Relationships between Fitness Status and Blood Biomarkers in Professional Soccer Players

Assessment of Strength and Power Capacities in Elite Male Soccer: A Systematic Review of Test Protocols Used in Practice and Research

BACKGROUND

Strength and power represent two crucial physical qualities for the attainment of a high level of performance considering the frequency and the importance of explosive actions occurring during elite soccer match-play. Evaluation of strength and power is a multifaceted concept involving a vast array of tests and outcome variables. Nevertheless, a comprehensive and systematic search of strength and power assessment procedures in elite soccer has yet to be undertaken.

OBJECTIVES

The aims of this systematic review were to: (1) identify the tests and outcome variables used to assess strength and power of elite male soccer players; (2) provide normative values for the most common tests of strength and power across different playing levels; and (3) report the reliability values of these strength and power tests.

METHODS

A systematic review of the academic databases MEDLINE, CINAHL, SPORTDiscus, Web of Science and OVID for studies published until August 2023 was conducted, following the Preferred Reporting Items of Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Studies were eligible for inclusion if they: (1) were original research studies, published in a peer-reviewed journal, and written in English language; (2) had the primary aim to assess strength and/or power; (3) players were male and older than 17 years of age (i.e., mean age of the group); and (4) their playing level was defined as "professional", "international" or "elite".

RESULTS

Regarding strength testing, 115 studies and 29 different tests were identified. The three most frequent strength tests were the knee extensor isokinetic strength test (58 studies), the knee flexor isokinetic strength test (55 studies) and the Nordic hamstring strength test (13 studies). In terms of power testing, 127 studies with 31 different tests were included. The three most frequent power tests were the countermovement jump with hands fixed on hips (99 studies), the squat jump (48 studies) and the vertical jump with arm swing (29 studies).

CONCLUSIONS

The wide range of different tests and outcome variables identified in this systematic review highlights the large diversity in the employed testing procedures. The establishment of a hybrid testing approach, combining standardised and widely accepted tests for establishing normative standards and enabling comparisons across different contexts, with flexible context-specific testing batteries, has the potential to maximise the impact of testing information for practitioners. In addition, the limited reporting of reliability data across studies highlights the need for practitioners to establish their own reliability measure within their specific contexts, informing the selection of certain tests and outcome variables.

Relationships between physical fitness and match running demands during a futsal congested-weeks training camp

This study examines the relationships between body composition, anthropometry and physical fitness measures, and internal and external load (match physical and running demands) during a congested period of an overseas futsal training camp. Eleven under-20 national futsal players participated in a eleven-day training camp. During the matches, exercise heart rate (HR) and locomotion profiles were recorded via a Polar Team Pro system as the players' internal and external load. The friendly matches were scheduled on the training camp's 2nd, 4th, 6th, 8th, and 10th days. A repeated-measures analysis of variance (ANOVA) and Pearson's correlation coefficient were used for statistical analysis. The results revealed significant differences in sprint (F = 2.74, p = 0.04, η2 = 0.21), accelerations (F = 3.63, p = 0.04, η2 = 0.27), and decelerations (F = 2.73, p = 0.04, η2 = 0.21) performance between the five matches (p < 0.05). Also, the overall body composition and physical fitness measures had large to very large correlations with match running demands during congested periods of futsal competition (p < 0.05). In conclusion, the baseline body composition and the overall physical fitness measures may be essential factors in match running demands during a congested futsal match period. Futsal players who perform better in the 30-15 Intermittent Fitness Test can sustain a greater volume of high-intensity accelerations during a congested period.

Match-to-Match Variation on High-Intensity Demands in a Portuguese Professional Football Team

The aim of this study was to analyze the match-to-match variation in high-intensity demands from one Portuguese professional football team according to playing positions. Twenty-three male outfield professional football players were observed during eighteen matches of the Portuguese Second League. Time-motion data were collected using Global Positioning System (GPS) technology. Match running performance was analyzed based on the following three playing positions: defenders (DF), midfielders (MF), and forwards (FW). Repeated measures ANOVA was utilized to compare match running performance within each position role, and seasonal running variation. Practical differences were assessed using the smallest worthwhile change (SWC), coefficient of variation (CV), and twice the coefficient of variation (2CV). Significant differences were found among playing positions in total distance covered (F = 15.45, p < 0.001, η2 = 0.33), average speed (F = 12.79, p < 0.001, η2 = 0.29), high-speed running (F = 16.93, p < 0.001, η2 = 0.36), sprinting (F = 13.49, p < 0.001, η2 = 0.31), accelerations (F = 4.69, p = 0.001, η2 = 0.132), and decelerations (F = 12.21, p < 0.001, η2 = 0.284). The match-to-match running performance encompassed TD (6.59%), AvS (8.67%), HSRr (37.83%), SPR (34.82%), ACC (26.92%), and DEC (27.85%). CV values for total distance covered ranged from 4.87-6.82%, with forwards and midfielders exhibiting the greatest and smallest variation, respectively. Midfielders demonstrated the highest match-to-match variation for all other analyzed variables (8.12-69.17%). All playing positions showed significant variation in high-demanding variables (26.94-37.83%). This study presents the initial analysis of match-to-match variation in high-intensity demands within a Portuguese professional football team. Thus, the position's specificity and context can provide a helpful strategy for evaluating match-to-match running performance, and for recommending individualized training exercises based on the peak and high-intensity demands for each player's role within the game.

Molecular insights into the lipid-carbohydrates metabolism switch under the endurance effort in Arabian horses

BACKGROUND

Recent studies have shown that in Arabian horse muscle, long-term exercise-induced expression of genes related to fatty acid degradation and the downregulation of genes belonging to the glycolysis/gluconeogenesis and insulin signalling pathways. Long-lasting physical exertion may trigger the metabolism to switch the main energy source from carbohydrates to lipids due to higher caloric content.

OBJECTIVES

To describe the metabolism adaptation at the whole transcriptome of blood to endurance effort in Arabian horses.

STUDY DESIGN

In vivo experiment.

METHODS

Venous blood samples from 10 Arabian horses were taken before and after a 120 km long endurance ride to isolate the RNA and perform the high-throughput NGS transcriptome sequencing.

RESULTS

The results, including KEGG (Kyoto Encyclopaedia of Genes and Genomes) and GO (Gene Ontology) analyses, allowed us to describe the most significantly upregulated-ARV1, DGAT2, LIPE, APOA2, MOGAT1, MOGAT2, GYS1, GYS2 and downregulated-ACACA, ACACB, FADS1, FADS2 genes involved in carbohydrate and lipid metabolism. Also, the increased expression of RAF1, KRAS and NRAS genes involved in the Insulin pathway and PI3K-Akt was shown.

MAIN LIMITATIONS

Limited sample size, Arabians used for endurance racing were not compared to Arabians from other equestrian disciplines.

CONCLUSIONS

This general insight into the processes described supports the thesis of the lipid-carbohydrates metabolism switch in endurance Arabian horses and provides the basis for further research.

The Association of Serum Calprotectin with Fitness Indicators and Biochemical Markers in High-Level Athletes: A Continuous Dynamic Monitoring during One Competitive Season

The objective was to determine the associations between several biochemical indicators and the dynamics of concentration change across four physical fitness phases over the period of a competitive season. Furthermore, associations between serum calprotectin and biomarkers of inflammation or muscle injury and physical indicators were examined.

SUBJECTS AND METHODS

Twenty professional male water polo players (median age: 28 (22-42)) were included in this study. Serum creatine kinase activity was determined by the automated photometric UV method. The concentrations of calprotectin, C-reactive protein, and myoglobin were measured using an automated immunoturbidimetric method, while an automated immunochemistry method was employed for interleukin-6, troponin I, and cortisol determination. Tests of repeated strength, maximal strength, and static strength were used to evaluate physical activity.

RESULTS

Serum calprotectin concentrations expressed in median and IQR were significantly different: T1: 2.92 g/mL (2.47; 3.86); T2: 2.35 g/mL (1.26; 2.87); T3: 2.27 g/mL (1.60; 3.27); and T4: 1.47 g/mL (1.04; 2.85) (p = 0.004). Cortisol concentration and CK activity showed significant changes among phases (p = 0.049 and p = 0.014, respectively). Each physical activity examined showed a significant seasonal decrease (all p values were 0.001). Calprotectin serum concentration and indicators of muscular injury, inflammation, and physical activity were found to be correlated during particular stages of the seasonal examination.

CONCLUSIONS

Calprotectin values determined throughout one competitive season decreased as training intensity among water polo players increased. Serum calprotectin concentrations and indicators were related to biochemical markers of inflammation and muscle damage.

Acute effect of moderate and high-intensity interval exercises on asprosin and BDNF levels in inactive normal weight and obese individuals

This study aimed to examine the acute effects of moderate-intensity aerobic and high-intensity interval exercise protocols on Asprosin and Brain-Derived Neurotrophic Factor (BDNF) levels in inactive normal weight and obese individuals. A total of 20 male individuals aged 18-65 years, ten normal weight (NW) (Body Mass Index (BMI): 18.5-24.99 kg/m²) and 10 obese (Ob) (BMI: 24.99-35.00 kg/m²) participated in this study, voluntarily. Moderate aerobic exercise (AE) (main circuit 30 min, between 40 and 59% of Heart Rate Reserve: HRR) and High-Intensity Interval exercise (HIIE) running protocols (main circuit 20 min, between 75 and 90% of the HRR for 1 min*10 times, and 1-min active rest at 30% of the HRR) was applied to the volunteer participants in the morning hours (08.00-10.00 a.m.), following the night fasting (at least 8-10 h) for at least 3 days between each other. Blood samples were collected from the participants before and immediately after each exercise protocol, and serum asprosin and BDNF hormone levels were determined by Enzyme-Linked Immunosorbent Assay" method. Basal serum asprosin was found to be significantly higher in the Ob group compared to the NW group (p < .001), while the basal serum BDNF hormone was found to be lower (p < 0.05). It was observed that the serum asprosin level of both groups decreased significantly after both AE and HIIE protocols (p < 0.05). In addition, there was a significantly higher decrease in serum asprosin level in the Ob group compared to the NW group after HIIE protocol. For the Ob group, serum BDNF level increased considerably after HIIE protocol compared to AE protocol (p < 0.05). Serum asprosin was found to be higher in the Ob group, while the serum BDNF was found to be lower. In addition, the acute exercises of different intensity significantly affected hormones that regulate appetite metabolism. In particular, it was observed that the HIIE protocol had a greater effect on the regulation of appetite (hunger-satiety) in the Ob group. This result can be taken into account when planning training programs for these individuals.

Comparison of the Physical, Physiological, and Psychological Responses of the High-Intensity Interval (HIIT) and Small-Sided Games (SSG) Training Programs in Young Elite Soccer Players

We investigated the effects of high-intensity interval (HIIT) and small-sided games (SSG) training programs on physiological and psychological responses in young soccer players. Twenty-four male soccer players (age 16.7 ± 0.9 years) were divided into two groups (HIIT and SSG) and completed a 6-week training programs consisting of two training sessions a week. HIIT consisted of intermittent runs lasting 15 s at the 110% maximum aerobic speed followed by a passive recovery lasting 15 s; SSG was instead structured in a 4 versus 4 players games on a playing field of 25 × 35 m. The muscular power of the lower body was assessed before and after each training session using the 5-jump test to leg length, and two incremental field tests (VAMEVAL test and modified agility t-test). Our results show that HIIT and SSG have similar beneficial effects on the variables connected to the soccer-specific performance and the endurance with little influence on neuromuscular performances. Psychological responses were assessed using the "physical activity enjoyment scale", the Hooper index and the POMS variables. Results showed that SSG offers greater perceived enjoyment than what can be achieved with HIIT. In conclusion, SSG can be considered an effective, more motivating, and fun soccer-specific training that brings about physiological responses and neuromuscular adjustments in young soccer players.

Modeling the Major Influencing Factor on Match Running Performance during the In-Season Phase in a Portuguese Professional Football Team

The aim of this study was two-fold: (1) to analyze the influence of season phase (i.e., the start of the in-season and mid-in-season) on match running performance in a Portuguese professional football team; (2) to determine and model the main factor influencing match running performance during the in-season in this specific football team. Eighteen matches were collected by an 18 Hz global positioning system (GPS) from a professional Portuguese football team during the start of the in-season and mid-in-season. The match running performance was analyzed according to season phases, presenting significant differences in total distance (TD) (tlowerbound = 4.71, p < 0.001; tupperbound = −2.22, p = 0.002), average speed (AvS) (tlowerbound = 359.45, p < 0.001; tupperbound = −359.87, p < 0.001), and relative high speed running (rHSR) (tlowerbound = 13.10, p < 0.001; tupperbound = −10.21, p < 0.001). The logistic regression showed TD (β = −1.59, z = −2.84, p = 0.005) and AvS (β = 2.68, z = −2.84, p = 0.007) as the major factors influencing match running performance during seasonal variation. Sprints and accelerations showed no significance for predicting match running performance during the season phases (β = −0.05 to 1.07, z = −0.95 to 1.07, p = 0.29 to 0.72). Current research confirms that lower and upper bounds should be used to quantify seasonal differences on match running performance. TD and AvS were described as the main factors influencing match running performance during the in-season phase. Thus, it is important to highlight the pace and volume of the game to maximize match running performance.

Analysis of the Sustainability of Long-Term Detraining Caused by COVID-19 Lockdown: Impact on the Maximal Aerobic Speed of Under-16 Soccer Players

This retrospective cohort study aimed to analyze the effect of a 9-week detraining caused by COVID-19 lock-down on the maximal aerobic speed (MAS) of youth soccer players. The study included twenty-two under-16 male players competing at the national league level (15.4 ± 0.7 years old) who were analyzed pre and post the detraining period. The MAS was estimated using the Bronco’s test. Moreover, the self-regulated physical exercise performed by the players during the lockdown was monitored using a questionnaire. Considering the training volume per week, the players were grouped into those working more (>180 min/week) and those working less (<180 min/week) during the lockdown. Within-group changes revealed no significant differences (p = 0.122; d = 0.381) in the group that self-trained less than 180 min/week started (pre-lockdown) at 3.97 ± 0.29 m/s and ended (post-lockdown) at 3.85 ± 0.34 m/s, corresponding to a decrease of 3.02%. For those who self-trained more than 180 min/week during the lockdown, they started with 4.33 ± 0.28 m/s and decreased by 1.62% for 4.26 ± 0.28 m/s (p = 0.319; d = 0.250). The team as a whole (pooled data, all players included) decreased 2.27% from 4.15 ± 0.34 to 4.06 ± 0.37 m/s (p = 0.077; d = 0.321). Between group analysis revealed that the group of players that trained more than 180 min/weeks were significantly better than players working below 180 min/week in both pre-lockdown moment (+9.01%; p = 0.007; d = 1.263) and post-lockdown moment (10.6%; p = 0.006; d = 1.323). Home-based training can be a good strategy to mitigate the detraining effects caused by a lockdown.