The Validity and Reliability of Global Positioning System Units for Measuring Distance and Velocity During Linear and Team Sport Simulated Movements

Locomotor and Physiological Demands of Small-Sided Soccer Games in Wildcard and Regular Players: Effects of Goalkeepers and Type of Wildcard

BACKGROUND

Small-sided games (SSGs) are frequent training drills in soccer. This study investigated whether type of game (ie, with/without goalkeepers) and wildcard ( without vs internal vs external wildcard) impact the physiological (heartrate [HR]) and locomotor (total distance [TD] covered) demands in regular and wildcard players and to evaluate between-player and within-player variability.

HYPOTHESIS

Demands are influenced by wildcard and game type, with higher demand (distance covered at high intensities and sprint speed) in regular players and with higher variability in SSG with wildcard players.

STUDY DESIGN

Descriptive/comparative study.

LEVEL OF EVIDENCE

Level 4.

METHODS

Twenty-four soccer players completed 6 SSG as 3 versus 3 without (NG) or with (GK) goalkeepers, and with internal (NG+IW and GK+IW) and external (NG+EW and GK+EW) wildcard. Average HR (HRavg), rate of perceived exertion, and locomotor demands (TD, medium [MID = 7.0-13.9 km h-1], high [HID = 14.0-20.9 km h-1] and sprint [SPD >21.0 km h-1] distance and peak speed [PS]) were registered.

RESULTS

The inclusion of GK and internal wildcard led to decreased HRavg and TD in regular players. Wildcard players positioned internally exhibited higher TD, PS, and lower HRavg than externally positioned wildcards. Regular players demonstrated higher TD, PS, MID, HID, HRavg and time spent in Z3 (>90% HRmax) compared with wildcard players in SSG played with external wildcard. Regular and wildcard players displayed great between- and within-player variability in high-intensity metrics.

CONCLUSION

Specific game type and wildcard inclusion impact the physiological and locomotor demands in SSG, with variations observed between regular and wildcard players.

CLINICAL RELEVANCE

This study provides comprehensive information on the physiological and locomotor demands of SSG depending on the inclusion and position of goalkeepers and wildcards, which can be useful for strength and conditioning coaches when designing specific training tasks, individualizing training load and applying return-to-play programs.

Validity and Sensitivity of a Submaximal Fitness Test for Assessing Cardiorespiratory Fitness and Response to Preseason Training Load in Female Football Players

PURPOSE

To evaluate the within-athlete sensitivity, validity, and dose-response relationships of exercise heart rate (HRex) from a submaximal fitness test (SMFT) as a proxy measure of cardiorespiratory fitness.

METHODS

This study follows an observational, repeated-measures design. Twenty-five trained female football players' training loads (GPS and HR metrics) were collected throughout an 8-week preseason period. A 4-minute continuous-fixed SMFT protocol was administered weekly to evaluate HRex. A running time-trial assessment was conducted in weeks 2 and 8 to calculate mean velocity (5-min-30-s time-trial mean velocity) as a proxy measure of cardiorespiratory fitness. SMFT HRex measurement properties were determined via within- and between-athletes correlations and linear mixed models.

RESULTS

The overall preseason change in SMFT HRex derived from weekly repeated measures was -4.7% points (90% CIs, -3.9 to -5.6). The association between SMFT HRex and 5-minute-30-second time-trial mean velocity changes was large (-0.55), with 90% CIs ranging from negative moderate to negative very large magnitudes (-0.31 to -0.71). A 1% point decrease in SMFT HRex corresponded to an increase in 5-minute-30-second time-trial mean velocity of 0.13 (90% CIs, 0.03-0.24) km·h-1. Within-athlete correlations between training loads and SMFT HRex demonstrated moderate inverse relationships with external-load parameters (-0.39 to -0.47) and small inverse relationships with HR-based internal metrics (-0.25 to -0.29). Accumulated high- and very high-speed running throughout the entire preseason showed consistent inverse dose-response relationships with SMFT HRex (moderate and large, respectively), while all other load measures displayed unclear associations.

CONCLUSIONS

SMFT HRex is a sensitive and valid tool to evaluate preseason cardiorespiratory-fitness changes in female football players.

Repeatability of Vertical Ground Reaction Force Estimation During Running on the Athletics Track on 3 Different Days

To increase understanding in development of running injuries, the biomechanical load over time should be studied. Ground reaction force (GRF) is an important parameter for biomechanical analyses and is typically measured in a controlled lab environment. GRF can be estimated outdoors, however, the repeatability of this estimation is unknown. Repeatability is a crucial aspect if a measurement is repeated over prolonged periods of time. This study investigates the repeatability of a GRF estimation algorithm using inertial measurement units during outdoor running. Twelve well-trained participants completed 3 running sessions on different days, on an athletics track, instrumented with inertial measurement units on the lower legs and pelvis. Vertical accelerations were used to estimate the GRF. The goal was to assess the algorithm's repeatability across 3 sessions in a real-world setting, aiming to bridge the gap between laboratory and outdoor measurements. Results showed a good level of repeatability, with an intraclass correlation coefficient (2, k) of .86 for peak GRF, root mean square error of .08 times body weight (3.5%) and Pearson correlation coefficients exceeding .99 between the days. This is the first study looking into the day-to-day repeatability of the estimation of GRF, showing the potential to use this algorithm daily.

Physical Performance Changes in Season are Associated with GPS Data in Soccer Players

This study investigated the associations between pre-season and in-season performance with external workload in professional soccer players. Twenty-one players completed hamstring strength, countermovement jump (CMJ), 20-m sprint, and Yo-Yo intermittent recovery tests before (pre-season) and after 8 weeks (in-season). External workload (total distance, high-intensity running distance, number of sprints, and power plays) was quantified during this period, and used to divide the average above and below subgroups outcome by outcome for further analyses. Significance was accepted when P≤0.05. Hamstring strength declined from pre- to in-season [- 6%; p=0.014; effect size (ES): - 0.41], while Yo-Yo performance improved (46%; p=0.001; ES: 1.31). When divided by high-intensity running distance, only the below-average subgroup improved CMJ performance (5%; p=0.030). For minutes played, the above-average subgroup improved Yo-Yo performance (41%; p<0.001), but not the below-average subgroup. Furthermore, playing time correlated with improved Yo-Yo performance (p=0.040; r=0.534). Improved 20-m sprint performance associated with more sprints performed (p=0.045; r=- 0.453). Physical capabilities changed over a competitive season and were related to, and differentiated by, external workload. Because hamstring strength decreased and CMJ only improved in players exposed to less high-intensity external load, practitioners should individualize approaches to counteract these conditions when high external workload is performed over the season.

Cardiovascular Response and Locomotor Demands of Elite Basketball Referees During International Tournament: A Within- and Between-Referee Analysis

There is little knowledge about within- and between-referee variation (WBRV) in cardiovascular responses (CVR) and locomotor game demands (LMD). Thus, the primary aim of this study was to assess the WBRV of CVR and LMD in male basketball referees during elite international games in preparation [e.g., warm-up (WU) and re-warm-up (R-WU)] and active game phases. The secondary aim was to explore quarter-by-quarter differences in CVR and LMD. Thirty-five international male referees took part in this study (age, 40.4 ± 5.4 years; body height, 184.9 ± 5.7 cm; body weight, 85.1 ± 7.5 kg; BMI, 24.0 ± 1.7 kg × m-2; fat%, 18.8 ± 4.7% and VO2max, 50.4 ± 2.2 L × kg-1 × min-1. In total, 76 games (e.g., 228 officiating cases) were analyzed during the FIBA elite men's competition. They officiated 4.5 games on average (range 3-9 games). Each referee used the Polar Team Pro system to measure CVR [e.g., heart rate (HR), time spent in different HR intensity categories] and LMD (e.g., distance covered, maximal and average velocity, and number of accelerations). Results showed that the referees had bigger WBRV during the active and preparation (e.g., W-U than R-WU) phase when variables of higher CVR and LMD intensity were observed (e.g., time spent at higher HR zones, distance covered in higher speed zones). The WBRV, CVR, and LMD were higher during WU than R-WU. Moreover, the referees had a lower CVR and LMD in the second half. In conclusion, the referees should establish and follow consistently a game-to-game preparation routine and attempt to spread their on-court preparation time equally within the crew. A half-time preparation routine should be improved to re-establish a sufficient activation level similar to that achieved in pre-game preparation.

Changes in female football players' in-season training load, intensity and physical performance: training progression matters more than accumulated load

Introduction

This observational study investigated: (1) potential changes in female football players' in-season training load, intensity and physical performance, and (2) if in-season accumulated training load, intensity, or their progression are associated to changes in physical performance.

Methods

Thirty-five national level female players (∼21 years, n = 35) from three top-teams of the Finnish national league participated. Players performed tests at the beginning and at the end of the 27-week in-season. Tests were: 30-m sprint, countermovement jump (CMJ) and 1,200-m shuttle run, used to calculate maximal aerobic speed (MAS). Players' external and internal training load and intensity were monitored in all on-field training sessions and official matches (3,941 data samples) using Polar Team Pro system.

Results

Training load decreased towards the end of the in-season (p < 0.05), but intensity remained stable. No changes in physical performance test results occurred from before to after in-season tests at a group level. Change of CMJ correlated negatively with accumulated training load, intensity and progression of total distance (TD) and low-intensity running distance (LIRD) (r = -0.398 to -0.599, p < 0.05). Instead, development of MAS correlated positively with progression of TD and LIRD intensities (r = 0.594 and 0.503, p < 0.05). Development of both CMJ and MAS correlated positively with intensity progression of very-high-intensity running distance (VHIRD) and number of accelerations and decelerations (r = 0.454-0.588, p < 0.05).

Discussion

Reduced training load over the in-season is not detrimental for players' physical performance when training intensity progressively increases. Intensity progression of VHIRD, moderate- and high-intensity accelerations and decelerations are indicators of both MAS and CMJ development, respectively.

Cross-Country Ski Skating Style Sub-Technique Detection and Skiing Characteristic Analysis on Snow Using High-Precision GNSS

A comprehensive analysis of cross-country skiing races is a pivotal step in establishing effective training objectives and tactical strategies. This study aimed to develop a method of classifying sub-techniques and analyzing skiing characteristics during cross-country skiing skating style timed races on snow using high-precision kinematic GNSS devices. The study involved attaching GNSS devices to the heads of two athletes during skating style timed races on cross-country ski courses. These devices provided precise positional data and recorded vertical and horizontal head movements and velocity over ground (VOG). Based on these data, sub-techniques were classified by defining waveform patterns for G2, G3, G4, and G6P (G6 with poling action). The validity of the classification was verified by comparing the GNSS data with video analysis, a process that yielded classification accuracies ranging from 95.0% to 98.8% for G2, G3, G4, and G6P. Notably, G4 emerged as the fastest technique, with sub-technique selection varying among skiers and being influenced by skiing velocity and course inclination. The study's findings have practical implications for athletes and coaches as they demonstrate that high-precision kinematic GNSS devices can accurately classify sub-techniques and detect skiing characteristics during skating style cross-country skiing races, thereby providing valuable insights for training and strategy development.

A Review of the Validity and Reliability of Accelerometer-Based Metrics From Upper Back-Mounted GNSS Player Tracking Systems for Athlete Training Load Monitoring

ABSTRACT

Dawson, L, Beato, M, Devereux, G, and McErlain-Naylor, SA. A review of the validity and reliability of accelerometer-based metrics from upper back-mounted GNSS player tracking systems for athlete training load monitoring. J Strength Cond Res 38(8): e459-e474, 2024-Athlete load monitoring using upper back-mounted global navigation satellite system (GNSS) player tracking is common within many team sports. However, accelerometer-based load monitoring may provide information that cannot be achieved with GNSS alone. This review focuses on the accelerometer-based metrics quantifying the accumulation of accelerations as an estimation of athlete training load, appraising the validity and reliability of accelerometer use in upper back-mounted GNSS player tracking systems, the accelerometer-based metrics, and their potential for application within athlete monitoring. Reliability of GNSS-housed accelerometers and accelerometer-based metrics are dependent on the equipment model, signal processing methods, and the activity being monitored. Furthermore, GNSS unit placement on the upper back may be suboptimal for accelerometer-based estimation of mechanical load. Because there are currently no feasible gold standard comparisons for field-based whole-body biomechanical load, the validity of accelerometer-based load metrics has largely been considered in relation to other measures of training load and exercise intensity. In terms of convergent validity, accelerometer-based metrics (e.g., PlayerLoad, Dynamic Stress Load, Body Load) have correlated, albeit with varying magnitudes and certainty, with measures of internal physiological load, exercise intensity, total distance, collisions and impacts, fatigue, and injury risk and incidence. Currently, comparisons of these metrics should not be made between athletes because of mass or technique differences or between manufacturers because of processing variations. Notable areas for further study include the associations between accelerometer-based metrics and other parts of biomechanical load-adaptation pathways of interest, such as internal biomechanical loads or methods of manipulating these metrics through effective training design.

Absence of Monotony and Strain Effects on Referees' Physical Performance During International Basketball Federation World Cup Basketball Competition

PURPOSE

The study aimed to conduct a comparative analysis of physical performance indicators and assess the levels of performance monotony and strain experienced by basketball referees.

METHODS

The study involved the participation of 12 basketball referees (mean age: 40.0 [4.9] y) affiliated with the International Basketball Federation. The investigation was carried out throughout 2 density tournaments, wherein the maximum heart rate, average heart rate, performance monotony, and performance strain were documented for 3 variables.

RESULTS

The findings indicated significant variations in the mean heart rate, maximum heart rate, total distance monotony, total distance strain, the total number of sprints monotony, the total number of sprints strain, calories monotony, and calories strain (P < .05). Decreasing the density of elite-level basketball competitions has been observed to reduce the monotony and strain experienced by referees. However, this action does not increase motion distance or speed zones.

CONCLUSIONS

The environmental stressors experienced by senior-level athletes (World Cup) differ from those encountered by younger athletes (World Cup Under 19). Further investigation is required to ascertain the potential effects of competition monotony and strain on decision-making processes and the overall quality of refereeing.

Wearable Sensors and the Evaluation of Physiological Performance in Elite Field Hockey Players

Sports performance tracking has gained a lot of interest and widespread use in recent years, especially in elite and sub-elite sports. This makes it possible to improve the effectiveness of training, to calibrate and balance workloads according to real energy expenditure, and to reduce the likelihood of injuries due to excessive physical stress. In this context, the aim of this review was to map the scientific literature on wearable devices used in field hockey, evaluating their characteristics and the available evidence on their validity in measuring physiological and movement parameters. A systematic investigation was carried out by employing five electronic databases and search terms that incorporated field hockey, wearables, and performance analysis. Two independent reviewers conducted assessments of the 3401 titles and abstracts for inclusion, and at the end of the screening process, 102 full texts were analyzed. Lastly, a total of 23 research articles that specifically concentrated on field hockey were incorporated. The selected papers dealt with performance monitoring (6 papers), technical analysis and strategy game (6), injury prevention (1), and physiological measurements (10). To appraise the quality of the evaluations, the Oxford quality scoring system scale was employed. The extraction of information was carried out through the utilization of the participants, intervention, comparison, and outcomes (PICOS) format. The analysis encompassed research studies that implemented wearable devices during training and competitive events. Among elite field hockey competitions, GPS units were identified as the predominant wearable, followed by heart rate monitors. The intraclass correlation coefficient (ICC) related to wearable devices showed reasonably high between-trial ICCs ranging from 0.77 to 0.99. The utilization of wearable devices in field hockey primarily centers around the measurement of player activity profiles and physiological demands. The presence of discrepancies in sampling rates and performance bands makes it arduous to draw comparisons between studies. Nevertheless, this analysis attested to the fact that wearable devices are being employed for diverse applications in the realm of field hockey.

External training load and performance recovery after small-sided games in soccer: Insights for return-to-play management

The return-to-play process' characteristics can vary by injury and sport type but are typically composed of phases of different durations, training targets, and intensities that gradually increase the physiological and mechanical load. In team sports, contact drills are a necessary part of the last phases of this process, and they should be planned using the optimal mechanical load. The present study investigated the external load and kinetic recovery in U19 soccer players performing 6vs6 and 3vs3 small-sided games. A global positioning system (GPS) measured external load metrics. The rate of perceived exertion (RPE) was registered at the end. Total quality of recovery (TQR) was collected at the beginning of the training session and after 24 h. Moreover, before and after the small-sided games (SSGs) and at 24 h, delayed-onset muscle soreness (DOMS) of the legs, sprinting time, and vertical jump height (CMJ) were collected. 6vs6 presented higher values in total distance low-, moderate-, high, and very-high-speed distance, and maximum speed (p < 0.05). However, 3vs3 showed higher number of sprints, acceleration, and deceleration at different intensities. Furthermore, no difference was shown in RPE. The effect of fatigue on sprint seems greater for 6vs6, showing an impairment persistent at 24 h (p < 0.05). Moreover, CMJ height was impaired after 6vs6 and at 24 h (p < 0.05) but did not change after 3vs3 (p > 0.05). DOMS values after SSGs and at 24 h were higher than baseline for both conditions (p < 0.05), while TQR decreased at 24 h in both conditions (p < 0.05). Based on our results, it seems that 6vs6, leading to a greater high-speed running distance, might cause a training load that needs more time to recover. This point may be crucial in a return-to-play process, especially when hamstring muscles are involved.

A Systematic Review and Meta-Analysis of Wearable Satellite System Technology for Linear Sprint Profiling: Technological Innovations and Practical Applications

ABSTRACT

Cormier, P, Meylan, C, Agar-Newman, D, Geneau, D, Epp-Stobbe, A, Lenetsky, S, and Klimstra, M. A systematic review and meta-analysis of wearable satellite system technology for linear sprint profiling: technological innovations and practical applications. J Strength Cond Res 38(2): 405-418, 2024-An emerging and promising practice is the use of global navigation satellite system (GNSS) technology to profile team-sports athletes in training and competition. Therefore, the purpose of this narrative systematic review with meta-analysis was to evaluate the literature regarding satellite system sensor usage for sprint modeling and to consolidate the findings to evaluate its validity and reliability. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, an electronic search of the databases, PubMed and SPORTDiscus (EBSCO), was conducted. Concurrent validity and reliability studies were considered, and 16 studies were retained for the review from the initial 1,485 studies identified. The effects on outcomes were expressed as standardized mean differences (SMDs, Cohen's d ) for each outcome (i.e., maximal sprint speed [MSS], the acceleration constant [τ], maximal theoretical velocity [ V0 ], relative force [ F0 ], and relative power [P max ]). Effect magnitudes represented the SMD between GNSS-derived and criterion-derived (i.e., radar and laser) and resulted in the following estimates: small for MSS ( d = 0.22, 95% CI 0.01 to 0.42), τ ( d = -0.18, 95% CI -0.60 to 0.23), V0 ( d = 0.14, 95% CI -0.08 to 0.36), relative F0 ( d = 0.15, 95% CI -0.25 to 0.55), and relative P max ( d = 0.21, 95% CI -0.16 to 0.58). No publication bias was identified in meta-analyzed studies and moderator analysis revealed that several factors (sampling rate and sensor manufacturer) influenced the results. Heterogeneity between studies was considered moderate to high. This highlighted the differences between studies in sensor technology differences (i.e., sampling rate, sensor fusion, and satellite network acquisition), processing techniques, criterion technology used, sprint protocols, outcome reporting, and athlete characteristics. These findings may be useful in guiding improvements in sprint modeling using GNSS technology and enable more direct comparisons in future research. Implementation of all-out linear sprint efforts with GNSS technology can be integrated into sport-specific sessions for sprint modeling when robust and consistent data processing protocols are performed, which has important implications for fatigue monitoring, program design, systematic testing, and rehabilitation in individual and team sports.

Average demands and most demanding passages of national-level female soccer matches: do small- and large-sided games replicate match demands?

Introduction

This study aims to (1) determine the average and most demanding passage (MDP) load of national-level female soccer matches and (2) evaluate the relationship between average and MDP load during small-sided games (SSGs), large-sided games (LSGs), and matches.

Methods

A total of 37 national-level female soccer players from a single club senior team and the U18 team participated. The average and 1-, 3-, and 5-min MDP external (total, high-speed, and very-high-speed running distances, acceleration and deceleration distances, average metabolic power, and high-metabolic load distance) and internal loads (average heart rate, rate of perceived exertion) of the 29 league matches, ten 4 vs. 4 + goalkeepers SSGs, and six 8 vs. 8 + goalkeepers LSGs were analyzed by the Polar Team Pro player tracking system.

Results

In matches, the external load variables during 1-, 3-, and 5-min MDPs were 167%-1,165%, 135%-504%, and 126%-359%, of match average values, respectively. In LSGs, all external load variables reached higher average values compared with those during matches, except for the very-high-speed running distance; however, no variable reached higher values of 1-min MDP compared with those during the matches. In SSGs, the average acceleration and deceleration distances were higher compared with those during the matches.

Discussion

The findings from the present study suggest that LSGs and SSGs can be used to overload the average values of the selected external load variables compared with those during the matches; however, other training options must be explored to overload 1-min match MDPs.

Validity and Reliability of Polar Team Pro and Playermaker for Estimating Running Distance and Speed in Indoor and Outdoor Conditions

Although global positioning systems and inertial measurement unit systems are often used to quantify physical variables in training, both types of systems need to be compared, considering their frequent use in measuring physical loads. Thus, the purpose of our study was to test the reliability and validity of speed and distance run measurements at different intensities in indoor and outdoor conditions made by Polar Team Pro and Playermaker. Four participants (age = 30.0 ± 5.1 years, body mass = 76.3 ± 5.3 kg, height = 1.79 ± 0.09 m), each wearing three Polar Team Pro and two Playermaker sensors, performed 100 m runs with different prescribed intensities (i.e., criterion measure) varying from 8 to 24 km h-1, in a straight line and/or rectangle under indoor and outdoor conditions. Both systems underestimated total distance; Playermaker underestimated speed, the extent of which increased as speed increased, while Polar Team Pro overestimated mean speed at 8 km h-1 for the straight-line condition. No differences emerged in mean speed estimated by Polar Team Pro at any intensities other than 20 km h-1, which was underestimated by 2%. The reliability of the sensors was good, given a coefficient of variation (CV) of <2% for all conditions except when measuring indoor conditions with Polar Team Pro (CV ≈ 10%). Intraclass correlations (ICCs) for consistency within the sensors varied from 0.47 to 0.99, and significantly lower ICCs were documented at 8, 10, and 12 km h-1. Both systems underestimated distance measured in indoor and outdoor conditions, and distance validity in different intensities seemed to worsen as speeds increased. Although Polar Team Pro demonstrated poor validity and reliability in indoor conditions, both systems exhibited good reliability between their sensors in outdoor conditions, whereas the reliability within their sensors varied with different speeds.

Reliability and validity of Polar Team Pro measurements in running at different velocities in an indoor setting

The purpose of this study was to test the reliability and validity of Polar Team Pro measurements of velocity, acceleration, and distance covered in a rectangular run at different intensities in an indoor setting. In two test sessions, 10 women (age 15.7 ± 0.4 years, body mass 61.3 ± 5.3 kg, body height 1.69 ± 0.07 m) performed 100 m runs at different intensities, ranging from 8 to 18 km/h. The 100 m runs were performed on a rectangular track at an indoor handball facility. The main finding revealed that Polar Team Pro underestimated the running distance and velocity (10%-15% at 10 km/h), especially at higher speeds (15% and 6% at 15 and 18 km/h, respectively). Between test days, coefficients of variance varied from 4.2% to 12.4%, when measuring at different speeds. However, a significant difference was found for the two runs only at 15 km/h between the two test days. It was concluded that Polar Team Pro underestimated the running distance and velocity when measuring a rectangular run at different speeds in an indoor setting, especially at higher speeds. This underestimation is probably caused by the inaccuracy of the inertial measurement unit algorithm that calculates the distance, as body height influences the distance and velocity measurements. The variability between the different units is, thereby, also influenced, causing variable coefficients of variance between the sensors. Test-retest variability was acceptable. Based on the findings of this study, practitioners should be cautious when measuring speed and distance using Polar Team Pro Sensors in indoor settings, as these measurements are underestimated with increasing speed.

Comparison of the neuromuscular response to three different Turkish, semi-professional football training sessions typically used within the tactical periodization training model

This study examined the neuromuscular responses to three typical football (soccer) training sessions and the reliability of peak speed (PS) measured during a submaximal running test (SRT) for identifying neuromuscular fatigue (NMF) status. Jump height (CMJ_H) and peak velocity (CMJ_PV) were collected from a CMJ test, while peak speed (PS) was collected during an SRT before and after each training session. Large effect size (ES) decreases were observed in each variable post-training (ES; - 1.42 to - 2.32). Significant differences (> 0.001) were detected between each football session's external load variables. Coefficients of variations were small (< 10%) with moderate (CMJ_PV; 0.53, PS; 0.44) and strong (CMJ_H; 0.72) intraclass correlation coefficients between pre-test measures. The demands of each football session aligned with the principles of tactical periodization and were sufficient to produce the fatigue necessary to elicit physiological adaptations. PS was also shown to be a viable measure of monitoring NMF status.

Influence of Scoring Systems on Mental Fatigue, Physical Demands, and Tactical Behavior during Soccer Large-Sided Games

Constraints are common in soccer training to develop physical, technical-tactical, and mental training concurrently. This study examined how different scoring systems influence physical, tactical, and mental demands during large-sided games in soccer. Eighteen youth-elite male (17.39 ± 1.04 y) soccer players completed three 8 vs. 8 large-sided games where the different score systems were i) official score system (OSS; i.e., 1 goal = 1 goal), ii) double the value of the goal-4 min (DVx4; i.e., 1 goal = 1 goal from 0.00 to 7.59 min, and 1 goal = 2 goals from 8.00 to 12.00 min), and iii) double the value of the goal-8 min (DVx8; i.e., 1 goal = 1 goal from 0.00 to 3.59 min, and 1 goal = 2 goals from 4.00 to 12.00 min). Physical demands and tactical behaviors were recorded during tasks using a global positioning system and video camera. Mental fatigue was recorded pre- and post-task using a visual analogue scale. Also, the ratio of perceived exertion and mental load were recorded after tasks were finished. Results reported the highest values of mental and physical demands in DVx4. Mental fatigue increased during all three large-sided games, although this increase was significantly higher in DVx4 compared with OSS (p = 0.006) and DVx8 (p = 0.027). Tactical behavior showed a trend towards more direct play during DVx4, which was less observed during DVx8, and not at all during OSS. In conclusion, changing the scoring system affects physical, tactical, and mental demands.

Profiling the Typical Training Load of a Law Enforcement Recruit Class

Law enforcement academies, designed to prepare recruits for their prospective career, represent periods of high physical and mental stress, potentially contributing to recruits' injuries. Managing stress via monitoring training loads may mitigate injuries while ensuring adequate preparation. However, it is vital to first understand an academy's typical training load. The aim of this study was to profile the typical training load of law enforcement recruits over the course of 22 weeks. Data were prospectively collected using global positioning system (GPS) units placed on recruits during a portion of the academy training, while a desktop analysis was retrospectively applied to six other classes. A Bland-Altman plot was conducted to assess the agreement between the two methods. A linear mixed model was conducted to analyse the difference in distances covered per week, while other variables were presented graphically. Adequate agreement between the desktop analysis and GPS units was observed. Significant differences (p-value < 0.01) in distance covered (9.64 to 11.65 km) exist between weeks during early academy stages, which coincide with increases (~6 h) in physical training. Significant decreases in distances were experienced during the last five weeks of academy training. Most acute:chronic workload ratios stayed between the proposed 0.8 to 1.3 optimal range. Results from this study indicate that large increases in training occur early in the academy, potentially influencing injuries. Utilizing a desktop analysis is a pragmatic and reliable approach for instructors to measure load.

VALIDATION AND RELIABILITY BETWEEN EXTERNAL LOAD ANALYSIS DEVICES FOR SOCCER PLAYERS

ABSTRACT Objective: To test the reliability between two instruments with different analysis mechanisms, either by GPS (model GPSPORTS®) or by video analysis (InStat For Players®), relating the results of total distance covered and distance at high speed ≥ 20km/h (Very High-Intensity Running Distance, VHIR) during official soccer matches. Study Design: This is a methodological study. Data from 35 male professional soccer athletes from all tactical positions were included. Age 29.2 (± 4.8 years) and body fat 9.9 (± 1.7%), excluding goalkeepers (102 individual analyzes) were collected in official matches. In the data analysis, descriptive statistics procedures were used to characterize the sample and the intraclass correlation coefficient (ICC) was used to verify the agreement on the stability and internal consistency of the tests with 95% confidence intervals (CI). Results: The ICC in the case of the total distance traveled variable was significant 0,914 (0,876; 0,941) and indicated a very high agreement, with the linear correlation coefficient indicating a strong positive correlation (p <0.001). The ICC for the VHIR variable was not significant, although the linear correlation coefficient indicates a strong positive correlation (p <0.001). Clinical Relevance Statment: This study reveals that there is good agreement in the comparison of two systems designed to analyze the movement demands of each professional soccer athlete in relation to the total distance covered. Level of Evidence I; Methodological Study - Investigation of a diagnostic test.

Psychological and Physiological Changes in Response to the Cumulative Demands of a Women's Division I Collegiate Soccer Season

ABSTRACT

McFadden, BA, Walker, AJ, Bozzini, BN, Hofacker, M, Russell, M, and Arent, SM. Psychological and physiological changes in response to the cumulative demands of a women's division I collegiate soccer season. J Strength Cond Res 36(5): 1373-1382, 2022-This study sought to determine the effects of a women's collegiate soccer season on psychological markers, biomarkers, sleep, and performance. Athletes participated in maximal countermovement vertical jump height (CMJ) assessments and biomarker monitoring in conjunction with subjective measures of psychological wellness and sleep questionnaires before preseason (S1) and every 4 weeks following (S2, S3, and S4). Training was monitored during practices and games using global positioning satellite systems and heart rate technology. Total training load was highest from S1 to S2, decreased from S2 to S3 (effect size [ES] = -2.5; p < 0.001), and remained stable from S3 to S4. CMJ declined at S2 (ES1-2 = -0.51; p = 0.001) and returned to baseline at S3. Increases from S1 to S2 were seen for creatine kinase (ES1-2 = 1.74), free testosterone (ES1-2 = 1.27), total testosterone (ES1-2 = 3.5), and free cortisol (ES1-2 = 0.88) (p < 0.03) before returning to baseline by S3 and S4 (free cortisol). Total cortisol was elevated throughout the season before declining at S4 (ES1-4 = -0.41; p = 0.03). Iron declined from S1 to S2 (ES1-2 = -0.73; p = 0.01) and returned to baseline values at S4, whereas growth hormone declined at S2 (ES1-2 = -0.50; p = 0.01) and remained depressed. Interleukin-6 increased at S4 (ES1-4 = 0.71; p = 0.02). Total training distress decreased from S1 to S2 (ES1-2 = -0.38; p = 0.02), returned to baseline by S3, and increased by S4 (ES1-4 = 0.57; p = 0.01). No changes were observed in markers of sleep (p > 0.05). Biomarkers showed notable changes after the highest workload period (S1-S2), which coincided with CMJ decrements. Biomarker perturbations preceded declines in subjective psychological wellness (S4) which occurred in the latter half of the season, indicating an accumulation of fatigue as the season progressed.

Examining Internal and External Physical Workloads Between Training and Competitive Matches Within Collegiate Division I Men's Soccer

ABSTRACT

Anderson, T, Adams, WM, Martin, KJ, and Wideman, L. Examining internal and external physical workloads between training and competitive matches within collegiate Division I men's soccer. J Strength Cond Res 35(12): 3440-3447, 2021-A direct analysis comparing differences in the demands of competition relative to in-season training in Division I collegiate soccer players has yet to be reported. Thus, the primary purpose of this study was to compare the absolute and relative internal and external workloads measured during training with competitive matches. Twenty-six male college soccer players were monitored over 2 consecutive seasons using a GPS and heart rate (HR) telemetry system. Differences between outdoor training sessions and competitive matches were analyzed for internal and external absolute and relative training workloads. Differences in training workloads between the 3 days before a match were also analyzed. Absolute time in HR zone 4 (80-89% of HRmax) and 5 (90-100% of HRmax); accelerations in zone 1 (0.50-0.99 m·s-2), zone 2 (1.00-1.99 m·s-2), and zone 3 (2.00-2.99 m·s-2); all negative acceleration zones; training load; and estimated energy expenditure were greater in competition than training (p < 0.05). By contrast, when comparing training and competition values using metrics relative to session duration, relative workload in trainings were greater than competition for HR zone 1 (50-59% of HRmax), zone 2 (60-69% of HRmax), zone 3 (70-79% of HRmax), and zone 4 (80-89% of HRmax) and all acceleration and negative acceleration zones. In addition, absolute training workloads were generally greatest 3 days prior (p < 0.01), but not different 2 days before the competitive match. Absolute physical workloads of competition are significantly greater than those achieved during training; however, these differences and impact on the physical condition of players are mitigated by the greater relative workloads achieved during training. These results provide meaningful metrics that may lead to insights into proper conditioning and in-season workload management for Division I collegiate soccer programs.

Peak running speed can be used to monitor neuromuscular fatigue from a standardized running test in team sport athletes

This study compared the sensitivity of peak running speed (PRS) measured during a submaximal run test (SRT) with a countermovement jump (CMJ) test to provide an alternate method of measuring neuromuscular fatigue (NMF). The study involved 20 semi-professional academy soccer players who performed a SRT and CMJ test, 24-hours pre-match, 24-, 48-, 72- and 96-hours post-match. Moderate decreases (effect-size (ES) ± 90% confidence intervals) were observed 24-hours post-match for CMJ_H; ES -0.70 ± 0.19, CMJ_PV; ES -0.92 ± 0.27 and PRS; ES -0.58 ± 0.11 with small decreases in CMJ_H; ES -0.36 ± 0.13 and PRS; ES -0.27 ± 0.23 still evident 48-hours post-match before returning to baseline 72-hours post-match. The results confirm PRS as an inexpensive alternate method of measuring NMF which, allows instantaneous real-time feedback on NMF. This can allow changes to be made immediately on-field within the post-match recovery phase without the need for further analysis or equipment.

Evaluation of Performance Characteristics and Internal and External Training Loads in Female Collegiate Beach Volleyball Players

ABSTRACT

Bozzini, BN, McFadden, BA, Scruggs, SK, and Arent, SM. Evaluation of performance characteristics and internal and external training loads in female collegiate beach volleyball players. J Strength Cond Res 35(6): 1559-1567, 2021-Although women's beach volleyball is the fastest growing collegiate sport, the training demands and performance characteristics have yet to be determined. The purpose of this study was to evaluate internal and external training loads throughout a competitive season and to quantify the performance characteristics of National Collegiate Athletic Association Division I women's beach volleyball players. Female beach volleyball players (N = 20) were monitored throughout the 6-week competitive season (T1-T6) using integrative global positioning systems (GPS) and heart rate (HR)-monitoring technology, which was individualized based on preseason testing, for the determination of workload metrics. In addition to team data, all variables were analyzed between travel (n = 11, regular match participation) and non-travel (n = 7) squad athletes (p < 0.05). Team performance metrics demonstrated the explosive power emphasis of the sport, with travel squad players exhibiting significantly greater vertical jump and jump velocity abilities than their non-travel counterparts (p < 0.05). Although few time main effects from T1 to T6 were observed for team workload metrics, follow-ups revealed significant time × group interactions for training load (TL), exercise energy expenditure (EEE), total distance covered, and minutes spent in HR zones (HRZ1-Z5) over the season (p < 0.05). Finally, although average workloads were greater in practices than in matches, when accounting for pre-match warm-ups, competition load was greater than practice (p < 0.05). National Collegiate Athletic Association Division I women's beach volleyball is a demanding, explosive power sport characterized by overall large TL and EEE, particularly in-season when athletes compete in 4 matches per weekend. The workloads observed point to the need to assess and manage training loads and fueling requirements to optimize performance and decrease injury risk.

Distance and Intensity Profiles in Division I Women's Soccer Matches across a Competitive Season

Women’s participation in soccer has increased rapidly. The purpose of this study was to evaluate the physiological demands imposed on women’s NCAA Division I soccer players across a season according to speed, total distance traveled, and numbers of sprints measured via GPS (Polar Team Pro^®). Eighteen athletes (19.2 ± 1.1 years, 50.5 ± 6.5 mL/kg/min and 23.4 ± 3.6% fat) participated in this study. The analysis was obtained through 13 official matches. Speed zones were defined as Zone 1 (1.0 to 5.99 km·h⁻¹), Zone 2 (6.0 to 10.99 km·h⁻¹), Zone 3 (11.0 to 15.49 km·h⁻¹), Zone 4 (15.5 to 19.9 km·h⁻¹) and Zone 5 (sprint > 20 km·h⁻¹), with Zones 4–5 considered as high intensity running. Individual differences in playing time and total distance were highly variable due to substitutions. Average distance traveled per game in quartiles was 3.9 km, 5.6 km and 7.4 km in the 25th, 50th, and 75th quartiles, respectively. Relative to playing time, players travelled an average of 113.64 ± 17.12 m/min (range: 93.7 to 143.5 m/min) and ran one sprint every 4.12 ± 2.06 min. When distance was summated and analyzed for the entire team, significant difference between halves was found for speed Zones 2, 3 and 4, with greater values found in the first half. Total distance, high intensity running and sprint distance were significantly less than previously recorded in professional players. These findings suggest that coaches should consider the unique physiological demands and recovery opportunities present in NCAA play when constructing practices and conditioning programs.

Can Rules in Technical-Tactical Decisions Influence on Physical and Mental Load during Soccer Training? A Pilot Study

This study aimed to analyze the effects of rules limitations in pass decisions during soccer tasks on physical and mental load reported by players. Participants were 40 semiprofessional Spanish soccer players (Mage = 22.40, SD = 2.25) from two male teams. Two training sessions with four tasks (same tasks with different score system: two maintaining ball possession games with goalkeepers, and two maintaining ball possession games) in counterbalanced order between teams were completed. To achieve a goal during limitation tasks, a minimum number of players had to participate in the passes before the goal. Internal (perceived effort and heart rate) and external physical load (distances), mental load (validated adaptation of the NASA-TXL) and fatigue (VASfatigue) were quantified. Paired t-test and magnitude-based inference were conducted. The results showed significantly higher mean speeds (p < 0.01), effort perception (p < 0.001), and mental fatigue (very likely positive) during possession games with restrictions. Additionally, performance satisfaction obtained significantly higher values with goalkeepers and pass restrictions (very likely positive). External physical load showed no significant differences between situations. The influence of mental fatigue on internal load and the complexity of the tasks could explain these results. Coaches can use this information to manipulate the training load in ecological conditions.

Impact of contextual factors on match demands experienced by elite male referees during international basketball tournaments

We aimed to assess the cardiovascular responses and locomotory demands of male referees during diverse elite, international, basketball matches, and to investigate the influence of moderating factors (competition sex, level and stage) on these demands. Cardiovascular and locomotory responses were monitored in 123 elite, male referees while officiating 283 basketball sessions (preparation until match end), during group and playoff stages, of women's and men's FIBA Continental and World Cups at senior and youth level. The total and average session distance and velocity were ~4740 m, 19.0 m·min ^-1 and 2 km·h ^-1. Referees experienced an average relative HR of 60-65% maximum HR with ~85% of each session spent within the very light to moderate HR categories. The average session relative HR was significantly greater for men compared to women competition, during senior compared to youth sessions, and for the group compared to the playoff stage sessions. Mean distance covered was significantly greater during senior and men compared with youth and women sessions. Elite, international male basketball referees experienced moderate cardiovascular load accompanied with intermittent locomotor activities during international sessions when accounting for all occupational activities. International competitions are more demanding for referees based upon competition sex, level and stage.