Contribution of Protein Intake and Concurrent Exercise to Skeletal Muscle Quality with Aging.

BACKGROUND: The use of magnetic resonance imaging (MRI) derived functional cross-sectional area (FCSA) and intramuscular adipose tissue (IMAT) to define skeletal muscle quality is of fundamental importance in order to understand aging and inactivity-related loss of muscle mass. OBJECTIVES: This study examined factors associated with lower-extremity skeletal muscle quality in healthy, younger, and middle-aged adults. DESIGN: Cross-sectional study. SETTING AND PARTICIPANTS: Ninety-eight participants (53% female) were classified as younger (20-35 years, n=50) or middle-aged (50-65 years, n=48) as well as sedentary (≤1 day per week) or active (≥3 days per week) on self-reported concurrent exercise (aerobic and resistance). MEASUREMENTS: All participants wore an accelerometer for seven days, recorded a three-day food diary, and participated in magnetic resonance imaging (MRI) of the lower limbs. Muscle cross-sectional area (CSA) was determined by tracing the knee extensors (KE) and plantar flexors, while muscle quality was established through the determination of FCSA and IMAT via color thresholding. RESULTS: One-way analysis of variance and stepwise regression models were performed to predict FCSA and IMAT. KE-IMAT (cm2) was significantly higher among sedentary (3.74 ± 1.93) vs. active (1.85 ± 0.56) and middle-aged (3.14 ± 2.05) vs. younger (2.74 ± 1.25) (p < 0.05). Protein intake (g•kg•day-1) was significantly higher in active (1.63 ± 0.55) vs. sedentary (1.19 ± 0.40) (p < 0.05). Sex, age, concurrent exercise training status, and protein intake were significant predictors of KE FCSA (R2 = 0.71, p < 0.01), while concurrent exercise training status and light physical activity predicted 33% of the variance in KE IMAT (p < 0.01). CONCLUSION: Concurrent exercise training, dietary protein intake, and light physical activity are significant determinants of skeletal muscle health and require further investigation to mitigate aging and inactivity-related loss of muscle quality.

Decreased Handgrip Strength is Associated With Impairments in Each Autonomous Living Task for Aging Adults in the United States.

OBJECTIVES: The primary purpose of this study was to determine the time-varying associations between decreased handgrip strength (HGS) and individual instrumental activities of daily living (IADL) impairments for a nationally-representative sample of aging adults in the United States. DESIGN: Longitudinal-Panel. SETTING: Detailed interviews were completed in person and core interviews were typically completed over the telephone. PARTICIPANTS: A total of 15,336 participants aged at least 50 years who participated in the 2006 wave of the Health and Retirement Study were followed biennially for 8-years. MEASUREMENTS: A hand-held dynamometer assessed HGS and performance in IADLs were self-reported. RESULTS: Every 5-kilogram decrease in HGS was associated with an increased odds ratio for the following IADL impairments: 1.11 (95% confidence interval (CI): 1.09, 1.13) for using a map, 1.10 (CI: 1.07, 1.12) for grocery shopping, 1.09 (CI: 1.05, 1.14) for taking medications, 1.07 (CI: 1.05, 1.09) for preparing hot meals, 1.06 (CI: 1.04, 1.08) for managing money, and 1.05 (CI: 1.02, 1.09) for using a telephone. CONCLUSIONS: Decreased HGS was associated with each IADL impairment, and slightly different associations were observed in individual IADL tasks for aging adults in the United States. Our findings suggest that decreased HGS, which is reflective of reduced function of the neuromuscular system, is associated with diminished performance in autonomous living tasks during aging. Losses in HGS may lead to the development of an IADL impairment. Therefore, health-care providers working with aging adults should utilize measures of HGS as a screening tool for identifying future deficits in neuromuscular functioning. Interventions designed to preserve IADLs in aging adults should also include measures of HGS for detecting early changes in IADL capacity, and intervening at the onset of HGS declines may help aging adults retain their ability to live autonomously.

The Burden of Functional Disabilities for Middle-Aged and Older Adults in the United States.

OBJECTIVES: Understanding the role of functional capacity on longevity is important as the population in the United States ages. The purpose of this study was to determine the burden of instrumental activities of daily living (IADL) and activities of daily living (ADL) disabilities for a nationally-representative sample of middle-aged and older adults in the United States. DESIGN: Longitudinal-Panel. SETTING: Core interviews were often performed in person or over the telephone. PARTICIPANTS: A sub-sample of 31,055 participants aged at least 50 years from the 1998-2014 waves of the Health and Retirement Study who reported having a functional disability were included. MEASUREMENTS: Ability to perform IADLs and ADLs were self-reported at each wave. The National Death Index was used to ascertain date of death. The number of years of life that were lost (YLLs) and years lived with a disability (YLDs) were summed for the calculation of disability-adjusted life years (DALYs). Sampling weights were used in the analyses to make the DALYs nationally-representative. The results for YLLs, YLDs, and DALYs are reported in thousands. RESULTS: Of the participants included, 14,990 had an IADL disability and 13,136 had an ADL disability. Men and women with an IADL disability had 236,037 and 233,772 DALYs, respectively; whereas, there were 178,594 DALYs for males and 253,630 DALYs for females with an ADL disability. Collectively, there were 469,809 years of healthy life lost from IADL impairments, and 432,224 years of healthy life lost from ADL limitations. CONCLUSIONS: These findings should be used to inform healthcare providers and guide interventions aiming to preserve the functional capacity of aging adults. Prioritizing health-related resources for mitigating the burden of functional disabilities may help aging adults increase their quality of life and life expectancy over time.

Unilateral lower limb suspension: integrative physiological knowledge from the past 20 years (1991-2011).

In 1991, Hans Berg and colleagues published the first research investigation using unilateral lower limb suspension (ULLS) as a human model to study the influence of unloading on skeletal muscle. ULLS requires a participant to perform all activities with axillary crutches while wearing one thick-soled shoe. The elevated shoe eliminates ground contact with the adjacent foot, thereby unloading the lower limb. Today, ULLS is a well-known ground-based analog for microgravity. The present review will synthesize the physiological findings from investigations using ULLS to study the deleterious effects of unloading. Compromised human performance and the neuromuscular, musculoskeletal and circulatory mechanisms leading to altered function will be a major emphasis of the work. Results from prolonged bed rest will also be included in order for general comparisons to be made between analogs. Finally, the efficacy of exercise to mitigate the negative consequences of unloading is presented.

Echo/Doppler and hemodynamic correlates of vasodilator responsiveness in primary pulmonary hypertension.

To determine correlates of acute vasodilator responsiveness in primary pulmonary hypertension, we retrospectively studied 25 patients, comparing 41 resting echo/Doppler and nine resting catheterization variables with the maximal reduction in pulmonary vascular resistance achieved during vasodilator trials. Twelve vasodilators were tested (mean, 5.6 drugs per patient; range, three to eight). Eight patients were vasodilator responsive, as defined by a reduction in pulmonary vascular resistance greater than or equal to 30 percent in response to at least one agent. Univariate and multivariate analyses revealed only Doppler pulmonic peak flow velocity to be an independent correlate of responsiveness (p less than 0.05). Responders differed from nonresponders in having a higher Doppler pulmonic peak flow velocity (PV) (SD 81 +/- 24 vs 64 +/- 15 cm/s; p = 0.05), lower mean right atrial pressure (RAP) (6 +/- 4 vs 13 +/- 7 mm Hg; p = 0.04), and longer median survival (37 vs 5 months; p = 0.03). Seven of eight responders had RAP less than or equal to 10 mm Hg, and all responders had PV greater than 60 cm/s. Seven of ten patients with both RAP less than or equal to 10 and PV greater than 60 and one of the 15 remaining patients were vasodilator responsive (p less than 0.001). Thus, echo/Doppler and invasive hemodynamic parameters correlate with acute vasodilator responsiveness in primary pulmonary hypertension. Patients with low PV and high RAP values were almost never vasodilator responsive. Doppler pulmonic peak velocity and mean RAP may be useful in identifying patients most likely to respond to acute vasodilator trials and those in whom testing is unlikely to yield positive results.

Two-dimensional and Doppler-echocardiographic and cardiac catheterization correlates of survival in primary pulmonary hypertension.

To determine correlates of survival in primary pulmonary hypertension, we compared 41 echocardiography-Doppler and nine catheterization parameters with outcome in 26 patients. Mean follow-up was 19.7 months in survivors; mean survival was 4.8 months in 16 nonsurvivors. Cox life-table univariate analysis correlated two echocardiographic, three Doppler, and three catheterization variables with poor survival (p less than or equal to 0.05), and chi 2 analysis ensured the best critical values: severity of pericardial effusion, heart rate of more than 87 beats/min, pulmonic flow acceleration time of less than 62 msec, tricuspid early flow deceleration (T-DEC) equal to or less than -300 cm2/sec, mitral early flow-to-atrial flow velocity ratio (M-E/A) equal to or less than 1.0, catheterization cardiac index (CI) equal to or less than 2.3 l/min/m2, mean pulmonary artery pressure of more than 61 mm Hg, and diastolic pulmonary artery pressure of more than 43 mm Hg. Multivariate life-table analysis of noninvasive variables revealed the severity of pericardial effusion to be independently significant (p = 0.006), whereas analysis of catheterization variables revealed cardiac index to be independently significant (p = 0.014). Combined multivariate analysis did not differ from the noninvasive results alone. Categorical modeling of the eight significant variables split at their critical values (present or absent) revealed M-E/A, T-DEC, and CI to be independently significant by multivariate analysis (p = 0.0014). Analysis of the five echocardiography-Doppler variables alone revealed M-E/A, T-DEC, and heart rate to be independently significant (p = 0.0016). In both cases, mortality increased with the number of critical values reached.(ABSTRACT TRUNCATED AT 250 WORDS)

Electrocardiographic diagnosis of exercise-induced left ventricular hypertrophy.

To assess the prevalence of physiologic left ventricular hypertrophy and the usefulness of ECG criteria for its diagnosis, we compared ECGs and M-mode echocardiograms from 44 ultraendurance athletes and 20 similarly aged sedentary control subjects. Left ventricular mass was elevated in 25 of 44 (57%) athletes including 17 of 29 (59%) men greater than 134 gm/m2 and 8 of 15 (53%) women greater than 110 gm/m2. The sensitivity and specificity of the three ECG criteria used to diagnose left ventricular hypertrophy were: Sokolow-Lyon voltage (S-V1 + R-V5 greater than or equal to 3.5 mV), 65% and 61%; Romhilt-Estes score (greater than or equal to 4), 16% and 84%; and Cornell voltage (R-aVL + S-V3 greater than 2.8 mV in men and greater than 2.0 mV in women), 8% and 95%, respectively. Left ventricular mass, mass index, posterior wall thickness, chamber diameter, and relative wall thickness were not related to any measurement of QRS voltage. Nonvoltage ECG criteria for left ventricular hypertrophy were rare in athletes. Thus hypertrophy is a common but not universal adaptation to exercise. It is only moderately well detected by standard voltage criteria for left ventricular hypertrophy and is not reflected in nonvoltage criteria.

Cardiac fatigue after prolonged exercise.

To determine the effects of prolonged exercise on systolic and diastolic left ventricular function, we studied 21 athletes before, at the finish (within 11 +/- 5 min), and during recovery (28 +/- 9 hr) after the Hawaii Ironman Triathlon (2.4 mile swim, 112 mile bike, 26.2 mile run). Two-dimensionally guided M mode echocardiograms were digitized for wall thickness, cavity dimension, fractional shortening, and peak rates of cavity enlargement and wall thinning. Pulsed Doppler left ventricular inflow recordings were analyzed for peak early and late velocities and their ratio. Left ventricular diastolic dimension was reduced at race finish (5.4 +/- 0.6 to 5.1 +/- 0.6 cm) and remained reduced after 1 day of recovery (5.2 +/- 0.6 cm, p less than .05). Fractional shortening fell at race finish (39 +/- 5% to 35 +/- 5%), although systolic blood pressure was unchanged, and rose to 40 +/- 4% after recovery (p less than .05). The return to prerace shortening values after recovery occurred despite continued reduction in diastolic size. Peak circumferential shortening did not change significantly. Individual reductions in fractional shortening were correlated with increases in systolic cavity size (r = -.64, p less than .01), but not with decreases in diastolic size. The stress-shortening relationship was displaced downward at race finish, but returned toward baseline after 1 day of recovery, despite a persistent reduction in cavity size. This suggests that the decrease in shortening was due to impaired contractility as well as altered preload.(ABSTRACT TRUNCATED AT 250 WORDS)

Contribution of afterload, hypertrophy and geometry to left ventricular ejection fraction in aortic valve stenosis, pure aortic regurgitation and idiopathic dilated cardiomyopathy.

To investigate the relation of left ventricular (LV) afterload, hypertrophy, geometry and systolic pump function, 17 normal persons, 24 patients with aortic stenosis (AS), 20 with aortic regurgitation (AR) and 15 with idiopathic dilated cardiomyopathy (DC) were studied. Two-dimensional echograms were used to assess end-systolic meridional and circumferential stresses and their ratio, LV mass, relative wall thickness (h/R ratio) and the ratio of LV minor axis to length, used as an index of shape. Independently obtained ejection fraction (EF) was used to determine which patients had normal (EF greater than or equal to 55%) and which had depressed (EF less than 55%) pump function. Patients with AS and low EF had similar LV mass (228 vs 215 g) but larger LV cavity (5.6 vs 4.5 cm), lower h/R ratio (0.53 vs 0.73, p less than 0.01), and therefore higher circumferential stress (336 vs 268 kdyne/cm2, p less than 0.05). Compared with normal persons, patients with DC had a lower h/R ratio (0.28 vs 0.38, p less than 0.01), higher circumferential stress (362 vs 215 kdyne/cm2, p less than 0.01) and more uniform stress distribution (meridional to circumferential stress ratio 0.57 vs 0.39, p less than 0.01), implying that meridional stress overestimates effective afterload. Afterload excess and LV shape change may be important to pump function in patients with AS or DC. In contrast, in those with AR, no significant shape differences were noted, although LV mass was higher in those with low EF (279 vs 211 g, p less than 0.05). Depressed pump function may result from impaired myocardial performance in AR without afterload excess.