PSXV-18 Dynamics of steroid hormones in young fine harness horses during the preparatory period of the race-course training

The aim of the study was to determine the dynamics of steroid hormones (pg /ml) in 2-year-old mares and stallions. During preparatory training, at rest, stallions and mares had similar testosterone levels (0,98±0,745-0,82±0,013), estradiol (21.18±5.05–22.50±3.01) and cortisol (90.17±2.11–83.26±2.48), respectively. In response to submaximal power, stallions and mares expend their reserves uneconomically, expressed in an increase of testosterone (9.54±0.353 – 19.59±1.85) and cortisol (203.07±8.70 -245.57±18.60). The estradiol in stallions fell 27% to 16,68±3,01, and in mares increased by 9% (24.50±0,89). At the end of the preparatory period, stallions showed increase in testosterone by 13 (to 13.47±2,21), cortisol 1.5 times (139,12 ±of 12.97), a fall in estradiol levels 5.3 times (to 4.00± 1,72). The content of testosterone in mares increased by 8.6 times (to 7.09±0.97), cortisol by 2.2 times (to 185.24±3.78), and estradiol fell by 6.8 times (to 3.30±0.84). The swing movement at the end of the preparatory period caused a significantly (P ≥ 0.999) less increase in testosterone in stallions (up to 2.63±0.42) and mares (9.39±3.09) in contrast to the previous period. The cortisol content in stallions increased by 88% (to 381.5±17.3), in mares by 384% (to 711.80±47.50). Estradiol concentration decreased 10-fold in stallions (to 1.40±0.576; P ≥ 0.999), and 3.5-fold (to 6.94±0.829; P ≥ 0.999) in mares. Conclusion: the training is sufficient for adaptation of stallions to the racetrack. For mares, the duration of the preparatory training is not sufficient.

Biomechanical Correlation Between Trunk and Foot Kinematics During Golf Swing Movement Before and After Fatigue

BackgroundKinematic chain of whole body is important during golf swing. Moreover, it was suggested that kinematics of golf swing was affected by fatigue. The purpose of the present study was to investigate the golf swing before and after fatigue of trunk muscles, and to assess the effect of the fatigue on kinematics of trunk as well as lower extremity. A total of 11 healthy adults participated in the current study. Golf swing motion in each subject was measured with a 7-iron on a grass plate using motion capture system. Three-dimensional kinematics of trunk and lower extremity on the lead side were evaluated.ResultsSagittal trunk instability was observed after fatigue. Regarding the kinematic chain, range of motion of trunk rotation (r = -0.76, p < 0.01) and knee rotation (r = 0.82, p < 0.01) were significantly correlated with the hindfoot rotation before the fatigue task. However, after the fatigue task, the hindfoot rotation was significantly correlated only with the knee rotation (r = 0.76, p <0.01). ConclusionsAs fatigue of trunk muscles will alter swing movement and kinematic chain, trunk muscle training can be one of key strategies to maintain swing performance. Trial registrationOur study was registered to UMIN (No. 000037037, date; 01/07/2019).

Elastic kirigami patch for electromyographic analysis of the palm muscle during baseball pitching

Surface electromyography (sEMG) is widely used to analyze human movements, including athletic performance. For baseball pitchers, a very precise movement is required to pitch the ball into the strike zone. The palm muscles appear to play a key role in this movement, and a real-time recording of sEMG from the palm muscle is useful in the analysis of motion during baseball pitching. However, the currently available devices with rigid and bulky electrodes (including connective wires) impede natural movements of the wearer and recording of sEMG from the palm muscles during vigorous action. Here, we describe a skin-contact patch consisting of kirigami-based stretchable wirings and conductive polymer nanosheet-based ultraconformable bioelectrodes, which address the challenge of mechanical mismatch between human skin and electrical devices. The key strategy is a kirigami-inspired wiring design and a mechanical gradient structure from nanosheet-based flexible bioelectrodes to a bulk wearable device. This approach would buffer the mechanical stress applied to the skin-contact bioelectrodes during an arm swing movement. With this patch, we precisely measure sEMG at the abductor pollicis brevis muscle (APBM) in a baseball player during ball pitching. We observe differences in the activity of the APBM between different types of pitches—fastball and curveball. This sEMG measurement system will enable the analysis of motion in unexplored muscle areas, such as on the palm and the sole, leading to a deeper understanding of muscular activity during performance in a wide range of sports and other movements.

Analysis of hazards associated with injuries to the employee’s head during fall arrest

A fall from a height is one of the most serious hazards faced by employees in the work environment. It is present mostly at workstations in such industries as construction, power engineering, mining, storage, etc. Using individual protective equipment against falls from a height is a basic method of protecting workers under such conditions. The choice of this method carries specific risks associated with the functioning of equipment during fall arrest. Hitting elements of the workstation during fall arrest associated with pendulum movement is a very serious threat. This paper presents conditions which trigger pendulum movement during fall arrest and the positions which a human equipped with a full body harness can assume then. Potential effects of the impact of the head against an obstacle during pendulum movement are discussed on the basis of the results of research with an anthropomorphic dummy. The article discusses methods of preventing swing movement and ways of mitigating the effects of collisions with obstacles within the workstation. It also presents the basic requirements for protective helmets intended for use with individual protection equipment against falls from a height.

Design of a Flapping Wing Mechanism to Coordinate Both Wing Swing and Wing Pitch

This paper presents a design procedure to achieve a flapping wing mechanism for a micro-air vehicle that coordinates both the wing swing and wing pitch with one actuator. The mechanism combines a planar four-bar linkage with a spatial four-bar linkage attached to the input and output links forming a six-bar linkage. The planar four-bar linkage was designed to control the wing swing trajectory profile and the spatial four-bar linkage was designed to coordinate the pitch of the wing to the swing movement. Tolerance zones were specified around the accuracy points, which were then sampled to generate a number of design candidates. The result was 29 designs that achieve the desired coordination of wing swing and pitch, and a prototype was constructed.