An electromyographic evaluation of elastic band exercises targeting neck and shoulder pain among helm bearing military helicopter crew

Autor: Lars Askær Kristensen, Thomas Stig Grøndberg, Mike Murray, Gisela Sjøgaard, Karen Søgaard
Jazyk: angličtina
Rok vydání: 2015
Zdroj: Kristensen, L A, Grøndberg, T S, Murray, M, Sjøgaard, G & Søgaard, K 2015, ' An electromyographic evaluation of elastic band exercises targeting neck and shoulder pain among helm bearing military helicopter crew ', 7th Annual Meeting of the Danish Society for Biomechanics, Aalborg, Denmark, 25/11/2015 .
University of Southern Denmark
Popis: INTRODUCTION Flight related neck and shoulder pain is a frequent problem in helicopter pilots and crew [1]. Pain causes personnel suffering, reduces operational capabilities and incurs high financial cost due to the loss of manpower. Evidence suggests that the occupational loading such as posture adopted during flight and increased weight added to the mass of the head due to the helmet and night vision equipment contribute to the development of neck and shoulder pain. Strength training has among other occupational groups been found to reduce musculoskeletal pain [2]. A 20-week exercise program for the neck and shoulder muscles using elastic bands has been applied for helicopter pilots and crew in the Royal Danish Air Force to prevent and reduce pain. The exercise program had an initial loading of 20RM and was increased progressively towards 12RM in the final weeks. A muscle activity >60% MVE is generally considered necessary for gaining strength, but with elastic bands it is hard to control exercise intensity [3]. The purpose of the present study was to conduct an electromyographic evaluation of the neuromuscular activity in trapezius descendens, sternocleidomastoideus and the upper neck extensors during an elastic band exercise program targeting neck and shoulder pain among military helicopter pilots and crew. METHODS The study was conducted in a laboratory setting at University of Southern Denmark, Odense. A group of 11 healthy males (25,9±1,4 years) with no pain in neck or shoulders (VAS=0) were included in the project. Electromyographic activity and fatigue development was measured in trapezius descendens, sternocleidomastoideus and the upper neck extensors. Measurements were obtained during cervical extension, cervical flexion, lateral flexion, cervical rotation, reverse flyers and shrugs. Testing was conducted over three separate days. Familiarization with the exercises and assessment of loadings corresponding to 12RM and 20RM were found on two individual days. These loadings were then used in a test session and EMG data were obtained. The order of exercises was randomized for each individual. Electromyographic amplitude during exercise testing was for each muscle offline normalized to the maximum amplitude obtained during muscle specific maximal voluntary isometric contraction (% MVE). RESULTS Shrugs and reverse flyers induced >60% MVE in trapezius and were significantly higher than all the remaining exercises. Trapezius activity in the remaining exercises did not exceed 20% MVE. Cervical extension produced the highest numerical activity in the upper neck extensors, but was not significantly higher than shrugs and reverse flyers during 12RM and 20RM. Cervical flexion and shrugs produced an activity >60% MVE during 12RM. Cervical flexion produced the highest activity in sternocleidomastoideus during both 12RM and 20RM but this was not significantly higher than for cervical rotation and lateral flexion. No exercises induced an activity >60% MVE in sternocleidomastoideus. Significantly higher activity was observed during 12RM compared with 20RM during all exercises except in cervical flexion. Differences between the 12 and 20 RM were only observed for the highest activated muscles during each exercise. A significantly higher activity was obtained during the concentric phase compared with the eccentric phase of muscle contraction. DISCUSSION Trapezius was specifically activated by shrugs and reverse flyers. An important observation was that reverse flyers and shrugs also induced high activity of the upper neck extensors and this was not significantly different from the specific neck exercise, cervical extension. To our knowledge this has not previously been demonstrated for the shrug exercise. This finding can have important implications as it indicate that the use of specific exercises for the cervical musculature may not be needed. Several exercises activated sternocleidomastoideus between 38%-49% MVE indicating that this muscle has multiple functions of the cervical spine. Nevertheless, no exercise induced an activity >60% MVE of sternocleidomastoideus. The concentric phase induced significantly higher activity compared with the eccentric phase of muscle contraction, indicating that the participants followed the stated repetition speed. CONCLUSIONS This electromyographic evaluation of neck and shoulder exercises documents that the type and intensity of exercise played a significant role for the activity in specific muscle groups. Shrugs and flyers were highly effective exercises as they induced high muscle activity of both shoulder and neck muscles. These findings have practical implications for the choice of exercises for training programs targeting muscle specific pain and disorders. REFERENCES 1. Ang B, et al. Neck pain and related disability in helicopter pilots: A survey of prevalence and risk factors. Aviation, space and environmental medicine. 77:713-9, 2006. 2. Smidt N, et al. Effectiveness of exercise therapy: a best-evidence summary of systematic reviews. The Australian journal of physiotherapy. 51:71-85, 2005 3. Ratamess NA, et al. American College of Sports Medicin position stand. Progression models in resistance training for healthy adults. Medicine and science in sports and exercise. 41:687-708, 2009.
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