Gait stability,variability and complexity on inclined surfaces

This study evaluated the gait stability, variability, and complexity of healthy young adults on inclined surfaces. A total of 49 individuals walked on a treadmill at their preferred speed for 4 min at inclinations of 6%, 8%, and 10% in upward (UP) and downward (DOWN) conditions, and in horizontal (0%) condition. Gait variability was assessed using average standard deviation trunk acceleration between strides (VAR), gait stability was assessed using margin of stability (MoS) and maximum Lyapunov exponent (λs), and gait complexity was assessed using sample entropy (SEn). Trunk variability (VAR) increased in the medial-lateral (ML), anterior-posterior, and vertical directions for all inclined conditions. The SEn values indicated that movement complexity decreased almost linearly from DOWN to UP conditions, reflecting changes in gait pattern with longer and slower steps as inclination increased. The DOWN conditions were associated with the highest variability and lowest stability in the MoS ML, but not in λs. Stability was lower in UP conditions, which exhibited the largest λs values. The overall results support the hypothesis that inclined surfaces decrease gait stability and alter gait variability, particularly in UP conditions.     

Investigation of balance strategy over gait cycle based on margin of stability

This study was conducted to investigate the balance strategy of healthy young adults through a gait cycle using the margin of stability (MoS). Thirty healthy young adults participated in this study. Each performed walking five times at a preferred speed and at a fast speed. The MoS was calculated over a gait cycle by defining the base of support (BoS) changes during a gait cycle. The MoS was divided into medial/lateral and anterior/posterior components (ML MoS and AP MoS). The central values and the values at 12 gait events of the MoS were compared. Positive/negative integration of ML MoS (ML MoS_POS and ML MoS_NEG, respectively) and the average ML/AP MoS over a cycle (ML/AP MoS_mean) were significantly lower at a fast gait than at a preferred gait. ML/AP MoS were lower at a fast speed than at the preferred speed, except for the ML MoS immediately before left heel strike (pre left HS) and right and left heel strike (HS). ML/AP MoS were significantly lower immediately before heel strike (pre-HS) than in other gait events, regardless of walking speed. It was suggested that pre-HS is the most unstable moment in both ML/AP directions and a crucial moment in control of gait stability. The results presented above might be applicable as basic data regarding dynamic stability of healthy young adults through a gait cycle for comparisons with elderly people and patients with orthopedic disorders or neurological disorders.     

Influence of gait speed on the control of mediolateral dynamic stability during gait initiation

This study investigated the influence of gait speed on the control of mediolateral dynamic stability during gait initiation. Thirteen healthy young adults initiated gait at three self-selected speeds: Slow, Normal and Fast. The results indicated that the duration of anticipatory postural adjustments (APA) decreased from Slow to Fast, i.e. the time allocated to propel the centre of mass (COM) towards the stance-leg side was shortened. Likely as an attempt at compensation, the peak of the anticipatory centre of pressure (COP) shift increased. However, COP compensation was not fully efficient since the results indicated that the mediolateral COM shift towards the stance-leg side at swing foot-off decreased with gait speed. Consequently, the COM shift towards the swing-leg side at swing heel-contact increased from Slow to Fast, indicating that the mediolateral COM fall during step execution increased as gait speed rose. However, this increased COM fall was compensated by greater step width so that the margin of stability (the distance between the base-of-support boundary and the mediolateral component of the “extrapolated centre of mass”) at heel-contact remained unchanged across the speed conditions. Furthermore, a positive correlation between the mediolateral extrapolated COM position at heel-contact and step width was found, indicating that the greater the mediolateral COM fall, the greater the step width. Globally, these results suggest that mediolateral APA and step width are modulated with gait speed so as to maintain equivalent mediolateral dynamical stability at the time of swing heel-contact.     

年轻健康正常人单次精准功率运动前后脉搏波波形特征个体化分析研究*

目的: 观察研究年轻健康正常人的静息桡动脉脉搏波特征及单次个体化运动后脉搏波的变化情况。方法: 选取阜外医院年轻健康、无任何疾病诊断的正常人16例,首先完成症状限制性极限心肺运动试验（CPET）,根据CPET计算Δ50%功率为个体化精准运动强度,完成持续30 min的单次运动。于运动前和运动后10 min、20 min、30 min分别测量50 s桡动脉脉搏波,先用软件自动定点再人工复检得到每个脉搏波特征点：起始点（B）、主波波峰点（P1）、重搏波波谷点（PL）、重搏波波峰点（P2）、结束点（E）,从仪器中导出各点对应的横坐标（时间T）和纵坐标（幅值Y）的原始数据,将上一个脉搏波的结束点E视为下一个波的起始点B,TB归零,得到主要观察指标：YB、YP1、YPL、YP2及TP1、TPL、TP2、TE,并计算出ΔYP1（YP1-YB）、ΔYPL（YPL-YB）、ΔYP2（YP2-YB）,TE-TPL、（TE-TPL）/TPL、脉率,S1（主波升支斜率）、S2（重搏波升支斜率）,ΔYP2-ΔYPL、TP2-TPL作为次要观察指标;定义波峰明显的重搏波为YP2>YPL,计算波峰明显的重搏波出现率（50 s内YP2>YPL的波形个数/波形总个数×100%）;对每位患者运动前后的50 s脉搏波数据个体化分析,再将所有数据求均值进行整体分析。结果: ①16例年轻健康受试者（男10女6）,年龄（30.6±6.4,24~48）岁;身高（170.4±8.2, 160~188）cm;体质量（63.9±12.8, 43~87）kg。②静息时YB（87.2±5.8,78.1~95.9）、YP1（223.5±15.8,192.7~242.3）、YPL（122.8±7.8,110.0~133.8）、YP2（131.4±4.9,116.7~137.5）、TP1（126.2±42.2,94.2~280.0）、TPL（360.2±44.8,311.5~507.3）、TP2（432.4±50.8,376.2~589.0）、TE（899.7±86.9,728.3~1042.0）;ΔYP1（136.3±19.9,96.8~158.6）、ΔYPL（35.7±10.7,16.0~55.7）、ΔYP2（44.3±8.1,22.5~56.5）、TE-TPL（539.5±79.3,405.9~691.3）、（TE-TPL）/TPL（1.5±0.3,0.8~2.0）、脉率（67.3±6.6,57.6~82.4）、S1（1.1±0.2,0.6~1.4）、S2（0.1±0.1,0.0~0.2）、ΔYP2-ΔYPL（8.6±6.1,0.9 ~19.8）、TP2-TPL（72.3±19.9,38.3~108.4）。③运动后10 min, YPL（97.0±13.2比122.8±7.8）、YP2（109.6±12.8比131.4±4.9）、ΔYPL（6.6±9.8比35.7±10.7）、ΔYP2（19.3±11.2比44.3±8.1）显著减小,TE（667.8±123.1比899.7±86.9）、TE-TPL（330.2±128.4比539.5±79.3）、（TE-TPL）/TPL（1.0±0.4比1.5±0.3）显著减小,而脉率（92.2±14.0比67.3±6.6）、ΔYP2-ΔYPL（12.7±9.7比8.6±6.1）、 TP2-TPL（98.0±38.1比72.3±19.9）显著增大（P均<0.05）。运动后20 min和30 min的脉搏波变化趋势与运动后10 min保持一致,但从20 min开始大部分指标逐渐向运动前静息水平恢复。④静息时16例正常人波峰明显的重搏波出现率为94.5%,运动后10 min（96.3%）、20 min（98.5%）、30 min（99.8%）的出现率升高（P均<0.01）。其中10例运动前后波峰明显的重搏波出现率均维持在100%左右;2例运动前出现率已达100%,但运动后10 min有所降低,后又继续升高,30 min时恢复到100%;3例静息出现率偏低,运动后升高近100%;还有1例仅运动后20 min出现率偏低,考虑人为因素影响。结论: 运动对正常人脉搏波的影响主要体现在重搏波上;整体上看,单次精准功率运动后,重搏波位置降低、幅度加深,波峰明显的重搏波出现率普遍提高,且这种改变至少能维持30 min;从个体上看,每位受试者的反应又有所不同。     

Active recovery has a positive and acute effect on recovery from fatigue induced by repeated maximal voluntary contractions of the plantar flexors

This study investigated the acute effect of active recovery (AR) following fatigue induced by 80 three-second maximal voluntary isometric plantar flexion contractions (MVICs) in 12 young men. AR consisted of a total of 180 voluntary isometric ramp contractions of the plantar flexors (0.75-s contraction/relaxation) targeting 10% of MVIC torque. MVIC torque, voluntary activation and root mean square values of electromyographic signals for the triceps surae normalized by each peak-to-peak amplitude of compound motor action potential were determined before, and immediately, 10, 20 and 30 min after the fatiguing task. Evoked torques were similarly assessed except for immediately after it. The AR and passive recovery were randomly performed on two days by each participant between 5 min and 10 min after the fatiguing task. For all the parameters other than MVIC torque, there was no significant difference between the conditions at any time point. MVIC torque decreased significantly immediately after the fatiguing task regardless of condition (P < 0.05), and the corresponding decrease in MVIC torque recovered 30 min after the fatiguing task only in AR (P < 0.05). These results suggest an acute positive effect of AR on recovery of neuromuscular function and/or contractile properties after fatigue.     

虾青素复合有氧运动对D-半乳糖诱导大鼠肾脏衰老的干预作用及其机制

目的:研究虾青素复合有氧运动对D-半乳糖诱导大鼠肾脏衰老的干预作用及其机制.方法:60只3月龄SPF级SD大鼠采用两因素两水平2×2析因设计随机分为空白对照组(C组)、急性衰老组(S组)、虾青素+急性衰老组(AS组)、有氧运动+急性衰老组(ES组)、虾青素+有氧运动+急性衰老组(AES组),每组12只.大鼠腹腔注射10...     

Effects of suboccipital release with craniocervical flexion exercise on craniocervical alignment and extrinsic cervical muscle activity in subjects with forward head posture

BackgroundForward head posture is a head-on-trunk malalignment, which results in musculoskeletal dysfunction and neck pain. To improve forward head posture, both the craniocervical flexion exercise and the suboccipital release technique have been used. Objectives: The purpose of this study was to compare the immediate effects of craniocervical flexion exercise and suboccipital release combined with craniocervical flexion exercise on craniovertebral angle, cervical flexion and extension range of motion, and the muscle activities of the sternocleidomastoid, anterior scalene, and splenius capitis during craniocervical flexion exercise in subjects with forward head posture.MethodsIn total, 19 subjects (7 males, 12 females) with forward head posture were recruited using G-power software. Each subject performed craniocervical flexion exercise and suboccipital release combined with craniocervical flexion exercise in random order. After one intervention was performed, the subject took a 20 min wash out period to minimize any carry-over effect between interventions. Craniovertebral angle, cervical flexion and extension range of motion, and the muscle activities of the sternocleidomastoid, anterior scalene, and splenius capitis were measured. A one-way, repeated-measures ANOVA was used to assess differences between the effects of the craniocervical flexion exercise and suboccipital release combined with craniocervical flexion exercise interventions in the same group.ResultsCraniovertebral angle (p < 0.05), cervical flexion range of motion (p < 0.05), and cervical extension range of motion (p < 0.001) were significantly greater after suboccipital release combined with craniocervical flexion exercise compared to craniocervical flexion exercise alone. The muscle activities of the sternocleidomastoid, anterior scalene, and splenius capitis were significantly lower during suboccipital release combined with craniocervical flexion exercise than during craniocervical flexion exercise alone across all craniocervical flexion exercise phases except the first (all p < 0.05).ConclusionThe addition of suboccipital release to craniocervical flexion exercise provided superior benefits relative to craniocervical flexion exercise alone as an intervention for subjects with forward head posture.