Precision and Reliability of Self-Assessed Neck Strength in UK Youth Rugby Using a Novel Protocol and Fixation Device

Introduction: Neck strength has long been purported as an important concussion injury risk mitigator, particularly in high school sports, where players face frequent high-impact collisions. Monitoring neck strength in youth athletes is essential for both injury prevention and rehabilitation. However, in non-elite settings, the accessibility of equipment and trained personnel for reliable monitoring is often limited. Developing a simple, cost-effective solution to monitor neck strength would offer a significant advantage for grassroots and amateur sports environments.
Aim: The aims of this study were therefore to a) develop a practical and cost-effective method for neck strength testing, and b) assess the precision and test-retest reliability of a self-assessed isometric neck strength test protocol using a 3D-printed fixation device for a handheld dynamometer among youth rugby union players.
Methods: Twenty youth rugby union players (age range: 14-22, mean age: 16.2 ± 1.8 years, height: 1.72 ± 0.12 m, weight: 77.9 ± 17.6 kg) participated in the study. A custom-made 3D-printed device was used to mount the ActivForce2 handheld dynamometer to a rugby post for secure, examiner-free testing. The participants self-assessed their neck strength in flexion, extension, and lateral flexion (right and left) as part of their training on three separate occasions, twice on day one, and once on day two. Following a standardised short warm-up, each participant performed three maximal isometric contractions, with a 30-second rest between each repetition. Reliability was assessed within-day and between-days using Intraclass Correlation Coefficients (ICCs), while precision was evaluated using Standard Error of Measurement and Minimum Detectable Change.
Results: Within-day reliability was excellent across all movements: Peak Flexion showed an ICC of 0.982 (CI95% [0.96, 0.99]), Peak Extension had an ICC of 0.982 (CI95% [0.95, 0.99]), while Peak Right Lateral Flexion and Peak Left Lateral Flexion recorded ICCs of 0.953 (CI95% [0.88, 0.98]) and 0.944 (CI95% [0.86, 0.98]), respectively (p<0.0001 across all movements). Between-day reliability was similarly excellent, with Peak Flexion showing an ICC of 0.971 (CI95% [0.93, 0.99]), Peak Extension an ICC of 0.964 (CI95% [0.91, 0.99]), while Peak Right Lateral Flexion and Peak Left Lateral Flexion recorded ICCs of 0.961 (CI95% [0.90, 0.98]) and 0.967 (CI95% [0.92, 0.99]), respectively (p><0.0001 across all movements). Standard Error of Measurement ranged between 9.6 and 16.7 N, while the Minimum Detectable Change varied from 26.7 to 46.2 N across all movements. CONCLUSION The self-assessed neck strength test protocol, utilizing a 3D-printed fixation device and handheld dynamometer, offers a reliable, cost-effective, and accessible solution for monitoring neck strength. With its demonstrated strong reliability and precision, this protocol is well-suited for longitudinal tracking of neck strength. >˂0.0001 across all movements). Between-day reliability was similarly excellent, with Peak Flexion showing an ICC of 0.971 (CI95% [0.93, 0.99]), Peak Extension an ICC of 0.964 (CI95% [0.91, 0.99]), while Peak Right Lateral Flexion and Peak Left Lateral Flexion recorded ICCs of 0.961 (CI95% [0.90, 0.98]) and 0.967 (CI95% [0.92, 0.99]), respectively (p<0.0001 across all movements). Standard Error of Measurement ranged between 9.6 and 16.7 N, while the Minimum Detectable Change varied from 26.7 to 46.2 N across all movements. CONCLUSION The self-assessed neck strength test protocol, utilizing a 3D-printed fixation device and handheld dynamometer, offers a reliable, cost-effective, and accessible solution for monitoring neck strength. With its demonstrated strong reliability and precision, this protocol is well-suited for longitudinal tracking of neck strength.>˂0.0001 across all movements). Standard Error of Measurement ranged between 9.6 and 16.7 N, while the Minimum Detectable Change varied from 26.7 to 46.2 N across all movements.
Conclusion: The self-assessed neck strength test protocol, utilizing a 3D-printed fixation device and handheld dynamometer, offers a reliable, cost-effective, and accessible solution for monitoring neck strength. With its demonstrated strong reliability and precision, this protocol is well-suited for longitudinal tracking of neck strength.