Christopher Heim

The Risk of Involuntary Firearms Discharge

Objectives: To investigate whether unintended muscle activity induced by motor overflow can result in the unintentional discharge of a firearm. Background: In the past few years an increasing number of people have been injured, sometimes fatally, as a result of police weapons being discharged involuntarily. Methods: Two experiments were performed using a pistol fitted with sensors to register the pressure exerted on the hand stock and the trigger. In Study 1, 34 police officers reacted to a set case using the prepared pistol. In Study 2, 25 participants performed 13 tasks requiring the use of different limbs. Results: In Study 1, about 20% of participating officers made contact with the trigger, thus violating police regulations to keep the trigger finger outside the trigger guard at all times until a conscious decision to fire has been made. Study 2 showed that motor activity in different limbs leads to a significant increase in grip force exerted on a firearm (significant results for 12 of 13 trials, Bonferroni-corrected p < .004). Furthermore, pressure on the trigger resulting from involuntary muscle contractions was, in certain cases, sufficient to unintentionally discharge a weapon. Conclusion: Unintentional discharges attributable to involuntary muscle activity can be a real danger for police officers when carrying out their duties. Application: Results may help improve police training with the aim of reducing the danger of involuntary discharges in real-life situations.

Towards an understanding of involuntary firearms discharges

Purpose – To identify environmental and physiological factors that may interact to bring about accidental discharges of firearms; and to make suggestions regarding the training of police officers with the aim of reducing such incidents.Design/methodology/approach – A pistol was fitted with sensors to register the pressure exerted on both the hand‐stock and the trigger of the weapon. Participants then performed 13 different tasks, each of which required the use of different limbs while holding the prepared weapon.Findings – Results suggest that motor activity in different limbs can lead to a significant increase in grip force exerted on a firearm, and that the amount of force exerted on the weapon is dependent on the intensity and type of movement and the limb involved in the movement. For movements of the contralateral arm a tendency for higher forces to be exerted on a weapon during pulling than during pushing movements was found, whereas the force with which the movement was performed did not seem to ha...

Construct and correlates of basic motor competencies in primary school-aged children

Background A central aim of physical education is the promotion of basic motor competencies (in German: Motorische Basiskompetenzen; MOBAK), which are prerequisites for childrens active participation in sports culture. This article introduces the MOBAK-1 test instrument for 6- to 8-year-old children and determines the construct validity of this test instrument. In addition, the relationship between MOBAK and motor ability (i.e., strength) as well as body mass index (BMI), sex, and age is investigated. Methods We analyzed data of 923 first and second graders (422 girls, 501 boys, ageu2009=u20096.80u2009±u20090.44 years). The childrens basic motor competencies were assessed by the MOBAK-1 test instrument. Besides analyses of frequency, correlation, and variance, 3 confirmatory factor analyses with covariates were performed. Results We found 2 MOBAK factors consisting of 4 items each. The first factor, locomotion, included the items balancing, rolling, jumping, and side stepping; the second factor, object control, included the items throwing, catching, bouncing, and dribbling. The motor ability strength had a significant influence on the factors locomotion (βu2009=u20090.60) and object control (βu2009=u20090.50). Older pupils achieved better results than younger pupils on object control (βu2009=u20090.29). Boys performed better on object control (βu2009=u2009−0.44), whereas girls achieved better results in locomotion (βu2009=u20090.07). Pupils with a high BMI achieved lower performance only on the factor locomotion (βu2009=u2009−0.28). Conclusion The MOBAK-1 test instrument developed for this study meets psychometric validity demands and is suitable to evaluate effects of sports and physical education.

Does exercise identity moderate affective and cognitive reactions to feedback on physical fitness

Objectives: The aim of this study was to examine the moderating role of exercise identity on the processing of feedback on self‐relevant physical fitness. It was hypothesized that individuals with a strong exercise identity would react cognitively more positively to consistent feedback than to positive feedback (self‐consistency principle), whereas individuals with a weak exercise identity were expected to react affectively more positively to positive feedback than to consistent feedback (self‐enhancement principle). Design: Cross‐sectional. Method: 215 university students (64.2% male, Mage = 23.82 years, SD = 2.32) were given bogus feedback on their results on an alleged fitness test based on heart rate variability in a laboratory setting. Affective and cognitive reactions were assessed afterwards. Data were examined using moderated regression analyses. Results: Exercise identity did not moderate affective reaction. For cognitive reaction, an interaction contrary to expectations was found: Individuals with a very weak exercise identity reacted more positively to consistent feedback than to positive feedback. Further, individuals with a strong exercise identity reacted more negatively to negative feedback than to consistent feedback. Conclusions: The hypotheses could not be confirmed. Cognitive reaction to negative feedback became more negative with a stronger exercise identity, whereas consistent feedback was received more positively as the strength of exercise identity increased. In future research focus should be on integrating the processing of negative feedback on a theoretical basis and should involve investigation into other relevant moderating variables. HighlightsParticipants were provided with consistent, positive, or negative bogus feedback.Exercise identity strength did not moderate affective reaction to fitness feedback.Affective reaction seems to be driven by self‐enhancement strivings.Exercise identity moderated cognitive reaction but not in the expected direction.