A new approach to quantifying physical demand in rugby union

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Abstract

The objective of the study was to describe an original approach to assessing individual workload during international rugby union competitions. The difference between positional groups and between the two halves was explored. Sixty-seven files from 30 French international rugby union players were assessed on a computerised player-tracking system (Amisco Pro(®), Sport Universal Process, Nice, France) during five international games. Each player's action was split up into exercise and recovery periods according to his individual velocity threshold. Exercise-to-recovery (E:R) period ratios and acceleration were calculated. Results indicated that about 65% of exercise periods lasted less than 4 s; half of the E:Rs were less than 1:4, and about one-third ranged between 1 and 1:4 and about 40% of exercise periods were classified as medium intensity. Most acceleration values were less than 3 m·s(-2) and started from standing or walking activity. Back row players showed the highest mean acceleration values over the game (P < 0.05). No significant decrease in physical performance was seen between the first and second halves of the games except for back rows, who showed a significant decrease in mean acceleration (P < 0.05). The analysis of results emphasised the specific activity of back rows and tended to suggest that the players' combinations of action and recovery times were optimal for preventing large decrease in the physical performance.

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Energy cost and metabolic power in elite soccer: a new match analysis approach.

Cristian Osgnach, Stefano Poser, Riccardo Bernardini … (2010)

Video match analysis is used for the assessment of physical performances of professional soccer players, particularly for the identification of "high intensities" considered as "high running speeds." However, accelerations are also essential elements setting metabolic loads, even when speed is low. We propose a more detailed assessment of soccer players' metabolic demands by video match analysis with the aim of also taking into account accelerations. A recent study showed that accelerated running on a flat terrain is equivalent to running uphill at constant speed, the incline being dictated by the acceleration. Because the energy cost of running uphill is known, this makes it possible to estimate the instantaneous energy cost of accelerated running, the corresponding instantaneous metabolic power, and the overall energy expenditure, provided that the speed (and acceleration) is known. Furthermore, the introduction of individual parameters makes it possible to customize performance profiles, especially as it concerns energy expenditure derived from anaerobic sources. Data from 399 "Serie-A" players (mean +/- SD; age = 27 +/- 4 yr, mass = 75.8 +/- 5.0 kg, stature = 1.80 +/- 0.06 m) were collected during the 2007-2008 season. Mean match distance was 10,950 +/- 1044 m, and average energy expenditure was 61.12 +/- 6.57 kJ x kg(-1). Total distance covered at high power (>20 W x kg(-1)) amounted to 26% and corresponding energy expenditure to approximately 42% of the total. "High intensities" expressed as high-power output are two to three times larger than those based only on running speed. The present approach for the assessment of top-level soccer players match performance through video analysis allowed us to assess instantaneous metabolic power, thus redefining the concept of "high intensity" on the basis of actual metabolic power rather than on speed alone.

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Sprint running: a new energetic approach.

G Antonutto, G. Di Giovanni, L Sepulcri … (2005)

The speed of the initial 30 m of an all-out run from a stationary start on a flat track was determined for 12 medium level male sprinters by means of a radar device. The peak speed of 9.46+/-0.19 m s(-1) (mean +/- s.d.) was attained after about 5 s, the highest forward acceleration (a(f)), attained immediately after the start, amounting to 6.42+/-0.61 m s(-2). During acceleration, the runner's body (assumed to coincide with the segment joining the centre of mass and the point of contact foot terrain) must lean forward, as compared to constant speed running, by an angle alpha = arctang/a(f) (g = acceleration of gravity). The complement (90-alpha) is the angle, with respect to the horizontal, by which the terrain should be tilted upwards to bring the runner's body to a position identical to that of constant speed running. Therefore, accelerated running is similar to running at constant speed up an ;equivalent slope' ES = tan(90-alpha). Maximum ES was 0.643+/-0.059. Knowledge of ES allowed us to estimate the energy cost of sprint running (C(sr), J kg(-1) m(-1)) from literature data on the energy cost measured during uphill running at constant speed. Peak Csr was 43.8+/-10.4 J kg(-1) m(-1); its average over the acceleration phase (30 m) was 10.7+/-0.59 J kg(-1) m(-1), as compared with 3.8 for running at constant speed on flat terrain. The corresponding metabolic powers (in W kg(-1)) amounted to 91.9+/-20.5 (peak) and 61.0+/-4.7 (mean).

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Applied Physiology and Game Analysis of Rugby Union

Grant Duthie, Sue Hooper, David Pyne (2003)

Increased professionalism in rugby has elicited rapid changes in the fitness profile of elite players. Recent research, focusing on the physiological and anthropometrical characteristics of rugby players, and the demands of competition are reviewed. The paucity of research on contemporary elite rugby players is highlighted, along with the need for standardised testing protocols. Recent data reinforce the pronounced differences in the anthropometric and physical characteristics of the forwards and backs. Forwards are typically heavier, taller, and have a greater proportion of body fat than backs. These characteristics are changing, with forwards developing greater total mass and higher muscularity. The forwards demonstrate superior absolute aerobic and anaerobic power, and muscular strength. Results favour the backs when body mass is taken into account. The scaling of results to body mass can be problematic and future investigations should present results using power function ratios. Recommended tests for elite players include body mass and skinfolds, vertical jump, speed, and the multi-stage shuttle run. Repeat sprint testing is a possible avenue for more specific evaluation of players. During competition, high-intensity efforts are often followed by periods of incomplete recovery. The total work over the duration of a game is lower in the backs compared with the forwards; forwards spend greater time in physical contact with the opposition while the backs spend more time in free running, allowing them to cover greater distances. The intense efforts undertaken by rugby players place considerable stress on anaerobic energy sources, while the aerobic system provides energy during repeated efforts and for recovery. Training should focus on repeated brief high-intensity efforts with short rest intervals to condition players to the demands of the game. Training for the forwards should emphasise the higher work rates of the game, while extended rest periods can be provided to the backs. Players should not only be prepared for the demands of competition, but also the stress of travel and extreme environmental conditions. The greater professionalism of rugby union has increased scientific research in the sport; however, there is scope for significant refinement of investigations on the physiological demands of the game, and sports-specific testing procedures.