (range, 30.21 [poor] to 69.76 [excellent]), and (4) measurements of high-sensitivity C-reactive protein. Outcomes were postoperative complications, time to discharge, and nursing home placement (NHP). RESULTS: In the sample of this study (mean age, 75 ± 5 yr; 51% women), 72% had intermediate- or high-risk surgery. Median time to discharge was 3 days (interquartile range, 1 to 4 days). Thirty patients (15%) developed postoperative complications, and 27 (13%) required NHP. After controlling for age, sex, body mass index, pain score, Revised Cardiac Risk Index, American Society of Anesthesiologist physical status, surgical risk, and high-sensitivity C-reactive protein, worse self-reported mobility (per 10-point decrease in Mobility Assessment Tool, which is equivalent to 1 SD) was associated with more postoperative complications (odds ratio [OR], 1.69; 95% CI, 1.05 to 2.73), later time to discharge (hazards ratio, 0.81; 95% CI, 0.68 to 0.96), and increased NHP (OR, 2.01; 95% CI, 1.13 to 3.56). By using the same model, intermediate frailty or frailty increased NHP (OR, 3.11; 95% CI, 1.02 to 9.54) but was not related to either postoperative complications or time to discharge. CONCLUSIONS: Preoperative self-reported mobility using a novel and brief assessment may help identify elderly patients at risk for adverse postoperative events.

Assessments of Fatty Infiltration and Muscle Atrophy From a Single Magnetic Resonance Image Slice Are Not Predictive of 3-Dimensional Measurements.

PURPOSE: To (1) determine whether standard clinical muscle fatty infiltration and atrophy assessment techniques using a single image slice for patients with a rotator cuff tear (RCT) are correlated with 3-dimensional measures in older individuals (60+ years) and (2) to determine whether age-associated changes to muscle morphology and strength are compounded by an RCT. METHODS: Twenty older individuals were studied: 10 with an RCT of the supraspinatus (5 men and 5 women) and 10 matched controls. Clinical imaging assessments (Goutallier and Fuchs scores and cross-sectional area ratio) were performed for participants with RCTs. Three-dimensional measurements of rotator cuff muscle and fat tissues were obtained for all participants using magnetic resonance imaging (MRI). Isometric joint moment was measured at the shoulder. RESULTS: There were no significant associations between single-image assessments and 3-dimensional measurements of fatty infiltration for the supraspinatus and infraspinatus muscles. Compared with controls, participants with RCTs had significantly increased percentages of fatty infiltration for each rotator cuff muscle (all P ≤ .023); reduced whole muscle volume for the supraspinatus, infraspinatus, and subscapularis muscles (all P ≤ .038); and reduced fat-free muscle volume for the supraspinatus, infraspinatus, and subscapularis muscles (all P ≤ .027). Only the teres minor (P = .017) fatty infiltration volume was significantly greater for participants with RCTs. Adduction, flexion, and external rotation strength (all P ≤ .021) were significantly reduced for participants with RCTs, and muscle volume was a significant predictor of strength for all comparisons. CONCLUSIONS: Clinical scores using a single image slice do not represent 3-dimensional muscle measurements. Efficient methods are needed to more effectively capture 3-dimensional information for clinical applications. Participants with RCTs had increased fatty infiltration percentages that were likely driven by muscle atrophy rather than increased fat volume. The significant association of muscle volume with strength production suggests that treatments to preserve muscle volume should be pursued for older patients with RCTs. LEVEL OF EVIDENCE: Level II, diagnostic study, with development of diagnostic criteria on the basis of consecutive patients with universally applied reference gold standard.

Psychometric properties of a computerized adaptive test for assessing mobility in older adults using novel video-animation technology.

PURPOSE: This paper reports on the psychometric properties of a computerized adaptive test (CAT) version of the Mobility Assessment Tool (MAT) for older adults (MAT-CAT). METHODS: An item pool of 78 video-animation-based items for mobility was developed, and response data were collected from a sample of 234 participants aged 65-90 years. The video-animation-based instrument was designed to minimize ambiguity in the presentation of task demands. In addition to evaluating traditional psychometric properties including dimensionality, differential item functioning (DIF), and local dependence, we extensively tested the performance of several MAT-CAT measures and compared their performances with a fixed format. RESULTS: Operationally, the MAT-CAT was sufficiently unidimensional and had acceptable levels of local independence. One DIF item was removed. Most importantly, the CAT measures showed that even starting with a single fixed item at the mean ability, the adaptive version delivered better performance than the fixed format in terms of several criteria including the standard error of estimate. CONCLUSION: The MAT-CAT demonstrated satisfactory psychometric properties and superior performance to a fixed format. The video-animation-based adaptive instrument can be used for assessing mobility with specificity and precision.

Design and implementation of the mobility assessment tool: software description.

BACKGROUND: In previous work, we described the development of an 81-item video-animated tool for assessing mobility. In response to criticism levied during a pilot study of this tool, we sought to develop a new version built upon a flexible framework for designing and administering the instrument. RESULTS: Rather than constructing a self-contained software application with a hard-coded instrument, we designed an XML schema capable of describing a variety of psychometric instruments. The new version of our video-animated assessment tool was then defined fully within the context of a compliant XML document. Two software applications--one built in Java, the other in Objective-C for the Apple iPad--were then built that could present the instrument described in the XML document and collect participants' responses. Separating the instrument's definition from the software application implementing it allowed for rapid iteration and easy, reliable definition of variations. CONCLUSIONS: Defining instruments in a software-independent XML document simplifies the process of defining instruments and variations and allows a single instrument to be deployed on as many platforms as there are software applications capable of interpreting the instrument, thereby broadening the potential target audience for the instrument. Continued work will be done to further specify and refine this type of instrument specification with a focus on spurring adoption by researchers in gerontology and geriatric medicine.

Upper extremity muscle volumes and functional strength after resistance training in older adults.

Aging leads to a decline in strength and an associated loss of independence. The authors examined changes in muscle volume, maximum isometric joint moment, functional strength, and 1-repetition maximum (1RM) after resistance training (RT) in the upper extremity of older adults. They evaluated isometric joint moment and muscle volume as predictors of functional strength. Sixteen healthy older adults (average age 75 ± 4.3 yr) were randomized to a 6-wk upper extremity RT program or control group. The RT group increased 1RM significantly (p < .01 for all exercises). Compared with controls, randomization to RT led to greater functional pulling strength (p = .003), isometric shoulder-adduction moment (p = .041), elbow-flexor volume (p = .017), and shoulder-adductor volume (p = .009). Shoulder-muscle volumes and isometric moments were good predictors of functional strength. The authors conclude that shoulder strength is an important factor for performing functional reaching and pulling tasks and a key target for upper extremity RT interventions.

Factors associated with falls in older adults: A secondary analysis of a 12-month randomized controlled trial.

PURPOSE: While identifying older adults at risk for falls is important, fall prediction models have had limited success, in part because of a poor understanding of which physical function measures to include. The purpose of this secondary analysis was to determine physical function measures that are associated with future falls in older adults. METHODS: In a 12-month trial comparing Vitamin D3 supplementation versus placebo on neuromuscular function, 124 older adults completed physical function measures at baseline, including the Short Physical Performance Battery (SPPB), Timed Up and Go, tests of leg strength and power, standing balance on a force plate with firm and foam surfaces, and walking over an instrumented walkway. Falls were recorded with monthly diaries over 12 months and categorized as no falls vs. one or more falls. Univariate and multivariable logistic regression adjusting for demographics, treatment assignment, depression, and prescription medications were conducted to examine the association between each physical function measure and future falls. Models were additionally adjusted for fall history. RESULTS: 61 participants sustained one or more falls. In univariate analysis, white race, depression, fall history, SPPB, and postural stability on foam were significantly associated with future falls. In multivariable analysis, fall history (OR (95% CI): 3.20 (1.42-7.43)), SPPB (0.80 (0.62-1.01)), and postural stability on foam (3.01 (1.18, 8.45)) were each significantly associated with future falls. After adjusting for fall history, only postural stability on foam was significantly associated with falls. CONCLUSIONS: When developing fall prediction models, fall history, the SPPB, and postural stability when standing on foam should be considered.

Vitamin D Supplementation and Muscle Power, Strength and Physical Performance in Older Adults: A Randomized Controlled Trial.

BACKGROUND: Low 25-hydroxyvitamin D (25[OH]D) concentrations (<30 ng/mL [<50 nmol/L]) have been associated with muscle weakness and impaired physical performance in observational studies. However, the effect of vitamin D supplementation on changes in muscle strength and physical performance in randomized controlled trials has been mixed. OBJECTIVES: To determine the effect of daily vitamin D supplementation on leg power, strength, and physical performance in low-functioning older adults with 25(OH)D concentrations of 18 to <30 ng/mL. METHODS: In this double-blind, randomized controlled trial, 136 low-functioning [Short Physical Performance Battery (SPPB) scores ≤10] adults aged 65-89 y with 25(OH)D concentrations of 18 to <30 ng/mL were randomly assigned to 2000 IU/d vitamin D3 or placebo for 12 mo. Lower-extremity leg power (primary outcome), leg and grip strength, SPPB, timed up and go (TUG), postural sway, and gait velocity and spatiotemporal parameters (secondary outcomes) were assessed at baseline, 4 and 12 mo. A subset (n = 37) also underwent a muscle biopsy at baseline and 4 mo and muscle fiber composition and contractile properties were assessed. RESULTS: Participants' mean ± SD age and SPPB scores at baseline were 73.4 ± 6.3 y and 7.8 ± 1.8, respectively. Mean ± SD 25(OH)D concentrations at baseline and 12 mo were 19.4 ± 4.2 ng/mL and 28.6 ± 6.7 ng/mL in the vitamin D group and 19.9 ± 4.9 ng/mL and 20.2 ± 5.0 ng/mL in the placebo group for a mean ± SE difference of 9.1 ± 1.1 ng/mL (P < 0.0001). However, there were no differences in change in leg power, leg or grip strength, SPPB score, TUG, postural sway, or gait velocity and spatiotemporal parameters by intervention group over 12 mo or muscle fiber composition and contractile properties over 4 mo. CONCLUSIONS: In low-functioning older adults with 25(OH)D concentrations of 18 to <30 ng/mL, randomization to 2000 IU/d vitamin D3 did not result in improvements in leg power, strength, or physical performance or muscle fiber composition and contractile properties. This trial was registered at clinicaltrials.gov as NCT02015611.

Effect of exercise modality and weight loss on changes in muscle and bone quality in older adults with obesity.

BACKGROUND: Little is known about the effect of exercise modality during a dietary weight loss program on muscle size and quality, as measured by computed tomography (CT). Even less is known about how CT-derived changes in muscle track with changes in volumetric bone mineral density (vBMD) and bone strength. METHODS: Older adults (66 ± 5 years, 64 % women) were randomized to 18-months of diet-induced weight loss (WL), WL with aerobic training (WL + AT), or WL with resistance training (WL + RT). CT-derived muscle area, radio-attenuation and intermuscular fat percentage at the trunk and mid-thigh were determined at baseline (n = 55) and 18-month follow-up (n = 22-34), and changes were adjusted for sex, baseline value, and weight lost. Lumbar spine and hip vBMD and finite element-derived bone strength were also measured. RESULTS: After adjustment for the weight lost, muscle area losses at the trunk were -7.82 cm2 [-12.30, -3.35] for WL, -7.72 cm2 [-11.36, -4.07] for WL + AT, and -5.14 cm2 [-8.65, -1.63] for WL + RT (p < 0.001 for group differences). At the mid-thigh, decreases were -6.20 cm2 [-10.39, -2.02] for WL, -7.84 cm2 [-11.19, -4.48] for WL + AT, and -0.60 cm2 [-4.14, 2.94] for WL + RT; this difference between WL + AT and WL + RT was significant in post-hoc testing (p = 0.01). Change in trunk muscle radio-attenuation was positively associated with change in lumbar bone strength (r = 0.41, p = 0.04). CONCLUSIONS: WL + RT better preserved muscle area and improved muscle quality more consistently than WL + AT or WL alone. More research is needed to characterize the associations between muscle and bone quality in older adults undertaking weight loss interventions.

Association Between Contrast Sensitivity and Physical Function in Cognitively Healthy Older Adults: The Brain Networks and Mobility Function Study.

BACKGROUND: To evaluate whether contrast sensitivity is associated with lower extremity physical function in cognitively intact older adults. METHODS: Cross-sectional analysis of the relationship of binocular and worse eye log contrast sensitivity (LCS) to expanded Short Physical Performance Battery (eSPPB) and its components (gait speed, narrow walking speed, chair stand pace, and balance) in 192 cognitively healthy older adults. The association of LCS with postural sway and gait was also tested with tasks that further challenged functional reserve. RESULTS: Mean age was 76.4 years with 56% identifying as female and over 98.5% having good corrected visual acuity. Lower LCS was significantly associated with worse performance on the eSPPB, 4-M gait speed, narrow walking speed, and balance time in unadjusted and adjusted models. The relationship between worse eye LCS and larger postural sway was 3 times greater on a foam surface (beta 1.07, 95% CI [0.35, 1.80]) than a firm surface (beta 0.35, 95% CI [0.05, 0.65]), and both were robust to adjustment for confounders; similar findings were observed with binocular LCS. Lower binocular LCS had a greater decremental effect on gait velocity during the fast pace (beta -0.58, 95% CI [-0.90, -0.27]) than the usual pace (Beta -0.39 [-0.63, -0.15]) gait task. CONCLUSIONS: These findings suggest that cognitively unimpaired older adults without significant visual acuity impairment can have subtle preclinical deficits in contrast sensitivity and physical function that could place them at risk of mobility and balance issues. Future studies should determine whether this subset of older adults may benefit from targeted intervention to prevent disability.

Performance criteria for generating predictive optimal control simulations of bicycle pedaling.

The purpose of this study was to identify one or more performance-based criteria that may be used to generate predictive optimal control simulations of submaximal pedaling. Two-legged pedaling simulations were generated based on minimizing muscle activation, muscle stress, metabolic energy, time derivative of muscle force, and minimizing metabolic energy while pedaling smoothly. The simulations based on minimizing muscle activation and muscle stress most closely matched experimental pedaling data, with the activation criterion better matching experimental muscle activation timing. We conclude that predictive simulations of submaximal pedaling may be generated using a cost function based on minimizing muscle activation.

The Virtual Short Physical Performance Battery: Psychometric Properties and Validation in Older Adults With Multiple Sclerosis.

Background: There are increasing numbers of older adults with multiple sclerosis (MS) who undergo declines in physical function that require attention of clinicians and researchers. Objective and perceived measures of disablement feasible for clinical and residential settings, such as the Short Physical Performance Battery and its virtual counterpart (vSPPB), are critical for defining the degree of disablement. Objective: We evaluated the psychometric properties and validity of the vSPPB as a measure of perceived lower extremity physical function in older adults with MS (age ≥60 years). Method: The sample included 35 older adults with MS and 35 age- and sex-matched healthy controls (age ≥60 years) who completed a battery of assessments, including the vSPPB. Results: The vSPPB performed satisfactorily in older adults with MS regarding data quality, scaling assumptions, and acceptability (i.e., psychometrics). The vSPPB further demonstrated criterion, known-groups, convergent, and discriminant construct validity. Conclusion: This report provides evidence for the validity of vSPPB scores as a measure of perceived lower extremity physical function in older adults with MS.

Relationship of Physical Function to Single Muscle Fiber Contractility in Older Adults: Effects of Resistance Training With and Without Caloric Restriction.

BACKGROUND: Previous studies support beneficial effects of both resistance exercise training (RT) and caloric restriction (CR) on skeletal muscle strength and physical performance. The goal of this study was to determine the effects of adding CR to RT on single-muscle fiber contractility responses to RT in older overweight and obese adults. METHODS: We analyzed contractile properties in 1,253 single myofiber from muscle biopsies of the vastus lateralis, as well as physical performance and thigh muscle volume, in 31 older (65-80 years), overweight or obese (body mass index = 27-35 kg/m2) men (n = 19) and women (n = 12) who were randomly assigned to a standardized, progressive RT intervention with CR (RT+CR; n = 15) or without CR (RT; n = 16) for 5 months. RESULTS: Both interventions evoked an increase in force normalized to cross-sectional area (CSA), in type-I and type-II fibers and knee extensor quality. However, these improvements were not different between intervention groups. In the RT group, changes in total thigh fat volume inversely correlated with changes in type-II fiber force (r = -.691; p = .019). Within the RT+CR group, changes in gait speed correlated positively with changes in type-I fiber CSA (r = .561; p = .030). In addition, increases in type-I normalized fiber force were related to decreases in thigh intermuscular fat volume (r = -0.539; p = .038). CONCLUSION: Single muscle fiber force and knee extensor quality improve with RT and RT+CR; however, CR does not enhance improvements in single muscle fiber contractility or whole muscle in response to RT in older overweight and obese men and women.