The efficiency index (Effindex) combines internal and external loads, and it has been considered a promising tool to evaluate physical fitness status. However, its real applicability and limitations have not been elucidated yet. To examine and discuss the findings from studies that used Effindex...

Big Data has real value when the veracity of the collected data has been previously identified. However, data veracity for load monitoring in professional soccer players has not been analyzed yet. This systematic review aims to evaluate the current evidence from the scientific literature related to data veracity for load monitoring in professional soccer. Systematic searches through the PubMed, Scopus, and Web of Science databases were conducted for reports onthe data veracity of diverse load monitoring tools and the associated parameters used in professional soccer. Ninety-four studies were finally included in the review, with 39 different tools used and 578 associated parameters identified. The pooled sample consisted of 2066 footballers (95% male: 24 ± 3 years and 5% female: 24 ± 1 years). Seventy-three percent of these studies did not report veracity metrics for anyof the parameters from these tools. Thus, data veracity was found for 54% of tools and 23% of parameters. The current information will assist in the selection of the most appropriate tools and parameters to be used for load monitoring with traditional and Big Data approaches while identifying those still requiring the analysis of their veracity metrics or their improvement to acceptable veracity levels.

OBJECTIVE: to determine the individual profile of blood concentration of creatine kinase CK in elite soccer players as well as to analyze the CK concentrations in different periods during the Professional Brazilian Championship.METHODS: resting CK of 17 soccer players was evaluated before the competition pre-season and after the matches 36 and 46 hours after the games CKGame for the individual blood CK. The Chi-square test was used to analyze the individual CK during the season. The competitive season was divided into three periods: initial, intermediate and final. The one-way ANOVA with repeated measurements followed by post hoc Student-Newman-Keuls test was used to compare the individual CK of each soccer player in each competitive period. The significance level was set at p<0.05.RESULTS: the highest frequency of individual CK was found in the second quartile 71 observations and the lowest frequency in the first 26 observations and the fourth quartile 40 observations compared to the expected number of 45.8 x2=22.21. CK concentrations were lower in the intermediate mean=66.99% and final mean=60.21% periods than in the initial period mean=89.33%.CONCLUSION: soccer players did not show elevated muscle damage and probably a muscle adaptation occurred in the competition, due to the reduction of CK concentrations observed.

This study investigated the differences in external and internal load during pre-season training sessions carried out with different SSGs and a friendly match in top-class professional football players. The study was conducted over a full pre-season. Participants were 9 male top-class professional football players (25 ± 5 years; 74 ± 8 kg; 177 ± 8 cm). The following variables were measured: training session duration (min), average heart rate (bpm), total distance (m), distance covered per minute (m/min), the total number of accelerations > 2.5 m/s², number of accelerations > 2.5 m/s² per minute, average distance of accelerations (m), the average value of acceleration (m/s²). One-way ANOVA was performed to analyze the variance of all evaluated variables. No differences were found in the average accelerations (m/s²) (0.128) among all the training formats. Moderate differences were found in number of accelerations > 2.5 m/s² per minute (η2 = 0.396, moderate effect) and average distance of accelerations (η2 = 0.545). Strong differences were found in HR (η2 = 0.788, large effect), total distance (η2 = 0.797, strong effect), distance per minute (η2 = 0.775 strong effect), total number of accelerations > 2.5 m/s² (η2 = 0.699 strong effect). Significant correlations were found just for the number of accelerations > 2.5 m/s² and the number of accelerations > 2.5 m/s² per minute with the 4v4, 8v8 and the FM (r = 0.828–0.890, r² = 69% – 79%; p < 0.01). External and internal loads differ across different SSGs and a FM during the pre-season training sessions.

Purpose : This study compared the temporal structure of high-speed running (HSR) efforts and subsequent recovery profiles between starters and substitutes, and across playing positions, in professional soccer. Methods : Sixty-one male professional players (26.9 [5.2] y) from 2 teams were monitored across 24 official matches, resulting in 215 match observations (148 starters and 67 substitutes). Match running performance was monitored using 10-Hz global navigation satellite system units. Episode-level variables included HSR duration, recovery duration, HSR–recovery intervals, and intervals between consecutive HSR efforts. Linear mixed-effects models were used to compare playing roles, while recovery durations were categorized into 120 s bands and analyzed using χ ² tests. Results : Mean HSR duration did not differ between starters and substitutes (2.37 [1.64] vs 2.40 [1.75] s), nor were differences for HSR–recovery intervals (3.86 [3.59] vs 3.75 [3.55] s), HSR–HSR intervals (3.51 [3.48] vs 3.57 [3.16] s), or the HSR/recovery ratio (1.05 [1.53] vs 1.00 [1.66]) (all P > .05). However, starters displayed significantly shorter recovery durations than substitutes (13.34 [33.51] vs 16.72 [39.50] s; P = .017). Recovery-band distributions differed by playing role ( P < .001), with starters completing a greater proportion (97% vs 93%) of short recoveries (<60 s), whereas substitutes exhibited relatively higher proportions of moderate (6%) and long (1%) recoveries. Playing position influenced temporal intervals and the HSR/recovery ratio, but not HSR or recovery duration. Conclusions : Despite longer recovery durations in substitutes, the overall temporal structure of HSR efforts was largely consistent between playing roles, with HSR and recovery periods predominantly occurring within short-time windows.