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The human heart is very adaptable, with chamber size, wall thickness and ventricular stiffness all modified by periods of inactivity or exercise training. Herein, we summarize the cardiac adaptations induced by changes in physical activity, ranging from bed rest and spaceflight to endurance exercise training, while also highlighting how the ageing process (a long-term model of inactivity) affects cardiac plasticity. Severe inactivity during bed rest or spaceflight leads to cardiac atrophy and ventriculo-vascular stiffening. Conversely, endurance training induces eccentric hypertrophy and enhances ventricular compliance, and can be used as an effective countermeasure to prevent adverse cardiac changes during prolonged periods of bed rest or spaceflight. With sedentary ageing, the heart undergoes concentric remodelling and irreversibly stiffens at advanced age. Specifically, older adults who initiate endurance training later in life are unable to improve ventricular compliance and diastolic function, suggesting reduced cardiac plasticity with advanced age; however, lifelong exercise training prevents age-associated cardiac remodelling and maintains cardiac compliance of older adults at a level similar to those of younger healthy individuals. Nevertheless, there are still many knowledge gaps related to cardiac remodelling and changes in cardiac function induced by bed rest, exercise training and spaceflight, as well as how these different stimuli may interact with advancing age. Future studies should focus on understanding what factors (sex, age, heritability, etc.) may influence the heart's responsiveness to training or deconditioning, as well as understanding the long-term cardiac consequences of spaceflight beyond low-Earth orbit with the added stimulus of galactic cosmic radiation.
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Bedrest as an experimental paradigm or as an in-patient stay for medical reasons has negative consequences for cardiovascular health. The effects of severe inactivity parallel many of the changes experienced with natural aging but over a much shorter duration. Cardiac function is reduced, arteries stiffen, neural reflex responses are impaired, and metabolic and oxidative stress responses impose burden on the heart and vascular systems. The effect of these changes is revealed in studies of integrative function. Aerobic fitness progressively deteriorates with bedrest and tolerance of upright posture is rapidly impaired. In this review we consider the similarities of aging and bedrest-induced cardiovascular deconditioning. We concur with many recent clinical recommendations that early and regular mobility with upright posture will reduce likelihood of hospital-associated disability related to bedrest.
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Reposo en Cama , Humanos , Reposo en Cama/efectos adversos , Enfermedades Cardiovasculares/fisiopatología , Enfermedades Cardiovasculares/etiología , Envejecimiento Prematuro/fisiopatología , Envejecimiento Prematuro/etiología , Descondicionamiento Cardiovascular/fisiología , Envejecimiento/fisiologíaRESUMEN
Blood volume shifts during postural adjustment lead to irregular distension of the internal jugular vein (IJV). In microgravity, distension may contribute to flow stasis and thromboembolism, though the regional implications and associated risk remain unexplored. We characterized regional differences in IJV volume distension and flow complexity during progressive head-down tilt (HDT) (0°, -6°, -15°, -30°) using conventional ultrasound and vector flow imaging. We also evaluated low-pressure thigh cuffs (40 mmHg) as a fluid shifting countermeasure during -6° HDT. Total IJV volume expanded 139 ± 95% from supine position (4.6 ± 2.7 mL) to -30° HDT (10.3 ± 5.0 mL). Blood flow profiles had greater vector uniformity at the cranial IJV region (P < 0.01) and became more dispersed with increasing tilt (P < 0.01). Qualitatively, flow was more uniform throughout the IJV during its early flow cycle phase and more disorganized during late flow phase. This disorganized flow was accentuated closer to the vessel wall, near the caudal region, and during greater HDT. Low-pressure thigh cuffs during -6° HDT decreased IJV volume at the cranial region (-12 ± 15%; P < 0.01) but not the caudal region (P = 0.20), although flow uniformity was unchanged (both regions, P > 0.25). We describe a distensible IJV accommodating large volume shifts along its length. Prominent flow dispersion was primarily found at the caudal region, suggesting multidirectional blood flow. Thigh cuffs appear effective for decreasing IJV volume but effects on flow complexity are minor. Flow complexity along the vessel length is likely related to IJV distension during chronic volume shifting and may be a precipitating factor for flow stasis and future thromboembolism risk.NEW & NOTEWORTHY The internal jugular vein (IJV) facilitates cerebral outflow and is sensitive to volume shifts. Concerns about IJV expansion and fluid flow behavior in astronauts have surfaced following thromboembolism reports. Our study explored regional volume distension and blood flow complexity in the IJV during progressive volume shifting. We observed stepwise volume distension and increasing flow dispersion with head-down tilting across all regions. Flow dispersion may pose a risk of future thromboembolism during prolonged volume shifts.
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Inclinación de Cabeza , Venas Yugulares , Humanos , Venas Yugulares/fisiología , Venas Yugulares/diagnóstico por imagen , Masculino , Inclinación de Cabeza/fisiología , Adulto , Femenino , Volumen Sanguíneo/fisiología , Adulto Joven , Flujo Sanguíneo Regional/fisiología , Velocidad del Flujo Sanguíneo/fisiología , Ultrasonografía/métodosRESUMEN
Human skeletal hemodynamics remain understudied. Neither assessments in weight-bearing bones during walking nor following periods of immobility exist, despite knowledge of altered nutrient-artery characteristics after short-duration unloading in rodents. We studied 12 older adults (8 females, aged 59 ± 3 years) who participated in ambulatory near-infrared spectroscopy (NIRS) assessments of tibial hemodynamics before (PRE) and after (POST) 14 days of head-down bed rest (HDBR), with most performing daily resistance and aerobic exercise countermeasures during HDBR. Continual simultaneous NIRS recordings were acquired over the proximal anteromedial tibial prominence of the right lower leg and ipsilateral lateral head of the gastrocnemius muscle during supine rest, walking, and standing. During 10 minutes of walking, desaturation kinetics in the tibia were slower (time to 95% nadir values 125.4 ± 56.8 s versus 55.0 ± 30.1 s, p = 0.0014). Tibial tissue saturation index (TSI) immediately fell (-9.9 ± 4.55) and did not completely recover by the end of 10 minutes of walking (-7.4 ± 6.7%, p = 0.027). Upon standing, total hemoglobin (tHb) kinetics were faster in the tibia (p < 0.0001), whereas HDBR resulted in faster oxygenated hemoglogin (O2Hb) kinetics in both tissues (p = 0.039). After the walk-to-stand transition, changes in O2Hb (p = 0.0022) and tHb (p = 0.0047) were attenuated in the tibia alone after bed rest. Comparisons of NIRS-derived variables during ambulation and changes in posture revealed potentially deleterious adaptations of feed vessels after HDBR. We identify important and novel tibial hemodynamics in humans during ambulation before and after bed rest, necessitating further investigation. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.
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Prolonged bedrest provokes orthostatic hypotension and intolerance of upright posture. Limited data are available on the cardiovascular responses of older adults to head-up tilt following bedrest, with no studies examining the potential benefits of exercise to mitigate intolerance in this age group. This randomized controlled trial of head-down bedrest (HDBR) in 55- to 65-yr-old men and women investigated if exercise could avert post-HDBR orthostatic intolerance. Twenty-two healthy older adults (11 female) underwent a strict 14-day HDBR and were assigned to either an exercise (EX) or control (CON) group. The exercise intervention included high-intensity, aerobic, and resistance exercises. Head-up tilt-testing to a maximum of 15 minutes was performed at baseline (Pre-Bedrest) and immediately after HDBR (R1), as well as 6 days (R6) and 4 weeks (R4wk) later. At Pre-Bedrest, three participants did not complete the full 15 minutes of tilt. At R1, 18 did not finish, with no difference in tilt end time between CON (422 ± 287 s) and EX (409 ± 346 s). No differences between CON and EX were observed at R6 or R4wk. At R1, just 1 participant self-terminated the test with symptoms, while 12 others reported symptoms only after physiological test termination criteria were reached. Finishers on R1 protected arterial pressure with higher total peripheral resistance relative to Pre-Bedrest. Cerebral blood velocity decreased linearly with reductions in arterial pressure, end-tidal CO2, and cardiac output. High-intensity interval exercise did not benefit post-HDBR orthostatic tolerance in older adults. Multiple factors were associated with the reduction in cerebral blood velocity leading to intolerance.
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Hipotensión Ortostática , Intolerancia Ortostática , Masculino , Humanos , Femenino , Anciano , Intolerancia Ortostática/diagnóstico , Intolerancia Ortostática/prevención & control , Reposo en Cama/efectos adversos , Inclinación de Cabeza/efectos adversos , Inclinación de Cabeza/fisiología , Pruebas de Mesa Inclinada , Ejercicio Físico , Presión Sanguínea , Hipotensión Ortostática/diagnóstico , Hipotensión Ortostática/prevención & control , Frecuencia CardíacaRESUMEN
Nonintrusive estimation of oxygen uptake (VÌo2) is possible with wearable sensor technology and artificial intelligence. VÌo2 kinetics have been accurately predicted during moderate exercise using easy-to-obtain sensor inputs. However, VÌo2 prediction algorithms for higher-intensity exercise with inherent nonlinearities are still being refined. The purpose of this investigation was to test if a machine learning model can accurately predict dynamic VÌo2 across exercise intensities, including slower VÌO2 kinetics normally observed during heavy- compared with moderate-intensity exercise. Fifteen young healthy adults (seven females; peak VÌo2: 42 ± 5 mL·min-1·kg-1) performed three different pseudorandom binary sequence (PRBS) exercise tests ranging in intensity from low-to-moderate, low-to-heavy, and ventilatory threshold-to-heavy work rates. A temporal convolutional network was trained to predict instantaneous VÌo2, with model inputs including heart rate, percent heart rate reserve, estimated minute ventilation, breathing frequency, and work rate. Frequency domain analyses between VÌo2 and work rate were used to evaluate measured and predicted VÌo2 kinetics. Predicted VÌo2 had low bias (-0.017 L·min-1, 95% limits of agreement: [-0.289, 0.254]), and was very strongly correlated (rrm = 0.974, P < 0.001) with the measured VÌo2. The extracted indicator of kinetics, mean normalized gain (MNG), was not different between predicted and measured VÌo2 responses (main effect: P = 0.374, ηp2 = 0.01), and decreased with increasing exercise intensity (main effect: P < 0.001, ηp2 = 0.64). Predicted and measured VÌo2 kinetics indicators were moderately correlated across repeated measurements (MNG: rrm = 0.680, P < 0.001). Therefore, the temporal convolutional network accurately predicted slower VÌo2 kinetics with increasing exercise intensity, enabling nonintrusive monitoring of cardiorespiratory dynamics across moderate- and heavy-exercise intensities.NEW & NOTEWORTHY Machine learning analysis of wearable sensor data with a sequential model, which utilized a receptive field of approximately 3 min to make instantaneous oxygen uptake estimations, accurately predicted oxygen uptake kinetics from moderate through to higher-intensity exercise. This innovation will enable nonintrusive cardiorespiratory monitoring over a wide range of exercise intensities encountered in vigorous training and competitive sports.
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Inteligencia Artificial , Consumo de Oxígeno , Adulto , Femenino , Humanos , Consumo de Oxígeno/fisiología , Ejercicio Físico/fisiología , Aprendizaje Automático , Cinética , Prueba de Esfuerzo , OxígenoRESUMEN
Cardiorespiratory fitness declines with age and this decline can be accelerated by inactivity and bed rest. Recovery of fitness is possible, but the timeline in 55- to 65-yr-old adults is unknown. Furthermore, the effectiveness of exercise to prevent deconditioning during bed rest is unexplored in this age group. Twenty-two adults (11 women, 59 ± 3 yr) completed 2 wk of strict 6° head-down bed rest (HDBR). Half of the participants performed approximately 1 h of daily exercises, including high-intensity interval cycling, aerobic cycling, and upper- and lower-body resistance training, whereas control participants were inactive. Step-incremental cycling tests to exhaustion were conducted pre-HDBR and at three times during the recovery phase (day 1 or 2, day 6, and 4 wk) to assess peak oxygen uptake (VÌo2). Peak VÌo2 was reduced in the control group throughout the first 6 days of recovery, but did return to pre-HDBR levels by the 4-wk recovery time point (interaction: P = 0.002). In the exercise group, peak VÌo2 was not different at any time point during recovery from pre-HDBR. Ventilatory threshold VÌo2 (interaction: P = 0.002) and heart rate at 15 W (interaction: P = 0.055) mirrored the changes in peak VÌo2 in each respective group. Overall, this study showed that approximately 1 h of daily exercise effectively protected 55- to 65-yr-old adults' cardiorespiratory fitness during 2 wk of HDBR. HDBR without exercise countermeasures caused substantial reductions in cardiorespiratory fitness, but fitness recovered within 4 wk of resuming daily activities. These findings highlight the importance of physical activity in late middle-age adults.NEW & NOTEWORTHY We report the complete time-course of cardiorespiratory fitness recovery back to baseline levels following 2 wk of head-down bed rest in 55- to 65-yr-old adults and found that multimodal training, consisting of high-intensity interval, aerobic and resistive exercises, performed throughout the 2 wk of head-down bed rest prevented reductions in cardiorespiratory fitness.
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Reposo en Cama , Capacidad Cardiovascular , Persona de Mediana Edad , Humanos , Adulto , Femenino , Ejercicio Físico/fisiología , Terapia por Ejercicio , Prueba de EsfuerzoRESUMEN
Background: Insufficient cardiac output in individuals with heart failure (HF) limits daily functioning and reduces quality of life. Although lower cerebral perfusion, secondary to limitations in cardiac output, has been observed during moderate-intensity efforts, individuals with HF also may be at risk for lower perfusion during even low-intensity ambulatory activities. Methods: We determined whether HF is associated with an altered cerebrovascular response to low-intensity activities representative of typical challenges of daily living. In this study, we monitored central hemodynamics and middle cerebral artery blood velocity (MCAv) and cerebral tissue oxygenation (near-infrared spectroscopy) in 10 individuals with HF (aged 78 ± 4 years; left ventricular ejection fraction 20%-61%) and 13 similar-aged controls (79 ± 8 years; 52%-73%) during 3 randomized transitions, as follows: (i) supine-to-standing; (ii) sitting-to-slow-paced over-ground walking; and (iii) sitting-to-normal-paced over-ground walking. Results: Throughout supine, sitting, standing, and both walking conditions, individuals with HF had lower cardiac index and cerebral tissue oxygenation than controls (P < 0.05), and MCAv was lower across the range of blood pressure in HF patients (P = 0.051) and during walking only (P = 0.011). Individuals with HF had an attenuated increase in stroke volume index and cardiac index during normal-paced walking, compared to controls (P < 0.01). Conclusions: The indices of cerebral perfusion from MCAv and cerebral oxygenation were lower during ambulatory activities in individuals with HF; however, relationships between MCAv and blood pressure were not different between those with HF and controls, indicating no difference in static cerebral autoregulation.
Contexte: Un débit cardiaque insuffisant chez les personnes atteintes d'insuffisance cardiaque limite les activités quotidiennes et affecte la qualité de vie. Par exemple, des efforts d'intensité modérée ont été associés à une perfusion cérébrale affaiblie chez ces personnes. Or, il semble que même des activités ambulatoires de faible intensité soient susceptibles d'avoir les mêmes conséquences. Méthodologie: Nous voulions déterminer si l'insuffisance cardiaque est associée à une altération de la réponse cérébrovasculaire à des activités de faible intensité qui sont typiques de la vie quotidienne. Dans le cadre de cette étude, nous avons surveillé l'hémodynamique centrale et la vitesse du sang dans l'artère cérébrale moyenne (VACM), ainsi que l'oxygénation tissulaire cérébrale (par spectroscopie dans le proche infrarouge) chez 10 personnes atteintes d'insuffisance cardiaque (âge : 78 ± 4 ans; fraction d'éjection du ventricule gauche de 20 à 61 %) et 13 témoins d'âge similaire (79 ± 8 ans; de 52 à 73 %) lors de 3 transitions réparties de façon aléatoire, soit : i) de la position couchée à debout; ii) de la position assise à une marche lente et iii) de la position assise à une marche à vitesse normale. Résultats: En position couchée, assise ou debout et avec les deux vitesses de marche, l'index cardiaque et l'oxygénation tissulaire cérébrale étaient plus faibles chez les personnes atteintes d'insuffisance cardiaque que chez les témoins (p < 0,05); la VACM était plus faible dans toutes les plages de pression artérielle chez les personnes atteintes d'insuffisance cardiaque (p = 0,051) et durant la marche seulement (p = 0,011). Les personnes atteintes d'insuffisance cardiaque présentaient une plus faible augmentation du volume d'éjection systolique et de l'index cardiaque durant la marche à vitesse normale, comparativement aux témoins (p < 0,01). Conclusions: Les indices de la perfusion cérébrale selon la VACM et l'oxygénation cérébrale étaient réduits durant les activités ambulatoires chez les personnes atteintes d'insuffisance cardiaque; cependant, les relations entre la VACM et la pression artérielle n'étaient pas différentes entre les personnes atteintes d'insuffisance cardiaque et les témoins, ce qui indique que l'autorégulation cérébrale statique n'est pas un facteur de différenciation.
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OBJECTIVE: To develop and evaluate an accurate method for cuffless blood pressure (BP) estimation during moderate- and heavy-intensity exercise. METHODS: Twelve participants performed three cycling exercises: a ramp-incremental exercise to exhaustion, and moderate and heavy pseudorandom binary sequence exercises on an electronically braked cycle ergometer over the course of 21 minutes. Subject-specific and population-based nonlinear autoregressive models with exogenous inputs (NARX) were compared with feedforward artificial neural network (ANN) models and pulse arrival time (PAT) models. RESULTS: Population-based NARX models, (applying leave-one-subject-out cross-validation), performed better than the other models and showed good capability for estimating large changes in mean arterial pressure (MAP). The models were unable to track consistent decreases in BP during prolonged exercise caused by reduction in peripheral vascular resistance, since this information is apparently not encoded in the employed proxy physiological signals (electrocardiography and forehead PPG) used for BP estimation. Nevertheless, the population-based NARX model had an error standard deviation of 11.0 mmHg during the entire exercise window, which improved to 9.0 mmHg when the model was periodically calibrated every 7 minutes. CONCLUSION: Population-based NARX models can estimate BP during moderate- and heavy-intensity exercise but need periodic calibration to account for the change in vascular resistance during exertion. SIGNIFICANCE: MAP can be continuously tracked during exercise using only wearable sensors, making monitoring exercise physiology more convenient and accessible.
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Determinación de la Presión Sanguínea , Dispositivos Electrónicos Vestibles , Humanos , Presión Sanguínea/fisiología , Determinación de la Presión Sanguínea/métodos , Fotopletismografía/métodos , Electrocardiografía/métodos , Análisis de la Onda del Pulso/métodosRESUMEN
Significant progress has been made in the development of countermeasures to attenuate the negative consequences of prolonged exposure to microgravity on astronauts' bodies. Deconditioning of several organ systems during flight includes losses to cardiorespiratory fitness, muscle mass, bone density and strength. Similar deconditioning also occurs during prolonged bedrest; any protracted time immobile or inactive, especially for unwell older adults (e.g., confined to hospital beds), can lead to similar detrimental health consequences. Due to limitations in physiological research in space, the six-degree head-down tilt bedrest protocol was developed as ground-based analogue to spaceflight. A variety of exercise countermeasures have been tested as interventions to limit detrimental changes and physiological deconditioning of the musculoskeletal and cardiovascular systems. The Canadian Institutes of Health Research and the Canadian Space Agency recently provided funding for research focused on Understanding the Health Impact of Inactivity to study the efficacy of exercise countermeasures in a 14-day randomized clinical trial of six-degree head-down tilt bedrest study in older adults aged 55-65 years old (BROA). Here we will describe the development of a multi-modality countermeasure protocol for the BROA campaign that includes upper- and lower-body resistance exercise and head-down tilt cycle ergometry (high-intensity interval and continuous aerobic exercise training). We provide reasoning for the choice of these modalities following review of the latest available information on exercise as a countermeasure for inactivity and spaceflight-related deconditioning. In summary, this paper sets out to review up-to-date exercise countermeasure research from spaceflight and head-down bedrest studies, whilst providing support for the proposed research countermeasure protocols developed for the bedrest study in older adults.
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Physical activity was reduced during the COVID-19 pandemic, especially when lockdowns were mandated; however, little is known about the impact of these lifestyle changes on objective measures of cardiorespiratory fitness. To address this knowledge gap, we evaluated the cardiorespiratory fitness of 14 young healthy adults (4 women, age: 27 ± 6 yr) just before the pandemic and after â¼1 yr of public health measures being in place. During fitness assessments, participants performed submaximal pseudorandom cycling exercise to assess cardiorespiratory kinetics, and a 25 W·min-1 ramp-incremental cycling test to determine peak oxygen uptake (VÌo2). Cluster analysis identified two subgroups of participants: those who had reduced peak VÌo2 at the 1-yr follow-up (-0.50 ± 0.17 L·min-1) and those whose peak VÌo2 was maintained (0.00 ± 0.10 L·min-1). Participants with reduced peak VÌo2 also exhibited slower heart rate kinetics (interaction: P = 0.01), reduced peak O2 pulse (interaction: P < 0.001), and lower peak work rate (interaction: P < 0.001) after 1 yr of the pandemic, whereas these variables were unchanged in the group of participants who maintained peak VÌo2. Regardless of changes in peak VÌo2, both subgroups of participants gained body mass (main effect: P = 0.002), which was negatively correlated with participants' level of self-reported physical activity level at the follow-up assessment (mass: ρ = -0.59, P = 0.03) These findings suggest that some young healthy individuals lost cardiorespiratory fitness during the pandemic, whereas others gained weight, but both changes could potentially increase the risk of adverse health outcomes and disease later in life if left unaddressed.NEW & NOTEWORTHY Some young healthy adults experienced cardiovascular deconditioning during the COVID-19 pandemic, with measurable reductions in cardiorespiratory fitness, whereas others experienced no change in fitness but gained body mass, which was related to self-reported physical activity during the pandemic.
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COVID-19 , Capacidad Cardiovascular , Adulto , Control de Enfermedades Transmisibles , Prueba de Esfuerzo , Femenino , Humanos , Consumo de Oxígeno/fisiología , Pandemias , Aptitud Física/fisiología , Adulto JovenRESUMEN
PURPOSE: To determine how repeatable thoracoabdominal compartmental contributions to tidal volume (VT) are across different intensities of exercise, and to examine if the pattern of breathing for a given minute ventilation (VÌE) is reproducible between constant-load and ramp exercise tests. METHODS: Ten healthy adults (age: 27 ± 6 yr, peak oxygen uptake: 42 ± 5 mL min-1 kg-1) completed a 25 W·min-1 ramp cycling test to exhaustion and two repetitions of a step cycling test on separate days. VT, breathing rate (BR), and VÌE were assessed using a bi-directional turbine, and thoracic and abdominal contributions to VT were measured using respiratory inductance plethysmography. Repeatability (step vs. step) and reproducibility (step vs. ramp) of responses were assessed using the intra-class correlation coefficient (ICC). RESULTS: The relative compartment contributions to VT during step exercise were highly repeatable for low (ICC = 0.87, p = 0.003), moderate (ICC = 0.89, p = 0.002) and heavy (ICC = 0.93, p = 0.001) exercise. Inter-individual differences in response to higher intensity exercise were observed, as two participants had significant relationships between VT and their percent compartmental contributions to VT, but five others did not. No differences were identified between ramp and step exercise tests for VT (main effect: p = 0.61) or BR (main effect: p = 0.77) at matched VÌE for each intensity, and the pattern of breathing was reproducible for each intensity. CONCLUSION: These findings suggest the way young healthy adults breathe for a given VÌE is repeatable day-to-day and reproducible between different exercise protocols.
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Ejercicio Físico , Respiración , Adulto , Ejercicio Físico/fisiología , Prueba de Esfuerzo , Humanos , Reproducibilidad de los Resultados , Volumen de Ventilación Pulmonar/fisiología , Adulto JovenRESUMEN
Oxygen consumption ([Formula: see text]) provides established clinical and physiological indicators of cardiorespiratory function and exercise capacity. However, [Formula: see text] monitoring is largely limited to specialized laboratory settings, making its widespread monitoring elusive. Here we investigate temporal prediction of [Formula: see text] from wearable sensors during cycle ergometer exercise using a temporal convolutional network (TCN). Cardiorespiratory signals were acquired from a smart shirt with integrated textile sensors alongside ground-truth [Formula: see text] from a metabolic system on 22 young healthy adults. Participants performed one ramp-incremental and three pseudorandom binary sequence exercise protocols to assess a range of [Formula: see text] dynamics. A TCN model was developed using causal convolutions across an effective history length to model the time-dependent nature of [Formula: see text]. Optimal history length was determined through minimum validation loss across hyperparameter values. The best performing model encoded 218 s history length (TCN-VO2 A), with 187, 97, and 76 s yielding <3% deviation from the optimal validation loss. TCN-VO2 A showed strong prediction accuracy (mean, 95% CI) across all exercise intensities (-22 ml min-1, [-262, 218]), spanning transitions from low-moderate (-23 ml min-1, [-250, 204]), low-high (14 ml min-1, [-252, 280]), ventilatory threshold-high (-49 ml min-1, [-274, 176]), and maximal (-32 ml min-1, [-261, 197]) exercise. Second-by-second classification of physical activity across 16,090 s of predicted [Formula: see text] was able to discern between vigorous, moderate, and light activity with high accuracy (94.1%). This system enables quantitative aerobic activity monitoring in non-laboratory settings, when combined with tidal volume and heart rate reserve calibration, across a range of exercise intensities using wearable sensors for monitoring exercise prescription adherence and personal fitness.
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BACKGROUND: Chemotherapy-induced peripheral neuropathy, a side effect of cancer treatment, presents several issues to patients, including reduced sensation and increased fall risk. Previously, massage therapy has been shown to improve chemotherapy-induced peripheral neuropathy symptoms, possibly through increased blood flow. A custom built intermittent pneumatic compression device, previously shown to increase lower leg blood flow, was tested as a plausible treatment modality. METHODS: Seven cancer survivors suffering from chemotherapy-induced peripheral neuropathy were recruited. Foot sensation (Semmes-Weinstein test) as well as static (dual and tandem stance) and dynamic (timed-up-and-go) balance control tests were performed both pre and post a 5-min intermittent pneumatic compression intervention. Self-reported feedback was provided by participants following testing and 24-h later. FINDINGS: Five participants reported positive changes in their feet immediately following intermittent pneumatic compression treatment while four of those participants reported positive changes up to 24 h after intervention. Foot sensation was unchanged regardless of location tested (P ≥ 0.23). Postural sway path length and sway area were unchanged following intervention during dual stance (P ≥ 0.14), but path length was significantly reduced (~19.9%) following intervention during tandem stance (P = 0.033). Timed-up-and-go duration was also significantly reduced (~7.0%, P = 0.012). INTERPRETATION: Overall, these findings demonstrate that intermittent pneumatic compression may be a plausible treatment modality for improving self-reported foot sensation as well as static and dynamic balance control. As a pilot study, this study provides sufficient context for further research exploring the efficacy of intermittent pneumatic compression as a treatment using a randomized control trial design.
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Antineoplásicos , Enfermedades del Sistema Nervioso Periférico , Humanos , Aparatos de Compresión Neumática Intermitente , Enfermedades del Sistema Nervioso Periférico/inducido químicamente , Enfermedades del Sistema Nervioso Periférico/terapia , Proyectos Piloto , SensaciónRESUMEN
The objective is to develop a cuffless method that accurately estimates blood pressure (BP) during activities of daily living. User-specific nonlinear autoregressive models with exogenous inputs (NARX) are implemented using artificial neural networks to estimate the BP waveforms from electrocardiography and photoplethysmography signals. To broaden the range of BP in the training data, subjects followed a short procedure consisting of sitting, standing, walking, Valsalva maneuvers, and static handgrip exercises. The procedure was performed before and after a six-hour testing phase wherein five participants went about their normal daily living activities. Data were further collected at a four-month time point for two participants and again at six months for one of the two. The performance of three different NARX models was compared with three pulse arrival time (PAT) models. The NARX models demonstrate superior accuracy and correlation with "ground truth" systolic and diastolic BP measures compared to the PAT models and a clear advantage in estimating the large range of BP. Preliminary results show that the NARX models can accurately estimate BP even months apart from the training. Preliminary testing suggests that it is robust against variabilities due to sensor placement. This establishes a method for cuffless BP estimation during activities of daily living that can be used for continuous monitoring and acute hypotension and hypertension detection.
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Actividades Cotidianas , Dispositivos Electrónicos Vestibles , Presión Sanguínea , Determinación de la Presión Sanguínea , Fuerza de la Mano , Humanos , Fotopletismografía , Análisis de la Onda del PulsoRESUMEN
Hot environmental conditions can challenge thermoregulation resulting in exacerbated heat strain. This study evaluated the influence of continuous inner forearm cooling on gastrointestinal temperature (TGI) and physiological responses to exercise in hot (30°C) and humid (relative humidity: 70%) conditions. Eleven trained cyclists (seven male age: 37±12 years; four female age: 41±15 years; mean±standard deviation) performed two experimental trials, cycling at 66% of their self-reported functional threshold power (average work rate over an hour of maximum effort cycling; 175±34W) for 45 minutes in an environmental chamber. One trial employed continuous inner forearm cooling (COOL) with 5°C water passing through aluminum heat exchangers, while the other had no cooling (CONTROL). Heat was removed from the body at an average rate of 30.3±6.6W during the COOL trial resulting in an attenuation of TGI rise (CONTROL: 2.46±0.70, COOL: 2.03±0.63°C·h-1; p=0.002). The change in heart rate from the 10th minute to the end of exercise, as an indicator of cardiovascular drift, was reduced (CONTROL: 20±7, COOL: 17±6beats·min-1; p=0.050) and end-exercise thermal comfort was improved in the COOL trial with a trend for reduced rating of perceived exertion (p=0.055). Findings suggest that continuous cooling of the inner forearms can attenuate the rise of TGI and help mitigate the risk of heat injury during exercise in hot and humid conditions.
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Ciclismo/fisiología , Temperatura Corporal/fisiología , Crioterapia/métodos , Tracto Gastrointestinal/fisiología , Adulto , Estudios Cruzados , Crioterapia/instrumentación , Femenino , Antebrazo , Voluntarios Sanos , Frecuencia Cardíaca/fisiología , Humanos , Masculino , Persona de Mediana Edad , Prueba de Estudio ConceptualRESUMEN
At the onset of an exercise transition, exponential modeling to calculate a time constant (τ) is the conventional method to analyze pulmonary oxygen uptake (VÌO2p) kinetics for moderate and heavy exercises. A new frequency domain analysis technique, mean normalized gain (MNG), has been used to analyze VÌO2p kinetics during moderate exercise, but has not been evaluated for its ability to detect differences in kinetics between moderate and heavy exercises. This study tested the hypothesis that MNG would detect smaller amplitude VÌO2p responses in the heavy-exercise domain compared with moderate-exercise domain. Eight young healthy adults (3 female; age: 27 ± 6 yr; peak VÌO2p: 43 ± 6 mL·min-1·kg-1; means ± SD) performed three bouts of pseudorandom binary sequence (PRBS) exercise for frequency analysis, with the work rate (WR) changing between 25 W and 90% ventilatory threshold (VT; L â MPRBS), 25 W and 50% of the difference between VT and peak VÌO2p (Δ50%; L â HPRBS), and VT to Δ50% (VT â HPRBS). Step exercise tests with equivalent changes in WR to the PRBS tests were performed to facilitate the comparison between MNG and τ. MNG was the highest for L â MPRBS (59 ± 7%), then L â HPRBS (52 ± 6%), and the lowest for VT â HPRBS (38 ± 7%, F(2,14) = 129.755, P < 0.001) exercise conditions indicating slower kinetics with increasing exercise intensity that correlated strongly in repeated measures with τ from step transitions (rrm = -0.893). These results indicate that frequency domain analysis and MNG reliably detect differences in VÌO2p kinetics observed across exercise intensity domains.NEW & NOTEWORTHY Mean normalized gain is able to detect differences in VÌO2p kinetics between moderate-, heavy-, and heavy-intensity exercises from a raised WR within the same individuals. This new method of kinetic analysis may be advantageous compared with conventional VÌO2p curve fitting, as it is less sensitive to breath-by-breath noise, it can provide useful information from a single exercise testing session, and it can be applied to nonconstant work rate exercise situations.
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Músculo Esquelético , Consumo de Oxígeno , Adulto , Ejercicio Físico , Prueba de Esfuerzo , Femenino , Humanos , Cinética , Músculo Esquelético/metabolismo , Oxígeno/metabolismo , Intercambio Gaseoso Pulmonar , Adulto JovenRESUMEN
This work presents a modelling approach to predict the blood pressure (BP) waveform time series during activities of daily living without the use of a traditional pressure cuff. A nonlinear autoregressive model with exogenous inputs (NARX) is implemented using artificial neural networks and trained to predict the BP waveform time series from electrocardiography (ECG) and forehead photoplethysmography (PPG) input signals. To broaden the range of blood pressures present in the training set, a protocol was implemented that included sitting, standing, walking, Valsalva manoeuvers, and static handgrip exercise. A five-minute interval of data in the sitting position at the end of the day was also used for training. The efficacy of the cuffless BP method for continuous BP estimation over 4.67 hours was evaluated on 3 participants for varying training data segments. A mean absolute error of 6.3 and 5.2 mmHg were achieved for systolic BP and diastolic BP estimates, respectively. Including static handgrips and Valsalva manoeuvers in the training dataset leads to better estimation of the higher ranges of BP observed throughout the day. The proposed method shows potential for estimating the range of BP experienced during activities of daily living.Clinical Relevance- Establishes a method for cuffless continuous blood pressure estimation during activities of daily living that can be used for continuous monitoring and acute hypertension detection.
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Actividades Cotidianas , Fuerza de la Mano , Presión Sanguínea , Determinación de la Presión Sanguínea , Humanos , Análisis de la Onda del PulsoRESUMEN
Postural instability is prevalent in aging and neurodegenerative disease, decreasing quality of life and independence. Quantitatively monitoring balance control is important for assessing treatment efficacy and rehabilitation progress. However, existing technologies for assessing postural sway are complex and expensive, limiting their widespread utility. Here, we propose a monocular imaging system capable of assessing sub-millimeter 3D sway dynamics during quiet standing. Two anatomical targets with known feature geometries were placed on the lumbar and shoulder. Upper and lower trunk 3D kinematic motion were automatically assessed from a set of 2D frames through geometric feature tracking and an inverse motion model. Sway was tracked in 3D and compared between control and hypoperfusion conditions in 14 healthy young adults. The proposed system demonstrated high agreement with a commercial motion capture system (error [Formula: see text], [-0.52, 0.52]). Between-condition differences in sway dynamics were observed in anterior-posterior sway during early and mid stance, and medial-lateral sway during mid stance commensurate with decreased cerebral perfusion, followed by recovered sway dynamics during late stance with cerebral perfusion recovery. This inexpensive single-camera system enables quantitative 3D sway monitoring for assessing neuromuscular balance control in weakly constrained environments.