Over the last few years, portable Near-Infrared Spectroscopy (NIRS) technology has been suggested for determining metabolic/ventilator thresholds. This systematic review and meta-analysis aimed to assess the reliability of a portable muscle oxygenation monitor for determining thresholds during exercise testing. The proposed PICO question was: Is the exercise intensity of muscle oxygenation thresholds, using portable NIRS, reliable compared with lactate and ventilatory thresholds for exercise intensity determined in athletes? A search of Pubmed, Scopus and Web of Science was undertaken and the review was conducted following PRISMA guidelines. Fifteen articles were included. The domains which presented the highest biases were confounders (93% with moderate or high risk) and participant selection (100% with moderate or high risk). The intra-class correlation coefficient between exercise intensity of the first ventilatory or lactate threshold and the first muscle oxygenation threshold was 0.53 (obtained with data from only 3 studies), whereas the second threshold was 0.80. The present work shows that although a portable muscle oxygenation monitor has moderate to good reliability for determining the second ventilatory and lactate thresholds, further research is necessary to investigate the mathematical methods of detection, the capacity to detect the first threshold, the detection in multiple regions, and the effect of sex, performance level and adipose tissue in determining thresholds.

Heart rate (HR) is the most frequently used variable to monitor athletes’ internal load during training and competition. High-intensity effort and abrupt HR changes during exercise have presented measurement accuracy issues depending on the chosen device. Therefore, this study aimed to compare two chest straps (Garmin HRM-Dual and Coospo H6) and one armband (Coospo HW807) during intermittent exercise under controlled laboratory conditions. Thirty active young men performed an indoor cycling protocol consisting of seven intermittent efforts with a 2 min effort stage followed by a 2 min recovery stage. The results show no difference between the chest straps (Garmin vs. Coospo), with a high level of agreement between the two devices (Bias = −0.2 bpm, LoA_up = +2.5 bpm, LoA_low = −2.9 bpm, ICC = 0.6–1.0). Differences were found between the chest straps and the armband during effort stages (±5 bpm, p < 0.05), with similar bias and LoA values in the Garmin Strap vs. Coospo Armband (Bias = −0.5 bpm, LoA_up = 8.3 bpm, LoA_low = −9.3 bpm) and Coospo Strap vs. Coospo Armband (Bias = −0.4 bpm, LoA_up = 8.3 bpm, LoA_low = −9.0 bpm) comparison. Chest straps (Garmin HRM-Dual and Coospo H6) accurately measure HR during intermittent exercise with abrupt HR changes. However, caution should be taken when using armbands (Coospo HW807) to monitor intermittent and high-intensity effort.

The aim of the present study was to evaluate skin temperature (Tsk) asymmetries, using infrared thermography, in professional padel players before (PRE), after (POST) and 10 min after training (POST10), and their relationship with perceptual variables and training characteristics. Thermal images were taken of 10 players before, after and 10 min after a standardized technical training. After training, Tsk of the dominant side was higher than before training in the anterior forearm (30.8 ± 0.4 °C vs. 29.1 ± 1.2 °C, p < 0.01; ES = 1.9), anterior shoulder (31.6 ± 0.6 °C vs. 30.9 ± 0.6 °C, p < 0.05; ES = 1.0) posterior arm (29.5 ± 1.0 °C vs. 28.3 ± 1.2 °C, p < 0.05; ES = 1.0), and posterior forearm (30.8 ± 0.9 °C vs. 29.3 ± 1.6 °C, p < 0.05; ES = 1.1). Likewise, these differences were significant POST10 in the anterior arm, anterior forearm, anterior shoulder, posterior arm and posterior forearm. Comparing the different moments of measurement (PRE, POST and POST10), the temperature was higher POST10 in all the regions analyzed except for the shoulder, abdominals, and lower back. Also, correlations were found between fatigue variation and temperature variation between limbs (Tsk dominance), and no correlation was found except between age and posterior thigh (|r| = 0.69; p < 0.05), and between the racket mass and anterior knee (|r| = 0.81; p < 0.01). In conclusion, infrared thermography allows monitoring of skin asymmetries between limbs in professional padel players, but these asymmetries were not related to overall fatigue variation, overall pain variation, years of experience and training hours.

This preliminary study aimed to assess skin temperature (Tsk) asymmetries before and after on-court training in elite young tennis players and to find the correlation between these asymmetries and demographic data, racquet characteristics, and pain and fatigue variation. Thermal images of nine tennis players were taken before and after two and a half hours of standardised training. Thermal asymmetries were correlated to age, years of experience, racquet weight, string tension, body mass index (BMI), and variation in fatigue and pain. In contralateral comparison, Tsk was higher on the dominant side in areas such as the anterior (1.1 ± 0.5 °C, p < 0.001, ES = 0.5) and posterior forearm (1.1 ± 1 °C, p < 0.01, ES = 0.5). Concerning pre- and post-comparisons, post-training Tsk values were lower in all regions except in the posterior forearm, posterior shoulder, and posterior leg. Finally, significant correlations were found between thermal asymmetry and weight of the racquet, body mass index, fatigue and pain variation. Monitoring tennis players’ Tsk with infrared thermography (IRT) gives coaches vital information to evaluate contralateral asymmetries and technical pattern activations during training sessions.

The physical-conditional aspects of the game are a significant research area, focusing on game demands, strength, and kinematic features. This study aimed to synthesise the current state of the art regarding beach volleyball's physical demands. This systematic literature review was conducted in March 2024, following the PRISMA criteria and methodological quality scales. The databases consulted were SPORTDiscus, Web of Science, and Scopus. Data concerning study design, sample size, gender, age-group category, player role, and performance level were considered. The risk of bias was assessed using the 12-item MINORS methodological index scale. A total of 19 studies were included, considering male (6), female (9) or both genders (4) as a sample. According to the athletes’ level of performance, 25% of the studies assessed players at the developmental or national level, 50% explored the international context, and the remaining 25% were with elite players. Data regarding game demands, mechanical outcomes related to jump and power, kinematic variables concerning distance covered and running speed, and kinetic measurements for acceleration and deceleration actions are displayed. The data provided by the current review allow a precise comparison, addressing specific performance profiles and future research challenges from the lack of knowledge about this topic.

Actualmente, están disponibles en el mercado nuevos modelos de calzado deportivo, como el calzado inestable. Sin embargo, todavía existe una falta de evidencia respecto a los cambios que este tipo de calzado puede producir en la biomecánica de la marcha. Así pues, el objetivo de esta investigación fue analizar los efectos agudos del calzado inestable sobre los impactos de aceleración, así como también sobre la variación de temperatura superficial plantar. Seis deportistas (estudiantes físicamente activos, edad 28±8 años, altura 1.73±0.05 m, masa corporal 68.7±6.7 kg, talla de pie 41±1.6 cm) participaron voluntariamente en el estudio. Las características de la pisada se obtuvieron mediante el test Foot Posture Index. La prueba de marcha se llevó a cabo sobre tapiz rodante (10 minutos a 1.44 m/s) bajo dos condiciones de calzado: zapatillas estables y zapatillas inestables. Se analizaron los impactos de aceleración (en tibia y cabeza), y la temperatura superficial plantar (en antepié, mediopié y retropié) en diferentes momentos de la prueba. Los resultados no mostraron diferencias significativas entre ambos tipos de zapatillas en las variables de acelerometría analizadas en ninguno de los momentos de registro. Sin embargo, sí se encontraron diferencias significativas entre ambos calzados (estable=1.40ºC, inestable=3.10ºC, p=0.004) en la variación de temperatura plantar del mediopié en ΔTPost5 (diferencia entre antes del inicio de la prueba y 5 minutos después de finalizarla). En conclusión, las zapatillas inestables parecen no producir ningún beneficio adicional al calzado tradicional para el deportista durante la marcha. Palabras clave: zapatillas, marcha, biomecánica, acelerometría, termografía. Nowadays, new models of sports footwear are available on the market, such as unstable shoes. However, there is still a lack of evidence regarding the changes that this type of footwear can produce on gait biomechanics. Therefore, the aim of this research was to analyze the acute effects of unstable shoes on acceleration impacts, as well as on plantar surface temperature variation. Six athletes (physically active college students, age 28±8 years, height 1.73±0.05 m, body mass 68.7±6.7 kg, shoe size 41±1.6 cm) voluntarily participated in the study. Gait characteristics were obtained by means of the Foot Posture Index test. The walking test was performed on a treadmill (10 minutes at 1.44 m/s) under two footwear conditions: stable shoes and unstable shoes. Acceleration impacts (tibia and head), and plantar surface temperature (forefoot, midfoot and rearfoot) were analysed at different moments during the test. The results showed no significant differences between the two types of shoes in the accelerometry variables analyzed at any of the recording times. However, significant differences were found between both shoes (stable=1.40ºC, unstable=3.10ºC, p=0.004) in the variation of midfoot plantar temperature at ΔTPost5 (difference between before the start of the test and 5 minutes after the end of the test). In conclusion, unstable shoes do not seem to produce any additional benefit to traditional shoes for the athlete during walking. Keywords: sport shoes, gait, biomechanics, accelerometry, thermography.