Rodrigo Villar

Purpose: To evaluate the effect of bodyweight interval training on frailty status in older adults. Methods: A randomized controlled trial was conducted with 60 frail older adults (74.0 ± 6.0 years; 72.4% women). Participants were allocated to bodyweight interval training (BWIT = 30) for 24 weeks or to a control group (CG = 30) instructed to maintain their usual physical activities. Frailty status (Fried phenotype), physical-functional performance, cardiohemodynamic responses, and body composition were assessed at baseline and after 12 and 24 weeks. Longitudinal effects were analyzed using linear mixed-effects models and categorical between-group comparisons. Results: BWIT was associated with a higher probability of transition to less frail states over 24 weeks (p < 0.001), whereas the control group remained stable. Significant effects were observed in the intervention group (OR = 15.44; p = 0.006) and over time at 12 weeks (OR = 4.96; p = 0.005) and 24 weeks (OR = 15.24; p < 0.001). BWIT improved knee extension strength, five-times sit-to-stand performance, gait speed, and reduced blood pressure parameters (p < 0.001), with no relevant changes in body composition. Conclusion: BWIT was effective in modifying frailty status in older adults over 24 weeks and may represent a feasible and accessible strategy for frailty management in primary health care. Trial registration: RBR-23t5jbh (Brazilian Registry of Clinical Trials), registered September 4, 2024, retrospectively registered.

Active postural transitions impose rapid orthostatic stress that requires coordinated cardiovascular compensation. Whether the magnitude and timing of these responses differ by gravitational load, age, and sex during common daily movements remains unclear. This study compared short-term cardiovascular regulation during sit-to-stand (lower gravitational load) and lie-to-stand (higher gravitational load) transitions in younger and older adults. Fifty-six healthy participants (younger and older females and males; n = 14 per group) completed both transitions in a randomized, counterbalanced design. Beat-to-beat blood pressure and hemodynamic responses were assessed at baseline, immediately on standing, and across four predefined compensatory phases. General linear models examined the effects of condition, age, sex, and age-sex interactions, with cardiovascular medication included as a covariate. Lie-to-stand elicited larger immediate reductions in systolic, diastolic, and mean arterial pressure, alongside greater heart rate increases, compared with sit-to-stand (all p < 0.001). Older adults demonstrated larger drops in blood pressure and systemic vascular resistance, and blunted heart rate and cardiac output responses, particularly under higher gravitational load. In contrast, older adults maintained relatively higher stroke volume during lie-to-stand, suggesting greater reliance on mechanical compensation. Sex-related differences were condition-specific: younger males exhibited higher cardiac output during sit-to-stand, while older females showed higher late-phase mean arterial pressure and vascular resistance during lie-to-stand. These findings indicate that gravitational load strongly influences short-term cardiovascular compensation during active standing and amplifies age-related differences. Sit-to-stand and lie-to-stand transitions provide complementary information, highlighting the importance of considering transition type when evaluating orthostatic cardiovascular regulation.

Background: Frailty is a multifactorial condition that significantly impacts older adults’ health and independence, which can be mitigated through training. This study examined the effects of a 12-week progressive strength training (PST) program on frailty status and short-term autonomic compensatory responses during postural transitions. Methods: Eight older adults (60–79 years) classified as pre-frail or frail according to the frailty index (FI) participated in a 12-week PST program. Time and frequency-domain heart rate variability (HRV) in the supine position, cardiac parasympathetic modulation (CPM) determined from the HR 30:15 ratio (longest RR interval around the 30th heartbeat divided by the shortest RR interval around the 15th heartbeat after standing), and cardiac baroreceptor gain (CBG) assessed as the ratio of heart rate change to systolic blood pressure drop (ΔHR/ΔSBP) at 30, 60, 180, and 420 s after standing were assessed at pre-test, 8 weeks and 12 weeks (autonomic function outcomes). Physical activity levels (PAL), handgrip strength (HGS), and gait speed (GS) were assessed, and orthostatic intolerance (OI) symptoms were self-reported at pre-test, 8 weeks, and 12 weeks. Results: After 12 weeks of PST, FI scores decreased from 0.18 to 0.04 (78% reduction). PAL, HGS, and GS improved by 152%, 13%, and 11%, respectively. Three of eight participants reported OI symptoms at pre-test, with no reported symptoms at week 12. Despite this, PST did not enhance short-term autonomic responses. Conclusions: PST counteracted frailty and improved physical and muscular function but did not enhance indices of short-term autonomic regulation in frail older people.

Intensive care unit-acquired weakness (ICU-AW) research focuses predominantly on intrinsic muscle pathology rather than integrated systemic interactions, which are commonly studied in exercise science. Peak oxygen uptake (V˙O2peak), V˙O2 on/off kinetics, and skeletal muscle oxygenation provide a quantitative evaluation of exercise capacity and are infrequently measured in intensive care unit (ICU) survivors. Routine cardiopulmonary exercise test (CPET) research separates V˙O2peak and V˙O2 kinetics assessments into multiple sessions. Yet, a combined experimental approach may enhance diagnosis, follow-up retention, and mechanistic insight for patients with ICU-AW. This prospective cross-sectional observational study aims to develop a standardized, single-session CPET protocol for combined assessment of V˙O2peak, V˙O2 kinetics, and skeletal muscle microvascular oxygenation in ICU survivors, enabling quantitative and integrated assessment of ICU-AW. Adults mechanically ventilated for ≥7 days will be recruited to participate 6 months post-ICU discharge in a modified CPET exercise session on an upright cycle ergometer. The proposed standardization will involve (1) the estimation of V˙O2peak using a priori formulas with a V˙O2peak correction factor for the ICU population, (2) V˙O2 on-kinetics (constant work rate) targeting relative 30% V˙O2reserve, (3) an incremental ramp exercise based on self-reported functional status, and (4) a 10-minute recovery to quantify V˙O2 off-kinetics. In addition, near-infrared spectroscopy will be placed on the vastus lateralis muscle to simultaneously collect tissue saturation index and deoxyhemoglobin during each phase of the protocol. Recruitment is anticipated to begin in June 2026 and is expected to be completed in 2029/2030. The anticipated sample size will be approximately 48 participants based on the feasibility of recruiting 1 participant per month and a sample size calculation based on Bland-Altman limits of agreement between predicted and measured V˙O2peak. The intensive care unit combined assessment of cardiorespiratory exercise (ICU-CARE) CPET protocol will enable the quantitative evaluation of V˙O2peak, V˙O2 on/off kinetics, and local microvascular skeletal muscle oxygenation during a single exercise session, facilitating the integrated physiological study of ICU-AW.

BACKGROUND ICU-acquired weakness (ICU-AW) research focuses predominantly on intrinsic muscle pathology rather than integrated systemic interactions, commonly studied in exercise science. Peak oxygen uptake (V ̇O_2peak), V ̇O_2 on/off kinetics, and skeletal muscle oxygenation provide quantitative evaluation of exercise capacity, and are infrequently measured in ICU survivors. Routine cardiopulmonary exercise test (CPET) research separates V ̇O_2peak and V ̇O_2 kinetics assessments into multiple sessions. Yet, a combined experimental approach may enhance diagnosis, follow-up retention, and mechanistic insight for patients with ICU-AW. OBJECTIVE This prospective cross-sectional observational study aims to develop a standardized, single-session CPET protocol for combined assessment of V ̇O_2peak, V ̇O_2 kinetics, and skeletal muscle microvascular oxygenation in ICU survivors, enabling quantitative and integrated assessment of ICU-AW. METHODS Adults mechanically ventilated ≥ 7 days will be recruited to participate 6 months post-ICU discharge, in a modified CPET exercise session on an upright cycle ergometer. The proposed standardization will involve (i) the estimation of V ̇O_2peak using a priori formulae with a V ̇O_2peak correction factor for the ICU population, (ii) V ̇O_2 on-kinetics (constant-work-rate [CWR]) targeting relative 30% V ̇O_2reserve, (iii) an incremental ramp exercise based on self-reported functional status, and (iv) a 10-minute recovery to quantify V ̇O_2 off-kinetics. In addition, near-infrared spectroscopy (NIRS) will be placed on the vastus lateralis muscle to simultaneously collect tissue saturation index (TSI) and deoxy-hemoglobin (HHb) during each phase of the protocol. RESULTS Recruitment is anticipated to begin in June 2026, and is expected to be completed in 2028. Anticipated sample size will be approximately 25 participants based on convenience sampling and recruitment of 1 participant per month. CONCLUSIONS The ICU-CARE CPET protocol will enable the quantitative evaluation of V ̇O_2peak, V ̇O_2 on/off kinetics, and local microvascular skeletal muscle oxygenation during a single exercise session, facilitating the integrated physiological study of ICU-AW. CLINICALTRIAL Registered at clinicaltrials.gov under the clinical study ID NCT06193980

Background: Frailty is a multifactorial condition that significantly impacts older adults' health and independence, which can be mitigated through training. This study examined the effects of a 12-week progressive strength training (PST) program on frailty status and short-term autonomic compensatory responses during postural transitions. Methods: Eight older adults (60-79 years) classified as pre-frail or frail according to the frailty index (FI) participated in a 12-week PST program. Time and frequency-domain heart rate variability (HRV) in the supine position, cardiac parasympathetic modulation (CPM) determined from the HR 30:15 ratio (longest RR interval around the 30th heartbeat divided by the shortest RR interval around the 15th heartbeat after standing), and cardiac baroreceptor gain (CBG) assessed as the ratio of heart rate change to systolic blood pressure drop (ΔHR/ΔSBP) at 30, 60, 180, and 420 seconds after standing were assessed at pre-test, 8 weeks and 12 weeks (autonomic function outcomes). Physical activity levels (PAL), handgrip strength (HGS), and gait speed (GS) were assessed, and orthostatic intolerance (OI) symptoms were self-reported at pre-test, 8 weeks, and 12 weeks. Results: After 12 weeks of PST, FI scores decreased from 0.18 to 0.04 (78% reduction). PAL, HGS, and GS improved by 152%, 13%, and 11%, respectively. Three of eight participants reported OI symptoms at pre-test, with no reported symptoms at week 12. Despite this, PST did not enhance short-term autonomic responses. Conclusion: PST counteracted frailty and improved physical and muscular function but did not enhance indices of short-term autonomic regulation in frail older people.

Background: Tachycardia after mild activity or during rest is a common complaint among people with post-COVID-19 condition (PCC). Understanding the relationships between heart rate (HR) and physical activity (PA) in this population is crucial for developing appropriate rehabilitation protocols. Objective: To investigate the associations between HR and PA in individuals with PCC, accounting for Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) symptoms. Design: Observational study. Subjects: Sixteen adults with PCC (81% females, mean age 51 ± 12 years). Methods: Participants were instructed to use 2 wearable devices (Garmin smartwatch and ActiGraph accelerometer) during waking hours over 4 days while performing daily activities. Average HR, percentage of time in tachycardia (time with HR > 100 bpm), and daily step count were assessed. The accelerometer counts per minute was used to categorize daily PA as sedentary, light intensity, and moderate-to-vigorous (MVPA). Results: Participants wore the watches and accelerometers for a mean of 11.36 ± 2.60 and 12.51 ± 1.94 h per day, respectively. Average daily HR increased with increasing PA levels from sedentary to MVPA. However, the percentage of time in tachycardia was significantly lower during periods of MVPA compared with sedentary periods, even after adjusting for ME/CFS symptoms. Conclusion: Individuals with PCC in our study experienced more tachycardia during periods of minimal physical activity compared with periods categorized as MVPA.

Background/Objectives: Individuals experiencing long COVID (LC) frequently report orthostatic intolerance symptoms, which may be linked to autonomic and cardiovascular dysfunction. The active standing test provides a simple, clinically relevant means to assess these impairments. This systematic review aims to determine the use of the active standing orthostatic stress test in evaluating cardiovascular, autonomic, and respiratory responses in people experiencing LC. Methods: A systematic search, according to PRISMA guidelines, was conducted in PubMed, MEDLINE, EMBASE, CINAHL, and Scopus for articles published between 2020 and 2025. This study was registered in PROSPERO CRD-42024615872. Studies were included if they used the active standing test, enrolled adults (≥18 years), included both long COVID and healthy control groups, used continuous beat-to-beat measurements, and reported physiological outcomes. Risk of bias was assessed using the nine-point Newcastle–Ottawa Scale. Results: Three studies (216 participants experiencing LC and 186 controls) met the inclusion criteria. Across studies, LC individuals consistently exhibited elevated heart rate in both supine and standing positions. However, blood pressure findings were more variable: only one study reported 13% of participants met orthostatic hypotension criteria, while another found significant increases in diastolic blood pressure during standing. Long COVID groups also showed reduced heart rate variability compared to controls. Conclusions: Individuals experiencing LC show elevated heart rate and impaired autonomic function during active standing, with subgroup-specific blood pressure changes. These alterations may contribute to dizziness, fatigue, and reduced activity tolerance. Incorporating active standing into clinical assessment could aid early identification of autonomic dysfunction and inform rehabilitation strategies, though more research is urgently needed.

Background. Frailty is a multifactorial condition that significantly impacts older adults' health and independence, which can be mitigated through training. This study examined the effects of a 12-week progressive strength training (PST) program on frailty status and short-term autonomic compensatory responses during postural transitions. Methods: Eight older adults (60-79 years) classified as pre-frail or frail according to the frailty index (FI) participated in a 12-week PST program. Time and frequency-domain heart rate varia-bility (HRV) in the supine position, cardiac parasympathetic modulation (CPM) deter-mined from the HR 30:15 ratio (longest RR interval around the 30th heartbeat divided by the shortest RR interval around the 15th heartbeat after standing), and cardiac baroreceptor gain (CBG) assessed as the ratio of heart rate change to systolic blood pressure drop (ΔHR/ΔSBP) at 30, 60, 180, and 420 seconds after standing were assessed at pre-test, 8 weeks and 12 weeks (autonomic function outcomes). The level of physical activity (LPA), handgrip strength (HGS), and gait speed (GS) were assessed, and orthostatic intolerance (OI) symptoms were self-reported at pre-test, 8 weeks and 12 weeks. Results: After 12 weeks of PST, FI scores decreased from 0.18 to 0.04 (78% reduction). LPA, HGS, and GS improved by 152%, 13%, and 11%, respectively. Three of eight participants reported OI symptoms at pre-test, with no reported symptoms at week 12. Despite this, PST did not enhance short-term autonomic responses. Conclusion: PST counteracted frailty and im-proved physical and muscular function but did not enhance indices of short-term auto-nomic regulation in frail older people.