Search

Purpose To define based on expert opinion and practical experience using a systematic and scientific approach, (1) the perceived most effective exercise-based strategies to prevent muscle injury in elite footballers; and, (2) when and how these exercise programs are prescribed based on the number of days between games i.e. implementation strategy. Methods A Delphi survey obtained opinions and assessed for agreement. Delphi respondents consisted of 21 experienced sports practitioners (12 ± 5.3 years in elite football and with an academic background) belonging to 18 teams from the Big-5 European football leagues; England, France, Germany, Italy, Spain. Three teams were represented collaboratively by two experts. The Delphi process involves sequential rounds each evolving based on the responses from the previous. The number of rounds is not pre-defined and continues until an agreement is either achieved or it is clear that no agreement will be reached. Frequency of responses was recorded where the agreement was sought (i.e. in closed questions) and an agreement was achieved if ≥ 13/18 (70%) respondents agreed. For open-ended questions, a qualitative content analysis was performed to identify recurring themes and when themes were specified by ≥ 13 (70%), these were also considered as reaching an agreement. Practitioners had the opportunity to raise concerns if they disagreed with the ‘agreement from recurrent themes’. Results There were four Delphi rounds (100% response for each round). Sprinting and High-Speed Running (HSR) focused exercises were agreed as most effective (perceived) to prevent muscle injuries. Eccentric exercise was perceived as the next most effective. It was agreed that sprinting and HSR be integrated into coaches training, and target 100% of players worst-case match scenario (e.g. volume, intensity) based on individual maximum speeds. Eccentric exercise was recommended to be implemented according to the context of the main football session and planned/actual sprinting and HSR content. It was agreed that eccentrics can be performed before or after training, context dependent. The day to perform specific sprinting and HSR or eccentric exercises depended on the proximity of previous and upcoming matches. Other exercises reaching agreement as ‘somewhat effective’ included concentric and isometric, horizontal and vertical plyometrics, coordination, core and dynamic flexibility in addition to core stability. No agreement was reached for multi-joint, resisted sprinting, kicking or agility exercises nor simultaneous single-leg strength and stability. Finally, no agreement was reached regarding programming variables e.g. sets, repetitions as deemed too contextual. Conclusion Regarding exercise-based strategies, particular importance agreed by the Delphi expert group was to focus on sprinting, HSR and eccentric exercises, integrated with a variety of other exercise modes which also carry some level of effectiveness in a multidimensional programme. Context was agreed to be key and decision-making about when to undertake/ how to prescribe exercise strategies to be made according to the content of normal football training and the proximity of matches.

Background: Wearable resistance (WR) training is a modality that allows athletes to perform loaded sport-specific movements to develop force and power outputs. The acute responses by which WR works is still relatively unknown, and the effects of WR load and location of the load has not yet been examined. Objectives: To investigate the acute neuromuscular and stride characteristic responses to different wearable resistance (WR) loads and placements on the calf muscles during high-speed running. Methods: Ten well-trained subjects completed a workout of ten sets of three 10s runs at 18km.h-1 (20s of rest between runs and one min between sets). Five conditions were tested: (1) unloaded control, (2) bilateral 0.75 vs. 1.5% body mass (BM) loading on the distal posterior calf, (3) bilateral proximal vs. distal loading of 1.5% BM positioned posteriorly, (4) bilateral anterior vs. posterior loading of 1.5% BM positioned distally, (5) unilateral loading of 1.5% BM on the distal posterior calf. Data were collected using Electromyography (EMG) and back-mounted GPS-embedded accelerometers. Magnitude of differences of within athlete and between muscle comparisons were calculated using effect sizes (ES) ± 90% confidence limits (CL). Results: No substantial differences in accelerometry data were observed between any of the loaded conditions and the control. EMG activity was lower for proximal loading compared to the control for the gluteus maximus (ES±90%CL; -0.72±0.41), vastus lateralis (-0.89±0.47) and vastus medialis (VM) (-0.97±0.46). Anterior loading induced substantially lower EMG activity for the semitendinosus (-0.70±0.48) and VM (-0.64±0.39) muscles compared with the control. EMG activity of the VM (-0.73±0.46) muscle was also substantially lower for posterior loading compared to the control. Unilateral loading induced no substantial differences in EMG activity between the loaded and unloaded legs. Conclusion: This preliminary study has provided a rationale for the performance of further investigations into the effects of WR lower limb loading on stride characteristics and EMG activity from a chronic standpoint using a larger population.

To compare the effects of different hypoxia severities on exercise capacity, cardio-respiratory, tissue oxygenation and neuromuscular fatigue characteristics in response to exhaustive intermittent cycling. Eleven well-trained cyclists, repeated supra-maximal cycling efforts of 15 s (30% of anaerobic power reserve, 609 ± 23 W), interspersed with 45 s of passive rest until task failure. The exercise was performed on separate days in normoxia (SL; simulated altitude/end-exercise arterial oxygen saturation = 0 m/~ 96%), moderate (MH; 2200 m/~ 90%) and severe (SH; 4200 m/~ 79%) hypoxia in a cross-over design. Neuromuscular tests, including brief (5 s) and sustained (30 s) maximal isometric voluntary contractions of the knee extensors, were performed at baseline and exhaustion. Exercise capacity decreased with hypoxia severity (23 ± 9, 16 ± 6 and 9 ± 3 cycle efforts in SL, MH and SH, respectively; P

Participation in soccer match-play leads to acute and transient subjective, biochemical, metabolic and physical disturbances in players over subsequent hours and days. Inadequate time for rest and regeneration between matches can expose players to the risk of training and competing whilst not entirely recovered. In professional soccer, contemporary competitive schedules can require teams to compete in excess of 60 matches over the course of the season with periods of fixture congestion occurring, prompting much attention from researchers and practitioners to the monitoring of fatigue and readiness to play. A comprehensive body of research has investigated post-match acute and residual fatigue responses. Yet the relevance of the research for professional soccer contexts is debatable, notably in relation to the study populations and designs employed. Monitoring can indeed be invasive, expensive, time inefficient, and difficult to perform routinely and simultaneously in a large squad of regularly competing players. Uncertainty also exists regarding the meaningfulness and interpretation of changes in fatigue response values and their functional relevance, and practical applicability in the field. The real-world need and cost-benefit of monitoring must be carefully weighed up. In relation to professional soccer contexts, this opinion paper intends to (1) debate the need for post-match fatigue monitoring; (2) critique the real-world relevance of the current research literature; (3) discuss the practical burden relating to measurement tools and protocols, and the collection, interpretation and application of data in the field; and (4) propose future research perspectives.

The purpose of this investigation was to determine the acute effects of back squats on countermovement jump performance across multiple sets using a strength-power potentiation complex training protocol. Fifteen elite volleyball players performed three unloaded countermovement jumps (CMJ) following three repetitions of the back squat performed at either 65% or 87% of 1-RM, respectively, repeated for 10 sets. A control session of three CMJs was also repeated for 10 sets. Mean jump height performance was enhanced compared to performing CMJs only irrespective of which intensity was used (65% 1-RM: +3.3 ± 2.2% [CI: 1.0 to 5.6]; 87% 1-RM: 2.6 ± 1.9% [CI: 0.7 to 4.5]). Subjects with a greater relative strength possessed a very likely large (97%; ES = 1.51) chance of improvement in jump height across 10 sets of the protocol prescribed using the intensity of 87% 1-RM and a likely moderate (89%; ES = 0.94) and very likely large (97%; ES = 1.76) chance of improvement in maximum concentric impulse (N·s) using intensities of 65% and 87%1-RM, respectively. Performance (jump height and maximum concentric impulse) may be enhanced across 10 sets of the strength power potentiation complex training protocol prescribed irrespective of intensity, with a greater effect observed for the subjects with a greater relative strength and with the 87% 1-RM heavy load back squat condition. In practice, coaches should consider the athlete’s strength level when designing such a complex training protocol to generate any post-activation potentiation effect across multiple alternating sets to enhance jump performance.

The aim of the present study was to examine the ability of a GPS-imbedded accelerometer to assess stride variables and vertical stiffness (K), which are directly related to neuromuscular fatigue during field-based high-intensity runs. The ability to detect stride imbalances was also examined. A team sport player performed a series of 30-s runs on an instrumented treadmill (6 runs at 10, 17 and 24 km·h-1) with or without his right ankle taped (aimed at creating a stride imbalance), while wearing on his back a commercially-available GPS unit with an embedded 100-Hz tri-axial accelerometer. Contact (CT) and flying (FT) time, and K were computed from both treadmill and accelerometers (Athletic Data Innovations) data. The agreement between treadmill (criterion measure) and accelerometer-derived data was examined. We also compared the ability of the different systems to detect the stride imbalance. Biases were small (CT and K) and moderate (FT). The typical error of the estimate was trivial (CT), small (K) and moderate (FT), with nearly perfect (CT and K) and large (FT) correlations for treadmill vs. accelerometer. The tape induced very large increase in the right - left foot ∆ in CT, FT and K measured by the treadmill. The tape effect on CT and K ∆ measured with the accelerometers were also very large, but of lower magnitude than with the treadmill. The tape effect on accelerometer-derived ∆ FT was unclear. Present data highlight the potential of a GPS-embedded accelerometer to assess CT and K during ground running.

We investigated the evolution and stability of anthropometric and soccer-specific endurance characteristics of 42 high-level, pubertal soccer players with high, average and low yo-yo intermittent recovery test level 1 (YYIR1) baseline performances over two and four years. The rates of improvement were calculated for each performance group, and intra-class correlations were used to verify short- and long-term stability. The main finding was that after two and four years, the magnitudes of the differences at baseline were reduced, although players with high YYIR1 baseline performance still covered the largest distance (e.g., low from 703 m to 2126 m; high from 1503 m to 2434 m over four years). Furthermore, the YYIR1 showed a high stability over two years (ICC = 0.76) and a moderate stability over four years (ICC = 0.59), due to large intra-individual differences in YYIR1 performances over time. Anthropometric measures showed very high stability (ICCs between 0.94 to 0.97) over a two-year period, in comparison with a moderate stability (ICCs between 0.57 and 0.75) over four years. These results confirm the moderate-to-high stability of high-intensity running performance in young soccer players, and suggest that the longer the follow-up, the lower the ability to predict player’s future potential in running performance. They also show that with growth and maturation, poor performers might only partially catch up their fitter counterparts between 12 and 16 years.

To compare relative match intensities of sea-level versus high-altitude native soccer players during a 2-week camp at 3600 m, data from 7 sea-level (Australian U17 National team, AUS) and 6 high-altitude (a Bolivian U18 team, BOL) native soccer players were analysed. Two matches were played at sea-level and three at 3600 m on Days 1, 6 and 13. The Yo-Yo Intermittent recovery test (vYo-YoIR1) was performed at sea-level, and on Days 3 and 10. Match activity profiles were measured via 10-Hz GPS. Distance covered >14.4 km.h-1 (D>14.4 km·h-1) and >80% of vYo-YoIR1 (D>80%vYo-YoIR1) were examined. Upon arrival at altitude, there was a greater decrement in vYo-YoIR1 (Cohen’s d +1.0, 90%CL ± 0.8) and D>14.4 km·h-1 (+0.5 ± 0.8) in AUS. D>14.4 km.h-1 was similarly reduced relative to vYo-YoIR1 in both groups, so that D>80%vYo-YoIR1 remained similarly unchanged (-0.1 ± 0.8). Throughout the altitude sojourn, vYo-YoIR1 and D>14.4 km·h-1 increased in parallel in AUS, so that D>80%vYo-YoIR1 remained stable in AUS (+6.0%/match, 90%CL ± 6.7); conversely D>80%vYo-YoIR1 decreased largely in BOL (-12.2%/match ± 6.2). In sea-level natives competing at high-altitude, changes in match running performance likely follow those in high-intensity running performance. Bolivian data confirm that increases in ‘fitness’ do not necessarily translate into greater match running performance, but rather in reduced relative exercise intensity.

The aims of this study were to 1) investigate the influence of ground travel on wellness measures, and 2) examine the possible influence of travel distance and fitness on the magnitude of these possible changes. Compared with home matches, wellness measures showed moderate-to-large impairments of wellness of soccer players for away matches the day prior to the match (D-1) (range; +5 to 68%, [90%CL 1-88]; standardized difference: range; +.6 to +1.75 [.1-2.07]) and small-to-large impairments the day of the match (D-0, range; +7 to +68.1 [-1.6-87.5]; standardized difference, range; +.24 to 1.78, [-.06-2.15]), respectively. There were large and very large negative relationships between the increases of fatigue (r = -.84, 90%CL -.95; -.56) or soreness (at D-1 r = -.80, -.93; -.84) and players’ fitness. There were also very large positive correlations between actual wellness measures and traveling distance to away locations (r range; .70 to .87). Ground travel-induced impairment of wellness is associated with fitness and distance of away locations in young soccer players. Simple wellness questionnaires could be used to effectively monitor young soccer players’ freshness and readiness to train or compete during away games.

The aim of the present study was to propose a new and simple field assessment of inter-effort recovery and change of direction (COD) ability based on performance during the 30-15 Intermittent Fitness Test (30-15IFT, an intermittent, incremental shuttle-run test) using three different protocols. Forty team-sport players (22 ± 2 years) performed either (group A; n = 16) the original 30-15IFT and two modified versions, one without a rest period (i.e. continuous run, 30-15IFT-CONT) and one without COD (30-15IFT-LINE), or (group B; n = 24) the original 30-15IFT and a modified version with more COD (28-m shuttle instead of 40-m, 30- 15IFT-28m). Heart rate (HR), blood lactate concentration ([La]b), rating of perceived exertion (RPE) and maximal running speed were recorded for all tests. There was no statistical difference in either maximal HR (A: p = 0.07 and B: p = 0.94) or RPE (A: p = 0.10 and B: p = 0.97) between tests. Compared with the 30-15IFT (12.3 ± 2.5, p0.01) and 30-15IFT-LINE (11.3 ± 2.6, p = 0.07, ES = 0.61), [La]b was lower for 30-15IFT-CONT (9.6 ± 3.3 mmol.L(-1)). Compared with 30-15IFT, maximal running speed was higher for 30-15IFT-LINE (103.1 ± 1.7%, p0.001) and lower for 30-15IFT-CONT (93.2 ± 1.4%, p0.001), while it was similar for 30-15IFT-28m (99.7 ± 3.6%, p = 0.62). Maximal speeds reached after the four tests were significantly but not perfectly correlated (r = 0.74 to 95, all p0.001). Present results show that differences in the maximal running speed reached following different versions of the 30-15IFT can be used by coaches to isolate and evaluate inter- effort recovery (i.e. 30-15IFT vs. 30-15IFT-CONT) and COD (i.e., 30-15IFT vs. 30-15IFT-LINE) abilities in the field. Additionally, COD ability as evaluated here appears to be independent of shuttle-length. Key pointsThe comparison of the maximal running speed reached at the original 30-15IFT with these reached at two modified protocols (i.e., 30-15IFT-CONT and 30-15IFT-LINE ) enables a simple and field-based assess-ment of between-efforts recovery and COD abilities during high-intensity runs.These data can be used by coaches to complete the physical profiling of each player, which could high-light the need for specific training interventions.

The aims of the present study were to examine: 1) the validity and reliability of a new timing system to assess running kinematics during change of direction (COD), and 2) the determinants of COD-speed. Twelve young soccer players performed three 20-m sprints, either in straight line or with one 45º- or 90º- COD. Sprints were monitored using timing gates and two synchronized 100-Hz laser guns, to track players’ velocities before, during and after the COD. The validity analysis revealed trivial-to-small biases and small-to-moderate typical errors of the estimate with the lasers compared with the timing gates. The reliability was variable-dependent, with trivial- (distance at peak speed) to-large (distance at peak deceleration) typical errors. Kinematic variables were angle-dependent, with likely lower peak speed, almost-certainly slower minimum speed during the COD and almost-certainly greater deceleration reached for 90º-COD vs. 45º- COD sprints. The minimum speed during the COD was largely correlated with sprint performance for both sprint angles. Correlations with most of the other independent variables were unclear. The new timing system showed acceptable levels of validity and reliability to assess some of the selected running kinematics during COD sprints. The ability to maintain a high speed during the COD may be the determinant of COD-speed.

© 2015 Aubry et al This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Purpose: The aim of the study was to investigate whether heart rate recovery (HRR) may represent an effective marker of functional overreaching (f-OR) in endurance athletes. Methods and Results: Thirty-one experienced male triathletes were tested (10 control and 21 overload subjects) before (Pre), and immediately after an overload training period (Mid) and after a 2-week taper (Post). Physiological responses were assessed during an incremental cycling protocol to exhaustion, including heart rate, catecholamine release and blood lactate concentration. Ten participants from the overload group developed signs of f-OR at Mid (i.e. -2.1 ± 0.8% change in performance associated with concomitant high perceived fatigue). Additionally, only the f-OR group demonstrated a 99% chance of increase in HRR during the overload period (+8 ± 5 bpm, large effect size). Concomitantly, this group also revealed a >80% chance of decreasing blood lactate (-11 ± 14%, large), plasma norepinephrine (-12 ± 37%, small) and plasma epinephrine peak concentrations (-51 ± 22%, moderate). These blood measures returned to baseline levels at Post. HRR change was negatively correlated to changes in performance, peak HR and peak blood metabolites concentrations. Conclusion: These findings suggest that i) a faster HRR is not systematically associated with improved physical performance, ii) changes in HRR should be interpreted in the context of the specific training phase, the athletes perceived level of fatigue and the performance response; and, iii) the faster HRR associated with f-OR may be induced by a decreased central command and by a lower chemoreflex activity.

International audience; Abstract The aim of the present study was to examine, in highly trained young soccer players, the mechanical horizontal determinants of acceleration (Acc) and maximal sprinting speed (MSS). Eighty-six players (14.1 ± 2.4 year) performed a 40-m sprint to assess Acc and MSS. Speed was measured with a 100-Hz radar, and theoretical maximal velocity (V0), horizontal force (F0) and horizontal power (Pmax) were calculated. Within each age group, players were classified as high Acc/fast MSS (>2% faster than group mean), medium (between -2% and +2%), and low/slow (>2% slower). Acc and MSS were very largely correlated (-0.79; 90% confidence limit [-0.85; -0.71]). The determinants (multiple regression r2 = 0.84 [0.78; 0.89]) of Acc were V0 (partial r: 0.80 [0.72; 0.86]) and F0 (0.57 [0.44; 0.68]); those of MSS (r2 = 0.96 [0.94; 0.97]) were V0 (0.96 [0.94; 0.97]) and Pmax (0.73 [0.63; -0.80]). High/Med have likely greater F0 (Cohen's d: +0.8 [0.0; 1.5]), V0 (+0.6 [-0.1; 1.3]) and Pmax (+0.9 [0.2; 1.7]) than Low/Med. High/Fast have an almost certainly faster V0 (+2.1 [1.5; 2.7]) and a likely greater Pmax (+0.6 [-0.1; 1.3]) than High/Med, with no clear differences in F0 (-0.0 [-0.7; 0.6]). Speed may be a generic quality, but the mechanical horizontal determinants of Acc and MSS differ. While maximal speed training may improve both Acc and MSS, improving horizontal force production capability may be efficient to enhance sprinting performance over short distances.

To examine the effects of body size on locomotor performance, 807 15-year-old French and 64 Qatari soccer players participated in the present study. They performed a 40-m sprint and an incremental running test to assess maximal sprinting (MSS) and aerobic speeds, respectively. French players were advanced in maturity, taller, heavier, faster and fitter than their Qatari counterparts (e.g., Cohen’s d=+1.3 and + 0.5 for body mass and MSS). However, when adjusted for body mass (BM), Qatari players had possibly greater MSS than French players (d=+0.2). A relative age effect was observed within both countries, with the players born in the first quarter of the year being taller, heavier and faster that those born during the fourth quarter (e.g., d=+0.2 for MSS in French players). When directly adjusted for BM, these MSS differences remained (d=+0.2). Finally, in both countries, players selected in National teams were taller, heavier, faster and fitter than their non-selected counterparts (e.g., d=+0.6 for MSS in French players), even after adjustments for body size (d=+0.5). Differences in locomotor performances between players with different phenotypes are likely mediated by differences in body size. However, when considering more homogeneous player groups, body dimensions are unlikely to substantially explain the superior locomotor performances of older and/or international players.

It has been suggested that the time spent at a high stroke volume (SV) is important for improving maximal cardiac function. The aim of this study was to examine the effect of recovery intensity on cardiovascular parameters during a typical high-intensity interval training (HIIT) session in fourteen well-trained cyclists. Oxygen consumption (VO2), heart rate (HR), SV, cardiac output (Qc), and oxygenation of vastus lateralis (TSI) were measured during a HIIT (3×3-min work period, 2 min of recovery) session on two occasions. VO2, HR and Qc were largely higher during moderate-intensity (60%) compared with low-intensity (30%) (VO2, effect size; ES = +2.6; HR, ES = +2.8; Qc, ES = +2.2) and passive (HR, ES = +2.2; Qc, ES = +1.7) recovery. By contrast, there was no clear difference in SV between the three recovery conditions, with the SV during the two active recovery periods not being substantially different than during exercise (60%, ES = -0.1; 30%, ES = -0.2). To conclude, moderate-intensity recovery may not be required to maintain a high SV during HIIT. Key pointsModerate-intensity recovery periods may not be necessary to maintain high stroke volume during the exercise intervals of HIIT.Stroke volume did not surpass the levels attained during the exercise intervals during the recovery periods of HIIT.The practical implication of these finding is that reducing the intensity of the recovery period during a HIIT protocol may prolong the time to exhaustion, potentially allowing completion of additional high-intensity intervals increasing the time accumulated at maximal cardiac output.

Monitoring an athlete's physiological status in response to various types and volumes of (aerobic-oriented) training can provide useful information for optimizing training programs. Measures of resting, exercise and recovery heart rate (HR) are receiving increasing interest for monitoring fatigue, fitness and endurance performance responses, which has direct implications for adjusting training load 1) daily during specific training blocks and 2) throughout the competitive season. These measures are still not widely implemented to monitor athletes’ responses to training load, probably because of apparent contradictory findings in the literature. In this review I contend that most of the contradictory findings are related to methodological inconsistencies and/or misinterpretation of the data rather than to limitations of heart rate measures to accurately inform on training status. I also provide evidence that measures derived from 5-min (almost daily) recordings of resting (indices capturing beat-to-beat changes in HR, reflecting parasympathetic activity) and submaximal exercise (30- to 60-s average) HR are likely the most useful monitoring tools. For appropriate interpretation at the individual level, changes in a given measure should be interpreted by taking into account the error of measurement and the smallest important change of the measure, as well as the training context (training phase, load and intensity distribution). The decision to use a given measure should be based upon the level of information that is required by the athlete, the marker’s sensitivity to changes in training status and the practical constrains required for the measurements. However, measures of HR cannot inform on all aspects of wellness, fatigue and performance, so their use in combination with daily training logs, psychometric questionnaires and non-invasive, cost-effective performance tests such as a countermovement jump may offer a complete solution to monitor training status

While a relative age effect (RAE) has been reported in handball, such analyses do not consider the actual playing time during competitions, which may actually have more impact on matches performance in matches. The objective of the present study was to examine the RAE on playing time during international competitions with respect to playing positions. Team compositions (477 players) of the quarter finalists of the 2012 Olympic Games, 2013 World Championships, and 2014 European Championship were analyzed. Month and year of birth where collected in the starting list of each team for center, left and right backs, left and right wings, goalkeepers and pivots. Players were categorized into birth quartile (Q1 Jan–Mar; Q2 Apr–Jun; Q3 Jul–Sep; and Q4 Oct–Dec) and as odd/even year. Playing times were retrieved from official statistics. Data were analyzed for practical significance using magnitude-based inferences. We observed a strong selection bias towards players born earlier within a two-year selection period for all playing positions (Chi-square, p, Iako je utjecaj relativne dobi igrača potvrđen u rukometu, takve analize ne uzimaju u obzir stvarno vrijeme provedeno u igri tijekom natjecanja, a što može snažnije utjecati na uspješnost tijekom utakmice. Cilj je ovog istraživanja bio utvrditi utjecaj relativne dobi igrača na vrijeme igranja tijekom međunarodnih natjecanja s obzirom na igračku poziciju. Analizirane su postave nacionalnih selekcija (477 igrača) koje su igrale četvrtinu finala na Olimpijskim igrama 2012. godine, Svjetskom prvenstvu 2013. te Europskom prvenstvu 2014. godine. Informacije o mjesecu i godini rođenja za srednje, lijeve i desne vanjske igrače, lijeva i desna krila, vratare i kružne napadače prikupljeni su iz službenih startnih popisa svake momčadi. Igrači su podijeljeni u kvartile definirane prema datumu rođenja (Q1 – siječanj do ožujak, Q2 – travanj do lipanj, Q3 – srpanj do rujan i Q4 – listopad do prosinac) te prema tomu jesu li rođeni u parnoj ili neparnoj godini. Vrijeme provedeno u igri za svakog igrača dobiveno je iz službenih statistika. Veličina učinka analizirana je u odnosu na minimalnu značajnu praktičnu vrijednost. Uočili smo snažnu selekcijsku pristranost prema igračima koji su rođeni ranije unutar dvogodišnjeg selekcijskog perioda za sve igračke pozicije (χ2, p

The question of whether altitude training can enhance subsequent sea-level performance has been well investigated over many decades. However, research on this topic has focused on athletes from individual or endurance sports, with scant number of studies on team-sport athletes. Questions that need to be answered include whether this type of training may enhance team-sport athlete performance, when success in team-sport is often more based on technical and tactical ability rather than physical capacity per se. This review will contrast and compare athletes from two sports representative of endurance (cycling) and team-sports (soccer). Specifically, we draw on the respective competition schedules, physiological capacities, activity profiles and energetics of each sport to compare the similarities between athletes from these sports and discuss the relative merits of altitude training for these athletes. The application of conventional live-high, train-high; live-high, train-low; and intermittent hypoxic training for team-sport athletes in the context of the above will be presented. When the above points are considered, we will conclude that dependent on resources and training objectives, altitude training can be seen as an attractive proposition to enhance the physical performance of team-sport athletes without the need for an obvious increase in training load.

Objectives: To examine the time course of wellness,fatigue and performance during an altitude training camp (La Paz, 3600 m) in two groups of either sea-level (Australian) or altitude (Bolivian) native young soccer players.Methods Wellness and fatigue were assessed using questionnaires and resting heart rate (HR) and HR variability. Physical performance was assessed using HR responses to a submaximal run, a Yo-Yo Intermittent recovery test level 1 (Yo-YoIR1) and a 20 m sprint. Most measures were performed daily, with the exception ofYo-YoIR1 and 20 m sprints, which were performed nearsea level and on days 3 and 10 at altitude. Results: Compared with near sea level, Australians had moderate-to-large impairments in wellness and Yo-YoIR1 relative to the Bolivians on arrival at altitude. The acclimatisation of most measures to altitude was substantially slower in Australians than Bolivians, with only Bolivians reaching near sea-level baseline high intensity running by the end of the camp. Both teams had moderately impaired 20 m sprinting at the end of the camp. Exercise HR had large associations (r>0.5-0.7)with changes in Yo-YoIR1 in both groups. Conclusions: Despite partial physiological and perceptual acclimatisation, 2 weeks is insufficient for restoration of physical performance in young sea-level native soccer players. Because of the possible decrement in 20 m sprint time, a greater emphasis on speed training may be required during and after altitude training. The specific time course of restoration for each variable suggests that they measure different aspects of acclimatisation to 3600 m; they should therefore be used in combination to assess adaptation to altitude. Refereed/Peer-reviewed

Background Altitude training is used by elite athletes to improve sports performance, but it may also disrupt sleep. The aim of this study was to examine the effects of 2 weeks at high altitude on the sleep of young elite athletes. Methods Participants (n=10) were members of the Australian under-17 soccer team on an 18-day (19-night) training camp in Bolivia, with six nights at near sea level in Santa Cruz (430 m) and 13 nights at high altitude in La Paz (3600 m). Sleep was monitored using polysomnography during a baseline night at 430 m and three nights at 3600 m (immediately after ascent,1 week after ascent and 2 weeks after ascent). Data were analysed using effect size statistics. Results All results are reported as comparisons with baseline. Rapid eye movement (REM) sleep was likely lower immediately upon ascent to altitude, possibly lower after 1 week and similar after 2 weeks. On all three nights at altitude, hypopneas and desaturations were almost certainly higher; oxygen saturation was almost certainly lower; and central apnoeas, respiratory arousals and periodic breathing were very likely higher. The effects on REM sleep were common to all but one participant, but the effects on breathing were specific to only half the participants.Conclusions The immediate effects of terrestrial altitude of 3600 m are to reduce the amount of REM sleep obtained by young elite athletes, and to cause 50% of them to have impaired breathing during sleep. REM sleep returns to normal after 2 weeks at altitude, but impaired breathing does not improve. Refereed/Peer-reviewed

Objectives We investigated the effect of high altitude on the match activity profile of elite youth high altitude and sea level residents. Methods Twenty Sea Level (Australian) and 19 Altitude-resident (Bolivian) soccer players played five games, two near sea level (430 m) and three in La Paz (3600 m). Match activity profile was quantified via global positioning system with the peak 5 min period for distance ((D5peak)) and high velocity running (>4.17 m/s, HIVR5peak); as well as the 5 min period immediately subsequent to the peak for both distance (D5sub) and high-velocity running (HIVR5sub) identified using a rolling 5 min epoch. The games at 3600 m were compared with the average of the two near sea-level games. Results The total distance per minute was reduced by a small magnitude in the first match at altitude in both teams, without any change in low-velocity running. There were variable changes in HiVR, D5peak and HiVR5peak from match to match for each team. There were within-team reductions in D5peak in each game at altitude compared with those at near sea level, and this reduction was greater by a small magnitude in Australians than Bolivians in game 4. The effect of altitude on HiVR5peak was moderately lower in Australians compared with Bolivians in game 3. There was no clear difference in the effect of altitude on maximal accelerations between teams. Conclusions High altitude reduces the distance covered by elite youth soccer players during matches. Neither 13 days of acclimatisation nor lifelong residence at high altitude protects against detrimental effects of altitude on match activity profile. Refereed/Peer-reviewed

Objectives To examine with a parallel group study design the performance and physiological responses to a 14-day off-season ‘live high-train low in the heat’ training camp in elite football players. Methods Seventeen professional Australian Rules Football players participated in outdoor football-specific skills (32±1°C, 11.5 h) and indoor strength (23±1°C, 9.3 h) sessions and slept (12 nights) and cycled indoors (4.3 h) in either normal air (NORM, n=8) or normobaric hypoxia (14±1 h/day, FiO 2 15.2–14.3%, corresponding to a simulated altitude of 2500–3000 m, hypoxic (HYP), n=9). They completed the Yo-Yo Intermittent Recovery level 2 (Yo-YoIR2) in temperate conditions (23±1°C, normal air) precamp (Pre) and postcamp (Post). Plasma volume (PV) and haemoglobin mass (Hb mass ) were measured at similar times and 4 weeks postcamp (4WPost). Sweat sodium concentration ((Na + ) sweat ) was measured Pre and Post during a heat-response test (44°C). Results Both groups showed very large improvements in Yo-YoIR2 at Post (+44%; 90% CL 38, 50), with no between-group differences in the changes (−1%; −9, 9). Postcamp, large changes in PV (+5.6%; −1.8, 5.6) and (Na + ) sweat (−29%; −37, −19) were observed in both groups, while Hb mass only moderately increased in HYP (+2.6%; 0.5, 4.5). At 4WPost, there was a likely slightly greater increase in Hb mass (+4.6%; 0.0, 9.3) and PV (+6%; −5, 18, unclear) in HYP than in NORM. Conclusions The combination of heat and hypoxic exposure during sleep/training might offer a promising ‘conditioning cocktail’ in team sports.

We examined the respective associations between aerobic fitness ([Formula: see text]max), metabolic control ([Formula: see text] kinetics) and locomotor function, and various physiological responses to high-intensity intermittent (HIT) running exercise in team sport players. Eleven players (30.5 ± 3.6 year) performed a series of tests to determine their [Formula: see text]max and the associated velocity (v[Formula: see text]max), maximal sprinting speed (MSS) and [Formula: see text] kinetics at exercise onset in the moderate and severe intensity domains, and during recovery ([Formula: see text] SEV). Cardiorespiratory variables, oxygenation and electromyography of lower limbs muscles and blood lactate ([La]) concentration were collected during a standardized HIT protocol consisting in 8 sets of 10, 4-s runs. During HIT, four players could not complete more than two sets; the others finished at least five sets. Metabolic responses to the two first sets of HIT were negatively correlated with [Formula: see text]max, v[Formula: see text]max, and [Formula: see text] SEV (r = -0.6 to -0.8), while there was no clear relationship with the other variables. [Formula: see text], oxygenation and [La] responses to the first two sets of HIT were the only variables that differed between the players which could complete at least five sets or those who could not complete more than two sets. Players that managed to run at least five sets presented, in comparison with the others, greater v[Formula: see text]max [ES = +1.5(0.4; 2.7), MSS(ES = +1.0(0.1; 1.9)] and training load [ES = +3.8 (2.8; 4.9)]. There was no clear between-group difference in any of the [Formula: see text] kinetics measures [e.g., ES = -0.1(-1.4; 1.2) for [Formula: see text] SEV]. While [Formula: see text]max and v[Formula: see text]max are likely determinant for HIT tolerance, the importance of [Formula: see text] kinetics as assessed in this study appears limited in the present population. Knowing the main factors influencing tolerance to HIT running exercise may assist practitioners in personalizing training interventions.

In this study we assessed the effect of acute hypoxia on post-exercise parasympathetic reactivation inferred from heart rate (HR) recovery (HRR) and HR variability (HRV) indices. Ten healthy males participated in this study. Following 10 min of seated rest, participants performed 5 min of submaximal running at the speed associated with the first ventilatory threshold (Sub) followed by a 20-s all-out supramaximal sprint (Supra). Both the Sub and Supra runs were immediately followed by 15 min of seated passive recovery. The resting and exercise sequence were performed in both normoxia (N) and normobaric hypoxia (H) (FiO2 = 15.4%). HRR indices (e.g., heart beats recovered in the first minute after exercise cessation, HRR60s) and vagal-related HRV indices (i.e., natural logarithm of the square root of the mean of the sum of the squared differences between adjacent normal R-R intervals (Ln rMSSD)) were calculated for both conditions. Difference in the changes between N and H for all HR-derived indices were also calculated for both Sub and Supra. HRR60s was greater in N compared with H following Sub only (60±14 vs. 52±19 beats.min-1, P = 0.016). Ln rMSSD was greater in N compared with H (post Sub: 3.60±0.45 vs. 3.28±0.44 ms in N and H, respectively and post Supra: 2.66±0.54 vs. 2.65±0.63 ms, main condition effect P = 0.02). When comparing the difference in the changes, hypoxia decreased HRR60s (-14.3%±17.2 vs. 5.2-0.5%±19.3; following Sub and Supra, respectively; P = 0.03) and Ln rMSSD (-8.6%±7.0 vs. 2.0%±13.3, following Sub and Supra, respectively; P = 0.08, Cohen’s effect size = 0.62) more following Sub than Supra. While hypoxia may delay parasympathetic reactivation following submaximal exercise, its effect is not apparent following supramaximal exercise. This may suggest that the effect of blood O2 partial pressure on parasympathetic reactivation is limited under heightened sympathetic activation.

The aim of the present study was to verify the validity of using exercise heart rate (HRex), HR recovery (HRR) and post-exercise HR variability (HRV) during and after a submaximal running test to predict changes in physical performance over an entire competitive season in highly trained young soccer players. Sixty-five complete data sets were analyzed comparing two consecutive testing sessions (3-4 months apart) collected on 46 players (age 15.1 ± 1.5 years). Physical performance tests included a 5-min run at 9 km h -1 followed by a seated 5-min recovery period to measure HRex, HRR and HRV, a counter movement jump, acceleration and maximal sprinting speed obtained during a 40-m sprint with 10-m splits, repeated-sprint performance and an incremental running test to estimate maximal cardiorespiratory function (end test velocity V Vam-Eval). Possible changes in physical performance were examined for the players presenting a substantial change in HR measures over two consecutive testing sessions (greater than 3, 13 and 10% for HRex, HRR and HRV, respectively). A decrease in HRex or increase in HRV was associated with likely improvements in V Vam-Eval; opposite changes led to unclear changes in V Vam-Eval. Moderate relationships were also found between individual changes in HRR and sprint [r = 0.39, 90% CL (0.07;0.64)] and repeated-sprint performance [r = -0.38 (-0.05;-0.64)]. To conclude, while monitoring HRex and HRV was effective in tracking improvements in V Vam-Eval, changes in HRR were moderately associated with changes in (repeated-)sprint performance. The present data also question the use of HRex and HRV as systematic markers of physical performance decrements in youth soccer players. Refereed/Peer-reviewed

The purpose of this study was to examine the effect of maturation on post-exercise hemodynamic and autonomic responses. Fifty-five highly trained young male soccer players (12-18years) classified as pre-, circum-, or post-peak height velocity (PHV) performed a graded running test to exhaustion on a treadmill. Before (Pre) and after (5th-10th min, Post) exercise, heart rate (HR), stroke volume (SV), cardiac output (CO), arterial pressure (AP), and total peripheral resistance (TPR) were monitored. Parasympathetic (high frequency [HF RR] of HR variability (HRV) and baroreflex sensitivity [Ln BRS]) and sympathetic activity (low frequency [LF SAP] of systolic AP variability) were estimated. Post-exercise blood lactate [La] b, the HR recovery (HRR) time constant, and parasympathetic reactivation (time-varying HRV analysis) were assessed. In all three groups, exercise resulted in increased HR, CO, AP and LF SAP (P< 0.001), decreased SV, HF RR, and Ln BRS (all P< 0.001), and no change in TPR (P=0.98). There was no "maturation xtime" interaction for any of the hemodynamic or autonomic variables (all P> 0.22). After exercise, pre-PHV players displayed lower SV, CO, and [La] b, faster HRR and greater parasympathetic reactivation compared with circum- and post-PHV players. Multiple regression analysis showed that lean muscle mass, [La] b, and Pre parasympathetic activity were the strongest predictors of HRR (r 2 = 0.62, P< 0.001). While pre-PHV players displayed a faster HRR and greater post-exercise parasympathetic reactivation, maturation had little influence on the hemodynamic and autonomic responses following maximal running exercise. HRR relates to lean muscle mass, blood acidosis, and intrinsic parasympathetic function, with less evident impact of post-exercise autonomic function. Refereed/Peer-reviewed

The aim of this study was to examine the effect of age and spa treatment (i.e. combined sauna, cold water immersion, and jacuzzi) on match running performance over two consecutive matches in highly trained young soccer players. Fifteen pre-(age 12.8±0.6 years) and 13 post-(15.9±1 y) peak height velocity (PHV) players played two matches (Matches 1 and 2) within 48 h against the same opposition, with no specific between-match recovery intervention (control). Five post-PHV players also completed another set of two consecutive matches, with spa treatment implemented after the first match. Match running performance was assessed using a global positioning system with very-high-intensity running (> 16.1-19.0 km h-1), sprinting distance (>19 km h-1), and peak match speed determined. Match 2 very-high-intensity running was "possibly" impaired in post-PHV players (-9±33%; ± 90% confidence limits), whereas it was "very likely" improved for the pre-PHV players (+27±22%). The spa treatment had a beneficial impact on Match 2 running performance, with a "likely" rating for sprinting distance (+30±67%) and "almost certain" for peak match speed (+6.4 ± 3%). The results suggest that spa treatment is an effective recovery intervention for post-PHV players, while its value in pre-PHV players is questionable. Refereed/Peer-reviewed

This study aimed to investigate the effect of cold and thermoneutral water immersion on post-exercise parasympathetic reactivation, inferred from heart rate (HR) recovery (HRR) and HR variability (HRV) indices. Twelve men performed, on three separate occasions, an intermittent exercise bout (all-out 30-s Wingate test, 5 min seated recovery, followed by 5 min of submaximal running exercise), randomly followed by 5 min of passive (seated) recovery under either cold (CWI), thermoneutral water immersion (TWI) or control (CON) conditions. HRR indices (e.g., heart beats recovered in the first minute after exercise cessation, HRR(60)(s)) and vagal-related HRV indices (i.e., natural logarithm of the square root of the mean of the sum of the squares of differences between adjacent normal R-R intervals (Ln rMSSD)) were calculated for the three recovery conditions. HRR(60)(s) was faster in water immersion compared with CON conditions [30+/-9 beats min(-)(1) for CON vs. 43+/- 10 beats min(-)(1) for TWI (P=0.003) and 40+/-13 beats min(-)(1) for CWI (P=0.017)], while no difference was found between CWI and TWI (P=0.763). Ln rMSSD was higher in CWI (2.32+/-0.67 ms) compared with CON (1.98+/-0.74 ms, P=0.05) and TWI (2.01+/-0.61 ms, P=0.08; aES=1.07) conditions, with no difference between CON and TWI (P=0.964). Water immersion is a simple and efficient means of immediately triggering post-exercise parasympathetic activity, with colder immersion temperatures likely to be more effective at increasing parasympathetic activity.

The activity profiles of highly trained young soccer players were examined in relation to age, playing position and physical capacity. Time-motion analyses (global positioning system) were performed on 77 (U13-U18; fullbacks [FB], centre-backs [CB], midfielders [MD], wide midfielders [W], second strikers [2 (nd)S] and strikers [S]) during 42 international club games. Total distance covered (TD) and very high-intensity activities (VHIA;16.1 km·h (-1)) were computed during 186 entire player-matches. Physical capacity was assessed via field test measures (e. g., peak running speed during an incremental field test, VVam-eval). Match running performance showed an increasing trend with age ( P0.001, partial eta-squared (η (2)): 0.20-0.45). When adjusted for age and individual playing time, match running performance was position-dependent ( P0.001, η (2): 0.13-0.40). MD covered the greater TD; CB the lowest ( P0.05). Distance for VHIA was lower for CB compared with all other positions ( P0.05); W and S displayed the highest VHIA ( P0.05). Relationships between match running performance and physical capacities were position-dependent, with poor or non-significant correlations within FB, CB, MD and W (e. g., VHIA vs. VVam-eval: R=0.06 in FB) but large associations within 2 (nd)S and S positions (e. g., VHIA vs. VVam-eval: R=0.70 in 2 (nd)S). In highly trained young soccer players, the importance of fitness level as a determinant of match running performance should be regarded as a function of playing position.

Made available in DSpace on 2016-10-10T03:51:15Z (GMT). No. of bitstreams: 5 Perceived exertion threshold_comparison with ventilatory thresholds and critical power.pdf: 297274 bytes, checksum: 29d81da39f3f03a866e800205f577a70 (MD5) license_url: 52 bytes, checksum: 3d480ae6c91e310daba2020f8787d6f9 (MD5) license_text: 21716 bytes, checksum: c200d7a52028dd255d79d7c917cc149a (MD5) license_rdf: 23005 bytes, checksum: 845fd6e03839c7264c0c164178b2e173 (MD5) license.txt: 1818 bytes, checksum: 46de3043f08e87659ae535ef74b8ce9d (MD5) Previous issue date: 2009 Objective. – The aim of this study was to provide concurrent validity evidences to perceived exertion threshold (PET) by comparing and establishing relationships with aerobic fitness parameters derived from square-wave and incremental tests. Methods. – Eleven male college students performed one incremental test to determine first and second ventilatory thresholds (VT1 and VT2, respectively), maximal oxygen uptake ( VO2max ), and maximal aerobic power (MAP); four predictive trials for the critical power (CP) and PET estimations. Results. – Oxygen consumption ( VO2) at VT1 and VT2 were 22.9±4.2 and 35.8±4.7 ml/kg per minute, respectively. The MAP and VO2max were 267±34W and 40.3±6.3 ml/kg per minute, respectively. The PET (146±31 W) and CP (146±33 W) did not differ from each other, and both estimates were between VT1 (121±28 W) and VT2 (228±36 W). The correlations between PET and CP, expressed in relative terms to body mass, were significant (P

International audience; Background: The diving response includes cardiovascular adjustments known to decrease oxygen uptake and thus prolong apnea duration. As this diving response is in part characterized by a pronounced decrease in heart rate (HR), it is thought to be vagally mediated.Methods: In five professional breath-hold divers (BHDs) and fi ve less-trained controls (CTL), we investigated whether the diving response is in fact associated with an increase in the root mean square successive difference of the R-R intervals (RMSSD), a time-domain heart rate variability (HRV) index. HR behavior and arterial oxygen saturation (S a O 2) were continuously recorded during one maximal apnea. Short-term changes in S a O 2 , HR, and RMSSD were calculated over the complete apnea duration.Results: BHDs presented bi-phasic HR kinetics, with two HR decreases (32 6 17% and 20 6 10% of initial HR). The second HR decrease, which was concomitant to the pronounced S a O 2 decrease, was also simultaneous to a marked increase in RMSSD. CTL showed only one HR decrease (50 6 10% of initial HR), which appeared before the concomitant S a O 2 and RMSSD changes. When all subject data were combined, arterial desaturation was positively correlated with total apnea time (r 5 0.87, P , 0.01).Conclusion: This study indicates that barorefl ex stimulation and hypoxia may be involved in the bi-phasic HR response of BHDs and thus in their longer apnea duration.

Heart rate variability (HRV), which is considered to reflect the activity of the autonomic nervous system (ANS), has been shown to decline with age. The aim of the present study was to explore cardiac ANS in older patients showing frontal-subcortical dysfunction with "Psychomotor Disadaptation Syndrome" (PDS), through the 24-h HRV. We enrolled 14 patients with PDS (mean age: 84.5+/-6.9 years), they were compared to 13 frail control subjects (mean age: 80.6+/-6.7 years). Cardiac ANS activity was assessed by 24-h ECG recordings from three leads with a Holter digital monitor. The decrease in cardiac ANS activity observed in PDS subjects was greater than the alteration found in normally aging subjects. The abnormalities of ANS that aggravate the effects of aging can be seen as a type of physical deconditioning. Such patients could benefit from particular attention in physical training.

Traditionally, the core of a Terminological Knowledge Representation System (TKRS) consists of a TBox or terminology, where concepts are introduced, and an ABox or world description, where facts about individuals are stated in terms of concept memberships. This design has a drawback because in most applications the TBox has to meet two functions at a time: On the one hand—similarly to a database schema—frame-like structures with type information are introduced through primitive concepts and primitive roles; on the other hand, views on the objects in the knowledge base are provided through defined concepts. We propose to account for this conceptual separation by partitioning the TBox into two components for primitive and defined concepts, which we call the schema and the view part. We envision the two parts to differ with respect to the language for concepts, the statements allowed, and the semantics. We argue that this separation achieves more conceptual clarity about the role of primitive and defined concepts and the semantics of terminological cycles. Two case studies show the computational benefits to be gained from the refined architecture.