No abstract

Internet of things (IoT) devices heavily rely on wireless connectivity. There are intrinsic overlooked limitations such as reach, availability, security and safety vulnerabilities closely associated with wireless solutions. Wired connectivity is the alternative to tackle those issues, and optical fibers directly connecting IoT devices could provide them unique features such as huge bandwidth, long reach, signal integrity and high security grade for the transmitted information. Nevertheless, it can be prohibitive for IoT devices which are power hungry and have costly electrical-to-optical conversions. In this paper, first, a niche is identified for IoT over fiber (IoToF) based on fully passive optical solutions for long reach upstream of low data rate optical connectivity over dark fibers. Then, we proposed, implemented and characterized a prototype physical connectivity (PHY) based on fiber Bragg grating (FBG) low-cost acousto-optic modulation at IoT devices and respective optical edge-filtering as wavelength discriminator at the receiver. Finally, we performed an experimental demonstration of upstream data communication based on simple M-ary frequency-shift keying (FSK), with baud rate of 300 bps transmitted over 30 km range. In terms of data rate and reach for niche applications, IoToF can outperform traditional wireless technologies, such as Sigfox or LoRa. IoToF will enable monitoring urban areas with scarce and polluted spectrum, industrial areas requiring intrinsic safety, and upstreaming data from IoT devices in remote locations with unfavorable wireless propagation but with dark fibers available.

Studying fatigue is challenging because it is influenced by physiological, psychological, and sociological states. Fatigue can be assessed objectively or subjectively, but the literature has difficulty understanding how an analytical test relates to a response via a questionnaire. Thus, the purpose of this study was to evaluate the relationships between objective fatigue variables (Squat Jump (SJ) and Countermovement Jump (CMJ)) measured on day-2 to the game and subjective fatigue (Rating Perceived Exertion (RPE) measured on day-3 to the game and Hooper Index (HI) measured on day-2). The sample comprised 32 professional football players from the First Portuguese League aged 25.86 ± 3.15 years. The Spearman correlations and regression analyses were used to study the relationships between the variables. The results showed statistically significant (p < 0.05) but small correlations (0.113–0.172) between several objective metrics and the subjective metrics evaluated. In addition, we found two weak models with statistical significance (p < 0.05) between the dependent objective variables (contact time, height, and elasticity index) and the HI (R2 = 3.7%) and RPE (R2 = 1.6%). Also, nine statistically significant (p < 0.05) but weak models were observed between the subjective dependent variables (HI and RPE) and contact time (R2 = 1.8–2.7%), flight time (R2 = 1.1–1.9%), height (R2 = 1.2–2.3%), power (R2 = 1.4%), pace (R2 = 1.2–2.1%), and elasticity index (R2 = 1.6%). In conclusion, objective and subjective fatigue-monitoring tests in professional soccer do not measure identical but rather complementary aspects of fatigue, and therefore, both need to be considered to gain a holistic perspective.

Sports participation is one of the most popular forms of physical activity among youngsters. This study aimed to examine the changes in the estimated body composition, strength, and flexibility of adolescent boys after 12 months of soccer training compared with those of age-matched controls with non-sports participation. We assessed 137 boys (62 soccer players and 75 controls) at baseline (TM1) and 12 months later (TM2). The differences in estimated body composition, strength, and flexibility were investigated using a repeated measure analysis of variance. The analysis revealed a significant main effect of soccer training on fat mass (F = 73.503, p ≤ 0.01, η2 = 0.59) and fat-free mass (F = 39.123, p ≤ 0.01, η2 = 0.48). Over time, the soccer group decreased their fat mass and increased their fat-free mass, while the opposite results were observed for the controls. Among physical fitness tests, a substantial effect of soccer training was evidenced for the sit-up performance (F = 16.224, p ≤ 0.01, η2 = 0.32). Regarding the time factor, significant effects were noted for height and handgrip strength. No significant differences were detected for flexibility. Overall, the benefits of soccer training were exhibited by the larger improvements in fat mass, fat-free mass, sit-ups, and handgrip strength performance, underlining the important role of soccer participation during adolescence.