摘要
研究背景：在人体的运动过程中,产生的冲击振动波将沿着人体由下而上进行传递,由于不同个体之间身体素质的差异,下肢肌群力量会有所不同,对振动在人体中的传递也将产生相应的影响。
研究目的：通过下肢肌群力量不同的两组受试者,改变试验中的控制条件：负重、冲击波的强度和膝关节角度。探讨在不同的实验条件下冲击振动波在人体中的传递特点以及下肢肌群对冲击的反应。
研究方法：以16名受试者为研究对象,根据其下肢肌肉力量大小进行分组,分为运动组和普通组,各8名,受试者按规定姿势站立于振动台上,利用自制的角度计和杠铃,来控制姿态和负重大小,使膝关节角度维持在90°、120°、150°和180°,负重分别为0%BW、10%BW、20%BW和30%BW。利用DY-600-5振动台对受试者施加加速度为2g和4g(持续时间为20ms)的三角冲击振动波。按振动强度、负重大小和站立姿态参数组合,共有32组实验条件。在实验过程中,利用Endevco加速度传感器(采样频率为2000hz)采集振动台台面、外踝、膝关节中心和第四腰椎处的加速度垂直分量。利用Biovision公司的Dasylab肌电采集系统记录试验中胫骨前肌、腓肠肌、股内侧肌、股直肌、股外侧肌、股二头肌和臀大肌的表面肌电,利用角度计来测量在试验中膝关节的角度变化量。
结果：(1)在试验中从胫骨到第四腰椎之间的振动衰减量最大。在实验条件0kg4g90°、15kg4g120°、10kg4g90°下,振动在从膝关节中心到第四腰椎处的衰减量具有显著性(p<0.05).衰减量为55.7±6.08%和45.31±20.2%等。随着输入冲击的改变,振动的衰减会随着冲击的强度增加而增加,但是在5kg的时候,却是冲击越大,踝膝衰减越小。随着膝关节屈曲角度的增加,振动衰减也逐渐增加,但是在腰膝衰减上,衰减最大的是在是在膝关节角度为150°时,但是在膝踝衰减上,衰减最大的却是在膝关节90°。除了120°和150°时,在膝踝上衰减不具有显著性。其它的角度之间的腰膝衰减、膝踝衰减和台踝衰减三个部位上具有显著性的差异。
(2)在膝关节角度方面,随着重量的增加,膝关节角度变化有减小的趋势,并且在普通组,这种趋势比较明显。但是在两组内,均没有显著性的差异。随着膝关节角度的增大,在实验冲击过程中,膝关节角度变化逐渐增大,原因可能是,随着膝关节屈曲角度的增大,为了减小对躯干和头部的伤害,膝关节需要额外的屈曲来对振动进行衰减,除了150°和180°外,其他各组均具有显著性。冲击程度的不同对膝关节角度的变化具有非常显著性的差异。无论是普通组还是运动组,2g和4g均具有显著性差异,但是在两组之间,没有显著性差异,随着冲击的增加,为了增加对冲击振动的衰减作用,人体会通过增加膝关节的屈曲角度来进行衰减。
(3)在振动冲击峰值的时间延迟上,重量因素只有在0%BW和30%BW相比时,在腰膝时间延迟上具有显著性差异。膝关节角度的变化对时间延迟没有显著性影响。但是在膝关节角度150°时,时间延迟明显变短,两组之间具有显著性差异。表明在这种条件下,由于下肢肌肉工作用力,导致下肢刚度增加,传递速度加快。冲击强度因素只有在台踝时间延迟上具有显著性差异,在膝腰和踝膝时间延迟上有随着冲击的增加时间延迟逐渐增加的趋势,但是不具有显著性。
(4)在实验条件相同的条件下,两组之间的在股内侧肌、腓肠肌、股直肌积分肌电出现显著性差异。胫骨前肌方面,随着冲击的增加,胫骨前肌的活动增强,随着膝关节角度的增大,胫骨前肌的活动逐渐减弱。普通组受重量的影响比较大,具有显著性。而运动组在冲击和角度上具有显著性；腓肠肌方面,随着重量的增加,腓肠肌肌电活动逐渐增强,随着膝关节角度的增加,腓肠肌活动增强。
(5)股内侧肌、股外侧肌方面,随着膝关节角度的增加,股内侧、股外侧肌的活动明显减小,冲击越大,肌肉活动越明显,在相同的条件下,.普通组的肌电活动比运动组的肌电活动明显。而负重量级越大,肌电活动越强。股内侧肌在普通组和运动组,在角度因素上,具有明显的差异；股直肌方面,表现出随着重量、冲击和膝关节屈曲角度的增加,肌肉活动情况增加的趋势。但是,均不具有显著性差异；臀大肌、股二头肌方面,臀大肌和股二头肌均随着重量的增加活动加剧,主要是在维持关节的作用。
结论
(1)下肢肌群力量对振动的衰减量、时间延迟方面的影响,在同负荷下,下肢肌群力量较大的振动衰减较小,时间延迟较短。在冲击振动中,下肢肌群力量较大的膝关节变化量较小
(2)在试验中发现,下肢肌群力量较大的能较好的控制试验中的膝关节角度,随着负重、冲击的增加,在冲击过程中膝关节角度逐渐增加,增加振动的衰减量,减小加速度对上身的传递。
(3)冲击振动波在人体的自下而上的传递过程中,其加速度峰值随着距离的增加而逐渐衰减。它衰减量最大的部位是从外踝到第四腰椎的部位。因此,人体对冲击力衰减缓冲的主要关节是膝关节和髋关节,踝关节具有一定的缓冲衰减作用,但是不是非常明显。在外踝到第四腰椎的振动传衰减主要与膝关节的屈曲角度有关。膝关节的屈曲角度越大,振动的衰减量越大,振动的传递速度越快。
Background:During exercise in the human body, impact vibration waves generated along the body and on the next spread, due to physical differences between different individuals. Lower limb muscle strength will be different, the vibration transmission in the human body will also have Corresponding impact.
Purpose:Two groups whose lower limb muscle strength are different, through changing the test control conditions:load, impact wave magnitude and knee angles. In the different experimental conditions, to discuss the transmission characteristics of impact vibration in the human body and the lower limb muscles response to the impact vibration.
Methods:According to the experimental purposes, through reading the related literatures, there are 16 subjects for the study, eight of them are athletes, the others are ordinary people. The subjects upright stand on the surface of the vibrator, using the angle and the bar which is made by myself, to control the experimental conditions, the knee position maintained at 90°,120°,150°and 180°. They take the weight in 0% BW,10% BW,20% BW and 30% BW. DY-600-5 produce acceleration in 2 and 4,using shaking table speed of subjects produce 2g and 4g (duration 20ms) of the triangular wave shock and vibration. Experiment was divided into two groups, according to the experimental conditions change, a total of 32 conditions. During the experiment, using Endevco accelerometer (sampling frequency of 2000hz) shaking table collecting surface, the lateral malleolus, knee joint center and the fourth lumbar vertebra the vertical component of acceleration. Dasylab produced by Biovision acquisition system recorded test EMG tibialis anterior muscle, gastrocnemius, vastus medialis, rectus femoris, vastus lateralis, biceps femoris and gluteus maximus muscle surface, the angle meter to use measuring the angle of the knee in the experiment variation.
Results:(1) In the experiments, the largest vibration attenuation is from the tibia to the fourth lumbar spine. The In the experimental conditions 0kg4g90°,15kg4g120°, 10kg4g90°, The vibration attenuation from the knee center to the fourth lumbar vertebra is significant (p<0.05). Attenuation is 55.7±6.08% and 45.31±20.2% and so on. With the changes of the input impact vibration, vibration attenuation will increase, but when it come to 5kg, it is the biggest impact and the greater attenuation from the center of the knee to ankle. With the increase of knee flexion, vibration attenuation is gradually increased, but from the waist to the knee, the most greatest attenuation is when the knee angle 150°, but the knee-ankle-decay, the attenuation is the most powerful in the knee 90°. In addition to 120°and 150°,the knee-ankle-decay is not significant, the other departs of attenuation in the waist-knee attenuation, knee-ankle-attenuation and ankle-plate form attenuation were significant differences.
(2) From the knee angle, with the increase of weight, the knee angle tends to decrease. In the normal group, this trend is obviously. However between the two groups don't have significant differences. With the knee angle increasing in the impact experimental process, the knee angle movement increases, it is maybe with the knee flexion angle increases, to reduce the damage to the torso and head, people don't need to increase the knee flexion angle to attenuate the vibration. Except the 150°and 180°, the other groups in different angles are significant. The different magnitudes of impact have a very significant difference to the changes of the knee angle. Whether the ordinary group or the exercise group,2g and 4g are significant differences, but between the two groups, there is no significant difference, with increasing the impact magnitude, people will increase the knee flex angle to decrease the magnitude of vibration.
(3) In the delaying time of the peak vibration, the weight factor only has significant different when comparing the time delaying on the waist-knee between the 0% BW and 30% BW. There is no significant in time delayed when the knee angle changes. However, when the knee angle is 150°, the time delayed is obverse short. There is a significant different between the two groups. in these conditions, the force of the lower limb muscles changing, leading to lower extremity stiffness increases, the transmission speed up in it. The impact factor only has a significant differences on time delayed in ankle-plateform. in waist-knee and knee-ankle, there is a trends that the time delayed increases with the impact growing trend, but there is not a significant.
(4) In the same experimental conditions, there is a signifitient different between the two groups in the vastus medialis. Gastrocnemius and rectus femoris.the tibialis anterior muscle will have much activity when the impact increasing or the knee angle decreases. The normal group has a significant difference when the weight factor changes. The exercise group has a significant difference in the angle and impact; the gastrocnemius EMG activity will increased gradually when the increasing the weight or the knee angle increasing.
(5) Vastus medialis and vastus lateralis will increase activity when the knee angle decreasing or the bigger impact. The EMG activity of the normal group will exerse obviously under the same conditions, the EMG activity have a significant between the normal group and the exercise group. The weight bigger,the electromyographic activity stronger. Vastus medialis has a significant difference between the two groups; the rectus femoris shows a trend that with the weight, impact and knee flexion increase, the muscle activities rising. However, there is no significant difference; the gluteus maximus and biceps femoris activity will increase when the weight increasing, the main role in the maintenance of joints.
Conclusion:(1)Lower limb muscle strength influce to the vibration attenuation, time delayed,in the same conditions, the larger muscle strength,the more vibration attenuation, the shorter time delayed. In the impact vibration, the people whose lower limb muscle strength is large changes a small knee angle.
(2) In the experiments, the lower limb muscle strength can better control the knee angle, with the load and the impact increasing, the knee changing angle became bigger during the impact experiment, to increase the amount of vibration attenuation, Reducing the transmission of acceleration to the upper body.
(3) When the transmission process of vibration waves transmit from bottom to up in the human body, the peak acceleration of impact vibration gradually decreases with distance increasing. The largest part of its fading is from the lateral ankle to the fourth lumbar vertebra. Therefore, the major part of the human body which cushion the impact force is the knee joint and the hip joint, the ankle joint has a certain buffer attenuation, but it isn't very obverse. the vibration transmission from the lateral ankle to the fourth lumbar vertebrae is major related to knee flexion primarily. When the knee flexion angle increases, the vibration attenuation increasing and the vibration transmit fast in human body.
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