Are there differences in elite youth soccer player work rate profiles in congested versus regular match schedules?

Official international tournaments in which youth soccer players participate can involve very congested schedules. Yet no information regarding physical and technical match performance during congested versus regular (non-congested) cycles is available. In this study, accelerations, decelerations, mean metabolic power, and technical performance (offensive and defensive variables) were compared across very congested (VCM; 10 international matches played over 3 successive days, including 2 days with 2 consecutive matches separated by a 4-5 hr interval) and 10 regular (non-congested) match periods (NCM) in elite male Under 15 (U15, n=11) and Under 17 (U17, n=13) soccer players. Players wore a 15-Hz GPS unit with a 100-Hz tri-axial accelerometer. The session-RPE was assessed 30 min post-match. Results showed a higher number of accelerations/min observed in VCM vs NCM (U15; 2.27±0.35 vs 2.12±0.23; effect size [ES]=0.49; U17; 2.27±0.41 vs 2.01±0.31; ES=0.69). Decelerations/min were higher during VCM (U15; 1.99±0.27 vs 1.84±0.25; ES=0.55; and U17; 1.98±0.35 vs 1.80±0.27; ES=0.56). Mean metabolic power was higher in the VCM (U15; 0.42±0.06 vs 0.37±0.02; ES=1.08; U17; 0.46±0.03 vs 0.30±0.03; ES=1.94). Technical actions/min were higher in the VCM for U17 (ES=1.60 and 1.37, for offensive and defensive performance, respectively); but lower (during VCM) for U15 (ES=3.59 and 0.28, for offensive and defensive performance). U15 reported a higher session-RPE in the VCM (7.9±0.5 AU vs 6.9±0.5 AU). The findings suggest that running activity in these youth players was unaffected overall in tournaments with congested schedules and that the intensity of match-play was actually greater than in regular match schedules

The Duration-specific Peak Average Running Speeds of European Super League Academy Rugby League Match Play.

This study aimed to quantify the duration-specific peak average running speeds of Academy-level rugby league match play, and compare between playing positions. Global positioning system data were collected from 149 players competing across 9 teams during 21 professional Academy (under-19) matches. Players were split into 6 positions: hookers (n = 40), fullbacks (n = 24), halves (n = 47), outside backs (n = 104), middles (n = 118), and backrow forwards (n = 104). Data were extracted and the 10-Hz raw velocity files exported to determine the peak average running speeds, via moving averages of speed (m·min−1), for 10- and 30-second, and 1- to 5- and 10-minute durations. The data were log transformed and analyzed using linear mixed-effect models followed by magnitude-based inferences, to determine differences between positions. Differences in the peak average running speeds are present between positions, indicating the need for position-specific prescription of velocity-based training. Fullbacks perform possibly to most likely greater average running speeds than all other positions, at each duration, except at 10 seconds vs. outside backs. Other differences are duration dependent. For 10 seconds, the average running speed is most likely greater for outside backs vs. the hookers, middles, and backrow forwards, but likely to most likely lower for 10 minutes. Hookers have possibly trivial or lower average speed for 10 seconds vs. middles and backrow forwards, but very likely greater average running speed for 10 minutes. The identified peak average running speeds of Academy-level match play seem similar to previously reported values of senior professional level

Comprehensive comparison and experimental validation of band-structure calculation methods in III\u2013V semiconductor quantum wells

We present and thoroughly compare band-structures computed with density functional theory, tight-binding, k p and non-parabolic effective mass models. Parameter sets for the non-parabolic C, the L and X valleys and intervalley bandgaps are extracted for bulk InAs, GaAs and InGaAs. We then consider quantum-wells with thickness ranging from 3 nm to 10 nm and the bandgap dependence on film thickness is compared with experiments for In0:53Ga0:47As quantum-wells. The impact of the band-structure on the drain current of nanoscale MOSFETs is simulated with ballistic transport models, the results provide a rigorous assessment of III\u2013V semiconductor band structure calculation methods and calibrated band parameters for device simulations

Quantifying The External And Internal Loads Of Professional Rugby League Training Modes: Consideration For Concurrent Field-Based Training Prescription.

Practitioners prescribe numerous training modes to develop the varied physical qualities professional rugby league players must express during competition. The aim of the current study was to determine how the magnitude of external and internal training load per minute of time differs between modes in professional rugby league players. This data were collected from 17 players across 716 individual sessions (mean (SD) sessions: 42 (13) per player) which were categorised by mode (conditioning, small sided games, skills and sprint training). Derived from global positioning systems (5Hz with 15Hz interpolation), the distances covered within arbitrary speed- and metabolic-power-thresholds were determined to represent the external load. Session rating of perceived exertion (sRPE) and individualised training impulse (iTRIMP) represented the internal load. All data were made relative to session duration. The differences in time-relative load methods between each mode were assessed using magnitude based inferences. Small-sided-games and conditioning very likely to almost certainly produced the greatest relative internal and external loads. Sprint training provided players with the greatest sprinting and maximal-power distances without a concomitant increase in internal load. The metabolic-power method complements speed-based quantification of the external load, particularly during smallsided-games and skills training. In practice, establishing normative loads per minute of time for each mode can be useful to plan future training by multiplying this value by the planned session duration

Exposure time, running and skill-related performance in international u20 rugby union players during an intensified tournament

Purpose This study investigated exposure time, running and skill-related performance in two international u20 rugby union teams during an intensified tournament: the 2015 Junior World Rugby Championship. Method Both teams played 5 matches in 19 days. Analyses were conducted using global positioning system (GPS) tracking (Viper 2™, Statsports Technologies Ltd) and event coding (Opta Pro®). Results Of the 62 players monitored, 36 (57.1%) participated in 4 matches and 23 (36.5%) in all 5 matches while player availability for selection was 88%. Analyses of team running output (all players completing >60-min play) showed that the total and peak 5-minute high metabolic load distances covered were likely-to-very likely moderately higher in the final match compared to matches 1 and 2 in back and forward players. In individual players with the highest match-play exposure (participation in >75% of total competition playing time and >75-min in each of the final 3 matches), comparisons of performance in matches 4 and 5 versus match 3 (three most important matches) reported moderate-to-large decreases in total and high metabolic load distance in backs while similar magnitude reductions occurred in high-speed distance in forwards. In contrast, skill-related performance was unchanged, albeit with trivial and unclear changes, while there were no alterations in either total or high-speed running distance covered at the end of matches. Conclusions These findings suggest that despite high availability for selection, players were not over-exposed to match-play during an intensified u20 international tournament. They also imply that the teams coped with the running and skill-related demands. Similarly, individual players with the highest exposure to match-play were also able to maintain skill-related performance and end-match running output (despite an overall reduction in the latter). These results support the need for player rotation and monitoring of performance, recovery and intervention strategies during intensified tournaments

The application of differential ratings of perceived exertion to Australian Football League matches

Objectives: To investigate the application of differential ratings of perceived exertion for the examination of internal load during Australian Football League (AFL) matches. Design: Single cohort, observational study. Methods: Using the centiMax rating of perceived exertion (RPE) scale, 26 professional AFL players provided ratings for match exertion (RPE-M), along with differential ratings for breathlessness (RPE-B), leg exertion (RPE-L), and technical demand (RPE-T) following 129 matches (5.0 ± 1.6 matches per player). Global positioning satellite (GPS) and accelerometer measures were also collected. Data were analysed using magnitude-based inferences. Results: RPE scores were 93.0 ± 8.2 AU (RPE-M), 89.0 ± 11.0 AU (RPE-B), 91.5 ± 9.8 AU (RPE-L), and 87.0 ± 10.0 AU (RPE-T). There was a most likely small difference between RPE-L and RPE-T (5.5%; ±90% confidence limits 1.9%), a likely small difference between RPE-L and RPE-B (3.5%; ±1.5%) and a possibly small difference between RPE-B and RPE-T (1.9%; ±1.9%). Within-player correlations between RPE and GPS measures were small for RPE-M (r = 0.14–0.28), unclear to small for RPE-B (r = 0.06–0.24) and unclear to moderate for RPE-L (r = 0.06–0.37). Differential RPE's combined to explain 76% of the variance in RPE-M. For all RPE scores, within-player variability was moderate to high (typical error: 7.9–12.4%), and the thresholds for a likely between-match change were 8.8–13.7%. Conclusions: As differential RPE's represent distinct sensory inputs, the collection of these scores facilitate the interpretation of internal match loads and therefore represent a valuable addition to match data collection procedures. Moderate to high within-player variability should be considered when interpreting between-match changes in all RPE scores

Physiological Responses to Linear and Nonlinear Soccer-specific Match Simulations and Their Effects on Lower-Limb Muscle Fatigue

The aims of this study were to: (a) investigate the effects of linear and nonlinear soccer simulations on lower-limb muscle function and physiological responses and (b) evaluate the relationship between match-running demands and changes in lower-limb muscle function. In a repeated-measures cross-over design, 8 participants completed either a linear or nonlinear adapted Loughborough Intermittent Shuttle Test (LIST) on 2 occasions. The movement of players was tracked with a global positioning system, while lower-limb muscle function tests and physiological measurements were performed before and every 15 minutes during the simulation. There were no differences in distance covered, yet high-speed running (p = 0.007), accelerations (p = 0.008), and decelerations (p = 0.015) were higher in the linear LIST. Mean heart rate (p = 0.001) and ratings of perceived exertion (p = 0.013) were higher in the nonlinear LIST. Peak landing forces (p = 0.017) and jump height (p = 0.001) were reduced between baseline and 90 minutes but were not different between conditions. Changes in peak landing forces from baseline to half-time (r = -0.57, n = 16, p = 0.022) and full-time (r = -0.58, n = 16, p = 0.019) were related to high-speed running. Hamstring force was unaffected by time (p = 0.448) but was reduced in the linear LIST (p = 0.044). Protocols posing different external and internal demands elicited similar levels of fatigue across simulations. Hamstring function was not an effective indicator of fatigue, but our results highlight the greater demands placed on this muscle group when higher-speed running is performed

Metabolic power in hurling with respect to position and halves of match-play.

The current investigation compared the metabolic power and energetic characteristics in team sports with respect to positional lines and halves of match-play. Global positioning system (GPS) technology data were collected from 22 elite competitive hurling matches over a 3-season period. A total of 250 complete match-files were recorded with players split into positional groups of full-back; half-back; midfield; half-forward; full-forward. Raw GPS data were exported into a customized spreadsheet that provided estimations of metabolic power and speed variables across match-play events (average metabolic power [Pmet], high metabolic load distance [HMLD], total distance, relative distance, high-speed distance, maximal speed, accelerations, and deceleration). Pmet, HMLD, total, relative and high-speed distance were 8.9 ± 1.6 W·kg-1, 1457 ± 349 m, 7506 ± 1364 m, 107 ± 20 m·min-1 and 1169 ± 260 m respectively. Half-backs, midfielders and half-forwards outperformed full-backs (Effect Size [ES] = 1.03, 1.22 and 2.07 respectively), and full-forwards in Pmet (Effect Size [ES] = 1.70, 2.07 and 1.28 respectively), and HMLD (full-backs: ES = -1.23, -1.37 and -0.84 respectively, and full-forwards: ES = -1.77, -2.00 and -1.38 respectively). Half-backs (ES = -0.60), midfielders (ES = -0.81), and half-forwards (ES = -0.74) experienced a second-half temporal decrement in HMLD. The current investigation demonstrates that metabolic power may increase our understanding of the match-play demands placed on elite hurling players. Coaches may utilize these findings to construct training drills that replicate match-play demands

Are Current Physical Match Performance Metrics in Elite Soccer Fit for Purpose or is the Adoption of an Integrated Approach Needed?

Time-motion analysis is a valuable data-collection technique used to quantify the physical match performance of elite soccer players. For over 40 years researchers have adopted a 'traditional' approach when evaluating match demands by simply reporting the distance covered or time spent along a motion continuum of walking through to sprinting. This methodology quantifies physical metrics in isolation without integrating other factors and this ultimately leads to a one-dimensional insight into match performance. Thus, this commentary proposes a novel 'integrated' approach that focuses on a sensitive physical metric such as high-intensity running but contextualizes this in relation to key tactical activities for each position and collectively for the team. In the example presented, the 'integrated' model clearly unveils the unique high-intensity profile that exists due to distinct tactical roles, rather than one-dimensional 'blind' distances produced by 'traditional' models. Intuitively this innovative concept may aid the coaches understanding of the physical performance in relation to the tactical roles and instructions given to the players. Additionally, it will enable practitioners to more effectively translate match metrics into training and testing protocols. This innovative model may well aid advances in other team sports that incorporate similar intermittent movements with tactical purpose. Evidence of the merits and application of this new concept are needed before the scientific community accepts this model as it may well add complexity to an area that conceivably needs simplicity