The influence of muscle tremor on shooting performance

Energy intake, hydration status, and sleep of world-class male archers during competition

BACKGROUND

Nutritional intake and sleep, play an important role for recovery and performance in elite sport but little work has been undertaken in archery. The present study aimed to assess energy intake (EI), hydration status, and sleep parameters in world-class male archers over the course of a four-day competition.

METHODS

Results, Conclusions Six male, elite-standard archers participated in the study and measurements of hydration status, EI, competition load, and sleep were recorded throughout each day of competition.

RESULTS

Daily energy, carbohydrate, and protein intake ranged between 2,563 and 3,986 kcal, 4 and 7.1 g/kg BM, 2.2 and 3.6 g/kg BM per day, respectively. Thus, archers practiced elements of periodized nutrition such that energy and carbohydrate intake was greater on the high-volume competition days (i.e. days 1 and 3; more numbers of arrows, longer duration, and walking distance) in comparison to low-volume days (days 2 and 4) over the tournament (all p > 0.01). Additionally, urine specific gravity was higher after waking, compared to pre- and post-competition, and before bed (all p < 0.05). This indicates that archers were euhydrated pre- and post-competition and before bedtime, while they were slightly hypohydrated after waking up. Sleep data show that disturbances were kept to a minimum.

CONCLUSIONS

Collectively, archers appear capable of periodizing their nutritional intake according to daily physical loading during a tournament whilst, staying euhydrated and maintaining sleep quality. In part, such data can help to explain why these archers experience a sustained level of success.

Air pistol shooting: upper limb muscle activation between training and simulated competition

Heightened stress during air pistol competitions may impair shooters' abilities to maintain gun stability, resulting in inferior performance. This study aimed to compare the pre-trigger muscle activation levels of upper muscles in 10-m air pistol shooters between training and simulated competition conditions. Seven sub-elite shooters from the Singapore National Youth Air Pistol Team shot 30 shots in a training versus simulated competition condition in randomised orders on separate days. Muscle activation for the forearm and shoulder muscles, namely extensor carpi radialis, flexor carpi ulnaris, anterior deltoid, and posterior deltoid, were recorded using electromyography (EMG). Shooting performance was evaluated by total shot scores. Stress level was monitored via heart rate and the Mental Readiness Form-3. No statistically significant differences were found in EMG, performance, or stress-related variables between conditions, although moderate-to-large effect sizes were observed in some muscle activation and self-reported stress indicators. Analysis of individual performances using smallest worthwhile change showed that two participants improved under the simulated competition condition, while two declined, and three remained unaffected. In conclusion, sub-elite youth air pistol shooters were able to exhibit good neuromuscular control under high anxiety situations and thus their performance was largely unaffected.

The Effects of Hand Tremors on the Shooting Performance of Air Pistol Shooters with Different Skill Levels

Physiologic hand tremors are a critical factor affecting the aim of air pistol shooters. However, the extent of the effect of hand tremors on shooting performance is unclear. In this study, we aim to explore the relationship between hand tremors and shooting performance scores as well as investigate potential links between muscle activation and hand tremors. In this study, 17 male air pistol shooters from China's national team and the Air Pistol Sports Center were divided into two groups: the elite group and the sub-elite group. Each participant completed 40 shots during the experiment, with shooters' hand tremors recorded using three-axis digital accelerometers affixed to their right hands. Muscle activation was recorded using surface electromyography on the right anterior deltoid, posterior deltoid, biceps brachii (short head), triceps brachii (long head), flexor carpi radialis, and extensor carpi radialis. Our analysis revealed weak correlations between shooting scores and hand tremor amplitude in multiple directions (middle-lateral, ML: r2 = -0.22, p < 0.001; vertical, VT: r2 = -0.25, p < 0.001), as well as between shooting scores and hand tremor complexity (ML: r2 = -0.26, p < 0.001; VT: r2 = -0.28, p < 0.001), across all participants. Notably, weak correlations between shooting scores and hand tremor amplitude (ML: r2 = -0.27, p < 0.001; VT: r2 = -0.33, p < 0.001) and complexity (ML: r2 = -0.31, p < 0.001) were observed in the elite group but not in the sub-elite group. Moderate correlation were found between the biceps brachii (short head) RMS and hand tremor amplitude in the VT and ML directions (ML: r2 = 0.49, p = 0.010; VT: r2 = 0.44, p = 0.025) in all shooters, with a moderate correlation in the ML direction in elite shooters (ML: r2 = 0.49, p = 0.034). Our results suggest that hand tremors in air pistol shooters are associated with the skill of the shooters, and muscle activation of the biceps brachii (long head) might be a factor affecting hand tremors. By balancing the agonist and antagonist muscles of the shoulder joint, shooters might potentially reduce hand tremors and improve their shooting scores.

The effect of socially evaluated multitasking stress on typing rhythms

Individuals have unique typing rhythms characterized by specific keystroke dynamics. Changes in state and cardiovascular responding are well documented manifestations of the fight-flight response to stress. However, as stress also leads to changes in muscle tone and motor control, typing rhythms may also be impacted. We aim to determine which individuals are experiencing stress through their typing rhythms and identify universal keystroke markers of stress. Participants (N = 116) typed 80 repetitions of a 6-word, 30-character phrase before and after 15 min of critically evaluated multitasking stress. Cardiovascular, hemodynamic, and state variables were compared across baseline, stress, and recovery periods and measures of typing rhythm were derived for each period and classified using machine-learning algorithms. Critically evaluated multitasking led to significant changes in all stress measures, demonstrating highly robust stress reactivity. Machine learning algorithms accurately classified stressed typing for each individual based on their typing rhythms; however, no universal keystroke markers of stress were identified. Using typing rhythms. We were able to determine whether an individual was stressed or not, but the markers used for classification differed between individuals. These individual changes may provide opportunities for identifying stressful periods through keystroke monitoring, as well as the potential for early identification of disorders which may impact fine motor control. Typing rhythms could therefore be used to monitor health and well-being in individuals who use keyboards in various situations. This is the first rigorous assessment of stress and typing rhythms and has led to the development of a feasible and highly reproducible research protocol.

The Effect of Wet Conditions and Surface Combat Swimming on Shooting

INTRODUCTION

Shooting ability is an important aspect of performance in some sports and is vital during a military operation. Load carriage, clothing, and equipment normally associated with fatigue and reduced field of vision or lack of stability at a specific point are important factors that affect the ability to aim when shooting. Additionally, gun support and equipment appear to differentially affect shooting ability with varying shooting positions. All of the studies examining these factors have taken place on dry land and not in water. However, up to date, no study has examined the effect of wet conditions, especially after surface combat swimming (sCS), on shooting ability in different shooting positions. The purpose of this study was to determine the effect of fatigue, produced by prolonged sCS, on a fighter's shooting ability. In addition, we investigated whether the effect of fatigue and wet conditions differed between the shooting positions.

MATERIALS AND METHODS

Forty-five participants performed 10 shots in a shooting simulator while standing (ST) and 10 shots while kneeling (KN). This was performed twice and in three conditions: dry, wet, and after 1,000 m of sCS.

RESULTS

Wet conditions did not significantly affect shooting abilities. Surface combat swimming negatively affected shooting ability when both ST and KN. The reduction in the center of gravity (COG) of the shots after sCS was 3.7 ± 2.5% for ST and 3.5 ± 0.8% for KN (P < .01). This was accompanied by the increase in horizontal and vertical movement of the gun after the sCS (P < .01). Kneeling was more stable, as shown by a higher percentage of COG of the shots by 3.3 ± 0.1% (P < .01) and by fewer gun movements in both axes (P < .01).

CONCLUSIONS

In conclusion, combat swimming affects shooting ability, both in ST and in KN positions. The KN position provides better stability and improved shooting ability.

Analysis of physiological tremors during different intensities of armcurl exercises using wearable three-axis accelerometers in healthy young men: a pilot study

PURPOSE

The purpose of this pilot study was to determine whether physiological tremors (PTs) assessed using an accelerometer could be used to evaluate resistance exercise intensity.

METHODS

Twenty healthy young men with no prior experience of resistance exercise were recruited. Different intensities (resting, 30%, 50%, and 70% of their predetermined one-repetition maximum (1-RM)) of arm-curl exercise were used to elicit PT. The total work was held equally by varying the number of repetitions, with five sets for each intensity. Sessions of varying intensities were performed randomly with a washout period of at least a week. PT responses were recorded during exercise using accelerometers (3-axis) attached to the wrist and ear. Electromyography (EMG) data were obtained from the biceps brachii muscle during exercise. PT and EMG data were expressed as the average root mean square index.

RESULTS

The EMG amplitude increased significantly as exercise intensity increased. Furthermore, PT amplitude significantly increased as exercise intensity increased. Moreover, the Borg rating of perceived exertion (RPE) and lactic acid levels increased significantly. The wrist PT was related to ear PT, EMG, RPE, and lactic acid levels. Additionally, ear PT was associated with EMG, RPE, and lactic acid levels.

CONCLUSION

This pilot study identified changes in PT during resistance exercise at different intensities. We suggest that the use of PT analyses during these exercises provides a more intuitive delineation of resistance exercise intensity and fatigue.

Steady, Aim, Fire! Optimized Instructions Enhance Performance and Reduce Intra-Trial Variability in a Shooting Task

The present study examined the influence of the individual and sequential combination of the key components of OPTIMAL (Optimizing Performance Through Intrinsic Motivation and Attention for Learning) theory (i.e., enhanced expectancies, autonomy support, and external focus), on the performance of a laser-pistol shooting task. In addition to shooting accuracy, intra-trial variability in the sway of forearm/pistol motion prior to movement execution (pulling the trigger) was the primary variable of interest. In a between-within-subject design, thirty-six participants (Mage = 21.27 ± 1.75 years) were randomized into either a control or an optimized group. Enhanced expectancies, autonomy support, and an external focus were implemented via sequential blocks of trials for participants in the optimized group. Participants in the control group performed all trials under “neutral” conditions. Our results showed that motor performance was enhanced for participants in the optimized group compared to those in the control group. Moreover, greater reductions in forearm sway leading up to the trigger pull were observed for the optimized group compared to the control group. These findings suggest higher movement effectiveness and efficiency, potentially through better attunement to task and environmental constraints, when implementing optimized instructions in a self-initiated fine motor task.

Relationship between Accuracy, Speed, and Consistency in a Modern Pentathlon Shooting Event

In the modern pentathlon, the laser run is the highest influence on the results, and fast and accurate shooting is essential. This study evaluates the relationship between shooting characteristics (shot speed, consistency, accuracy) according to sex, competition type, and round number during laser run competitions among 19,648 modern shooting round cases from 2015 to 2019. As a result, men showed faster shot speed than women (p < 0.05, d = 0.493), and final rounds were significantly better than qualifier round in shot speed (p < 0.05, d = 0.176), consistency (p < 0.05, d = 0.138), and accuracy (p < 0.05, d = 0.151). Series-1 had the highest consistency (p < 0.05, ηp2 = 0.01) and accuracy (p < 0.05, ηp2 = 0.07) compared to other series. Series-4 had the lowest shooting speed (p < 0.05, ηp2 = 0.01) compared to other series. Consistency and speed showed moderate positive correlation (r = 0.362, p < 0.05). These results show differences in shot characteristics according to sex, competition type, and round number, and explain the relationship between shot speed and consistency. We believe these results will help relevant coaches and players aiming to improve performance understand shot characteristics and reduce shot time.

Pistol Shooting Performance Correlates with Respiratory Muscle Strength and Pulmonary Function in Police Cadets

Breathing patterns play a crucial role in shooting performance; however, little is known about the respiratory muscle strength and pulmonary capacities that control these patterns. The present study aimed to examine the relationship between shooting performance, respiratory muscle strength, and pulmonary function and to determine differences in respiratory capacities according to the shooting performance categories in police cadets. One hundred sixty-seven police cadets were recruited to assess respiratory muscle strength, pulmonary function, and shooting performance in a well-controlled environment. Measurements included maximal inspiratory pressure (MIP), maximal expiratory pressure (MEP), forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), slow vital capacity (SVC), maximal voluntary ventilation (MVV), and pistol shooting scores. The shooting score had a moderate positive correlation with MIP (ρ = 0.33) and MEP (ρ = 0.45). FVC (ρ = 0.25), FEV1 (ρ = 0.26), SVC (ρ = 0.26) (p < 0.001) and MVV (ρ = 0.21) (p < 0.05) were slightly correlated with shooting score. There were differences between shooting performance categories in MIP, MEP, FVC, FEV1, SVC, and MVV (p < 0.001, p < 0.05). The results imply that both strong respiratory muscles and optimal pulmonary function may be one of the necessary prerequisites for superior shooting performance in police.

Physical Stress and Determinants of Shooting Performance Among Norwegian Special Forces Operators

However, there is a lack of conceptual understanding of the factors influencing performance decrements in prone shooting. The present study examines how one can simulate a combat scenario by inducing acute physical stress, ultimately impacting one's shooting performance (SP). The relationship between participants' physical level and SP was measured in several ways. The SP of members of the Norwegian Navy Special Operations Forces (SOF) (N = 30) was measured before and directly after acute exercise-induced stress caused by a 200-m uphill run (90% HRmax). Under acute physical stress, participants took less time to fire five rounds (total 15.5 ± 10.9 s faster), and the probability of hitting the target was unaffected (92%). In terms of more sensitive measures, score was significantly reduced and shot-group dispersion increased (64 ± 90 cm2, p < 0.01, d = 0.72), mainly due to increased vertical dispersion (2.5 ± 4.6 cm, p < 0.01, d = 0.53). Age, trait somatic anxiety and the Big Five Inventory item "openness" explained 45.2% of the variance in shooting score in the pre-physical stress condition. In the post-physical stress condition, pre-test shooting score, the number of months deployed, and shooting time predicted 32.9% of the variance in shooting score. The change in SP (pre-post) showed the concentration disruption scale was the best predictor of the reduction in shot score (20.1%). From a practical point of view, maintaining the probability of hitting the target with reduced shooting time post-physical stress could be viewed as superior performance for SOF.

Neurofeedback training: Decreases in Mu rhythm lead to improved motor performance in complex visuomotor skills

The physiological function of the Mu rhythm (8-13 Hz in the central region) is still unclear, particularly its role in visuomotor performance in sports (shooting vs. golf putting), as both the complexity of the motor skills (i.e., simple vs. complex visuomotor skills) and the skill level (e.g., novices vs. experts or low-skilled vs. highly skilled) may modulate Mu rhythm. To gain a broader understanding of the association between Mu rhythm and visuomotor skill performance, a study design that considers both a control moderator (the difference in skill level) and the ability to manipulate Mu rhythm (i.e., either increase or decrease Mu rhythm) is required. To achieve this, we recruited 30 novice golfers who were randomly assigned to either the increased Mu rhythm group (IMG), decreased Mu rhythm group (DMG), or sham group (SG) and used electroencephalographic-neurofeedback training (EEG-NFT) to manipulate Mu rhythm during a golf putting task (complex visuomotor skill). The aim was to determine whether the complexity of the motor skill was a potential moderator of Mu rhythm. We mainly found that Mu power was significantly decreased in the DMG following EEG-NFT, which lead to increased motor control and improved performance. We suggest that (1) the complexity of the motor skill, rather than the difference in skill level, may be a potential moderator of Mu rhythm and visuomotor performance, as our results were not consistent with a previous study that reported that increased Mu rhythm improved shooting performance (a simple visuomotor task) in novices.

Executive Function Level in Cadets’ Shooting Performance

Executive functions (EF) are crucial to a person’s unique abilities, enabling one to achieve goals, adapt to new situations and manage social interactions. EF are also very important for the effective performance of military tasks including the shooting performance (SP) of soldiers. The aim of this study was to investigate the association of EF with SP and gender differences in the level of these traits among cadets of the General Tadeusz Kosciuszko Military University of Land Forces in Wroclaw i.e., 156 persons (19 females and 137 males). The level of EF and processes related to attention was measured with usage of the Color Trails Test (CTT-1 and CTT-2). SP was assessed on the basis of scores from four different small arms and rifle shootings at a fixed target and at emerging targets. The relations between explained and explanatory variables were assessed using Spearman correlation. The variation in the mean values of CTT scores and SP of men and women was compared using the Mann–Whitney U test for independent samples. The results of the present study did not reveal any significant differences between women and men in the level of EF and SP. The key finding of the present study is that the higher SP of males in all shooting events of the study and of females in pistol shooting were significantly correlated with higher executive functions.

Alternating Attention and Physical Fitness in Relation to the Level of Combat Training

The level of combat training (CT) of the future commander-leader is of critical importance to the armed forces in national defense. This study aimed to search for the relationship between the level of alternating attention, physical fitness and shooting accuracy (SA), and academic achievements in practical military subjects (PMS). The study group consisted of 137 cadets of the Military University of Land Forces. The measure of alternating attention in the study was the Color Trails Test results. Motor components were assessed by measuring hand static strength, endurance run, and time of a speed and agility run. SA and PMS were taken as measures of cadets’ CT. Significantly higher PMS were associated with higher levels of strength and better endurance in cadets. The physical fitness of the cadets did not significantly affect the cadets’ SA. The main result of the study is the revelation of the level of alternating attention as a strong determinant of cadets’ SA. The authors suggest that the main emphasis should be put on the physical preparation of a modern soldier, focused on the development of strength and endurance skills. It is also reasonable to introduce cognitive stimulation exercises to shooting training.

Anthropometric, Physiological and Psychological Variables That Determine the Elite Pistol Performance of Women

Shooting is a high-precision sport that depends on many factors to achieve high performance levels. The main objective of this study was to analyze the differences in anthropometric, physiological, and psychological variables by sport level in women air-pistol shooters. Fifteen female pistol shooters, including seven elite national shooters of Iran and eight non-elite shooters, participated in this study. Analyzed variables were grouped into three sections: anthropometric, physiological, and psychological. Anthropometric variables included: height, weight, body mass index, length of leg, arm span, and proportions between variables. Physiological tests include resting heart rate, static and dynamic balance, flexibility, and upper body strength. Additionally, psychological questionnaires of SMS-6 sport motivation, TSCI trait sport-confidence and SSCI state sport-confidence, ACSI-28 athletic coping skills, and SAS sport anxiety scale were used. The Shapiro–Wilks test and independent t-test were used to analyze the data. Effect size and test reliability were calculated using Cohen’s d and Cronbach’s alpha, respectively. Our results showed that elite shooters have higher values of dynamic balance (Y-test), upper body strength (sit-ups), and intrinsic motivation, and lower resting heart rate than non-elite. However, no differences were found in the anthropometric variables, nor in anxiety or coping skills. We conclude that physiological and psychological workouts should be included in the shooters’ training programs to improve their performance.

Practicing Sport in Cold Environments: Practical Recommendations to Improve Sport Performance and Reduce Negative Health Outcomes

Although not a barrier to perform sport, cold weather environments (low ambient temperature, high wind speeds, and increased precipitation, i.e., rain/water/snow) may influence sport performance. Despite the obvious requirement for practical recommendations and guidelines to better facilitate training and competition in such cold environments, the current scientific evidence-base is lacking. Nonetheless, this review summarizes the current available knowledge specifically related to the physiological impact of cold exposure, in an attempt to provide practitioners and coaches alike with practical recommendations to minimize any potential negative performance effects, mitigate health issues, and best optimize athlete preparation across various sporting disciplines. Herein, the review is split into sections which explore some of the key physiological effects of cold exposure on performance (i.e., endurance exercise capacity and explosive athletic power), potential health issues (short-term and long-term), and what is currently known with regard to best preparation or mitigation strategies considered to negate the potential negative effects of cold on performance. Specific focus is given to "winter" sports that are usually completed in cold environments and practical recommendations for physical preparation.

Effects of Dehydration on Archery Performance, Subjective Feelings and Heart Rate during a Competition Simulation

This study aimed to investigate the effect of dehydration on archery performance, subjective feelings and heart rate response. Ten national level archers performed two archery competition simulations, once under euhydration (EUH) and once in a dehydrated state (DEH), induced by 24-h reduced fluid intake. Hydration status was verified prior to each trial by urine specific gravity (USG ≥ 1.025). Archery score was measured according to official archery regulations. Subjective feelings of thirst, fatigue and concentration were recorded on a visual analogue scale. Heart rate was continuously monitored during the trials. Archery performance was similar between trials (p = 0.155). During DEH trial (USG 1.032 ± 0.005), the athletes felt thirstier (p < 0.001), more fatigued (p = 0.041) and less able to concentrate (p = 0.016) compared with the EUH trial (USG 1.015 ± 0.004). Heart rate during DEH at baseline (85 ± 5 b∙min^-1) was higher (p = 0.021) compared with EUH (78 ± 6 b∙min^-1) and remained significantly higher during the latter stages of the DEH compared to EUH trial. In conclusion, archery performance over 72 arrows was not affected by dehydration, despite the induced psychological and physiological strain, revealed from decreased feeling of concentration, increased sensation of fatigue and increased heart rate during the DEH trial.

The Relationship Between Pistol Olympic Shooting Performance, Handgrip and Shoulder Abduction Strength

The ability to stabilize the gun, a crucial factor for performance in air pistol Olympic shooting, is thought to be strongly related to the muscular work of the shooter´s shoulder and forearm. The objective of the present study was to confirm this relationship by analysing the influence of maximal finger flexor forces and maximal isometric shoulder force on performance in female air pistol shooting. Twenty‐three female pistol shooters participated in the study. Handgrip and shoulder force data were recorded under competition conditions, during the official training time of national Spanish championships on the day previous to the competition and at the official training stands. Performance was measured as the total score of 40 shots at competition. Linear regressions between performance and age, weight, height, training experience, body mass index (BMI), mean and maximal finger flexor and shoulder forces were calculated. Significant correlations were found between performance and a) training hours b) peak finger flexor force relative to the BMI, and c) peak isometric force of the shoulder abduction relative to the BMI. The study concludes that there is a statistically significant correlation between performance and muscular forces exerted by the athletes relative to their BMI. Appropriate muscular strength training programs are therefore necessary in female air pistol Olympic shooting.

Effect of caffeine ingestion on competitive rifle shooting performance

PURPOSE

The purpose of the present study was to test if caffeine ingestion affects rifle shooting accuracy in trained shooters.

METHODS

Twenty trained shooters performed 4 shooting tests in a randomized, double-blinded, placebo controlled crossover design; 2 identical tests after placebo ingestion and 2 after ingestion of 300 mg caffeine. The tests consisted of 30 shots in prone position and 30 in standing position on a 10 ring electronic target, on a distance of 50 metres, without any time limit, at rest.

RESULTS

Caffeine supplementation entailed a mean decrease in shooting performance by 11.8 points (95% CI: 6.7 to 17.0, effect size: 0.9). This was primarily a result of an 11.3 (95% CI: 7.2 to 15.4, effect size: 0.9) point decrease during shooting in standing position and not in prone position (0.6 point decrease, 95% CI: -2.1 to 3.2, effect size: 0.1).

CONCLUSIONS

We conclude that prior ingestion of 300 mg caffeine impairs rifle shooting accuracy in trained shooters when performed in standing but not in prone position.

Intermittent Hypoxic Training at Lactate Threshold Intensity Improves Aiming Performance in Well-Trained Biathletes with Little Change of Cardiovascular Variables

The main objective of this research was to evaluate the efficacy of intermittent hypoxic training (IHT) on aiming performance and aerobic capacity in biathletes. Fourteen male biathletes were randomly divided into a hypoxia group (H) (n = 7), which trained three times per week in a normobaric hypoxic environment (FiO₂ = 16.5%, 2000 m a.s.l.) with lactate threshold intensity (LT) determined in hypoxia, and a control group (C) (n = 7), which exercised under normoxic conditions with LT intensity determined in normoxia. The training program included three weekly microcycles, followed by three days of recovery. The main part of the interval workout consisted of four 7 min (1^st week), 8 min (2^nd week), or 9 min (3^rd week) running bouts at treadmill separated by 2 minutes of active recovery. After the warm-up and during the rest between the bouts, the athletes performed aiming to the target in the standing position with a sporting rifle (20 s). The results showed that the IHT caused a significant (p < 0.05) increase in retention time in the target at rest (RT9_rest) by 14.4% in hypoxia, whereas RT postincremental test (RT9_post) increased by 27.4% in normoxia and 26.7% in hypoxia. No significant changes in this variable were found in group C. Additionally, the capillary oxygen saturation at the end of the maximal effort (SO_{2capillary max}) in hypoxia increased significantly (p < 0.001) by ∼4% after IHT. The maximal workload during the incremental test (WR_max) in normoxia also increased significantly (p < 0.001) by 6.3% after IHT. Furthermore, in absolute and relative values of VO_2max in normoxia, there was a propensity (p < 0.07) for increasing this value by 5% in group H. In conclusion, the main findings of this study showed a significant improvement in resting and postexercise aiming performance in normoxia and hypoxia. Furthermore, the results demonstrated beneficial effects of the IHT protocol on aerobic capacity of biathletes.

Cardio-Respiratory Monitoring in Archery Using a Smart Textile Based on Flexible Fiber Bragg Grating Sensors

In precision sports, the control of breathing and heart rate is crucial to help the body to remain stable in the shooting position. To improve stability, archers try to adopt similar breathing patterns and to have a low heartbeat during each shot. We proposed an easy-to-use and unobtrusive smart textile (ST) which is able to detect chest wall excursions due to breathing and heart beating. The sensing part is based on two FBGs housed into a soft polymer matrix to optimize the adherence to the chest wall and the system robustness. The ST was assessed on volunteers to figure out its performance in the estimation of respiratory frequency (f_R) and heart rate (HR). Then, the system was tested on two archers during four shooting sessions. This is the first study to monitor cardio-respiratory activity on archers during shooting. The good performance of the ST is supported by the low mean absolute percentage error for f_R and HR estimation (≤1.97% and ≤5.74%, respectively), calculated with respect to reference signals (flow sensor for f_R, photopletismography sensor for HR). Moreover, results showed the capability of the ST to estimate f_R and HR during different phases of shooting action. The promising results motivate future investigations to speculate about the influence of f_R and HR on archers' performance.

The relationship between multiscale dynamics in tremulous motion of upper limb when aiming and aiming performance in different physical load conditions

The dynamics of tremulous motion in the upper limb is complex. We aimed to explore the relationship between the complexity of upper limb tremor when aiming and aiming performance and the influences of physical load on the two outcomes. Fifteen modern pentathlon athletes were recruited and completed two 1000-m treadmill running and three 60-s standard aiming task trials: one at baseline and each of the other two immediately after each running. The time series of light spot trace on the target was measured using a high-speed camera. The complexity of this time series was quantified using multiscale entropy. The effective aiming rate was used to assess the aiming performance. We observed that participants with lower tremor complexity had lower effective aiming rate across three physical load conditions (r² > 0.38, p < 0.01). Physical load decreased both tremor complexity (F = 4.8, p = 0.01) and effective aiming rate (F = 13.5, p < 0.0001), but no difference was observed after 1000-m running compared to that after 2000-m running. The per cent change of tremor complexity associated with the change of effective aiming rate (r² = 0.55, p < 0.0001). This pilot study demonstrates that multiscale complexity of tremulous motion in the upper limb when aiming may serve as a novel marker to assess the physiologic system functionality when aiming.

Postural balance and rifle stability in a standing shooting position after specific physical effort in biathletes

The aim of the study was to evaluate the effect of maximal specific physical effort on postural balance and rifle stability in biathletes in a standing shooting position. The study included 10 junior elite biathletes. The measurements were taken with the Vicon system and AMTI force platform. Postural balance and rifle stability characteristics were determined at rest as well as 1 and 5 min post maximal specific physical effort which was performed on a ski ergometer and continued until exhaustion. Maximal physical effort exerted a significant effect on all examined postural sway and rifle sway characteristics. The duration of the post-exercise changes was longer than 5 minutes. Higher post-effort rifle sway was observed in the vertical direction than in the across the shooting line direction. Post-effort postural balance impairment in the shooting line was much greater than in the across the shooting line direction. Moreover, a strong correlation was found between postural balance and rifle stability. Maximal physical effort influenced postural balance and rifle stability during aiming. Rifle sway during aiming in a standing shooting position seems to be coordinated with the postural sway of the biathlete's body. Thus, an increase in postural sway contributes to greater sway and lesser stability of the rifle.

Effect of heart rate on shooting performance in elite archers

Aim

The aim of the present study was to examine the effect of heart rate on shooting performance in elite archers.

Methods

Regularly trained 13 (7 female, 6 male) international level elite archers performed a (specific) protocol twice with 3 days interval in an indoor area. In order to raise the heart rate (HR) and related physiological stress the archers performed 4 sets of steady pace shuttle runs (males 10 km h^-1; females 8 km h^-1) for 3 minutes in a 20 m course following with 1 minute stop during which they performed 3 shots to 18 meter distance indoor target, and followed by 1 minute rest, where blood sample was collected from ear lobe for blood lactate (BL) analysis. Heart rate monitors were used for heart rate (HR) recordings with 5 seconds intervals for resting, running, shooting, and recovery periods. The score of the shots were recorded as in the normal archery indoor competition. Average (overall) results were taken into account for statistical analysis.

Results

Mean HR and BL during resting shoot in 1^st and 2^nd tests were 119.0 and 112.2 bpm (range 1^st test: 101–142 bpm, 2^nd test: 96–135 bpm) and 1.72 and 1.65 mmol.L⁻¹ (range 1^st test: 0.9–2.6 mmol.L⁻¹, 2^nd test: 0.8–2.3 mmol.L⁻¹) respectively. Mean HR and BL during post exercise shooting in 1^st and 2^nd tests were 168 and 166 bpm (range 1^st test: 152–191 bpm, 2^nd test: 147–188 bpm) and 4.21 and 3.44 mmol.L⁻¹ (range 1^st test: 1.3–7.0 mmol.L⁻¹, 2^nd test: 1.3–5.7 mmol.L⁻¹) respectively. There was not any statistically difference between shooting scores (27.50–27.23 points) after running exercise and resting (p > 0.05).

Conclusion

It was concluded that, under simulated indoor competition environment, high HR values do not influence short distance shooting scores.

Tremor in normal adults: A population-based study of 1158 adults in the Faroe Islands

There are virtually no population-based data on tremor in normal individuals. Using a population-based sample of 1158 normal adults ages 40-98 years in the Faroe Islands, we characterized the extent of normal action tremor across age and gender strata. Participants drew two Archimedes spirals with each hand, and tremor was systematically quantified by a senior movement disorder neurologist using a reliable and valid ordinal rating scale (ratings = 0-3). Tremor was nearly universal - 1145 (98.9%) participants had a total mean spiral score > 0. Older age was associated with more tremor (p < .001) and spiral scores were higher in males than females (p < .001). The proportion of individuals with a spiral rating ≥ 1.5 (i.e., more than mild tremor) was low (1.8% - 8.5%); however, this value reached 19.6% in left-hand spirals of males ≥70 years old. In this population-based study of more than one thousand normal adults, the vast bulk (i.e., 98.9%) had tremor on spiral drawing. In general, the tremor was mild. The proportion of individuals with tremor above the mild range varied across age and gender strata. These extensive data may be used as a gold standard for defining normal levels of tremor within adult populations.

The influence of physical exercise on the relation between the phase of cardiac cycle and shooting accuracy in biathlon

This study examined the influence of physical exercise on the relation between shooting accuracy and the phase of the cardiac cycle in which the shot is fired. Thirteen experienced biathletes (8 females, mean age 17 years) fired from the standing position at rest and right after a submaximal exercise on a bicycle ergometer. Shooting accuracy and the timing of each shot relative to the R-waves of the electrocardiogram (ECG) were recorded. Best shots (with greatest accuracy) and worst shots (with lowest accuracy) were fired prevalently in different phases of the cardiac cycle. In the rest condition, best shots were fired less frequently from 200 to 300 ms and more frequently from 500 to 600 ms after the R-wave, compared to worst shots. In the exercise condition, best shots were fired less frequently from 100 to 200 ms after the R-wave and from 20% to 30% of the R-R interval, compared to worst shots. These findings support the hypothesis that shooting accuracy is influenced by the cardiac cycle phase due to the ballistocardiac recoil generated at each heartbeat. To achieve best results athletes could be trained (e.g. through biofeedback) to fire within a specific phase of the cardiac cycle.

Prior Mental Fatigue Impairs Marksmanship Decision Performance

Purpose: Mental fatigue has been shown to impair subsequent physical performance in continuous and discontinuous exercise. However, its influence on subsequent fine-motor performance in an applied setting (e.g., marksmanship for trained soldiers) is relatively unknown. The purpose of this study was to investigate whether prior mental fatigue influences subsequent marksmanship performance as measured by shooting accuracy and judgment of soldiers in a live-fire scenario.

Methods: Twenty trained infantry soldiers engaged targets after completing either a mental fatigue or control intervention in a repeated measure design. Heart rate variability and the NASA-TLX were used to gauge physiological and subjective effects of the interventions. Target hit proportion, projectile group accuracy, and precision were used to measure marksmanship accuracy. Marksmanship accuracy was assessed by measuring bullet group accuracy (i.e., how close a group of shots are relative to center of mass) and bullet group precision (i.e., how close are each individual shot to each other). Additionally, marksmanship decision accuracy (correctly shooting vs. correctly withholding shot) when engaging targets was used to examine marksmanship performance.

Results: Soldiers rated the mentally fatiguing task (59.88 ± 23.7) as having greater mental workload relative to the control intervention [31.29 ± 12.3, t₍₁₉₎ = 1.72, p < 0.001]. Additionally, soldiers completing the mental fatigue intervention (96.04 ± = 37.1) also had lower time-domain (standard deviation of normal to normal R-R intervals) heart rate variability relative to the control [134.39 ± 47.4, t₍₁₈₎ = 3.59, p < 0.001]. Projectile group accuracy and group precision failed to show differences between interventions [t₍₁₉₎ = 0.98, p = 0.34, t₍₁₉₎ = 0.18, p = 0.87, respectively]. Marksmanship decision errors significantly increased after soldiers completed the mental fatigue intervention (48% ± 22.4) relative to the control intervention [M = 32% ± 79.9, t₍₁₉₎ = 4.39, p < 0.001]. There was a significant negative correlation between shooting response time and errors of commission (r = −0.61; p = 0.004) when preceded by the mental fatigue intervention, but not the control (r = −0.31; p = 0.17).

Conclusion: The mental fatigue intervention was successful in eliciting fatigue which was supported subjectively and objectively. Marksmanship judgment performance is significantly reduced when soldiers are mentally fatigued, although shot accuracy is not.

EFEITO DO ESFORÇO FÍSICO NO DESEMPENHO DE TIRO DE POLICIAIS MILITARES DO BATALHÃO DE CHOQUE

RESUMO Introdução: O uso de arma de fogo por policiais militares normalmente é precedido por perseguição a pé, e as alterações fisiológicas produzidas pelo esforço físico podem afetar o desempenho do tiro. Objetivo: Verificar o efeito do esforço físico sobre o desempenho de tiro em policiais militares. Métodos: A amostra foi constituída por 15 homens (34,1 ± 5,4 anos; 81,4 ± 8,8 kg; 171,3 ± 5,6 cm; 27,7 ± 2,3 kg/m²; 44,9 ± 4,0 ml.kg-1.min-1) do batalhão de choque da polícia militar. Na primeira sessão, os participantes realizaram um teste de esforço máximo em esteira no qual se mediu o consumo pico de oxigênio (VO2pico). Na segunda sessão, foi avaliado o desempenho (pontuação) e tempo de tiro pré e pós-esforço físico e o tempo gasto no circuito de corrida com obstáculos (297 m). O índice de eficiência de tiro foi calculado pela razão entre a pontuação total e tempo de execução de tiro. O teste de Shapiro-Wilk confirmou a normalidade da distribuição dos dados. Utilizou-se o teste t pareado para comparação das variáveis desfecho pré e pós-esforço e o coeficiente de correlação de Pearson. Resultados: O tempo para completar o percurso de corrida foi 75,3 ± 4,4 s. O desempenho (20,4 ± 11,4 vs. 17,6 ± 9,3 pontos), tempo (4,48 ± 1,1 vs. 4,23 ± 0,9 s) e eficiência de tiro (4,69 ± 2,7 vs. 4,35 ± 2,7 pts./s) não apresentaram diferenças significativas (P > 0,2). Além disso, detectou-se uma correlação entre o VO2pico e o tempo de execução da corrida (r = -0,64; P = 0,01), mas não com o desempenho de tiro (P > 0,05). Conclusão: O esforço físico não afeta o desempenho de tiro de policiais militares. Apesar de o nível de aptidão aeróbica não ser associado ao desempenho de tiro, foi associado ao desempenho físico realizado previamente aos disparos.

The Effect of Soldier Marching, Rucksack Load, and Heart Rate on Marksmanship

OBJECTIVE

The purpose was to determine if Soldier rucksack load, marching distance, and average heart rate (HR) during shooting affect the probability of hitting the target.

BACKGROUND

Infantry Soldiers routinely carry heavy rucksack loads and are expected to engage enemy targets should a threat arise.

METHOD

Twelve male Soldiers performed two 11.8 km marches in forested terrain at 4.3 km/hour on separate days (randomized, counterbalanced design). The Rifleman load consisted of protective armor (26.1 kg); the Rucksack load included the Rifleman load plus a weighted rucksack (48.5 kg). Soldiers performed a live-fire shooting task (48 targets) prior to the march, in the middle of the march, and at the end of the march. HR was collected during the shooting task. Data were assessed with multilevel logistic regression controlling for the multiple observations on each subject and shooting target distance. Predicted probabilities for hitting the target were calculated.

RESULTS

There was a three-way interaction effect between rucksack load, average HR, and march ( p = .02). Graphical assessment of predicted probabilities indicated that regardless of load, marching increases shooting performance. Increases in shooting HR after marching result in lower probability of hitting the target, and rucksack load has inconsistent effects on marksmanship.

CONCLUSION

Early evidence suggests that rucksack load and marching may not uniformly decrease marksmanship but that an inverted-U phenomenon may govern changes in marksmanship.

APPLICATION

The effects of load and marching on marksmanship are not linear; the abilities of Soldiers should be continuously monitored to understand their capabilities in a given scenario.

Tremors in white rhinoceroses (<i>Ceratotherium simum</i>) during etorphine-azaperone immobilisation

Little is known about the mechanisms causing tremors during immobilisation of rhinoceros and whether cardiorespiratory supportive interventions alter their intensity. Therefore, we set out to determine the possible mechanisms that lead to muscle tremors and ascertain whether cardiorespiratory supportive interventions affect tremor intensity. We studied tremors and physiological responses during etorphine–azaperone immobilisation in eight boma-held and 14 free-living white rhinoceroses. Repeated measures analysis of variance and a Friedman test were used to determine differences in variables over time and between interventions. Spearman and Pearson correlations were used to test for associations between variables. Tremor intensity measured objectively by activity loggers correlated well (p < 0.0001; r² = 0.9) with visual observations. Tremor intensity was greatest when animals were severely hypoxaemic and acidaemic. Tremor intensity correlated strongly and negatively with partial pressure of oxygen (PaO₂) (p = 0.0003; r² = 0.9995) and potential of hydrogen (pH) (p = 0.02, r² = 0.97). It correlated strongly and positively with adrenaline concentrations (p = 0.003; r² = 0.96), and adrenaline correlated strongly and negatively with PaO₂ (p = 0.03; r² = 0.95) and pH (p = 0.03; r² = 0.94). Therefore, hypoxaemia and acidaemia were likely associated with the intensity of tremors through their activation of the release of tremorgenic levels of adrenaline. Tremors can be reduced if circulating adrenaline is reduced, and this can be achieved by the administration of butorphanol plus oxygen insufflation. Furthermore, to assist with reducing the risks associated with rhinoceros immobilisation, tremor intensity could be used as a clinical indicator of respiratory and metabolic compromise.

Keeping still doesn't "make sense": examining a role for movement variability by stabilizing the arm during a postural control task

Small-amplitude, higher frequency oscillations of the body or limb are typically observed when humans attempt to maintain the position of a body or limb in space. Recent investigations have suggested that these involuntary movements of the body during stance could be used as an exploratory means of acquiring sensory information. In the present study, we wanted to determine whether a similar phenomenon would be observed in an upper limb postural task that does not involve whole body postural control. Participants were placed in a supine position with the arm pointing vertically and were asked to maintain the position of the limb in space with and without visual feedback. The wrist was attached to an apparatus that allowed the experimenter to stabilize or "lock" movements of the arm without the participants' awareness. When participants were "locked," the forces recorded predicted greater accelerations than those observed when the arm was freely moving with and without visual feedback. From unlocked to locked, angular accelerations increased in the eyes-closed condition and when participants were provided visual feedback of arm angular displacements. Irrespective of their origin, small displacements of the limb may be used as an exploratory means of acquiring sensory information from the surrounding environment.NEW & NOTEWORTHY The role of movement variability during a static limb position task is currently unknown. We tested whether variability remains in the absence of sensory-based error with an apparatus that stabilized the limb without the participant's knowledge during a static postural task. Increased forces observed during arm stabilization predicted movements greater than those observed when not externally stabilized. These results suggest movement variability during static postures could facilitate the gathering of sensory information from the surrounding environment.

Prediction of posture-dependent tremor by the calculation of the endpoint compliance

This paper proposes to use the analysis of human mechanical impedance to predict spatial behavior of tremor. Traditional studies have revealed that the variability in force is proportional to the mean level of force generated, which is described as signal dependent noise. The variability in force sometimes generates unintentional and uncontrollable rhythmic muscle movements, called tremor. Tremor appears most commonly on arms and hands due to not only a symptom of a neurological disorder, but also when we tighten our muscles. This study hypothesizes that the posture-dependent tremor at the hand is affected by the mechanical impedance of the arm, which is represented as the endpoint compliance ellipsoid. To verify this hypothesis, we measured the trajectory of the endpoint of the arm by human experiments, and compared the results with the endpoint compliance ellipsoid computationally obtained. The human experiment where the oscillations at the hand are measured revealed that the simulation results well correspond with the human experiments. This suggests that the posture-dependent motion noise is affected by the mechanical impedance of human body.

Failure of Arm Movement Control in Stroke Patients, Characterized by Loss of Complexity

We study the mechanism of human arm-posture control by means of nonlinear dynamics and quantitative time series analysis methods. Utilizing linear and nonlinear measures in combination, we find that pathological tremors emerge in patient dynamics and serve as a main feature discriminating between normal and patient groups. The deterministic structure accompanied with loss of complexity inherent in the tremor dynamics is also revealed. To probe the underlying mechanism of the arm-posture dynamics, we further analyze the coupling patterns between joints and components, and discuss their roles in breaking of the organization structure. As a result, we elucidate the mechanisms in the arm-posture dynamics of normal subjects responding to the gravitational force and for the reduction of the dynamic degrees of freedom in the patient dynamics. This study provides an integrated framework for the origin of the loss of complexity in the dynamics of patients as well as the coupling structure in the arm-posture dynamics.

Effect of carrying a rifle on physiology and biomechanical responses in biathletes

PURPOSE

This study aimed to assess the effect of carrying a rifle on the physiological and biomechanical responses of well-trained biathletes.

METHODS

Ten elite biathletes (five men and five women) performed ski skating with (R) or without a rifle (NR) on a treadmill using the V2 (5° incline) and V1 techniques (8°) at 8 and 6 km·h(-1), respectively, as well as at racing intensity (approximately 95% of peak oxygen uptake (V˙O2peak), 10.7 ± 0.8 and 7.7 ± 0.9 km·h(-1), respectively). V˙O2, ventilation (V˙(E)), HR, blood lactate concentration (BLa), and cycle characteristics as well as pole and leg kinetics were evaluated during these trials.

RESULTS

Metabolic data were all higher for R than for NR, as follows: V˙O2, +2.5%; V˙(E), +8.1%; RER, +4.2%; all P < 0.001; HR, +1.7%; and BLa, +15.1%; both P < 0.05. Biomechanically, carrying a rifle reduced cycle time and length, poling and arm swing times, and leg ground contact time and increased cycle rate, the peak and impulse of leg force, average cycle force, and impulse of forefoot force (all P < 0.05). With the exception of elevated pole forces when V2 skating at racing velocity, there were no differences between the peak and impulse of pole force. The difference in V˙(E) between R and NR was greater for the women than that for men (P < 0.05), and the difference in BLa also tended to be larger for the women (P < 0.1).

CONCLUSIONS

Carrying a rifle elevated physiological responses, accelerated cycle rate, and involved greater leg work, with no differences between the V1 and V2 techniques.

Task-specific kinetic finger tremor affects the performance of carrom players

We aimed to determine the effect of task-specific kinetic finger tremor, as indexed by surface electromyography (EMG), on the accuracy of a carrom stroke. Surface EMG of extensor digitorum communis muscle of the playing arm was recorded during rest, isometric contraction and stroke execution in 17 male carrom players with clinically observed finger tremor and 18 skill- and age-matched controls. Log-transformed power spectral densities (LogPSDs) of surface EMG activity (signifying tremor severity) at a 1-s pre-execution period correlated with angular error of the stroke. LogPSDs in 4-10 Hz range were higher in players with tremor than controls during pre-execution (P < 0.001), but not during the resting state (P = 0.067). Pre-execution tremor amplitude correlated with angular deviation (r = 0.45, P = 0.007). For the first time, we document a task-specific kinetic finger tremor in carrom players. This finger tremor during the immediate pre-execution phase appears to be a significant determinant of stroke accuracy.

Does Amphetamine Enhance Your Health? On the Distinction between Health and "Health-like" Enhancements

It is an imperative within health care, medicine, and public health to restore, preserve, and enhance health. Therefore, it is important to determine what kinds of enhancement are increases in health and what kinds are not. Taking as its point of departure two conceptions of health, namely, "manifest health" and "fundamental health," the paper discusses various means used to enhance ability and well-being, and if those means, such as wheelchairs, implants, medicines, stimulants, or narcotics, enhance health. The fact that some means that enhance ability or well-being are not usually considered health enhancing, for example, narcotics, constitutes a problem. The paper ends with a discussion of some suggestions about how to distinguish between those enhancements that are health related and those that are not. One plausible idea holds that an enhancement is health related when the substance, or aid, increases ability or well-being, is integrated into the body, and does not harm the individual's fundamental health.

Changes in physiological tremor resulting from sleep deprivation under conditions of increasing fatigue during prolonged military training

The aim of the study was to define the changes of the characteristics of physiological postural tremor under conditions of increasing fatigue and lack of sleep during prolonged military training (survival). The subjects of the study were 15 students of the Polish Air Force Academy in Dęblin. The average age was 19.9±1.3 years. During the 36-hour-long continuous military training (survival) the subjects were deprived of sleep. Four tremor measurements were carried out for each of the subjects: Day 1 – morning, after rest (measurement 0); Day 2 – morning, after overnight physical exercise (measurement 1); afternoon, after continuous sleep deprivation (measurement 2); Day 3 – morning, after a full night sleep (measurement 3). The accelerometric method using an acceleration measuring kit was applied to analyse tremor. A significant difference between mean values of the index evaluating tremor power in low frequencies L_2-4 in measurement 0 and measurement 3 was observed (p<0.01). No significant differences were found in mean values of index L_10-20. Mean frequencies F_2-4 differed significantly from each other (F_2,42=4.53; p<0.01). Their values were 2.94±0.11, 2.99±0.9, 2.93±0.07 and 2.91±0.07 for successive measurements. A gradual, significant decrease of F_8-14 was observed (F_2,42=5.143; p<0.01). Prolonged sleep deprivation combined with performing tasks demanding constant physical effort causes long-lasting (over 24 hours) changes of the amplitude of low-frequency tremor changes. This phenomenon may significantly influence psychomotor performance, deteriorating the ability to perform tasks requiring movement precision.

Detecting within- and between-day manifestations of neuromuscular fatigue at work: an exploratory study

Cumulative neuromuscular fatigue may result from exposure to physically demanding work, such as repetitive and/or sustained work with insufficient recovery. The aims of this exploratory study were to develop a battery of field usable fatigue measures and to document hand/arm fatigue in physically demanding work over multiple workdays and after a weekend break. Sixteen plumbers were observed for five days and measures of handgrip force, variability, tremor and discomfort were obtained pre-, mid- and post-shift. This exploratory study demonstrated increasing fatigue of the hand/arm over the day and persistent fatigue from Tuesday to Friday, and that a number of the measures did not return to baseline values following a weekend break. The findings provide preliminary evidence of cumulative fatigue in residential plumbing and insight into neuromuscular fatigue measurement. However, further work is needed to develop and refine a set of fatigue measures to detect neuromuscular fatigue at the workplace.

PRACTITIONER SUMMARY

Cumulative fatigue has been linked to long-term health outcomes, including work-related musculoskeletal disorders. This paper presents findings from a physically demanding job (i.e. plumbing) revealing persistent fatigue over the work shift(s) and insufficient recovery after a weekend break, and provides insight into fatigue measurement at the workplace.

Validation of a dumbbell body sway test in olympic air pistol shooting

We present and validate a test able to provide reliable body sway measurements in air pistol shooting, without the use of a gun. 46 senior male pistol shooters who participated in Spanish air pistol championships participated in the study. Body sway data of two static bipodal balance tests have been compared: during the first test, shooting was simulated by use of a dumbbell, while during the second test the shooters own pistol was used. Both tests were performed the day previous to the competition, during the official training time and at the training stands to simulate competition conditions. The participantś performance was determined as the total score of 60 shots at competition. Apart from the commonly used variables that refer to movements of the shooters centre of pressure (COP), such as COP displacements on the X and Y axes, maximum and average COP velocities and total COP area, the present analysis also included variables that provide information regarding the axes of the COP ellipse (length and angle in respect to X). A strong statistically significant correlation between the two tests was found (with an interclass correlation varying between 0.59 and 0.92). A statistically significant inverse linear correlation was also found between performance and COP movements. The study concludes that dumbbell tests are perfectly valid for measuring body sway by simulating pistol shooting.

Pursue or shoot? Effects of exercise-induced fatigue on the transition from running to rifle shooting in a pursuit task

To investigate to what degree exercise-induced fatigue influences behavioural choices, participants' transition from running to rifle shooting in a pursue-and-shoot task was assessed. Participants ran on a treadmill and chased a target in a virtual environment and were free to choose when to stop the treadmill and shoot at the target. Fatigue increased progressively throughout the 20-minute test. Results indicated that shooting accuracy was not affected by fatigue. However, the distance to the target at which participants decided to shoot showed a U-shaped relationship with fatigue, R(2) = 0.884, p = 0.013. At low fatigue levels (ratings of perceived exertion [RPE] < 6.5), the distance to the target at which participants shot decreased, whereas at higher fatigue levels (RPE > 6.5) shooting distance increased again. At high levels of fatigue, participants stopped running sooner, aimed at the target longer and shot less often. Findings indicate that physiological parameters influence not only perception but also actual transitions between different actions.

Tremor severity and age: a cross-sectional, population-based study of 2,524 young and midlife normal adults

Mild action tremor occurs in most normal people. Yet this tremor mainly has been studied within the context of advanced age rather than among the vast bulk of adults who are not elderly. Whether this tremor worsens during young and middle age is unknown. Using cross-sectional data from a large population-based study of young and midlife normal adults (age range, 18-60 years), we assessed whether increasing age is associated with more severe action tremor. Two thousand five hundred and twenty-four adults in Araihazar, Bangladesh, drew an Archimedes spiral with each hand. Tremor in spirals was rated (0-3) by a blinded neurologist, and a spiral score (range, 0-6) was assigned. Spiral score was correlated with age (r = 0.06, P = .004). With each advancing decade, the spiral score increased (P = .002) so that the spiral score in participants in the highest age group (age 60) was approximately twice that of participants in the youngest age group (age 18-19); P = .003. In the regression model that adjusted for potential confounders (sex, cigarettes, medications, asthma inhalers, and tea and betel nut use), spiral score was associated with age (P = .0045). In this cross-sectional, population-based study of more than 2500 young and midlife normal adults, there was a clear association between age and tremor severity. Although the magnitude of the correlation coefficient was modest, tremor severity was higher with each passing decade. These data suggest that age-dependent increase in tremor amplitude is not restricted to older people but occurs in all adult age groups.

Gender differences in hand stability of normal young people assessed at low force levels

To examine gender differences in hand stability, finger position and force holding tasks at low force levels were conducted with 30 male and 30 female young adults. Total fluctuation was defined as the standard deviation of measured data and fluctuation and the 10-Hz component of the physiological tremor were compared between maleand female subjects. In all tasks, the total fluctuation and the 10-Hz tremor were significantly larger in male subjects than females. On average, the fluctuation was 1.3 times larger and the 10-Hz tremor was 1.6 times larger. The results of this study suggest that women have superior hand stability compared with men at low force levels. Finger length, maximal voluntary contraction and surface electromyography were also measured and factors related to gender differences in hand stability are discussed. STATEMENT OF RELEVANCE: Hand stability is crucial for precise manual operations. This study demonstrated gender differences in hand steadiness at low force levels. Though hand dexterity cannot be explained only by hand stability, the results of this study are useful not only for occupational aptitude tests but also for neuropsychological tests.