To determine and compare the force exerted upon the head and relative position of the cervical spine during the sustained push phase of scrummaging across the front row (FR), under both machine and live conditions.
Twelve male front row rugby union players (20.7 ± 1.3 years,1.78 ± 0.06 m, 98.3 ± 12.6 kg) of university or community level standard were tested. Scrummaging was performed under two conditions:
- Scrum Machine (SM). Participants scrummaged against instrumented scrum machine affixed with a bespoke head pad.
- Live Scrum (LS). Scrummaging was performed in a 3-vs-3 FR formation. Participants were fitted with TekScan pressure sensors affixed to a head guard to record estimated force and their point of application.
Neck and head angles were recorded using inertial measurement units (Xsens, MTw) across both conditions. All trials were recorded using a ‘Crouch-Bind-Set’ call sequence.
SM generated a significantly larger neck flexion angle compared with LS. Forces exerted upon the head and the relative position of the cervical spine were comparable across conditions (Fig 2). Across the FR positions, force acting upon the head was found to be statistically significant under LS conditions. Substantially larger forces were exerting upon the the tighthead (TH) and hooker (HK), compared with the loosehead (LH).
Machine scrummaging lacks ecological validity in terms of FR scrum biomechanics (e.g. head position and head forces across FR), and raises questions as to their place in coaching correct scrummaging technique. Furthermore the inter-positional differences in force during live scrummaging indicate for the first time how the potential injury risk (both acute and chronic) may vary across these positions.