Acquisition evaluations are expensive, have a high time liability, and tend to prioritize engineering requirements over human factors and good experimental design. Shooting serials usually consist of ...static prone shooting to minimize movement variability, increase reliability of accuracy and timing data or use a single data point to make acquisition decisions. To better understand the number of trials required to achieve representative performance of accuracy and timing, 60 shots from the standing unsupported position while cyclically moving the weapon from the low ready to shoot was utilized. Intra-class correlations, standard error of measurement, minimal detectable change, and sequential averaging analysis (SAA) were used to evaluate the variables of radial error, shot interval, x-bias and y-bias over the 60 shots. The number of trials required to achieve an intraclass correlation of greater than 0.8 ranged from 2 (shot interval) to 58 (y-bias), whereas SAA varied between 3 (x-bias) and 43 (shot interval) trials. When averaging 10 shots at a time, the moving intraclass correlation remained above 0.8 for radial error and y-bias between 7 and 15 shots, shot interval from the second shot, but x-bias never reached 0.8. The number of trials required to satisfy each reliability method was inconsistent, in line with previous literature. Given the limitations identified in the literature as well as practical considerations such as the preference for prioritizing radial error reasonable performance stability can be achieved after 15 shots, and using the moving intraclass correlation results it is recommended that the first six shots are discarded with the following nine shots used for analysis.
Defence acquisitions use accuracy measures as a discriminating factor in weapon purchases, but assessments are generally completed in static, supported postures at static targets with few differences ...being seen between configurations. The aim of this study was to investigate whether an assessment requiring repositioning between shots could reveal differences. Participants shot at a static target under four conditions: an unweighted rifle and the addition of a mass fixed at three different positions. Accuracy and timing as well as discomfort measures were captured and compared. Hit percentage, consistency and timing varied over time, and timing increased with the addition of mass in two out of the three conditions. There was an increase in discomfort with the addition of mass further from the participant. The results showed that relying on accuracy and consistency measures alone to make acquisition decisions could have the consequence of purchasing equipment not fit for the human.
Practitioner Summary: This research shows that relying on accuracy and consistency measures alone to make weapon-system acquisition decisions could have the consequence of purchasing equipment not fit for the user. Further research should focus on 'upstream' issues such as muscle fatigue and aim point stability in order to better understand human-weapon-system interactions.
Back muscle endurance is a predictor of future low back pain and is commonly assessed using the Biering-Sorensen Test (BST). Differences exist between ethnic groups that may affect the performance ...and interpretation of the BST and should be investigated. This study's aim was to explore objective and subjective measures of the BST in a Japanese group in comparison with previous studies in other ethnic groups. A total of 27 young male Japanese students performed the BST while measures of muscle fatigue were collected. The mean BST time (152.7 (32.5) s) was greater than the median of the reported mean times in other ethnic groups over the previous decade (128.6 s). Objective measures indicated that the Japanese subjects' lumbar muscles were as fatigued as those of previous studies, while subjective measures appear to indicate that subjects under-reported exertion. The better performance of the Japanese subjects in the BST may reflect physical, psychosocial and lifestyle differences related to ethnicity.
Statement of Relevance: Ergonomics research and practice needs to be applicable to different ethnic groups. Despite the substantial body of evidence on back muscle endurance and indications of potential ethnicity related differences, this had not been previously investigated. These results help ergonomists to interpret physical ergonomics evidence in a multi-ethnic world.
The purpose of this study was to compare surface electromyography (EMG) activation levels of selected neck muscles for two common neck-training modalities (Thera-Band and Cybex). Seventeen ...asymptomatic subjects (eight men and nine women) with a mean age 23.4 years were recruited. EMG activation normalized to maximal voluntary isometric contraction (MVIC) was measured with subjects performing exercises with green, blue, and black Thera-Bands and 50%, 70%, and 90% of 3RM for the Cybex modality. Four variables were used to depict exercise intensityaverage and peak EMG activation in the concentric and eccentric phases. Significant differences (P ≤ 0.05) in EMG activation were evident when comparing intensities of the Cybex modality with each other and when comparing the Cybex intensities with Thera-Band intensities in most cases. Minimal differences were found among differing intensities of Thera-Band. Thera-Band exercise resulted in low-level EMG activation (range, flexion 3.8-15.7% MVIC; range, extension 20.2-34.8% MVIC); therefore, such exercise may be useful in rehabilitation programs. Cybex exercise (range, flexion 20.9-83.5% MVIC; range, extension 40.6-95.8% MVIC) may be useful for occupation-related injury prevention. However, exercise prescription should be undertaken with care as the mechanical loading on passive spinal structures is unknown.
Performing specific neck strengthening exercises has been proposed to decrease the incidence of neck injury and pain in high performance combat pilots. However, there is little known about these ...exercises in comparison to the demands on the neck musculature in flight.
Eight male non-pilots performed specific neck exercises using two different modalities (elastic band and resistance machine) at six different intensities in flexion, extension, and lateral bending. Six Royal Australian Air Force Hawk pilots flew a sortie that included combinations of three +Gz levels and four head positions. Surface electromyography (EMG) from selected neck and shoulder muscles was recorded in both activities.
Muscle activation levels recorded during the three elastic band exercises were similar to in-flight EMG collected at +1 Gz (15% MVIC). EMG levels elicited during the 50% resistance machine exercises were between the +3 Gz (9-40% MVIC) and +5 Gz (16-53% MVIC) ranges of muscle activations in most muscles. EMG recorded during 70% and 90% resistance machine exercises were generally higher than in-flight EMG at +5 Gz.
Elastic band exercises could possibly be useful to pilots who fly low +Gz missions while 50% resistance machine mimicked neck loads experienced by combat pilots flying high +Gz ACM. The 70% and 90% resistance machine intensities are known to optimize maximal strength but should be administered with care because of the unknown spinal loads and diminished muscle force generating capacity after exercise.
Les treize contributions publiées dans ce volume des Cahiers de l’APLIUT mettent l’accent sur les mutations qui ont, le temps d’une carrière de baby boomer, transformé radicalement le métier ...d’enseignant. Les travaux des didacticiens et les recherches croisées entre les disciplines de référence ont bouleversé le regard sur l’apprentissage et les comportements. L’élaboration du Cadre européen commun de référence pour les langues (souvent abrégé en Cadre ou CECRL) transcrit cette vision nouvelle de l’enseignement/apprentissage désormais centré sur l’apprenant et sur le processus cognitif. Parallèlement, la révolution technologique a ouvert le champ des possibles et permis de développer l’apprentissage en autonomie et de redéfinir le rôle de l’enseignant. Enfin, l’intérêt pour les langues de spécialité n’a cessé de croître, élargissant le champ des recherches.
Les treize contributions publiées dans ce volume des Cahiers de l’APLIUT mettent l’accent sur les mutations qui ont, le temps d’une carrière de baby boomer, transformé radicalement le métier ...d’enseignant. Les travaux des didacticiens et les recherches croisées entre les disciplines de référence ont bouleversé le regard sur l’apprentissage et les comportements. L’élaboration du Cadre européen commun de référence pour les langues (souvent abrégé en Cadre ou CECRL) transcrit cette vision nouvelle de l’enseignement/apprentissage désormais centré sur l’apprenant et sur le processus cognitif. Parallèlement, la révolution technologique a ouvert le champ des possibles et permis de développer l’apprentissage en autonomie et de redéfinir le rôle de l’enseignant. Enfin, l’intérêt pour les langues de spécialité n’a cessé de croître, élargissant le champ des recherches.
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