Chronotropic Incompetence among People with HIV Improves with Exercise Training in the Exercise for Healthy Aging Study.

BACKGROUND: People with HIV (PWH) have lower exercise capacity compared to peers without HIV, which may be explained by chronotropic incompetence (CI), the inability to increase heart rate during exercise. METHODS: The Exercise for Healthy Aging Study included adults ages 50-75 with and without HIV. Participants completed 12 weeks of moderate intensity exercise, before randomization to moderate or high intensity for 12 additional weeks. We compared adjusted heart rate reserve (AHRR; CI <80%) on cardiopulmonary exercise testing by HIV serostatus and change from baseline to 12 and 24 weeks using mixed effects models. RESULTS: Among 32 PWH and 37 controls (median age 56, 7% female, mean BMI 28 kg/m2), 28% of PWH compared to 11% of controls had CI at baseline (p = 0.067). AHRR was lower among PWH (91 vs 101%; difference 10%, 95% CI 1.9-18.9; p = 0.02). At week 12, AHRR normalized among PWH (+8%, 95% CI 4-11; p < 0.001) and was sustained at week 24 (+5, 95%CI 1-9; p = 0.008) compared to no change among controls (95%CI -4 to 4; p = 0.95; pinteraction = 0.004). After 24 weeks of exercise, only 15% PWH and 10% of controls had CI (p = 0.70). CONCLUSIONS: Chronotropic incompetence contributes to reduced exercise capacity among PWH and improves with exercise training.

Chronotropic Incompetence among People with HIV Improves with Exercise Training in the Exercise for Healthy Aging Study.

Background: People with HIV (PWH) have lower exercise capacity compared to HIV-uninfected peers, which may be explained by chronotropic incompetence (CI), the inability to increase heart rate during exercise. Methods: The Exercise for Healthy Aging Study included adults ages 50-75 with and without HIV. Participants completed 12 weeks of moderate intensity exercise, before randomization to moderate or high intensity for 12 additional weeks. We compared adjusted heart rate reserve (AHRR; CI <80%) on cardiopulmonary exercise testing by HIV serostatus, and change from baseline to 12 and 24 weeks using mixed effects models. Results: Among 32 PWH and 37 controls (median age 56, 7% female, mean BMI 28 kg/m2), 28% of PWH compared to 11% of controls had CI at baseline (p=0.067). AHRR was lower among PWH (91 vs 102%; difference 11%, 95% CI 2.5-19.7; p=0.01). At week 12, AHRR normalized among PWH (+8%, 95% CI 4-11; p<0.001) and was sustained at week 24 (+5, 95%CI 1-9; p=0.008) compared to no change among controls (95%CI -4 to 4; p=0.95; pinteraction=0.004). After 24 weeks of exercise, only 15% PWH and 10% of controls had CI (p=0.70). Conclusions: Chronotropic incompetence contributes to reduced exercise capacity among PWH and improves with exercise training.

Elevated liver glycogenolysis mediates higher blood glucose during acute exercise in Barth syndrome.

Barth syndrome (BTHS) is an X-linked recessive genetic disorder due to mutations in the Tafazzin (TAFAZZIN) gene that lead to cardiac and skeletal muscle mitochondrial dysfunction. Previous studies in humans with BTHS demonstrate that the defects in muscle mitochondrial oxidative metabolism result in an enhanced reliance on anaerobic metabolism during exercise to meet energy demands of muscular work. During exercise, the liver normally increases glucose production via glycogenolysis and gluconeogenesis to match the elevated rate of muscle glucose uptake and meet the ATP requirements of working muscle. However, the impact of Tafazzin deficiency on hepatic glucose production and the pathways contributing to hepatic glucose production during exercise is unknown. Therefore, the purpose of this study was to quantify in vivo liver gluconeogenesis and glycogenolysis in Tafazzin knockdown mice at rest and during acute exercise. METHODS: Male TAFAZZIN shRNA transgenic (TG) and wild-type (WT) mice completed exhaustive treadmill running protocols to test exercise tolerance. Mice underwent 2H- and 13C-stable isotope infusions at rest and during a 30-minute treadmill running bout to quantify hepatic glucose production and associated nutrient fluxes under sedentary conditions and during acute exercise. Circulating and tissue (skeletal muscle and liver) samples were obtained during and following exercise to assess static metabolite levels. RESULTS: TG mice reached exhaustion sooner during exhaustive treadmill running protocols and exhibited higher plasma lactate concentrations after exhaustive exercise compared to WT mice. Arterial glucose levels were comparable between genotypes at rest, but higher in TG mice compared to WT mice during exercise. Consistent with the higher blood glucose, TG mice showed increased endogenous glucose production owing to elevated glycogenolysis compared to WT mice during exercise. Total gluconeogenesis, gluconeogenesis from glycerol, gluconeogenesis from phosphoenolpyruvate, pyruvate cycling, total cataplerosis, and anaplerotic fluxes were similar between TG and WT mice at rest and during exercise. However, lactate dehydrogenase flux and TCA cycle fluxes trended higher in TG mice during exercise. Liver glycogen content in TG was higher in TG vs. controls. CONCLUSION: Our data in the Tafazzin knockdown mouse suggest that elevated anaerobic metabolism during rest and exercise previously reported in humans with BTHS are supported by the finding of higher hepatic glycogenolysis.

The use of non-invasive imaging modalities for the assessment of skeletal muscle quantity and quality in people with HIV: A narrative review.

BACKGROUND: People with HIV (PWH) are prone to mobility impairments and physical dysfunction, with the loss of skeletal muscle quantity and quality being a major contributor to the dysfunction. Assessment of skeletal muscle is an important component of care for this patient population for early intervention and treatment. The use of non-invasive imaging techniques to evaluate skeletal muscle, such as dual X-ray absorptiometry, computer tomography and magnetic resonance imaging, has increased in popularity in recent years. PURPOSE: This narrative review synthesizes the use of these techniques and summarizes the associations between outcomes from these imaging modalities and physical function in PWH.

Severity of functional impairments by race and sex in older patients hospitalized with acute decompensated heart failure.

BACKGROUND: Older patients hospitalized with acute decompensated heart failure (ADHF) have marked functional impairments, which may contribute to their delayed and incomplete recovery and persistently poor outcomes. However, whether impairment severity differs by race and sex is unknown. METHODS: REHAB-HF trial participants (≥60 years) were assessed just before discharge home from ADHF hospitalization. Physical function [Short Physical Performance Battery; 6-min walk distance (6MWD)], frailty (Fried criteria), cognition [Montreal Cognitive Assessment (MoCA)], quality-of-life [Kansas City Cardiomyopathy Questionnaire, Short-Form-12, EuroQol-5D-5L], and depression [Geriatric Depression Scale (GDS)] were examined by race and sex. RESULTS: This prespecified subgroup cross-sectional analysis included 337 older adults (52% female, 50% Black). Black participants were on average younger than White participants (70.3 ± 7.2 vs. 74.7 ± 8.3 years). After age, body mass index, ejection fraction, comorbidity, and education adjustment, and impairments were similarly common and severe across groups except: Black male and Black and White female participants had more severely impaired walking function compared with White male participants [6MWD (m) 187 ± 12, 168 ± 9170 ± 11 vs. 239 ± 9, p < 0.001]; gait speed (m/s) (0.61 ± 0.03, 0.56 ± 0.02, 0.55 ± 0.02 vs. 0.69 ± 0.02, p < 0.001); White female participants had the highest frailty prevalence (72% vs. 47%-51%, p = 0.007); and Black participants had lower MoCA scores compared with White participants (20.9 ± 4.5 vs. 22.8 ± 3.9, p < 0.001). Depressive symptoms were common overall (43% GDS ≥5), yet underrecognized clinically (18%), especially in Black male participants compared with White male participants (7% vs. 20%). CONCLUSION: Among older patients hospitalized for ADHF, frailty and functional impairments with high potential to jeopardize patient HF self-management, safety, and independence were common and severe across all race and sex groups. Impairment severity was often worse in Black participant and female participant groups. Formal screening across frailty and functional domains may identify those who may require greater support and more tailored care to reduce the risk of adverse events and excess hospitalizations and death.

Examining the Accuracy of the Polar A360 Monitor.

ABSTRACT: Rider, BC, Conger, SA, Ditzenberger, GL, Besteman, SS, Bouret, CM, and Coughlin, AM. Examining the accuracy of the Polar A360 monitor. J Strength Cond Res 35(8): 2165-2169, 2021-The purpose of this study was to determine the accuracy of the Polar A360 heart rate (HR) monitor during periods of rest, walking/running, and active/passive recovery from exercise. Thirty collegiate athletes (women n = 15 and men n = 15) wore an A360 monitor and a previously validated chest HR monitor (Polar RS400) that served as the criterion measurement across a range of resting and walking/running intensities. First, subjects rested in a supine, seated, and standing position. Next, each subject walked on a treadmill at 1.6 kilometers per hour (kph). Speed was increased by 1.6 kph every 2 minutes until volitional fatigue. Then, subjects walked at 4.8 kph followed by a seated recovery stage. Heart rate was recorded in 30-second increments. Total mean difference in HR readings, percent accuracy, and intraclass correlation coefficient (ICC) analysis established the level of agreement between devices. Bland-Altman plots and a regression were used to examine the agreement between devices. The A360 demonstrated a strong correlation with the RS400 (r2 = 0.98) across time points. The analysis of variance with repeated measures indicated an overall significant difference (p < 0.001) between devices. The A360 significantly underestimated HR during the 6.4-kph speed only (p < 0.05) (effect size 0.26). The greatest percent accuracy occurred during rest (91%) and recovery (90%). An ICC of 0.98 (SEM: 0.35) demonstrates a strong level of agreement between devices. The A360 is accurate at rest and during various walking and running speeds and thus is a device that can be used with confidence by athletes for specific training purposes. Future research should examine accuracy during weight training and other sport-specific activities.