LA FATICA NEUROMUSCOLARE NEL CALCIO: ASPETTI CENTRALI E PERIFERICI

Soccer is a team sport that requires prolonged high-intensity intermittent exercise. Physical aspects of match performance have changed a lot in the last forty years; for example total distance has increased from 7000-8000 m in the seventies to 10000-11000 m reported in recent investigations. Nowadays, during the match, players change activity on average every 5 seconds and perform approximately 1300 actions, with 200 of these being completed at high-intensity. In addition, the game involves other intense actions such as decelerations, kicking, dribbling, and tackling. All of these efforts exacerbate the physical strain imposed on the players and contribute to making football highly physiologically demanding. Furthermore, soccer players that compete at high level perform up to 70 matches during a single season. During the second half of a match, the total distance and high-intensity running decline markedly, with the amount of high-intensity running 20% to 40% lower in the last 15 min of the game compared with the initial 15-min period. A greater decrement in running is observed when more activity is performed in the first half. Furthermore, in the 5-min period following the most demanding 5-min of the game, the distance covered at high intensity is reduced by 6% to 12% compared with the game average. Collectively, these results indicate that players experience fatigue toward the end of a match and temporarily during a game. Accordingly, both single and repeated-sprint test performances are impaired after a high-intensity period during as well as at the end of the game. Fatigue may also have a negative impact on passing precision, with the less fit players showing a more pronounced deterioration in technical performance. Furthermore, maximal strength and jumping ability are also both reduced immediately after a match. The time required for a full recovery of these qualities in male players may be very long (> 72 h) (permanent fatigue). However, there is limited information regarding recovery time in high level athletes. In literature, fatigue can be defined as an acute impairment of performance that includes both an increase in the perceived of the effort necessary to exert a desired force or power and/or reduction in the ability to exert maximal force or power. It has been demonstrated that the neuromuscular mechanisms that contribute to performance impairment differ according to the contraction mode, exercise intensity and the duration. Fatigue can be classified as central when the origin is proximal and/or peripheral when the origin is distal to the neuromuscular junction. However, to date, no studies have quantified the relative contribution of central and peripheral factors in determining fatigue in soccer. Peripheral skeletal muscle function can be determined using electrical stimulations and classified as high-frequency and low-frequency (or long-lasting fatigue). Long-lasting fatigue can be evaluated using tetanic nerve stimulations at different frequencies (low- to high-frequency force ratio). Nonetheless, tetanic nerve stimulations are very painful, and their usability is limited. Paired stimulations have been proposed as a surrogate of the stimulation trains, and recent research demonstrates the validity of this method to quantify muscle fatigue induced by eccentric exercise. In chapter 2, a study was conducted to determine the extent to which neuromuscular fatigue occurs in high-level professional soccer players. In addition to this, we aimed to examine recovery after a match and to examine its relationship with central and peripheral fatigue indicators. Maximal voluntary contraction (MVC), sprint and passing abilities, muscle soreness, maximal voluntary activation, EMG activity, and evoked quadriceps contractile properties (using different electrical stimulations) were determined before, immediately after, and at 24 and 48 h after the match in 20 male professional players. Immediately after a game, fatigue was evident from the reduction in MVC and sprint performance (-11%, P < 0.001 and -3%, P < 0.001, respectively) as well as increased muscle soreness (P < 0.001) compared with baseline. However, short-passing ability was seen to be preserved. This was observed alongside maximal voluntary activation and EMG activity being reduced by 8% (P < 0.001) and 12% (P = 0.001), respectively. M-wave characteristics were unchanged, whereas quadriceps mechanical responses to single and paired stimulations at 10 Hz resulted significantly reduced (peak torque = -8%, P < 0.001 and -9%, P < 0.001). Despite the observation of a partial recovery 24 h after the game, all variables returned to baseline values 48 h after the match. In high-level professional players, the fatigue induced by a soccer match occurs to a lesser extent than in lower level athletes and appears to be recovered in a faster fashion. Match-related fatigue is determined by a combination of central and peripheral factors. A relationship exists between central fatigue indicators, MVC and sprint performance decrements, whereas muscle soreness appears to be linked to peripheral fatigue indicators, in particular to mechanical responses at low-frequency stimulations. In chapter 3, a study was conducted to determine the possible relationship between match related fatigue and goal scoring. Some preliminary observations indicate that goal scoring increases over time during the game; however, these preliminary results were obtained analyzing minor soccer leagues and/or using a limited amount of matches. The aim of this study was to examine the goal scoring patterns in four major European leagues (English Premier League, French Football Ligue 1, Italian Serie A and Spanish Football Liga) across three consecutive seasons (2008\u201309, 2009\u201310 and 2010\u201311). Chi square analysis revealed a significantly (P < 0.001) higher goal scoring frequency in the second half (55.1 %) compared to the first half (44.9 %). With 15-min interval analysis highlighting a significant (P < 0.001) upward trend in the number of goals scored as time progressed (13.7, 15.1, 16.2, 17.7, 17.2 and 20.2 %, for 0\u201315, 15\u201330, 30\u201345, 45\u201360, 60\u201375 and 75\u201390 intervals respectively). The main finding of the present study is that, in the four major European soccer leagues investigated, the amount of goals scored is greater in the second half, with the scoring rate being highest in the last 15-min of a match. Fatigue occurring during the game may play a role; however, fatigue alone cannot explain the differences. The state of the games result and the reduced time available for scoring are other potential contributing factors to the increased goal scoring patterns observed in the latter stages of the game. Repeated-sprint ability (RSA) is defined by the ability to perform several sprints interspersed with brief recovery periods. RSA is an essential component of many team sports like soccer and is deemed to be an important determinant of physical performance. Several studies have been carried out to establish the physiological determinants of RSA and to investigate the fatigue mechanisms related to this particular form of exercise in order to improve performance. However, no study to date has investigated the high- and low-frequency fatigue induced in more than one muscle group involved during fatiguing RSA exercise. In chapter 4, a study was presented aimed to investigate peripheral fatigue in Knee Extensor (KE) and Plantar Flexor (PF) muscles RSA cycling and running tests. Both RSA tests consisted of 5 x 6 s sprints and peripheral fatigue was quantified using diverse electrical stimulations (from a single stimulus to paired stimulations at 100 Hz). The main findings were that RSA cycling induced higher decrements in peak torque (PT), maximal rate of torque development and relaxation of KE compared with running (PT decrements at different stimulation frequencies: -39% to -53% cycling vs -16% to -39% running, P 0.231). However, the higher decrements of some PT ratios of the PF (10/100 Hz, 20/50 Hz and 20/100 Hz) confirmed the presence of low-frequency fatigue following RSA cycling. Subjects also reported significantly higher values for RPE leg following RSA cycling (8.2 vs 7.3 respectively, P = 0.018) despite no differences in blood lactate, hydrogen ions and bicarbonates concentrations (P > 0.467). The higher level of peripheral fatigue induced by RSA cycling may be partially related to longer fractional duration of muscle contraction phases which can limit local blood flow. The discrepancies in neuromuscular fatigue between KE and PF can be partially explained by differences in muscle fibre composition and/or muscle contributions during RSA tests. A number of studies have determined the reproducibility of peripheral muscle contractile properties at rest reporting good values of coefficient of variation. Only one study has assessed the reliability of the quadriceps contractile properties in a fatigued state. This was achieved using a sustained (2 minutes) maximal isometric contraction. However, this form of exercise is far from specific for the majority of sporting performances. In order to use electrical stimulations as a tool to determine the extent of peripheral muscle fatigue experienced by athletes it is necessary to carry out methodological studies that establish the reliability of peripheral muscle fatigue measures caused by a specific exercise. For these reasons, in chapter 5 a reliability study was conducted to determine the reproducibility of peripheral fatigue induced in knee extensors by high-intensity intermittent running test (HIT). The reliability of the assessment of peripheral fatigue was established in ten amateur soccer players (age: 18 \ub1 1, height: 178 \ub1 5 cm, weight: 68 \ub1 8 kg). Transcutaneous electrical stimulations before and after HIT determined knee extensors muscle contractile properties on three separate occasions (T1, T2 and T3), each separated by 7 days. No significant differences were noted for any of the parameters measured (P = 0.101). The ICC values for peak torque (PT) varied from moderate to high, with the exception of PT at 10 Hz calculated comparing T2 vs T1 (range PRE = 0.78 - 0.92; POST = 0.76 - 0.97). The ICC derived from PT percentage decrements data were all low, with the exception of PT decrements at 1 Hz calculated comparing T3 vs T2 (ICC = 0.85, moderate). The TE for all contractile parameters obtained using 1 Hz and 100 Hz electrical stimulations were below 10%, including some that demonstrated a TE lower than 5%. Muscle contractile properties determined using 10 Hz stimulations showed a higher level of TE (range: 3.2 - 15.1%). Similar results were obtained for maximal rate of torque development and torque relaxation. From the results of this study it can be concluded that muscle contractile properties express a good level of reliability in baseline and post-exercise measures following familiarization. In chapter 6, seasonal variations in peripheral neuromuscular fatigue induced by HIT were established in two groups of professional soccer players: eleven adult players (age: 23 \ub1 3, height: 181 \ub1 4 cm, weight: 78 \ub1 6 kg) and twelve young players (age: 17 \ub1 1, height: 181 \ub1 4 cm, weight: 71 \ub1 5 kg). Transcutaneous electrical stimulations before (PRE) and after (POST) HIT determined knee extensors muscle contractile properties on four separate occasions during a season (before the preparation period Test 1, after the preparation period Test 2, in the mid of competitive period Test 3 and towards the end of the competitive period Test 4). Muscle contractile properties at rest were partially reduced during the competitive period both in adult and young professional players (reduction of PRE maximal rate of torque development at 1 Hz (P < 0.024) and the same parameter at 10 Hz (P < 0.022)). Analysis of POST parameters, confirmed the reduction of the high-frequency fatigue levels during the competitive period for adult players (higher values of POST peak torque at 100 Hz (P = 0.006) and POST maximal rate of torque relaxation at 100 Hz, P = 0.009). Furthermore, in young players, the reduction of both high-frequency fatigue and low-frequency fatigue were evident (POST maximal rate of torque development at 100 Hz (P = 0.035), POST maximal rate of torque relaxation at 100 Hz (P = 0.009), POST peak torque at 10 Hz (P = 0.038) and POST 10/100 Hz ratio (P = 0.012). Considering percentage decrements, several parameters confirm the presence of lower level high-frequency and low-frequency peripheral fatigue both in adult and young players during the competitive period. These results suggest that it is possible to use the assessment of muscle contractile properties to monitor soccer players physical condition. In conclusion, fatigue in soccer is determined by a combination of central and peripheral factors. Central fatigue is evident immediately after and in the hours of recovery following a match (permanent fatigue). While peripheral fatigue is more evident considering some aspects of soccer performance characterized by short high-intensity periods (temporary fatigue). Peripheral fatigue include both high-frequency and low-frequency fatigue with the latter being more evident in young players. Training interventions and strategies applied to improve performance levels should take these aspects into consideration

Evaluation of goal scoring patterns between the 2016 copa America and the 2016 European championship

© 2018, Asian Journal of Sports Medicine. Background: Soccer is one of the most popular worldwide sports and performance is dependentuponmanyfactors including technical, biomechanical, tactical, psychological and physiological aspects. Previous investigations have identified that the frequency of goals increases as matches progress, however, previous research in this area is limited as it is based on data from very few competitions. Objectives: The aim of the present study was to examine the goal scoring patterns between two major international tournaments, the 2016 European championship and the 2016 Copa America. Methods: The sample consisted of 83 games: 51 games from the 2016 European Championship and 32 from the 2016 Copa America. Results: A total of 197 goals scored in 83 games were analysed. Analyses revealed that a significantly greater percentage of total match goals were scored in the first half Copa America matches compared to the European championship (47.8% vs. 39.3%, P = 0.02). No differences were found in the second half between tournaments. There was a significantly higher goal scoring frequency in the second half (60.7%) compared to the first half (39.3%) in the European championship (P = 0.02), but no differences were found between halves for the Copa America. Chi square analysis revealed a significantly (P < 0.01) higher goal scoring frequency in the first 15-minute interval for the Copa America (24%) compared to the first 15 minutes of the European Championship (12%). Conclusions: The findings of this study indicate that South American nations appear to take an offensive approach in the first 15 minutes which is indicative that there may be a country-related style of play related to goal scoring patterns in major international tournaments. Future studies need to extend this research across several international tournaments and/or between club versus country to determine if there is a country-related style of play element to goal scoring patterns between European and South American international tournaments

Seasonal changes in physical capacities of basketball players according to competitive levels and individual responses

PURPOSE:The aim of this study was to quantify changes in physical capacities of thirty-eight basketball players selected from different teams, as well as from varying competitive levels (i.e. Division I, Division II and Division III) during the preparation and in-season periods. METHODS:Pre (T1) and post (T2) preparation period and during regular season (T3), the players completed a Yo-Yo Intermittent Recovery test-level 1. Following a 3 to 8 days-break, players performed a 6-min continuous running test (Mognoni's test), a counter-movement jump test and a 5-min high-intensity intermittent running test. RESULTS:Blood lactate concentration measured after the Mognoni's test was significantly reduced from T1 to T2, and from T2 to T3 (P<0.001, ƞ2 = 0.424). The distance covered during the Yo-Yo Intermittent Recovery test was significantly increased only from T1 to T2 in Division II and III (P<0.001, ƞ2 = 0.789). Similarly, the physiological responses to high-intensity intermittent running test were improved only from T1 to T2 (all P<0.001, ƞ2 = 0.495 to 0.652). Despite significant changes observed in running tests from T1 to T2, at individual level 35-55% of players did not show a very likely improvement. Relative peak power produced during vertical jumps at T3 by Division I players was increased compared to T1 (ANOVA interaction, P = 0.037, ƞ2 = 0.134). CONCLUSIONS:The main improvements in physical capacities occurred during the preparation period, when the aerobic fitness and the ability to sustain high-intensity intermittent efforts were moderately-to-largely improved. However, it appears that the preparation period does not consistently impact on vertical jump variables. Aerobic fitness and force/power production during vertical jumps appear to improve across the competitive season (slightly-to-moderately). Physical tests should be used to identify weaknesses in physical performance of players and to monitor their fatigue status, with the aim to develop individualized training programs

Interpreting physical performance in professional soccer match-play: Should we be more pragmatic in our approach?

Academic and practitioner interest in the physical performance of male professional soccer players in the competition setting determined via time-motion analyses has grown substantially over the last four decades leading to a substantial body of published research and aiding development of a more systematic evidence-based framework for physical conditioning. Findings have forcibly shaped contemporary opinions in the sport with researchers and practitioners frequently emphasising the important role that physical performance plays in match outcomes. Time-motion analyses have also influenced practice as player conditioning programmes can be tailored according to the different physical demands identified across individual playing positions. Yet despite a more systematic approach to physical conditioning, data indicate that even at the very highest standards of competition, the contemporary player is still susceptible to transient and end-game fatigue. Over the course of this article, the author suggests that a more pragmatic approach to interpreting the current body of time-motion analysis data and its application in the practical setting is nevertheless required. Examples of this are addressed using findings in the literature to examine: a) the association between competitive physical performance and ‘success’ in professional soccer, b) current approaches to interpreting differences in time-motion analysis data across playing positions and, c) whether data can realistically be used to demonstrate the occurrence of fatigue in match-play. Gaps in the current literature and directions for future research are also identified

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

The preparation period in basketball: Training load and neuromuscular adaptations

© 2018 Human Kinetics, Inc. Purpose: To investigate the effect of the preparation period on neuromuscular characteristics of 12 professional (PRO) and 16 semiprofessional (SEMIPRO) basketball players and relationships between training-load indices and changes in neuromuscular physical performance. Methods: Before and after the preparation period, players underwent a countermovement jump (CMJ) test followed by a repeated change-of-direction (COD) test consisting of 4 levels with increasing intensities. The peripheral neuromuscular functions of the knee extensors (peak torque [PT]) were measured using electrical stimulations after each level (PT1, PT2, PT3, and PT4). Furthermore, PT Max (the highest value of PT) and PT Dec (PT decrement from PT Max to PT4) were calculated. Results: Trivial to small (effect size [ES] = -0.17 to 0.46) improvements were found in CMJ variables, regardless of competitive level. After the preparation period, peripheral fatigue induced by a COD test was similarly reduced in both PRO (PT Dec: from 27.8% [21.3%] to 11.4% [13.7%]; ES = -0.71; 90% confidence interval [CI], ±0.30) and SEMIPRO (PT Dec: from 26.1% [21.9%] to 10.2% [8.2%]; ES = -0.69; 90% CI, ±0.32). Moderate to large relationships were found between session rating of perceived exertion training load and changes in peak power output (PPO) measured during the CMJs (rs [90% confidence interval]: PPOabs, -.46 [±.26]; PPOrel, -.53 [±.23]) and in some PTs measured during the COD test (PT1, -.45 [±.26]; PT2, -.44 [±.26]; PT3, -.40 [±.27]; and PT Max, -.38 [±.28]). Conclusions: The preparation period induced minimal changes in the CMJ, while the ability to sustain repeated COD efforts was improved. Reaching high session rating of perceived exertion training loads might partially and negatively affect the ability to produce strength and power

Bilateral asymmetry of skin temperature is not related to bilateral asymmetry of crank torque during an incremental cycling exercise to exhaustion

© 2018 Trecroci et al. Although moderate relationships (|r|~0:5) were reported between skin temperature and performance-related variables (e.g., kinetic), it remains unclear whether skin temperature asymmetry reflects muscle force imbalance in cycling. Therefore, the aim of this study was to assess whether a relationship exists between kinetic and thermal asymmetry during a fatiguing exercise. Ten elite cyclists were enrolled and tested on a maximal incremental cycling test. Peak crank torques of both legs were obtained at the initial and final workload. Likewise, bilateral skin temperatures were recorded before and after exercise. Asymmetric indexes were also calculated for kinetic (AIK) and skin temperature (AIT) outcomes. The bilateral peak crank torques showed a larger difference at the final compared to the initial workload (p0:05). Additionally, trivial relationships were reported between AIK and AIT (-0:3<r<0:2) at the initial and final workload. The obtained results showed that changes in bilateral kinetic values did not reflect concurrent changes in bilateral skin temperatures. This finding emphasizes the difficulty of associating the asymmetry of skin temperature with those of muscle effort in elite cyclists. Lastly, our study also provided further insights on thermal skin responses during exhaustive cycling exercise in very highly-trained athletes

Implementing concurrent-training and nutritional strategies in professional football: a complex challenge for coaches and practitioners

Purpose: To study concurrent-training (CT) and nutritional practices within a professional soccer team. Methods: Twenty-one professional football players competing in the English professional league participated in this study (mean ± standard deviations [M ± SD] 26 ± 4 years, stature 1.84 ± 0.1 m, body mass 83 ± 7 kg, VO2max; 58 ± 3 ml · kg−1 · min−1). A range of internal and external training metrics, the organisation of CT (training sequence, training rest period between bouts) and the nutritional intake around CT (timing, type and quantity) was collected for 10 weeks. Results: CT; n = 17 (endurance-training [ET] + resistance-training [RT]; n = 11; RT + ET; n = 6) rest period between bouts was not consistent and varied depending on the sequence of CT (RT + ET, 75 ± 48 min; ET + RT; 60 ± 5 min; P = 0.04). sRPE of football-specific ET was higher in RT + ET (RT + ET, 7 ± 1; ET + RT, 6 ± 1; P = 0.05). The timing of meals around training was influenced by the organisation of CT. Subsequently, CHO consumption before training session one was significantly less in RT + ET (CHO 0.10 ± 0.5 g · kg−1 vs. CHO 0.45 ± 0.2 g · kg−1). Conclusion: The present data demonstrate that the organisation of CT (i.e., exercise order and/or recovery time between bouts) and nutrition (i.e., timing of meal intake) can be unsystematic in the applied environment. The organisation of training and nutrition might influence the players’ ability to perform high-intensity actions in secondary training sessions and could potentially impact acute metabolic processes associated with muscle recovery and muscle adaptation

Common spatiotemporal processing of visual features shapes object representation

none10Biological vision relies on representations of the physical world at different levels of complexity. Relevant features span from simple low-level properties, as contrast and spatial frequencies, to object-based attributes, as shape and category. However, how these features are integrated into coherent percepts is still debated. Moreover, these dimensions often share common biases: for instance, stimuli from the same category (e.g., tools) may have similar shapes. Here, using magnetoencephalography, we revealed the temporal dynamics of feature processing in human subjects attending to objects from six semantic categories. By employing Relative Weights Analysis, we mitigated collinearity between model-based descriptions of stimuli and showed that low-level properties (contrast and spatial frequencies), shape (medial-axis) and category are represented within the same spatial locations early in time: 100-150 ms after stimulus onset. This fast and overlapping processing may result from independent parallel computations, with categorical representation emerging later than the onset of low-level feature processing, yet before shape coding. Categorical information is represented both before and after shape, suggesting a role for this feature in the refinement of categorical matching.nonePapale, Paolo; Betta, Monica; Handjaras, Giacomo; Malfatti, Giulia; Cecchetti, Luca; Rampinini, Alessandra; Pietrini, Pietro; Ricciardi, Emiliano; Turella, Luca; Leo, AndreaPapale, Paolo; Betta, Monica; Handjaras, Giacomo; Malfatti, Giulia; Cecchetti, Luca; Rampinini, Alessandra; Pietrini, Pietro; Ricciardi, Emiliano; Turella, Luca; Leo, Andre

Peripheral Muscle Function During Repeated Changes of Direction in Basketball

PURPOSE: To examine differences between adult male basketball players of different competitive levels (study 1) and changes over a basketball season (study 2) of knee extensor peripheral muscle function during a multi-stage changes of direction exercise (MCODE). METHODS: In study 1, 111 players from 4 different divisions completed the MCODE during the regular season. In study 2, the MCODE was performed before (T1) and after (T2) the preparation period and during the competitive season (T3) by 32 players from division I, II and III. The MCODE comprised 4 levels of increasing intensity for each player. The peak twitch torque (PT) of knee extensors was measured after each level. PTmax (the highest value of PT) and fatigue were calculated. RESULTS: In study 1, we found possibly small differences (ES\ub190%CI: -0.24\ub10.39) in fatigue between division I and II. Division I was characterized by likely (ES: 0.30 to 0.65) and very likely-to-almost certain (ES: 0.74 to 1.41) better PTmax and fatigue levels compared to division III and VI, respectively. In study 2, fatigue was very likely reduced (ES: -0.91 to -0.51) among all divisions from T1 to T2, while PTmax was likely-to-very likely reduced (ES: -0.51 to -0.39) in division II and III. CONCLUSIONS: Professional basketball players are characterized by a better peripheral muscle function during a MCODE. Most of the seasonal changes in peripheral muscle function occurred after the preparation period. These findings inform practitioners on the development of training programs to enhance the ability to sustain repeated changes of direction efforts