Michel Brink

Monitoring stress and recovery: new insights for the prevention of injuries and illnesses in elite youth soccer players

Objective Elite youth soccer players have a relatively high risk for injuries and illnesses due to increased physical and psychosocial stress. The aim of this study is to investigate how measures to monitor stress and recovery, and its analysis, provide useful information for the prevention of injuries and illnesses in elite youth soccer players. Methods 53 elite soccer players between 15 and 18 years of age participated in this study. To determine physical stress, soccer players registered training and match duration and session rating of perceived exertion for two competitive seasons by means of daily training logs. The Dutch version of the Recovery Stress Questionnaire for athletes (RESTQ-Sport) was administered monthly to assess the psychosocial stress–recovery state of players. The medical staff collected injury and illness data using the standardised Fédération Internationale de Football Association registration system. ORs and 95% CIs were calculated for injuries and illnesses using multinomial regression analyses. The independent measures were stress and recovery. Results During the study period, 320 injuries and 82 illnesses occurred. Multinomial regression demonstrated that physical stress was related to both injury and illness (range OR 1.01 to 2.59). Psychosocial stress and recovery were related the occurrence of illness (range OR 0.56 to 2.27). Conclusions Injuries are related to physical stress. Physical stress and psychosocial stress and recovery are important in relation to illness. Individual monitoring of stress and recovery may provide useful information to prevent soccer players from injuries and illnesses.

Changes in perceived stress and recovery in overreached young elite soccer players

The aim of this study was to prospectively monitor sport‐specific performance and assess the stress–recovery balance in overreached (OR) soccer players and controls. During two competitive seasons, 94 players participated in the study. The stress–recovery balance (RESTQ‐Sport) and sport‐specific performance (Interval Shuttle Run Test) were assessed monthly. Seven players with performance decrement of at least a month were classified as OR. Stress and recovery measures were assessed between groups (OR vs healthy players) and at different times within the OR group. An unfavorable total recovery score appeared 2 months before diagnosis when compared with the reference values of the healthy group established at the start of the season (P=0.009) and also over the two seasons (P=0.028). The scales Emotional Stress (P=0.044), Physical Recovery (P=0.009), General Well‐being (P=0.001) and Sleep Quality (P=0.045) were sensitive to OR compared with the average of the healthy group over the two seasons. Finally, Fatigue and Being in Shape demonstrated the largest changes in stress and recovery within the OR players (effect size=1.14 and 1.50). The longitudinal monitoring of performance and changes in stress and recovery may be useful for the detection of OR in its earliest stage. The information obtained from these tests can be used to optimize individual training and recovery programs.

Monitoring load, recovery and performance in young elite soccer players

Brink, MS, Nederhof, E, Visscher, C, Schmikli, SL, and Lemmink, KAPM. Monitoring load, recovery, and performance in young elite soccer players. J Strength Cond Res 24(3): 597-603, 2010-The purpose of this study was to investigate the relation between training load, recovery, and monthly field test performance in young elite soccer players to develop training guidelines to enhance performance. In a prospective, nonexperimental cohort design, 18 young elite soccer players registered training and match duration for a full competitive season by means of daily training logs. Furthermore, session rating of perceived exertion (RPE) and total quality of recovery (TQR) scores were recorded. Weekly duration (TLd), load (duration × session RPE = TLrpe), and TQR scores were calculated for 1 and 2 weeks before a monthly submaximal interval shuttle run tests to determine interval endurance capacity. Participants spent on average 394.4 ± 134.9 minutes per week on training and game play with an average session RPE of 14.4 ± 1.2 (somewhat hard) and TQR of 14.7 ± 1.3 (good recovery). Random intercept models showed that every extra hour training or game play resulted in enhanced field test performance (p < 0.05). Session RPE and TQR scores did not contribute to the prediction of performance. The duration of training and game play in the week before field test performance is most strongly related to interval endurance capacity. Therefore, coaches should focus on training duration to improve interval endurance capacity in elite soccer players. To evaluate the group and individual training response, field tests should be frequently executed and be incorporated in the training program.

Sport Injuries Aligned to Peak Height Velocity in Talented Pubertal Soccer Players

In young athletes, demands of sports are superimposed on normal growth and maturation. It has been suggested that this causes a temporarily increased vulnerability for injuries. We followed 26 talented soccer players (mean age 11.9±0.84 years) longitudinally for 3 years around their adolescent growth spurt, called Peak Height Velocity, to identify differences in number of traumatic and overuse injuries and days missed due to injuries. Peak Height Velocity was calculated according to the Maturity Offset Protocol. The number of injuries was calculated for each player per year. A repeated measurement analysis showed that athletes had significantly more traumatic injuries in the year of Peak Height Velocity (1.41) than in the year before Peak Height Velocity (0.81). A moderate effect size of 0.42 was found for the difference in number of overuse injuries per player per year before (0.81) and after Peak Height Velocity (1.41), respectively. Finally, a moderate effect size of 0.55 was found for difference between days missed due to injuries before (7.27 days per player per year) and during Peak Height Velocity (15.69 days per player per year). Adolescent growth spurt seems to result in increased vulnerability for traumatic injuries. Afterwards athletes seem to be susceptible to overuse injuries.

Evidence of Nervous System Sensitization in Commonly Presenting and Persistent Painful Tendinopathies: A Systematic Review.

Study Design Systematic review. Objectives To elucidate if there is sensitization of the nervous system in those with persistent rotator cuff (shoulder), lateral elbow, patellar, and Achilles tendinopathies. Background Tendinopathy can be difficult to treat, and persistent intractable pain and dysfunction are frequent. It is hypothesized that induction or maintenance of persistent pain in tendinopathy may be, at least in part, based on changes in the nervous system. Methods The PRISMA guidelines were followed. Relevant articles were identified through a computerized search in Embase, PubMed, and Web of Science, followed by a manual search of reference lists of retained articles. To be eligible, studies had to include quantitative sensory testing and evaluate individuals diagnosed with a persistent tendinopathy of the rotator cuff (shoulder), lateral elbow, patella, or Achilles tendon. Methodological quality assessment was evaluated with the Newcastle-Ottawa Scale. Results In total, 16 full-text articles met the criteria for inclusion, of which the majority were case-control studies with heterogeneous methodological quality. No studies on Achilles tendinopathy were found. Mechanical algometry was the predominant quantitative sensory testing used. Lowered pressure pain threshold was observed across different tendinopathies at the site of tendinopathy, as well as at other sites, the latter being suggestive of central sensitization. Conclusion Although more research on sensory abnormalities is warranted, it appears likely that there is an association between persistent tendon pain and sensitization of the nervous system. This evidence is primarily from studies of upper-limb tendinopathy, and caution should be exercised with inference to lower-limb tendinopathy. J Orthop Sports Phys Ther 2015;45(11):864-875. Epub 21 Sep 2015. doi:10.2519/jospt.2015.5895.

Can we detect non-functional overreaching in young elite soccer players and middle-long distance runners using field performance tests?

Objective To study whether field performance tests can make a valid distinction between non-functionally overreaching (NFO) athletes and control athletes. Design Monthly field performance tests were used to determine a performance decrement (PD) throughout a season. Athletes with a minimum of 1 month PD were compared with control athletes without a PD on mood characteristics and resting levels of stress hormones. Setting Sporting field and sports medical laboratory. Participants 129 young elite athletes, 77 soccer players and 52 middle-long distance runners were followed prospectively during the 2006–2007 season. Fifteen of them were invited to the laboratory. Eight athletes showed a performance decrease lasting longer than 1 month, and seven athletes without a performance decrease acted as their controls. Main outcome measures Performance changes over time were measured using field tests. Profile of Mood States and resting levels of adrenocorticotrophic hormone (ACTH) and cortisol in blood were measured in the laboratory. Results PD athletes showed several symptoms typical of the non-functional state of overreaching (OR). The PD group scored higher on depression and anger than controls. They also showed a specific pattern of correlations between negative mood subscales (tension, fatigue and depression), which was absent in controls. ACTH levels at rest were similar, but lower cortisol levels in PD athletes pointed at a blunted cortisol response. Cortisol levels were decoupled from ACTH levels only in PD athletes. Conclusions Implementing performance-related criteria in field tests can help coaches and sports physicians to distinguish NFO athletes from athletes with balanced workload and recovery.

Importance of peak height velocity timing in terms of injuries in talented soccer players

The purpose of this study was to identify differences in traumatic and overuse injury incidence between talented soccer players who differ in the timing of their adolescent growth spurt. 26 soccer players (mean age 11.9 ± 0.84 years) were followed longitudinally for 3 years around Peak Height Velocity, calculated according to the Maturity Offset Protocol. The group was divided into an earlier and later maturing group by median split. Injuries were registered following the FIFA consensus statement. Mann-Whitney tests showed that later maturing players had a significantly higher overuse injury incidence than their earlier maturing counterparts both in the year before Peak Height Velocity (3.53 vs.0.49 overuse injuries/1 000 h of exposure,U = 49.50, z = − 2.049, p < 0.05) and the year of Peak Height Velocity (3.97 vs. 1.56 overuse injuries/1 000 h of exposure, U = 50.5, z = − 1.796,p < 0.05). Trainers and coaches should be careful with the training and match load they put on talented soccer players, especially those physically not (yet) able to handle that load. Players appear to be especially susceptible to injury between 13.5 and 14.5 years of age. Training and match load should be structured relative to maturity such that athletic development is maximized and the risk of injury is minimized.

Monitoring performance, pituitary–adrenal hormones and mood profiles: how to diagnose non-functional over-reaching in male elite junior soccer players

Objective To verify if in male elite junior soccer players a minimum 1-month performance decrease is accompanied by a mood profile and hormone levels typical of non-functional over-reaching (NFOR). Design A prospective case-control study using a monthly performance monitor with a standardised field test to detect the performance changes. Players with a performance decrease lasting at least 1 month were compared with control players without a performance decrease on mood scores and pre-exercise and postexercise levels of stress hormones. Setting Sporting field and sports medical laboratory. Participants Ninety-four young elite soccer players were monitored during the 2006–2008 seasons. Twenty-one players were invited to the laboratory, seven of whom showed a significant performance decrease. Main outcome measures Performance change over time, scores on the profile of mood states and premaximal and postmaximal exercise serum levels of adrenocorticotropic hormone (ACTH), growth hormone (GH) and cortisol. Results Players with a performance decrease showed psychological and hormonal changes typical of the non-functional state of over-reaching. Scores were higher on depression and anger, whereas the resting GH levels and ACTH levels after maximal exercise were reduced. ACTH and GH were capable of classifying all but one player correctly as either NFOR or control. Conclusions Performance-related criteria in field tests are capable of identifying players with worsened mood and adaptations of the endocrine system that fit the definition of NFOR. Performance, mood and hormone levels may therefore be considered as valid instruments to diagnose NFOR in young elite soccer players.

Sports injuries in physical education teacher education students

Sports injuries could be highly detrimental to the career of a physical education teacher education (PETE) student. To enable the development of future sports injury prevention programs, sports injuries in 128 first‐year academic bachelor PETE students were registered prospectively during one academic year. Common risk factors for sports injuries, taken from the literature, were also evaluated by means of logistic regression analysis. We found an incidence rate of 1.91 and an injury risk of 0.85, which is higher than generally found in a sports‐active population. Most injuries involved the lower extremities, were acute, newly occurring injuries, and took place in non‐contact situations. More than half of all injuries lead to an inactivity period of 1 week or more and over 80% of all injuries required medical attention. A major part of these injuries happened during the intracurricular sports classes. Few differences were seen between women and men. A history of injury was a significant risk factor (P = 0.018) for the occurrence of injuries, and performance of cooling‐down exercises was significantly related to a lower occurrence of ankle injuries (P = 0.031). These data can inform future programs for the prevention of sports injuries in PETE students.

Anthropometric Injury Risk Factors in Elite-standard Youth Soccer

The aim of the study was to investigate whether an increased risk of injury occurrence can be determined through frequent anthropometric measurements in elite-standard youth soccer players. Over the course of one season, we followed 101 male elite-standard youth soccer players between 11 and 19 years of age. Height and body mass were monitored at monthly measurement intervals and fat percentage was assessed every 3 months by use of the sum of skinfold method. Growth in height (cm), alternations in body mass index (kg/m(2)), fat percentage and fat-free mass index (kg/m(2)) were calculated. Injuries were recorded in accordance with the recommendations of the FIFA Consensus Model for Injury Registration. Odds ratio scores and 95% confidence intervals were calculated using binary logistic regression analyses. The following anthropometric injury risk factors were identified: ≥ 0.6 centimeter growth per month (p=0.03; OR=1.63; 95% CI: 1.06-2.52), ≥ 0.3 kg/m(2) increase of body mass index value per month (p=0.03; OR=1.61; 95% CI: 1.04-2.49) and low fat percentage; i. e., < 7% for players aged 11-16 and < 5% for players over 16 years (p=0.01; OR=1.81; 95% CI: 1.18-2.76). Individual monitoring of anthropometrics provides useful information to determine increased risk of injury occurrence in elite-standard youth soccer.