Do non-contact injuries occur during high-speed running in elite football? Preliminary results from a novel GPS and video-based method.

OBJECTIVES: Understanding how injuries occur (inciting circumstances) is useful for developing etiological hypotheses and prevention strategies. The aims of this study were 1) to evaluate the feasibility of a method combining video and Global Positioning System data to estimate the speed and acceleration of activities leading to injuries and 2) to use this method to analyse the inciting circumstances leading to non-contact injuries. DESIGN: Retrospective descriptive study. METHODS: Injury inciting circumstances from 46 elite players over three seasons were analysed from video recordings and from external load measures collected through Catapult Vector S7 Global Positioning System. RESULTS: In total 34 non-contact injuries were analysed. Sixteen out of the seventeen hamstring injuries occurred when players were running for (median and interquartile range) 16.75 m (8.42-26.65 m) and achieved a peak speed of 29.28 km·h-1 (26.61-31.13 km·h-1) which corresponded to 87.55 % of players' maximal speed (78.5 %-89.75 %). Of the three adductor injuries, one occurred whilst the player was decelerating without the ball, one occurred whilst the player was accelerating and controlling the ball at knee level, and one occurred whilst the player was performing an instep kick. Two quadriceps injuries occurred whilst the players were kicking either whilst walking or running. CONCLUSIONS: From the preliminary results reported in this study most hamstring injuries occurred when players ran >25 km·h-1 and above 80 % of their maximal speed. This study suggests that this novel approach can allow a detailed and standardised analysis of injury inciting circumstances.

Cardiovascular effects of COVID-19 lockdown in professional football players.

BACKGROUND: The COVID-19 pandemic with the stay-at-home orders and lockdown has dramatically forced athletes to stop team training and competitions, causing deep changes in habits and lifestyle. Aim of this study was to evaluate in a retrospective single center study the cardiovascular (CV) health and fitness of elite football player after COVID-19 lockdown in Italy and to compare such findings with the 2019 off-season period, in order to identify potential differences in the CV features and outcomes. METHODS: All 29 professional football players of the first male team were enrolled before resuming training and competition after COVID-19 lockdown and underwent several exams including physical examination, resting and stress electrocardiography (ECG), echocardiography, spirometry and blood tests. RESULTS: Median age was 27 years (23; 31), with no athlete being COVID-19 positive at the time of the evaluation. In comparison with the usual off-season 2-month detraining, significant differences were found for left ventricular (LV) mass (189 g [172; 212] vs. 181 g [167; 206], P=0.024) and LV Mass Index for body surface area (94 g/m2 [85; 104] vs. 88 g/m2 [79.5; 101.5], P=0.017), while LV mass/fat free mass remained unchanged (2.8 g/kg [2.6; 2.9] vs. 2.9 g/kg [2.6; 3.2], P=0.222). Respiratory function and metabolic profile were improved, while no significant changes were found in ECG findings, at rest and during exercise. CONCLUSIONS: Prolonged abstinence from training and competitions induced by lockdown elicited significant changes in comparison with off-season in parameters ascribable to detraining, as the changes in LV mass, in respiratory function and in metabolic profile.

Morning Priming Exercise Strategy to Enhance Afternoon Performance in Young Elite Soccer Players.

PURPOSE: To compare the effects of different modalities of morning priming exercise on afternoon physical performance with the associated hormonal and psychophysiological responses in young soccer players. METHODS: In a randomized counterbalanced crossover design, 12 young soccer players completed 3 different morning conditions on 3 different days: repeated-sprint running (6 × 40 m), easy exercise (4 × 12 fast half squats, 6 speed ladder drills, and 20-m sprints), and control (no exercise). Blood testosterone and cortisol concentrations were assessed upon arrival (approximately 8:30AM) and approximately 5 hours and 30 minutes later. Body temperature, self-reported mood, quadriceps neuromuscular function (maximal voluntary contraction, voluntary activation, rate of torque development, and twitch contractile properties), jump, and sprint performance were evaluated twice per day, while rating of perceived exertion, motivation, and the Yo-Yo Intermittent Recovery level 2 (IR2) tests were assessed once per day. RESULTS: Compared with the control, repeated-sprint running induced a possible positive effect on testosterone (+11.6%) but a possible to very likely negative effect on twitch contractile properties (-13.0%), jump height (-1.4%), and Yo-Yo IR2 (-7.1%). On the other hand, easy exercise had an unclear effect on testosterone (-3.3%), resulted in lower self-reported fatigue (-31.0%) and cortisol (-12.9%), and had a possible positive effect on the rate of torque development (+4.3%) and Yo-Yo IR2 (+6.5%) compared with the control. CONCLUSIONS: Players' testosterone levels were positively influenced by repeated-sprint running, but this did not translate into better physical function, as both muscular and endurance performance were reduced. Easy exercise seemed to be suitable to optimize the physical performance and psychophysiological state of young soccer players.

Mental health and well-being during COVID-19 lockdown: A survey case report of high-level male and female players of an Italian Serie A football club.

OBJECTIVES: To describe high-level footballers' levels and changes in mental health and well-being throughout a 8-week period of lockdown and restricted training during the COVID-19 pandemic. METHOD: One-hundred and one players belonging to four teams (women's and men's, first and U19 teams) of the same Italian Serie A club participated in the study. Data were collected through an online questionnaire, and administered at 2, 3, 5, 7 and 9 weeks after the start of the lockdown . Well-being, positive and negative affects measurements were examined. RESULTS: Across the five measures, 36% of players reported clinical levels in depressive symptoms (scores ≤50) on at least one occasion. Thirteen percent of the players reported clinical levels on > 50% of the occasions. There was a decrease in depressive symptoms and negative affects over the period. No change was found in positive affects. CONCLUSIONS: High number of players reportedclinical levels of depressive symptoms compared to what was found previously in high-level athletes. The number decrease during the 8-week period. A similar trend was found for negative affects.Despite a higher prevalence in depressive symptoms earlier during lockdown, this improved as players progressed towards fewer restrictions.

On-Sight and Red-Point Climbing: Changes in Performance and Route-Finding Ability in Male Advanced Climbers.

AIM: In lead climbing, the ascent of the route can be defined as on-sight or red-point. On-sight is the more challenging style since it demands greater physiological and psychological commitment. The differences between the two modes in advanced climbers have not been studied much. Two essential skills needed to optimize performance, in both on-sight and in red-point climbing, are route interpretation (RI) ability and movements sequence recall. Therefore, this study aimed to compare performance between on-sight and red-point ascent in advanced climbers and evaluate how a climber's RI ability and movement sequences recall might change before and after on-sight and red-point climbing. METHODS: Eighteen advanced male climbers (age 29.2 ± 4.7 years, body mass 67.8 ± 3.6 kg, stature 175.2 ± 2.4 cm, best red-point and on-sight grades 7b+/8a and 7a+/7b+, respectively) were video-recorded during the route ascent in on-sight and red-point modes to evaluate performance and to measure static and dynamic action times. RI ability and movement sequence recall were assessed before and after each climb. Level of anxiety was evaluated via a self-report questionnaire. Heart rate (f H), lactate concentration, ([La-]), and rating of perceived exertion (RPE) were detected during and after each climb. RESULTS: Compared to on-sight, an improvement in performance was observed in a red-point climb: the ascent was faster (148.7 ± 13.6 s and 179.5 ± 12.5 s, respectively, P < 0.05), smoother (significant reduction in exploratory moves and in stops times, P < 0.05), less demanding physiologically (lower f H peak and [La-]peak, P < 0.05), and psychologically (lower RPE, cognitive and somatic anxiety and higher self-confidence, P < 0.05). The RI ability was improved in red-point versus on-sight and, in the same mode, between pre and post ascent. CONCLUSION: Red-point climbing was found to be less demanding than on-sight, both physiologically and psychologically, under the conditions investigated by this study. Our findings suggest that RI is a trainable skill and underscore the importance of including specific techniques in training programs designed to improve interaction between perceptual, psychological, and physiological factors.

Exercise-Based Strategies to Prevent Muscle Injury in Elite Footballers: A Systematic Review and Best Evidence Synthesis.

BACKGROUND: Exercise-based strategies are used to prevent muscle injuries in football and studies on different competitive-level populations may provide different results. OBJECTIVES: To evaluate the effectiveness of exercise-based muscle injury prevention strategies in adult elite football. METHODS: A systematic search was conducted in PubMed (MEDLINE), Web of Science, Cochrane Library, and SPORTDiscuss (EBSCO). We considered only elite adult (> 16 year-old) football players with no distinction for gender; the intervention to be any exercise/s performed with the target to prevent lower-limb muscle injuries; the comparison to be no injury prevention exercise undertaken; the outcome to be the number of injuries, injury incidence, and severity. We searched systematic reviews, randomized-controlled trials (RCTs), and non-randomized-controlled trials (NRCTs), limited for English language. Risk of bias was assessed using the Risk of Bias in Systematic Reviews tool, the Cochrane Collaboration's Tool for assessing risk of bias in RCTs, and the Risk of Bias in NRCTs of Interventions tool. RESULTS: 15 studies were included. Three systematic reviews showed inconsistent results, with one supporting (high risk of bias) and two showing insufficient evidence (low risk of bias) to support exercise-based strategies to prevent muscle injuries in elite players. Five RCTs and seven NRCTs support eccentric exercise, proprioception exercises, and a multi-dimensional component to an injury prevention program; however, all were deemed to be at high/critical risk of bias. Only one RCT was found at low risk of bias and supported eccentric exercise for preventing groin problems. CONCLUSION: We found limited scientific evidence to support exercise-based strategies to prevent muscle injury in elite footballers. TRIAL REGISTRATION NUMBER: PROSPERO CRD42017077705.

Validity of Session Rating of Perceived Exertion Assessed via the CR100 Scale to Track Internal Load in Elite Youth Football Players.

PURPOSE: To assess the convergent validity of the Borg CR100® scale to track internal training load (TL) in youth football players. METHODS: A total of 19 youth football players (age = 15 [1] y, height = 175.9 [12.3] cm, and body mass = 69 [15.4] kg) were monitored for 27 sessions, including training and games. Internal TL was assessed via session rating of perceived exertion (sRPE) and 2 heart-rate-based methods (Banister training impulse and Edwards TL). The correlations between sRPE and heart-rate-based TL, the differences in individual player intercepts and slopes, and the differences between types of sessions (training vs games) were assessed using a general linear mixed model with magnitude-based inferences. RESULTS: Correlations between sRPE and Banister training impulse were very large at overall group level (r = .77; 90% confidence limits, .72-.80) and individual level (range .70-.95). Correlations between sRPE and Edwards TL were very large at overall group level (r = .84; 90% confidence limit, .82-.86) and large to very large at individual level (range .64-.93). A very likely small difference was found in the comparison between games and training sessions for the relationship between sRPE and Banister training impulse. CONCLUSIONS: The Borg CR100 scale is a valid method for monitoring TL in youth football players.

Determining the Relationship Between Internal Load Markers and Noncontact Injuries in Young Elite Soccer Players.

PURPOSE: To examine the association and predictive ability of internal load markers with regard to noncontact injuries in young elite soccer players. METHODS: Twenty-two soccer players (18.6 [0.6] y) who competed in the Spanish U19 League participated in the study. During a full season, noncontact injuries were recorded and, using session rating of perceived exertion, internal weekly load (sum of load of all training sessions and matches for each week) and acute:chronic workload ratio (typically, acute = current week and chronic = rolling 4-wk average) were calculated. A generalized estimating equation analysis was used to examine the association of weekly and acute:chronic load-ratio markers with a noncontact injury in the subsequent week. Load variables were also analyzed for predictive ability with receiver operating characteristic curve and area under the curve. RESULTS: No association was found for weekly load (odds ratio = 1.00; 90% confidence interval, 0.99-1.00) and acute:chronic load ratio (odds ratio = 0.16; 90% confidence interval, 0.01-1.84) with respect to injury occurrence. In addition, the analyzed load markers showed poor ability to predict injury occurrence (area under the curve < .50). CONCLUSIONS: The results of this study suggest that internal load markers are not associated with noncontact injuries in young soccer players and present poor predictive capacity with regard to the latter.

Return to competition after an Achilles tendon rupture using both on and off the field load monitoring as guidance: A case report of a top-level soccer player.

OBJECTIVES: To describe the Return to competition after Achilles Tendon rupture (ATR) in an elite soccer player. DESIGN: Case report. SETTING: Return to sport (RTS) of a professional soccer player who suffered an ATR during a match. The RTS phase started 15 weeks after surgery and specific on-field activities were gradually introduced. Criteria used to monitor the transition through the different phases were strength and endurance of the calf muscle and ability to sustain specific on-field training loads (TL) monitored with Global Positioning System and heart-rate system. TLs were weekly compared to pre-injury values to evaluate recovery and to prescribe future sessions. PARTICIPANT: A 39-year-old (height 178 cm, weight 75 kg) elite soccer defender player, playing in Italian Serie-A league. RESULTS: Days of absence were lower compared to a cohort presented in UEFA study (119 versus 161 ± 65 days, respectively). External-TL and Internal-TL were organized to gradually increase during RTS and resulted in higher values prior to return to competition compared to pre-injury values. Concentric plantar flexion peak torque increased till 9th months after surgery. CONCLUSIONS: Monitoring of the field activities allowed comparison with pre-injury values and provided a useful and functional criteria to pass return to team activity and competition.

Validity of the Online Athlete Management System to Assess Training Load.

PURPOSE: To validate the quantification of training load (session rating of perceived exertion [s-RPE]) in an Australian Olympic squad (women's water polo), assessed with the use of a modified RPE scale collected via a newly developed online system (athlete management system). METHODS: Sixteen elite women water polo players (age = 26 [3] y, height = 1.78 [0.05] m, and body mass = 75.5 [7.1] kg) participated in the study. Thirty training sessions were monitored for a total of 303 individual sessions. Heart rate was recorded during training sessions using continuous heart-rate telemetry. Participants were asked to rate the intensity of the training sessions on the athlete management system RPE scale, using an online application within 30 min of completion of the sessions. Individual relationships between s-RPE and both Banister training impulse (TRIMP) and Edwards' method were analyzed. RESULTS: Individual correlations with s-RPE ranged between r = .51 and .79 (Banister TRIMP) and r = .54 and .83 (Edwards' method). The percentages of moderate and large correlation were 81% and 19% between s-RPE method and Banister TRIMP, and 56% and 44% between s-RPE and Edwards' method. CONCLUSIONS: The online athlete management system for assessing s-RPE was shown to be a valid indicator of internal training load and can be used in elite sport.

Prediction: The Modern-Day Sport-Science and Sports-Medicine "Quest for the Holy Grail".

In high-performance sport, science and medicine practitioners employ a variety of physical and psychological tests, training and match monitoring, and injury-screening tools for a variety of reasons, mainly to predict performance, identify talented individuals, and flag when an injury will occur. The ability to "predict" outcomes such as performance, talent, or injury is arguably sport science and medicine's modern-day equivalent of the "Quest for the Holy Grail." The purpose of this invited commentary is to highlight the common misinterpretation of studies investigating association to those actually analyzing prediction and to provide practitioners with simple recommendations to quickly distinguish between methods pertaining to association and those of prediction.

Use of CR100 Scale for Session Rating of Perceived Exertion in Soccer and Its Interchangeability With the CR10.

PURPOSE: To examine the construct validity of the session rating perceived exertion (s-RPE) assessed with the Borg CR100 scale to measure training loads in elite soccer and to examine if the CR100 is interchangeable and can provide more-accurate ratings than the CR10 scale. METHODS: Two studies were conducted. The validity of the CR100 was determined in 19 elite soccer players (age 28 ± 6 y, height 180 ± 7 cm, body mass 77 ± 6 kg) during training sessions through correlations with the Edwards heart-rate method (study 1). The interchangeability with CR10 was assessed in 78 soccer players (age 19.3 ± 4.1 y, height 178 ± 5.9 cm, body mass 71.4 ± 6.1 kg) through the Bland-Altman method and correlations between change scores in different sessions. To examine whether the CR100 is more finely graded than the CR10, the proportions of responses corresponding to the verbal expressions were calculated (study 2). RESULTS: Individual correlations between the Edwards method and s-RPE were large to very large (.52-.85). The mean difference between the 2 scales was -0.3 ± 0.33 AU (90% CI -0.41 to -0.29) with 95% limits of agreements (0.31 to -0.96 AU). Correlations between scales and between-changes scores were nearly perfect (.95 and .91-.98). Ratings corresponding to the verbal anchors were 49% in CR10 and 26% in CR100. CONCLUSIONS: The CR100 is valid for assessing the training load in elite soccer players. It can be used interchangeably with the CR10 and may provide more-precise measures of exercise intensity.

Effect of training-session intensity distribution on session rating of perceived exertion in soccer players.

PURPOSE: To examine the effect of different exercise-intensity distributions within a training session on the session rating of perceived exertion (RPE) and to examine the timing of measure on the rating. METHODS: Nineteen junior players (age 16±1 y, height 173±5 cm, body mass 64±6 kg) from a Swiss soccer team were involved in the study. Percentage of heart rate maximum (%HR) and RPE (Borg CR100®) were collected in 4 standardized training sessions (conditions). The Total Quality of Recovery scale (TQR) and a visual analogue scale (VAS) for pain of the lower limbs were used to control for the effect of pretraining fatigue. Every session consisted of three 20-min blocks of different intensities (ie, low-moderate-high) performed in a random order. RPE was collected after every block (RPE5), immediately after the session (RPE-end), and 30 min after the session (RPE30). RESULTS: RPE5s of each block were different depending on the distribution sequence (P<.0001). RPE-end, TQR, and VAS values were not different between conditions (P=.57, P=.55, and P=.96, respectively). The %HR was significantly different between conditions (P=.008), with condition 3 higher than condition 2 (74.1 vs 70.2%, P=.02). Edwards training loads were not significantly different between conditions (P=.09). RPE30 was not different from RPE-end (P>.05). CONCLUSIONS: The current results show that coaches can design training sessions without concern about the influence of the within-session distribution of exercise intensity on session-RPE and that RPE can be collected at the end of the session or 30 min later.

Are the Yo-Yo intermittent recovery test levels 1 and 2 both useful? Reliability, responsiveness and interchangeability in young soccer players.

Abstract The aim of this study was to compare the reliability, internal responsiveness and interchangeability of the Yo-Yo intermittent recovery test level 1 (YY1), level 2 (YY2) and submaximal YY1 (YY1-sub). Twenty-four young soccer players (age 17 ± 1 years; height 177 ± 7 cm; body mass 68 ± 6 kg) completed each test five times within pre- and in-season; distances covered and heart rates (HRs) were measured. Reliability was expressed as typical error of measurement (TEM) and intraclass correlation coefficient (ICC). Internal responsiveness was determined as effect size (ES) and signal-to-noise ratio (ESTEM). Interchangeability was determined with correlation between training-induced changes. The TEM and ICC for distances in the YY1 and YY2 and for HR in YY1-sub were 7.3% and 0.78, 7.1% and 0.93 and 2.2% and 0.78, respectively. The ESs and ESTEMs were 0.9 and 1.9 for YY1, 0.4 and 1.2 for YY2 and -0.3 and -0.3 for YY1-sub. Correlations between YY1 vs. YY2 and YY1-sub were 0.56 to 0.84 and -0.36 to -0.81, respectively. Correlations between change scores in YY1 vs. YY2 were 0.29 and -0.21 vs. YY1-sub. Peak HR was higher in YY1 vs. YY2. The YY1 and YY2 showed similar reliability; however, they were not interchangeable. The YY1 was more responsive to training compared to YY2 and YY1-sub.

Differences in climbing-specific strength between boulder and lead rock climbers.

The purpose of this study was to compare maximal muscle strength and rapid force capacity of finger flexors between boulder and lead climbers of national-international level. Ten boulder (mean ± SD, age 27 ± 8 years) and 10 lead climbers (age 27 ± 6 years) volunteered for the study. Ten nonclimbers (age 25 ± 4 years) were also tested. Isometric maximal voluntary contraction (MVC) force and rate of force development (RFD) produced in "crimp" and "open-crimp" hand positions were evaluated on an instrumented hold. Climbers were stronger than nonclimbers. More interestingly, MVC force and RFD were significantly greater in boulder compared with lead climbers (p < 0.05), in both crimp and open-crimp positions. The RFD was the most discriminatory outcome, as the largest difference between boulder and lead climbers (34-38%) was observed for this variable. The RFD may reflect the specific requirements of bouldering and seems to be more appropriate than pure maximal strength for investigating muscle function in rock climbers.

Effect of bout duration on exercise intensity and technical performance of small-sided games in soccer.

To examine whether the increase in bout duration would affect the exercise intensity and technical actions, we manipulated bout duration during a typical small-sided game drill (SSG) in male soccer players. Nineteen players (mean ± SD: age 24 ± 4 years, body mass 74 ± 4 kg, and height 180 ± 5 cm) completed three bouts of a 3-a-side drill at three different bout durations: 2, 4, and 6 minutes. Exercise intensity was quantified using heart rate (HR) and rating of perceived exertion (RPE). A nonsignificant duration × bout interaction was found for HR (p = 0.757). Heart rates of bout 1 were significantly lower than bout 2 (p = 0.004) and bout 3 (p = 0.049). The effect of duration was close to significance for HR (p = 0.057) with 6-minute SSG significantly lower than 4-minute SSG (p = 0.004). Duration × bout interaction did not reach the significance for RPE (p = 0.096). The RPE significantly increased along the bouts (p < 0.001) but was not affected by duration (p = 0.763). No effect of duration was found for number of technical actions per minute (p > 0.111). A significant effect of bout was only found for successful passes (p = 0.018). Partially confirming our hypothesis, the increase in bout duration from 2 to 6 minutes resulted in a decrease in intensity only between the 4- and 6-min SSG. However, duration did not influence the technical actions and proficiency. The magnitude of changes in HR (89.5 vs. 87.8 of maximum) is probably not enough to induce different training adaptations. Therefore, coaches can use different bout durations with minimal impact on exercise intensity and without compromising technical proficiency.

Repeated-sprint ability in professional and amateur soccer players.

This study investigated the repeated-sprint ability (RSA) physiological responses to a standardized, high-intensity, intermittent running test (HIT), maximal oxygen uptake (VO(2) (max)) and oxygen uptake (VO(2)) kinetics in male soccer players (professional (N = 12) and amateur (N = 11)) of different playing standards. The relationships between each of these factors and RSA performance were determined. Mean RSA time (RSA(mean)) and RSA decrement were related to the physiological responses to HIT (blood lactate concentration ([La(-)]), r = 0.66 and 0.77; blood bicarbonate concentration ([HCO(3)-]), r = -0.71 and -0.75; and blood hydrogen ion concentration ([H(+)]), r = 0.61 and 0.73; all p < 0.05), VO(2) (max) (r = -0.45 and -0.65, p < 0.05), and time constant (tau) in VO(2) kinetics (r = 0.62 and 0.62, p < 0.05). VO(2) (max) was not different between playing standards (58.5 +/- 4.0 vs. 56.3 +/- 4.5 mL.kg(-1).min(-1); p = 0.227); however, the professional players demonstrated better RSA(mean) (7.17 +/- 0.09 vs. 7.41 +/- 0.19 s; p = 0.001), lower [La-] (5.7 +/- 1.5 vs. 8.2 +/- 2.2 mmol.L(-1); p = 0.004), lower [H+] (46.5 +/- 5.3 vs. 52.2 +/- 3.4 mmol.L(-1); p = 0.007), and higher [HCO3-] (20.1 +/- 2.1 vs. 17.7 +/- 1.7 mmol.L(-1); p = 0.006) after the HIT, and a shorter in VO2 kinetics (27.2 +/- 3.5 vs. 32.3 +/- 6.0 s; p = 0.019). These results show that RSA performance, the physiological response to the HIT, and differentiate between professional- and amateur-standard soccer players. Our results also show that RSA performance is related to VO(2) max, tau, and selected physiological responses to a standardized, high-intensity, intermittent exercise.