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Ground reaction forces (GRF) are a critical element acting on the joints of the lower limbs and the presence of fatigue may potentially modify running biomechanics. This systematic review aimed to assess and synthesize the current evidence on the effects of fatigue on GRF-related variables in long-distance runners. Following the PRISMA 2020 guidelines, four databases were consulted in September 2024 followed by a search of reference lists and expert suggestions. Eligibility criteria included healthy competitive or recreational long-distance runners, performing before and after an exercise-based fatigue-inducing protocol, and assessing GRF-related variables on a treadmill or overground using a force plate (the gold standard for kinetic performance analysis). 14 studies (345 participants, 193 females) were included. The studies investigated 27 different variables (with loading rate, active peak force and peak ankle plantarflexor). Most studies exhibited no effect of fatigue on GRF-related variables and there was considerable heterogeneity between studies (e.g., populations, interventions and testing). Risk of bias in the studies was moderate to high and certainty of evidence was judged as very low. Based on available data, there is no significant effect of fatigue on GRF during running, being uncertain to what extent they affect performance overall. Future research should focus on the ecological validity of the study, replicating the experiments during outdoor running.

(1) Background: Among the myriad of injuries affecting football players, hamstring strains have emerged as a persistent and debilitating concern, underscoring the need for novel approaches to reduce strain rates. The current study aims to analyze the impact of improved running technique on reducing hamstring injuries in football players. (2) Methods: Twenty-two male < 19 years old footballers were randomly assigned to an intervention and a control groups (n = 14 vs. 8), the former performing a running technique program of six weeks. Three-dimensional kinematics, using a markerless motion capture system, assessed linear and angular variables during touchdown and toe-off instants to evaluate pre- and post-intervention. Independent and repeated measure t-tests and effect size calculations were employed. (3) Results: A decrease in hip flexion and thorax external rotation during the touchdown (−2.39° and −2.02°, p ≤ 0.05) and a decrease in pelvic external rotation and an increase in stride length (−3.22° and 0.06 m, p ≤ 0.05) during toe-off for the players that engaged in the running technique development was observed. (4) Conclusions: These findings emphasize the significant impact of improved running technique and sprint mechanics, suggesting a potential decrease in the risk of hamstring injuries during high-speed running in football players.

Runners achieve forward locomotion through diverse techniques. However, understanding the behavior of the involved kinematical variables remains incomplete, particularly when running overground and along an intensity spectrum. We aimed to characterize the biomechanical and physiological adaptations while running at low, moderate, heavy and severe intensities. Ten middle- and long-distance runners completed an incremental intermittent protocol of 800 m steps until exhaustion (1 km·h−1 velocity increments and 30 s intervals) on an outdoor track field. Biomechanical data were captured using two high-resolution video cameras, and linear and angular kinematic variables were analyzed. With the intensity rise, a decrease in stride, step and contact times ([0.70–0.65], [0.35–0.33] and [0.42–0.37] s) and an increase in stride length and frequency and flight time ([3.13–3.52] m, [1.43–1.52] Hz and [0.28–0.29] s; p < 0.05) were observed, together with an increase in oxygen uptake and blood lactate concentrations ([54.7–67.6] mL∙kg−1∙min−1 and [3.1–10.2] mmol∙L−1). A more flexed hip at initial contact and toe-off (152.02–149.36] and [165.70–163.64]) and knee at initial contact ([162.64–159.57]; p < 0.05) were also observed. A consistent gait pattern along each protocol step was exhibited, with minor changes without practical significance. Runners are constantly adapting their gait pattern, reflected in both biomechanical and physiological responses, both of which should be considered for better characterization.

Background/Objectives: Swimming is a popular and cost-effective way to prevent sedentary behavior and improve physical conditioning and health during early adolescence. However, information on its impact and benefits on daily life activities is lacking. This systematic review aims to summarize the chronic effects of swimming on physical conditioning and physical health outcomes in early adolescents. Methods: The PRISMA 2020 guidelines were followed and PubMed, Scopus, Web of Science, and International Symposium of Biomechanics and Medicine in Swimming proceedings databases were searched. Eligibility criteria were defined on the PICOS framework (healthy adolescents in early puberty, swimming programmes or training, passive or active control groups, general effects on physical conditioning or health, longitudinal) and risk of bias was assessed using RoBANS 2. Results: From 2365 records, 20 non-randomized studies met the defined criteria. High heterogeneity in sample size and intervention was observed. While studies related to physical conditioning (n = 5) focused on physiological variables and muscular function, the evidence regarding physical health outcomes (n = 15) explored bone accrual, haemodynamics, body composition, musculoskeletal system, and lung growth. High overall risk of bias (70%) was observed due to strict criteria. Conclusions: Swimming exercise seems to improve cardiorespiratory fitness, cardiac output, haemodynamics, heart growth, motor performance, and body composition of early adolescents. Despite clear evidence that exists on these chronic effects, research on bone health, postural deficit, motor skills, and sleep quality is still missing.

The effects of occlusal splints on sport performance have already been studied, although their biomechanical impacts are often overlooked. We investigated the kinematical changes during running until exhaustion at severe intensity while wearing a mandibular advancement occlusal splint. Twelve trained runners completed (i) an incremental protocol on a track to determine their velocity corresponding to maximal oxygen uptake and (ii) two trials of square wave transition exercises at their velocity corresponding to maximal oxygen until exhaustion, wearing two occlusal splints (without and with mandibular advancement). Running kinematics were compared within laps performed during the square wave transition exercises and between splint conditions. The mandibular advancement occlusal splint increased the running distance covered (~1663 ± 402 vs. 1540 ± 397 m, p = 0.03), along with a noticeable lap effect in decreasing stride frequency (p = 0.04) and increasing stride length (p = 0.03) and duty factor (p < 0.001). No spatiotemporal differences were observed between splints, except for improved balance foot contact times in the mandibular advancement condition. An increased knee flexion angle at initial contact (p = 0.017) was noted along laps in the non-advancement condition, despite the fact that no differences between splints were found. Running patterns mainly shifted within laps rather than between conditions, indicating that a mandibular advancement occlusal splint had a trivial kinematical effect.

An inertial measurement system, using a combination of accelerometers, gyroscopes and magnetometers, is of great interest to capture tennis movements. We have assessed the key biomechanical moments of the serve phases and events, as well as the kinematic metrics during the serve, to analyze their influence on serve speed. Eighteen male competitive tennis players, equipped with the inertial measurement units, performed a prolonged serve game consisting of 12 simulated points. Participants were divided into groups A and B in accordance with their positioning above or below the sample average serve speed. Group A (compared with their counterparts) presented with lower back hip adduction and knee flexion, and a higher leftward thoracic tilt during the impact event (−14.9 ± 6.9 vs. 13.8 ± 6.4, 2.8 ± 5.9 vs. 14.3 ± 13.0 and −28.9 ± 6.3 vs. 28.0 ± 7.3°). In addition, group A exhibited higher maximal angular velocities in the wrist and thorax, as well as a lower maximal angular velocity in the back hip than group B (427.0 ± 99.8 vs. 205.4 ± 9.7, 162.4 ± 81.7 vs. 193.5 ± 43.8, 205.4 ± 9.7 vs. 308.3 ± 111.7, 193.5 ± 43.8 vs. 81.1 ± 49.7°/s). The relevant biomechanical differences during the serve were identified, highlighting the changes in joint angles and angular velocities between the groups, providing meaningful information for coaches and players to improve their serve proficiency.

Since swimming performance depends on both physical conditioning and technical proficiency, training zones should be built based on physiology and biomechanics inputs to dispose of structured and effective training programs. This paper presents a zone-based swimming training, supported by the oxygen uptake (V˙O2) kinetics at low, moderate, heavy, severe and extreme intensities concurrently with lactate and heart rate values. Since technique is vital for efficiently moving through the water, upper limbs frequency and length should also be targeted during the workouts. The index of coordination was also added to our proposal since upper limbs synchronization is a key technical factor. To better establish and characterize a wide range of swimming intensities, the training methods and corresponding contents that better fit each training zone will be suggested. It will be shown that when under/at the anaerobic threshold (at low-to-moderate intensities), swimmers are at homeostasis and can maintain stable internal and external load indicators. However, above that boundary (at heavy and severe intensities), the physiological stable state is no longer observed and the anaerobic metabolism starts contributing significantly, with a technical degradation being more evident when performing near/at the V˙O2max intensity. Then, when performing above aerobic power, on typical anaerobic intensities, V˙O2 kinetics presents a very evident fast rise, ending abruptly due to exhaustion caused by muscle acidosis. This overall knowledge allows advancing toward more objective training programs and highlights the importance of systematic training control and swimmers' evaluation and advice.

A cross-sectional study was conducted to biomechanically characterize Isabel’s workout (30 snatch repetitions with 61 kg fixed weight), focusing on eventual changes in knee, hip and shoulder angles. A three-dimensional markerless motion capture system was used to collect data from 11 highly trained male crossfitters along the Isabel workout performed at maximal effort. The routine was analyzed globally and in initial, middle and final phases (10, 20 and 30 repetitions, respectively). Lift total time increased (1.51 ± 0.18 vs. 1.97 ± 0.20 s) and maximal lift velocity (2.64 ± 0.12 vs. 2.32 ± 0.13 m/s) and maximal lift power (15.58 ± 2.34 vs. 13.80 ± 2.49 W/kg) decreased from the initial to final phases, while the time from lift until the bar crossed the hip and shoulder (34.20 ± 4.00 vs. 27.50 ± 5.10 and 39.70 ± 16.80 vs. 30.90 ± 13.90%) decreased along the Isabel workout. In addition, a decrease in hip flexion was observed during the last two phases when the bar crosses the knee (62.62 ± 24.80 vs. 53.60 ± 19.99°). Data evidence a decrease in the power profile and a change in hip flexion throughout the Isabel workout, without compromising the other joints.

We aimed to conduct a biophysical comparison of angular (Biorower) and linear (Concept2) rowing ergometers across a wide spectrum of exercise intensities. Sixteen (eleven male) skilled rowers, aged 29.8 ± 8.6 and 23.6 ± 1.5 years, with international competitive experience, performed 7 × 3 min bouts with 30 W increments and 60 s intervals, plus 1 min of all-out rowing on both machines with 48 h in between. The ventilatory and kinematical variables were measured breath-by-breath using a telemetric portable gas analyzer and determined using a full-body markerless system, respectively. Similar values of oxygen uptake were observed between ergometers across all intensity domains (e.g., 60.36 ± 8.40 vs. 58.14 ± 7.55 mL/min/kg for the Biorower and Concept2 at severe intensity). The rowing rate was higher on the Biorower vs. Concept2 at heavy and severe intensities (27.88 ± 3.22 vs. 25.69 ± 1.99 and 30.63 ± 3.18 vs. 28.94 ± 2.29). Other differences in kinematics were observed across all intensity domains, particularly in the thorax angle at the finish (e.g., 19.44 ± 4.49 vs. 27.51 ± 7.59° for the Biorower compared to Concep2 at heavy intensity), likely due to closer alignment of the Biorower with an on-water rowing technique. The overall perceived effort was lower on the Biorower when compared to the Concept2 (14.38 ± 1.76 vs. 15.88 ± 1.88). Rowers presented similar cardiorespiratory function on both rowing ergometers, while important biomechanical differences were observed, possibly due to the Biorower’s closer alignment with an on-water rowing technique.

We investigated the acute biophysical responses of changing the mandibular position during a rowing incremental protocol. A World-class 37-year-old male rower performed two 7 × 3 min ergometer rowing trials, once with no intraoral splint (control) and the other with a mandibular forward repositioning splint (splint condition). Ventilatory, kinematics and body electromyography were evaluated and compared between trials (paired samples t-test, p ≤ 0.05). Under the splint condition, oxygen uptake was lower, particularly at higher exercise intensities (67.3 ± 2.3 vs. 70.9 ± 1.5 mL·kg−1·min−1), and ventilation increased during specific rowing protocol steps (1st–4th and 6th). Wearing the splint condition led to changes in rowing technique, including a slower rowing frequency ([18–30] vs. [19–32] cycles·min−1) and a longer propulsive movement ([1.58–1.52] vs. [1.56–1.50] m) than the control condition. The splint condition also had a faster propulsive phase and a prolonged recovery period than the control condition. The splint reduced peak and mean upper body muscle activation, contrasting with an increase in lower body muscle activity, and generated an energetic benefit by reducing exercise cost and increasing rowing economy compared to the control condition. Changing the mandibular position benefited a World-class rower, supporting the potential of wearing an intraoral splint in high-level sports, particularly in rowing.

Despite its limitations, 2D kinematical analysis remains a simple and valid alternative for swimming analysis. This analysis is limited by the length of the field of view, and the reconstruction errors are proportional to the calibrated area. A possible solution for these problems is the usage of moving cameras that allow for tracking an object across a larger area without the concerns of the calibration area. The purpose of this study was to verify the viability of the utilization of moving cameras for underwater 2D kinematical analysis. Two calibration processes were evaluated: (i) obtaining the extrinsic parameters for every frame based on pool markers (M1) and; (ii) constraining the degrees of freedom of the camera’s movements and tracking translation based on the principal point (M2). M1 obtained better accuracy in reconstructing the coordinates of static markers (mean error: 12.1 against 14.2 mm from a static camera) and in the estimation of the rod length (−2.6 vs. 12.6 mm). M2 obtained better accuracy when evaluating the distance between the points (−0.3 mm) than that for position estimation (58.6 mm). The results indicate that moving cameras are a viable alternative for 2D underwater kinematic analysis, but M2 had limitations about real position extraction.

The speedometer is widely used to evaluate swimming velocity but has some constraints. With the constant development of inertial units (IMUs), it is expected that they will become a good alternative to the speedometer. This study aimed to compare the data retrieved by an IMU and a speedometer when breaststroke is performed at maximum speed. Sixteen swimmers, nine males and seven females (20.3 ± 3.3 vs. 18.7 ± 1.1 years old, 65.8 ± 11.2 vs. 57.7 ± 9.1 kg of body mass and 1.75 ± 0.07 vs. 1.61 ± 0.10 m of height, respectively), performed 4 × 25 m of breaststroke sprint. They were equipped with an IMU fixed to the sacrum and with the line of an electromechanical speedometer (acquisition frequency of 50 Hz) fixed at the central point in the lumbar region. Statistical parametric mapping was used to compare the velocity curves, IBM SPSS was used for descriptive statistics and Bland–Altman plots were used for agreement of measurements. The results show that the IMU and speedometer do not show similar patterns, and the velocity values measured by the IMU are lower (p < 0.001). Bland–Altman plots presented a larger bias in terms of coefficient of variation and intracycle velocity variation. It can be concluded that IMUs and speedometers are not substitutes for each other as methods for evaluating intracycle velocity variations.

Explainable artificial intelligence (XAI) models with Shapley additive explanation (SHAP) values allows multidimensional representation of movement performance interpreted on both global and local levels in terms understandable to human intuition. We aimed to evaluate the swimming performance (World Aquatics points) predictability of a combination of demographic, training, anthropometric, and biomechanical variables (inputs) through XAI. Forty-seven swimmers (16 males), after completing a training questionnaire (background and duration) and anthropometric assessment, performed, in a randomised order, a 25 m front crawl and three countermovement jumps, at maximal intensity. The predicted World Aquatics points (516 ± 159; mean ± SD) were highly correlated (r2 = 0.93) with the 529 ± 158 actual values. The duration of swimming training was the most important variable (95_SHAP), followed by the countermovement jump impulse (37_SHAP), both with a positive effect on performance. In contrast, a higher percentage of fat mass (21_SHAP) corresponded to lower World Aquatics points. Impulse, when interpreted together with dryland training duration and stroke rate, shows the positive effects of upper and lower limb power on swimming performance. Height should be interpreted together with arm span when exploring positive effects of anthropometric traits on swimming performance. The XAI modelling highlights the usefulness of specific training, technical and physical testing, and anthropometric factors for monitoring swimmers.

Physical activity and sports practice plays an important role in maintaining health, well-being, and quality of life. As related concepts, those are not well studied in persons with disabilities, particularly with intellectual disability or Down syndrome. This study aimed to assess the daily life physical activity levels of competitive persons with Down syndrome and to compare those with active and untrained individuals with the same condition. Twenty participants were allocated to international competitive (N=8; 25.8±7.4 years), recreational (N=6; 22.0±4.3 years) and untrained (N=6; 24.0±7.4 years) groups. The daily physical activity was assessed with a CE Mark class I electronic medical device (WalkinSense®), designed to monitor dynamics of human lower limbs’. Time spending in sports practice was not accounted for this analysis. Differences were found between the competitive and the recreational groups in the number of training hours per week and walking distance. Similarly, the competitive group showed differences with the two other groups in weight, body mass index, training hours per week, steps/day and walking distance. Our findings suggest that individuals with Down syndrome engaged in competitive training are more active persons behind their sport comparing to their non-competitive peers, but remain far from the 10 000 steps/day that is the recommended guideline for healthier adults without any disability.

The current study aimed to evidence the strengths and weaknesses of two indirect methods for assessing the anaerobic alactic contribution to a specific CrossFit® workout. Thirty experienced crossfitters performed the Fran workout at maximal intensity, and ventilatory data were collected during the recovery period using a telemetric portable gas analyser to assess the oxygen uptake (VO2) of the off-kinetics fast component (Anarecovery). The kinetics of maximal phosphocreatine splitting (AnaPCr) were determined based on the literature. No differences between the two methods were observed (31.4 ± 4.0 vs. 30.4 ± 4.1 kJ for Anarecovery and AnaPCr, respectively). Despite the existence of some caveats (e.g., errors derived from a delay at the onset of VO2 recovery and the assumption of given values in the concentration of phosphocreatine per kilogram of wet muscle, respectively) in both methods, the data indicate that they yield similar results and allow for estimations of alactic energy contribution from a short-duration and high intensity CrossFit® routine. The current data contributes to CrossFit® workout evaluations and training strategies, helping researchers to evaluate crossfitters more accurately. The advantage of the two methods used in the current study is that they are non-invasive, which differs greatly from muscle biopsies.

In this study, we quantified relevant biophysical characteristics of two elite rowers across a wide range of intensities. Two

Our purpose was to characterize the oxygen uptake kinetics (VO2), energy systems contributions and total energy expenditure during a CrossFit® benchmark workout performed in the extreme intensity domain. Fourteen highly trained male CrossFitters, aged 28.3 ± 5.4 years, with height 177.8 ± 9.4 cm, body mass 87.9 ± 10.5 kg and 5.6 ± 1.8 years of training experience, performed the Isabel workout at maximal exertion. Cardiorespiratory variables were measured at baseline, during exercise and the recovery period, with blood lactate and glucose concentrations, including the ratings of perceived exertion, measured pre- and post-workout. The Isabel workout was 117 ± 10 s in duration and the VO2 peak was 47.2 ± 4.7 mL·kg−1·min−1, the primary component amplitude was 42.0 ± 6.0 mL·kg−1·min−1, the time delay was 4.3 ± 2.2 s and the time constant was 14.2 ± 6.0 s. The accumulated VO2 (0.6 ± 0.1 vs. 4.8 ± 1.0 L·min−1) value post-workout increased substantially when compared to baseline. Oxidative phosphorylation (40%), glycolytic (45%) and phosphagen (15%) pathways contributed to the 245 ± 25 kJ total energy expenditure. Despite the short ~2 min duration of the Isabel workout, the oxygen-dependent and oxygen-independent metabolism energy contributions to the total metabolic energy release were similar. The CrossFit® Isabel requires maximal effort and the pattern of physiological demands identifies this as a highly intensive and effective workout for developing fitness and conditioning for sports.

Considering the conflicting evidence regarding the potential long-term detrimental effect of swimming during growth on femur quality and fracture risk, our aim was to investigate the effect of eight months of swimming on femur quality. Twenty male eight-week-old Wistar rats were assigned into a swimming (SW; n = 10; 2 h/day, 5 days/week) or active control group (CG; n = 10, housed with running wheel) for eight months. Plasma osteocalcin and C-terminal telopeptide of type I collagen concentrations (ELISA) were assessed at baseline, four, and eight months of protocol. Femur structure (micro-computed tomography), biomechanical properties (three-point bending), and cellular density (histology) were determined after the protocol. SW displayed a lower uncoupling index, suggesting higher bone resorption, lower empty lacunae density, cortical and trabecular femur mass, femur length and cortical thickness, and higher cortical porosity than CG (p < 0.05). Although both biomarkers’ concentrations decreased in both groups throughout the experiment (p < 0.001), there were no significant differences between groups (p > 0.05). No differences were also found regarding biomechanical properties, bone marrow adiposity, and osteocyte and osteoclast densities (p > 0.05). Long-term swimming was associated with unbalanced bone turnover and compromised femur growth, lower femur mass, and deteriorated cortical bone microarchitecture. However, femur trabecular microarchitecture and biomechanical properties were not affected by swimming.

The present study aimed to analyse the associations between force production and 100 m front crawl inter-lap pacing and kinematics. Eleven elite male swimmers performed a 100 m front crawl maximal effort to collect 50 m lap time (T50, s) and velocity (v, m·s−1) for pacing, stroke rate (SR), stroke length (SL) and stroke index (SI) as kinematic variables. A 30 s tethered effort allowed to determine the peak (Fpeak) and mean force (Fmean) as force production variables. The relative change (Δ) between 50 m laps was also calculated for all measures. A paired sample t-test was used to check differences between laps and Pearson correlation coefficients allowed to quantify the associations between force and remaining variables. The T50 increased from the first to the second lap (ΔT50 = 10.61%, p

Background Physical exercise is a source of stress to the human body, triggering different ventilatory responses through different regulatory mechanisms and the aquatic environment imposes several restrictions to the swimmer, particularly regarding the restricted ventilation. Thus, we aimed to assess the acute ventilatory responses and to characterize the adopted breathing patterns when swimming front crawl at increasing intensity domains. Methods Eighteen well-trained swimmers performed 7 × 200 m front crawl (0.05 m∙s−1 velocity increments) and a maximal 100 m (30 s rest intervals). Pulmonary gas exchange and ventilation were continuously measured (breath-by-breath) and capillary blood samples for lactate concentration ([La−]) analysis were collected at rest, during intervals and at the end of the protocol, allowing the identification of the low, moderate, heavy, severe and extreme intensity domains. Results With the swimming velocity rise, respiratory frequency (fR), [La−] and stroke rate (SR) increased ([29.1–49.7] breaths∙min−1, [2.7–11.4] mmol∙L−1, [26.23–40.85] cycles; respectively) and stroke length (SL) decreased ([2.43–2.04] m∙min−1; respectively). Oxygen uptake (VO2), minute ventilation (VE), carbon dioxide production (VCO2) and heart rate (HR) increased until severe ([37.5–53.5] mL∙kg−1∙min−1, [55.8–96.3] L∙min−1, [32.2–51.5] mL∙kg−1∙min−1 and [152–182] bpm; respectively) and stabilized from severe to extreme (53.1 ± 8.4, mL∙kg−1∙min-1, 99.5 ± 19.1 L∙min−1, 49.7 ± 8.3 mL∙kg−1∙min−1 and 186 ± 11 bpm; respectively) while tidal volume (VT) was similar from low to severe ([2.02–2.18] L) and decreased at extreme intensities (2.08 ± 0.56 L). Lastly, the fR/SR ratio increased from low to heavy and decreased from severe to the extreme intensity domains (1.12 ± 0.24, 1.19 ± 0.25, 1.26 ± 0.26, 1.32 ± 0.26 and 1.23 ± 0.26). Conclusions Our findings confirm a different ventilatory response pattern at extreme intensities when compared to the usually evaluated exertions. This novel insight helps to understand and characterize the maximal efforts in swimming and reinforces the importance to include extreme efforts in future swimming evaluations.

The analysis of the external forces of swimming starts has revealed how swimmers propel themselves out of the block, but data should be properly interpreted to fully understand force-generation mechanisms. This study aimed to assess horizontal and vertical forces in the backstroke start based on swimmers’ structural and propulsive actions. Firstly, a simulated structural force was estimated by two transient backstroke-start inter-segmental realistic body positions: a maximally tucked position and an extended one (just before the hands-off and the take-off, respectively). Secondly, 10 competitive backstroke swimmers performed four 15 m maximal backstroke starts with the external forces estimated. Thirdly, the simulated structural force was subtracted from raw horizontal and vertical force data, measured between hands-off and take-off instants, resulting in the propulsive forces. The application of the algorithm has evidenced that backstrokers’ horizontal and vertical simulated-structural-force components contributed to ~40% of total force during start propulsion (~0.2–0.12 s before the take-off), followed by the propulsive horizontal force increment and a progressive vertical component reduction (~0.05 s) with ~20° take-off angle. Based on these findings, researchers and coaches can better guide swimmers as to the proper mechanical strategies to achieve effectiveness in the backstroke start, and to improve direct transfer of resistance training programs.

Low back pain is one of the main causes of motor disabilities and psychological stress, with the painful process encompassing sensory and affective components. Noxious stimuli originate on the periphery; however, the stimuli are recombined in the brain and therefore processed differently due to the emotional environment. To better understand this process, our objective was to develop a mathematical representation of the International Association for the Study of Pain (IASP) model of pain, covering the multidimensional representation of this phenomenon. Data from the Oswestry disability index; the short form of the depression, anxiety, and stress scale; and pain catastrophizing daily questionnaires were collected through online completion, available from 8 June 2022, to 8 April 2023 (1021 cases). Using the information collected, an artificial neural network structure was trained (based on anomaly detection methods) to identify the patterns that emerge from the relationship between the variables. The developed model proved to be robust and able to show the patterns and the relationship between the variables, and it allowed for differentiating the groups with altered patterns in the context of low back pain. The distinct groups all behave according to the main finding that psychological and pain events are directly associated. We conclude that our proposal is effective as it is able to test and confirm the definition of the IASP for the study of pain. Here we show that the fiscal and mental dimensions of pain are directly associated, meaning that mental illness can be an enhancer of pain episodes and functionality.

Abstract Surfing is one additional sport proposed by the Tokyo 2020 Organizing Committee. Surprisingly, substantial efforts to understand surfing energetics are recent, and the impact of a single surfing paddling cycle on fatigue and energy cost is still not clear. Since surfing paddling technique is highly specific, experiments in real practice conditions are necessary to provide deeper insights. Through a biophysical approach, biomechanical and energetics responses of surfing paddling were quantified and compared from 16 competitive male surfers (23.5 ± 10.0 years old, 65.3 ± 11.4 kg and 1.72 ± 0.01 m) during two sets (PRE and POST) of 10 s all-out tethered paddling plus 20 m sprint paddling, interposed by 6 min of endurance paddling. Faster surfers presented lower energy cost during sprint PRE (r2 = 0.30, p = 0.03) and endurance (r2 = 0.35, p = 0.02) relative surfing paddling velocities. Although the energy cost was higher for a lower velocity at maximal paddling velocity POST, the energy cost of surfing paddling increased with absolute velocity according to a power function (R2 = 0.83). Our results suggest that fatigue seems to occur even following a single surfing paddling cycle. Developing a powerful and endurable metabolic base while reducing energy cost during surfing paddling should be seen as key factors in surfing training programs.

Abstract The current study investigated body roll amplitude and timing of its peak in backstroke and compared them with front crawl swimming. Nineteen anatomical landmarks were digitised using 80 swimming trial videos (ten swimmers × two techniques × four intensities) recorded by two above- and four below-water cameras. One upper-limb cycle was analysed for each trial, and shoulder and hip roll, whole-body roll (WBR), and WBR due to the buoyant torque (WBR BT ) were obtained. Main effects of intensity and technique on the amplitude and timing to reach the peak in those variables were assessed by two-way repeated-measures ANOVA. Swimmers decreased their WBR BT amplitude with an increase in the intensity in both techniques (p ≤ 0.005). The same result was observed for the amplitude of WBR, shoulder roll, and hip roll only in front crawl (p ≤ 0.017). Swimmers maintained the timing of peak WBR BT in both techniques, while they shifted the timing of WBR and hip roll peak toward the beginning of the cycle when increasing the intensity in front crawl (p ≤ 0.017). In conclusion, swimmers maintain the amplitude of WBR, shoulder roll, and hip roll in backstroke when the intensity increases, whereas they reduce the amplitude of all rolls in front crawl.

This study aimed to identify the biomechanical features of backstroke to breaststroke transition techniques (open, somersault, bucket, and crossover) in age-group swimmers. Eighteen preadolescent swimmers (12.2 ± 0.4 years old and 3–4 Tanner stages) underwent 4 weeks of systematic contextual interference training, comprising 16 sessions (40 min·session−1). Soon after, experimental testing was conducted where swimmers randomly performed 12 × 15 m maximal turns (composed of 7.5 m turn-in and 7.5 m turn-out of the wall segments), three in each transition technique. Kinematical, kinetic, and hydrodynamic variables were assessed with a dual-media motion capture system (12 land and 11 underwater cameras), triaxial underwater force plates, and inverse dynamics. Variables were grouped in turn-in (approach and rotation) and turn-out (wall contact, gliding, and pull-out) phases, with factor analysis used to select the variables entering on multiple regressions. For the turn-in phase, 86, 77, 89, and 87% of the variance for open, somersault, bucket, and crossover turning techniques, respectively, was accounted by the 7.5 and 2.5 m times, mean stroke length, and rotation time. For the turn-out phase, first gliding distance and time, second gliding depth, turn-out time, and dominating peak_Z push-off force accounted for 93% in open turn, while wall contact time, first gliding distance, breakout distance and time, turn-out time, dominating peak_Y push-off force, and second gliding drag coefficient accounted for 92% in a somersault turn. The foot plant index, push-off velocity, second gliding distance, and turn-out time accounted for 92% in bucket turn while breakout and turn-out time, non-dominating peak_Y and peak_Z push-off force, first and second gliding drag force and second gliding drag coefficient accounted for 90% in crossover turn, respectively. The findings in this study were novel and provided relevant biomechanical contribution, focusing on the key kinematic–temporal determinant during turn-in, rotation, and push-off efficacy, and the kinetic and hydrodynamic during turn-out, which would lead to improved backstroke to breaststroke transition techniques in 11–13 years-old age-group swimmers.

Physical fatigue reduces productivity and quality of work while increasing the risk of injuries and accidents among safety-sensitive professionals. To prevent its adverse effects, researchers are developing automated assessment methods that, despite being highly accurate, require a comprehensive understanding of underlying mechanisms and variables’ contributions to determine their real-life applicability. This work aims to evaluate the performance variations of a previously developed four-level physical fatigue model when alternating its inputs to have a comprehensive view of the impact of each physiological variable on the model’s functioning. Data from heart rate, breathing rate, core temperature and personal characteristics from 24 firefighters during an incremental running protocol were used to develop the physical fatigue model based on an XGBoosted tree classifier. The model was trained 11 times with different input combinations resulting from alternating four groups of features. Performance measures from each case showed that heart rate is the most relevant signal for estimating physical fatigue. Breathing rate and core temperature enhanced the model when combined with heart rate but showed poor performance individually. Overall, this study highlights the advantage of using more than one physiological measure for improving physical fatigue modelling. The findings can contribute to variables and sensor selection in occupational applications and as the foundation for further field research.

Intracycle velocity variation is a swimming relevant research topic, focusing on understanding the interaction between hydrodynamic propulsive and drag forces. We have performed a systematic scoping review to map the main concepts, sources and types of evidence accomplished. Searches were conducted in the PubMed, Scopus and Web of Science databases, as well as the Biomechanics and Medicine in Swimming Symposia Proceedings Book, with manual searches, snowballing citation tracking, and external experts consultation. The eligibility criteria included competitive swimmers’ intracycle velocity variation assessment of any sex, distance, pace, swimming technique and protocol. Studies’ characteristics were summarized and expressed in an evidence gap map, and the risk of bias was judged using RoBANS. A total of 76 studies, corresponding to 68 trials involving 1440 swimmers (55.2 and 34.1% males and females), were included, with only 20 (29.4%) presenting an overall low risk of bias. The front crawl was the most studied swimming technique and intracycle velocity variation was assessed and quantified in several ways, leading to extremely divergent results. Researchers related intracycle velocity variation to coordination, energy cost, fatigue, technical proficiency, velocity, swimming techniques variants and force. Future studies should focus on studying backstroke, breaststroke and butterfly at high intensities, in young, youth and world-class swimmers, as well as in IVV quantification.

Physical fatigue is a serious threat to the health and safety of firefighters. Its effects include decreased cognitive abilities and a heightened risk of accidents. Subjective scales and, recently, on-body sensors have been used to monitor physical fatigue among firefighters and safety-sensitive professionals. Considering the capabilities (e.g., noninvasiveness and continuous monitoring) and limitations (e.g., assessed fatiguing tasks and models validation procedures) of current approaches, this study aimed to develop a physical fatigue prediction model combining cardiorespiratory and thermoregulatory measures and machine learning algorithms within a firefighters’ sample. Sensory data from heart rate, breathing rate and core temperature were recorded from 24 participants during an incremental running protocol. Various supervised machine learning algorithms were examined using 21 features extracted from the physiological variables and participants’ characteristics to estimate four physical fatigue conditions: low, moderate, heavy and severe. Results showed that the XGBoosted Trees algorithm achieved the best outcomes with an average accuracy of 82% and accuracies of 93% and 86% for recognising the low and severe levels. Furthermore, this study evaluated different methods to assess the models’ performance, concluding that the group cross-validation method presents the most practical results. Overall, this study highlights the advantages of using multiple physiological measures for enhancing physical fatigue modelling. It proposes a promising health and safety management tool and lays the foundation for future studies in field conditions.

Jogadores nascidos nos primeiros meses do ano civil tendem a apresentar maior maturação física e psicológica comparativamente com os jogadores nascidos nos últimos meses desse mesmo ano e têm maior probabilidade de serem selecionados pelos seus treinadores. Este fenómeno denomina-se efeito da idade relativa e as suas causas continuam por determinar1. O objetivo deste estudo foi explorar se jovens jogadores de polo aquático nascidos em diferentes semestres do mesmo ano civil, apresentavam diferenças antropométricas e motoras. Vinte e oito jogadores de polo aquático do escalão de infantis da Associação de Natação do Norte de Portugal participaram no estudo. Foram realizadas medições antropométricas (peso, altura, envergadura, percentagem de massa gorda e massa isenta de gordura) e testes de aptidão motora específicos (salto vertical, teste funcional para desempenho de agilidade, teste de nado intermitente e incremental de percursos de 10 m, velocidade de remate e eficácia de remate) e não específicos da modalidade (abdominais, sprint de 5 m, sprint de 20 m, sprint de 30 m, lançamento da bola medicinal, t-teste de agilidade, salto horizontal, toque pedal e teste yo-yo de recuperação intermitente) tendo os resultados sido agrupados por semestres considerando a data de nascimento de cada sujeito. Recorreu-se ao programa IBM® SPSS® Statistics, versão 25 para o Windows e aos testes Shapiro-Wilk e t-student de medidas independentes (p < 0.05) para avaliar a normalidade dos dados e verificar a existência de diferenças entre grupos, respetivamente. Os jogadores nascidos no primeiro semestre revelaram melhores resultados no salto vertical (129.2 ± 6.5 vs. 121.0 ± 8.1 cm) e no sprint de 20 m (3.65 ± 0.20 vs. 3.88 ± 0.28 s) comparativamente com os jogadores nascidos no segundo semestre desse mesmo ano. Apesar de ausência de diferenças estatísticas, os jogadores nascidos no primeiro semestre tenderam a ser mais altos (173.24 ± 5.97 vs. 167.84 ± 6.96 cm), pesados (63.03 ± 9.24 vs. 61.43 ± 9.78 kg), ágeis (3.77 ± 0.57 vs. 4.09 ± 0.54 s), rápidos no nado (6.34 ± 0.66 vs. 6.75 ± 1.12 s), e potentes (4.11 ± 0.39 vs. 3.88 ± 0.46 m) comparativamente com os jogadores nascidos no segundo semestre desse mesmo ano. A ausência de diferenças antropométricas e motoras entre indivíduos relativamente mais velhos e mais novos apontam para a ausência do efeito da idade relativa nesta amostra. O nível de competitividade e o número de praticantes são fatores que potenciam este fenómeno2. Assim, atendendo ao baixo número de praticantes de polo aquático no contexto nacional parece não existir a necessidade de seleção de jogadores numa mesma equipa em contexto competitivo, atenuando as diferenças existentes entre indivíduos mais velhos e mais novos. No entanto, o relativamente reduzido valor de n pode ter influenciado a ausência de diferenças estatisticamente significativas entre grupos.

O polo aquático é um desporto que solicita ambos os sistemas energéticos, razão pela qual o seu desenvolvimento e avaliação são fundamentais. Jogadores com melhor desempenho em testes de aptidão aeróbia conseguirão melhor resistir à fadiga específica do jogo, enquanto níveis elevados de velocidade serão decisivos para se propulsionarem e realizarem de forma veloz os movimentos acíclicos típicos do polo aquático. Este estudo tem como objetivo apresentar e relacionar os testes multietapa e de sprint usados para aferir a potência aeróbia e a velocidade máxima de nado de jogadores de polo aquático. Foram avaliados 66 jogadores masculinos Sub14 (14.0±0.5 anos de idade) da Associação de Natação do Norte de Portugal. Os jogadores realizaram: (i) o teste multietapa, nadando percursos de 10 m na técnica de crol, iniciando a 0.90 m.s-1 e aumentando 0.05 m.s-1, registando-se a distância final e (ii) o teste de sprint, na distância de 10 m, sendo considerado o melhor tempo após três tentativas (cf. Richichi et al., 2000). Foi testada a normalidade dos dados através do teste Shapiro-Wilk e, pelo facto da distribuição não ter sido normal, calculou-se a mediana, o intervalo interquartil (IIQ) e os valores mínimos e máximos de cada variável. Seguidamente, o grau de relação entre as variáveis foi obtido através do coeficiente de correlação de Spearman (r) para um p ≤ 0.05 (SPSS). No teste multietapa registou-se a mediana de 60 m de distância percorrida (IIQ: 63 m) e de 30 (nível 1) a 230 m (nível 4) de valores mínimos e máximos. No teste de velocidade de nado registou-se a mediana de 7.43 s (IIQ: 1.41 s) e de 5.41 a 12.02 s de valores mínimos e máximos. Observou-se uma relação inversa forte entre as variáveis em análise (r = - 0.80; p < 0.001). Os valores de aptidão aeróbia e velocidade demonstraram uma heterogeneidade significativa, a qual pode justificar-se pela curta experiência dos jogadores, sobretudo em situação de avaliação. As diferenças maturacionais próprias deste escalão etário poderão também ajudar a explicar a dispersão observada. O coeficiente de correlação observado entre prestações motoras encontra-se próximo de -1, evidenciando que quanto melhor a prestação aeróbia, menor será o tempo no teste de sprint, pelo que os jogadores com melhor performance aeróbia são também os mais velozes em distâncias curtas. Está descrito na literatura que jogadores de polo aquático com melhor desempenho aeróbio conseguem melhor resistir à fadiga, apresentando um rendimento desportivo superior quer do ponto de vista da condição física quer das habilidades técnicas (Botonis et al., 2015). Uma melhoria na capacidade de sprint será também decisiva para as fases de início e aceleração no início de cada período de jogo, assim como para cada jogador se conseguir deslocar de forma adequada, por exemplo, num contra-ataque.

Propulsive swimming mechanics mainly depends on upper limbs' actions that perform three-dimensional movements in each cycle. Considering that hydrodynamic drag is proportional to the square of velocity, technical execution of segmental displacement at maximal exertions should be effective to ensure high and stable propulsive forces per cycle. Nevertheless, human movement is characterized by constraints that imply variability of motor solutions to optimise kinematic patterns and performance (Newell, 1986). The aim of the study is to characterize upper limbs phases when swimming front crawl at maximal velocity. Thirteen high-level swimmers participated in the study (16.2 ± 0.7 years of age and 171.6 ± 6 cm of height) that took place in a 25 m indoor pool after the main competition of the macrocycle. After a standardized warm-up, swimmers performed a 25 m front crawl at maximal intensity and were recorded in the sagittal plane for 2D kinematical analyses using a double camera set-up (Go Pro 6, 120 Hz) fixed laterally and pushed on a chariot. Upper limbs cycles were divided by counting frames using Blender software, and phases (entry, downsweep, insweep, upsweep, and recovery) were identified. The first seven cycles of each swimmer were analysed, and the relative duration of each phase was obtained as a percentage of the cycle duration. A repeated-measures ANOVA was used to verify differences between cycles, and ICC allowed investigating the relationship between them. The significance level was set at 5%. Figure 1 presents the relative duration of front crawl upper limbs phases (entry, downsweep, insweep, upsweep, and recovery = 18, 12, 20, 23, and 26 % respectively), being possible to observe that downsweep was the shortest even though non-propulsive phases prevailed in relation to the propulsive ones. Table 1 presents the mean values ± SD of the relative duration of seven successive upper limbs cycles. Although swimmers have presented variable relative duration of front crawl upper limbs phases, no differences were reported between cycles. Complementarily, ICC demonstrated high consistency in intraindividual performance (entry, downsweep, insweep, upsweep and recovery = 0.97, 0.90, 0.97, 0.93. 0.90, respectively). Despite the well-known decrease of non-propulsive phases at sprint pace due to the fastest hand velocity/acceleration (McCabe et al., 2011), a predominance was still observed. These results were expected since a higher increase in the relative duration of the propulsive phases could reduce the efficiency, and consequently, could be a technical mistake if its increase was not mandatory for the swimmers' high velocity. In becoming skilled, the neuromuscular system ensures that movement is performed consistently well while, at the same time, develops the ability to adapt to changing constraints. In the present study, we highlighted this statement, as a slight variability is observed between cycles. However, ANOVA and ICC showed a great consistency during the swimming, supporting that the relative duration of upper limbs phases was maintained, probably due to the swimmers' high level in response to the swimming constraints.

O ensino da Natação tem-se caracterizado pelo ensino quase exclusivo da natação pura desportiva (NPD), nela incluindo a fase inicial de adaptação ao meio aquático. Contudo, no meio académico, nos últimos anos, tem-se discutido a potencial vantagem de o ensino ser multidisciplinar, abrangendo outras modalidades aquáticas como o polo aquático (PA), a natação artística (NA) e os saltos para a água, por exemplo (Canossa et al., 2007). Preconiza-se que este modelo de ensino aumentará a satisfação com a prática, a motivação e a competência aquática dos praticantes, nomeadamente pela maior diversidade de movimentos e ações a aprender, mas tais convicções não foram ainda validadas. O presente estudo teve como objetivo determinar o efeito de um programa aquático multidisciplinar na motivação e na competência aquática de sujeitos adultos. Participaram no estudo 9 sujeitos, 7 do sexo masculino e 2 do sexo feminino (41.43±13.25 anos). Um dos participantes era estudante do ensino superior e os restantes tinham profissões de quadro médio ou superior. O protocolo experimental consistiu em 20 sessões de ensino multidisciplinar, compostas por conteúdos da NPD (20 min), do PA (10 min) e da NA (10 min). Foram recolhidos dados iniciais e intermédios relativos à motivação e satisfação dos sujeitos através de um questionário. A competência aquática inicial e final foi avaliada com base na observação de registos vídeo da prestação aquática: (i) NPD: teste de 100m de nado contínuo composto por 50m crol e 50m costas (incluindo partida regulamentar e viragens); (ii) PA (jogo 3x3); (iii) NA (esquema individual). O programa iniciou com 6 participantes, tendo havido uma desistência na 8ª sessão. Três participantes entraram no programa entre a 9ª e a 10ª sessões e após a sua primeira aula aderiram de forma voluntária e entusiasta ao programa. Não se verificaram alterações objetivas na motivação e na satisfação dos participantes. A competência aquática evoluiu de forma evidente em 9 conteúdos da natação pura desportiva e de forma mais discreta em 5 conteúdos da natação artística e 4 do polo aquático. A desistência de um participante foi motivada pela aversão do mesmo à modalidade de polo aquático, o que indicia que os programas de ensino multidisciplinar terão de coabitar com ofertas de ensino clássicas. A reação positiva e muito entusiasta ao programa terá determinado a ausência de diferenças na motivação e na satisfação entre o início e o meio do programa e revela a boa predisposição dos adultos para uma prática aquática mais diversificada. Todos os participantes aprenderam ou otimizaram 18 conteúdos. Apenas uma praticante não conseguiu vencer o medo de rodar sobre o eixo transversal, o que inviabilizou a aprendizagem da viragem de rolamento. Os conteúdos da natação pura desportiva foram melhor consolidados, possivelmente devido ao maior tempo de prática e de experiência dos praticantes com a modalidade. Em conclusão, os resultados do estudo piloto parecem sustentar o interesse no ensino da Natação segundo uma abordagem multidisciplinar.

The purpose of this study was to investigate differences in Froude efficiency (ηF) and active drag (DA) between front crawl and backstroke at the same speed. ηF was investigated by the three-dimensional (3D) motion analysis using 10 male swimmers. The swimmers performed 50 m swims at four swimming speeds in each technique, and their whole body motion during one upper-limb cycle was quantified by a 3D direct linear transformation algorithm with manually digitized video footage. Stroke length (SL), stroke frequency (SF), the index of coordination (IdC), ηF, and the underwater body volume (UWVbody) were obtained. DA was assessed by the measuring residual thrust method (MRT method) using a different group of swimmers (six males) due to a sufficient experience and familiarization required for the method. A two-way repeated-measures ANOVA (trials and techniques as the factors) and a paired t-test were used for the outcomes from the 3D motion analysis and the MRT method, respectively. Swimmers had 8.3% longer SL, 5.4% lower SF, 14.3% smaller IdC, and 30.8% higher ηF in front crawl than backstroke in the 3D motion analysis (all p < 0.01), which suggest that front crawl is more efficient than backstroke. Backstroke had 25% larger DA at 1.2 m⋅s–1 than front crawl (p < 0.01) in the MRT trial. A 4% difference in UWVbody (p < 0.001) between the two techniques in the 3D motion analysis also indirectly showed that the pressure drag and friction drag were probably larger in backstroke than in front crawl. In conclusion, front crawl is more efficient and has a smaller DA than backstroke at the same swimming speed.

Background: Physical exercise can affect the immune system. We studied the effect of antioxidants on hematological and immune biomarkers after heavy training. Methods: 24 well-trained and well-fed male firefighters were randomly divided into supplemented and placebo groups, and tested for immunology-related variables using venous blood samples in the fasting state, pre- (M1) and post- (M2) five weeks of daily micronutrient supplementation (15 mg of beta-carotene, 200 mg of vitamin C, 136 mg of vitamin E, 200 μg of selenium, 15 mg of zinc, 100 mg of magnesium). Total leukocytes and a differential count for five populations were determined using standard procedures (MAXM—Beckman Coulter Diagnostics; Brea, CA, USA). Lymphocyte subsets were determined through immunophenotyping. Results: Although all values were within the normal range for healthy adults and athletes in the supplemented group (SG), mean CD3+CD8+, CD8+ and CD16+CD56+ decreased (p < 0.05; small to moderate effects), while mean CD4+, CD19+ and CD4+/CD8+ increased (p < 0.05; small effects) after five-weeks. Regarding the placebo group (PG), higher total leukocyte count (p < 0.05; trivial effect) and natural killer cells percentage (CD16+CD56+; p < 0.05; moderate effect) were observed when comparing M1 and M2. Conclusions: Antioxidants supplementation did not alter well-fed male firefighters recruit firefighters’ immune cell response during the five-week physical training program.

Concepts about motor unit recruitment are important learning contents in exercise physiology and biomechanics classes that are usually taught theoretically. In the last few years, great advances have occurred in the decomposition of surface electromyography, allowing the learning of theoretical contents in an experimental way. In this tutorial paper, we have described the decomposition of surface electromyography methodological aspects and examples to teach motor unit recruitment concepts in exercise physiology and biomechanics practical lessons. This work has the aim to facilitate physiology and biomechanics academics to introduce this technique in practical classes.

Acute ergogenic effects of wearing occlusal splints have been reported for aerobic and anaerobic exercises, but the literature centered on performance improvement by using jaw repositioning splints is scarce. We aimed to analyze the effect of wearing a 50% lower jaw advancement splint on biophysical and perceptual responses at low to severe running intensities. Sixteen middle- and long-distance runners performed twice a 7 × 800 m intermittent running protocol (with 1 km·h−1 increments and 30 s rest periods) in an outdoor track field using two lower intraoral splints (a placebo and a lower jaw advancer). These devices were custom manufactured for each participant and a randomized and repeated measure design was used to compare conditions. No differences between placebo and lower jaw advancer were found (e.g., 52.1 ± 9.9 vs. 53.9 ± 10.7 mL·kg−1·min−1 of oxygen uptake, 3.30 ± 0.44 vs. 3.29 ± 0.43 m of stride length and 16 ± 3 vs. 16 ± 2 Borg scores), but small effects were sometimes observed (e.g., 109.2 ± 22.5 vs. 112.7 ± 25.2 L·min−1 of ventilation, ES = −0.42). Therefore, this jaw advancement splint had no substantial ergogenic effect on biophysical and perceptual responses when running at different intensities.

The emergence of physiological monitoring technologies has produced exceptional opportunities for real-time collection and analysis of workers’ physiological information. To benefit from these safety and health prognostic opportunities, research efforts have explored the applicability of these devices to control workers’ wellbeing levels during occupational activities. A systematic review is proposed to summarise up-to-date progress in applying physiological monitoring systems for occupational groups. Adhering with the PRISMA Statement, five databases were searched from 2014 to 2021, and 12 keywords were combined, concluding with the selection of 38 articles. Sources of risk of bias were assessed regarding randomisation procedures, selective outcome reporting and generalisability of results. Assessment procedures involving non-invasive methods applied with health and safety-related goals were filtered. Working-age participants from homogeneous occupational groups were selected, with these groups primarily including firefighters and construction workers. Research objectives were mainly directed to assess heat stress and physiological workload demands. Heart rate related variables, thermal responses and motion tracking through accelerometry were the most common approaches. Overall, wearable sensors proved to be valid tools for assessing physiological status in working environments. Future research should focus on conducting sensor fusion assessments, engaging wearables in real-time evaluation methods and giving continuous feedback to workers and practitioners.

Abstract Active video games (exergames) may provide short-term increase in energy expenditure. We explored the effects of gender and prior experience on aerobic and anaerobic energy systems contributions, and the activity profiles of 40 participants playing with a swimming exergame. We recorded oxygen consumption and assessed blood lactate after each swimming technique. We also filmed participants’ gameplays, divided them into different phases and tagged them as active or inactive. Anaerobic pathway accounted for 8.9 ± 5.6% of total energy expenditure and although experienced players were less active compared to novice counterparts (η²

The aim of this study was to trial several attacking offensive sequences as representative for further use in research on the perceptual-cognitive skills of water polo players. Elite water polo coaches were presented with separate test film sequences encompassing 80 structured water polo offensive plays. Each clip was approximately 6 s–7 s long with an inter-clip interval of 5 s–10 s, where a red dot was displayed on-screen at the start of the clip to indicate the area of first appearance of the ball. The order of presentation of the video clips was counterbalanced and randomly determined. The criteria were scored on a 5-point Likert-type scale. From the 80 clips presented, only 56 showed high agreement (W = 1; p < 0.05) and internal consistence reliability between the expert observers (α = 0.980; p < 0.05). Furthermore, a very high reproducibility (Z = 0; p = 1) was obtained between viewing sessions. The results obtained determine that 56 offensive scenarios were representative of the water polo game and as such may be useful in evaluating the perceptual-cognitive skills of the players.

The surf pop-up is a unique and challenging skill, critical to successful surfing. Hypothesizing that anthropometric characteristics of surfers influence the pop-up performance, we aimed to measure kinematics and ground-reaction forces (GRF) during a simulated pop-up motion, and to relate these variables with anthropometric characteristics. Twenty-three male surfers (age: 28.4 ± 10.1 years old; body mass: 68.3 ± 10.8 kg; height: 1.73 ± 0.07 m; time of practice: 12.4 ± 8.9 years; arm-span: 1.75 ± 8.9 m) perform a simulated pop-up in the laboratory, while GRF and 3D motion-capture data were acquired. The duration of the pop-up was 1.20 ± 0.19 s (60% push-up and 40% reaching/landing phase). During the push-up, the hands were placed 0.46 ± 0.05 m apart and generated a relative total peak-force of 0.99 ± 0.10 N/Weight, with symmetrical impulse of 0.30 ± 0.05 N·s/Weight for the dominant and 0.29 ± 0.07 N·s/Weight for the nondominant hand. Elbow angles were not different during the peak force application (110 ± 18° vs. 112 ± 18°, respectively) of the push-up phase. During the landing phase, the feet were placed 0.63 ± 0.10 m apart and generated a relative peak force of 1.63 ± 0.18 N/Weight. The impact force during landing was applied unevenly between the rear foot (28%) and the front foot (72%). In conclusion, most anthropometric-related variables showed no relationship with performance variables, with the exception of an inverse relationship between muscle mass and pop-up total duration. We also observed no differences in upper- and lower-body kinematics between the dominant vs. nondominant hands and among surfers who preferred a regular vs. “goofy-foot” stance. Finally, the force profiles between hands were similar and symmetric, while the lower extremities during the reaching phase were different, with the front foot applying greater force than that of the rear foot.