Examination of the validity of the Injury-Psychological Readiness to Return to Sport (I-PRRS) scale in male professional football players: A worldwide study of 29 professional teams.

Perceived confidence is an important dimension of an athlete's psychological readiness to return-to-play. However, there is no established and validated tool to evaluate confidence in professional football. This study aimed to provide preliminary evaluation of the internal structure of the Injury-Psychological Readiness to Return-to-Sport scale (I-PRRS) in a cohort of injured male professional footballers. Over an 18-month period, 29 teams from 17 leagues participated. Players sustaining injuries eliciting ≥ 3 weeks' time-loss were recruited. Cross culturally adapted to 4 further languages, the I-PRRS was administered on two occasions: 1) day before returning-to-training and 2) day before returning-to-match-play. In total, 113 injuries were recorded with 96 completed I-PRRS data sets collected. Confirmatory factor analysis indicated the I-PRRS was a unidimensional scale, with all items measuring the same construct. The scale demonstrated good internal consistency (ω = .88). When examining longitudinal invariance of the I-PRRS across administration time-points, indices of model fit supported scalar invariance. There was preliminary evidence of good internal structure for the I-PRRS in professional male footballers. However, before further research involving the I-PRRS can be endorsed, efforts to confirm or refute empirical developments pertaining to psychological readiness are necessary.

Return-to-Play Practices Following Hamstring Injury: A Worldwide Survey of 131 Premier League Football Teams.

PURPOSE: Return-to-play (RTP) is an on-going challenge in professional football. Return-to-play related research is increasing. However, it is unknown to what extent the recommendations presented within research are being implemented by professional football teams, and where there are gaps between research and practice. The purposes of this study were (1) to determine if premier-league football teams worldwide follow a RTP continuum, (2) to identify RTP criteria used and (3) to understand how RTP decision-making occurs in applied practice. METHODS: We sent a structured online survey to practitioners responsible for the RTP programme in 310 professional teams from 34 premier-leagues worldwide. The survey comprised four sections, based on hamstring muscle injury: (1) criteria used throughout RTP phases, (2) the frequency with which progression criteria were achieved, (3) RTP decision-making process and (4) challenges to decision-making. RESULTS: One-hundred and thirty-one teams responded with a completed survey (42%). One-hundred and twenty-four teams (95%) used a continuum to guide RTP, assessing a combination of clinical, functional and psychological criteria to inform decisions to progress. One-hundred and five (80%) teams reported using a shared decision-making approach considering the input of multiple stakeholders. Team hierarchy, match- and player-related factors were common challenges perceived to influence decision-making. CONCLUSIONS: General research recommendations for RTP and the beliefs and practices of practitioners appear to match with, the majority of teams assessing functional, clinical and psychological criteria throughout a RTP continuum to inform decision-making which is also shared among key stakeholders. However, specific criteria, metrics and thresholds used, and the specific involvement, dynamics and interactions of staff during decision-making are not clear.

Stability in post-seasonal hematological profiles in response to high-competitive match-play loads within elite top-level European soccer players: implications from a pilot study.

INTRODUCTION: The stability of hematological status indices is a key determinant of optimal sport performance. The capacity to monitor hematological behaviors of elite soccer players may better explain the stresses placed upon physiological systems and the potential decrements in performance and physical capacity. The primary aim of this investigation was to examine the post-seasonal hematological status of professional top-level soccer players in response to seasonal match-play and training demands, in terms of the training practices, intensity, and loadings that they experience before, during, and after each season. METHODS: Seventeen male elite European soccer players participated in the study (mean±SD: age 26.8±4.6 years, weight 78.1±5.7 kg, height 182.4±4.8 cm, body fat 9.8%±2.9%, and maximal aerobic capacity 56.5±4.2 mL kg-1 min-1). The season culminated in 74 competitive matches including domestic, Champions League, and UEFA Cup matches. Blood samples were collected between 9:00 and 10:30 am after an overnight fast (~10 hours), 72 hours post conclusion of the final match of the competitive season. RESULTS: Near-perfect correlations between white blood cells, neutrophils, the period of season, training availability, and total competitive minutes were found. When adjusting for all the confounding variables, a stability of the hematological profile was noticed. Only mean cell volume and mean cell hemoglobin values were associated with the requirement for elite European soccer teams to fulfill excessive competitive loadings. The reported lower mean cell volume and mean cell hemoglobin values may highlight the accumulative effects of seasonal training and match-play demands. CONCLUSION: Regular blood testing could identify the need for both squad rotation and the implementation of interventions to assist in stabilizing transient hematological behaviors in order to optimize performance and sports output.

Seasonal Body Composition Variation Amongst Elite European Professional Soccer Players: An Approach of Talent Identification.

The primary aim of the investigation was to study the seasonal changes in body composition in elite European soccer players and identify key playing positional differences. Twenty-two players (age = 24 ± 3.7 years, body height = 180.45 ± 5.12 cm, body mass = 76.66 ± 5.34 kg) were tested. Players' mass (kg), lean body mass (LBM), fat free mass (FFM), fat mass (FM), muscle girths (MG) and sum of 8 skinfolds (mm) were measured across 5 time points (T0 = Start of pre-season training; T1 = End of pre-season training; T2 = Mid-season; T3 = End of mid-season break; T4 = End of season). Players were divided into their tactical positional roles for analysis. The specific positions they were divided into included defenders (n = 8), midfielders (n = 8) and forwards (n = 6). Assessment of training and matchplay exposure were also recorded. Sites-4, Sites-7, Sites-8 and Fat Mass decreased dramatically from T0 to T1 and T2 in all playing positions (p < 0.01), while no remarkable differences were found between T2, T3 and T4. Except for defenders, calf girth and lean mass were higher in T2, T3 and T4 compared to T0 and T1 (p < 0.01). Midfielders were found to be leaner than forwards and defenders in all data collection time point sessions. Defenders showed higher values in calf girth and lean body mass than midfielders and forwards. It can be concluded from this investigation that there are large variances n positional body composition profiles amongst professional European soccer players. Furthermore, significant changes are prevalent and occur across the season from LBM, FFM, MG and skinfold assessment amongst European elite level soccer players.

High-Intensity Training and Salivary Immunoglobulin A Responses in Professional Top-Level Soccer Players: Effect of Training Intensity.

Owen, AL, Wong, DP, Dunlop, G, Groussard, C, Kebsi, W, Dellal, A, Morgans, R, and Zouhal, H. High-intensity training and salivary immunoglobulin A responses in professional top-level soccer players: Effect of training intensity. J Strength Cond Res 30(9): 2460-2469, 2016-This study aimed (a) to test the hypothesis that salivary immunoglobulin A (s-IgA) would vary with training intensity sessions (low-intensity [LI] vs. high-intensity sessions [HI]) during a traditional training program divided into 4 training periods and (b) to identify key variables (e.g., GPS data, rating of perceived exertion [RPE], and training duration), which could affect s-IgA. Saliva samples of 10 elite professional soccer players were collected (a) before the investigation started to establish the baseline level and (b) before and after each 4 training sessions (LI vs. HI). Training intensity was monitored as internal (through heart rate responses and RPE) and external (through GPS) loads. High-intensity sessions were associated with higher external load (GPS) and with higher RPE. Baseline and pretraining s-IgA did not differ between the 4 training sessions both for HI and LI. Post-training s-IgA were not different (in absolute value and in percentage of change) between HI and LI sessions at the first 3 periods. However, at the fourth period, s-IgA concentration for HI session was significantly lower (p ≤ 0.05) than the LI session. The percentage change between s-IgA post-training and s-IgA baseline concentrations differ significantly (p ≤ 0.05) between HI and LI training sessions. Significant correlations between s-IgA and training intensity were also noted. High-intensity soccer training sessions might cause a significant decrease in s-IgA values during the postexercise window as compared with LI sessions. This study encourages coaches to monitor s-IgA in routine, particularly during HI training periods, to take precautions to avoid upper respiratory tract infection in highly trained soccer players.

The relationship between lower-limb strength and match-related muscle damage in elite level professional European soccer players.

In professional soccer, the benefits of lower limb strength training have been advocated. However, from an aspect of performance development, specifically with respect to expression of fatigue and injury prevention, the advantages of increased lower body strength have received limited attention at the elite level of the game. The primary aim of this cross-sectional investigation was to examine the association between lower body strength and the expression of markers of fatigue as evaluated through muscle damage assessment following match play in professional soccer players. Ten male professional soccer players participated in this investigation (mean ± SD age 26.2 ± 4.3 years, height 181.6 ± 4.8 cm and body mass 78.7 ± 6.1 kg); creatine kinase (CK) was collected 2-days post-match for a 5-month period and at three different time points (Phase 1, Phase 2 and Phase 3); muscular strength (e.g. 4 repetition half-squat) was measured 3-day post-match. No significant change in CK and muscular force across three time points was found (F = 0.60, P = 0.56, η(2) = 0.06 and F = 2.65, P = 0.10, η(2) = 0.23, respectively). Muscular force was negatively correlated (moderate to very large) with CK. It can be concluded that players who produce greater lower body force as a result of being stronger in the lower limbs show reduced levels of CK 48 h post-match.