Background Approximately 25% of Rugby Union injuries occur to players executing a tackle and they mostly involve upper-body regions.

Objective To investigate how upper-body biomechanical loading changes depending on the tackle characteristics, such as side of body used and direction of approach.

Design A repeated-measures study where a group of Rugby Union players performed full tackling trials against a bespoke tackle simulator. Two conditions (both within-group factors) were analysed: laterality (left/right shoulder) and direction (front/diagonal/lateral) of the tackler's approach.

Setting A laboratory-based study.

Patients (or Participants) Six male players (26.7±7.6 years, 1.82±0.09 m, 95.7±14.0 kg), all right-side dominant.

Interventions (or Assessment of Risk Factors) Participants completed up to 2 dynamic tackles in each of the 6 testing conditions. A 40 kg punch-bag was accelerated manually to simulate the ball carrier and the tackler executed a full tackling movement bringing the punch-bag to the ground.

Main Outcome Measurements Peak shoulder impact forces and head linear accelerations were measured through pressure sensors and inertial measurement units. Linear mixed models and magnitude-based inferences were used to assess differences between conditions.

Results Dominant (right) shoulder tackles in the frontal direction generated the highest impact forces (5.3±1.0 kN), and overall they were substantially higher (by 15%) than non-dominant (left) shoulder tackles. Impact load decreased going from frontal to diagonal −3%) and lateral tackling (−10%). The lowest peak head accelerations (substantially lower [−5%] compared to frontal tackles) were recorded during diagonal tackles, with the right shoulder (9.1±3.5 g).

Conclusions Both laterality (dominant side) and tackle direction have a substantial effect on the loads applied to the upper-body. Where feasible, the tackler should approach from a slightly offset angle from frontal and coaching should aim to reduce the deficiencies in tackling technique on the non-dominant side.