Relationship between moderate-to-vigorous, light intensity physical activity and sedentary behavior in a prospective cohort of older French adults: a 18-year follow-up of mortality and cardiovascular events ─ the PROOF cohort study.

Background: It is well documented that moderate-to-vigorous intensity physical activity (MVPA) is effective in the prevention of major chronic diseases. Even though the current international physical activity (PA) guidelines still mainly focus on MVPA, the topic of the most recent epidemiological studies has shifted from MVPA to light intensity physical activity (LPA), owing to the necessity of promoting all activities vs. sedentary behavior (SB). However, the evidence remains currently limited. Thus, the clarification of the effects of LPA and the close relationship with SB is crucial to promote public health. Method: PA and SB were assessed by a validated self-administered questionnaire (POPAQ) investigating 5 different types of PA during the 7 previous days. PA was measured in metabolic equivalent of task (MET)-h, which refers to the amount of energy (calories) expended per hour of PA. SB was measured in hour/day. Medical histories and examinations were taken during each clinical visit to determine clinical events. All-cause mortality was established using the same procedure and by checking local death registries. The relationships between the intensity of PA (light, moderate to vigorous) and mortality and between the periods of SB and mortality or CV events were analyzed by splines and COX models, adjusted for sex and year of birth. Results: From the 1011 65-year-old subjects initially included in 2001 (60% women), the last 18-year follow-up has been currently completed since 2019. A total of 197 deaths (19.2%, including 77 CV deaths) and 195 CV events (19.3%) were reported. Averages (standard deviation) of MVPA, LPA and SB were, respectively, 1.2 h/d (0.3), 5.8 h/d (1.1), and 6.6 h/d (2.3). For all-cause deaths, as well as CV deaths, the splines were significant for LPA (p = 0.04 and p = 0.01), and MVPA (p < 0.001 and p < 0.001), but not for SB (p = 0.24 and p = 0.90). There was a significant reduction in CV events when SB was decreasing from 10.9 to 3.3 h/d. Conclusion: The PROOF cohort study shows a clear dose-response between the dose of LPA, MVPA, SB and risk of mortality. These findings provide additional evidence to support the inclusion of LPA in future PA guidelines.

Longer-term effects of supervised physical activity on obstructive sleep apnea and subsequent health consequences.

Although recent trials have shown promising benefits of exercise on obstructive sleep apnea (OSA) severity, the long-term effect of these interventions remains unknown. The aim of this study was to assess the effect of a 9-month community physical activity program on OSA severity one year later in free-living conditions. OSA patients, previously included in a 9-month randomized controlled trial (EXESAS study) evaluating the effects of supervised community physical activity on OSA severity, were invited to participate in an extra one-year observational study. Twenty-eight patients completed the study. Although OSA severity did not significantly worsen over the real-life period (9 to 21 months of follow-up), reductions in apnea-hypopnea index (AHI) and oxygen desaturation index were no longer significant after 21 months of follow-up compared to baseline (baseline AHI: 22.2 ± 6.3 /h; 9 months: 16.3 ± 6.4 /h; 21 months: 18.7 ± 8.9 /h). Benefits observed at 9 months on daytime sleepiness and mental health were preserved at 21 months, whereas cardiorespiratory fitness slightly decreased. Per-protocol analysis revealed that patients who stopped exercise at 9 months had worsened OSA severity compared to those who continued exercise during the real-life period (AHI: +9.0 ± 8.8 vs. -1.3 ± 5.3 /h; p < .01). In conclusion, our study suggested that improvements in OSA severity remain transient and is dependent on long-term adherence to regular physical activity practice.

Effect of exercise training on heart rate variability in patients with obstructive sleep apnea: A randomized controlled trial.

While obstructive sleep apnea (OSA) increases chemoreflex, leading to an autonomic dysfunction in the long term, no studies have yet assessed the potential benefit of exercise on cardiac autonomic activity in these patients. The aim of this study was to evaluate potential improvement in cardiac autonomic function (CAF) measured through heart rate variability (HRV) after a 9-month physical activity program in patients with OSA. Seventy-four patients with moderate OSA, aged 40-80 years, were randomly assigned to an exercise group (n = 36, 3 × 1 h/wk) or a control group (n = 38) during 9 months. Linear and nonlinear HRV parameters were measured during night using a Holter ECG. After 9 months, mean R-R intervals increased in the exercise group without any changes in HRV parameters, while controls decreased global (standard deviation of normal-to-normal intervals, total power) and parasympathetic (root mean square successive difference of N-Ns, very low frequency, high frequency, and standard deviation of the instantaneous beat-to-beat variability) indices of HRV (P < 0.05 for all). Significant correlations with moderate effect size were found between changes in apnea severity and changes in R-R intervals (P < 0.05). Improvement in moderate-to-vigorous physical activity was also correlated to improvement in nocturnal oxygen parameters (P < 0.05). In conclusion, supervised community physical activity may prevent a decline in nighttime CAF observed in nontreated community-dwelling patients with moderate OSA over a 9-month period. Thus, beyond apnea-hypopnea index improvement, exercise may be cardioprotective in OSA patients through bradycardia, CAF preservation, and VO2peak increase.

Even a Previous Light-Active Physical Activity at Work Still Reduces Late Myocardial Infarction and Stroke in Retired Adults Aged>65 Years by 32%: The PROOF Cohort Study.

Background: Work may contribute significantly to daily physical activity (PA) and sedentary behavior (SB). Physical inactivity and SB at work might be two major risk factors for premature morbidity. Therefore, the aim of this research was to describe self-reported past PA and SB at work and during leisure time within the PROOF cohort subjects, and to determine consequences of PA and SB on late health of these now retired workers. Material and Methods: The PROOF cohort study was used to prospectively allow assessment of the predictive value of PA and SB at work and during leisure time among a healthy retired French population, with regard to cardiovascular and cerebrovascular events. PA (MET-h/week) and SB (h/d) were assessed using the Population Physical Activity Questionnaire (POPAQ) and the modified Global Physical Activity Questionnaire (GPAQ). Odds ratios (ORs with 95% CIs) for cardiovascular and cerebrovascular events were associated with each level of PA at work: light (<3 METs), moderate (3-5.9 METs), vigorous (≥6 METs) and were compared to SB at work. Results: Out of the 1011 65-year-old subjects initially included, the 15-year follow-up has been currently completed for 688 (68%) subjects; 89 deaths (all-cause mortality, 9%) and 91 fatal and non-fatal cardiovascular and cerebrovascular events (9%), were reported. An active work (light, moderate, or vigorous intensity) was associated with a 21% reduced risk of cardiovascular (myocardial infarction) and cerebrovascular events (stroke) (OR = 0.79, 95% CI: 0.32-0.91, p < 0.02) compared to sedentary work. This relationship was already significant for light intensity work (32%; i.e., OR = 0.68, 95% CI: 0.31-0.87, p < 0.02). Conclusion: There is strong causal evidence linking PA and SB at work with late cardiovascular and cerebrovascular disease. All in all, the risk for onset of myocardial infarction and stroke was lower among those who had a previous active work compared to those with previous sedentary work. Even previous light active work produced substantial health benefits. Clinical Trial Registration: www.ClinicalTrials.gov, identifier: NCT00759304.

Does Subjective Sleep Affect Bone Mineral Density in Older People with Minimal Health Disorders? The PROOF Cohort.

STUDY OBJECTIVES: Clinical and epidemiological studies suggest a relation between bone mineral density (BMD) and self-assessment of sleep with an effect on bone formation and osteoporosis (OS) risk in short and long sleepers. This study explores this association in a large sample of older subjects. METHODS: We examined 500 participants without insomnia complaints aged 65.7 ± 0.8 y. Each participant had a full evaluation including anthropometric measurement, clinical examination and measurements of BMD at the lumbar spine and femoral sites by dual-energy X-ray absorptiometry. The daily energy expenditure (DEE) was measured by the Population Physical Activity Questionnaire. Sleep duration and quality were evaluated by the Pittsburgh Sleep Quality Index. The subjects were stratified into three groups according to sleep duration, i.e., short (< 6 h), normal (6-8 h), and long (≥ 8 h) sleepers. RESULTS: Osteopenia was found in 40% of the subjects at the femoral level and 43% at the vertebral level. The prevalence of OS was lower both at femoral (8%) and vertebral (12%) levels. Short, normal, and long sleepers accounted for 29%, 40%, and 31% of subjects, respectively. After adjustments for metabolic, anthropometric, and DEE, multinomial logistic regression analysis indicated that long sleepers were more likely to have femoral neck OS with a slight effect of DEE at vertebral spine. CONCLUSIONS: In a sample of older subjects, self-reported long sleep was the best predictor of OS risk at the femoral level. This finding suggests an association between OS and self-reported sleep duration in older subjects. CLINICAL TRIAL REGISTRATION: NCT 00759304 and NCT 00766584.

Risk factors of osteoporosis in healthy elderly with unrecognized obstructive sleep apnea: role of physical activity.

OBJECTIVE: Several studies suggest a relationship between bone mineral density (BMD) anthropometric and metabolic variables, and obstructive sleep apnea (OSA); all of these factors have an effect on osteoporosis (OS) risk. This cross-sectional study explores these associations in a large sample of older subjects with and without OSA. METHODS: Volunteers were recruited from the PROgnostic indicator OF cardiovascular and cerebrovascular events survey. A total of 461 subjects, aged 68.7 ± 0.8 years, were examined, blood samples were taken, and they were subjected to home polygraphy, assessment of daily energy expenditure (DEE), and dual-energy X-ray absorptiometry. RESULTS: Osteopenia (OP) was detected in 44% of subjects at the femoral and 39% at the vertebral level, while the prevalence of OS was lower at the femoral (4%) and vertebral (12%) levels. As expected, women had a higher prevalence of OP and OS. Subjects with OP and OS had a tendency to have lower DEE and values of obesity, apnea-hypopnea index (AHI), and indices of hypoxemia (ODI). At the correlation analyses, anthropometric factors and DEE were significantly related to BMD with a slight effect of indices of OSA severity. After adjustment for confounding variables, univariate and multivariate regression analyses showed a strong significant association between femoral and lumbar BMD and T-score and DEE without contribution of metabolic data and with a slight negative effect of respiratory factors. CONCLUSIONS: In this sample of the elderly, physical activity was the best predictor of OS with a slight effect of body mass index. The indices of OSA confirm their protective effect on bone mineral density.

Relationship between cranial mechanics and dysmorphic dentofacial characteristics: a cross-sectional study.

AIMS: The aim of the present study was to evaluate if cranial dysfunctions felt by osteopaths could correlate with sagittal dysmorphologies diagnosed by orthodontists, using cephalometric traces in the sagittal plane. Metholology: One hundred and six children between 6 and 12 years old (42 boys and 64 girls) were tested by an osteopath to determine if the cranial movement felt was considered to be eased in flexion or extension. To test reproducibility intra-operator, 27 randomly selected subjects were tested twice, at a one-month interval by the same osteopath before the start of their orthodontic treatment. These tests were then correlated with a cephalometric analysis of the sagittal plane to determine what type of dysmorphology existed, if any, as well as the angle of the spheno-occipital synchondrosis (SOS). RESULTS: Practitioners systematically found more cranial movement in extension for all the bones in patients in skeletal class II than in the others. Similarly, they systematically found more cranial movement in flexion in patients in skeletal class III than in the other skeletal classes. However, there was no significant difference found in SOS angulation between skeletal classes I, II, and III. DISCUSSION: This study tends to confirm the correlation, described previously by orthodontists, between the mobility of the bones of the cranial vault and dysmorphic dentofacial characteristics in the sagittal plane. Anomalies during development could lead to the typical cranial characteristics of flexion or extension. As such, these situations could be related to skeletal classes III and II respectively.

Identification and comparison of the predictors of maximal inspiratory force and handgrip in a healthy elderly population. The proof study.

BACKGROUND: A severe weakness of peripheral muscles occurs in half of the persons aged 80 years or older. The common factors between muscle depletion and reduced respiratory strength have not yet been established. OBJECTIVE: In the subjects of the Proof cohort, we aimed to identify, among body composition, pulmonary function and energy expenditure parameters, the predictors of maximal inspiratory pressure (MIP) as an index of respiratory muscle strength and handgrip (HG) as an index of peripheral muscle strength. SUBJECTS AND METHODS: In 375 healthy elderly subjects aged 72 ± 1 years, fat mass (FM) and fat free mass (FFM) were assessed by DEXA, the last being also indexed to height (FFMI). Spirometry was performed and daily energy expenditure (DEE) was estimated by a questionnaire. After three years, MIP and HG of the dominant arm were determined and the predicting value of pulmonary function tests, body composition and DEE on these parameters was tested. RESULTS: Mean MIP and HG were 77 ± 26% and 106 ± 19% of the predicted value (%pred) with 90 (24%) and 30 (8%) subjects below standards, respectively. There was a significant but weak correlation between MIP%pred and HG%pred (r = 0.175, p < 0.001). Logistic regression showed that low MIP was predicted by trunk FFM and FFMI in women, and DEE in men. Low HG was predicted by trunk FM in men only. CONCLUSIONS: The predictors of a reduction of MIP in the elderly differ from those of HG, suggesting a differential regulation of respiratory muscle and arm strength.

Modeling of performance and ANS activity for predicting future responses to training.

PURPOSE: Our aim was to assess whether we can predict satisfactorily performance in swimming and high frequency power (HF power) of heart rate variability from the responses to previous training. We have tested predictions using the model of Banister and the variable dose-response model. METHODS: Data came from ten swimmers followed during 30 weeks of training with performance and HF power measured each week. The first 15-week training period was used to estimate the parameters of each model for both performance and HF power. Both were then predicted in response to the training done during the second 15-week training period. The bias and precision were estimated from the mean and SD of the difference between prediction and actual value expressed as a percentage of performance or HF power at the first week. RESULTS: With the variable-dose response model, the bias for performance prediction was -0.24 ± 0.06 and the precision 0.69 ± 0.24% (mean ± between-subject SD). For HF power, the bias was 0 ± 21 and the precision 22 ± 8%. When HF power was transformed into performance using a quadratic relation in each swimmer established from the first 15-week period, the bias was 0.18 ± 0.74 and the precision 0.80 ± 0.30%. No clear trend in the error was observed during the second period. CONCLUSIONS: This study showed that the modeling of training effects on performance allowed accurate performance prediction supporting its relevance to control and predict week after week the responses to future training.

Predictors of physical activity in patients with heart failure: a questionnaire study.

BACKGROUND: Adequate physical activity is believed to help decrease readmission and improve quality of life for patients with heart failure (HF). OBJECTIVE: The aim of this study was to explore the predictors of physical activity level 1 month after discharge from hospital in Taiwanese patients with HF. METHOD: A prospective research design was used. Overall, 111 patients with HF from a medical center in Southern Taiwan were recruited. Symptomatic distress, self-efficacy for physical activity, physical activity knowledge, and demographic and disease characteristics of patients with HF were collected at their discharge. One month later, patients' total daily energy expenditure (DEE), DEE for low-intensity physical activities (PA(low) DEE; strictly <3 metabolic equivalents [METs]), DEE for high-intensity physical activities (PA(high) DEE; 3-5 METs), and DEE for intensive-intensity physical activities (PA(intensive) DEE; strictly >5 METs) were collected. RESULTS: The mean total DEE was 8175.85 ± 2595.12 kJ 24 h, of which 19.12% was for PAlow DEE, 7.20% was for PA(high) DEE, and only 1.42% was for PA(intensive) DEE. Body mass index (BMI), age, self-efficacy for instrumental activities of daily living, and educational level were predictors of total DEE of patients with HF 1 month after discharge. Self-efficacy for instrumental activities of daily living, gender, and BMI were predictors of PA(high) DEE. Age, BMI, and symptom distress were predictors of PA(intensive) DEE. CONCLUSIONS: Taiwanese patients with HF practiced lower intensity physical activities. Factors related to physical activity of patients with HF in Taiwan were similar to those of Western countries. Nurses should emphasize the importance of physical activity to patients with HF who are male, of older age, with lower educational level, or with lower BMI. Improving self-efficacy for instrumental activities and decreasing symptom distress should be incorporated into discharge planning programs for patients with HF.

[Establishment of a pilot study of awareness retraining in physical activity in two selected populations of patients with breast cancer]. / Mise en place d'une étude pilote de sensibilisation au réentraînement à l'activité physique dans deux populations sélectionnées atteintes d'un cancer du sein.

The purpose of this study is to measure the impact of an educational program to raise awareness of the increased spending energy in two different population of patients with breast cancer by using the questionnaire POPAQ (Population Physical Activity Questionnaire). This is a prospective study including two groups of 15 consecutive breast cancer patients (≤ 50 years Group 1 and Group 2 > 50 and < 70 years) followed in the department of radiotherapy at the Institute of Cancer of the Loire from January to July 2011. A questionnaire of physical activity assessment was used at two different times before the diagnosis/treatment of breast cancer (t0) and at 6 months (t6) to measure the impact of the awareness method. Comparison of different measures of daily energy expenditure (t0) between groups 1 and 2 was statistically significant (1,1803 and 9434 kJ/24 h, respectively, p = 0.0005). Daily energy expenditure of professional activity was statistically different between the two groups (1437 and 457 kJ/24 h, in groups 1 and 2, respectively; p = 0.003). Between t0 and t6, we observed a significant decrease in total energy consumption in group 1 (1,1803 to 1,0876 kJ/24 h) while there was no significant change between the group 2, except energy expended at rest (basal metabolism). There were differences in daily energy expenditure based on age may influence behavioral patterns deal with energy expenditure in physical activities. Tomorrow's challenges are to provide re-entrainment programs tailored to targeted populations.

A model for the training effects in swimming demonstrates a strong relationship between parasympathetic activity, performance and index of fatigue.

Competitive swimming as a physical activity results in changes to the activity level of the autonomic nervous system (ANS). However, the precise relationship between ANS activity, fatigue and sports performance remains contentious. To address this problem and build a model to support a consistent relationship, data were gathered from national and regional swimmers during two 30 consecutive-week training periods. Nocturnal ANS activity was measured weekly and quantified through wavelet transform analysis of the recorded heart rate variability. Performance was then measured through a subsequent morning 400 meters freestyle time-trial. A model was proposed where indices of fatigue were computed using Banister's two antagonistic component model of fatigue and adaptation applied to both the ANS activity and the performance. This demonstrated that a logarithmic relationship existed between performance and ANS activity for each subject. There was a high degree of model fit between the measured and calculated performance (R(2)=0.84±0.14,p<0.01) and the measured and calculated High Frequency (HF) power of the ANS activity (R(2)=0.79±0.07, p<0.01). During the taper periods, improvements in measured performance and measured HF were strongly related. In the model, variations in performance were related to significant reductions in the level of 'Negative Influences' rather than increases in 'Positive Influences'. Furthermore, the delay needed to return to the initial performance level was highly correlated to the delay required to return to the initial HF power level (p<0.01). The delay required to reach peak performance was highly correlated to the delay required to reach the maximal level of HF power (p=0.02). Building the ANS/performance identity of a subject, including the time to peak HF, may help predict the maximal performance that could be obtained at a given time.

[Assessment of daily physical activity of breast cancer patients and comparison with two control populations]. / Quantification de l'activité physique journalière des patientes traitées pour un cancer du sein et comparaison avec deux populations témoins.

OBJECTIVE: The purpose is to assess the physical activity of breast cancer patients using a questionnaire, the Population Physical Activity Questionnaire (POPAQ) and to compare the data with those from two female populations: one healthy population and one with a previous history of cardiovascular disease. PATIENTS AND METHODS: This prospective study included 104 consecutive breast cancer patients who were addressed at the radiation oncology department, Institut de cancérologie de la Loire from March to July 2010. A questionnaire using factorial method was used for assessment of physical activity. RESULTS: In the study population, the rest energetic expenditures of physical energy related to both rest activity and low intensity activity were higher than in the healthy patients (5,292±1,376 versus 5,520±1,248 kJ/24 h, P<0.05 and 2,583±681 versus 2,494±558 kJ/24 h, P<0.05, respectively). Conversely, the energetic expenditures of physical energy related to both high physical activity and intensive physical activity were lower than in the healthy population (882±441 versus 1,560±868 kJ/24 h, P<0.05 et 210±274 versus 340±621 kJ/24 h, P<0.05, respectively). CONCLUSION: The POPAQ allows quantifying the daily physical activity and seems feasible in clinical routine in breast cancer patients. In our study, it was found that the physical activity of those patients was significantly different from that of a healthy population. Further investigations are necessary for better defining the true impact of such differences in terms of incidence and prognostic for mammary carcinoma.

Level of physical activity at the age of 65 predicts successful aging seven years later: the PROOF study.

BACKGROUND: Physical activity has a pleiotropic effect and is a significant factor in successful aging. This study aims to quantify the relationship between the physical activity of a 65-year-old cohort and the level of life satisfaction and self-rated health 7 years later. METHODS: A total of 988 questionnaires were sent by mail to a representative sample of healthy pensioners. Life satisfaction and health status were estimated on two visual analogical scales in answer to the following questions: (1) How would you estimate your state of health? and (2) Are you generally satisfied with your life? The level of physical activity was estimated using a questionnaire which enabled us to calculate: (1) Daily energy expenditure (DEE), (2) physical activity energy expenditure (PAEE), (3) daily energy expenditure higher than 5 metabolic equivalents (METs) (DEQisa), (4) Activity index (PAEE/DEE), (5) VO(2) peak. RESULTS: In all, 686 responses were validated. The average age was 72.9 ± 1.2 years old with 59.5% of women (n = 408). Amongst the sample, 98.8% (n = 676) lived in their own homes and 25.2% (n = 172) lived alone. Mean DEE was 10.365 ± 1.964 kJ/24 h, mean PAEE was 4.479 ± 1.170 kJ/24 h, mean activity index was 0.42 ± 0.05, and mean estimated oxygen uptake (VO(2)) peak was 22.5 ± 1.6 mL/min per kg. Activity index and VO(2) peak were the variables most significantly correlated with self-rated health (p = 0.0032 and p = 0.0011, respectively) and life satisfaction (p = 0.0117 and p = 0.0053). CONCLUSIONS: Energy spent in activity and VO(2) peak estimated from DEE, measured at the age of 65, appear to be strong predictors of well-being 7 years later.

Increased waist circumference is the component of metabolic syndrome the most strongly associated with elevated C-reactive protein in elderly.

BACKGROUND: Metabolic syndrome is associated with higher C-reactive protein (CRP) serum levels, a common biological marker of inflammation. However, the respective contribution of each component of metabolic syndrome to the inflammation has not been established. The aim of the present study was to assess the strength of the association between metabolic syndrome components and CRP in elderly subjects. METHODS: This was an observational, cross-sectional study on 921 volunteers (65.6 ± 0.8 years old) from the PROOF (PROgnostic indicator OF cardiovascular and cerebrovascular events) Study. Anthropometric, biological, and clinical parameters were evaluated. Subjects with a CRP value less than 10 mg/L were considered. The relationships between the metabolic syndrome components and CRP tertiles were evaluated using logistic regression analysis. RESULTS: After adjustment for gender and for body mass index, metabolic syndrome and high-CRP tertile were significantly associated [odds ratio (OR)=2.37, 95% confidence interval (CI) 1.46-3.87, P<0.001]. Waist circumference demonstrated the strongest association with the high-CRP tertile (OR=1.75, 95% CI 1.05-2.91, P<0.05). In addition, CRP levels significantly increased with the number of metabolic syndrome components. CONCLUSIONS: Among metabolic syndrome components, waist circumference showed the strongest association with the high-CRP tertile in elderly subjects. These findings help to explain the strong association between waist circumference and cardiovascular morbidity.

Remodeling of skeletal muscle microvasculature in sickle cell trait and alpha-thalassemia.

The influence of sickle cell trait and/or alpha-thalassemia on skeletal muscle microvascular network characteristics was assessed and compared with control subjects [hemoglobin (Hb) AA] in 30 Cameroonian residents [10 HbAA, 5 HbAA alpha-thalassemia (alpha-t), 6 HbAS, and 9 HbASalpha-t] matched for maximal work capacity and daily energy expenditure. Subjects performed an incremental exercise to exhaustion and underwent a muscle biopsy. Muscle fiber type and surface area were not different among groups. However, sickle cell trait (SCT) was associated with lower capillary density (P < 0.05), lower capillary tortuosity (P < 0.001), and enlarged microvessels (P < 0.01). SCT carriers had reduced counts of microvessels <5-microm diameter, but a higher percentage of broader microvessels, i.e., diameter >10 microm (P < 0.05). alpha-Thalassemia seemed to be characterized by a higher capillary tortuosity and unchanged capillary density and diameter. Thus, while SCT is a priori clinically benign, we demonstrate for the first time that significant remodeling of the microvasculature occurs in SCT carriers. These modifications may possibly reflect protective adaptations against hemorheological and microcirculatory dysfunction induced by the presence of HbS. The remodeling of the microvascular network occurs to a lesser extent in alpha-thalassemia. In alpha-thalassemic subjects, increased capillary tortuosity would promote oxygen supply to muscle tissues and might compensate for the lower Hb content often reported in those subjects.

Dominance in cardiac parasympathetic activity during real recreational SCUBA diving.

It was already established that exposure to hyperbaric conditions induces vagal-depended bradycardia but field study on autonomic nervous system (ANS) activity during self-contained underwater breathing apparatus (SCUBA) diving is lacking. The aim of the present study was to evaluate ANS modifications during real recreational SCUBA diving using heart rate variability analysis (timedomain, frequency-domain and Poincaré plot) in 10 experienced and volunteers recreational divers. Mean RR, root mean square of successive differences of interval (rMSSD), high frequency of spectral analysis and standard deviation 1 of Poincaré Plot increased (P < 0.05) during dive. Low frequency/high frequency ratio decreased during dive (P < 0.05) but increased after (P < 0.05). Recreational SCUBA diving induced a rise in vagal activity and a decrease in cardiac sympathetic activity. Conversely, sympathetic activity increases (P < 0.05) during the recovery.