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Background and Purpose: Accurate measurement of cardiorespiratory fitness (VO2max) is very important in sport sciences. The direct measurement of VO2max using a respiratory gas analysis device cannot be very operational and comprehensive due to the high cost, time-consuming, need for an expert, and the possibility of some cardio-respiratory risks during the performance of an increasing exercise test. Estimating VO2max using equations based on heart rate index (HRindex) is one of the most widely used methods in sports fields, which can estimate an individual's VO2max without needing breath gas analysis. However, this requires accurate measurements of resting and maximal heart rates with the least error. In the present study we aimed to evaluate the validity of VO2max equations based on heart rate index in adolescent boys. Material and Methods: One hundred and fifty-seven healthy adolescent boys (Mean±SD; age, 14.92±1.35 years; BMI, 21.39 ± 4.50 kg/m2 and VO2max: 41.80 ± 6.67 ml/kg/min) from middle and high schools in Hamadan city voluntarily participated in this cross-sectional study. Initially, the resting heart rate and body composition of the subjects were measured. The subjects' VO2max and maximal heart rate were measured by the respiratory gas analysis method by using modified Bruce incremental exercise test (criterion method). Moreover, the subjects' VO2max were estimated using HRindex-based equations. Pearson correlation, pair sample t-test, and Bland and Altman agreement were used to evaluate the validity of heart rate index based on VO2max equations. Results: A significant correlation was observed between the criterion method of VO2max and HRindex- based VO2max equations (R=0.328, p<0.05). A significant difference (p<0.05) was observed between measured and HRindex-based VO2max equations (Mean difference = 3.34 - 5.45 ml/kg/min). In healthy adolescent boys, both estimation equations led to underestimation of VO2max by 11.36 ± 17.93% and 5.84 ± 16.39%, respectively. In addition, the Bland and Altman plot showed low agreement between measured and HRindex-based VO2max equations. Conclusions: HRindex-based VO2max equations do not have sufficient validity to be used in healthy adolescent boys and they led to the underestimation of VO2max. Therefore, it is recommended to employ HRindex-based VO2max equations for healthy adolescent boys. [ABSTRACT FROM AUTHOR]

Phase Change Memory (PCM) is an emerging memory technology that has the capability to address the growing demand for memory capacity and bridge the gap between the main memory and the secondary storage. As a resistive memory, PCM is able to store data based on its resistance values. The wide resistance range of PCM makes it possible to store even multiple bits per cell (MLC) rather than a single bit per cell (SLC). Unfortunately, PCM cells suffer from short lifetime. That means PCM cells could tolerate a limited number of write operations, and afterward they tend to permanently stick at a constant value. Limited lifetime is an issue related to PCM memory; hence, in recent years, many studies have been conducted to prolong PCM lifetime. These schemes have vast variety and are applied at different architectural levels. In this survey, we review the important works of such schemes to give insights to those starting to research on non-volatile memories (NVMs). These schemes are not limited to PCM and are applicable on other NVM technologies due to the similarities between them and the generality of lifetime-prolonging schemes. [ABSTRACT FROM AUTHOR]

Background and aims: Measurement of the cardiorespiratory fitness (CRF) (VO2peak) is not possible in every clinical and exercise setting due to complexity, cost, and time required. Submaximal field exercise test in an alternative method. Among exercise tests, the 6-minute walk test (6MWT) measures the maximal distance which a person can walk in 6 minutes. The purpose of the present study was to develop and cross-validate the VO2peak prediction equation based on the 6MWT in boys. Methods: VO2peak was measured by Bruce treadmill protocol with gas analysis in 157 healthy boys (13-17 years old). The 6MWT and anthropometric variables were measured according to standard methods. Data were analyzed using Kolmogorov-Smirnov test, Pearson correlation, and multiple regression analysis. Results: It was found that VO2peak of the boys had a significant correlation with 6MWT and anthropometric variables (r=0.318-0.853). VO2peak of the adolescent boys could be predicted by the distance walked in 6 minutes and body mass index (BMI) (R2 = 0.825, SEE = 2.81 mL/kg/min, P < 0.001). When the new VO2peak prediction equation was applied for the subjects of this study, predicted VO2peak had a high correlation with measured VO2peak (r = 0.908, P < 0.001). Conclusion: The 6MWT and proposed native VO2peak prediction equation could be used as a simple and safe tool for measurement of the CRF in the boys. It seems that physicians, exercise and fitness coaches, and physiotherapists could be able to evaluate the effect of medical and exercise prescriptions on the CRF of the boys via performing the 6MWT. This claim needs future studies. [ABSTRACT FROM AUTHOR]