复杂度在立位期间心率变异分析中的应用

目的 介绍非线性指标复杂度,并将之应用于心率变异分析。分析立位测试过程中心血管系统复杂性的变化。方法 对8名被试者进行立位耐力测试。记录心电信号并用复杂度进行心率变异分析。结果 与立位前平卧位相比,立位0-5min,5-10min,10-15min和15-20min心脏R-R间期,R-R间期标准差和相临R-R间期差值的标准差（RMSSD）显著降低。立位0-5min,15-20min复杂度和近似熵显著低于平卧位。结论 立位期间心率变异降低。心血管系统复杂性降低。复杂度应用于心率变异的分析是可行的。     

有氧锻炼前后立位应激下血压变异性的比较

目的阐明下体负压（ＬＢＮＰ）作用下血压变异性的特征，以及有氧锻炼是否对其有一定影响。方法用常规ＡＲ谱、时变ＡＲ谱、粗粒化谱分析（ＣＧＳＡ）及近似熵（ＡｐＥｎ）四种方法，分析六个月有氧锻炼前、后大学生在两种ＬＢＮＰ作用下的收缩压变异性（ＳＢＰＶ），并与一组中、长跑运动员的结果进行横向比较。结果ＬＢＮＰ作用时，ＳＢＰＶ信号谐波成份的总功率及低频段（ＬＦ）功率增大，分形成份的谱指数（无显著变化，而ＡｐＥｎ则呈持续升高变化。有氧锻炼后，ＬＢＮＰ作用下各种ＳＢＰＶ指标的响应变化较锻炼前并无显著差别。大学生组与运动员组之间亦无显著差别。结论ＳＢＰＶ信号与心率变异性（ＨＲＶ）迥然不同：ＬＢＮＰ作用下，ＳＢＰＶ的ＬＦ成份被进一步激活，信号的复杂度显著升高；但ＳＢＰＶ信号的这种特征性变化并不受有氧锻炼的影响。     

Mounting and calibration of stairs on piezoelectric force platforms

To calculate the centre of pressure using piezoelectric force plates mounted on pads, no net tensile stresses may be imposed on the surface of the plate. This condition is violated when stairs are attached to the plates, unless the plates are preloaded. Typical shear forces encountered when climbing stairs were used to determine required preloads of approximately 16.4 N/cm step height. Vertical and horizontal loads were applied at known locations on the steps, and points of application were calculated. Deviations were within ± 3 mm. The effect of point of application inaccuracy on calculated joint moments is considerable. A 2 cm medial shift in the point of application resulted in calculated peak knee abduction/adduction moment errors of 35%.     

Pre‐performance psychological states and performance in an elite climbing competition

The purpose of the present study was to assess the relationship between pre‐performance psychological states and expert performance in non‐traditional sport competition. Nineteen elite male sport climbers (M=24.6, SD=4.0 years of age) completed the Competitive State Anxiety Inventory‐2 and the Positive and Negative Affect Schedule before an international rock climbing competition. Climbing performances were video‐recorded to calculate movement fluency (entropy) and obtain ascent times. Official route scores were also obtained. Successful climbers reported higher pre‐performance levels of somatic anxiety and climbed the most difficult part of the route more slowly than their unsuccessful counterparts. The psychological states preceding elite climbing competition appeared to be an important factor in determining success, even when differences in baseline ability were taken into account.     

A biomechanical study of equilibrium in sport rock climbing

One of the main objectives of the experiment reported in this article was to analyze the arrangement of the forces applied to the holds accompanying a voluntary right foot release in the hanging rock climber. The three dimensional reaction forces applied to the holds were measured using four holds equipped with strain gauges. The force arrangement after the release consisted of a tripedal stance on the three remaining holds for the vertical forces, and of a bipedal stance on two laterally opposite holds (left foot and left holds) for the horizontal forces. The general significance of the results was analyzed with respect to the mechanism of static equilibrium. However, before conclusions can be drawn, other climbing movements and positions must be analyzed.     

心率变异分析方法的研究进展

心率变异性（HRV）是当前心电图分析的一个前沿热点。目前HRV信号的分析法主要是线性分析法,非线性分析法则不多。本文综述了国内外心率变异分析方法的研究进展。重点分析了非线性分析方法的原理和特点,探讨了HRV信号的分形维数,复杂度和近似熵分析法。     

正加速度作用下心率变异性的非线性动力学分析

目的揭示心率变异性在＋ＧＺ作用下的变化规律，用于高性能战斗机飞行员的选拔。方法对３１名飞行员离心机加速度试验中安静状态、２．５Ｇ和３．５Ｇ时的心率变异性数据进行了复杂度、分形维数和近似熵的非线性动力学分析。结果随着＋ＧＺ作用增加，受试者心率变异性的复杂度、分形维数和近似熵都有不同程度的降低。进一步分析还发现，分解后的１／ｆ部分的分形维数变化量与基础Ｇ耐力呈正相关；非１／ｆ部分的复杂度和近似熵变化量与基础Ｇ耐力呈负相关。结论这些参数有可能作为衡量基础Ｇ耐力的指标。     

有氧锻炼前后立位应激下血压变异性的比较

目的 阐明下体负压（LBNP）作用下血压变异性的特征,以及有氧锻炼是否对其有一定影响。 方法 用常规AR谱、时变AR谱、粗粒化谱分析（CGSA）及近似熵（ApEn）四种方法,分析六个月有氧锻炼前、后大学生在两种LBNP作用下的收缩压变异性（SBPV）,并与一组中、长跑运动员的结果进行横向比较。 结果 LBNP作用时,SBPV信号谐波成份的总功率及低频段（LF）功率增大,分形成份的谱指数（无显著变化,而ApEn则呈持续升高变化。有氧锻炼后,LBNP作用下各种SBPV指标的响应变化较锻炼前并无显著差别。大学生组与运动员组之间亦无显著差别。 结论 SBPV信号与心率变异性（HRV）迥然不同：LBNP作用下,SBPV的LF成份被进一步激活,信号的复杂度显著升高;但SBPV信号的这种特征性变化并不受有氧锻炼的影响。     

熵指数对异氟烷麻醉中切皮体动反应的预测作用

目的研究熵指数(包括反应熵和状态熵)对异氟烷复合麻醉中切皮体动反应的预测作用并与双频谱指数(BIS)比较。方法ASAⅡ级择期腹部手术患者20例,按切皮有无体动反应分为体动组(9例)和非体动组(11例)。入室后常规监测,然后静注异丙酚、琥珀胆碱、芬太尼快诱导气管插管,持续吸入异氟烷,维持呼气末异氟烷浓度为1·3MAC,维持10min后开始手术,切皮前不用神经肌肉阻滞剂,如果发生体动,则按10%提高下一个患者异氟烷呼气末浓度,如果不动则按10%降低下一个患者异氟烷呼气末浓度。分别于入室、切皮前60s、30s、切皮后45s、120s对每例患者同时行熵指数和BIS监测。结果两组患者的熵指数值有显著性差异(P<0·05),而BIS无显著性差异(P>0·05)。反应熵和状态熵可以预测切皮体动,其预测概率(Pk)值分别为0·8937和0·8852,BIS不能预测切皮体动,Pk值是0·5919,熵指数和BIS的Pk值之间有显著性差异(P<0·05),Pk与反应熵和状态熵的Logistic回归方程分别为ln[Pk/(1-Pk)]=32·517-0·481x和ln[Pk/(1-Pk)]=28·728-0·438x。结论熵指数监测可以预测异氟烷麻醉中的切皮体动反应,值得临床推广应用。     

Postural stability during visual-based cognitive and motor dual-tasks after ACLR

ObjectivesDetermine the effect of visual-based motor and cognitive dual tasking on postural stability in those with anterior cruciate ligament reconstruction relative to matched controls.DesignCohort study.MethodsFourteen volunteers with history of anterior crucaite ligament reconstruction were matched with fourteen healthy controls. Participants performed single leg balance tasks under 4 conditions: (1) single leg balance with eyes-open, (2) single leg balance while catching a ball (dual-motor), (3) single leg balance while repeating a string of numbers in reverse order after viewing them (dual-cognitive) and (4) single leg balance with eyes-closed. Participants completed several patient-reported outcomes of knee function. Mixed effects models were used to identify group differences on the center of pressure measures of ellipse area and root-mean-squared excursion (medial–lateral and anterior–posterior). The mixed models included subject pair as a random factor and group (control, anterior cruciate liagement reconstruction), balance condition (eyes-open, eyes-closed, dual-cognitive, and dual-motor), and group*condition as fixed effects. Tukey post-hoc pairwise comparisons were performed for significant interaction and main effects with an α = 0.05.ResultsA significant group by condition interaction was observed for ellipse area and medial–lateral root-mean-squared excursion. The anterior cruciate ligament reconstruction group had higher ellipse area (p = 0.002, d = 0.44) and medial–lateral root-mean-squared excursion (p < 0.001, d = 0.49).ConclusionsPostural stability is greatly impaired under eyes-closed and dual-motor conditions relative to eyes-open. Anterior cruciate ligament reconstructed individuals have greater postural instability during the dual-cognitive condition that may indicate unique neural processing deficits remain following anterior cruciate ligament reconstruction.     

正加速度作用下心率变异性的非线性动力学分析

目的 揭示心率变异性在+G_z作用下的变化规律,用于高性能战斗机飞行员的选拔。方法 对31名飞行员离心机加速度试验中安静状态、2.5G和3.5G时的心率变异性数据进行了复杂度、分形维数和近似熵的非线性动力学分析。结果 随着+G_z作用增加,受试者心率变异性的复杂度、分形维数和近似熵都有不同程度的降低。进一步分析还发现,分解后的1/f部分的分形维数变化量与基础G耐力呈正相关;非1/f部分的复杂度和近似熵变化量与基础G耐力呈负相关。结论 这些参数有可能作为衡量基础G耐力的指标。     

有氧锻炼引起的心率动力学变化的近似熵分析

为研究有氧锻炼对心率动力学的影响，采用近似熵（ＡｐＥｎ，ａｐｐｒｏｘｉｍａｔｅｅｎｔｒｏｐｙ）方法对大学生有氧锻炼前、后及中长跑运动员的心率变异性（ＨＲＶ）信号进行了分析，并与相同条件下的时域分析及谱分析结果进行了比较。结果表明：６个月有氧锻炼引起大学生心率动力学一定改变，锻炼后在仰卧状态及ＬＢＮＰ作用下，其ＲＲ间期序列的ＡｐＥｎ值均较锻炼前显著降低（Ｐ＜０．０１，Ｐ＜０．０５）。中长跑运动员组在仰卧状态及ＬＢＮＰ作用初期，ＲＲ间期序列的ＡｐＥｎ值亦均显著低于大学生组有氧锻炼前的各相应值（Ｐ＜０．０１，Ｐ＜０．０５）。大学生组在－６．６７ｋＰａ／３０ｍｉｎＬＢＮＰ作用期间，ＨＲＶ信号的ＡｐＥｎ值均随作用时间呈线性持续降低变化（Ｐ＜０．０１）。但常规的时域及频域分析却不能区分出上述这些差别。结果提示：有氧锻炼可使ＨＲＶ信号的复杂度降低，而且在ＬＢＮＰ作用期间心率调节的同步化过程是持续进行的。