The emergence of critical incidents in Rugby Union matches using Markov chain analysis.

During a rugby match, teams are continually trying to cause instabilities of different magnitudes on each other. Once a perturbation occurs, a phase transition emerges. Markov chain analysis has the potential to investigate emerging patterns in rugby union. This study examined the probability of a critical incident (CI; penalties and tries) occurring during Rugby Union matches, and whether differences would exist between winning and losing. The Markov chain analysis was used to identify the probability of a transition from a game state to a further state, due to the analysis of the preceding state. A game phase was defined as a technical and tactical match action which occurred between two consecutive advantage lines. Contingency tables were assembled from 280 phases registered during 11 matches of Brazilian Rugby Union XV A Series Championship. The results showed that previous technical and tactical actions made from rucks had the highest probability of generating a transition phase leading to a CI. The results suggest that the winning teams adopt a more flexible approach to the environmental changes that occur throughout a game and demonstrated more flexibility during transitional state occurrences, with higher variability in technical and tactical actions related to a previous game phase.

The Markov chain analysis showed that previous technical and tactical actions made from rucks had the highest probability of generating a transition phase leading to a CI.Winning teams may adopt a more flexible approach to the environmental changes that occur throughout a game.Higher variability in technical and tactical actions related to a previous game phase was observed in winning teams.The game action leading to CI moments for winning teams involved forwards and backs, while losing teams mainly depended on the involvement of forwards and eventually on opponent errors.Markov chain analysis may be a useful and valid tool to rugby match-play analysis considering the complex system framework.

Assessment of Energy Expenditure of a Professional Goalkeeper From the English Premier League Using the Doubly Labeled Water Method.

Purpose: To better understand the energy and carbohydrate (CHO) requirements of a professional goalkeeper (GK) in elite soccer, the authors quantified physical loading, energy expenditure (EE), and energy intake (EI) during a 2-games-per-week in-season microcycle. Methods: Daily training and match loads were assessed in a professional GK (age 26 y, height 191 cm, body mass 85.6 kg) from the English Premier League using global positioning systems (GPS) and ProZone®, respectively. Assessments of EE (using the doubly labeled water method) and EI (using food diaries supported by the remote food photographic method and 24-h recalls) were also completed. Results: Physical loading was greater on match days than training days as inferred from total distance (4574 [432] vs 1959 [500] m), average speed (48 [5] vs 40 [4] m/min), and distance completed when jogging (993 [194] vs 645 [81] m) and running (138 [16] vs 21 [20] m). Average daily energy and macronutrient intake appear reflective of a self-selected "low-CHO" diet (energy 3160 [381] kcal, CHO 2.6 [0.6], protein 2.4 [0.4], fat 1.9 [0.3] g/kg body mass). Mean daily EE was 2894 kcal. Conclusions: The average daily EE of this professional GK was approximately 600 kcal/d lower than that previously reported in outfield players from the same team. Such data suggest that the nutritional requirements of a GK should be carefully considered depending on the required daily and weekly loading patterns.

Unilateral jumps in different directions: a novel assessment of soccer-associated power?

OBJECTIVES: We aimed to determine whether countermovement jumps (CMJs; unilateral and bilateral) performed in different directions assessed independent lower-limb power qualities, and if unilateral CMJs would better differentiate between elite and non-elite soccer players than the bilateral vertical (BV) CMJ. DESIGN: Elite (n=23; age, 18.1±1.0years) and non-elite (n=20; age, 22.3±2.7years) soccer players performed three BV, unilateral vertical (UV), unilateral horizontal-forward (UH) and unilateral medial (UM) CMJs. METHODS: Jump performance (height and projectile range), kinetic and kinematic variables from ground reaction forces, and peak activation levels of the vastus lateralis and biceps femoris (BF) muscles from surface electromyography, were compared between jumps and groups of players. RESULTS: Peak vertical power (V-power) was greater in BV (220.2±30.1W/kg) compared to UV (144.1±16.2W/kg), which was greater than UH (86.7±18.3W/kg) and UM (85.5±13.5W/kg) (all, p<0.05) but there was no difference between UH and UM (p=1.000). Peak BF EMG was greater in UH compared to all other CMJs (p≤0.001). V-power was greater in elite than non-elite for all CMJs (p≤0.032) except for BV (p=0.197). Elite achieved greater UH projectile range than non-elite (51.6±15.4 vs. 40.4±10.4cm, p=0.009). CONCLUSIONS: We have shown that UH, UV and UM CMJs assess distinct lower-limb muscular power capabilities in soccer players. Furthermore, as elite players outperformed non-elite players during unilateral but not BV CMJs, unilateral CMJs in different directions should be included in soccer-specific muscular power assessment and talent identification protocols, rather than the BV CMJ.

Energy Intake and Expenditure of Professional Soccer Players of the English Premier League: Evidence of Carbohydrate Periodization.

In an attempt to better identify and inform the energy requirements of elite soccer players, we quantified the energy expenditure (EE) of players from the English Premier League (n = 6) via the doubly labeled water method (DLW) over a 7-day in-season period. Energy intake (EI) was also assessed using food diaries, supported by the remote food photographic method and 24 hr recalls. The 7-day period consisted of 5 training days (TD) and 2 match days (MD). Although mean daily EI (3186 ± 367 kcals) was not different from (p > .05) daily EE (3566 ± 585 kcals), EI was greater (p < .05) on MD (3789 ± 532 kcal; 61.1 ± 11.4 kcal.kg-1 LBM) compared with TD (2956 ± 374 kcal; 45.2 ± 9.3 kcal.kg-1 LBM, respectively). Differences in EI were reflective of greater (p < .05) daily CHO intake on MD (6.4 ± 2.2 g.kg-1) compared with TD (4.2 ± 1.4 g.kg-1). Exogenous CHO intake was also different (p < .01) during training sessions (3.1 ± 4.4 g.h-1) versus matches (32.3 ± 21.9 g.h-1). In contrast, daily protein (205 ± 30 g.kg-1, p = .29) and fat intake (101 ± 20 g, p = .16) did not display any evidence of daily periodization as opposed to g.kg-1, Although players readily achieve current guidelines for daily protein and fat intake, data suggest that CHO intake on the day before and in recovery from match play was not in accordance with guidelines to promote muscle glycogen storage.

Body composition assessment of English Premier League soccer players: a comparative DXA analysis of first team, U21 and U18 squads.

Professional soccer players from the first team (1st team, n = 27), under twenty-one (U21, n = 21) and under eighteen (U18, n = 35) squads of an English Premier League soccer team were assessed for whole body and regional estimates of body composition using dual-energy X-ray absorptiometry (DXA). Per cent body fat was lower in 1st team (10.0 ± 1.6) compared with both U21 (11.6 ± 2.5, P = 0.02) and U18 (11.4 ± 2.6, P = 0.01) players. However, this difference was not due to variations (P = 0.23) in fat mass between squads (7.8 ± 1.6 v. 8.8 ± 2.1 v. 8.2 ± 2.4 kg, respectively) but rather the presence of more lean mass in 1st team (66.9 ± 7.1 kg, P < 0.01) and U21 (64.6 ± 6.5 kg, P = 0.02) compared with U18 (60.6 ± 6.3 kg) players. Accordingly, fat mass index was not different (P = 0.138) between squads, whereas lean mass index was greater (P < 0.01) in 1st team players (20.0 ± 1.1 kg · m(-2)) compared with U18 players (18.8 ± 1.4 kg · m(-2)). Differences in lean mass were also reflective of higher lean tissue mass in all regions, for example, upper limbs/lower limbs and trunk. Data suggest that training and nutritional interventions for younger players should therefore be targeted to lean mass growth as opposed to body fat loss.