Key transition technology of ski jumping based on inertial motion unit, kinematics and dynamics.

BACKGROUND: The development and innovation of biomechanical measurement methods provide a solution to the problems in ski jumping research. At present, research on ski jumping mostly focuses on the local technical characteristics of different phases, but studies on the technology transition process are less. OBJECTIVES: This study aims to evaluate a measurement system (i.e. the merging of 2D video recording, inertial measurement unit and wireless pressure insole) that can capture a wide range of sport performance and focus on the key transition technical characteristics. METHODS: The application validity of the Xsens motion capture system in ski jumping was verified under field conditions by comparing the lower limb joint angles of eight professional ski jumpers during the takeoff phase collected by different motion capture systems (Xsens and Simi high-speed camera). Subsequently, the key transition technical characteristics of eight ski jumpers were captured on the basis of the aforementioned measurement system. RESULTS: Validation results indicated that the joint angle point-by-point curve during the takeoff phase was highly correlated and had excellent agreement (0.966 ≤ r ≤ 0.998, P < 0.001). Joint root-mean-square error (RMSE) differences between model calculations were 5.967° for hip, 6.856° for knee and 4.009° for ankle. CONCLUSIONS: Compared with 2D video recording, the Xsens system shows excellent agreement to ski jumping. Furthermore, the established measurement system can effectively capture the key transition technical characteristics of athletes, particularly in the dynamic changes of straight turn into arc in inrun, the adjustment of body posture and ski movement during early flight and landing preparation.

Reasons and promotion strategies of physical activity constraints in obese/overweight children and adolescents.

To explore the reasons for low levels of physical activity in obese/overweight children and adolescents and to propose appropriate strategies to promote their physical activity (PA). This review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines by searching and analyzing the literature of studies related to physical activity in obese/overweight children and adolescents published between January 2003 and January 2023 in Web of Science, Scopus, and PubMed databases. A total of 31 relevant studies were included for analysis, of which 16 were quantitative and 15 qualitative. According to these studies, the PA of obese/overweight children and adolescents is mainly constrained by negative factors: Individual, interpersonal, and environmental. Among these factors, low levels of individual motivation and psychological sensitivity and vulnerability, lack of family support, negative social feedback, insufficient protection from government policies, and inadequate support from the built environment are the main reasons that constrain their PA. The promotion of PA in obese/overweight children and adolescents, who are subject to more constraints at all levels, requires a system of security that involves the government, the community, the school, and the family to address the problems they encounter and enhance the sustainability of engagement in PA.

Comparative efficacy of various exercise interventions on depression in older adults with mild cognitive impairment: A systematic review and network meta-analysis.

BACKGROUND: Exercise is a promising nonpharmacological treatment for improving depression in older adults with MCI, but it is unclear which exercises are most effective. The objectives of this study were to compare and rank the effectiveness of various exercise interventions for depression in mild cognitive impairment (MCI) and to investigate the effects of exercise on depression. METHODS: The PRISMA-NMA guidelines were applied to the development and reporting of review criteria. The Cochrane Library, Web of Science, PsycINFO, PubMed, EMBASE, CINAHL, and Scopus databases were systematically searched by combining search terms for randomized controlled trial studies (RCTs) published in English from individual databases with the earliest available date set to March 10, 2023. Two evaluators independently selected and evaluated eligible studies of changes in depression in older adults with MCI after an exercise intervention. A protocol for this systematic review was registered in PROSPERO (Registration number: CRD42022377052). RESULTS: A network meta-analysis was conducted on 15 eligible RCTs consisting of 4271 subjects, including aerobic (n = 6), mind-body (n = 6) and multicomponent (n = 3) exercise trials. Compared to controls, mind-body exercise showed the strongest improvement in depressive symptoms (SMD = -0.63, 95% CI: -1.13, -0.14), followed by aerobic (SMD = -0.57, 95% CI: -0.88, -0.26) and multicomponent exercise (SMD = -0.53, 95% CI: -1.02, -0.03). Notably, there were no statistically significant differences between exercise types: aerobic vs. mind-body (SMD = 0.06, 95% PrI: -0.71, 0.84), multicomponent vs. mind-body (SMD = 0.11, 95% PrI: -0.75, 0.97), or multicomponent vs. aerobic (SMD = 0.04, 95% PrI: -0.771, 0.86). CONCLUSIONS: In this review, we found that mind-body exercise was most effective when compared to conventional controls and that multiple exercise modalities (aerobic, mind-body, and multicomponent exercise) had beneficial and comparable effects in reducing depressive states in older adults with MCI. These findings may guide clinical geriatric stakeholders and allied health professionals in providing more scientifically optimal exercise prescriptions for older adults with MCI. In the future, more high-quality, long-term clinical trials are needed to support the exploration of longer-term dynamic effects.

A Pulse Signal Preprocessing Method Based on the Chauvenet Criterion.

Pulse signals are widely used to evaluate the status of the human cardiovascular, respiratory, and circulatory systems. In the process of being collected, the signals are usually interfered by some factors, such as the spike noise and the poor-sensor-contact noise, which have severely affected the accuracy of the subsequent detection models. In recent years, some methods have been applied to processing the above noisy signals, such as dynamic time warping, empirical mode decomposition, autocorrelation, and cross-correlation. Effective as they are, those methods are complex and difficult to implement. It is also found that the noisy signals are tightly related to gross errors. The Chauvenet criterion, one of the gross error discrimination criterions, is highly efficient and widely applicable for being without the complex calculations like decomposition and reconstruction. Therefore, in this study, based on the Chauvenet criterion, a new pulse signal preprocessing method is proposed, in which adaptive thresholds are designed, respectively, to discriminate the abnormal signals caused by spike noise and poor-sensor-contact noise. 81 hours of pulse signals (with a sleep apnea annotated every 30 seconds and 9,720 segments in total) from the MIT-BIH Polysomnographic Database are used in the study, including 35 minutes of poor-sensor-contact noises and 25 minutes of spike noises. The proposed method was used to preprocess the pulse signals, in which 9,684 segments out of a total of 9,720 were correctly discriminated, and the accuracy of the method reached 99.63%. To quantitatively evaluate the noise removal effect, a simulation experiment is conducted to compare the Jaccard Similarity Coefficient (JSC) calculated before and after the noise removal, respectively, and the results show that the preprocessed signal obtains higher JSC, closer to the reference signal, which indicates that the proposed method can effectively improve the signal quality. In order to evaluate the method, three back-propagation (BP) sleep apnea detection models with the same network structure and parameters were established, respectively. Through comparing the recognition rate and the prediction rate of the models, higher rates were obtained by using the proposed method. To prove the efficiency, the comparison experiment between the proposed Chauvenet-based method and a Romanovsky-based method was conducted, and the execution time of the proposed method is much shorter than that of the Romanovsky method. The results suggest that the superiority in execution time of the Chauvenet-based method becomes more significant as the date size increases.