HRV analysis: undependability of approximate entropy at locating optimum complexity in malnourished children.

INTRODUCTION: Approximate Entropy is an extensively enforced metric to evaluate chaotic responses and irregularities of RR intervals sourced from an eletrocardiogram. However, to estimate their responses, it has one major problem - the accurate determination of tolerances and embedding dimensions. So, we aimed to overt this potential hazard by calculating numerous alternatives to detect their optimality in malnourished children. MATERIALS AND METHODS: We evaluated 70 subjects split equally: malnourished children and controls. To estimate autonomic modulation, the heart rate was measured lacking any physical, sensory or pharmacologic stimuli. In the time series attained, Approximate Entropy was computed for tolerance (0.1→0.5 in intervals of 0.1) and embedding dimension (1→5 in intervals of 1) and the statistical significances between the groups by their Cohen's ds and Hedges's gs were totalled. RESULTS: The uppermost value of statistical significance accomplished for the effect sizes for any of the combinations was -0.2897 (Cohen's ds) and -0.2865 (Hedges's gs). This was achieved with embedding dimension = 5 and tolerance = 0.3. CONCLUSIONS: Approximate Entropy was able to identify a reduction in chaotic response via malnourished children. The best values of embedding dimension and tolerance of the Approximate Entropy to identify malnourished children were, respectively, embedding dimension = 5 and embedding tolerance = 0.3. Nevertheless, Approximate Entropy is still an unreliable mathematical marker to regulate this.

Non-linear regulation of cardiac autonomic modulation in obese youths: interpolation of ultra-short time series.

BACKGROUND: In this study, we applied ultra-short time series of interbeat intervals (RR-intervals) to evaluate heart rate variability through default chaotic global techniques with the purpose of discriminating obese youths from non-obese youth patients. METHOD: Chaotic global analysis of the RR-intervals from the electrocardiogram and pre-processing adjustments was undertaken. The effect of cubic spline interpolations was assessed, while the spectral parameters remained fixed. Exactly, 125 RR-intervals of data were recorded. RESULTS: CFP1, CFP3, and CFP6 were the only significant combinations of chaotic globals when the standard conditions were enforced and at the level p<0.01 (or <1%). These significances were acheived via Kruskal-Wallis and Cohen's ds effects sizes tests of significance after Anderson-Darling and Lilliefors statistical tests indicated non-normal distributions in the majority of cases. Adjustments of the cubic spline interpolation from 1 to 13 Hz were revealed to be inconsequential when measured by Kruskal-Wallis and Cohen's ds, regarding the outcome between the two datasets. CONCLUSION: Chaotic global analysis was offered as a robust technique to distinguish autonomic dysfunction in obese youths. It can discriminate the two different groups using ultra-short data lengths, and no cubic spline interpolations need be applied.

Autonomic responses induced by aerobic submaximal exercise in obese and overweight adolescents.

BACKGROUND: Graded exercises tests are performed in adult populations; nonetheless, the use of this type of assessment is greatly understudied in overweight and obese adolescents. OBJECTIVE: To investigate heart rate autonomic responses to submaximal aerobic exercise in obese and overweight adolescents. METHODS: We recruited 40 adolescents divided into two groups: (1) overweight group comprising 10 boys and 10 girls between Z-score +1 and +2 and (2) obese group comprising 10 boys and 10 girls above Z-score >+2. Heart rate variability was analysed before (T1) and after exercise (T2-T4) on treadmill at a slope of 0%, with 70% of the maximal estimated heart rate (220 - age) for 20 minutes. RESULTS: Heart rate in the overweight group was: 93.2±10.52 bpm versus 120.8±13.49 bpm versus 94.6±11.65 bpm versus 93.0±9.23 bpm, and in the obese group was: 92.0±15.41 bpm versus 117.6±16.31 bpm versus 92.1±12.9 bpm versus 91.8±14.33 bpm. High frequency in the overweight group was: 640±633.1 ms2 versus 84±174.66 ms2 versus 603.5±655.31 ms2 versus 762.6±807.21 ms2, and in the obese group was: 628.4±779.81 ms2 versus 65.4±119.34 ms2 versus 506.2±482.70 ms2 versus 677.9±939.05 ms2; and root mean square of successive differences in the overweight group was: 37.9±18.81 ms versus 10.9±8.41 ms versus 32.8±24.07 ms versus 36.7±21.86 ms, and in the obese group was: 38.7±23.17 ms versus 11.5±8.62 ms versus 32.3±16.74 ms versus 37.3±24.21 ms. These values significantly changed during exercise compared with resting values in overweight and obese groups. Moreover, we also reported no significant difference of resting parasympathetic control of heart rate between obese and overweight adolescents. CONCLUSION: There was no significant difference of autonomic responses elicited by submaximal aerobic exercise between overweight and obese adolescents.

A New Mathematical Approach to Explore the Post-exercise Recovery Process and Its Applicability in a Cold Water Immersion Protocol.

Micheletti, JK, Vanderlei, FM, Machado, AF, de Almeida, AC, Nakamura, FY, Netto Junior, J, and Pastre, CM. A new mathematical approach to explore the post-exercise recovery process and its applicability in a cold water immersion protocol. J Strength Cond Res 33(5): 1266-1275, 2019-The objective of this study was to propose a mathematical model to analyze the post-training recovery of perceptive, functional, metabolic, and autonomic parameters from the use of cold water immersion (CWI) through isolated and combined analysis. Following simulated training, 64 male soccer players were randomized into an experimental group (EG: CWI, 13 ± 1° C; 15 minutes) and a control group (CG: passive recovery; 15 minutes). Perceptive (soreness and perception of recovery), autonomic (heart rate variability [HRV]), metabolic (lactate concentration), and functional parameters (squat jump, T agility test, sprint test, 40-second test, and maximal voluntary isometric contraction) were analyzed before and at specific moments after training (without exceeding 2 hours after training). The variables were analyzed using the raw data, dichotomization of each variable (isolated analysis), and through a mathematical model using the combination of all parameters analyzed (combined analysis). The combined analysis did not demonstrate better efficacy of the EG compared with the CG (69.17 and 63.4%, p = 0.09). In the isolated analysis, a chance of the technique being better was observed in the metabolic parameter at 1 and 2 hours after training (odds ratio, 95% confidence interval = 3.75 [1.01-13.88] and 11.11 [1.25-98.49]), respectively, and in the autonomic parameter at 40-45 minutes after training (4.4 [1.09-17.67]). For the raw data, all parameters analyzed presented recovery by 2 hours after training for both groups. Based on the proposed mathematical model, it is concluded that CWI is not better than the control condition. However, considering the analysis of variables in isolation, the technique presents a better chance of recovery for blood lactate concentration and HRV.

Association of cardiac autonomic modulation with physical and clinical features of young people with type 1 diabetes.

OBJECTIVE: The objective of this study was to verify possible associations between heart rate variability indices and physical activity, body composition, and metabolic and cardiovascular parameters in individuals with type 1 diabetes. METHOD: A total of 39 young patients with type 1 diabetes were included. Body composition, physical activity, cardiovascular parameters, and metabolic parameters were assessed. For the heart rate variability analysis, heart rate was recorded beat-by-beat using a Polar S810i heart rate monitor for 30 minutes, with the volunteers in the supine position; subsequently, the following indices were considered: standard deviation of all normal RR intervals; root-mean square of differences between adjacent normal RR intervals in a time interval; percentage of adjacent RR intervals with a difference of duration >50 ms; high frequency component in milliseconds squared; high frequency component in normalised units; standard deviation of the instantaneous variability beat-to-beat; and standard deviation of the long-term variability. The association between the heart rate variability indices and independent variables was verified through linear regression in unadjusted and adjusted models (considering gender and age). The statistical significance was set at 5% and the confidence interval at 95%. RESULTS: High values of at-rest heart rate were associated with reduced parasympathetic activity and global heart rate variability, and higher values of waist-to-hip ratio were related to lower parasympathetic activity, independent of age or gender. CONCLUSION: For young patients with type 1 diabetes, increases in at-rest heart rate values are associated with reduced parasympathetic activity and global heart rate variability, whereas higher waist-to-hip ratio values are related to lower parasympathetic activity, both independent of age and gender.

Comparison of Two Types of Insoles on Musculoskeletal Symptoms and Plantar Pressure Distribution in a Work Environment: A Randomized Clinical Trial.

BACKGROUND: The aim of the present study was to assess plantar pressure distribution and musculoskeletal symptoms following the use of customized insoles among female assembly line workers. METHODS: The study included 29 female assembly line workers (age, 29.76 ± 5.79 years; weight, 63.79 ± 12.11 kg) with musculoskeletal symptoms who work predominantly while standing. The Nordic Musculoskeletal Questionnaire was administered to the study population. Plantar pressure was determined using a computerized plantar pressure feedback system. A control group (n=13) used ethylvinylacetate insoles (Podaly®) that were individually heat molded and heat glued. The intervention group (n=14) also used the insoles and a strip of the same material was added to the site of greatest plantar pressure as determined by the electronic feedback device. After five weeks, the plantar pressure data were collected again and the questionnaire was administered a second time. RESULTS: There was no significant difference between groups with regard to pain in any anatomic site. However, within each group the lumbar region exhibited a reduction in symptoms in the intervention group (P<0.05), and the feet exhibited a reduction in symptoms in both groups (P<0.05). Mean plantar pressure increased and plantar surface decreased in the intervention group (P<0.05). CONCLUSION: Insoles increased foot comfort in both groups. However, the added strip did not significantly modify either plantar pressure or other symptoms in female workers.

Effects of Effortful Swallow on Cardiac Autonomic Regulation.

Swallowing-induced changes in heart rate have been recently reported. However, it is not apparent the responses of heart rate variability (HRV) elicited by effortful swallow maneuver. We investigated the acute effects of effortful swallowing maneuver on HRV. This study was performed on 34 healthy women between 18 and 35 years old. We assessed heart rate variability in the time (SDNN, RMSSD, and pNN50) and frequency (HF, LF, and LF/HF ratio) domains and, visual analysis through the Poincaré plot. The subjects remained at rest for 5 min during spontaneous swallowing and then performed effortful swallowing for 5 min. HRV was analyzed during spontaneous and effortful swallowing. We found no significant differences for SDNN, pNN50, RMSSD, HF in absolute units (ms(2)). There is a trend for increase of LF in absolute (p = 0.05) and normalized (p = 0.08) units during effortful swallowing. HF in normalized units reduced (p = 0.02) during effortful swallowing and LF/HF ratio (p = 0.03) increased during effortful swallowing. In conclusion effortful swallow maneuver in healthy women increased sympathetic cardiac modulation, indicating a cardiac overload.

Response of cardiac autonomic modulation after a single exposure to musical auditory stimulation.

The acute effects after exposure to different styles of music on cardiac autonomic modulation assessed through heart rate variability (HRV) analysis have not yet been well elucidated. We aimed to investigate the recovery response of cardiac autonomic modulation in women after exposure to musical auditory stimulation of different styles. The study was conducted on 30 healthy women aged between 18 years and 30 years. We did not include subjects having previous experience with musical instruments and those who had an affinity for music styles. The volunteers remained at rest for 10 min and were exposed to classical baroque (64-84 dB) and heavy metal (75-84 dB) music for 10 min, and their HRV was evaluated for 30 min after music cessation. We analyzed the following HRV indices: Standard deviation of normal-to-normal (SDNN) intervals, root mean square of successive differences (RMSSD), percentage of normal-to-normal 50 (pNN50), low frequency (LF), high frequency (HF), and LF/HF ratio. SDNN, LF in absolute units (ms 2 ) and normalized (nu), and LF/HF ratio increased while HF index (nu) decreased after exposure to classical baroque music. Regarding the heavy metal music style, it was observed that there were increases in SDNN, RMSSD, pNN50, and LF (ms 2 ) after the musical stimulation. In conclusion, the recovery response of cardiac autonomic modulation after exposure to auditory stimulation with music featured an increased global activity of both systems for the two musical styles, with a cardiac sympathetic modulation for classical baroque music and a cardiac vagal tone for the heavy metal style.

Relationship between heart rate variability and performance in eccentric training with blood flow restriction.

BACKGROUND: The resistance training with blood flow restriction (BFR) presents results in strength gain and muscle hypertrophy. However, there are no data that evaluate the long-term adaptation of the autonomic nervous system and its influence on the performance, especially with eccentric contractions. OBJECTIVE: To perform a systematic autonomous monitoring during eccentric training with BFR at different loads and to correlate them with possible changes in the performance METHODS: This is a 4-arms, randomized controlled and single blind trial. Sixty men were randomized in four groups: low and high load eccentric exercise (LL and HL); LL and HL with BFR (LL-BFR and HL-BFR). The participants underwent 18 sessions of eccentric exercise for the dominant quadriceps femoris muscle in the isokinetic dynamometer. The performance (strength through isometric, concentric and eccentric peaks torque on the isokinetic dynamometer and Single-leg Hop Test) was evaluated 1 week before, in the fourth week and 1 week after the end of the training programme. Heart rate variability (HRV) through vagal and global indices was evaluated daily for 15 min before each session. RESULTS: There was a significant correlation between performance and HRV for LL and HL-BFR groups, with an increase in parasympathetic indices in the first group and an increase in performance in the second group. CONCLUSION: HRV indices are correlated with performance. However, in the LL group, there was an increase in parasympathetic indices without repercussions on performance while, in the HL-BFR group, there was an increase in performance and no repercussion in the autonomic indices.

Photobiomodulation therapy applied during an exercise-training program does not promote additional effects in trained individuals: A randomized placebo-controlled trial.

BACKGROUND: Previous studies have shown positive results of photobiomodulation (PBM) for improving performance and accelerating post-exercise recovery. However, the effects of PBM in healthy individuals who underwent a neuromuscular adaptation training remain unclear. OBJECTIVE: To investigate the effects of PBM during a training program combining sprints and explosive squats exercises on clinical, functional, and systemic outcomes in trained healthy individuals compared to a placebo intervention and a control. METHODS: We conducted a randomized placebo-controlled trial. Healthy males were randomly assigned to three groups: active PBM (30 J per site), placebo, or control (passive recovery). The participants performed a six-week (12 sessions) of a training program consisting of a combination of sprints and squats with recovery applied between sprints and squats. To prevent the influence of the primary neuromuscular adaptation to exercise on the results, all participants had to participate in a period of six weeks of exercise training program. Functional, clinical, and psychological outcomes and vascular endothelial growth factor (VEGF) were assessed at baseline and after six weeks. Results are expressed as mean difference (MD) and 95% confidence intervals (CI). RESULTS: Thirty-nine healthy male volunteers (aged 18-30 years; body mass index 23.9 ±â€¯3 kg/m²) were recruited. There was no significant time by group interaction, and no significant effect of group, but there was a significant effect of time for maximal voluntary isometric contraction (primary outcome) (MD=22 Nm/kg; 95%CI: 3.9, 40) and for squat jump (MD=1.6 cm; 95CI%: 0.7, 2.5). There was no significant interaction (time*group), time, or group effect for the other outcomes. CONCLUSION: The addition of PBM to a combined training performed for six weeks in previously trained individuals did not result in additional benefits compared to placebo or no additional intervention.

Effects of 12-week Pilates training program on cardiac autonomic modulation: a randomized controlled clinical trial.

Aim: To evaluate the effects of 12-week Pilates training program on cardiac autonomic modulation. Materials & methods: A randomized controlled trial of a 12-week Pilates training program was conducted. A total of 54 men were randomly allocated to either a control or a Pilates group. Initially, the RR intervals were captured for 20 min for later analysis of heart rate variability (HRV). The training protocol was then initiated, in which the Pilates group performed 36 sessions of the Pilates method for approximately 60 min each session, three-times a week, totaling 12 weeks. The control group was instructed to maintain their normal activities during this period. One week after the end of the training, the final evaluations were performed with the capture of RR intervals in both the groups. Linear indices in the time (SDNN and rMSSD) and frequency (low frequency [LF] and high frequency [HF]) domains, and the Poincaré plot (SD1 and SD2) were used. Nonlinear indices were also analyzed (approximate entropy and detrended fluctuation analysis). Descriptive statistics and generalized mixed models were performed. Results: There was a group effect for LF (ms2) and a time effect for SD2. There was a training effect observed by the time*group interactions in which an increase in global HRV indices was found for the Pilates group after 12 weeks (SDNN: mean difference [MD] = 9.82; standard deviation [SD] = 18.52; ES = -0.514; LF [ms2]: MD = 334.23; SD = 669.43; ES = -0.547; SD2: MD = 14.58; SD = 24.28; ES = -0.693). Conclusion: A 12-week Pilates training program promotes significant improvement in global modulation of HRV in the Pilates group considering the significant increase in SDNN, LF (ms2) and SD2 indices. Trial registration number: NCT03232866.

Lower Systolic Blood Pressure in Normotensive Subjects is Related to Better Autonomic Recovery Following Exercise.

Blood pressure (BP) is a cardiovascular parameter applied to detect cardiovascular risk. Recently, the pre-hypertension state has received greater consideration for prevention strategies. We evaluated autonomic and cardiorespiratory recovery following aerobic exercise in normotensive individuals with different systolic BP (SBP) values. We investigated 30 healthy men aged 18 to 30 years divided into groups according to systolic BP (SBP): G1 (n = 16), resting SBP <110 mmHg and G2 (n = 14), resting SBP between 120-110 mmHg. The groups endured 15 minutes seated at rest, followed by a submaximal aerobic exercise on a treadmill and then remaining seated for 60 minutes also at rest, during recovery from the exercise. Cardiorespiratory parameters and heart rate (HR) variability (HRV) (rMSSD, SD1, HF [ms2]) were evaluated before and during recovery from exercise. G2 displayed slower return of SBP, rMSSD and SD1 HRV indices during recovery from exercise compared to G1. In conclusion, normotensive subjects with higher resting SBP (110 to 120 mmHg) offered delayed autonomic recovery following moderate exercise. We suggest that this group may be less physiologically optimized leading to cardiac risks.

Waist-Stature Ratio And Its Relationship With Autonomic Recovery From Aerobic Exercise In Healthy Men.

Autonomic modulation and cardiorespiratory variables are influenced by numerous factors, including anthropometric variables. We investigated autonomic recovery following aerobic exercise in healthy men with different waist-stature ratio (WSR) values. The study was conducted with 52 healthy men aged 18 to 30 years, divided into groups according to the WSR: G1 - between 0.40 and 0.449 (N = 19), G2 - between 0.45 and 0.50 (N = 28) and G3 - between 0.5 and 0.56 (N = 5). The subjects endured 15 minutes seated and at rest followed by an aerobic exercise and then remained seated for 60 minutes and at rest during recovery from exercise. Heart rate (HR) variability (HRV) (rMSSD, SD1, HF [ms2]) and cardiorespiratory variables were analyzed before and after exercise. Recovery of respiratory rate, diastolic blood pressure, SD1 and HF indices were delayed in G2. G3 presented delayed recovery after the maximal effort test while no difference with G2 was noted in the moderate intensity. Correlation and linear regression analysis indicated association of WSR, body mass index and waist circumference with HRV indices in the recovery from aerobic exercise (45 to 60 minutes after exercise) in G2. In conclusion, healthy men with higher WSR accomplished delayed autonomic recovery following maximal effort exercise.

Acute Effects of Different Types of Resistance Training on Cardiac Autonomic Modulation in COPD.

BACKGROUND: An exercise modality that has been gaining significant importance in the rehabilitation of subjects with COPD is resistance training. When considering that patients with COPD present alterations in autonomic cardiac modulation caused by the disease itself, it is necessary to investigate the behavior of the autonomic nervous system in relation to this type of exercise. Thus, the objective of this study was to compare the acute effects of resistance training with elastic tubes, elastic bands, and conventional weightlifitng on the behavior of cardiac autonomic modulation in post-exercise recovery in subjects with COPD. METHODS: Thirty-four subjects with COPD performed an single session of resistance training divided according to the therapeutic resource used: elastic tubes (n = 10), elastic bands (n = 11), and conventional bodybuilding (n = 13). For analysis of cardiac autonomic modulation, the heart rate was obtained beat to beat at rest and immediately after the end of the session for 60 min in a seated position. Heart rate variability indices were obtained in the time and frequency domains. RESULTS: The 3 therapeutic resource types used in the single session of resistance training promoted changes in heart rate variability linear indices in the time and frequency domains; however, post-exercise recovery time was similar for all protocols performed. CONCLUSIONS: After single resistance training the elastic tubes group presented a minimum alteration in the post-exercise recovery of cardiac autonomic modulation in the subjects with COPD; however, at 5 min after exercising, the subjects with COPD had already recovered. Therefore, if the purpose of the training is to restore autonomic cardiac modulation, the use of elastic tubes is suggested, when considering their low cost and versatility.

Post-exercise recovery of biological, clinical and metabolic variables after different temperatures and durations of cold water immersion: a randomized clinical trial.

BACKGROUND: Cold water immersion (CWI) is a commonly used recuperative strategy. However there is a lack of standardization of protocols considering the duration and temperature of application of the technique and the stress model. Therefore it is important to study the issue of dose response in a specific stress model. Thus the objective was to analyze and compare the effects of CWI during intense post-exercise recovery using different durations and temperatures of immersion. METHODS: One hundred and five male individuals were divided into five groups: one control group (CG) and four recovery groups (G1: 5' at 9±1 °C; G2: 5' at 14±1 °C; G3: 15' at 9±1 °C; G4: 15' at 14±1 °C). The volunteers were submitted to an exhaustion protocol that consisted of a jump program and the Wingate Test. Immediately after the exhaustion protocol, the volunteers were directed to a tank with water and ice, where they were immersed for the recovery procedure, during which blood samples were collected for later lactate and creatine kinase (CK) analysis. Variables were collected prior to the exercise and 24, 48, 72, and 96 hours after its completion. RESULTS: For the CK concentration, 15 minutes at 14 °C was the best intervention option, considering the values at 72 hours after exercise, while for the moment of peak lactate an advantage was observed for immersion for 5 minutes at 14 °C. Regarding the perception of recovery, CWI for 5 minutes at 14 °C performed better long-term, from the time of the intervention to 96 hours post-exercise. For pain, no form of immersion responded better than the CG at the immediately post-intervention moment. CONCLUSIONS: There were no differences in behavior between the CWI intervention groups for the outcomes studied.

Analysis of agreement between cardiac risk stratification protocols applied to participants of a center for cardiac rehabilitation.

BACKGROUND: Cardiac risk stratification is related to the risk of the occurrence of events induced by exercise. Despite the existence of several protocols to calculate risk stratification, studies indicating that there is similarity between these protocols are still unknown. OBJECTIVE: To evaluate the agreement between the existing protocols on cardiac risk rating in cardiac patients. METHOD: The records of 50 patients from a cardiac rehabilitation program were analyzed, from which the following information was extracted: age, sex, weight, height, clinical diagnosis, medical history, risk factors, associated diseases, and the results from the most recent laboratory and complementary tests performed. This information was used for risk stratification of the patients in the protocols of the American College of Sports Medicine, the Brazilian Society of Cardiology, the American Heart Association, the protocol designed by Frederic J. Pashkow, the American Association of Cardiovascular and Pulmonary Rehabilitation, the Société Française de Cardiologie, and the Sociedad Española de Cardiología. Descriptive statistics were used to characterize the sample and the analysis of agreement between the protocols was calculated using the Kappa coefficient. Differences were considered with a significance level of 5%. RESULTS: Of the 21 analyses of agreement, 12 were considered significant between the protocols used for risk classification, with nine classified as moderate and three as low. No agreements were classified as excellent. Different proportions were observed in each risk category, with significant differences between the protocols for all risk categories. CONCLUSION: The agreements between the protocols were considered low and moderate and the risk proportions differed between protocols.

The effects of cold water immersion with different dosages (duration and temperature variations) on heart rate variability post-exercise recovery: A randomized controlled trial.

OBJECTIVES: The aim of the present study was to investigate the effects of cold water immersion during post-exercise recovery, with different durations and temperatures, on heart rate variability indices. DESIGN: Hundred participants performed a protocol of jumps and a Wingate test, and immediately afterwards were immersed in cold water, according to the characteristics of each group (CG: control; G1: 5' at 9±1°C; G2: 5' at 14±1°C; G3: 15' at 9±1°C; G4: 15' at 14±1°C). METHODS: Analyses were performed at baseline, during the CWI recuperative technique (TRec) and 20, 30, 40, 50 and 60min post-exercise. The average HRV indices of all RR-intervals in each analysis period (MeanRR), standard deviation of normal RR-intervals (SDNN), square root of the mean of the sum of the squares of differences between adjacent RR-intervals (RMSSD), spectral components of very low frequency (VLF), low frequency (LF) and high frequency (HF), scatter of points perpendicular to the line of identity of the Poincaré Plot (SD1) and scatter points along the line of identity (SD2) were assessed. RESULTS: Mean RR, VLF and LF presented an anticipated return to baseline values at all the intervention groups, but the same was observed for SDNN and SD2 only in the immersion for 15min at 14°C group (G4). In addition, G4 presented higher values when compared to CG. CONCLUSIONS: These findings demonstrate that if the purpose of the recovery process is restoration of cardiac autonomic modulation, the technique is recommended, specifically for 15min at 14°C.

Effects of auditory stimulation with music of different intensities on heart period.

Various studies have indicated that music therapy with relaxant music improves cardiac function of patients treated with cardiotoxic medication and heavy-metal music acutely reduces heart rate variability (HRV). There is also evidence that white noise auditory stimulation above 50 dB causes cardiac autonomic responses. In this study, we aimed to evaluate the acute effects of musical auditory stimulation with different intensities on cardiac autonomic regulation. This study was performed on 24 healthy women between 18 and 25 years of age. We analyzed HRV in the time [standard deviation of normal-to-normal RR intervals (SDNN), percentage of adjacent RR intervals with a difference of duration >50 ms (pNN50), and root-mean square of differences between adjacent normal RR intervals in a time interval (RMSSD)] and frequency [low frequency (LF), high frequency (HF), and LF/HF ratio] domains. HRV was recorded at rest for 10 minutes. Subsequently, the volunteers were exposed to baroque or heavy-metal music for 5 minutes through an earphone. The volunteers were exposed to three equivalent sound levels (60-70, 70-80, and 80-90 dB). After the first baroque or heavy-metal music, they remained at rest for 5 minutes and then they were exposed to the other music. The sequence of songs was randomized for each individual. Heavy-metal musical auditory stimulation at 80-90 dB reduced the SDNN index compared with control (44.39 ± 14.40 ms vs. 34.88 ± 8.69 ms), and stimulation at 60-70 dB decreased the LF (ms(2)) index compared with control (668.83 ± 648.74 ms(2) vs. 392.5 ± 179.94 ms(2)). Baroque music at 60-70 dB reduced the LF (ms(2)) index (587.75 ± 318.44 ms(2) vs. 376.21 ± 178.85 ms(2)). In conclusion, heavy-metal and baroque musical auditory stimulation at lower intensities acutely reduced global modulation of the heart and only heavy-metal music reduced HRV at higher intensities.

Effects of functional training on geometric indices of heart rate variability.

BACKGROUND: Geometric methods provide an analysis of autonomic modulation using the geometric properties of the resulting pattern, and represent an interesting tool in the analysis of heart rate variability (HRV). The aim of this study was to evaluate the impact of functional training on cardiac autonomic modulation in healthy young women using the geometric indices of HRV. METHODS: Data were analyzed from 29 women, and were stratified into a functional training group (FTG, n = 13; 23.00 ± 2.51 years; 21.90 ± 2.82 kg/m2) and a control group (CG, n = 16; 20.56 ± 1.03 years; 22.12 ± 3.86 kg/m2). The FTG received periodized functional training for 12 weeks. The cardiac autonomic modulation of both groups was evaluated before and after this training, and a qualitative analysis was performed using the Poincaré plot. RESULTS: There was a significant increase in the difference of the triangular index (RRTri), SD1, SD2, and RR intervals in the FTG as compared to the CG, and the qualitative analysis from the Poincaré plot showed an increase in the dispersion of beat-to-beat and long-term RR intervals in the functional group after training. No changes were observed in the triangular interpolation of RR interval histogram (TINN) or SD1/SD2. CONCLUSION: Functional training had a beneficial impact on autonomic modulation, as characterized by increased parasympathetic activity and overall variability, thus highlighting the clinical usefulness of this type of training.