Opposition Skill Efficiency During Professional Rugby Union Official Games Is Related to Horizontal Force-Production Capacities in Sprinting.

Purpose: This study aimed to determine relationships between parameters of force-production capacity in sprinting and opposition skill efficiency in rugby union games according to position. Methods: The sprint force–velocity profile of 33 professional rugby union players divided into 2 subgroups (forwards and backs) was measured on a 30-m sprint. Skill efficiencies (in percentage) of offensive duels, tackles, and rucks were assessed using objective criteria during 12 consecutive competitive games. Pearson correlation was used to determine the relationships between parameters of horizontal force-production capacity in sprinting (maximum propulsive power, theoretical maximum force [F₀], theoretical maximum velocity, maximum ratio of horizontal force [RF_max], and rate of decrease of this ratio of forces with increasing velocity) and skill efficiencies. Two multiple linear regression models were used to observe whether skill efficiencies could depend on determinants of horizontal force application in low- or high-velocity conditions. A first model including F₀ and theoretical maximum velocity was used as a macroscopic analysis, while a second model including RF_max and rate of decrease of this ratio of forces with increasing velocity was used as microscopic analysis to determine the most significant determinants of skill efficiency. Results: All skill efficiencies were strongly correlated with maximum propulsive power in forwards and backs. In forwards, F₀ and RF_max were the key predictors of dueling, rucking, and tackling efficiency. In backs, F₀ was the main predictor of dueling and rucking efficiency, whereas RF_max was the key predictor of dueling and tackling efficiency. F₀ and theoretical maximum velocity equivalently contributed to tackling performance. Conclusions: In rugby union forward and back players, skill efficiency is correlated with maximum propulsive power and may be more explained by horizontal force-production capacity and mechanical effectiveness at lower velocities than at higher velocities. [ABSTRACT FROM AUTHOR]