Random forest algorithms to classify frailty and falling history in seniors using plantar pressure measurement insoles: a large-scale feasibility study.

BACKGROUND: Frailty and falls are two adverse characteristics of aging that impair the quality of life of senior people and increase the burden on the healthcare system. Various methods exist to evaluate frailty, but none of them are considered the gold standard. Technological methods have also been proposed to assess the risk of falling in seniors. This study aims to propose an objective method for complementing existing methods used to identify the frail state and risk of falling in older adults. METHOD: A total of 712 subjects (age: 71.3 ± 8.2 years, including 505 women and 207 men) were recruited from two Japanese cities. Two hundred and three people were classified as frail according to the Kihon Checklist. One hundred and forty-two people presented with a history of falling during the previous 12 months. The subjects performed a 45 s standing balance test and a 20 m round walking trial. The plantar pressure data were collected using a 7-sensor insole. One hundred and eighty-four data features were extracted. Automatic learning random forest algorithms were used to build the frailty and faller classifiers. The discrimination capabilities of the features in the classification models were explored. RESULTS: The overall balanced accuracy for the recognition of frail subjects was 0.75 ± 0.04 (F1-score: 0.77 ± 0.03). One sub-analysis using data collected for men aged > 65 years only revealed accuracies as high as 0.78 ± 0.07 (F1-score: 0.79 ± 0.05). The overall balanced accuracy for classifying subjects with a recent history of falling was 0.57 ± 0.05 (F1-score: 0.62 ± 0.04). The classification of subjects relative to their frailty state primarily relied on features extracted from the plantar pressure series collected during the walking test. CONCLUSION: In the future, plantar pressures measured with smart insoles inserted in the shoes of senior people may be used to evaluate aspects of frailty related to the physical dimension (e.g., gait and balance alterations), thus allowing assisting clinicians in the early identification of frail individuals.

Caffeine Consumption Is Associated With Higher Level of Physical Activity in Japanese Women.

Caffeine has been described as a sports performance-enhancing substance. However, it is unclear whether it can increase the level of physical activity (PA) in nonathletic individuals. This study investigates the relationship between daily caffeine consumption and (a) daily PA/fitness or (b) intervention-induced changes in PA in women and men. On the basis of responses to a dietary habit questionnaire, which included items on caffeinated beverages, 1,032 Japanese adults, were categorized into lower or higher caffeine consumption groups (relative to the median caffeine consumption). In each group, daily step count; sedentary time; and light, moderate, and vigorous PA outcomes were objectively measured. Physical fitness, including peak oxygen consumption, was also evaluated. The relationship between daily caffeine consumption and the change in the levels of PA was investigated in a subgroup of 202 subjects who participated in a 1-year PA counseling intervention. Women in the higher caffeine consumption group presented higher moderate-to-vigorous PA and step count compared with their counterparts in the lower consumption group (4.0 ± 2.1 vs. 3.3 ± 2.1 MET-hr/day, p < .001; 10,335 ± 3,499 vs. 9,375 ± 3,527 steps/day, p < .001). A significant positive correlation was noted between caffeine consumption and peak oxygen consumption among women (r = .15, p < .001). No caffeine-related effects were noted in men. The lower and higher caffeine consumption groups showed no significant differences in their levels of PA at the end of the 1-year intervention. Therefore, caffeine consumption appears to be associated with higher levels of PA in Japanese women. Further studies are needed to clarify this association.

Management of surgical instruments with radio frequency identification tags.

PURPOSE: To prevent malpractices, medical staff has adopted inventory time-outs and/or checklists. Accurate inventory and maintenance of surgical instruments decreases the risk of operating room miscounting and malfunction. In our previous study, an individual management of surgical instruments was accomplished using Radio Frequency Identification (RFID) tags. The purpose of this paper is to evaluate a new management method of RFID-tagged instruments. DESIGN/METHODOLOGY/APPROACH: The management system of RFID-tagged surgical instruments was used for 27 months in clinical areas. In total, 13 study participants assembled surgical trays in the central sterile supply department. FINDINGS: While using the management system, trays were assembled 94 times. During this period, no assembly errors occurred. An instrument malfunction had occurred after the 19th, 56th, and 73 th uses, no malfunction caused by the RFID tags, and usage history had been recorded. Additionally, the time it took to assemble surgical trays was recorded, and the long-term usability of the management system was evaluated. ORIGINALITY/VALUE: The system could record the number of uses and the defective history of each surgical instrument. In addition, the history of the frequency of instruments being transferred from one tray to another was recorded. The results suggest that our system can be used to manage instruments safely. Additionally, the management system was acquired of the learning effect and the usability on daily maintenance. This finding suggests that the management system examined here ensures surgical instrument and tray assembly quality.

Installation of a stationary high desk in the workplace: effect of a 6-week intervention on physical activity.

BACKGROUND: Extended sitting time at work is viewed as a crucial public health issue. Encouraging workers to stand during their office hours via the installation of standing desks maybe one effective option to combat this. Here, we investigate whether the installation of high desks in the workplace can induce positive changes in the amount of physical activity (PA) and thereby lead to subsequent improvements in anthropometric parameters. METHODS: Thirty-two white-collar workers (22 men and 10 women, mean age 44.2) were randomly divided into two groups. A randomised crossover trial was performed for 13 weeks. During the experimental period, subjects completed their office work in a standing position using stationary high desks (standing work, SW) for 10 hours per week or more (SW period). The subjects were asked to maintain their normal sitting working habits during the control period (CONT period). The primary outcome was PA, which was assessed objectively using a triaxial accelerometer during weekdays and weekends. The secondary outcomes were anthropometric measurements. For each group and each parameter, the mean values during each period were recorded and were compared by paired t test. RESULTS: The daily total PA (10.2 ± 2.4 vs. 9.7 ± 2.3 METs · h/day, P = 0.043), MVPA (4.2 ± 2.2 vs. 3.7 ± 1.8 METs · h/day, P = 0.025), time spent in moderate PA (58.2 ± 20.7 vs. 53.4 ± 17.0 min/day, P = 0.019) and time spent in MVPA (62.8 ± 25.1 vs. 57.0 ± 20.3 min/day, P = 0.019) were significantly higher during the SW period compared to the CONT period. A weekdays verses weekends subanalysis revealed that these parameters were significantly higher during the SW period compared to the CONT period during weekdays only. No significant differences were noted before and after SW periods for most of the anthropometric measures, except waist circumference (83.7 ± 7.9 vs. 83.0 ± 7.9 cm, respectively, P = 0.007). CONCLUSIONS: Standing work, via the installation of high desks, significantly increases moderate to vigorous physical activity, especially on weekdays. TRIAL REGISTRATION: UMIN-CRT, UMIN000016731, 7th March 2015.

Objective Assessment of Physical Activity at Home Using a Novel Floor-Vibration Monitoring System: Validation and Comparison With Wearable Activity Trackers and Indirect Calorimetry Measurements.

BACKGROUND: The self-monitoring of physical activity is an effective strategy for promoting active lifestyles. However, accurately assessing physical activity remains challenging in certain situations. This study evaluates a novel floor-vibration monitoring system to quantify housework-related physical activity. OBJECTIVE: This study aims to assess the validity of step-count and physical behavior intensity predictions of a novel floor-vibration monitoring system in comparison with the actual number of steps and indirect calorimetry measurements. The accuracy of the predictions is also compared with that of research-grade devices (ActiGraph GT9X). METHODS: The Ocha-House, located in Tokyo, serves as an independent experimental facility equipped with high-sensitivity accelerometers installed on the floor to monitor vibrations. Dedicated data processing software was developed to analyze floor-vibration signals and calculate 3 quantitative indices: floor-vibration quantity, step count, and moving distance. In total, 10 participants performed 4 different housework-related activities, wearing ActiGraph GT9X monitors on both the waist and wrist for 6 minutes each. Concurrently, floor-vibration data were collected, and the energy expenditure was measured using the Douglas bag method to determine the actual intensity of activities. RESULTS: Significant correlations (P<.001) were found between the quantity of floor vibrations, the estimated step count, the estimated moving distance, and the actual activity intensities. The step-count parameter extracted from the floor-vibration signal emerged as the most robust predictor (r2=0.82; P<.001). Multiple regression models incorporating several floor-vibration-extracted parameters showed a strong association with actual activity intensities (r2=0.88; P<.001). Both the step-count and intensity predictions made by the floor-vibration monitoring system exhibited greater accuracy than those of the ActiGraph monitor. CONCLUSIONS: Floor-vibration monitoring systems seem able to produce valid quantitative assessments of physical activity for selected housework-related activities. In the future, connected smart home systems that integrate this type of technology could be used to perform continuous and accurate evaluations of physical behaviors throughout the day.

Ultrasound monitoring of RBC aggregation as a real-time marker of the inflammatory response in a cardiopulmonary bypass swine model.

OBJECTIVES: In many pathological conditions, including high-risk surgery, the severity of the inflammatory response is related to the patient outcome. However, determining the patient inflammatory state presents difficulties, as markers are obtained intermittently through blood testing with long delay. RBC aggregation is a surrogate marker of inflammation that can be quantified with the ultrasound Structure Factor Size and Attenuation Estimator. The latter is proposed as a real-time inflammation monitoring technique for patient care. DESIGN: Ten swine underwent a 90-minute cardiopulmonary bypass, and surveillance was maintained during 120 minutes in the postbypass period. To promote the inflammatory reaction, lipopolysaccharide was administrated two times prior to surgery in six of those swine (lipopolysaccharide group). During the whole procedure, the Structure Factor Size and Attenuation Estimator cellular imaging method displayed a RBC aggregation index (W) computed from images acquired within the pump circuit and the femoral vein. Interleukin-6, interleukin-10, C-reactive protein, haptoglobin, immunoglobulin G, and fibrinogen concentrations were measured at specific periods. MAIN RESULTS: Compared with controls, the lipopolysaccharide group exhibited higher W within the pump circuit (p < 0.05). In the femoral vein, W was gradually amplified in the lipopolysaccharide group during cardiopulmonary bypass and the postbypass period (p < 0.05), whereas interleukin levels were higher in the lipopolysaccharide group but only at the end of cardiopulmonary bypass and beginning of postbypass (p < 0.05). CONCLUSIONS: Continuous RBC aggregation monitoring can characterize the evolving inflammatory response during and after cardiopulmonary bypass. The Structure Factor Size and Attenuation Estimator is proposed as a real-time noninvasive monitoring technique to anticipate inflammation-related complications during high-risk surgery or critical care situations. Because RBC aggregation promotes vascular resistance and thrombosis, W could also provide early information on vascular disorders in those clinical situations.

Body Cell Mass to Fat-Free Mass Ratio and Extra- to Intracellular Water Ratio Are Related to Maximal Oxygen Uptake.

Fat-free mass (FFM) is a heterogeneous compartment comprising body cell mass (BCM), intracellular water (ICW), extracellular solids, and extracellular water (ECW). The BCM/FFM and ECW/ICW ratios vary among individuals and decrease with age. This study aimed to determine whether BCM/FFM and ECW/ICW ratios are predictors of maximal oxygen uptake (V̇̇O2peak) independently of age, sex, and objectively measured physical activity (PA). A total of 115 Japanese males and females, aged 55.3 ± 8.0 years (mean ± standard deviation), were included in the study. Anthropometry, explosive leg muscle power, and V̇̇O2peak were measured, and BCM, FFM, ICW, and ECW were estimated. Step count and PA were objectively measured using a triaxial accelerometer. Blood flow volume was assessed using ultrasonography. BCM and ICW were negatively correlated with age, whereas FFM and ECW were not significantly correlated with age. FFM, ICW/ECW, BCM/FFM, step counts, moderate and vigorous PA, and leg muscle power were positively correlated with V̇̇O2peak, even after adjusting for age and sex (p < .05). Multiple regression analysis indicated that either BCM/FFM or ECW/ICW, leg power, and objectively measured PA were associated with V̇̇O2peak independent of age, sex, and FFM. Blood flow volume was significantly correlated with ECW (p < .05), but not with BCM. The BCM/FFM and ECW/ICW ratios were significant predictors of V̇̇O2peak, independent of age, sex, FFM, leg power, and objectively measured PA.

Step-count outcomes of 13 different activity trackers: Results from laboratory and free-living experiments.

BACKGROUND: Many activity trackers have been developed, but steps can still be inconsistent from one monitor to another. RESEARCH QUESTION: What are the differences and associations between the steps of 13 selected consumer-based and research-grade wearable devices during 1 standardized day in a metabolic chamber and 15-day free-living trials? METHODS: In total, 19 healthy adults between 21 and 50 years-old participated in this study. Participants were equipped with 12 accelerometer-based active trackers and one pedometer (Yamasa) in order to monitor the number of steps per day. The devices were worn on the waist (ActiGraph, Omron, Actimarker, Lifedorder, Withings, and Yamasa) or non-dominant wrist (Fitbit, Garmin, Misfit, EPSON, and Jawbone), or placed in a pocket (Omron CaloriScan, and TANITA). Participants performed structured activities over a 24 h period in a chamber (Standardized day), and steps were monitored in the same participants in free-living trials for 15 successive days using the same monitors (free-living days). RESULTS: When the 13 monitors were ranked by their steps, waist-worn ActiGraph was located at the center (7th) of the monitors both in the Standardized (12,252 ± 598 steps/day, mean ± SD) and free-living days (9295 ± 4027 steps/day). The correlation between the accelerometer-based devices was very high (r = 0.87-0.99). However, the steps of Yamasa was significantly lower in both trials than ActiGraph. The wrist-worn accelerometers had significantly higher steps than other devices both trials (P < 0.05). The differences between ActiGraph and Actimarker or Lifecorder was less than 100 steps/day in the Standardized day, and the differences between ActiGraph and Active Style Pro was less than 100 steps/day in the free-living days. Regression equation was also performed for inter-device compatibility. SIGNIFICANCE: Step obtained from the wrist-worn, waist-worn, and pocket-type activity trackers were significantly different from each other but still highly correlated in free-living conditions.

Effect of a 1-year intervention comprising brief counselling sessions and low-dose physical activity recommendations in Japanese adults, and retention of the effect at 2 years: a randomized trial.

BACKGROUND: In an effort to increase people's adherence to active lifestyles, contemporary physical activity (PA) guidelines now include low-dose PA. METHODS: PA was evaluated in 583 participants of the Nutritional and Physical Activity Intervention Study (NEXIS) cohort (30-65 years old); 349 inactive participants (MVPA, 2.7 ± 1.0 MET-h/day) were randomly assigned to the intervention or control groups, and 235 active participants participated in follow-up visits. The intervention aimed to increase MVPA and comprised five brief counseling sessions over 1 year. The 1-year target for the participant was increasing their step-count to 10,000 steps/d or +3000 steps/d, relative to the baseline score. The counseling sessions were designed to stimulate progressive changes in physical behaviors by recommendations promoting small and/or light-intensity bouts of PA. PA was measured at baseline, the end of the intervention, and 1 year after the intervention ended. Additionally, several nutrition, health, and fitness parameters were measured. RESULTS: Participants in the intervention group significantly increased their step-count from 8415 ± 1924 at baseline to 9493 ± 2575 at the end of the 1-year period. During the same period, MVPA significantly increased by 0.9 MET-h. The daily time spent in ≥ 3, ≥ 4 and ≥ 5 MET activities increased by 11, 6, and 3 min, respectively. This increase in PA remained observable 1 year after intervention concluded. The active group maintained higher physical activity levels throughout the two years. The intervention group showed smaller energy intakes at the end of the 2-year period. Significant correlations were noted between the 1-year change in MVPA and the change in resting heart rate (r = - 0.22), and between the 2-year change in MVPA and the change in waist circumference (r = - 0.08) and peak oxygen consumption capacity (r = 0.23) in the intervention group only. CONCLUSIONS: A prolonged and progressive PA intervention promoting small bouts of light-to-moderate PA may be used in healthy, not-optimally-active people to increase PA beyond the strict period of the intervention. Further studies are necessary to understand whether low-dose PA messages can be effective in initiating a progressive increase toward larger amounts of PA. TRIAL REGISTRATION: Clinical Trials.gov, NCT00926744, retrospectively registered.

Effects of hydration and dehydration on blood rheology in sickle cell trait carriers during exercise.

This study compared the hemorheological responses of a group of sickle cell trait (SCT) carriers with those of a control (Cont) group in response to 40 min of submaximal exercise (exercise intensity, 55% aerobic peak power) performed in two conditions: one with water offered ad libitum, i.e., the hydration (Hyd) condition, and one without water, i.e., the dehydration (Dehyd) condition. Blood and plasma viscosities, as well as red blood cell rigidity, were determined at rest, at the end of exercise, and at 2 h recovery with a cone plate viscometer at high shear rate and 37 degrees C. The SCT and Cont groups lost 1 +/- 0.7 and 1.6 +/- 0.6 kg of body weight, respectively, in the Dehyd condition, indicating a significant effect of water deprivation compared with the Hyd condition, in which body weight remained unchanged. Plasma viscosity increased with exercise and returned to baseline during recovery independently of the group and condition. As previously demonstrated, resting blood viscosity was greater in the SCT carriers than in the Cont group. Blood viscosity increased by the end of exercise and returned to baseline at 2 h recovery in the Cont group in both conditions. The blood viscosity of SCT carriers did not change in response to exercise in the Dehyd condition and remained elevated at 2 h recovery. This extended hyperviscosity, in association with other biological changes induced by exercise, could be considered as a risk factor for exercise-related events in SCT carriers, similar to vasoocclusive crises, notably during the recovery. In contrast, the Hyd condition normalized the hyperviscosity and red blood cell rigidity of the SCT carriers, with blood viscosity values reaching the same lower values as those found in the Cont group during the recovery. Adequate hydration of SCT carriers should be strongly promoted to reduce the clinical risk associated with potential hyperviscosity complications.

Patterns of exercise-related inflammatory response in sickle cell trait carriers.

OBJECTIVE: To clarify whether sickle cell trait (SCT) carriers (SCT group) present a specific postexercise inflammatory response to repeated and strenuous exercise. DESIGN: The patterns of inflammatory markers in response to repeated heavy exercise were investigated in SCT carriers (SCT group: eight men, 20.0+/-0.7 years) and subjects with normal haemoglobin (CONT group: seven men, 20.6+/-0.7 years). The exercise consisted of three successive maximal ramp exercise tests, interspaced with 10 min of recovery, and accomplished at room temperature. Blood was sampled at rest (T(R)), at the end of each of the three tests (T(1), T(2), T(3)) and during the immediate (T(1 h), T(2 h)) and late (T(24 h), T(48 h)) recovery periods. Standard haematological parameters and plasma levels of cytokines (TNFalpha, IL-6) and adhesion molecules: soluble L- and P-selectins (sL-selectin, sP-selectin), soluble vascular cell adhesion molecule-1 (sVCAM-1), soluble intracellular adhesion molecule-1 (sICAM-1) were measured. RESULTS: In both groups, the three successive maximal exercise bouts prompted an inflammatory response (ie, white blood cells and IL-6 levels increased in response to exercise). sICAM-1 and sVCAM-1 levels did not change during or after exercise and presented no difference between groups. However, during exercise, sL-selectin and sP-selectin kinetics differed between groups: sL-selectin increased earlier in the SCT group than in the CONT group, and sP-selectin statistically increased only in the SCT group. CONCLUSION: Although the data do not indicate an extended exercise inflammatory response in SCT carriers, a specific activation of the L- and P-selectins was observed. Further studies are needed to determine whether the selectins' changes are evidence of greater risk for SCT carriers during physical exercise in specific conditions or an indication of a protective mechanism mediated by the shedding process of adhesion molecules.

Random forest algorithms for recognizing daily life activities using plantar pressure information: a smart-shoe study.

BACKGROUND: Wearable activity trackers are regarded as a new opportunity to deliver health promotion interventions. Indeed, while the prediction of active behaviors is currently primarily relying on the processing of accelerometer sensor data, the emergence of smart clothes with multi-sensing capacities is offering new possibilities. Algorithms able to process data from a variety of smart devices and classify daily life activities could therefore be of particular importance to achieve a more accurate evaluation of physical behaviors. This study aims to (1) develop an activity recognition algorithm based on the processing of plantar pressure information provided by a smart-shoe prototype and (2) to determine the optimal hardware and software configurations. METHOD: Seventeen subjects wore a pair of smart-shoe prototypes composed of plantar pressure measurement insoles, and they performed the following nine activities: sitting, standing, walking on a flat surface, walking upstairs, walking downstairs, walking up a slope, running, cycling, and completing office work. The insole featured seven pressure sensors. For each activity, at least four minutes of plantar pressure data were collected. The plantar pressure data were cut in overlapping windows of different lengths and 167 features were extracted for each window. Data were split into training and test samples using a subject-wise assignment method. A random forest model was trained to recognize activity. The resulting activity recognition algorithms were evaluated on the test sample. A multi hold-out procedure allowed repeating the operation with 5 different assignments. The analytic conditions were modulated to test (1) different window lengths (1-60 seconds), (2) some selected sensor configurations and (3) different numbers of data features. RESULTS: A window length of 20 s was found to be optimum and therefore used for the rest of the analysis. Using all the sensors and all 167 features, the smart shoes predicted the activities with an average success of 89%. "Running" demonstrated the highest sensitivity (100%). "Walking up a slope" was linked with the lowest performance (63%), with the majority of the false negatives being "walking on a flat surface" and "walking upstairs." Some 2- and 3-sensor configurations were linked with an average success rate of 87%. Reducing the number of features down to 20 does not alter significantly the performance of the algorithm. CONCLUSION: High-performance human behavior recognition using plantar pressure data only is possible. In the future, smart-shoe devices could contribute to the evaluation of daily physical activities. Minimalist configurations integrating only a small number of sensors and computing a reduced number of selected features could maintain a satisfying performance. Future experiments must include a more heterogeneous population.

Red blood cell aggregation, aggregate strength and oxygen transport potential of blood are abnormal in both homozygous sickle cell anemia and sickle-hemoglobin C disease.

BACKGROUND: Recent evidence suggests that red blood cell aggregation and the ratio of hematocrit to blood viscosity (HVR), an index of the oxygen transport potential of blood, might considerably modulate blood flow dynamics in the microcirculation. It thus seems likely that these factors could play a role in sickle cell disease. DESIGN AND METHODS: We compared red blood cell aggregation characteristics, blood viscosity and HVR at different shear rates between sickle cell anemia and sickle cell hemoglobin C disease (SCC) patients, sickle cell trait carriers (AS) and control individuals (AA). RESULTS: Blood viscosity determined at high shear rate was lower in sickle cell anemia (n=21) than in AA (n=52), AS (n=33) or SCC (n=21), and was markedly increased in both SCC and AS. Despite differences in blood viscosity, both sickle cell anemia and SCC had similar low HVR values compared to both AA and AS. Sickle cell anemia (n=21) and SCC (n=19) subjects had a lower red blood cell aggregation index and longer time for red blood cell aggregates formation than AA (n=16) and AS (n=15), and a 2 to 3 fold greater shear rate required to disperse red blood cell aggregates. CONCLUSIONS: The low HVR levels found in sickle cell anemia and SCC indicates a comparable low oxygen transport potential of blood in both genotypes. Red blood cell aggregation properties are likely to be involved in the pathophysiology of sickle cell disease: the increased shear forces needed to disperse red blood cell aggregates may disturb blood flow, especially at the microcirculatory level, since red blood cell are only able to pass through narrow capillaries as single cells rather than as aggregates.

Relationships between hemodynamic, hemorheological and metabolic responses during exercise.

Aerobic performance is dependent on both cardio-respiratory and peripheral factors with hemodynamic parameters playing a major role. However, whether blood rheology might affect aerobic performance through an effect on hemodynamic factors is not known. The aim of the present study was to assess the relationships between hemodynamic, hemorheological and metabolic parameters in response to a sub-maximal cycling exercise protocol consisting of three successive levels of nine min duration (50, 100 and 150 W). Ten young sportsmen participated in the present study. Mean arterial pressure (MAP) was measured manually, with thoracic impedance used to monitor cardiac output (Qc): systemic vascular resistance (SVR) was then calculated. Whole blood viscosity (etab) was measured and used to calculate systemic vascular hindrance. Hematocrit (Hct) was determined by micro-centrifugation and red blood cell (RBC) deformability (EI) was determined by ecktacytometry. A breath-by-breath gas analyzer was used to measure oxygen uptake (VO2); the Fick equation was used to calculate arterio-venous oxygen difference [(a-v)O(2)] from VO(2) and Qc. All measurements were performed at rest, during exercise and during recovery. Compared to baseline, Qc, MAP, Hct, EI, VO(2), and (a-v)O(2) increased during exercise. etab increased above baseline only at 150 W and remained elevated during recovery; the increase in etab during the last level of exercise was associated with a decrease of SVR and systemic vascular hindrance. There was a significant negative correlation between EI and SVR (r=-0.35, p<0.01) and a significant positive relationship between EI and (a-v)O(2) (r=0.35, p<0.01) and between EI and VO(2) (r=0.37, p<0.01) across all exercise workloads, thus suggesting a potential role for RBC deformability as a factor affecting aerobic performance via oxygen delivery to tissues. These data lend support to the concept that hemorheological parameters may contribute to hemodynamic and cardio-respiratory adaptations in response to exercise in moderately trained sportsmen.

Effects of storage duration and temperature of human blood on red cell deformability and aggregation.

Blood samples used in hemorheological studies may be stored for a period of time, the effects of storage have yet to be fully explored. This study evaluated the effects of storage temperature (i.e., 4 degrees C or 25 degrees C) and duration on RBC deformability and aggregation for blood from healthy controls and from septic patients. Our results indicate that for normal blood, RBC deformability over 0.3-50 Pa is stable up to six hours regardless of storage temperature; at eight hours there were no significant differences in EI but SS1/2 calculated via a Lineweaver-Burk method indicated impaired deformability. Storage temperature affected the stable period for RBC aggregation: the safe time was shorter at 25 degrees C whereas at 4 degrees C aggregation was stable up to 12 hours. Interestingly, blood samples from septic patients were less affected by storage. Blood can thus be stored at 25 degrees C for up to six hours for deformability studies, but should be limited to four hours for RBC aggregation; storage at 4 degrees C may prolong the storage period up to 12 hours for aggregation but not deformability measurements. Therefore, the time period between sampling and measurement should be as short as possible and reported together with results.

Sampling time after tourniquet removal affects erythrocyte deformability and aggregation measurements.

Venipuncture procedures are widely thought to influence biochemical, hematological or hemorheological measurements. In line with the preparation of the new Guidelines for the standardization of hemorheological measurement, we compared various blood rheological parameters (i.e., red blood cell deformability and aggregation indices) assessed in blood samples obtained after 5, 30, 60 and 90 s following the tourniquet removal and a blood sample obtained without applying a tourniquet (control sample). A slight but significant improvement in red blood cell (RBC) deformability after the removal of tourniquet compared to the control sample was observed. RBC deformability was maximal in the samples obtained 30 s after tourniquet removal and remained slightly higher than the control in the following samples (at 60 and 90 s after tourniquet removal). The aggregation index (AI) decreased with time after tourniquet removal reaching significantly lower values than the control at 90 s after tourniquet removal. This finding was supported by a greater half time for RBC aggregation in the samples obtained 60 and 90 s after tourniquet removal. In conclusion, this study revealed that RBC deformability and aggregation might be significantly altered in the samples obtained after the application and removal of a tourniquet, as a part of the blood sampling procedure. Recommendation "remove the tourniquet at least 5 s prior to the start of blood sampling" may need to be revised.

Cardiorespiratory responses during three repeated incremental exercise tests in sickle cell trait carriers.

This study investigated the cardioventilatory responses during heavy exercise in sickle cell trait carriers (SCTc) and subjects with normal hemoglobin (control group). Eight SCTc and six control subjects repeated three incremental exercise tests (Iet) separated by 10-min recoveries. Cardioventilatory parameters were analyzed at rest and during the first and third Iet. No significant difference in the ventilatory parameters [notably, maximal oxygen uptake (VO2max) and the ventilatory thresholds] was observed between the two groups. The time course of power output showed a significant difference between the first and third Iet from 80% of VO2max to VO2max (P < 0.05) in both groups. In conclusion, SCTc exhibited normal ventilatory responses during three successive Iet, which strongly suggests that this population, despite the presence of HbS in their red blood cells, is not limited during this type of aerobic exercise.

Blood rheology abnormalities and vascular cell adhesion mechanisms in sickle cell trait carriers during exercise.

Sickle cell trait (SCT) is usually considered a benign disorder compared with sickle cell anemia (SS hemoglobinopathy). However, several authors have reported cases of exercise-related sudden death in this population. Among the mechanisms that could be involved in these fatal complications, vaso-occlusive processes, such as those occurring in SS hemoglobinopathy, may play a role. In sickle cell anemia, these vaso-occlusive processes involve inflammatory and adhesion molecules such as the cell adhesion molecules (CAM family), which play a role in the firm adhesion of reticulocytes and leukocytes to endothelial cells, and the selectins, which play a role in leukocyte and platelet rolling on the vascular wall. Recent results suggest that adhesion phenomena could be amplified in SCT carriers during exercise compared with non-carriers. Other mechanisms like alterations in blood coagulation and/or hemorheological properties can also favor the occurrence of vaso-occlusive processes. Although few studies have reported coagulation disturbances in SCT carriers at rest, we recently observed no difference between this population and control subjects in response to exercise. In contrast, by studying the behavior of several hemorheological parameters in response to several types of exercise, we detected hemorheological abnormalities in individuals with SCT. These abnormalities included higher red blood cell rigidity and higher blood viscosity in the SCT carriers compared with the non-carriers, particularly during the late recovery period (24 and 48 h after exercise). Therefore, we can suggest that the risks for microvascular complications in SCT carriers in response to exercise could be dependent on alterations in blood rheology and vascular adhesion processes.

Effects of strenuous exercise on blood coagulation activity in sickle cell trait carriers.

We compared routine coagulation markers in six sickle cell trait carriers ((SCT, or AS hemoglobinopathy)--the heterozygous form of sickle cell anemia) and six subjects with normal hemoglobin before and after a prolonged and intense exercise. Blood was sampled at rest and at the end of the entire exercise test to measure coagulation markers (prothrombin time, activated partial thromboplastin time, plasma fibrinogen and antithrombin III activity), hematocrit (Hct) and yield stress (tau(y)). Results obtained at the end of exercise were corrected by the percent change in plasma volume. Blood coagulation markers, Hct and tau(y) were not different between the two groups at rest. Exercise did not change prothrombin time, antithrombin III activity and plasma fibrinogen, decreased activated partial thromboplastin time and increased Hct and tau(y) in the two groups. These parameters were not significantly different between the two groups at the end of exercise, except for plasma fibrinogen which was slightly higher in SCT carriers but in the normal range values. The results have been discussed in relation with some cases of exercise-related sudden death in SCT carriers, reported in several studies. Therefore our results show that the increased risk for clinical complications in certain SCT carriers during exercise seems to be unrelated to higher blood coagulation activity.