Voluntary drive-dependent changes in vastus lateralis motor unit firing rates during a sustained isometric contraction at 50% of maximum knee extension force

The purpose of the present study was to relate the expected inter-subject variability in voluntary drive of the knee extensor muscles during a sustained isometric contraction to the changes in firing rates of single motor units. Voluntary activation, as established with superimposed electrical stimulation was high (range: 91–99%, n=8) during a short maximal contraction, but was lower (range: 69–100%) in most subjects at the point of force failure during a sustained (49.1±10.1 s) fatiguing contraction at 50% of maximum force. On a different experimental day the firing behaviour of 27 single motor units was recorded with wire electrodes in the vastus lateralis muscle, 24 of which could be monitored from the time of recruitment to the point of force failure (53.6±9.8 s). Motor unit firing behaviour differed considerably among subjects. During the second half of the sustained, fatiguing contraction the changes in firing rate firing rate variability of early recruited units ranged from –10% to +100% and from –50% to +160% respectively among subjects. There were significant positive linear relations between voluntary activation, on the one hand, and rectified surface electromyogram (rsEMG, r=0.82), the changes in motor unit firing rate (r=0.49) and firing rate variability (r=0.50) towards the point of force failure on the other. The present data suggest that differences in voluntary drive that appear among subjects during fatigue may be an important determinant of motor unit firing behaviour.Abbreviations EMG electromyogram - ER unit early recruited unit - MFGC maximal force-generating capacity - MPF mean power frequency - MVC maximum voluntary contraction - NR unit newly recruited unit - rsEMG rectified surface electromyogram - SMUAP single motor unit action potential     

Effects of Creep and Cyclic Loading on the Mechanical Properties and Failure of Human Achilles Tendons

The Achilles tendon is one of the most frequently injured tendons in humans, and yet the mechanisms underlying its injury are not well understood. This study examines the ex vivo mechanical behavior of excised human Achilles tendons to elucidate the relationships between mechanical loading and Achilles tendon injury. Eighteen tendons underwent creep testing at constant stresses from 35 to 75 MPa. Another 25 tendons underwent sinusoidal cyclic loading at 1 Hz between a minimum stress of 10 MPa and maximum stresses of 30–80 MPa. For the creep specimens, there was no significant relationship between applied stress and time to failure, but time to failure decreased exponentially with increasing initial strain (strain when target stress is first reached) and decreasing failure strain. For the cyclically loaded specimens, secant modulus decreased and cyclic energy dissipation increased over time. Time and cycles to failure decreased exponentially with increasing applied stress, increasing initial strain (peak strain from first loading cycle), and decreasing failure strain. For both creep and cyclic loading, initial strain was the best predictor of time or cycles to failure, supporting the hypothesis that strain is the primary mechanical parameter governing tendon damage accumulation and injury. The cyclically loaded specimens failed faster than would be expected if only time-dependent damage occurred, suggesting that repetitive loading also contributes to Achilles tendon injuries. © 2003 Biomedical Engineering Society. PAC2003: 8719Rr     

Effects of active recovery on power output during repeated maximal sprint cycling

The effects of active recovery on metabolic and cardiorespiratory responses and power output were examined during repeated sprints. Male subjects (n = 13) performed two maximal 30-s cycle ergometer sprints, 4 min apart, on two separate occasions with either an active [cycling at 40 (1)% of maximal oxygen uptake; mean (SEM)] or passive recovery. Active recovery resulted in a significantly higher mean power output ( ) during sprint 2, compared with passive recovery [ ] 603 (17) W and 589 (15) W, P < 0.05]. This improvement was totally attributed to a 3.1 (1.0)% higher power generation during the initial 10 s of sprint 2 following the active recovery (P < 0.05), since power output during the last 20 s sprint 2 was the same after both recoveries. Despite the higher power output during sprint 2 after active recovery, no differences were observed between conditions in venous blood lactate and pH, but peak plasma ammonia was significantly higher in the active recovery condition [205 (23) vs 170 (20) μmol · 1⁻¹;P < 0.05]. No differences were found between active and passive recovery in terms of changes in plasma volume or arterial blood pressure throughout the test. However, heart rate between the two 30-s sprints and oxygen uptake during the second sprint were higher for the active compared with passive recovery [148 (3) vs 130 (4) beats · min⁻¹;P < 0.01) and 3.3 (0.1) vs 2.8 (0.1) 1 · min⁻¹;P < 0.01]. These data suggest that recovery of power output during repeated sprint exercise is enhanced when low-intensity exercise is performed between sprints. The beneficial effects of an active recovery are possibly mediated by an increased blood flow to the previously exercised muscle.     

多维分层反馈模式在医院内部质量评价中的应用效果

目的探讨多维分层反馈模式在医院内部质量评价中的应用效果。方法选择江苏省盐城市某三甲综合医院为样本医院,以职能部门、临床科室、医技科室共89个考核单元为研究对象,开展医院内部质量评价活动,应用多维分层理念建立质评反馈模式。结果应用多维分层反馈模式后,办公室、医务科、沟通办等职能部门月度质评现场管理成绩均有所提升（P＜0.05）;职能部门（台账资料）、临床医疗、医技科室及护理单元季度质评成绩均有所提高（P＜0.05）;危化品、不良事件、便携式血糖仪、知情同意及时间管理等专项质评追踪合格率均显著提高（P＜0.001）。结论将质评机制引入医院并形成科学化、常态化管理,是对外部评审的重要补充。而多维分层反馈模式的建立,有效地促进了部门、科室间的相互协作,提升了职能部门的管理成效,提高了医院整体的质量管理效能。     

Can the Multidimensional Prognostic Index Improve the Identification of Older Hospitalized Patients with COVID-19 Likely to Benefit from Mechanical Ventilation? An Observational,Prospective, Multicenter Study

ObjectiveData on prognostic tools for indicating mechanical ventilation in older people with COVID-19 are still limited. The aim of this research was to evaluate if the Multidimensional Prognostic Index (MPI), based on the Comprehensive Geriatric Assessment (CGA), may help physicians in identifying older hospitalized patients affected by COVID-19 who might benefit from mechanical ventilation.DesignLongitudinal, multicenter study.Settings and Participants502 older people hospitalized for COVID-19 in 10 European hospitals.MethodsMPI was calculated using 8 different domains typical of the CGA. A propensity score, Cox's regression analysis was used for assessing the impact of mechanical ventilation on rehospitalization/mortality for 90 days' follow-up, stratified by MPI = 0.50. The accuracy of MPI in predicting negative outcomes (ie, rehospitalization/mortality) was assessed using the area under the curve (AUC), and the discrimination with several indexes like the Net Reclassification Improvement (NRI) and the Integrated Discrimination Improvement (IDI).ResultsAmong 502 older people hospitalized for COVID-19 (mean age: 80 years), 152 were treated with mechanical ventilation. In the propensity score analysis, during the 90-day follow-up period, there were 44 rehospitalizations and 95 deaths. Mechanical ventilation in patients with MPI values ≥ 0.50, indicating frailer participants, was associated with a higher risk of rehospitalization/mortality (hazard ratio 1.56, 95% CI 1.09-2.23), whereas in participants with MPI values < 0.50 this association was not significant. The accuracy of the model including age, sex, respiratory parameters, and MPI was good (AUC = 0.783) as confirmed by an NRI of 0.2756 (P < .001) and an IDI of 0.1858 (P < .001), suggesting a good discrimination of the model in predicting negative outcomes.Conclusions and ImplicationsMPI could be useful for better individualizing older people hospitalized by COVID-19 who could benefit from mechanical ventilation.     

特种兵高强度训练后集训疲劳行为的观察与防护

目的：改善与防护某特种兵队员高强度集训疲劳。方法：匀衡膳食营养,服用自制抗疲I号,分析血中酶等及SCL－90分值变化。结果：防护后血中LDH,α－HBDH,CK,CK－MB等得到明显改善IP＜0．01,0．05）,3例过度训练综合征得到防治,SCL－90显示：躯体化症状,强迫症状,睡眠饮食等分值整体呈下降趋势（P＜0．05,0．01）。结论：服用1号食品可有效防护过度训练综合征的发生,改善大强度体能,野战条件下各种军事课目集训产生的躯体和心身疲劳。     

中枢性疲劳症候群临床与血清色氨酸的研究

目的：对珠海市中学生中枢性疲劳症候群的临床,患病率及与血清色氨酸的关系进行研究。方法：采用单纯随机抽样和整群一级抽样方法,对4年中学1594人进行问卷调查作为初筛,筛出有症状的部分人在医院进行以排除其它疾病为 的精查,并做血清色氨酸含量的测量,结果：临床表现自主神经症状,睡眠障碍,精神症状,推测珠海市中学生中患病率为11％,血清色氨酸含量较正常对照组低,两组有显著差异（P＜0．01）,结论：中枢性疲劳症候群是珠海地区中学生中的常见病,应积极于以防治;血中色氨酸含量的测定对诊断该疾病有一定的价值。     

"Fatigue on rest" and associated symptoms (headache, vertigo, blurred vision, nausea, tension and irritability) due to locally asymptomatic, unerupted, impacted teeth.

"Fatigue on Rest", headache, vertigo and the feeling of loss of balance, blurred vision, nausea, tension and irritability, were found to be prevalent amongst patients who had locally asymptomatic, unerupted impacted teeth. A comparative pressure sign was developed, which, when positive, confirmed the relationship between the impacted teeth and the medical symptoms. Removal of the impactions resulted in the alleviation of the symptoms. Stress and psychogenic factors are considered as trigger mechanisms, rather than as basic causes of the symptoms.     

中枢、神经—肌肉接头、肌肉疲劳的实验模型及其应用研究

目的：建立研究中枢、神经－肌肉接头和肌肉疲劳动物模型,为各种因素对运动性疲劳的影响及机制的研究,提供一种新的实验方法。方法：用铂金电极刺激蟾蜍脊髓,保护电极刺激坐骨神经干,直刺电极刺激腓肠肌,用MS302实验系统记录坐骨神经干的动作电位和腓肠肌的收缩曲线。观察丹参和生脉注射液对上述疲劳的影响。结果：中枢出现疲劳时间最短;神经－肌肉接头次之;肌肉出现疲劳时间最长。丹参和生脉注射液使中枢、神经－肌肉接头和肌肉出现疲劳时间都相应延长。结论：运动性疲劳首先发生在中枢,其次是神经－肌肉接头,最后是肌肉疲劳,丹参和生脉具有抗疲劳的作用。     

Prospective feasibility study of a mindfulness-based program for breast cancer patients in the southeastern US

BackgroundMindfulness interventions can improve psychological distress and quality of life (QoL) in cancer survivors. Few mindfulness programs for cancer recovery exist in Southeastern U.S. The primary objective of this study was to assess the feasibility of a modified mindfulness-based stress reduction (MBSR) program for breast cancer patients in Birmingham, Alabama. The secondary objective was to explore potential program effects on mindfulness skills and QoL.MethodsThis study was a prospective, quasi-experimental feasibility study conducted over 10 months at a university hospital. Feasibility was achieved if 80% of eligible patients screened enrolled in the study and 70% of enrolled patients attended all 8 program sessions. Effectiveness was estimated by changes in mindfulness and QoL indicators measured with validated scales administered at 3 time points and assessed with a non-parametric Friedman test. Sessions included meditation, yoga, and an attention practice called body scan. There were 3 groups of 2–5 patients.ResultsThe sample totaled 12 patients. Forty-four percent (12/27) of eligible patients enrolled in the study, and two out of 12 enrolled patients completed 8 program sessions, resulting in 16.7% (2/12) retention. However, more than half (66.7%) of participants completed at least 7 sessions. Between baseline and 8-week follow-up, patients demonstrated statistically significant improvements in distress, general wellbeing, and fatigue-related QoL.ConclusionsFeasibility objectives were not achieved. However, a majority of participants (66.7%) completed 7 of 8 program sessions. Program effects were promising for distress, fatigue, and wellbeing. Results warrant further research on MBSR-like programs for breast cancer patients in Alabama.