Electromyographic study of neck muscle activity according to head position in rugby tackles

Ergonomic design and evaluation of gemstone polishing workstation

Objectives. Gemstone polishers suffer from musculoskeletal problems due to constrained working postures, substantially influenced by the poor design of conventional gemstone polishing workstations. The present study investigated the effects of three workstation adjustment parameters (illumination at workstation, polishing height, tool post position) on postural angle, muscle activity and perceived postural discomfort in order to develop recommendations for new gemstone polishing workstations. Methods. Twelve professional gemstone polishers performed the polishing task on a prototype test-rig in 27 different test conditions. Taguchi's L27 orthogonal array was employed to estimate the optimum setting for gemstone polishing workstation design. Results. Study variables had a significant influence on postural angles. Polishing height substantially influenced muscle activity and perceived discomfort in the shoulder and lower back region. Tool post position was found to be the determinant factor for forearm muscle activity and perceived discomfort in the wrist/forearm region. Based on the findings, illumination of 1500 lux, polishing at 15 cm above the elbow height and a 20° tool position was recommended. Conclusions. Our findings present an alternative approach to using Taguchi's design of experiment for workstation improvement, which has received very little attention in ergonomics studies. A confirmation test was conducted to validate the study recommendations.

Lay of the land: narrative synthesis of tackle research in rugby union and rugby sevens

Objectives

The purpose of this review was to synthesise both injury prevention and performance tackle-related research to provide rugby stakeholders with information on tackle injury epidemiology, including tackle injury risk factors and performance determinants, and to discuss potential preventative measures.

Design

Systematic review and narrative synthesis.

Data sources

PubMed, Scopus and Web of Science.

Eligibility criteria

Limited to peer-reviewed English-only publications between January 1995 and October 2018.

Results

A total of 317 studies were identified, with 177 in rugby union and 13 were in rugby sevens. The tackle accounted for more than 50% of all injuries in rugby union and rugby sevens, both at the professional level and at the lower levels, with the rate of tackle injuries higher at the professional level (mean 32/1000 player-hours) compared with the lower levels (mean 17/1000 player-hours). A player’s tackle actions and technical ability were identified as major risk factors for injury and a key determinant of performance.

Summary/conclusion

Evidence-based education, progressive tackle technique training with a high potential to transfer and law changes have been proposed as key modifiers of player tackle actions and technical ability. Conceivably, all three modifiers working in unison (as opposed to separately) will have a higher potential at reducing tackle injury risk while enhancing performance. With the guidance of tackle injury and performance studies, as well as stakeholder engagement, experiential and explorative tackle research has the potential to inspire innovative injury prevention and performance strategies.

Head and Neck Response of an Active Human Body Model and Finite Element Anthropometric Test Device During a Linear Impactor Helmet Test

It has been proposed that neck muscle activation may play a role in head response resulting from impacts in American Football. The importance of neck stiffness and active musculature in the standard linear impactor helmet test was assessed using a detailed head and neck finite element (FE) model from a current human body model (HBM) compared to a validated hybrid III head and neck FE model. The models were assessed for bare-head and helmeted impacts at three speeds (5.5, 7.4, and 9.3 m/s) and three impact orientations. The HBM head and neck was assessed without muscle activation and with a high level of muscle activation representing a braced condition. The HBM and hybrid III had an average cross-correlation rating of 0.89 for acceleration in the primary impact direction, indicating excellent correspondence regardless of muscle activation. Differences were identified in the axial head acceleration, attributed to axial neck stiffness (correlation rating of 0.45), but these differences did not have a large effect on the overall head response using existing head response metrics (head injury criteria, brain injury criteria, and head impact power). Although responses that develop over longer durations following the impact differed slightly, such as the moment at the base of the neck, this occurred later in time, and therefore, did not considerably affect the short-term head kinematics in the primary impact direction. Though muscle activation did not play a strong role in the head response for the test configurations considered, muscle activation may play a role in longer duration events.

Changes in the activity of the muscles surrounding the neck according to the angles of movement of the neck in adults in their 20s

[Purpose] The aim of this study was to examine changes in the muscle activity around the neck according to the neck movement angle during neck flexion and extension. [Subjects and Methods] Activities of the sternocleidomastoid muscle (SCM), splenius capitis and splenius cervicis muscles, upper trapezius muscle, and middle trapezius muscle during flexion and extension were assessed in 24 college students. [Results] SCM muscle activation significantly increased at every angle during flexion and extension. The activities of the splenius capitis and splenius cervicis muscles increased significantly during flexion. The activity of the upper trapezius muscle also increased significantly. [Conclusion] The results highlight the need for individuals not to adopt a neck flexion posture for extended periods.