This paper aims at analyzing the state-of-the-art techniques to measure electrical impedance (and, consequently, electrical resistivity) of mortar/concrete elements. Despite the validity of the concept being widely proven in the literature, a clear standard for this measurement is still missing. Different methods are described and discussed, highlighting pros and cons with respect to their performance, reliability, and degree of maturity. Both monitoring and inspection approaches are possible by using electrical resistivity measurements; since electrical resistivity is an important indicator of the health status of mortar/concrete, as it changes whenever phenomena modifying the conductivity of mortar/concrete (e.g., degradation or attacks by external agents) occur, this review aims to serve as a guide for those interested in this type of measurements.

Nowadays, the use of wearable devices is spreading in different fields of application, such as healthcare, digital health, and sports monitoring. In sport applications, the present trend is to continuously monitor the athletes’ physiological parameters during training or competitions to maximize performance and support coaches. This paper aims to evaluate the performances in heart rate assessment, in terms of accuracy and precision, of both wrist-worn and chest-strap commercial devices used during swimming activity, considering a test population of 10 expert swimmers. Three devices were employed: Polar H10 cardiac belt, Polar Vantage V2, and Garmin Venu Sq smartwatches. The former was used as a reference device to validate the data measured by the two smartwatches. Tests were performed both in dry and wet conditions, considering walking/running on a treadmill and different swimming styles in water, respectively. The measurement accuracy and precision were evaluated through standard methods, i.e., Bland–Altman plot, analysis of deviations, and Pearson’s correlation coefficient. Results show that both precision and accuracy worsen during swimming activity (with an absolute increase of the measurement deviation in the range of 13–56 bpm for mean value and 49–52 bpm for standard deviation), proving how water and arms movement act as relevant interference inputs. Moreover, it was found that wearable performance decreases when activity intensity increases, highlighting the need for specific research for wearable applications in water, with a particular focus on swimming-related sports activities.

To date, wearable devices are increasingly widespread among different kinds of users (e.g. sport people, patients, but also young and adult people in general) to monitor physiological parameters (e.g. heart rate, skin temperature, steps and energy expenditure), depicting the subject's physical activity pattern during different activities. Nonetheless, an insufficient attention is paid to the measurement characteristics and the accuracy of these devices, which, on the contrary, are of utmost importance, especially if the wearable is used for health or fitness purposes since uncertainty affects the result itself. The aim of this work is to analyze the performances of wearable devices and the measurement procedure used to validate them with respect to gold standard instruments, such as electrocardiogram for cardiac parameters or calorimetry for energy expenditure. What clearly appears is the lack of a standard test protocol in the validation process, as well as a large variability in the expression of metrological characteristics of this class of measurement device (e.g. referring to accuracy, some authors use bias, others absolute error). Therefore, in the field of wearable devices research it would be fundamental to identify some common measurement parameters and to devise a kind of guidelines, in order to obtain repeatable and inter-comparable data that can be reliably compared.