1,721,024 research outputs found
Fractal analysis of heart rate variability reveals alterations of the integrative autonomic control of circulation in paraplegic individuals
Full text linkThe autonomic nervous system plays a major role in the integrative control of circulation, possibly contributing to the 'complex' dynamics responsible for fractal components in heart rate variability. Aim of this study is to evaluate whether an altered autonomic integrative control is identified by fractal analysis of heart rate variability. We enrolled 14 spinal cord injured individuals with complete lesion between the 5th and 11th thoracic vertebra (SCIH), 14 with complete lesion between 12th thoracic and 5th lumbar vertebra (SCIL), and 34 able-bodied controls (AB). These paraplegic subjects have an altered autonomic integrative regulation, but intact autonomic cardiac control and, as to SCILindividuals, intact autonomic splanchnic control. Power spectral and fractal analysis (temporal spectrum of scale coefficients) were performed on 10 min tachograms. AB and SCILpower spectra were similar, while the SCILfractal spectrum had higher coefficients between 12 and 48 s. SCIHindividuals had lower power than controls at 0.1 Hz; their fractal spectrum was morphologically different, diverging from that of controls at the largest scales (120 s). Therefore, when the lesion compromises the autonomic control of lower districts, fractal analysis reveals alterations undetected by power spectral analysis of heart rate variability
Sample, Fuzzy and Distribution Entropies of Heart Rate Variability: What Do They Tell Us on Cardiovascular Complexity?
Full text linkDistribution Entropy (DistEn) has been introduced as an alternative to Sample Entropy (SampEn) to assess the heart rate variability (HRV) on much shorter series without the arbitrary definition of distance thresholds. However, DistEn, considered a measure of cardiovascular complexity, differs substantially from SampEn or Fuzzy Entropy (FuzzyEn), both measures of HRV randomness. This work aims to compare DistEn, SampEn, and FuzzyEn analyzing postural changes (expected to modify the HRV randomness through a sympatho/vagal shift without affecting the cardiovascular complexity) and low-level spinal cord injuries (SCI, whose impaired integrative regulation may alter the system complexity without affecting the HRV spectrum). We recorded RR intervals in able-bodied (AB) and SCI participants in supine and sitting postures, evaluating DistEn, SampEn, and FuzzyEn over 512 beats. The significance of “case” (AB vs. SCI) and “posture” (supine vs. sitting) was assessed by longitudinal analysis. Multiscale DistEn (mDE), SampEn (mSE), and FuzzyEn (mFE) compared postures and cases at each scale between 2 and 20 beats. Unlike SampEn and FuzzyEn, DistEn is affected by the spinal lesion but not by the postural sympatho/vagal shift. The multiscale approach shows differences between AB and SCI sitting participants at the largest mFE scales and between postures in AB participants at the shortest mSE scales. Thus, our results support the hypothesis that DistEn measures cardiovascular complexity while SampEn/FuzzyEn measure HRV randomness, highlighting that together these methods integrate the information each of them provides
On the Autonomic Control of Heart Rate Variability: How the Mean Heart Rate Affects Spectral and Complexity Analysis and a Way to Mitigate Its Influence
Full text linkHeart Rate Variability (HRV) analysis allows for assessing autonomic control from the beat-by-beat dynamics of the time series of cardiac intervals. However, some HRV indices may strongly correlate with the mean heart rate, possibly flawed by the interpretation of HRV changes in terms of autonomic control. Therefore, this study aims to (1) investigate how HRV indices of fluctuation amplitude and multiscale complex dynamics of cardiac time series faithfully describe the autonomic control at different heart rates through a mathematical model of the generation of cardiac action potentials driven by realistically synthesized autonomic modulations; and (2) propose an alternative procedure of HRV analysis less sensitive to the mean heart rate. Results on the synthesized series confirm a strong dependency of amplitude indices of HRV on the mean heart rate due to a nonlinearity in the model, which can be removed by our procedure. Application of our procedure to real cardiac intervals recorded in different postures suggests that the dependency of these indices on the heart rate may importantly affect the physiological interpretation of HRV. By contrast, multiscale complexity indices do not substantially depend on the heart rate provided that multiscale analyses are defined on a time- rather than a beat-basis
Complexity Analysis of Surface Electromyography for Assessing the Myoelectric Manifestation of Muscle Fatigue: A Review
Full text linkThe surface electromyography (sEMG) records the electrical activity of muscle fibers during contraction: one of its uses is to assess changes taking place within muscles in the course of a fatiguing contraction to provide insights into our understanding of muscle fatigue in training protocols and rehabilitation medicine. Until recently, these myoelectric manifestations of muscle fatigue (MMF) have been assessed essentially by linear sEMG analyses. However, sEMG shows a complex behavior, due to many concurrent factors. Therefore, in the last years, complexity-based methods have been tentatively applied to the sEMG signal to better individuate the MMF onset during sustained contractions. In this review, after describing concisely the traditional linear methods employed to assess MMF we present the complexity methods used for sEMG analysis based on an extensive literature search. We show that some of these indices, like those derived from recurrence plots, from entropy or fractal analysis, can detect MMF efficiently. However, we also show that more work remains to be done to compare the complexity indices in terms of reliability and sensibility; to optimize the choice of embedding dimension, time delay and threshold distance in reconstructing the phase space; and to elucidate the relationship between complexity estimators and the physiologic phenomena underlying the onset of MMF in exercising muscles
Perceptual-vision training as a strategy for healthy aging in adults with intellectual disability: a study protocol
Full text linkAging leads to changes in motor-cognitive performance. Despite the importance of physical activity for healthy aging and the need for health promotion interventions in individuals with intellectual disability (ID), there is a lack of empirically strategies for promoting health in adults with ID. Therefore, we are conducting a clinical trial (NCT06628999 on clinicaltrials.gov) to investigate a strategy for promoting healthy aging by targeting physical and cognitive domains in ID individuals. The present work aims to provide a detailed account of the study protocol of the proposed trial to promote transparency and dissemination of the ongoing research. Specifically, this project will study the effect of a vision training program on cognitive performance and physical fitness in adults with ID. A secondary aim is to examine the association between mental and physical performance outcomes. Participants will be randomly allocated into a vision training group (VT, n = 28), a vision training-detraining group (VTD, n = 28), and a control group (C, n = 28). During the first 8 weeks, the VT and VTD groups will follow the same training protocol (based on vision oculomotor exercises combined with postural control exercises). From weeks 9 to 16, the VT group will continue the training protocol, whereas the VTD group will abstain from training (detraining). Cognitive performance and physical fitness will be assessed at baseline, mid- and post-training intervention. Overall, a vision training program can positively impact various aspects of life for individuals with ID promoting autonomy, and social integration to counteract the aging process
Essential role of weekly high-frequency plyometric training to enhance physical performance 2 and manage muscle soreness in male adolescent soccer players
Full text linkPurpose: this study aims to investigate the effects of volume-matched plyometric training (PT) with different frequency distributions on physical performance and muscle soreness in adolescent soccer players. Methods: Thirty-four sub-elite players were allocated into two groups: PLYO-1 (n = 17, age 1=16.02±0.26 years) underwent one PT session per week, while PLYO-3 (n = 17, age = 15.81±0.37 years) underwent three volume-matched PT sessions per week. The PT program lasted 9 -weeks with an initial weekly volume of ~55 -foot contacts, increasing by 10% per week. The 7-point Likert scale was employed to assess the perceived muscle soreness before and after each PT session. All players were tested for countermovement horizontal (CMHJ) and vertical (CMVJ) jumps, 10-m sprint and change of direction (COD) performance using the modified 505 test (505mod). Results: After the 9- week experimental period, both groups exhibited significant improvements in CMHJ distance (p 0.911, d = −0.12). The changes in perceived muscle soreness were significantly lower for PLYO-3 compared with PLYO-1 (p < 0.001, d = 1.04) throughout the experimental period. Conclusions: Employing weekly volume-matched PT conducted at different frequencies can help to maintain, or even enhance, jump and COD performance, while differently impacting muscle soreness
Impaired autonomic vascular control : a non linear dynamic analysis
No full textThe specific role of autonomic vascular control in determining non-linear behaviour of RR intervals is not clear. In 10 T12-L4 paraplegic subjects (light vascular autonomic impairment), 12 T 5-T11 paraplegic subjects (moderate vascular autonomic impairment), and 24 controls RR time series were recorded (10 min): 1) in resting supine position; 2) sitting on the wheelchair and 3) during a light (5W) arm exercise. Fractal Dimension (FD), Approximate Entropy (ApEn) and the a scaling exponent (α-DFA, Detrended Fluctuation Analysis) were calculated. The lesional level significantly affected ApEn (p=0.004), FD (p=0.007) and α-DFA (p=0.002). Autonomic activation did not influence FD and α-DFA, but significantly affected ApEn (p=0.03S). It seems that FD and α-DFA are influenced by the changes in nonlinear RR dynamics due to vascular autonomic impairment but not to autonomic activation, whereas ApEn may be equally responsive to either condition
Effects of short term cast wearing on respiratory and cardiac responses to submaximal and maximal exercise in adolescents with idiopathic scoliosis
No full textAIM: Bracing is widely used to treat adolescent scoliosis. However, bracing may also affect respiratory and cardiovascular function. In this thirteen-weeks longitudinal study we evaluated the effect of brace wearing on maximal and submaximal cardiorespiratory capacity in adolescents with moderate idiopathic scoliosis. METHODS: Eight boys and 8 girls (12-18 years) with scoliosis of the thoracic spine (Cobb angle range 32 degrees - 42 degrees in boys and 32 degrees - 60 degrees in girls) were enrolled. Respiratory basal function (forced vital capacity, FVC, and forced expired volume in 1 s, FEV(1)) and cardiorespiratory adjustments to submaximal and maximal cycle ergometer exercise (heart rate, HR, pulmonary ventilation, VE, and oxygen consumption, VO(2)) were measured a week before fitting a brace, after 1 and 12 weeks of brace wearing, and a week after brace removal. RESULTS: With respect to pretreatment values: a) after 1 week of brace wearing FVC and FEV(1) were significantly reduced in both genders; b) after 12 weeks of bracing the amount of oxygen consumed per heart beat was reduced during maximal and submaximal exercises in females only; c) ventilatory efficiency was unchanged in both genders in each condition; d) oxygen uptake during maximal exercise was decreased (by about 10-20%) in females only; e) after brace removal all variables tended to regress to pretreatment values. CONCLUSIONS: Although data are preliminary and need to be confirmed on larger samples of patients, the brace appears to limit maximal exercise performance especially in girls, where it affects the cardiopulmonary efficiency. Thus, moderate physical exercise during brace wearing is advised to counteract respiratory, cardiovascular and muscle inefficiency due to ribcage movement limitations
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