Date of Submission



Rugby league is a collision sport that is intermittent in nature, characterised by bouts of high intensity running, collisions and tackling, separated by periods of lower intensity activity. Success in the sport requires a multifaceted skillset with players requiring good ball handling ability, quick and accurate decision making, and the ability to perform effective tackles.

A large part of success in a collision sport such as rugby league is based on player’s ability to execute proficient and effective tackles, the ability to dominate the tackle contest, and the capacity to tolerate physical impacts. While the tackle contest is a critical element in rugby league, there is a relatively small body of work investigating this facet of the sport.

It is generally accepted that high levels of muscular strength and power is advantageous for elite rugby league performance as players are required to push, pull, wrestle and tackle their opposition. However, the extent to which strength and power influences specific rugby league skills, such as tackling, is not fully understood.

The aim of this thesis was to examine the influence of muscular strength and power on tackle ability and tackle performance in semi-professional rugby league players. This was achieved through seven experimental studies. The first study examined the muscular strength and power correlates of a standardised one-on-one under-the-ball tackle drill. The second study investigated the influence that changes in muscular strength and power following an 8-week training block had on the aforementioned tackle drill. The third study explored changes in tackle ability during a competitive season and possible relationships with changes in muscular strength and power. Study four examined the relationship between the standardised one-on-one tackle assessment and match-play tackle performance. Based on the findings of the previous chapter, study five explored the relationships between match-play tackle characteristics, tackle outcomes and physical qualities. The final two studies examined an alternate tackle drill, the over-the-ball tackle drill, and its relationship to strength and power, as well as match-play tackle performance.

It was found that well-developed muscular strength and upper-body power were significantly correlated to tackling ability in rugby league players. Lower body strength as measured by a 1RM squat, maximum squat relative to body mass, and upper body power (plyometric push up) were related to performance in the standardised one-on-one under-the-ball tackle drill. It was also found that over an 8 week period, increases in lower-body strength was related to enhanced tackle ability. Conversely, there was a clear relationship between players who experienced a decrement in lower-body strength and deterioration in tackling ability.

The standardised one-on-one under-the-ball tackle drill was shown to be a reliable (intraclass correlation coefficient for test-retest reliability = 0.88) and valid method to evaluate tackling ability in semi-professional rugby league players. Players with good tackling ability were involved in a greater proportion of dominant tackles and missed fewer tackles during match-play. Lower-body muscular strength was found to be correlated to the proportion of dominant tackles made during match-play. Furthermore, lower-body strength was significantly related to defenders exhibiting a medium body position (tackler presenting moderate flexion at hips and knees) and the ball-carrier being placed on their back. These findings suggest that lower-body strength was related to tackle characteristics and outcomes.

An examination of match-play tackle characteristics found that approximately 70% of tackles were executed around the ball-carriers chest and shoulders and less than 25% of tackles were made at the mid-torso region. Thus, an alternate one-on-one tackle drill was examined where contact was made on the upper-torso of the ball carrier, the over-the-ball tackle. It was observed that upper-body strength and power as measured by plyometric push up peak power was significantly related to over-the-ball tackling ability. Under-the-ball and over-the-ball tackle abilities were shown to be associated with varying indicators of match-play tackle performance. Under-the-ball tackle ability was positively related to the proportion of dominant tackles and negatively related to missed tackles, while over-the-ball tackle ability was positively related to the proportion of dominant tackles and average play-the-ball speeds, and negatively related to tackles that conceded offloads.

Two important findings can be concluded from the studies presented in this thesis. The first is that muscular strength, in particular lower body strength, contributes to under-the-ball tackling ability and match-play tackle outcomes in rugby league players. As long as the technical aspects of tackling technique are adequately coached and practiced, then enhancements in muscular strength and power may be one of the foundational components to underpin improvement in tackling ability.

Secondly, this thesis presented criteria to assess over-the-ball tackling ability, with findings suggesting that the assessment is both valid and reliable. Both the under-the-ball and over-the-ball standardised tackle assessment tests are related to match-play tackle performance indicators, thus justifying the practical utility of these off-field tests to assess tackling ability. Although correlated, this study showed that the two tackle ability tests were related to different match-play tackle outcomes, indicating that over-the-ball and under-the-ball tackle ability are two different skills and should be assessed and trained accordingly.


School of Exercise Science

Document Type


Access Rights

Open Access


252 pages

Degree Name

Doctor of Philosophy (PhD)


Faculty of Health Sciences