Countermovement Jump Standards in Rugby League: What is a "Good" Performance?

Area of Science:

• Sports Science
• Biomechanics
• Rugby League Performance Analysis

Background:

• The countermovement jump (CMJ) is a key performance indicator in rugby league.
• Previous research lacks standardized reference values for CMJ metrics in rugby league players.
• Inconsistent assessment methods hinder the interpretation of 'good' CMJ performance.

Purpose of the Study:

• To establish norm-referenced values for countermovement jump (CMJ) performance in elite rugby league players.
• To create a reference scale for jump height (JH), reactive strength index modified (RSImod), mean propulsion power (PPmean), and peak propulsion power (PPpeak).
• To differentiate performance standards between 'forward' and 'back' positional groups.

Main Methods:

• One hundred four elite rugby league players (55 forwards, 49 backs) from top English leagues participated.
• Three countermovement jumps were performed on a force platform at the start of pre-season.
• Jump height (JH), reactive strength index modified (RSImod), mean propulsion power (PPmean), and peak propulsion power (PPpeak) were calculated using criterion methods.

Main Results:

• Backs demonstrated superior performance across all measured CMJ metrics compared to forwards.
• Position-specific percentile-based reference values were generated for JH, RSImod, PPmean, and PPpeak.
• Significant differences in CMJ metrics were observed within and between positional subgroups (quartiles).

Conclusions:

• The study provides the first position-specific reference scale for CMJ performance in elite rugby league.
• These norm-referenced values enable accurate assessment of player performance against established standards.
• The findings support the use of tailored performance benchmarks for forwards and backs in rugby league.