Influence of Substitutions and Roles on Kinematic Variables in Professional Soccer Players.

In soccer, roles, and substitutions could make unclear how different physical capacities decrease over time and impact performance. This investigation aimed to analyze kinematic parameters and their changes over game time and provide information to effectively prescribe training programs. Data from four professional teams were analyzed, and all the teams competed in the Premier Division championship. Average metabolic power and high-intensity activities associated with critical moments in the match were considered in the comparisons. The video analysis system STATS SportVU collected the data during official matches. Players were assigned to a specific group according to their time played, categorized as follows: 0-15', 15-30', 30-45', 45-60', 60-75', 75-90', and > 90 min. Different roles, including forwards and wingers (FW), midfielders (MF), center-backs (CB), and side-backs (SB) were also considered. Significant differences (p<0.05) were found in different roles and within roles at different times played. The results highlighted how MF performance decreased over time, whereas CB was unaffected by time. SB spent more time at very high velocity than other roles, independently from the time played. These findings provide valuable information about the physical demands of official soccer games and could be used to review training prescriptions.

Return to training in soccer players after anterior cruciate ligament reconstruction: reflections and considerations.

This clinical and rehabilitative overview focuses on the return to unrestricted sporting activity, aiming to consolidate the scientific evidence surrounding the structural progression of athletes, particularly footballers, undergoing anterior cruciate ligament reconstruction (ACLR). A multidisciplinary approach necessitates a shared language and standardized methodologies. Unfortunately, significant disparities persist in the structural strategies guiding the decision-making process for returning to on-field activities, the latter stages of rehabilitation, and subsequent restoration of technical and tactical football abilities. Divergences in definitions, terminologies, and rehabilitation protocols can substantially influence final outcomes. Presently, scientific consensus studies regarding the decision-making process during the final stages of on-field rehabilitation are lacking. Nevertheless, this overview outlines and defines pivotal language parameters crucial for effective communication and the seamless integration of clinical and rehabilitative data among the diverse professionals involved in facilitating the athlete's return to peak performance. In conclusion, the successful resumption of competitive sporting activities for footballer's post ACLR demands a collaborative decision-making approach encompassing various professionals. Additionally, it necessitates a cohesive transition from rehabilitation to on-field work, aiming at reinstating athleticism, technical prowess, and tactical acumen.

Exploring the interplay between metabolic power and equivalent distance in training games and official matches in soccer: a machine learning approach.

Introduction: This study aimed to explore the interplay between metabolic power (MP) and equivalent distance (ED) and their respective roles in training games (TGs) and official soccer matches. Furthermore, the secondary objective was to investigate the connection between external training load (ETL), determined by the interplay of metabolic power and equivalent distance, and internal training load (ITL) assessed through HR-based methods, serving as a measure of criterion validity. Methods: Twenty-one elite professional male soccer players participated in the study. Players were monitored during 11 months of full training and overall official matches. The study used a dataset of 4269 training games and 380 official matches split into training and test sets. In terms of machine learning methods, the study applied several techniques, including K-Nearest Neighbors, Decision Tree, Random Forest, and Support-Vector Machine classifiers. The dataset was divided into two subsets: a training set used for model training and a test set used for evaluation. Results: Based on metabolic power and equivalent distance, the study successfully employed four machine learning methods to accurately distinguish between the two types of soccer activities: TGs and official matches. The area under the curve (AUC) values ranged from 0.90 to 0.96, demonstrating high discriminatory power, with accuracy levels ranging from 0.89 to 0.98. Furthermore, the significant correlations observed between Edwards' training load (TL) and TL calculated from metabolic power metrics confirm the validity of these variables in assessing external training load in soccer. The correlation coefficients (r values) ranged from 0.59 to 0.87, all reaching statistical significance at p < 0.001. Discussion: These results underscore the critical importance of investigating the interaction between metabolic power and equivalent distance in soccer. While the overall intensity may appear similar between TGs and official matches, it is evident that underlying factors contributing to this intensity differ significantly. This highlights the necessity for more comprehensive analyses of the specific elements influencing physical effort during these activities. By addressing this fundamental aspect, this study contributes valuable insights to the field of sports science, aiding in the development of tailored training programs and strategies that can optimize player performance and reduce the risk of injuries in elite soccer.

Golden ratio and self-similarity in swimming: breast-stroke and the back-stroke.

Introduction: Dynamics-on-graph concepts and generalized finite-length Fibonacci sequences have been used to characterize, from a temporal point of view, both human walking & running at a comfortable speed and front-crawl & butterfly swimming strokes at a middle/long distance pace. Such sequences, in which the golden ratio plays a crucial role to describe self-similar patterns, have been found to be subtly experimentally exhibited by healthy (but not pathological) walking subjects and elite swimmers, in terms of durations of gait/stroke-subphases with a clear physical meaning. Corresponding quantitative indices have been able to unveil the resulting hidden time-harmonic and self-similar structures. Results: In this study, we meaningfully extend such latest findings to the remaining two swimming strokes, namely, the breast-stroke and the back-stroke: breast-stroke, just like butterfly swimming, is highly technical and involves the complex coordination of the arm and leg actions, while back-stroke is definitely similar to front-crawl swimming. An experimental validation with reference to international-level swimmers is included.

Role of music therapy in improving cognitive function post-traumatic brain injury: A systematic review.

Cognitive deficits are one of the most prevalent impairments in patients with traumatic brain injury (TBI). Music therapy has the potential to be a valuable intervention for improving cognitive function. This review aimed to investigate the effects of music therapy on cognitive function in patients with TBI. Scopus, PubMed, REHABDATA, PEDro, EMBASE, and web of science were searched for experimental trials examining the impacts of music therapy on cognition in patients with TBI from inception until December 2022. Physiotherapy Evidence Database (PEDro) scale was used to evaluate the methodological quality of the included studies. Five studies met the inclusion criteria. A total of 122 patients with TBI were included in this review, 32% of whom were females. The PEDro scores ranged from four to seven, with a median of five. The findings showed that music therapy could be effective in improving executive function post-TBI, with limited evidence for the effects on memory and attention. Music therapy might be safe in patients with TBI. The evidence for the effect of music therapy on executive function in patients with TBI is promising. Further studies with larger sample sizes and long-term follow-ups are strongly needed.

Prevention of Secondary Injury after Anterior Cruciate Ligament Reconstruction: Relationship between Pelvic-Drop and Dynamic Knee Valgus.

(1) Background: Optimal neuromuscular, Lumbo-Pelvic-Hip Complex, and lower extremity control are associated with decreased risk factors for secondary anterior cruciate ligament (ACL) injury. This study aimed to analyze any asymmetries and malalignments in the Lumbo-Pelvic-Hip Complex and the lower limbs at 6 months after ACL reconstruction (ACLR). (2) Methods: We conducted an exploratory retrospective observational single-center study in patients during the outpatient postoperative rehabilitation program at ICOT (Latina, Italy). From January 2014 to June 2020, 181 patients were recruited, but only 100 patients (86 male 28 ± 0.6 years, 178 ± 0.5 height; 14 female 24 ± 2.0 years, 178 ± 3.0 height) were eligible for the inclusion criteria and studied 6 months after ACL reconstruction surgery. (3) Statistical analysis: Student's t-tests and Pearson's product-moment correlation coefficient were used to determine significant differences between affected and non-affected limbs and variables' association. (4) Results: The study shows a decrease in neuromuscular control of the Lumbo-Pelvic-Hip Complex and dynamic adaptive valgus of the knee at 6 months after ACLR (mean difference between pathological and healthy limb of dynamic adaptive valgus was -10.11 ± 8.19° 95% CI -14.84 to -9.34; mean value was 16.3 ± 6.8° 95% CI 14.04 to 18.55 for healthy limb and 4.2 ± 3.1° 95% CI 3.15 to 5.21 for pathological limb, p < 0.0001). The results also showed a relationship between dynamic adaptive valgus and contralateral pelvic drop (r = 0.78, 95% CI 0.62 to 0.88, magnitude of correlation very large). (5) Conclusions: The analysis showed an associative correlation between decreased postural control of the pelvic girdle and dynamic adaptive valgus of the knee in 38% of patients; this study highlights the usefulness of the Single-Leg Squat Test (SLST) as a clinical/functional assessment to evaluate the rehabilitation process and as a preventive tool to reduce the risk of second ACL injuries during the return to sport.

Transcutaneous spinal cord stimulation effects on spasticity in patients with spinal cord injury: A systematic review.

CONTEXT: Spasticity is one of the most prevalent impairments following spinal cord injury (SCI). It can lead to a decrease in the patient's functional level. Transcutaneous spinal cord stimulation (tSCS) has demonstrated motor function improvements following SCI. No systematic reviews were published examining the influences of tSCS on spasticity post-SCI. OBJECTIVES: This review aimed to investigate the effects of tSCS on spasticity in patients with SCI. METHODS: PubMed, SCOPUS, PEDro, CINAHL, MEDLINE, REHABDATA, AMED, and Web of Science databases were searched until June 2021. The Physiotherapy Evidence Database (PEDro) scale was used to assess the methodological quality of the selected studies. RESULTS: Six studies met the inclusion criteria. Five studies were pilot studies, and one was a case series. The scores on the PEDro scale ranged from two to four, with a median score of four. The results showed heterogenous evidence for the effects of tSCS on spasticity reduction post-SCI. CONCLUSIONS: TSCS appears safe and well-tolerated intervention in patients with SCI. The evidence for the effectiveness of tSCS on spasticity in chronic SCI patients is limited. Further randomized controlled studies are strongly needed to study the effects of tSCS on patients with SCI.

Hyperbaric oxygen therapy for cognitive impairments in patients with traumatic brain injury: A systematic review.

Cognitive deficits are the most common impairments after traumatic brain injury (TBI). It can be linked with poor physical function. Hyperbaric oxygen therapy (HBOT) increases blood flow and oxygen supply to the brain. This review aimed to summarize and evaluate the available literature on the influences of HBOT on cognitive deficits in patients with TBI. PubMed, SCOPUS, PEDro, REHABDATA, MIDLINE, CHINAL, EMBASE, and Web of Science were searched from inception until June 2021. The methodological quality was measured using the physiotherapy evidence database (PEDro) scale. Ten studies met the eligibility criteria. Six studies were randomized controlled trials, and four were pilot studies. The scores on the PEDro scale ranged from two to nine, with a median score of seven. The included studies showed heterogeneity results for the beneficial effects of HBOT on improving cognitive functions in patients with TBI. The evidence for the beneficial effects of HBOT on cognitive functions post-TBI was limited. Further randomized controlled trials with large sample sizes are strongly needed to understand the effects of HBOT on cognitive functions in patients with TBI.

Transcranial direct current stimulation for upper extremity spasticity rehabilitation in stroke survivors: A systematic review of randomized controlled trials.

OBJECTIVES: To examine the effects of transcranial direct current stimulation (tDCS) on upper extremity spasticity after stroke and to define the most effective tDCS parameters. LITERATURE SURVEY: Systematic review in the following databases: PubMed, SCOPUS, PEDro, CINAHL, MEDLINE, REHABDATA, AMED, and Web of Science databases. Studies up to June 2020 were included. METHODOLOGY: Studies were included if the sample was composed of individuals with stroke, the intervention followed a tDCS intervention (alone or combined with another intervention), and the study was a randomized controlled trial including at least one measurement assessing upper extremity spasticity. Two authors independently screened the included studies. Conflicting decisions between authors were resolved by discussion with the third author. The methodological quality was assessed using the Cochrane Collaboration's tool. The authors determined that the meta-analysis was not feasible due to the heterogeneity in the protocols among the included studies. SYNTHESIS: After the screening of 1204 records, a total of seven studies met the specified inclusion criteria and involved 320 participants (mean age = 60.3), 31.1% of whom were females. Patients with ischemic stroke comprised 77.2% of the total patients, and 42.2% were with right hemispheric stroke. Six studies exhibited "high" quality and one exhibited "moderate" quality. Five of the selected studies that combined the tDCS intervention and other traditional interventions showed a significant reduction in upper extremity spasticity after stroke following tDCS intervention. The other two studies that delivered tDCs alone did not show a significant difference. CONCLUSIONS: The evidence for the effect of tDCS on upper extremity spasticity after stroke was limited. The optimal tDCS treatment dosage remains unclear. Additional studies with large sample sizes and long-term follow-up are strongly warranted.

Noninvasive brain stimulation for cognitive rehabilitation following traumatic brain injury: A systematic review.

Traumatic brain injury (TBI) can cause numerous cognitive deficits. These deficits are associated with disability and reduction in quality of life. Noninvasive brain stimulation (NIBS) provides excitatory or inhibitory stimuli to the cerebral cortex. This review aimed to examine the effectiveness of NIBS (i.e., rTMS and tDCS) on cognitive functions in patients with TBI. PubMed, SCOPUS, PEDro, CINAHL, MEDLINE, REHABDATA, and Web of Science were searched from inception to May 2021. The risk of bias in the randomized controlled trials was assessed using the Cochrane Collaboration's instrument. The Physiotherapy Evidence Database (PEDro) scale was applied to evaluate the risk of bias in the non-randomized controlled trials. Ten studies met our inclusion criteria. Six studies used repetitive Transcranial Magnetic Stimulation (rTMS), and four used transcranial Direct Current Stimulation (tDCS) as cognitive rehabilitation interventions. The results showed heterogenous evidence for the effects of rTMS and tDCS on cognitive function outcomes in individuals with TBI. The evidence for the effects of NIBS on cognition following TBI was limited. TDCS and rTMS are safe and well-tolerated interventions post-TBI. The optimal stimulation sites and stimulation parameters remain unknown. Combining NIBS with traditional rehabilitation interventions may contribute to greater enhancements in cognitive functions post-TBI.

Proprioceptive Focal Stimulation (Equistasi®) for gait and postural balance rehabilitation in patients with Parkinson's disease: A systematic review.

Gait and postural deficits are the most common impairments in patients with Parkinson's Disease (PD). These impairments often reduce patients' quality of life. Equistasi® is a wearable proprioceptive stabilizer that converts body thermic energy into mechanical vibration. No systematic reviews have been published investigating the influences of Equistasi® on gait and postural control in patients with PD. This review aimed to examine the effects of proprioceptive focal stimulation (Equistasi®) on gait deficits and postural instability in patients with PD. PubMed, Scopus, PEDro, REHABDATA, web of science, CHAINAL, EMBASE, and MEDLINE were searched from inception to July 2021. The methodological quality of the selected studies was evaluated using the Physiotherapy Evidence Database (PEDro) scale. Five studies met the eligibility criteria. The scores on the PEDro scale ranged from 3 to 8, with a median score of 8. The results showed evidence for the benefits of the proprioceptive focal stimulation (Equistasi®) on gait and postural stability in individuals with PD. Proprioceptive focal stimulation (Equistasi®) appears to be safe and well-tolerated in patients with PD. Proprioceptive focal stimulation (Equistasi®) may improve gait ability and postural stability in patients with PD. Further high-quality studies with long-term follow-ups are strongly needed to clarify the long-term effects of proprioceptive focal stimulation (Equistasi®) in patients with PD.

Effects of long-term detraining on muscle performance in young soccer players.

BACKGROUND: Long-term detraining consists of a physiological partial or total reduction of the adaptations induced by training caused by a suspension period of the training itself longer than 4 weeks. The aim of this study was to analyze a group of young soccer players by assessing the effects of long-term detraining on neuromuscular performance. METHODS: A study sample of 35 young soccer players of subelite level (age: 14.5±0.5 years) was recruited. The subjects were tested 7 days before the interruption of training for the summer break (T0), and at the end of the 7-week detraining period (T1). RESULTS: No statistically significant differences were found for BMI (P=0.283) and percentage of fat mass (P=0.273) between T0 and T1. PUSH UP (P=0.016; ES [effect size]=0.2) and SIT UP (P=0.001; ES=1.2) test values show statistically significant increase, those of CHIN UP (P=0.05; ES=-0.2), instead, a statistically significant worsening. Statistically significant but moderate differences on speed running test 30 meters (P=0.001; ES=0.3) are observed as well as trivial differences on 50 meters (P=0.001; ES=0.2), while differences on 10, 15 and 20 meters are irrelevant. As for the jump tests, values show a slight worsening (P=0.135; ES=0.2) in Squat Jump and Counter Movement Jump (P=0.153; ES=0.2) without statistical significance. CONCLUSIONS: A 7-week-long detraining period does not seem to produce any appreciable changes on neuromuscular performance of the lower limb (trained muscle) in young soccer players. As regards the analyzed age group, coaches should not focus their attention on neuromuscular efficiency maintenance exercises in the off-season period.

Whole Body Vibration: A Valid Alternative Strategy to Exercise?

Several studies agree that mechanical vibration can induce physiological changes at different levels, improving neuromuscular function through postural control strategies, muscle tuning mechanisms and tonic vibration reflexes. Whole-body vibration has also been reported to increase bone mineral density and muscle mass and strength, as well as to relieve pain and modulate proprioceptive function in patients with osteoarthritis or lower back pain. Furthermore, vibratory training was found to be an effective strategy for improving the physical performance of healthy athletes in terms of muscle strength, agility, flexibility, and vertical jump height. Notably, several benefits have also been observed at the brain level, proving to be an important factor in protecting and/or preventing the development of age-related cognitive disorders. Although research in this field is still debated, certain molecular mechanisms responsible for the response to whole-body vibration also appear to be involved in physiological adaptations to exercise, suggesting the possibility of using it as an alternative or reinforcing strategy to canonical training. Understanding these mechanisms is crucial for the development of whole body vibration protocols appropriately designed based on individual needs to optimize these effects. Therefore, we performed a narrative review of the literature, consulting the bibliographic databases MEDLINE and Google Scholar, to i) summarize the most recent scientific evidence on the effects of whole-body vibration and the molecular mechanisms proposed so far to provide a useful state of the art and ii) assess the potential of whole-body vibration as a form of passive training in place of or in association with exercise.

Rehabilitation interventions for cognitive deficits in stroke survivors: A systematic review of randomized controlled trials.

Cognitive deficits are one of the most common impairments after stroke. It negatively affects physical and social functioning. Rehabilitation interventions for cognitive deficits post-stroke have taken less consideration. The present study aimed to provide an overview of the effects of various rehabilitation interventions on cognitive functions in patients with stroke. PUBMED, SCOPUS, PEDro, EMBASE, MEDLINE, and REHABDATA were searched for randomized controlled trials (RCTs) investigating the effects of rehabilitation interventions on cognitive domains poststroke until August 2021. The methodological quality of the selected studies was evaluated using the Cochrane Collaboration tool, and the effect sizes were calculated. Forty-four studies met the inclusion criteria. A total of 3561 individuals with stroke, 57.60% of whom were males. The mean age for all participants was 65.48 years. Eighteen RCTs were high, moderate (n = 17), and low methodological quality (n = 9). The results showed evidence for the beneficial effects of many rehabilitation interventions on cognition in individuals with stroke. Rehabilitation plays a crucial role in improving cognitive functions in stroke patients with mild cognitive deficits. Virtual reality (VR), computer-based cognitive rehabilitation (CBCR), and non-aerobic exercises may promote cognitive functions in patients with stroke.

Virtual reality for balance and mobility rehabilitation following traumatic brain injury: A systematic review of randomized controlled trials.

BACKGROUND: Balance and mobility deficits are most prevalent impairments in patients with traumatic brain injury (TBI). The evidence has proposed that rehabilitation plays an important role in improving balance and mobility post-TBI. Virtual reality (VR) is a computer technology that provides immersed users to generate feedback such as visual, audio, and haptic. OBJECTIVE: This review aimed to examine the effects of the VR treatment intervention on balance and mobility in patients with TBI and to define the most effective VR treatment protocol. METHODS: SCOPUS, PEDro, PubMed, REHABDATA, EMBASE, and the web of science were searched for experimental trials examining the impacts of VR training on balance and mobility in patients with TBI from inception until July 2022. Physiotherapy Evidence Database (PEDro) scale was used to assess the methodological quality of the selected studies. RESULTS: Five randomized controlled trials (RCTs) met the inclusion criteria. The PEDro scores ranged from 6 to 8, with a median of 6. A total of 157 patients with TBI were included in this review, 31.2% of whom were females. The findings showed that VR intervention is not superior to traditional physiotherapy interventions in improving balance and mobility post- TBI. CONCLUSIONS: The preliminary findings showed that the influence of VR on the balance and mobility ability in patients with TBI is promising. Combining VR with other concurrent rehabilitation interventions may show more significant improvements in balance and mobility compared to VR interventions alone. The optimal VR treatment protocol remains unclear. Further randomized controlled trials are strongly needed.

COVID-19 as a Potential Cause of Muscle Injuries in Professional Italian Serie A Soccer Players: A Retrospective Observational Study.

The COVID-19 pandemic has shocked the entire planet. The soccer world has also suffered major upheavals, and many professional soccer players have been infected with the virus. The aim of this study was to evaluate the incidence of injuries in Italian Serie A professional soccer players before and during the COVID-19 pandemic. Methods: We evaluated the incidence of muscle injuries between four competitive seasons of the Italian Serie A (2016-2017, 2017-2018, and 2018-2019 pre-COVID-19 vs. 2020/2021 post-COVID-19) in professional soccer players. Results: Significant differences were found in muscular injuries between the post-COVID-19 season and the previous seasons (p < 0.001). The median split of the players' positivity duration was of 15 days. The players' long positivity (PLP) group showed a significant number of muscular injuries compared to the players' short positivity (PSP) group (p < 0.0014, ES = 0.81, Large). The total teams' days of positivity were significantly related to the total team number of muscular injuries (r = 0.86; CI 95% 0.66 to 0.94; p < 0.0001). In conclusion, this data showed that the competitive season post-COVID-19 lockdown has a higher incidence of muscle injuries in Italian Serie A soccer players compared to the pre-pandemic competitive season.

Whole Body Vibration Improves Brain and Musculoskeletal Health by Modulating the Expression of Tissue-Specific Markers: FNDC5 as a Key Regulator of Vibration Adaptations.

Whole body vibration (WBV) is well known to exert beneficial effects on multiple tissues, improving synaptic transmission, muscle mass, bone quality, and reducing anxiety and depressive behavior. However, the underlying molecular mechanisms are not yet fully understood, and organs and tissues may respond differently to the vibratory stimulus depending on multiple factors. Therefore, we investigated the WBV effects on the brain and musculoskeletal tissue of 4-month-old young mice, evaluating synaptic plasticity by electrophysiological recordings and tissue organization by histology and histomorphometric analysis. Specifically, WBV protocols were characterized by the same vibration frequency (45 Hz), but different in vibration exposure time (five series of 3 min for the B protocol and three series of 2 min and 30 s for the C protocol) and recovery time between two vibration sessions (1 min for the B protocol and 2 min and 30 s for the C protocol). In addition, immunohistochemistry was conducted to evaluate the expression of fibronectin type III domain-containing protein 5 (FNDC5), as well as that of tissue-specific markers, such as brain-derived neurotrophic factor (BDNF) in brain, myostatin in muscle and collagen I (COL-1) in bone. Our results suggest that the WBV effects depend closely on the type of protocol used and support the hypothesis that different organs or tissues have different susceptibility to vibration. Further studies will be needed to deepen our knowledge of physiological adaptations to vibration and develop customized WBV protocols to improve and preserve cognitive and motor functions.

Specificity of weightlifting bench exercises in kayaking sprint performance: A perspective for neuromuscular training.

Several studies showed significant differences between bench lift exercises without investigating which is more related, in biomechanical and neuromuscular terms, to improve the sprint flatwater kayak performance. This study aims to compare the power-load and velocity-load neuromuscular parameters performed in prone bench pull (PBP), and bench press (BP) exercises to identify which of them meet the gesture specificity in sprint flatwater kayak performance. Ten elite kayakers participated in this study. Power-load, velocity-load relationships, the maximum dynamic strength, and the kayak sprint performance test were assessed. The power-load and velocity-load relationships showed significant differences between the PBP and BP for each considered load. The kayakers showed a significant correlation between maximum power performed on the PBP and the maximum velocity reached in the kayak sprint (r = 0.80, p < 0.01) and the stroke frequency (r = 0.61, p < 0.05). Conversely, the maximum power performed on the BP did not correlate with the kinematic parameters analyzed. In addition, the maximum dynamic strength in the PBP and BP did not correlate with the maximum velocity and stroke frequency. Furthermore, no significant difference was observed in both the bench exercises for the maximum dynamic strength (p > 0.05). The results of this study suggest that the maximal muscular power expressed in PBP exercise only seems to be more specific in kayak velocity performance compared with maximal dynamic strength and with all dynamic parameters recorded in the BP. This will allow coaches and trainers to use specific bench exercises for specific neuromuscular kayakers' adaptations during the whole competitive season.

Relationship between aerobic fitness and metabolic power metrics in elite male soccer players.

The aim was to assess the relationship between aerobic fitness and metabolic power metrics in elite male soccer players, and the possible differences that playing positions might impose during match play over new metabolic power metrics. Sixty-two elite professional male soccer players (13 central backs, 13 side backs, 22 midfielders, and 14 forwards) took part in the study. Players were monitored during eleven months of full training (including pre-season and in-season) and over all official matches (Serie A matches, Italy Cup matches). Aerobic fitness tests were conducted one week after the start of the preseason, and 8, 24 and 36 weeks after the beginning of the Championship. Players' aerobic fitness and metabolic power metrics were considered as the mean of all seasonal testing and of pooling data of 38 championship matches and 3 or 6 Italy Cup matches for all the calculations respectively. The velocity at 4 mmol·L-1 (VL4) was significantly related to metabolic power metrics match variables with correlation ranging from trivial to very large (r = 0.32 to r = 0.89). Receiver-operating-characteristic (ROC) analysis showed that speed at VL4 was sensitive in detecting high metabolic power distance (HMPD) changes in all but central back players as revealed by area under the curve (central back .78, 95%CI .47 to .95; full back .93, 95%CI .64 to 0.99; midfielder .88, 95%CI .67 to 0.98; forward .90, 95%CI .62 to 0.99). This study's findings provide further evidence for the ecological validity of aerobic fitness in elite male soccer players. Players having a HMPD cut-off equal to or higher than > 1450 m for central backs, > 1990 m for full backs, > 2170 m for midfielders and > 1670 m for forwards may be considered as possessing superior aerobic fitness status. In light of this study's findings, the VL4 test may be considered a valid test to evaluate meaningful information for direct generic aerobic training in soccer players.

Paddle propulsive force and power balance: a new approach to performance assessment in flatwater kayaking.

This study aims to determine the propulsive force (Fp) and its timing of application during the paddle stroke confirming the dynamic balance between propulsive and drag powers (Pp = Pd) in kayaking performance. Ten male sub-elite paddlers participated in the study. The athletes carried out three trials of 50 m at three different velocity ranges: 2.70 - 3.00 m/ s; 3.01 - 3.50 m/s and 3.51 - 4.00 m/ s. A constant velocity during each trial was maintained and the section between 15 and 40 m of the total pool length was considered for further analysis. Data were collected using the E-kayak system provided of an instrumented paddle and 2D video analysis. It was observed that the propulsive force increases in intensity (up to 90% of the peak force) as the velocity increases. The dynamic balance between Pd and Pp was confirmed with a Bland and Altman plot (estimated bias: 0.2; LoA: 12.8 and 13.3 W). The related comparisons between the power parameters showed no significant difference (p > 0.050) in each of the considered velocity. By applying the dynamic balance theory between Pp = Pd on the data obtained from the interaction among GPS, force on the paddle and 2D video analysis, it is possible to acquire essential information (Fp, Pp) to monitor the flatwater kayaking performance.