Abstract
Introduction: This study presents secondary outcome analyses, in terms of muscle function [i.e., maximal voluntary contraction (MVC) and rate of torque development (RTD)] from a parallel group, single blinded, randomized controlled trial introducing a physical exercise training intervention aiming to reduce neck pain among military helicopter pilots and crew-members.Methods: Participants (50 pilots, 58 crew-members) were recruited from the Royal Danish Air Force and randomized to either an exercise-training-group (ETG; n = 35) or a reference-group (REF; n = 34). Participants in ETG received 20 weeks of self-administered exercise training specifically tailored to target the neck and shoulder muscles. REF received no training. Outcome: (1) MVC was measured for cervical extension and flexion as well as shoulder elevation and abduction, (2) RTD was measured for cervical extension and flexion. Adherence to training was self-reported and categorized as regular if performed at least once a week.Results: MVC for cervical extension was significantly increased at follow-up in ETG (37.5 ± 11.2 Nm at baseline, change: 2.1 ± 8.3 Nm) compared to REF (38.1 ± 10.7 Nm at baseline, change: −2.4 ± 6.8 Nm) according to intension-to-treat analysis (p = 0.018). Likewise, RTD was significantly increased in ETG for cervical extension (149.6 ± 63.3 Nm/s at baseline, change: 14.7 ± 49.0 Nm/s) compared to REF (165.4 ± 84.7 Nm/s at baseline, change: −16.9±70.9 Nm/s) (p = 0.034). The cervical extension/flexion MVC-ratio was significantly different at follow-up (p = 0.039) between ETG (1.5 ± 0.5 at baseline, change: −0.0 ± 0.3) compared to REF (1.5 ± 0.5 at baseline, change: −0.2 ± 0.4). Per-protocol analysis of MVC, including only participants in ETG with regular training adherence (n = 10), showed a significant increase for cervical extension (33.2 ± 7.3 Nm at baseline, change: 6.0 ± 5.4 Nm) and shoulder elevation right side (143.0 ± 25.8 Nm at baseline, change: 15.8 ± 18.1 Nm).Conclusion: Physical exercise training significantly improved MVC and RTD in the upper neck extensors. Only approximately 1/3 of participants in ETG adhered to training regularly, which likely attenuated the effectiveness of the training intervention on neck and shoulder muscle function. Future studies should focus on the practical implementation of self-administered exercise training to improve adherence.
Highlights
This study presents secondary outcome analyses, in terms of muscle function [i.e., maximal voluntary contraction (MVC) and rate of torque development (RTD)] from a parallel group, single blinded, randomized controlled trial introducing a physical exercise training intervention aiming to reduce neck pain among military helicopter pilots and crew-members
This paper presents secondary outcome analyses, in terms of muscle strength, from a randomized controlled trial introducing a physical exercise training intervention aiming to reduce and prevent neck pain among military helicopter pilots and crew-members [30]
The main findings of this study were that: [1] 20 weeks of physical exercise training, designed to reduce and prevent neck pain, significantly improved MVC and RTD in the cervical extensor muscles of military helicopter pilots and crew-members, [2] participants with regular training adherence increased their MVC for shoulder elevation in the right side significantly, and [3] the physical exercise intervention proved preventive in terms of maintaining the cervical extension/flexion MVC-ratio, that decreased significantly in REF from baseline to follow-up
Summary
This study presents secondary outcome analyses, in terms of muscle function [i.e., maximal voluntary contraction (MVC) and rate of torque development (RTD)] from a parallel group, single blinded, randomized controlled trial introducing a physical exercise training intervention aiming to reduce neck pain among military helicopter pilots and crew-members. Muscle strain is affected by adapted postures during flight, and studies have found positioning of the head and body to have greater influence on muscle strain than the load due to head-worn equipment such as NVG [9, 10] We addressed this issue during real flight scenarios [11]. External loading on the cervical spine, by use of a helmet and NVG, may potentially evolve into excessive internal loading of the cervical vertebrae and the musculature supporting the neck. This might translate into the high prevalence of neck pain observed within the helicopter community
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