¹Université Laval, Québec, Canada
²Centre interdisciplinaire de recherche en réadaptation et intégration sociale (CIRRIS), Québec, Canada
³Forest Department and Wildlife Park (wildlife sector), Chibougamau, Canada

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Introduction: One of the tasks of some wildlife technicians is to capture animals using a net gun aboard a helicopter. Workers’ expertise relies on task precision (a low or high shot can result in an accident and crew fatality) and physical endurance (grip force required to hold the gun still during shooting implied 85% of the maximal voluntary contraction (MVC)(unpublished data)), which are considered key personal factors that can influence net gun shooting performance. Static muscular work of this amplitude cannot be sustained for very long, and rest time must be taken to avoid muscle fatigue, defined as a reduction in MVC after exertion. There is no consensus on the effect of fatigue on performance. The unique nature of net gun shooting, the lack of data specific to this task and the issues related to expertise and fatigue in this skill are reasons to study this task specifically.

Methods: Seven professional wildlife technicians (experts) and seven age- and height-matched novices were recruited. For kinematic data, an Xsens Link system was used to measure shoulders, elbows and trunk joint angles. Surface electromyography (EMG) was used to record muscle activity of the anterior deltoid, biceps, upper trapezius of the left side, and upper trapezius, middle deltoid of the right side. MVC values were obtained for EMG normalization and upper-body perceived exertion was asked after each of the 20 shooting trials. Virtual reality scenarios of wildlife capture were presented, separated by a fatigue protocol (i.e. 20 push-ups and 20 elbow flexions with the net gun following each block of five trials, for a total of three exercise sessions). Dependent variables were submitted to within-subject and between-subject mean comparisons (p<0.05).

Results: The perceived exertion significantly increased over the course of the blocks (p<0.001). Increase EMG activity level in left anterior deltoid and decrease in median frequency (p<0.05) indicated that the task was sufficiently demanding to induce fatigue. Muscle activity on the left side appears to be lower for experts than for novices (p<0.05). The Novice group’s muscle coactivation scores became lower as the blocks progressed, while the Experts maintained a similar, lower score across all four blocks (p<0.05). The univariate test showed an increase in sagittal trunk flexion and right elbow flexion in the expert group (p<0.01).

Discussion: These results suggest that the experts used a different strategy that allowed them to maintain a lower, constant level of muscle coactivation. Fatigue seems to affect the positioning of the weapon which could potentially increase the aiming height of the net gun.

Conclusion: The task-related physical component involved in the shooting task is significant, and that physical skills should be taken in consideration. Future work should improve the realism of the scenario and measure shooting accuracy to better understand the different strategies used by experts and the physical requirements of the task. The potential influence of gender should also be addressed.