A very limited amount of research has examined intermittent fasting (IF) programs, such as time-restricted feeding (TRF), in active populations. Our objective was to examine the effects of TRF, with or without β-hydroxy β-methylbutyrate (HMB) supplementation, during resistance training (RT). This study employed a randomized, placebo-controlled, reduced factorial design and was double-blind with respect to supplementation in TRF groups. Resistance-trained females were randomly assigned to a control diet (CD), TRF, or TRF plus 3 g/d HMB (TRF_HMB). TRF groups consumed all calories between 1200 h and 2000 h, whereas the CD group ate regularly from breakfast until the end of the day. All groups completed 8 wk of supervised RT and consumed supplemental whey protein. Body composition, muscular performance, dietary intake, physical activity, and physiological variables were assessed. Data were analyzed prior to unblinding using mixed models and both intention-to-treat (ITT) and per protocol (PP) frameworks. Forty participants were included in ITT, and 24 were included in PP. Energy and protein intake (1.6 g/kg/d) did not differ between groups despite different feeding durations (TRF and TRF_HMB: ∼7.5 h/d; CD: ∼13 h/d). Comparable fat-free mass (FFM) accretion (+2% to 3% relative to baseline) and skeletal muscle hypertrophy occurred in all groups. Differential effects on fat mass (CD: +2%; TRF: −2% to −4%; TRF_HMB: −4% to −7%) were statistically significant in the PP analysis, but not ITT. Muscular performance improved without differences between groups. No changes in physiological variables occurred in any group, and minimal side effects were reported. IF, in the form of TRF, did not attenuate RT adaptations in resistance-trained females. Similar FFM accretion, skeletal muscle hypertrophy, and muscular performance improvements can be achieved with dramatically different feeding programs that contain similar energy and protein content during RT. Supplemental HMB during fasting periods of TRF did not definitively improve outcomes. This study was prospectively registered at clinicaltrials.gov as NCT03404271.

This study examined (a) the validity of two accelerometers (ActiGraph GT3X [ActiGraph LLC, Pensacola, FL, USA] and activPAL [PAL Technologies Ltd., Glasgow, Scotland]) for the assessment of sedentary behavior; and (b) the variations in assessment accuracy by setting minimum sedentary bout durations against a proxy for direct observation using an automated wearable camera in free-living environments. Time spent in sedentary behavior estimated from the GT3X, with varying identification methods (i.e., a hybrid machine learning algorithm, Sojourn, and activity count thresholds), and the activPAL were compared to the criterion measure with and without applying minimum sedentary bout durations. The activPAL assessed sedentary behavior most accurately followed by GT3X with the Sojourn method. The performance of the GT3X is improved when identifying sedentary bouts ≥ 15 min with the Sojourn method or a threshold of < 150 cpm. The activPAL should be considered for studies focusing on sedentary behavior. The ability of the GT3X to assess sedentary behavior is improved when focusing on sedentary bouts ≥ 15 min using the Sojourn method or the threshold of < 150 cpm.

Cardiac rehabilitation (CR) improves survival in patients with coronary heart disease (CHD), which is largely mediated by the improvements in cardiorespiratory fitness (CRF) defined as peak oxygen consumption (VO₂). Therefore, measuring CRF is essential to predict long-term outcomes in this population. It is unclear, however, whether peak VO₂ achieved at the end of CR (END-peak VO₂) predicts survival or whether the changes of CRF achieved during CR provide a greater prognostic value. To determine whether END-peak VO₂ independently predicts long-term survival in patients with CHD undergoing CR. We also aimed at identifying cut-offs for END-peak VO₂ that could be used in clinical practice. Retrospective analysis of 853 patients with CHD referred to CR who completed a maximal cardiopulmonary exercise test. Survival analysis was performed to examine the risk of all-cause mortality (average follow-up years: 6.65) based on peak VO₂. The Contal and O’Quigley’s method was used to determine the optimal cut-off of END-peak VO₂ based on the log-rank statistic. END-peak VO₂ was inversely associated with mortality risk [hazard ratio (HR) = 0.84; 95% confidence interval (CI) = 0.78–0.90], independent of changes in peak VO₂ adjusted for the baseline peak VO₂. The estimated cut-off of END-peak VO₂ at ≥17.6 mL/kg/min best predicted the survival with high predictive accuracy and patients with END-peak VO₂ under the cut-off had a greater risk of mortality (HR = 2.93; 95% CI = 1.81–4.74). In patient with CHD undergoing CR, END-peak VO₂ is an independent predictor for long-term survival. Studies utilizing higher intensity CR programmes, with and without pharmacologic strategies, to increase peak VO₂ to a greater degree in those achieving a suboptimal END-peak VO₂, are urgently needed.

Accelerometer-based activity monitors are widely used in research and surveillance applications for quantifying sedentary behavior (SB) and physical activity (PA). Considerable research has been done to refine methods for assessing PA, but relatively little attention has been given to operationalizing SB parameters (i.e., sedentary time and breaks) from accelerometer data - particularly in relation to health outcomes. This study investigated: (a) the accrued patterns of sedentary time and breaks; and (b) the associations of sedentary time and breaks in different bout durations with cardiovascular risk factors. Accelerometer data on 5,917 adults from the National Health Examination and Nutrition Survey (NHANES) 2003–2006 were used. Sedentary time and breaks at different bout durations (i.e., 1, 2–4, 5–9, 10–14, 15–19, 20–24, 25–29, and ≥30-min) were obtained using a threshold of <100 counts per minute. Sedentary time and breaks were regressed on cardiovascular risk factors (waist circumference, triglyceride, and high-density lipoprotein cholesterol) and body mass index across bout durations. The results revealed that the majority of sedentary time occurred within relatively short bout durations (≈70% and ≈85% for <5-min and <10-min, respectively). The associations of sedentary time and breaks with health outcomes varied depending on how bout time was defined. Estimates of SB parameters based on bout durations of 5 min or shorter were associated with reduced cardiovascular risk factors while durations longer than 10-min were generally associated with increased risk factors. The present study demonstrates that the duration of sedentary bouts should be further considered when operationalizing the SB parameters from accelerometer data. The threshold of 5 minutes to define a bout is defensible, but a 10 minute threshold would provide a more conservative estimate to clearly capture the prolonged nature of sedentary behavior. Additional research is needed to determine the relative sensitivity and specificity of these thresholds.

Background: Sarcopenia impairs cardiorespiratory fitness (CRF) in patients with heart failure with reduced ejection fraction (HFrEF). Obesity has also been shown to impair CRF; however, the effects of sarcopenia on CRF in patients with obesity and HFrEF are unknown. The aim of this analysis was to examine differences in CRF between patients with sarcopenic obesity (SO) and non-SO (NSO) with HFrEF. We also assessed associations between skeletal muscle mass index (SMMI) and CRF. Methods: Forty patients with HFrEF and obesity underwent cardiopulmonary exercise testing to collect measures of CRF including peak oxygen consumption (VO ₂ ), circulatory power, oxygen uptake efficiency slope, O ₂ pulse, and exercise time. Body composition was performed in all patients using bioelectrical impedance analysis to quantify fat mass index and divide patients into SO and NSO based on SMMI cutoffs. Results are presented as mean (SD) or median [interquartile range] as appropriate. Results: Nearly half (43% [n=17]) of patients had SO. Patients with SO had a lower SMMI than those with NSO, and no differences in fat mass index were observed between groups. Those with SO achieved a lower absolute peak VO ₂ (NSO, 1.62±0.53 L·min ^-1 versus SO, 1.27±0.44 L·min ^-1 , P =0.035), oxygen uptake efficiency slope (NSO, 1.92±0.59 versus SO, 1.54±0.48, P =0.036), and exercise time (NSO, 549±198 seconds versus SO, 413±140 seconds, P =0.021) compared to those with NSO. On multivariate analysis, SMMI remained a significant predictor of absolute peak VO ₂ when adjusted for age, sex, adiposity, and HF severity. Conclusions: In patients with HFrEF and obesity, sarcopenia, defined as low SMMI, is associated with a clinically significant reduction in CRF, independent of adiposity.

Gender disparities in chronic pain are well documented in the literature. However, little is known regarding the relationship between physical activity (PA) and gender disparities in chronic pain. This study described gender differences in prevalence of chronic pain and PA, and identified a type of leisure time PA that individuals frequently chose in a nationally representative sample of US adults (N = 14,449). Data from the National Health Nutrition Examination Survey 1999–2004 were analyzed. Individuals were categorized into no chronic pain (NCP), localized chronic pain (LCP), and widespread chronic pain (WCP) groups based on responses to a pain questionnaire. A self-report PA questionnaire was used to estimate the time spent in different types of PA. Women showed higher prevalence of LCP and WCP compared to men. Men spent more hours per week for leisure time PA compared to women, but men and women showed similar prevalence of sufficient PA to meet a PA recommendation (≥150 min/week of moderate-to-vigorous intensity PA) across chronic pain categories. However, the prevalence of sufficient PA was substantially higher among men and women with NCP compared to men and women with LCP and WCP. Additionally, both men and women chose walking as the primary type of leisure time PA. Together, gender disparities exist in the prevalence of chronic pain and hours spent for leisure time PA. More research is needed to explore the role of increasing leisure time PA, such as walking, in reducing gender disparities in chronic pain.