Effects of padel activity and proprioception training on soccer players in an off-season period

BACKGROUND

Off-season periods imply considerable changes in the fitness status of soccer players. So far, no studies evaluated the effects of proprioception-focused training during soccer off-season periods. In this work, we assessed how much some players' abilities (static and dynamic balance, reaction times, quickness, strength, and technical skills) were affected by proprioception training and padel activity during an off-season period of 12 weeks.

METHODS

Twenty-eight non-professional adult male soccer players were organized into three groups: a group carried out regular padel activity, ~2 h once a week. Another group underwent a regular proprioception training program, ~ 20 min, twice a week. The third group did not perform any specific activity (control). Static and dynamic balance, reaction times, quickness, strength, and technical skills were evaluated at three time-points: before starting, after 6 weeks, and after 12 weeks.

RESULTS

Both padel activity and specific proprioception training carried out for 12 weeks significantly improved players' monopodalic static balance with eyes open and dynamic balance. No significant effects of these training regimens were found on monopodalic static balance with eyes closed, visual and acoustic reaction times, acyclic quickness, and strength. Furthermore, proprioception training considerably improved technical skills.

CONCLUSIONS

Coaches may use padel activity and proprioception exercises for off-season programs featured by ease of execution, low training volume, and high compliance.

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.

Caffeinated Chewing Gum Improves Basketball Shooting Accuracy and Physical Performance Indicators of Trained Basketball Players: A Double-Blind Crossover Trial

(1) Background: This study investigated the effects of caffeinated chewing gum on the basketball-specific performance of trained basketball players. A double-blind, randomized crossover design was employed. (2) Methods: Fifteen participants (age: 20.9 ± 1.0 years; height: 180.9 ± 5.4 cm; mass: 77.2 ± 7.5 kg; training age: 8.2 ± 0.3 years) were recruited and divided into a caffeine trial (CAF) and placebo trial (PL). The participants in the CAF trial chewed gum containing 3 mg/kg of caffeine for 10 min, while those in the PL trial chewed a placebo gum without caffeine. Following a 15 min rest, all the participants completed basketball-specific performance tests. (3) Results: The free throw accuracy for the CAF trial was significantly higher than that for the PL trial (CAF: 79.0 ± 4.31%; PL: 73.0 ± 9.16%; p = 0.012; Cohen's d = 0.94). Additionally, the CAF trial demonstrated significantly better performance in the 20 m segmented dash (CAF: 2.94 ± 1.12 s; PL: 3.13 ± 0.10 s; p < 0.001; Cohen's d =1.8) and squats (p < 0.05), and exhibited lower fatigue indexes (CAF: 3.6 ± 1.6%; PL: 5.2 ± 1.6%; p = 0.009; Cohen's d =1.0). (4) Conclusions: These findings suggest that chewing gum containing 3 mg/kg of caffeine offers moderate-to-large improvements in key performance aspects relevant to professionally trained basketball players.

Supervised Offseason Training Programs are able to mitigate the Effects of Detraining in Youth Men Soccer Players Physical Fitness: A Randomized Parallel Controlled Study

This study aimed to analyze the effects of three off-season training programs on the aerobic capacity, countermovement jump (CMJ), and linear sprint performance of young male soccer players. The study employed a randomized multi-arm design, consisting of three experimental groups: i) a high-intensity interval training (HIIT) group; (ii) a plyometric jump training (PJT) group; and (iii) a HIIT+PJT group; and an inactive control group. Fifty-eight under-19 male soccer players (aged 17.6 ±0.6 years) were randomly assigned to participate in a 3-week offseason training program exclusively performing HIIT, PJT, or a combination of both, while the fourth group remained inactive. Players underwent assessments twice, using the Yo-Yo Intermittent Recovery Test - Level 1 (YYIRT), CMJ, and 30-meter linear sprint. Significant interactions between time and groups were found in CMJ (p<0.001), YYIRT (p<0.001), and 30-m sprint (p<0.001). Group*time interaction revealed that the control group was significantly different from HIIT (p<0.001), PJT (p<0.001), and HIIT+PJT (p<0.001) considering the CMJ. Moreover, the control group was significantly different from HIIT (p=0.037) in YYIRT. Finally, the control group was significantly different from HIIT (p=0.024), PJT (p<0.001), and HIIT+PJT (p=0.021) considering the 30-m sprint. In conclusion, off-season training programs are effective in significantly reducing declines in CMJ and sprint performance compared to maintaining training cessation. However, in the YYIRT, only HIIT seems to be significantly superior to maintaining inactivity. To mitigate aerobic performance declines, incorporating HIIT sessions twice weekly during the offseason is advisable. To enhance or maintain jump performance, integrating at least one session of PJT weekly is beneficial.

Seasonal variations in vitamin D do not change the musculoskeletal health of physically active ambulatory men with cerebral palsy: a longitudinal cross-sectional comparison study

Increased levels of vitamin D in the summer months from natural seasonal variations in sun exposure have been linked to improvements in musculoskeletal health and function in UK populations; however, studies have shown that differences in lifestyles because of disability can inhibit the natural vitamin D increase in these populations. We hypothesized that men with cerebral palsy (CP) will experience smaller increases in 25-hydroxyvitamin D (25(OH)D) from winter to summer and men with CP will not experience any improvements in musculoskeletal health and function during the summer. A longitudinal observational study in 16 ambulant men with CP aged 21.0 ± 1.3 years and 16 healthy, physical activity matched, typically developed controls aged 25.4 ± 2.6 years, completed assessments of serum 25(OH)D and parathyroid hormone during winter and summer. Neuromuscular outcomes included vastus lateralis size, knee extensor strength, 10-m sprint, vertical jumps, and grip strength. Bone ultrasounds were performed to obtain radius and tibia T and Z scores. Men with CP and typically developed controls showed a 70.5% and 85.7% increase in serum 25(OH)D from winter to summer months, respectively. Neither group showed seasonal effect on neuromuscular outcomes muscle strength, size, vertical jump, or tibia and radius T and Z scores. A seasonal interaction effect was seen in the tibia T and Z scores (P < .05). In conclusion, there were similar seasonal increases in 25(OH)D observed in men with CP and typically developed controls, but serum 25(OH)D levels were still considered insufficient to improve bone or neuromuscular outcomes.

Body Composition of Male Professional Soccer Players Using Different Measurement Methods: A Systematic Review and Meta-Analysis

The performance of male soccer players (MSP) depends on multiple factors such as body composition. The physical demands of modern soccer have changed, so the ideal body composition (BC) requirements must be adapted to the present. The aim of this systematic review and meta-analysis was to describe the anthropometric, BC, and somatotype characteristics of professional MSP and to compare the values reported according to the methods and equations used. We systematically searched Embase, PubMed, SPORTDiscus, and Web of Science following the PRISMA statement. Random-effects meta-analysis, a pooled summary of means, and 95% CI (method or equation) were calculated. Random models were used with the restricted maximum likelihood (REML) method. Seventy-four articles were included in the systematic review and seventy-three in the meta-analysis. After comparing the groups according to the assessment method (kinanthropometry, bioimpedance, and densitometry), significant differences were found in height, fat mass in kilograms, fat mass percentage, and fat-free mass in kilograms (p = 0.001; p < 0.0001). Taking into account the equation used to calculate the fat mass percentage and ∑skinfolds, significant differences were observed in the data reported according to groups (p < 0.001). Despite the limitations, this study provides useful information that could help medical technical staff to properly assess the BC of professional MSP, providing a range of guidance values for the different BC.

Changes in Body Composition and Motor Fitness of Young Female Volleyball Players in an Annual Training Cycle

BACKGROUND

Modern volleyball requires a high level of motor preparation, specific body build and optimal body composition.

OBJECTIVES

The aim of this study was to determine changes in body build, body composition and motor skills in young volleyball female players during an annual training cycle.

METHODS

The research group was comprised of 36 female athletes aged 14-16 years, who were monitored throughout a whole season using a longitudinal study design. Body composition was estimated by bioelectrical impedance analysis. Motor fitness was assessed with the following tests: vertical jumping tests (based on one-handed and two-handed reach, standing vertical jump and running vertical jump), standing long jump and 2 kg medicine ball throw. Measurements were carried out at the beginning of the preparatory period, after its completion, in the middle of the start period, at the end of the start period and during transition periods.

RESULTS

The study showed significant changes in body composition and motor fitness level during the annual training cycle. These changes differ in subsequent periods of the macrocycle. The most pronounced changes occurred after the preparatory period and concerned increases in fat-free mass, total water content and cell mass. A significant reduction in fat content was also noted at this point.

CONCLUSIONS

Systematic monitoring of morpho-functional changes in young female volleyball players over extended periods provides them a chance to maintain their optimal fitness level.

Analysis of the Effect of Injuries on Match Performance Variables in Professional Soccer Players: A Retrospective, Experimental Longitudinal Design

Background

Knowing the impact of injuries is essential for their adequate management during reconditioning programs.

Objective

This study aimed to analyze the changes in match performance parameters in professional soccer players after sustaining an injury, which was defined according to injury severity.

Methods

Two-hundred and seven injuries related to one hundred and sixty-one professional soccer players from the Spanish LaLiga™ were considered for this study. All the injuries were classified according to their severity as minor (from 4 to 7 missed days), moderate (from 8 to 28 missed days), and major (more than 28 missed days). Through Mediacoach^® videotracking system, time and external demand variables were collected and subsequently compared between pre-injury and return to play periods. The analyzed variables were (in m min⁻¹): relative distance covered (RD; total distance covered·min⁻¹), distance covered walking (0–6 km h⁻¹), distance covered jogging (6–12 km h⁻¹⁾, distance covered running (12–18 km h⁻¹), distance covered at intense running (18–21 km h⁻¹), distance covered at high-speed running (21–24 km h⁻¹), and sprinting (> 24 km h⁻¹) distance covered.

Results

Significant reductions in playing time after suffering moderate and major injuries were observed. Significant reductions after minor injuries were observed in jogging (> 6 km h⁻¹) and running (6–12 km h⁻¹), while significantly greater distances at intense running (18–21 km h⁻¹) and high-speed running (21–24 km h⁻¹) were covered by players who suffer major injuries. Finally, relevant decreases in the maximum speed achieved after moderate and major injuries were found.

Conclusions

In conclusion, this study shows the importance of high loads during reconditioning programs, as well as implementing strategies that allow reaching levels of maximum speed values after the return to play.

Innate immunity changes in soccer players after whole-body cryotherapy

Whole-body cryotherapy (WBC) consists of short exposure (up to 2–3 min) to dry air at cryogenic temperatures (up to -190 °C) and has recently been applied for muscle recovery after injury to reduce the inflammation process. We aimed to determine the impact of cryotherapy on immunological, hormonal, and metabolic responses in non-professional soccer players (NPSPs). Nine male NPSPs (age: 20 ± 2 years) who trained regularly over 5 consecutive days, immediately before and after each training session, were subjected to WBC treatment (WBC-t). Blood samples were collected for the evaluation of fifty analytes including hematologic parameters, serum chemistry, and hormone profiles. Monocytes phenotyping (Mo) was performed and plasmatic markers, usually increased during inflammation [CCL2, IL-18, free mitochondrial (mt)DNA] or with anti-inflammatory effects (IL2RA, IL1RN), were quantified. After WBC-t, we observed reduced levels of ferritin, mean corpuscular hemoglobin, mean platelet volume, testosterone, and estradiol, which however remain within the normal ranges. The percentage of the total, intermediates and non-classical Mo increased, while classical Mo decreased. CXCR4 expression decreased in each Mo subset. Plasma IL18 and IL2RA levels decreased, while IL1RN only exhibited a tendency to decrease and CCL2 showed a tendency to increase. Circulating mtDNA levels were not altered following WBC-t. The differences observed in monocyte subsets after WBC-t may be attributable to their redistribution into the surrounding tissue. Moreover, the decrease of CXCR4 in Mo subpopulations could be coherent with their differentiation process. Thus, WBC through yet unknown mechanisms could promote their differentiation having a role in tissue repair.

The soccer season: performance variations and evolutionary trends

The physiological demands of soccer challenge the entire spectrum of the response capacity of the biological systems and fitness requirements of the players. In this review we examined variations and evolutionary trends in body composition, neuromuscular and endurance-related parameters, as well as in game-related physical parameters of professional players. Further, we explore aspects relevant for training monitoring and we reference how different training stimulus and situational variables (e.g., competition exposure) affect the physiological and performance parameters of players. Generally, improvements of small magnitude in non- (non-CMJ) and countermovement-based jumps (CMJBased) and in the sprint acceleration (ACCPhase) and maximal velocity phase (MVPhase) are observed from start of preparation phase (PPS) to beginning of competition phase (BCP). A greater magnitude of increases is observed in physiological and endurance performance measures within this period; moderate magnitude in sub-maximal intensity exercise (velocity at fixed blood lactate concentrations; V2-4mmol/l) and large magnitude in VO2max, maximal aerobic speed (MAS) and intense intermittent exercise performance (IE). In the middle of competition phase (MCP), small (CMJBased and ACCPhase), moderate (non-CMJ; MVPhase; VO2max; sub-maximal exercise) and large (MAS and IE) improvements were observed compared to PPS. In the end of competition period (ECP), CMJBased and MVPhase improve to a small extent with non-CMJ, and ACCPhase, VO2max, MAS, sub-maximal intensity exercise and IE revealing moderate increments compared to PPS. Although less investigated, there are generally observed alterations of trivial magnitude in neuromuscular and endurance-related parameters between in-season assessments; only substantial alterations are examined for IE and sub-maximal exercise performance (decrease and increase of small magnitude, respectively) from BCP to MCP and in VO2max and IE (decrements of small magnitude) from MCP to ECP. Match performance may vary during the season. Although, the variability between studies is clear for TD, VHSR and sprint, all the studies observed substantial increments in HSR between MCP and ECP. Finally, studies examining evolutionary trends by means of exercise and competition performance measures suggests of a heightened importance of neuromuscular factors. In conclusion, during the preseason players "recover" body composition profile and neuromuscular and endurance competitive capacity. Within in-season, and more robustly towards ECP, alterations in neuromuscular performance seem to be force-velocity dependent, and in some cases, physiological determinants and endurance performance may be compromised when considering other in-season moments. Importantly, there is a substantial variability in team responses that can be observed during in-season. Consequently, this informs on the need to both provide a regular training stimulus and adequate monitorization throughout the season.

Effects of different training intensities in high-intensity interval training (HIIT) on maximal aerobic velocity, hematological and muscle-damage markers in healthy young adults

This study aimed to examine the effects of two high-intensity interval training programs (HIIT) on maximal aerobic velocity (MAV), hematological variations and muscle damage markers in young healthy adults. Twenty-nine male physical education students, aged 20.3 ± 3.3 years, volunteered to participate in this study, and were randomly assigned to a control group (CG, n = 9) or two intervention groups (group 1 or 2). Intervention group 1 (n = 10) exercised at 100% of their MAV (EG₁₀₀) while group 2 (n = 10) exercised at 110% MAV (EG₁₁₀). Before and after the eight week training program, blood samples were drawn at rest, before, and after an intermittent exercise. Aspartate aminotransferase (ASAT), alanine aminotransferase (ALAT), C reactive protein (CRP), creatine kinase (CK) concentrations and hematological parameters (white blood cells [WBC], monocytes [MO], lymphocytes [LY], neutrophil [NE]) and lactate dehydrogenase (LDH) were measured. Post-hoc tests showed that MAV was significantly higher in EG₁₁₀ compared to EG₁₀₀ after HIIT (p < 0.01, η_p² = 0.05), whilst ALAT, ASAT, and CPR were significantly lower (p < 0.01; 0.02 < η_p² < 0.11) in EG₁₁₀ compared to EG₁₀₀. Moreover, post-hoc tests indicated that LY decreased significantly (p < 0.001, η_p² = 0.21) only for EG₁₁₀. Furthermore, there were significant positive correlations for both EG₁₀₀ and EG₁₁₀ between MAV and ALAT (r = 0.66, p = 0.044 and r = 0.64, p = 0.041 respectively), CK (r = 0.67, p = 0.031 and r = 0.86, p = 0.030, respectively), LDH (r = 0.74, p = 0.014, and r = 0.071, p = 0.021, respectively). In addition, there was a significant positive correlation for both, EG₁₀₀ and EG₁₁₀ between MAV and LY (r = 0.79, p < 0.01; r = 0.72, p < 0.05, respectively). Concerning the relationship between MAV and NE, there was a significant positive correlation (r = 0.66; p < 0.05) only for EG₁₁₀. Findings from this study revealed that HIIT at 110% MAV was more efficient to improve MAV and reduce muscle damage. In addition, we observed significant associations between performance improvements (MAV) and markers of muscle damage.

Can high-intensity interval training and small-sided games be effective for improving physical fitness after detraining? A parallel study design in youth male soccer players

Background

The aim of this study was two-fold: (i) analyze the within-group physical fitness adaptations promoted by a detraining period (4 weeks) followed by an intervention period (4 weeks) using small-sided games (SSGs) or running-based high intensity interval training (HIIT); and (ii) analyze the between-group differences aiming to identify the effectiveness of each training intervention on the physical fitness of youth male soccer players.

Methods

This study followed a randomized parallel study design. Forty male soccer players (age: 16.4 ± 0.5 years old) were assessed three times: (i) baseline; (ii) after 4 weeks of detraining; and (iii) after a retraining period of 4 weeks. After returning from detraining, players were randomized to an SSG-based training intervention (n = 20) or running-based HIIT (n = 20). Interventions lasted 4 weeks, with a training frequency of three sessions per week. At all timepoints, players were assessed by: (i) anthropometry (height, body mass, fat mass (FM)), countermovement jump (CMJ), standing broad jump (SBJ), triple hop jump (THJ), linear sprint test (5-, 10-, and 20-m), zig-zag test with (ZZwB) and without (ZZwoB) ball, three corner run test (3CRT), Y-balance test and the Yo-Yo intermittent recovery test level 1 (YYIRT). Mixed ANOVA (time * group) was conducted for testing interactions between the three timepoints of repeated measures and the two groups. Effect size (ES) for pairwise comparisons was calculated using Cohen's.

Results

Between-group analysis revealed significantly smaller SBJ (t = -2.424, p = 0.020, d = -0.767 small ES) and THT (t = -4.353, p < 0.001, d = -1.376 large ES) in the SSG group after the retraining period. At the same time, SSG presented significantly greater FM after retraining compared to HIIT (t = 3.736, p < 0.001, d = 1.181 large ES). Additionally, SSG had significantly smaller values than HIIT in the ZZwB (t = -3.645, p < 0.001, d = -1.153 large ES), but greater times in the ZZwoB (t = 2.679, p = 0.011, d = 0.847 large ES) and 3CRT (t = 3.126, p = 0.003, d = 0.989 large ES).

Conclusions

Although SSG and HIIT interventions improved physical fitness outcomes after a period of detraining, they were not able to effectively restore body composition, CMJ, 20-m sprint, ZZwB, and YYIRT compared with the baseline assessments (before detraining). Only HIIT was significantly effective for restoring SBJ, short linear sprin speed, and change-of-direction compared with baseline. HIIT was also significantly better than SSG in improving SBJ and ZZwoB. Although the small sample, the non determination of maturation status and the need to be cautious regarding generalization, HIIT appears to be more beneficial than SSG after a detraining period for recovery of body composition and physical fitness qualities in this specific context of youth soccer players.

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.

Effects of COVID-19 Lockdown on Physical Performance, Sleep Quality, and Health-Related Quality of Life in Professional Youth Soccer Players

Background

In March 2020, the COVID-19 outbreak led to the declaration of a pandemic. The accompanying restrictions on public life caused a change in the training routines of athletes worldwide. The present study aimed to investigate the effects of a 13-week supervised home training program on physical performance, sleep quality, and health-related quality of life in professional youth soccer players during the first COVID-19 lockdown in Germany.

Methods

Eight professional soccer players (age range 16–19; height: 1.81 ± 0.07 m; body weight: 72.05 ± 6.96 kg) from a Bundesliga team in Germany participated in this study. During the lockdown, they trained 5–6 days per week with home-based training plans and were monitored via tracking apps and video training. To determine the effects of home training, measurements were taken before (March 2020) and after (June 2020) the home training period. Bioelectrical impedance analysis was used to determine body composition, and an isokinetic strength test and a treadmill step test, including lactate measurements, were used to measure physical performance. Two questionnaires were responded to in order to assess health-related quality of life [Short-Form 36 Health Survey (SF-36)] and sleep quality (Pittsburgh Sleep Quality Index).

Results

When comparing measurements before and after the home training period, we observed significant increases in the following variables: body weight (72.05 ± 6.96 kg vs. 73.50 ± 6.68 kg, p = 0.034), fat mass (11.99 ± 3.13 % vs. 13.98 ± 3.92 %, p = 0.030), body mass index (22.04 ± 0.85 kg/m2 vs. 22.49 ± 0.92 kg/m2, p = 0.049), and mental health component summary score (MCS) of the questionnaire SF-36 (53.95 ± 3.47 vs. 58.33 ± 4.50, p = 0.044). Scores on the general health (77.88 ± 14.56 vs. 89.75 ± 13.76, p = 0.025) and mental health (81.50 ± 9.30 vs. 90.00 ± 11.71, p = 0.018) subscales of the SF-36 also increased significantly.

Conclusion

The COVID-19 lockdown led to an increase in body composition parameters and showed an improvement in the MCS and scores on the general and mental health subscales of the SF-36. Physical performance and sleep quality could be maintained during the home training period. These observations may help trainers for future training planning during longer interruptions in soccer training.

Relationships between Fitness Status and Blood Biomarkers in Professional Soccer Players

Background

Physical conditions are recognized to be optimal after the pre-season (PS) phase in professional sports. Given that blood measures may also reveal variations, which in turn, may present associations with fitness changes.

Objective

The aim of this study is to test the changes of blood markers and physical fitness outcomes at the beginning and following the PS phase. Additionally, we aimed also to analyze the associations of training adaptations between blood markers and the physical fitness measures. Methodology. 25 professional male soccer players (28.1 ± 4.6 years old, 2.0 ± 7.8 kg, and 176.7 ± 4.9 cm) were assessed for hematological and biochemical parameters, and physical fitness measures in the baseline and after the phase of PS.

Results

Increases in platelets were observed after the PS phase (p = 0.001, η2 = 0.39). Regarding the biochemical parameters, significant increases between PS were found for creatinine (Cre) (p = 0.001, η2 = 0.66), alkaline phosphatase (ALP) (p = 0.001, η2 = 0.79), C-Reactive Protein (CRP) (p = 0.001, η2 = 0.74), cortisol (C) (p = 0.001, η2 = 0.63), and testosterone (T) (p = 0.001, η2 = 0.76), whereas significant decreases were found for albumin (Alb) (p = 0.004, η2 = 0.29), and calcium corrected (Ca Corr.) (p = 0.002, η2 = 0.32). Moderate correlations were found between albumin and the 5-meter linear sprint split (r = -0.44 (95%CI: -0.71; -0.05)) and CRP (r = -0.48 (95%CI: -0.74; -0.10)). Moderate correlations were found between VAMEVAL and hemoglobin (r = 0.44 (95%CI: 0.05; 0.71)).

Conclusions

The overall physical fitness measures improved after the PS phase. Also, significant variations (decreases/increases) were observed for the case of biomchemical and hematological outcomes. Coaches should carefully consider the adaptative changes observed in blood parameters as the changes in whole organism and metabolism after specific critical phases as the PS in professional players. Thus, optimal management of stimulus/recovery can be warranted to minimize illness and injury rate and to follow the direction and dynamics of adaptative changes.

Gastrointestinal Hormones, Morphological Characteristics, and Physical Performance in Elite Soccer Players

PURPOSE

To determine the relationship between gastrointestinal hormones (leptin, glucagon-like peptide-1), ghrelin, cholecystokinin, peptide YY, morphological characteristics, and physical performances in elite soccer players.

METHODS

Q2 Twenty-two elite male soccer players (age = 23.1 [2.7] y, height = 177.0 [0.1] cm, weight = 70.2 [2.9] kg, body mass index = 22.1 [1.8] kg/m2) completed 3-day food records each week during the 5-week training period. Blood samples were drawn after an overnight fast before and after preseason training to assess gastrointestinal hormones (leptin, glucagon-like peptide-1, ghrelin, cholecystokinin, and peptide YY). Continuous analysis of the training load was used during the training period. Preintervention and postintervention tests assessed jumping (countermovement jump), sprinting (10, 20, and 30 m), and endurance fitness (the Yo-Yo Intermittent Recovery Test Level 1 [YYIRT1]) levels.

RESULTS

Preseason training decreased body mass index (P = .001; effect size [ES] = 0.183) and body fat percentage (P = .001; ES = 0.516). There were increases in countermovement jump (P = .032; ES = 0.215), 20- (P = .016; ES = 0.195) and 30-m sprints (P = .001; ES = 0.188), and YYIRT1 performance (P = .001; ES = 0.9). Levels of cholecystokinin, peptide YY, and ghrelin did not change during preseason training, although changes in leptin (P = .001; ES = 0.41) and glucagon-like peptide-1 levels (P = .039; ES = 0.606) were recorded. Leptinemia correlated with anthropometric parameters (body mass index, r = .77, P = .001; percentage of body fat,r = .67, P = .006) and the total distance covered during the YYIRT1 (r = -.54; P = .03).

CONCLUSION

Changes in morphological parameters and physical performance in elite-level male soccer players are related to variations in selected gastrointestinal hormones.

Biological, Psychological, and Physical Performance Variations in Football Players during the COVID-19 Lockdown: A Prospective Cohort Study

This prospective cohort study aimed to evaluate whether COVID-19 lockdown caused biological, psychological, and/or physical performance variations in footballers. We compared the 2018/2019 and 2019/2020 seasons evaluating the plasma volume, hematological parameters, iron/ferritin, creatine kinase, vitamin D, cortisol, testosterone, and physiological state of players of the Italian football major league (Serie A). Measurements were performed before the preparatory period (T0), at the beginning (T1) and in the middle (T2) of the championship, and in March (T3) and at the end of season (T4). The results showed that in the 2019/2020 season affected by the lockdown, the weight, BMI, and fat mass percentage were higher than in the previous season. Hematocrit, hemoglobin, red blood cells, and ferritin decreased during both seasons, more significantly than in the regular season. During both seasons, creatine kinase increased from T2 whilst iron concentrations decreased in T3. Testosterone increased in both seasons from T0 to T3 and returned to initial levels at T4; cortisol increased in T2 and T3 during the 2018/2019 season but not during the COVID-19 season. Physical performance tests revealed differences associated with lockdown. Thus, although from a medical point of view, none of the evaluated changes between the two seasons were clinically relevant, training at home during lockdown did not allow the players to maintain the jumping power levels typical of a competitive period.

The impact of COVID-19 lockdown on professional soccer players' body composition and physical fitness

During the COVID-19 lockdown, professional soccer players ceased their regular team training sessions and were provided with exercise programs to follow independently. This investigation assessed the impact of a 7-week COVID-19 lockdown and home-based individual physical training on professional soccer players’ body composition and physical fitness. The study consisted of nineteen division 1 elite soccer players (age 27.68 ± 5.99 years, height 178.47 ± 5.44 cm) and compared the anthropometric and physical fitness parameters obtained post-transition period to those obtained post-COVID-19 lockdown. The statistical analysis indicated that body fat percentage was significantly higher after the lockdown period [t(18) = -5.59, p < 0.01, d = 0.56]. Furthermore, VO_2max [t(17) = -11.54, p < 0.01, d = 0.57] and running time [t(17) = 3.94, p < 0.01, d = 0.76] values were significantly higher after the COVID-19 lockdown than those obtained after the transition period. In addition, significantly higher level of performance was demonstrated on squat jump [t(18) = -4.10, p < 0.01, d = 0.30], countermovement jump [t(18) = -7.43, p < 0.01, d = 1.11] and sit and reach tests [t(19) = -5.33, p < 0.01, d = 0.32]. Concurrently, lower body strength was indicated to be significantly greater (p < 0.01) following the COVID-19 lockdown. The training protocol provided during the confinement, due to the COVID-19 outbreak, was effective in keeping physical fitness at a significantly higher level compared to the transition period. Coaches and trainers are encouraged to examine the effectiveness of this protocol, as it may help them develop effective periodization programs during the transition period. This protocol may aid in the development of effective periodization programs that require minimal equipment and can be followed in similar situations.

Blood Biomarkers Variations across the Pre-Season and Interactions with Training Load: A Study in Professional Soccer Players

Background: Pre-season training in soccer can induce changes in biological markers in the circulation. However, relationships between chosen hematological and biochemical blood parameters and training load have not been measured. Objective: Analyze the blood measures changes and their relationships with training loads changes after pre-season training. Methodology: Twenty-five professional soccer players were assessed by training load measures (derived from rate of perceived exertion- known as RPE) during the pre-season period. Additionally, blood samples were collected for hematological and biochemical analyses. Results: For hematological parameters, significant increases were found for platelets (PLT) (dif: 6.42; p = 0.006; d = -0.36), while significant decreases were found for absolute neutrophils count (ANC) (dif: -3.98; p = 0.006; d = 0.11), and absolute monocytes count (AMC) (dif: -16.98; p = 0.001; d = 0.78) after the pre-season period. For biochemical parameters, there were significant increases in creatinine (dif: 5.15; p = 0.001; d = -0.46), alkaline phosphatase (ALP) (dif: 12.55; p = 0.001; d = -0.84), C-reactive protein (CRP) (dif: 15.15; p = 0.001; d = -0.67), cortisol (dif: 2.85; p = 0.001; d = -0.28), and testosterone (dif: 5.38; p = 0.001; d = -0.52), whereas there were significant decreases in calcium (dif: -1.31; p = 0.007; d =0.49) and calcium corrected (dif: -2.18; p = 0.015; d = 0.82) after the pre-season period. Moreover, the Hooper Index (dif: 13.22; p = 0.01; d = 0.78), and all derived RPE measures increased after pre-season period. Moderate-to-very large positive and negative correlations (r range: 0.50-0.73) were found between the training load and hematological measures percentage of changes. Moderate-to-large positive and negative correlations (r range: 0.50-0.60) were found between training load and biochemical measures percentage of changes. Conclusions: The results indicated heavy physical loads during the pre-season, leading to a decrease in immune functions. Given the significant relationships between blood and training load measures, monitoring hematological and biochemical measures allow coaches to minimize injury risk, overreaching, and overtraining.

Hematology, Hormones, Inflammation, and Muscle Damage in Elite and Professional Soccer Players: A Systematic Review with Implications for Exercise

BACKGROUND

Knowledge of the long-term effects of soccer training on hematological, hormonal, inflammatory, and muscle damage markers and physical performance may help to better design strength and conditioning programs for performance development and injury prevention for the individual player and the team.

OBJECTIVES

The aim of this systematic review was to summarize and discuss evidence on the long-term effects of soccer training on selected hematological, hormonal, inflammatory, and muscle damage markers and physical performance in elite and professional soccer players. A second goal was to investigate associations between selected physiological markers and measures of performance.

METHODS

Adhering to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines, a systematic literature search was conducted in four electronic databases (PubMed, ISI Web of Knowledge, Web of Science, and SPORTDiscus) from inception until August 2020 to identify articles related to soccer training effects. To be included in this systematic review, studies had to examine male elite (national level) and/or professional (international level) soccer players aged > 17 years and a soccer training period > 4 weeks, and report outcomes related to hematological, hormonal, inflammatory, muscle damage, and performance markers.

RESULTS

The search syntax initially identified 2420 records. After screening titles, abstracts, and full texts, 20 eligible studies were included in this systematic review, with training durations lasting between 4 and 18 weeks in 15 studies, around 6 months in four studies, and around 1 year in one study. Effects of long-term soccer training revealed parameter-specific increases or decreases in hematological, hormonal, inflammatory, and muscle damage markers and physical performance. Two studies showed a moderate increase in hematological markers such as hemoglobin (effect size [ES] = 0.67-0.93). Parameter-specific changes were noted for hormonal markers in the form of increases for total testosterone (ES = 0.20-0.67) and free testosterone (FT) (ES = 0.20-0.65) and decreases for cortisol (ES =  - 0.28 to - 1.31). Finally, moderate to very large increases were found for muscle damage markers such as creatine kinase (ES = 0.94-6.80) and physical performance such as countermovement jump (CMJ) height (ES = 0.50-1.11) and squat jump (SJ) height (ES = 0.65-1.28). After long-term periods of soccer training, significant positive correlations were found between percentage change (Δ%) in FT and Δ% in CMJ height (r = 0.94; p = 0.04) and between Δ% in total testosterone/cortisol (TT/C) ratio and Δ% in SJ (r = 0.89; p = 0.03).

CONCLUSIONS

Findings suggest that long-term soccer training induces increases/decreases in hematological, hormonal, inflammatory, and muscle damage markers and physical performance in male elite and professional soccer players. These fluctuations can be explained by different contextual factors (e.g., training load, duration of training, psychological factors, mood state). Interestingly, the observed changes in hormonal parameters (FT and TT/C) were related to vertical jump performance changes (e.g., CMJ and SJ). Anabolic hormones and TT/C can possibly be used as a tool to identify physical performance alteration after long-term soccer training.

Blood and performance adaptations to individual training load in professional soccer: a team study

PURPOSE

The aim of this study was to describe seasonal changes in iron storage, hormonal status and functional capacity in relation to accumulated training load in a professional male soccer team.

METHODS

Resting blood samples, countermovement jump (CMJ) and aerobic capacity (45-15 test) were collected over a 6-month period from the start of the preparatory period to the middle-season (E1 to E4) in a professional male soccer team (n=15 outfield players). External training load was regularly quantified using a wearable 10-Hz global positioning system.

RESULTS

One player systematically showed reduced iron storage throughout the season (ferritin<110 μg·l-1, hemoglobin<14 g·dl-1). No significant differences in blood and performance parameters were observed throughout the season (P>0.05). However, accumulated total distance and high-intensity distance (above maximal aerobic speed) from E1 to E3 were negatively correlated to changes in haematocrit, hemoglobin and red blood cells (r=-0.85 to -0.67; P<0.05) and positively to changes in ferritin (r=0.63-0.69; P<0.05). Additionally, high-intensity distance covered between E1 and E3 was negatively correlated to changes in testosterone concentrations (r [95%CI]=-0.71 [-0.93; -0.15]; P=0.021).

CONCLUSIONS

Resting blood parameters and functional capacity of male soccer players appeared to be stable throughout the early competitive period. However, iron storage and hormonal status are likely to be affected by accumulated high-intensity activity performed during practice and competition. Practitioners involved with GPS-based TL monitoring could consider the accumulated amount of high-intensity activity to inform medical staffs about possible changes in oxygen-carrying capacity and anaerobic overtraining.

Maximal Strength, Sprint, and Jump Performance in High-Level Female Football Players Are Maintained With a Customized Training Program During the COVID-19 Lockdown

INTRODUCTION

The COVID-19 outbreak with partial lockdown has inevitably led to an alteration in training routines for football players worldwide. Thus, coaches had to face with the novel challenge of minimizing the potential decline in fitness during this period of training disruption.

METHODS

In this observational pre- to posttest study involving Norwegian female football players (18.8 ± 1.9 years, height 1.68 ± 0.4 m, mass 61.3 ± 3.7 kg), we investigated the effects of a prescribed home-based and group-based intervention, implemented during the COVID-19 lockdown, on maximal muscular force production and high velocity variables. Specifically, maximal partial squat strength one repetition maximum (1RM), counter movement jump (CMJ) and 15 m sprint time were assessed 1 week prior to the lockdown and 12 weeks after the onset of lockdown. We also collected training content and volume from the prescribed training program and self-reported perceived training quality and motivation toward training.

RESULTS

We observed no change in 1RM [pretest: 104 ± 12 kg, posttest: 101 ± 11 kg (P = 0.28)], CMJ height [pretest: 28.1 ± 2.3 cm, posttest: 26.8 ± 1.9 (P = 0.09)], and 15 m sprint time [pretest: 2.60 ± 0.08 s, posttest: 2.61 ± 0.07 s (P = 0.52)].

CONCLUSION

Our findings suggest that a prescribed home-based and group-based intervention with increased training time devoted to strength, jump, and sprint ability, and regulated to obtain a sufficient infection control level is feasible and effective to preserve strength, jumping, and sprinting abilities of high-level female football players during a ∼ 3-month period of a pandemic-induced lockdown.

Physical fitness changes among amateur soccer players: effects of the pre-season period

Study aim: To assess changes in physical fitness of amateur soccer players after a pre-season training period and baseline fitness dependencies.

Material and methods: Twenty-one amateur soccer players were assessed during the pre-season. The following physical variables were assessed before and after a two-month pre-season training period: (i) cardiorespiratory fitness, (ii) strength and power, and (iii) change of direction (COD).

Results: Significant decreases were found for countermovement jump (CMJ) (p < 0.001; d = 1.161), drop jump (DJ) (p = 0.014; d = 0.958), and horizontal jump (HJ) (p = 0.042; d = 0.640), while no significant changes were found for the overall variables from the beginning to the end of pre-season. Fit players revealed significant decreases for CMJ (p = 0.002; d = –2.495), DJ (p = 0.004; d = –1.760), HJ (p = 0.028; d = –1.005), COD deficit (p = 0.034; d = 1.013), and maximal aerobic speed (MAS) (p = 0.026; d = –4.053). No significant changes were found for unfit players.

Conclusions: Amateur soccer coaches should consider assessing physical qualities at the beginning of pre-season and use the free-of-charge monitoring tools such as session-rate of perceived exertion (s-RPE) during the training process.

Detrimental Effects of the Off-Season in Soccer Players: A Systematic Review and Meta-analysis

BACKGROUND

The off-season period in soccer leads necessarily to changes in fitness status. However, there is a lack of systematization that allows identifying the magnitude of these changes in groups participating in off-season training programs compared with those subjected to training cessation.

OBJECTIVE

This systematic review with meta-analysis was conducted to assess the effects of training cessation in off-season training programs on men soccer players' body fat, maximal oxygen uptake (VO_2max), yo-yo intermittent recovery test (YYIRT), vertical jump, sprinting time, and repeated-sprint ability.

METHODS

To qualify for inclusion in the systematic review, studies must have included: (1) a detraining period of ≥ 2 weeks; (2) controlled trials or cohorts of healthy men soccer players with no restriction on age; and (3) a pre-post training cessation or off-season training programs measure of body fat (%), VO_2max (mL kg^-1 min^-1), YYIRT performance (meters), vertical jump (height), sprinting (time), and repeated-sprint ability (total time).

RESULTS

The electronic search yielded 563 articles, and 12 were subsequently included. Significant (all p < 0.05) detrimental training cessation effects were noted for body fat (ES = 0.26), VO_2max (ES = - 1.48), YYIRT (ES = - 0.46), vertical jump (ES = - 0.81), and repeated-sprint ability (ES = 0.68). Similarly, significant (all p < 0.05) detrimental off-season training programs effects were noted for body fat (ES = 0.26), VO_2max (ES = - 0.48), vertical jump (ES = - 0.51), and sprinting time (ES = 0.86). When training cessation and off-season training programs effects were compared, greater detrimental effects were noted after training cessation for VO_2max (p = 0.002) and repeated-sprint ability (p < 0.001).

CONCLUSIONS

Detrimental effects on body composition and physical fitness were observed after both training cessation and off-season training programs. However, off-season training programs seem to ameliorate such detrimental effects on VO_2max and repeated-sprint ability to some extent. The results presented here call for the implementation of more effective off-season training programs among male soccer players.

Changes in markers of body composition of professional male soccer players during pre-season

To evaluate changes achieved in whole-body and regional (upper limbs, lower limbs, and trunk) estimates of body composition, twenty professional male soccer players (7 defenders, 7 midfielders, 6 forwards) underwent dual-energy x-ray absorptiometry (DXA) analysis at the beginning and end of pre-season. Measures included: mass, fat mass (FM), fat-free mass (FFM), and body fat per cent (BF%). Players' activity during on-field training sessions was monitored using Global Positioning System (GPS) units, with GPS data used to obtain estimations of energy expenditure (EE). Whole-body mass remained unchanged across the pre-season. Moderate significant increases and decreases were achieved in whole-body FFM (Pre: 59.58 ± 5.27 kg; Post: 60.61 ± 5.18 kg; p = 0.001; d = 0.87) and FM (Pre: 10.60 ± 1.88 kg; Post: 9.56 ± 1.81 kg; p = 0.001; d = 0.85), respectively. Moderate significant decreases were achieved in whole-body BF% (Pre: 14.4 ± 2.3%; Post: 12.9 ± 2.0%; p < 0.001; d = 0.94). No significant inter-positional differences were observed for the changes achieved in any global or regional estimate of body composition. Total EE was significantly correlated with ΔFM (r = 0.65, p = 0.002), ΔFFM (r = 0.46, p = 0.03), and ΔBF% (r = 0.67, p = 0.002). The total EE of pre-season training accounted for 42%, 21%, and 45% of the variance in ΔFM, ΔFFM, and ΔBF%, respectively. These findings suggest that the pre-season period is a suitable time for initiating favourable alterations in body composition following the off-season in elite soccer players.

Performance changes during the off-season period in football players - Effects of age and previous hamstring injury

The aims of this study were to investigate changes in selected performance measures during an off-season period, their association, and the potential role of age and previous hamstring injury in semi-professional and amateur football players. Seventy-four male players (age: 25 ± 4 years, stature: 178.0 ± 6.6 cm, body mass: 74.9 ± 8.1 kg) were assessed at the beginning and end of the off-season summer-period for sprint, change-of-direction performance and eccentric hamstring strength. Small to medium increases in sprint times were observed at 5 (d = 0.26, p = 0.057), 10 (d = 0.42, p < 0.001) and 30 m (d = 0.64, p < 0.001). Small (d = -0.23, p = 0.033) improvements were observed for COD performance, and no changes in eccentric hamstring strength (d = 0.10, p = 0.317). The changes in the outcomes were not affected by age (p = 0.449 to 0.928) or previous hamstring injury (p = 0.109 to 0.995). The impaired sprint performance was not related to changes in eccentric hamstring strength (r = -0.21 to 0.03, p = 0.213 to 0.856), instead, changes in COD performance were associated with changes in eccentric hamstring strength (r = -0.42, p = 0.008).

Seasonal Repeated Sprint Ability With Change of Direction Variations in U17 and U20 Elite Brazilian Soccer Players: A Comparative Study

Jorge, G, Garrafoli, MT, and Cal Abad, CC. Seasonal repeated sprint ability with change of direction variations in U17 and U20 elite Brazilian soccer players: a comparative study. J Strength Cond Res 34(5): 1431-1439, 2020-This study aimed to describe seasonal variations of repeated sprint with change-of-direction ability in young elite Brazilian soccer players. The Bangsbo sprint test (BST) was performed by 21 under-17 (U17) (176.9 cm; 68.2 kg) and 22 under-20 (U20) athletes (178.7 cm, 74.4 kg) at the start, middle, and end of the season. The fatigue index (FI) was calculated in seconds and in percentage of decrease (%D) for comparisons. Both age categories showed higher BST performance in the middle and end compared with the start of the season (p ≤ 0.05). The U20 players performed better at the start than the U17 players. The U17 soccer players showed higher FI at the start and in the middle in comparison with the U20 players (p ≤ 0.05). They also showed lower FI at the end of the season in comparison with the start and middle of the season (p ≤ 0.05). The U20 players showed significant reductions in the FI in the middle and at the end in comparison with the start of the season (p ≤ 0.05). Only the U17 soccer players showed lower %D at the end in comparison with the start of the season (p ≤ 0.05). To summarize, both U17 and U20 players performed BST poorly at the start, increased the BST performance until the middle, and maintained the BST performance until the end of the season. A difference in the magnitude of enhancement was observed between U17 and U20 soccer players, which was found to be dependent on the initial values. Finally, the mathematical model to calculate the FI requires caution.

The effects of detraining and retraining periods on fat-mass and fat-free mass in elite male soccer players

The aim of the study was to examine the effects of a detraining period (DTP) (i.e., off-season) with an individually prescribed training program, and a retraining period (RTP) (i.e., pre-season) combining soccer and flywheel-based strength training on fat-free mass (FFM) and fat-mass (FM) in 10 elite professional male soccer players. The present study used a controlled repeated-measures research design to investigate the changes in FFM and FM using dual-energy X-ray absorptiometry. Whole body %FM increased (effect size (ES) = 0.87 ± 0.46) and FFM reduced after DTP (ES = −0.30 ± 0.19), returning to values comparable to the end of the previous season after RTP. At regional levels, arms, legs, and trunk %FM increased (ES = from 0.42 to 1.29) while trunk-FFM was reduced (ES = −0.40 ± 0.26) after DTP, returning to the values observed at the end of the previous season after RTP. Legs-FFM did not change after DTP, with a substantial increase after RTP in comparison with pre-season values (ES = 0.34 ± 0.29 and 0.53 ± 0.36 for the right and left leg, respectively). Despite the small sample size of the present study, the findings indicate that elite soccer players can be allowed 2 weeks of rest during a five-week DTP, since the changes in %FM and FFM were relatively small, and FM and FFM returned to the optimal initial values for competition after the proposed RTP during the pre-season.