Leonor Gallardo

Purpose : This study aimed to evaluate the reliability of the acceleration–speed profile in elite male and female football players across 3 competitive seasons. Specifically, we assessed how the number and type of microcycles influence the reliability of theoretical maximal acceleration (A ₀ ) and speed (S ₀ ). Methods : GPS-derived acceleration and speed data were collected from 181 women’s and 146 men’s microcycles. Acceleration–speed profiles were constructed using overlapping windows of 1 to 5 consecutive microcycles, classified as competitive, including match day (MD) or post-MD (MD + 1) or noncompetitive, not including MD or MD + 1. Linear regressions were applied to estimate A ₀ and S ₀ . Results : Theoretical maximal acceleration and S ₀ increased with longer microcycles but plateaued beyond 5 days. Grouping by 2 microcycles showed the highest reliability for both A ₀ and S ₀ in male and female players. Competitive profiles consistently outperformed noncompetitive profiles in terms of stability and signal quality across both sexes. Male players demonstrated lower variability and higher signal-to-noise ratios than female players. Conclusions : The most reliable acceleration–speed profiles can be obtained from 2 consecutive microcycles, each including 5 or more sessions and at least 1 MD or MD + 1. These findings support the integration of in situ sprint profiling into applied performance monitoring without the need for isolated testing.

(1) Background: This study examined the acute and chronic effects of sled-resisted training on power, strength, jump height (evaluated through a CMJ), and sprint kinematics in Spanish amateur football players. (2) Methods: A total of 19 football players (28 ± 8 years; 172 ± 12 cm; 79.3 ± 22.3 kg) performed 10 sled-resisted training sessions with loads of 80% (±2 kg) of their body mass on the day before the match (MD-1). Performance was assessed using a CMJ measured with the My Jump Lab app and sprint kinematics recorded with the 1080 Sprint system; both of these sensor-based technologies are validated for sports performance analysis. The CMJ was performed on MD-1 before the training and again on match day. Sprinting was evaluated before the sled-resisted training and again one week after it ended. (3) Results: These results suggest that sled training with heavy loads and low volume may not have acute effects on CMJ in amateur football players 24 h after it is performed, but there are chronic improvements in CMJ relative force and changes in sprinting after 10 weeks of sled-resisted training. (4) Conclusions: The findings of this study will enable football coaches and physical trainers to understand the changes in this training method to improve performance in amateur football players, using only three repetitions per player per week.

The aim of this study was to describe and compare the physical demands in Worst-Case Scenarios (WCS) across different competition levels in male and female football of Spanish elite football referees during matches, comparing competitions independently for male and female referees. Physical demands (total distance [TD], total distance > 18 km/h [TD18], total distance > 21 km/h [TD21], total distance > 24 km/h [TD24], accelerations (> 3 m/s2) [Acc] and decelerations (<-3 m/s2) [Dec]) were recorded over different time windows (0.5, 1, 3, 5 and 10 min) on 24 professional male Spanish football referees from male 1st Division, 26 from male 2nd Division and 24 professional female Spanish football referees from female 1st Division during the 2020/21, 2021/22, and 2022/23 seasons over a total of 2,156 official matches, using Global Positioning Systems. Results showed that male referees experienced higher physical demands, particularly during the shortest time windows of WCS (0.5 and 1 min), where the highest relative physical loads were observed. Significant differences (p < 0.05) were found between competitions, with higher demands recorded in the 2nd Division and Champions League. In contrast, female referees faced their greatest physical demands in national competitions, such as the Queen’s Cup, compared to international competitions. Both genders demonstrated higher intensity during shorter time windows, highlighting the need to be prepared for short and high-intensity match periods. The study concludes that physical demands vary according to gender and level of competition. Male referees face higher workloads, and female referees have different demands depending on the competitive context. These findings highlight the need for tailored training programs and recovery strategies to address the specific demands of referees across different match contexts. For male referees, training should emphasize short-duration, high-intensity efforts, especially for competitions such as the Second Division and Champions League. For female referees, programs should replicate the demands observed in national competitions like the Queen’s Cup. These adaptations can improve performance, reduce injury risk, and enhance match officiating quality. not applicable.

Background: Leisure-time physical activity is the preferred domain by the population to follow physical activity recommendations, helping to maintain a healthy lifestyle. However, the main issue in this type of physical activity intervention is massive dropout. Methods: Using monthly data from 20,908 leisure/fitness center members (2011–2016), we estimate a discrete-time duration model to examine how membership duration influences dropout probability, addressing cross-sectional limitations. Additionally, we assess the explanatory power of different covariate groups. Results: Dropout probability follows a seasonal pattern, peaking within the first 3 months before declining and stabilizing over time. Short-term memberships and low attendance frequency significantly increase dropout risk, confirming that membership conditions and time-related variables are key predictors of retention. Additionally, macroeconomic factors particularly unemployment play a crucial role in increasing dropout probability. Conclusions: These results could help both recreational facility managers and policymakers to design strategies to reduce dropout among physical activity practitioners, in particular, in the current situation generated by the COVID-19 crisis.

The aim was to analyse the consequences of a congested schedule (due to the COVID-19 lockdown) on creatine kinase (CK) in elite football players using GPS tracking technology. A total of 17 elite football players were monitored in training and competition with a global positioning system. Variables including total distance, high-intensity distance, and distance acceleration and deceleration were analysed. Different measurements of serum creatine kinase (CK) concentration were performed on match day (MD) and at 24 h (MD+1), 48 h (MD+2), and 72 h (MD+3) after each match to study the muscle damage of each individual player caused during the match. The results showed a significant increase in physical demands in training (in relative terms regarding the match) at MD+3 compared to MD+1 and MD+2. Furthermore, at +72 h, CK decreases to a value almost the same as that before MD. On the other hand, the players with lower demands for high-intensity actions in the match showed a higher reduction in the concentration of CK at MD+3 compared to MD+1 and MD+2 (p < 0.05). It became evident that players with high-intensity demand and a high number of accelerations and decelerations need more time to assimilate the match load and can remain in a state of muscle fatigue for up to 3 days. In addition, a congested schedule can lead to a state of chronic fatigue in elite football players, limiting physical performance and possibly increasing the potential risk of injury for football players.

The aim of this study is to analyse the relationship between sport modalities practiced, physical fitness, body composition, and healthy habits in an active young population, using a statistical model for prediction. A total of 2255 (1528 boys and 727 girls) children and adolescents aged 6–17 years old who were involved in extracurricular sports from rural areas of Spain participated. Physical fitness was assessed through validated field test and, body composition was determinated using bioelectrical impedance analysis. Adherence to the Mediterranean diet was assessed by KIDMED questionnaire. The general sport variable was significant in VO₂max when comparing the invasion and combat modalities to the reference level (court/net). The sex and age variables revealed significant differences in all physical fitness and body composition parameters. Health parameters, such as hours of additional practice, adherence to the Mediterranean diet, and previous experience, showed significant differences. The study concludes that the sport modality variables of training, sex, age, and maturational period have an impact on body composition and fitness parameters in this population. Therefore, by focusing on factors associated with lower values in health indicators, we can prevent health problems during adulthood, such as cardiorespiratory deficits.

The aim of this study is to analyze the worst-case scenarios of professional futsal referees during the first and second half of official matches in the Spanish Futsal Cup using a Local Positioning System (LPS) for monitoring their movement patterns. Eight professional futsal referees (40 ± 3.43 years; 1.80 ± 0.03 m; 72.84 ± 4.01 kg) participated in the study. The external load (total distance, high-speed running distance and efforts, sprint distance and efforts, and accelerations and decelerations distances) of the referees was monitored and collected using an LPS. The results revealed significant differences in the worst-case scenarios of the futsal referees during the match according to the time window analyzed (p < 0.05). The longest time windows (120 s, 180 s, and 300 s) showed lower relative total distances in the worst-case scenarios (p < 0.05). The high-speed running distances were significatively higher in the first half for the 120 s (+2.65 m·min⁻¹; ES: 1.25), 180 s (+1.55 m·min⁻¹; ES: 1.28), and 300 s (+0.95 m·min⁻¹; ES: 1.14) time windows (p < 0.05). No differences were found between the first and second half for the high-intensity deceleration distance (p > 0.05). These results will serve to prepare the referees in the best conditions for the competition and adapt the training plans to the worst-case scenarios.

Alonso-Callejo, A, García-Unanue, J, Guitart-Trench, M, Majano, C, Gallardo, L, and Felipe, J. Validity and reliability of the acceleration-speed profile for assessing running kinematics' variables derived from the force-velocity profile in professional soccer players. J Strength Cond Res 38(3): 563–570, 2024—The aim of this research is to assess the validity and reliability of the acceleration-speed profile (ASP) for measuring the mechanical variables of running kinematics when compared with the force-velocity profile (FVP) obtained by reference systems. The ASP and FVP of 14 male players of an elite football club were assessed during a competitive microcycle. Three ASPs were tested according to the number and type of sessions included in its plotting (ASP1: 5 training sessions and competitive match; ASP2: 5 training sessions; ASP3: competitive match). Force-velocity profile was tested 4 days before match (MD-4) with a 30-m linear sprint using 3 previously validated devices (encoder, mobile App, and global positioning system). Level of significance was p < 0.05. Acceptable reliability (intraclass correlation coefficient > 0.5) was found between the ASP1 and the encoder for all variables (F₀-A₀, V₀-S₀, and V_max). The more reliable ASP method was the ASP1 showing a lower bias than the ASP2 and ASP3 methods for almost all variables and reference systems. For ASP1, lower mean absolute error (MAE: 0.3–0.5) and higher correlation (P-M corr: 0.57–0.92) were found on variables related to the velocity in comparison with variables related to the early acceleration phase (F₀-A₀; MAE: 0.49–0.63; P-M corr: 0.13–0.41). Acceleration-speed profile, when computed with data from a complete competitive week, is a reliable method for analyzing variables derived from velocity and acceleration kinematics. From these results, practitioners could implement ASP and the applications of the FVP previously studied, such as resistance training prescription, performance assessment, and return-to-play management.

Background: Although the scientific literature has previously described the impact of worksite programs based on physical activity (WPPAs) on employees’ productivity and health in different contexts, the effect of these programs has not been analyzed based on the characteristics or modalities of physical activity (PA) performed (e.g., aerobic exercise, strength training, flexibility). In addition, studies on WPPAs usually report health and productivity outcomes separately, not integrated into a single study. Knowing the health and economic-related impacts of a WPPAs could provide useful information for stakeholders and policy development.Objective: The purpose of this review was as follows: (1) to analyze the effect of different modalities of WPPAs on employees’ productivity and health and (2) to investigate the economic impact of WPPAs.Methods: This systematic review is registered in PROSPERO (CRD42021230626) and complies with PRISMA guidelines. Only randomized controlled trials from 1997 to March 2021 were included. Two reviewers independently screened abstracts and full texts for study eligibility, extracted the data, and performed a quality assessment using the Cochrane Collaboration Risk-of-Bias Tool for randomized trials. Population, instruments, comparison, and outcome (PICO) elements were used to define eligibility criteria. Eight-hundred sixty relevant studies were found through electronic searches in PubMed, Web of Science, Medline, Scopus, and SPORTDiscus databases. Once the eligibility criteria were applied, a total of 16 papers were included.Results: Workability was the productivity variable most positively impacted by WPPAs. Cardiorespiratory fitness, muscle strength, and musculoskeletal symptoms health variables improved in all the studies included. It was not possible to fully examine the effectiveness of each exercise modality because of the heterogeneity in methodology, duration, and working population. Finally, cost-effectiveness could not be analyzed because this information was not reported in most studies.Conclusion: All types of WPPAs analyzed improved workers’ productivity and health. However, the heterogeneity of WPPAs does not allow to identify which modality is more effective.

The aim of this study was to describe and analyse the effects of a 12-week football programme on body composition (fat mass, muscle mass, and bone mass) in children compared to a sedentary lifestyle, as well as the physical demands and loads required in training and matches in young football players (U10–U12). Forty children were included, divided into two groups: a football group (FG; n = 20) and a control group (CG; n = 20). Body composition was analysed using DXA and physical demands were analysed using GPS, with a total of 504 observations. Total bone mineral content (BMC) was significantly increased in FG-U12 (p = 0.025) after training. Total bone mineral density (BMD) was increased after the 12 weeks in FG-U10 (p = 0.001) and FG-U12 (p = 0.002). Leg BMC in FG-U10 (p < 0.05; 2.2 to 7.1 g) and FG-U12 (p < 0.05; 2.0 to 17.0 g) was increased after 12 weeks. VO₂ max after training was significantly improved in FG-U10 (p < 0.05; ES: 1.7 to 5.2 mL/kg/min) and FG-U12 (p < 0.05; 0.3 to 3.8 mL/kg/min). Among U10s, midfielders covered greater distances and had higher intensity accelerations (p < 0.05; ES: 1.05 to 2.00) than forwards and defenders. Among U12s, midfielders in matches covered greater distances and at higher intensity than in training (p < 0.05; ES: 1.05 to 2.39). Football practice produces benefits in total and lower limb BMC, BMD, and VO₂ max. The training and position of midfielders require higher physical demands.