Elite North American soccer performance in thermally challenging environments: An explorative approach to tracking outcomes.

AIMS: The physiologic challenges related to performances in hot conditions calls for dedicated consideration when planning athlete training, although complete amelioration of the effects of heat may not be possible. We aimed to quantify within-subject correlations between different measures of environmental temperature and performance changes over multiple elite soccer competitions. METHODS: Thirty-seven elite male soccer players (age: 26 ± 3.4 years, height: 171 ± 2 cm, body mass: 78 ± 7.1 kg) competed in North America over four seasons (range: 3 to 98 matches). Players wore global positioning system devices during games and reported differential-RPE immediately post game. Temperatures at kick-off, week average temperature, the difference between game-day and week average (DiffTemp), and heat index at kick-off were obtained. Within-player correlations were calculated using general linear models to quantify associations between fluctuations in temperature measures and physical and perceived outputs. RESULTS: Correlations between total distance and the various temperature measures were trivial to small (range: -0.08 to 0.13, p=<0.001-0.02). Small negative correlations were found between all temperature measures except DiffTemp and high-speed running (HSR) (range: -0.17 to -0.14, p=<0.001). Most correlations between differential-RPE and temperature measures were trivial to small and not significant (r = 0.06 to 0.18 p = 0.03-0.92) although breathlessness-RPE and heat index showed a small significant association (P = 0.018). CONCLUSION: Decrements in HSR appear to be associated with increased environmental temperature, however, these associations are small in magnitude.

Does Prematch Neuromuscular Performance Affect Running Performance in Collegiate Elite Female Soccer?

ABSTRACT: Ishida, A, Draper, G, White, JB, and Travis, SK. Does prematch neuromuscular performance affect running performance in collegiate elite female soccer? J Strength Cond Res 37(4): 854-858, 2023-The purpose of this study was to investigate whether prematch neuromuscular performance affected match physical performance by player position in Division I collegiate female soccer. Fourteen players participated (20.7 ± 1.3 years; 165.1 ± 6.0 cm; 63.3 ± 7.0 kg) in this study. Players were selected based on being free from injuries, playing for a duration of ≥72 minutes, and match intervals were ≥2 days. Data included 73 observations ( n = 5 defenders, n = 7 midfielders, and n = 2 forward) from 14 official matches. Prematch neuromuscular performance was assessed using countermovement jump (CMJ) with polyvinyl chloride pipe on dual force plates. Countermovement jump variables included jump height (JH) and relative peak power (RPP). Match physical performance included average speed, high-speed running (HSR), and number of high accelerations and decelerations. Linear mixed model was compiled with fixed effects of loaded with fixed effect of JH, RPP, and position and random effects per individual player. In CMJ and player position model, RPP was a significant predictor for average HSR ( p = 0.003) while fixed effects of JH and position were not significant ( p = 0.15-0.86). The fixed and random effects explained 34.8 and 42.1% of variances in average HSR. In CMJ-only model, RPP significantly predicted the variances in average HSR ( p = 0.001). The fixed effects and random effects of the model explained 22.7 and 51.8% of the variance in average HSR. However, position-only was not a significant predictor for average HSR in the position-only model ( p = 0.26 and 0.33). Prematch CMJ RPP may be the greatest predictor of average HSR in collegiate female soccer.

Training Volume and High-Speed Loads Vary Within Microcycle in Elite North American Soccer Players.

ABSTRACT: Ishida, A, Draper, G, Wright, M, Emerson, J, and Stone, MH. Training volume and high-speed loads vary within microcycle in elite North American soccer players. J Strength Cond Res 37(11): 2229-2234, 2023-The purposes of this study were to reduce dimensionality of external training load variables and examine how the selected variables varied within microcycle in elite North American soccer players. Data were collected from 18 players during 2018-2020 in-seasons. Microcycle was categorized as 1, 2, 3, 4, 5 days before match day (MD-1, MD-2, MD-3, MD-4, and MD-5, respectively). Training load variables included total distance, average speed, maximum velocity, high-speed running distance (HSR), average HSR, HSR efforts, average HSR efforts, sprint distance, average sprint distance, sprint efforts, average sprint efforts, total PlayerLoad, and average PlayerLoad. The first principal component (PC) can explain 66.0% of the variances and be represented by "high-speed load" (e.g., HSR and sprint-related variables) with the second PC relating to "volume" (e.g., total distance and PlayerLoad) accounting for 17.9% of the variance. Average sprint distance and total distance were selected for further analysis. Average sprint distance was significantly higher at MD-3 than at MD-2 (p = 0.01, mean difference = 0.36 m•minute-1, 95% confidence intervals [CIs] = 0.07-0.65 m•minute-1) and MD-4 (p = 0.012, mean difference = 0.26 m•minute-1, 95% CIs = 0.10-0.41 m•minute-1). Total distance was significantly higher at MD-3 than at MD-1 (p < 0.001, mean difference = 1,465 m, 95% CIs = 1,003-1926 m), and MD-2 (p < 0.001, mean difference = 941 m, 95% CIs = 523-1,360 m). Principal component analysis may simplify reporting process of external training loads. Practitioners may need to choose "volume" and "high-speed load" variables. Elite North American Soccer players may accumulate higher average sprint distance at MD-3 than at other training days.

Player Position Affects Relationship Between Internal and External Training Loads During Division I Collegiate Female Soccer Season.

ABSTRACT: Ishida, A, Travis, SK, Draper, G, White, JB, and Stone, MH. Player position affects relationship between internal and external training loads during Division I collegiate female soccer season. J Strength Cond Res 36(2): 513-517, 2022-The purpose of this study was to investigate how competition phase and player position affect the relationship between internal and external training loads (ITL and ETL, respectively) in collegiate female soccer. Seventeen players participated (21.8 ± 1.7 years; 165.1 ± 6.2 cm; and 63.7 ± 7.9 kg). Nineteen match-plays (10 nonconference and 9 conference) were completed during the 2019 competitive season, including 270 observations of 17 players (defenders = 5, midfielders = 9, and forwards = 3). Internal training load was assessed using session rating of perceived exertion (sRPE). External training load included total distance and high-speed running (HSR) distance. A linear mixed model was compiled with fixed effects of total distance, HSR, competition phase, and player position (defenders, midfielders, and forwards) and random effects of player. There were statistically significant main effects for total distance (p < 0.001), HSR (p = 0.047) and player position (p = 0.045) on the prediction model of sRPE. However, the main effect of competition phase did not statistically contribute to the prediction model of sRPE (p = 0.38). In the final model, total distance (p < 0.001) and player position for forwards (p = 0.008) were significant predictors of sRPE. However, there was no statistically significant fixed effect of HSR on sRPE (p = 0.15). The final model explained 60.6% of the variance in sRPE (R2 = 0.60), whereas the random effect also explained 6.1% of the variance (R2 = 0.06). Our findings indicated that total distance and player position were strong predictors of sRPE. The relationship between ITL and ETL should be monitored by player position in female soccer players.

The Uptake of Nordic Hamstring Exercise Program for Injury Prevention in Major League Soccer and Its Barriers to Implementation in Practice.

CONTEXT: It is well demonstrated that Nordic hamstring (NH) program has poor compliance across European soccer clubs, but little is known about its implementation in Major League Soccer (MLS). The authors aimed to investigate MLS hamstring prevention practices and compliance with the NH program and understand the reasons for its inclusion or exclusion. DESIGN: A cross-sectional electronic survey was completed by 24 of the 26 (92%) MLS top-division soccer clubs. METHODS: The survey, based on the Reach, Efficacy, Adoption, Implementation, and Maintenance framework, was sent to team medical staff. Medical staff were also asked for opinions on barriers to implementation. RESULTS: Eighteen clubs (75%) reported a formal hamstring injury prevention program, with eccentric exercises (94%; 95% CI [confidence interval], 74%-99%), high-speed running (94%; 95% CI, 74%-99%), and NH exercises (89%; 95% CI, 67%-97%) the most common strategies adopted. Fifteen clubs partially implemented the NH program, but only 5 (21%; 95% CI, 9%-40%) completed the full program and were classed as compliant. A total of 20 respondents reported that player perception and muscle soreness (83%; 95% CI, 64%-93%) were barriers to the implementation of the NH program. On a 5-point Likert scale, respondents "partially agreed" (4.13 [0.80]) that the NH exercise could substantially reduce injuries and would be "effective" at their own club (3.88 [0.61]). CONCLUSIONS: The NH exercise was valued, but negative player perception and muscular soreness were identified as barriers to implementing the full program. Manipulation of volume and frequency should inform future "effectiveness" research to prospectively assess such modifications in the context of MLS.

Practitioners' perspective of non-contact injury risk factors and injury prevention programming in professional North American male soccer.

OBJECTIVE: To evaluate non-contact injury prevention strategies of professional men's soccer clubs in elite North American league soccer. To understand the application, perceived effectiveness and barriers to implementation. DESIGN: Online cross-Sectional Study. SETTING: North American elite soccer teams. PARTICIPANTS: 96 medical and performance support staff of elite North American teams. MAIN OUTCOME MEASURE: The survey consisted of 20 questions and captured 1) practitioners' demographics; 2) perceptions of risk factors; 3) the use of assessment and monitoring strategies; and 4) perceptions of the implementation of injury prevention programmes'. RESULTS: Injury prevention programmes were perceived as 'effective' (Median 4, Interquartile range 4-4) and reduced injury rates (n = 94, 98%, 95 CI% 93 to 99). A range of potential risk factors were rated as "very important" (4.58 ± 0.52 Likert scale points; mean ± standard deviation). A multi-disciplinary approach to the design, application and monitoring of programmes was generally adopted. Competing training priorities (n = 75, 78%, 95 CI% 69 to 85) and game schedules (n = 71, 74%, 95 CI% 64 to 82) were the most prevalent barriers to injury prevention implementation. CONCLUSIONS: Injury prevention programmes were perceived as effective in reducing non-contact injuries. Managing the conflicting priorities between scheduling training, tactical and conditioning goals were considered the key barriers to desired implementation.

Do environmental temperatures and altitudes affect physical outputs of elite football athletes in match conditions? A systematic review of the 'real world' studies.

Players involved in the various football codes compete throughout the calendar year around the world. Therefore, environmental stressors such as temperature and altitude should be considered in preparation for, and during, matches. We aimed to systematically review the observational and quasi-experimental studies that have been specifically designed to quantify the effects of temperature (hot or cold) high altitude on in-match physical performance indicators. A search of electronic databases (Web of Science, Scopus, SPORTDiscus, PubMed/MEDLINE) was conducted, with 19,424 papers identified as relevant. Following sifting in relation to the eligibility criteria, 12 papers were deemed directly relevant. The reviewed studies scored 6-9 (on a 0-9 scale) for quality assessment using a previously used scale. The major outcome variables relevant to the current review were total distance (m), high-speed running (m) and high-speed runs (count) measured during matches. Standardized effect sizes (ES) were heterogeneous across studies for total distance (ES: -0.96 to -0.14) and high-speed running (ES: -0.69 to 0.12) for >1000 m vs sea-level, time spent at the given altitude being a putative factor for this heterogeneity. Heat had mainly detrimental effects on performance, but ES were, again, heterogeneous across studies (ES: -1.25 to 0.26), dependent on temperature. Given the small number of studies that involved mostly male athletes, and large heterogeneity across studies, more research needs be conducted on physical performance in these environmental conditions, with attention paid to standardizing outcomes and broadening the approaches of studies to guide future decision-making in professional sporting environments.

Genomic Epidemiology of a Severe Acute Respiratory Syndrome Coronavirus 2 Outbreak in a US Major League Soccer Club: Was It Travel Related?

Background: Professional soccer athletes are at risk of acquiring severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). United States Major League Soccer (MLS) uses protocol-based SARS-CoV-2 testing for identification of individuals with coronavirus disease 2019. Methods: Per MLS protocol, fully vaccinated players underwent SARS-CoV-2 real-time polymerase chain reaction testing weekly; unvaccinated players were tested every other day. Demographic and epidemiologic data were collected from individuals who tested positive, and contact tracing was performed. Whole genome sequencing (WGS) was performed on positive specimens, and phylogenetic analyses were used to identify potential transmission patterns. Results: In the fall of 2021, all 30 players from 1 MLS team underwent SARS-CoV-2 testing per protocol; 27 (90%) were vaccinated. One player who had recently traveled to Africa tested positive for SARS-CoV-2; within the following 2 weeks, 10 additional players and 1 staff member tested positive. WGS yielded full genome sequences for 10 samples, including 1 from the traveler. The traveler's sample was Delta sublineage AY.36 and was closely related to a sequence from Africa. Nine samples yielded other Delta sublineages including AY.4 (n = 7), AY.39 (n = 1), and B.1.617.2 (n = 1). The 7 AY.4 sequences clustered together; suggesting a common source of infection. Transmission from a family member visiting from England to an MLS player was identified as the potential index case. The other 2 AY.4 sequences differed from this group by 1-3 nucleotides, as did a partial genome sequence from an additional team member. Conclusions: WGS is a useful tool for understanding SARS-CoV-2 transmission dynamics in professional sports teams.