Search results for "VARIABILITY"
showing 10 items of 904 documents
Quantifying coordination and coordination variability in backward versus forward running: Implications for control of motion
2015
The aims of this study were to compare coordination and coordination variability in backward and forward running and to investigate the effects of speed on coordination variability in both backward and forward running. Fifteen healthy male participants took part in this study to run forwards and backwards on a treadmill at 80%, 100% and 120% of their preferred running speeds. The coordinate data of passive reflective markers attached to body segments were recorded using motion capture systems. Coordination of shank-foot and thigh-shank couplings in sagittal plane was quantified using the continuous relative phase method. Coordination variability was calculated as the standard deviation of a…
Effects of sex and menstrual cycle phase on cardiac response and alpha- amylase levels in psychosocial stress.
2018
The impact of sex and the menstrual cycle phase on the autonomic response to psychosocial stress remains controversial. This study explored autonomic nervous system activity through salivary alpha-amylase, heart rate, and heart rate variability responses to the Trier Social Stress Test (TSST) in healthy young people. The sample was composed of 25 men, 26 women in the luteal phase, and 25 women in the follicular phase, from 18 to 25 years of age. Participants were exposed to the TSST or a control condition. The results indicate that women in their follicular phase showed a blunted alpha-amylase response to stress compared to men and women in the luteal phase. In addition, men showed higher s…
Assessment of Heart Rate Variability Thresholds from Incremental Treadmill Tests in Five Cross-Country Skiing Techniques
2016
The assessment of heart rate variability (HRV) thresholds (HRVTs) as an alternative of Ventilatory thresholds (VTs) is a relatively new approach with increasing popularity which has not been conducted in cross-country (XC) skiing yet. The main purpose of the present study was to assess HRVTs in the five main XC skiing-related techniques, double poling (DP), diagonal striding (DS), Nordic walking (NW), V1 skating (V1), and V2 skating (V2).Ten competitive skiers completed these incremental treadmill tests until exhaustion with a minimum of one to two recovery days in between each test. Ventilatory gases, HRV and poling frequencies were measured. The first HRV threshold (HRVT1) was assessed us…
Reduced cardiovascular activation following chronic stress in caregivers of people with anorexia nervosa.
2017
Caring for offspring diagnosed with eating disorders (EDs) puts caregivers under high levels of chronic stress, which have negative consequences for their health. Unfortunately, caregivers have received little attention from mental health professionals. Chronic stress experienced by informal caregivers has been associated with the alteration of body homeostasis, and therefore, the functioning of various physiological systems. This could be the basis of health problems in informal caregivers of people with EDs. The main objective of this study was to analyze physiological response, in terms of heart rate (HR) and heart rate variability (HRV), to an acute laboratory stressor in a sample of in…
Hydration Status, Executive Function, and Response to Orthostatism After a 118-km Mountain Race: Are They Interrelated?
2016
Martínez-Navarro, I, Chiva-Bartoll, O, Hernando, B, Collado, E, Porcar, V, and Hernando, C. Hydration status, executive function and response to orthostatism after a 118-km mountain race: are they interrelated? J Strength Cond Res 32(2): 441-449, 2018-The present study aimed to explore whether blood pressure (BP) and heart rate (HR) variability (HRV) responsiveness to orthostatism, jointly with executive function (EF) performance, was diminished after an ultra-endurance mountain race. Besides, we wanted to assess whether hydration status was related to either performance or the abovementioned alterations. Fifty recreational ultra-endurance athletes participating in the Penyagolosa Trails CS…
Increased gait variability during robot-assisted walking is accompanied by increased sensorimotor brain activity in healthy people
2019
Abstract Background Gait disorders are major symptoms of neurological diseases affecting the quality of life. Interventions that restore walking and allow patients to maintain safe and independent mobility are essential. Robot-assisted gait training (RAGT) proved to be a promising treatment for restoring and improving the ability to walk. Due to heterogenuous study designs and fragmentary knowlegde about the neural correlates associated with RAGT and the relation to motor recovery, guidelines for an individually optimized therapy can hardly be derived. To optimize robotic rehabilitation, it is crucial to understand how robotic assistance affect locomotor control and its underlying brain act…
Breathing 100% oxygen during water immersion improves postimmersion cardiovascular responses to orthostatic stress
2016
Abstract Physiological compensation to postural stress is weakened after long‐duration water immersion (WI), thus predisposing individuals to orthostatic intolerance. This study was conducted to compare hemodynamic responses to postural stress following exposure to WI alone (Air WI), hyperbaric oxygen alone in a hyperbaric chamber (O 2 HC), and WI combined with hyperbaric oxygen (O 2 WI), all at a depth of 1.35 ATA, and to determine whether hyperbaric oxygen is protective of orthostatic tolerance. Thirty‐two healthy men underwent up to 15 min of 70° head‐up tilt (HUT) testing before and after a single 6‐h resting exposure to Air WI ( N = 10), O 2 HC ( N = 12), or O 2 WI ( N = 10). Heart …
Investigating cardiac and respiratory determinants of heart rate variability in an information-theoretic framework.
2014
This study was aimed at comparing two alternative information-theoretic approaches for the combined analysis of heart rate variability (HRV) and respiration variability (RV). The approaches decompose the predictive information about HRV in two terms, quantifying respectively the information stored into HRV and that transferred to HRV from RV. Storage and transfer were assessed by the popular self entropy (SE) and transfer entropy (TE) measures, as well as by the alternative conditional SE (cSE) and cross entropy (CE) measures. The comparison was performed at a theoretical level, computing the exact values of the four measures for simulated cardiorespiratory dynamics, and on real data, estim…
Linear and nonlinear heart rate dynamics in elderly inpatients. Relations with comorbidity and depression
2010
Background. Hospitalization processes are known to increase depressive symptoms arising among elderly population. Meanwhile, dysregulation of cardiac autonomic function has been suggested to link depression and cardiovascular mortality. In this context, analysis of heart rate variability (HRV) is emerging as a powerful mortality risk stratifier clinical tool. The purpose of the study was to examine the relationship among HRV, depression, and comorbidity risk among an elderly inpatient population. Material and methods. Twenty-six subjects (aged 78±9 years) were recruited from the Short- Term Stay Unit at the Hospital General de Alicante. Before joining a Physical Activity Program aimed to pr…
Effects of HRV-Guided vs. Predetermined Block Training on Performance, HRV and Serum Hormones
2017
AbstractThe aim of this study was to compare heart rate variability -guided (HRVG) and predetermined (PD) block periodization of high intensity aerobic training (HIT). Endurance performance, neuromuscular performance, heart rate variability (HRV) and serum hormone concentrations were measured before, in the middle and after the 8-week training period in 24 endurance trained males. Both groups improved significantly maximal treadmill velocity (Vmax) (p<0.001) and 3000 m running performance (HRVG; p<0.001 and PD; p=0.001). The relative changes in Vmax and countermovement jump were significantly greater in HRVG (p<0.05). Nocturnal heart rate decreased in both groups (p<0.01), but H…