The Validity and Reliability of a Novel Testing Device and Six‐Way Neck‐Strength Testing Protocol for Peak Force and Rate of Force Development

Neck strength is hypothesised to mitigate head/neck injury and head acceleration events. Studies often only assess maximal isometric neck strength in flexion, extension, and lateral flexion and few consider the criterion and ecological validity of the devices and protocols used. This study aimed to (1): evaluate the validity and reliability of a novel strength-testing device (LINK), and (2) determine the reliability of a practical six-way (flexion, extension, lateral flexion, rotation) neck-testing protocol for peak force (PF) and rate of force development (RFD). LINK validity and reliability were assessed in two parts: (A) criterion validity and inter-/intra-LINK reliability for PF against Kistler force platforms; and (B) criterion validity for PF and RFD during an isometric mid-thigh pull compared with the force platforms. Intra-tester inter-session reliability of the neck testing protocol was determined across two sessions. Reliability was assessed using intraclass correlation coefficients (ICC). All LINKs demonstrated excellent intra-LINK reliability. Two LINKs showed agreement with the force platforms up to 606.8 N (mean bias: 10.6 [2.8-18.4] N and 10.7 [0.6-20.8] N) and excellent inter-LINK reliability (ICC lower bound > 0.99). One LINK was removed from further analysis due to higher mean bias (23.7 [9.6-37.8] N). The six-way protocol demonstrated moderate-to-excellent reliability for PF (ICC 0.83-0.95; 95% CI between 0.53-0.99), but not for RFD (ICC 0.41-0.94; -0.30 to 0.99). Meaningful detectable changes in neck strength ranged from 38.9 to 58.0 N. This study presents a valid, reliable method for assessing neck PF across six directions.