Can Data-Driven Supervised Machine Learning Approaches Applied to Infrared Thermal Imaging Data Estimate Muscular Activity and Fatigue?

Surface electromyography (sEMG) is the acquisition, from the skin, of the electrical signal produced by muscle activation. Usually, sEMG is measured through electrodes with electrolytic gel, which often causes skin irritation. Capacitive contactless electrodes have been developed to overcome this limitation. However, contactless EMG devices are still sensitive to motion artifacts and often not comfortable for long monitoring. In this study, a non-invasive contactless method to estimate parameters indicative of muscular activity and fatigue, as they are assessed by EMG, through infrared thermal imaging (IRI) and cross-validated machine learning (ML) approaches is described. Particularly, 10 healthy participants underwent five series of bodyweight squats until exhaustion interspersed by 1 min of rest. During exercising, the vastus medialis activity and its temperature were measured through sEMG and IRI, respectively. The EMG average rectified value (ARV) and the median frequency of the power spectral density (MDF) of each series were estimated through several ML approaches applied to IRI features, obtaining good estimation performances (r = 0.886, p < 0.001 for ARV, and r = 0.661, p < 0.001 for MDF). Although EMG and IRI measure physiological processes of a different nature and are not interchangeable, these results suggest a potential link between skin temperature and muscle activity and fatigue, fostering the employment of contactless methods to deliver metrics of muscular activity in a non-invasive and comfortable manner in sports and clinical applications.

Wellness Forecasting by External and Internal Workloads in Elite Soccer Players: A Machine Learning Approach

Training for success has increasingly become a balance between maintaining high performance standards and avoiding the negative consequences of accumulated fatigue. The aim of this study is to develop a big data analytics framework to predict players’ wellness according to the external and internal workloads performed in previous days. Such a framework is useful for coaches and staff to simulate the players’ response to scheduled training in order to adapt the training stimulus to the players’ fatigue response. 17 players competing in the Italian championship (Serie A) were recruited for this study. Players’ Global Position System (GPS) data was recorded during each training and match. Moreover, every morning each player has filled in a questionnaire about their perceived wellness (WI) that consists of a 7-point Likert scale for 4 items (fatigue, sleep, stress, and muscle soreness). Finally, the rate of perceived exertion (RPE) was used to assess the effort performed by the players after each training or match. The main findings of this study are that it is possible to accurately estimate players’ WI considering their workload history as input. The machine learning framework proposed in this study is useful for sports scientists, athletic trainers, and coaches to maximise the periodization of the training based on the physiological requests of a specific period of the season.

Changes in Upper-Body Muscular Strength and Power in Paralympic Swimmers: Effects of Training Confinement during the COVID-19 Pandemic

The aim of this case series was to evaluate the effectiveness of a dry-land home-training program conducted during the COVID-19 pandemic period in Paralympic swimmers. Previous evidence showed the importance of muscular strength and power training for Paralympic swimmers due to the positive relationship between severity of impairment, swimming technique and biomechanics parameters. Specifically, we aimed to analyze: (i) the effects of a customized training regime conducted pre, during and post restrictions on upper-body muscular strength and power (one repetition maximum, mean propulsive velocity, and mean relative propulsive power) compared to a regular gym-based program; (ii) the associations between mean propulsive velocity and load during two upper body exercises in order to estimate the one repetition maximum. Four elite Paralympic swimmers were retrospectively analyzed in upper-body muscular strength, mean propulsive velocity and mean relative propulsive power in bench press and lat pull-down exercises at three time points: T0 (prior the Lockdown period), T1 (immediately after the Lockdown confinement), T2 (sixteen weeks after returning to gym training). Our findings suggest a very likely decrement in one repetition maximum, mean propulsive velocity, and mean relative propulsive power during the Lockdown period compared with the T0 period with a subsequent very likely increment in one repetition maximum after returning to gym training (T2) compared with the lockdown period (T0). Conversely, mean relative propulsive power showed an unclear improvement in all athletes in T2 compared with T1. These results were also corroborated by the Friedman’s test followed by the Dunn’s pairwise comparison that mainly showed a decrement from T0 to T1 (p < 0.05). At the same time, it appears that muscle strength and power could be rapidly restored close to the pre-lockdown levels following an adequate training program in the gym, albeit without significance (p > 0.05). Finally, the close relationship between mean propulsive velocity and load in bench press and lat pull-down exercises was also confirmed in para swimming, making a possible estimation of one repetition maximum.

Regional Bioelectrical Phase Angle Is More Informative than Whole-Body Phase Angle for Monitoring Neuromuscular Performance: A Pilot Study in Elite Young Soccer Players

Background: The objective of this study was to investigate the association between regional and total phase angle (PhA) with lower-body neuromuscular performance in young elite soccer players. Methods: Sixteen elite male soccer players (14.3 ± 1.0 years) participated in this study. Lower (LPhA)- and upper (UPhA)-hemisome PhA together with whole-body PhA (WBPhA) were measured by a bioelectrical-impedance analysis (BIA), while appendicular arm and leg lean soft tissue (ALST and LLST, respectively) were estimated. Urine osmolarity (UOsm) and urine-specific gravity (USG) were also considered. Sprints over 10 m and 20 m and countermovement jump (CMJ) tests were employed to evaluate neuromuscular performance. Results: LPhA (p = 0.003) and UOsm (p = 0.012) explained 62% of the variance in the 10 m sprint. UOsm (p = 0.001) and both LPhA (p < 0.001) and WBPhA (p = 0.024) explained 81% of the total variance in the 20 m sprint. The CMJ height was affected by LPhA (p < 0.001) and UOsm (p = 0.024), which overall explained 68% of its variance (p < 0.05), while 93% of the CMJ power variance was explained by LPhA (p < 0.001), ALST (p < 0.001), and WBPhA (p = 0.011). Conclusions: Regional PhA is a relevant and non-invasive tool to monitor lower-body neuromuscular performance in elite youth soccer. Specifically, LPhA may be favored over WBPhA as more informative.

Central and Peripheral Thermal Signatures of Brain-Derived Fatigue during Unilateral Resistance Exercise: A Preliminary Study

Simple Summary

Fatigue is considered a brain-derived emotion that could impact performance during the execution of physical exercises. Infrared thermography is a valuable technique able to measure the psychophysiological state associated with emotions in a contactless manner. The aim of the study is to test the capability of infrared thermography to evaluate the central and peripheral physiological effect of fatigue through facial skin and muscle temperature modulations collected during the execution of a unilateral resistance exercise of the lower limb. Both time- and frequency-domain analyses were performed on the temperature time course of the face and limbs. Particularly, significant correlations between features extracted from the thermal signals and the perceived exertion were found. These findings confirmed the ability of thermal imaging to detect both peripheral and central effects of fatigue in response to physical exercises. These results could foster the employment of infrared thermography to monitor the psychophysiological state of the athletes during training. The possibility to calibrate the training load in accordance with the psychophysiological conditions could improve the performance of the athletes during the training process and competitions.

Abstract

Infrared thermography (IRT) allows to evaluate the psychophysiological state associated with emotions from facial temperature modulations. As fatigue is a brain-derived emotion, it is possible to hypothesize that facial temperature could provide information regarding the fatigue related to exercise. The aim of this study was to investigate the capability of IRT to assess the central and peripheral physiological effect of fatigue by measuring facial skin and muscle temperature modulations in response to a unilateral knee extension exercise until exhaustion. Rate of perceived exertion (RPE) was recorded at the end of the exercise. Both time- (∆T_ROI: pre–post exercise temperature variation) and frequency-domain (∆PSD: pre–post exercise power spectral density variation of specific frequency bands) analyses were performed to extract features from regions of interest (ROIs) positioned on the exercised and nonexercised leg, nose tip, and corrugator. The ANOVA-RM revealed a significant difference between ∆T_ROI (F_(1.41,9.81) = 15.14; p = 0.0018), and between ∆PSD of myogenic (F_(1.34,9.39) = 15.20; p = 0.0021) and neurogenic bands (F_(1.75,12.26) = 9.96; p = 0.0034) of different ROIs. Moreover, significant correlations between thermal features and RPE were found. These findings suggest that IRT could assess both peripheral and central responses to physical exercise. Its applicability in monitoring the psychophysiological responses to exercise should be further explored

Effects of a nasal breathing protocol on physical fitness and pulmonary function in young basketball players

BACKGROUND

Respiratory muscle training has been shown to provide positive effects for both health and performance purposes. The aim of this study was to evaluate the effects of a six-week period of nasal breathing on pulmonary function and cardio-respiratory fitness in young basketball players.

METHODS

Thirty-four, male, basketball players were enrolled and assigned either to experimental group (EG) or to control group (CG). All participants were tested for Yo-Yo Intermittent Recovery level 1 (Yo-Yo IR1), Shuttle Sprint Test (SST), Forced Vitality Capacity (FVC), Forced Expiratory Volume in one second (FEV1) and Peak Expiratory Flow (PEF). EG group followed reduced breathing frequency training program focused on intermittent running exercises while performing nasal breathing.

RESULTS

The main findings were significant interactions in Yo-Yo IR1 test, FVC, FEV1 and PEF (p<0.05) in favour of EG compared to CG. Conversely, no significant changes were detected between EG and CG in the SST total time.

CONCLUSIONS

Young basketball players may benefit from nasal breathing protocol during their regular training practice leading remarkable improvements in both physical fitness and pulmonary function.

Stand age, degree of encroachment and soil characteristics modulate changes of C and N cycles in dry grassland soils invaded by the N2-fixing shrub Amorpha fruticosa

The N₂-fixing shrub Amorpha fruticosa L. is rapidly spreading in the dry riparian natural grasslands of Europe, altering ecosystem functions and depleting plant diversity. Alteration of the N cycle represents the key factor involved in invasions by N₂-fixing plants with cascading effects on plant species richness. We hypothesized that A. fruticosa encroachment strongly impacts not only the N but also the C cycle and that the magnitude of such alterations may be modulated by soil characteristics. To test these hypotheses, we selected four river floodplains in North East of Italy and compared natural uninvaded grasslands with half invaded and completely invaded sites, based on A. fruticosa stand characteristic and relevant leaf traits and on soil properties related to soil texture and to C and N cycles. Soil organic matter mineralisation, ammonification and nitrification rates were determined. Soil nitrification increased remarkably with plant invasion while ammonification was significantly higher only in half invaded sites. Soil organic matter mineralisation, microbial biomass C sustained per soil organic C unit and nitrification positively correlated with stand age, regardless to the stage of the encroachment. Mineralisation and nitrification increased with soil organic C and total N in uninvaded and completely invaded sites, but decreased in half invaded sites. At the half invasion stage, trends in nitrification and CO₂ mineralisation were transitionally reverted and remediation may be facilitated by less pronounced changes in soil properties compared to completely invaded sites. Direct effects of plant invasion are modulated by the action of soil characteristics such as soil organic C and clay contents, with soils rich in organic C showing larger nitrification and mineralisation rates.

Association of phase angle and appendicular upper and lower body lean soft tissue with physical performance in young elite soccer players: a pilot study

BACKGROUND

In soccer, a better understanding of the bioimpedance parameters with physical performance may be useful to efficiently monitor and interpret players' performance variation throughout a certain period of the season. Therefore, this study aimed to examine the association between phase angle (PhA) and arms and legs lean soft tissue (ALST and LLST) with physical performance in young elite soccer players.

METHODS

Fifteen young male elite soccer players (age = 14.2±1.2 years, BMI = 20.51±1.38 kg/m2) participated in this investigation. Raw bioimpedance parameters (reactance, resistance, and phase angle) were obtained by a bioelectrical impedance analysis (BIA) device. Then, ALST and LLST were estimated. All players underwent a physical testing battery including countermovement jump (CMJ), 10-m and 20-m sprint, and Yo-Yo Intermittent Recovery Test level 1 (YoYo IRTL1) in the domains of anaerobic and aerobic performance, respectively.

RESULTS

The results showed that LST (total, arms and legs) positively correlated with CMJ (0.64 < r < 0.69; p < 0.001) and negatively correlated with 10-m (-0.59 < r < -0.63; p < 0.05) and 20-m sprint (-0.67 < r < -0.73; p < 0.001), while PhA positively correlated with CMJ (r = 0.57; p < 0.05) and negatively correlated (r = -0.54; p < 0.05) only with 20-m sprint. No significant association was found between the BIA-related parameters (PhA and LST) and Yo- Yo IRT level 1.

CONCLUSIONS

The present findings highlight the existing association of PhA and LST with jumping and sprinting performance in young elite soccer players. This result supports the use of BIA-related measures as a simple and practical approach to monitoring anaerobic performance changes, rather than aerobic, over time throughout the season.

Perceptual and Biochemical Responses in Relation to Different Match-Day +2 Training Interventions in Soccer Players

The aim of this study was to examine the impact of two different post-match training interventions on the subsequent recovery of perceptual and biochemical parameters after the game. In a crossover design, eight sub-elite players underwent a soccer-specific training (SST) and an active recovery (AR) regimen on the second day after a match (+48 h). Muscle soreness as well as muscle damage (creatine kinase, CK), inflammatory (C-reactive protein and interleukin 6), immunological (e.g., lymphocytes, neutrophils, and monocytes), and endocrine (cortisol) markers were obtained at baseline (-72 h), immediately after (0 h), and 72 h post-match (+72 h). AR promoted a higher restoration of muscle soreness values (P = 0.004, η2 p = 0.49) together with a better restoration of CK within 72 h post-match compared with SST (P = 0.04, η2 p = 0.36). Conversely, no significant (P > 0.05, η2 p < 0.91) differences were observed in the recovery timeframe of inflammatory, immunological, and endocrine responses between SST and AR. Overall, AR elicited a quicker muscle soreness and CK restoration compared to SST intervention at 72 h post-match. Such information provides novel evidence-based findings on the appropriateness of different recovery strategies and may aid to improve the practitioners' decision-making process when two consecutive games are played within 3 days.

Relationship of regional and whole body morphology to vertical jump in elite soccer players: a data-driven approach

BACKGROUND

This study aimed to analyse the relationship of regional and whole body morphology to vertical jump performance and to compare the morphological features outlining high and low performers in professional soccer players.

METHODS

Twenty-one male soccer players were recruited. Whole and regional (upper and lower limbs) features were obtained in the form of body dimensional measurements. Then, all players were tested for vertical jump performance. A data-driven approach was used to group players according to their jump performance parameters (high vs low).

RESULTS

The regional morphological features presented higher correlations with vertical jump than whole body features. High and low performers were significantly different among upperand lower-limb morphology. No differences were observed among whole body features.

CONCLUSIONS

These findings indicate that, rather than the whole body, the use of morphological features linked to specific body regions may ensure a better interpretation of the soccer players' physical potential in jump performance.

Effects of Non-Sport-Specific Versus Sport-Specific Training on Physical Performance and Perceptual Response in Young Football Players

This study aimed to compare the effects of non-sport-specific and sport-specific training methods on physical performance and perceptual response in young football players. Seventy-nine under 11 participants were selected and assigned to non-sport-specific (NSSG), sport-specific (SSG), and control (CNTG) groups. The NSSG training protocol consisted of combined stimuli based on balance, agility, and jump rope drills. The SSG training protocol included technical exercises, defensive and offensive game-based drills, and a small-sided game. The CNTG included the participants not taking part in any sport training. All participants were tested for general motor coordination (Harre test), dynamic balance (Lower Quarter Y-balance test), and dribbling before and after 10 weeks of training (NSSG and SSG) or habitual activity (CNTG). At post-intervention, perceived enjoyment was requested by the Physical Activity Enjoyment Scale (PACES). A two-way repeated measure analysis of covariance was used to detect interactions and main effects of time and groups controlling for baseline values. Whereas, a one-way analysis of variance was used to evaluate PACES-related differences between groups. NSSG gained greater improvements (p < 0.05) compared with SSG in the Harre and Lower Quarter Y-balance tests, while dribbling skills improved similarly in both groups. Regarding PACES, NSSG and SSG presented a comparable perceived enjoyment. These findings suggest that a 10-week non-sport-specific training is an enjoyable practice capable to promote greater improvements in general motor coordination and dynamic balance compared with sport-specific training in youth football players. This can occur without impairment of football-specific skills.

A MIP-based low-cost electrochemical sensor for 2-furaldehyde detection in beverages

There is an increasing interest in determining the concentration of furanic compounds naturally formed in food aqueous matrices, by in situ, fast and low-cost methods. A sensor presenting such characteristics is here proposed, and characterized. It is based on a molecularly imprinted polymer (MIP) as a receptor with electrochemical transduction on a screen printed cell (SPC). The molecularly imprinted polymer has been developed for a particular furanic derivative, 2-furaldehyde (2-FAL). The detection bases on the reduction of 2-FAL selectively adsorbed on the polymer layer in contact with the working electrode. The polymer layer is simply formed by in situ polymerization, directly over the SPC and it was characterized by IR, SEM and electrochemical methods. Even if based on an easy and fast preparation procedure, the layer sufficiently adheres to the cell surface giving a reusable sensor. Square wave voltammetry (SWV) was applied as the signal acquisition method. The sensor performance in aqueous solution (NaCl 0.1 M) was tested, obtaining that the dose-response curve is fitted by the Langmuir adsorption isotherm. The sensitivity, and so the limit of detection, were noticeably improved by a chemometric approach based on the Design of experiment method. (optimized conditions: E_step = 0.03 V, E_pulse = 0.066 V, f = 31 s^-1). In water solution at pH around neutrality the dynamic range was from about 50 μM to 20 mM. Similar results were obtained for a white wine containing 12% ethanol, which has been considered as a typical example of beverage possibly containing furhaldehydes. The higher limit of quantification can be modulated by the amount of MIP deposited, while the lower detection limit by the conditions of the electrochemical measurement.

Slow-Speed Resistance Training Increases Skeletal Muscle Contractile Properties and Power Production Capacity in Elite Futsal Players

The purpose of this study was to explore the effects of slow-speed resistance training with low intensity (SRT) on muscle power output in elite futsal players with respect to traditional resistance training. The authors hypothesized that the muscle deoxygenation during SRT causes early recruitment of fast twitch fibers that would positively affect strength and power performance. Thirty male elite futsal players were recruited and randomly assigned either to SRT group or to traditional resistance training (TRT) group. All players underwent an 8-weeks experimental protocol consisting of 2 training sessions per week at both leg curl and leg extension machines. In the SRT, players lifted 50% of one maximum repetition (1RM) involving 3 s for eccentric and concentric actions. In the TRT, players lifted 80% of 1RM involving 1 s for eccentric and concentric actions. All players were tested twice (pre and post) for sprint and jump performances, maximal isometric voluntary contraction (MVC) and maximal isokinetic peak torque (Peak TQ) and total work (TW) at 60 and 120°/s (on knee extensors and flexors). The two groups presented remarkable differences in the within-group changes for all the variables. SRT exhibited greater improvements in both Peak TQ and TW for knee extensors and flexors at 120°/s. Conversely, TRT showed greater improvements in MVC, and in both Peak TQ and TW for knee extensors and flexors at 60°/s, except for Peak TQ of the knee extensors, where no significant difference was found between TRT and SRT. Countermovement jump showed a decrease in eccentric time and an increase in concentric force in SRT group. SRT and TRT resulted effective to enhance the strength performance indices during the 8-weeks experimental protocol. Peak torque at 120°/s explained more of the contractile characteristic effects of SRT training than MVC, suggesting that slow-speed training can cause fast twitch fibers hypertrophy in elite athletes. Since slow-speed training is supposed to produce a decreased exercise-induced muscle damage, SRT method is a suitable option in strength training for futsal and team sports.

Change of direction asymmetry across different age categories in youth soccer

Background

In youth, the development of change of direction (COD) and sprint performance is a key component for successfully competing in soccer across age. During a COD, the presence of directional asymmetries may be detrimental due to the unpredictable nature of the sport. Therefore, the aims of the study were to investigate asymmetries in COD ability and to examine the differences in COD and sprint performance across age in young soccer players.

Methods

Sixty-eight sub-elite soccer players of different age categories (U18, U17, U16, U15) were tested on a 10-m linear sprint test and 90°COD (5-m entry and exit) test in both directions. Asymmetric index (AI) of COD deficit was obtained for dominant (fastest) and non-dominant directions (slowest).

Results

The results showed that U16 were more asymmetrical than U18, U17, and U15 from large to moderate effects. The sprint time improved linearly across age with U18 and U15 displaying the fastest and slowest 10-m sprint performance (p < 0.01), respectively. Moreover, COD ability measured by COD deficit did not change across age (p > 0.05).

Conclusion

Given the results of this study, practitioners are encouraged to assess asymmetries between dominant and non-dominant directions rather than solely players’ COD ability in young soccer players.

Kinematics and Kinetics of Bulgarian-Bag-Overloaded Sprints in Young Athletes

Background: Effective sprinting requires large acceleration capabilities. To accelerate, large amount of force must be produced and applied effectively. The use of different implements such as sleds and vests can increase the amount of force produced and alter sprinting effectiveness. We propose the use of increasing overload via the Bulgarian Bag (BB) as a means to modify athletes’ sprint and acutely increase force and power production. Methods: 24 young athletes performed three sprints over 20 m in three different conditions: unloaded (BW) and loaded with BB weighing 2.5% (BB2.5) and 5% (BB5) of the athlete’s body mass. Sprint times at 2.5, 5, 10, 15, and 20 m were acquired and used to compute the force–velocity relationship for the sprints. Maximal velocity (V0), peak force (F0), peak power (PP), and decrease in ratio of force (D_RF) were computed. Results: the additional load caused a decrease in sprint times (p < 0.05) and V0 (p = 0.028), conversely no differences were found for F0 (p = 0.21), PP (p = 0.50), and D_RF (p = 0.83). Conclusions: Based on those findings, BB can be an alternative method to effectively overload sprint training toward improving sprinting performance.

A New Strategy to Integrate Heath-Carter Somatotype Assessment with Bioelectrical Impedance Analysis in Elite Soccer Player

Easy-to-apply and quick methods for evaluate body composition are often preferred when assessing soccer teams. This study aimed to develop new equations for the somatotype quantification that would reduce the anthropometric measurements required by the Heath and Carter method, integrating the somatotype assessment to the bioelectrical impedance analysis (BIA). One hundred and seventy-six male elite soccer players (age 26.9 ± 4.5 years), registered in the Italian first division (Serie A), underwent anthropometric measurements and BIA. Endomorphy, mesomorphy, and ectomorphy were obtained according to the Heath and Carter method, while fat mass (FM) and fat free mass (FFM) estimated using a BIA-derived equation specific for athletes. The participants were randomly split into development (n = 117) and validation groups (n = 59, 1/3 of sample). The developed models including resistance2/stature, FM%, FFM, contracted arm and calf circumference, triceps, and supraspinal skinfolds had high predictive ability for endomorphy (R2 = 0.83, Standard Error of Estimate (SEE) = 0.16) mesomorphy (R2 = 0.80, SEE = 0.36), and ectomorphy (endomorphy (R2 = 0.87, SEE = 0.22). Cross validation revealed R2 of 0.80, 0.84, 0.87 for endomorphy, mesomorphy, and ectomorphy, respectively. The proposed strategy allows the integration of somatotype assessment to BIA in soccer players, reducing the number of instruments and measurements required by the Heath and Carter approach.

Mental fatigue impairs physical activity, technical and decision-making performance during small-sided games

The aim of this study was to investigate the effects of mental fatigue on physical activity, technical and decision-making performance during small-sided games. Nine sub-elite soccer players were enrolled in the study. The players performed two small-sided games on two occasions within a crossover experimental design. Before each game, they underwent a mental fatiguing task (Stroop task) and a control task (documentary watching) in a randomized, counterbalanced order. Players' physical activity, technical, and decision-making performance were obtained during small-sided games by GPS and video scouting. Results showed that distance in acceleration covered per min, negative passes, passing accuracy, and shot accuracy were likely impaired than control task after a mental fatiguing protocol. Decision-making performance of negative passes, passes accuracy, and dribbling accuracy resulted also likely decreased compared with control task. These findings demonstrated that mental fatigue impacted on technical, GPS-derived, and soccer-specific decision-making performance during SSG. In conclusion, avoiding cognitively demanding tasks before playing soccer-specific activities may be advisable to preserve players' physical activity, technical, and decision-making skills.

Importance of anthropometric features to predict physical performance in elite youth soccer: a machine learning approach

The present study aimed to determine the contribution of soccer players' anthropometric features to predict their physical performance. Sixteen players, from a professional youth soccer academy, were recruited. Several anthropometric features such as corrected arm muscle area (AMA_corr), arm muscle circumference (AMC) and right and left suprapatellar girths (RSPG and LSPG) were employed in this study. Players' physical performance was assessed by the change of direction (COD), sprint (10-m and 20-m), and vertical jump (CMJ) tests, and Yo-Yo Intermittent Recovery Test level 1 (Yo-Yo IRT1). Using an extra tree regression (ETR) model, the anthropometric features permitted to accurately predict 10-m sprint, 20-m sprint and Yo-Yo IRTL 1 performance (p < 0.05). ETR showed that upper-body features as AMA_corr, and AMC affected 10-m and 20-m sprint performances, while lower-body features as RSPG and LSPG influenced the Yo-Yo IRTL 1 (Overall Gini importance ≥ 0.22). The model predicting COD and CMJ presented a poor level of prediction, suggesting that other factors, rather than anthropometric features, may concur to predict their changes in performance. These findings demonstrated that the upper- and lower-body anthropometric features are strictly related to sprint and aerobic fitness performance in elite youth soccer.

Acute Effect of Exercise on Cognitive Performance in Middle-Aged Adults: Aerobic Versus Balance

BACKGROUND

Recent evidence has suggested that chronic physical activities including balance exercises have positive effects on cognition, but their acute effects are still unknown. In the present study, the authors tested the hypothesis that an acute bout of balance exercise would enhance cognitive performance compared with aerobic activity.

METHODS

A total of 20 healthy middle-aged adults completed 2 acute 30-minute balance and moderate-intensity aerobic exercise sessions on 2 counterbalanced separate occasions. To assess cognitive functions, performance tasks in executive control, perceptual speed, and simple reaction time were tested before and immediately after each exercise session.

RESULTS

Although there were no significant interactions (time × exercise condition, P > .05), the main effects of time were significant in executive control (P < .05), perceptual speed (P < .05), and simple reaction time (P < .001), showing improvements after both exercises.

CONCLUSIONS

These findings highlight that both types of exercise (aerobic, more metabolic and less cognitively demanding; balance, more cognitively and less metabolically demanding) were able to positively affect simple reaction time performance, perceptual speed, and executive control independently of physiological adjustments occurring during aerobic or balance exercise.

Nutritional interventions for reducing the signs and symptoms of exercise-induced muscle damage and accelerate recovery in athletes: current knowledge, practical application and future perspectives

PURPOSE

This review provides an overview of the current knowledge of the nutritional strategies to treat the signs and symptoms related to EIMD. These strategies have been organized into the following sections based upon the quality and quantity of the scientific support available: (1) interventions with a good level of evidence; (2) interventions with some evidence and require more research; and (3) potential nutritional interventions with little to-no-evidence to support efficacy.

METHOD

Pubmed, EMBASE, Scopus and Web of Science were used. The search terms 'EIMD' and 'exercise-induced muscle damage' were individually concatenated with 'supplementation', 'athletes', 'recovery', 'adaptation', 'nutritional strategies', hormesis'.

RESULT

Supplementation with tart cherries, beetroot, pomegranate, creatine monohydrate and vitamin D appear to provide a prophylactic effect in reducing EIMD. β-hydroxy β-methylbutyrate, and the ingestion of protein, BCAA and milk could represent promising strategies to manage EIMD. Other nutritional interventions were identified but offered limited effect in the treatment of EIMD; however, inconsistencies in the dose and frequency of interventions might account for the lack of consensus regarding their efficacy.

CONCLUSION

There are clearly varying levels of evidence and practitioners should be mindful to refer to this evidence-base when prescribing to clients and athletes. One concern is the potential for these interventions to interfere with the exercise-recovery-adaptation continuum. Whilst there is no evidence that these interventions will blunt adaptation, it seems pragmatic to use a periodised approach to administering these strategies until data are in place to provide and evidence base on any interference effect on adaptation.

School self-efficacy is affected by gender and motor skills: findings from an Italian study

Background

Perceived school self-efficacy (SE) is an important variable in students’ activities as it affects their motivation and learning. Further, self-efficacy might represent a good predictor of performance, persistence and perseverance. Motor skills and other physical health determinants are extensively debated and linked to cognitive function in children of developmental age. However, inconclusive evidence supports a definitive relationship between perceived school SE and motor skills among schoolchildren. We conducted a cross-sectional study on 6–11-year-old schoolchildren to evaluate the extent by which perceived school SE and physical health determinants were related.

Methods

A SE questionnaire and motor performance battery tests were administered to primary school pupils recruited from 154 sampled schools of northwest Italy. Perceived SE at school was assessed via 12 items from the Caprara’s questionnaire. Motor performance scores were obtained from motor skill tests: 4 × 10 m shuttle run test, SRT; standing broad jump, SBJ; six-minute walking test, 6MWT.

Results

A total of 3,962 children (M = 2,019; F = 1943) were studied and 68% were normal weight. Overall, a 58% of the sample perceived a high SE, while, as to gender differences, a greater percentage of females perceived high levels of school SE with respect to any other level (χ² = 38.93, p < 0.0001). Results from multinomial logistic regression analysis revealed that: (i) females perceived higher SE compared to males; (ii) children who performed better in SRT and 6MWT showed higher levels of perceived school SE; (iii) no significant effect was registered for the body weight. Alternative strategies are encouraged to enhance SE through physical education: structured interventions might enhance both complex motor skills and high-order cognitive skills, like SE, in young children.

Italian consensus statement (2020) on return to play after lower limb muscle injury in football (soccer)

Return to play (RTP) decisions in football are currently based on expert opinion. No consensus guideline has been published to demonstrate an evidence-based decision-making process in football (soccer). Our aim was to provide a framework for evidence-based decision-making in RTP following lower limb muscle injuries sustained in football. A 1-day consensus meeting was held in Milan, on 31 August 2018, involving 66 national and international experts from various academic backgrounds. A narrative review of the current evidence for RTP decision-making in football was provided to delegates. Assembled experts came to a consensus on the best practice for managing RTP following lower limb muscle injuries via the Delphi process. Consensus was reached on (1) the definitions of 'return to training' and 'return to play' in football. We agreed on 'return to training' and RTP in football, the appropriate use of clinical and imaging assessments, and laboratory and field tests for return to training following lower limb muscle injury, and identified objective criteria for RTP based on global positioning system technology. Level of evidence IV, grade of recommendation D.

Gross Primary Productivity of Four European Ecosystems Constrained by Joint CO2 and COS Flux Measurements

Gross primary productivity (GPP), the gross uptake of carbon dioxide (CO2) by plant photosynthesis, is the primary driver of the land carbon sink, which presently removes around one quarter of the anthropogenic CO2 emissions each year. GPP, however, cannot be measured directly and the resulting uncertainty undermines our ability to project the magnitude of the future land carbon sink. Carbonyl sulfide (COS) has been proposed as an independent proxy for GPP as it diffuses into leaves in a fashion very similar to CO2, but in contrast to the latter is generally not emitted. Here we use concurrent ecosystem-scale flux measurements of CO2 and COS at four European biomes for a joint constraint on CO2 flux partitioning. The resulting GPP estimates generally agree with classical approaches relying exclusively on CO2 fluxes but indicate a systematic underestimation under low light conditions, demonstrating the importance of using multiple approaches for constraining present-day GPP.