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Purpose: Altered head range of motion (RoM) and head repositioning accuracy (HRA) are commonly reported in neck pain. However, the quality of motion (QoM) is currently not easy to assess clinically. This study investigated the agreement of head rotation recordings using a 3D camera system compared to a commercially available inertial measurement unit (MOTI). Materials and methods: Thirty participants, mean age 26.5 years old (SD 4.4), partook in this study. Participants wore a Headband with MOTI and markers for 3D motion capture analysis during head rotations. The two systems recorded active head RoM in rotation, HRA, and QoM. Agreement of RoM, HRA and QoM data was compared between the two systems using Interclass correlation coefficients (ICC; 2.1) and Bland-Altman plots. Results: Good to excellent agreement between the two systems was seen for RoM (ICC: 0.998), HRA (0.75–0.88) and QoM (ICC: 0.911–0.913). The Bland-Altman plots revealed a systemic offset where the MOTI device measured higher values for RoM (mean bias: −0.56 ± 0.65°), HRA (mean bias: 0.48 ± 0.76°) and QoM (mean bias: −16.9 ± 51.6 A.U.). Conclusion: The present study found that the MOTI device can accurately measure RoM, HRA and QoM during head rotation. MOTI may be preferred over a 3D camera system for clinical use.

Neck pain is a common musculoskeletal problem often accompanied by reduced exercise-induced hypoalgesia (EIH) or hyperalgesia compared with an asymptomatic population. This study investigated EIH in a healthy population during experimental neck pain. Forty participants were randomized into this double-blinded parallel-group study. On 4 separate test days (day 0, day 2, day 4, and day 15), participants completed the Neck Disability Index and scored neck pain intensity during head movements on a numerical rating scale. At the end of day 0 and day 2, nerve growth factor (NGF) or isotonic saline (control) was injected into the right splenius capitis muscle. Pressure pain thresholds (PPTs) were recorded bilaterally over splenius capitis (neck), temporalis (head), and tibialis anterior (leg) muscles on all days. On day 0, day 4, and day 15, PPTs were recorded before and after a hand-bike exercise. Exercise-induced hypoalgesia was defined as the PPT increase caused by the exercise. Compared with the control group, the NGF group demonstrated higher Neck Disability Index scores at day 2 and day 4 (P < 0.001, η 2> 0.557) and higher numerical rating scale scores (P < 0.03, η 2> 0.09) along with reduced neck PPTs (P < 0.01, d > 0.44) at day 2 (right: 95% confidence interval [CI] [26.0-54.0]; left: 95% CI [6.8-26.9]), day 4 (right: 95% CI [40.5-67.9]; left: 95% CI [6.9-28.2]), and day 15 (right: 95% CI [5.6-37.2]; left: 95% CI [6.9-34.8]). Across days, the EIH effect was reduced at the neck site in the NGF group compared with the control group (P < 0.001, ηp2 = 0.367, 95% CI [-34.5 to -13.7]). At the head and leg sites, the NGF group showed reduced EIH effect compared with the control group (P < 0.05, d > 0.43) on day 4 (head: 95% CI [-61.4 to -22.9]; leg: 95% CI [-154.7 to -72.4]) and day 15 (head: 95% CI [-54.3 to -7.6]; leg: 95% CI [-122.7 to -34.4]). These results indicate that a few days of clinically comparable neck pain and hyperalgesia might have a negative impact on EIH responses and may help explain why some patients with neck pain do not experience immediate positive effects of exercise.

Background: Neck pain is a common problem in the general population, and movement adaptations are a natural response to pain. Previous studies have reported reduced trunk rotation during walking in those suffering from clinical neck pain. However, it is unknown how soon after the onset of pain, movement adaptations are adopted. This study investigated the effect of prolonged experimental neck pain four days after pain onset on gait kinematics during walking. Methods: Forty healthy participants were randomized to receive injections of nerve-growth-factor or a control injection of isotonic saline into the right splenius capitis muscle at the end of days 0 and 2. Participants performed two walking tasks, walking and walking while reading on a smartphone, on days 0, 4, and 15. Gait kinematics, spatiotemporal parameters, and gait stability were measured using Xsens Awinda. Findings: The nerve-growth-factor group reported increased neck pain intensity (median VAS 17.5 [IQR: 2.75–25.75]) on day 4 compared to day 0 and day 15. No pain intensity changes between days were reported for the isotonic-group. For gait kinematics, a main effect of the task was identified, showing that during the smartphone condition, participants had shorter stride lengths and reduced RoM for the trunk, hip, knee, and ankle compared to normal waking (P < 0.006). Interpretation: Walking while reading on a smartphone, but not mild neck muscle pain, caused changes in the gait kinematics compared to normal walking without neck pain. This finding suggests that movement alterations during walking are not an early feature of prolonged experimental neck pain.

Introduction: Sitting posture may contribute to spinal pain. Effects of postures on pain, sensitivity and muscle activity during computer tasks were investigated. Methods: Twenty-five healthy participants, seated at a workstation without backrest, completed four, 15-min typing tasks: A)Upright with forearm-support; B)Upright without forearm-support; C)Slumped with forearm-support; D)Slumped without forearm-support. Participants rated pain every minute on a numerical rating scale (NRS). RMS-EMG was recorded from upper/lower trapezius (UT, LT), serratus anterior and anterior/middle deltoid. At baseline and after tasks, pressure pain thresholds (PPTs) were recorded bilaterally over the head, UT, and leg. Results: All tasks caused clinically relevant increased NRS (≥2/10) compared to baseline (P < 0.001). NRS was higher in Task-D (P < 0.003) and lower in Task-B (P < 0.005) than others. PPTs did not change from baseline. Task-D caused higher UT and LT RMS-EMG (P < 0.02) than other tasks. Conclusion: A 15-min task caused pain irrespective of posture with some causing larger changes than others.