Biomechanics of walking with snowshoes

Snowshoeing is a popular form of winter recreation due to the development of lightweight snowshoes that provide flotation, traction, and stability. The purpose of this study was to determine the effects of snowshoes on lower extremity kinematics during level walking. Twelve adults (6 males, 6 females, body mass = 67.5 +/- 10.7kg) completed six 3-minute level walking trials. Subjects walked overground without snowshoes and on packed snow using conventional and flexible tail snowshoes. We placed lightweight inertial/gyroscopic sensors on the sacrum, thigh, shank, and foot. We recorded sensor orientation and calculated hip, knee, and ankle joint angles and angular velocities. Compared to level overground walking, subjects had greater hip and knee flexion during stance and greater hip flexion during swing while snowshoeing. Ankle plantarflexion began during late swing when snowshoeing vs. heel strike during overground walking. Lower extremity kinematics were similar across snowshoe frame designs during level walking. Our results show that snowshoeing on packed snow results in a more flexed leg compared to overground walking and may reflect a strategy to limit the effects of walking with an extended heel.     

Determining motions with an IMU during level walking and slope and stair walking

ABSTRACT

This study investigated whether using an inertial measurement unit (IMU) can identify different walking conditions, including level walking (LW), descent (DC) and ascent (AC) slope walking as well as downstairs (DS) and upstairs (US) walking. Thirty healthy participants performed walking under five conditions. The IMU was stabilised on the exterior of the left shoe. The data from IMU were used to establish a customised prediction model by cut point and a prediction model by using deep learning method. The accuracy of both prediction models was evaluated. The customised prediction model combining the angular velocity of dorsi–plantar flexion in the heel-strike (HS) and toe-off (TO) phases can distinctly determine real conditions during DC and AC slope, DS, and LW (accuracy: 86.7–96.7%) except for US walking (accuracy: 60.0%). The prediction model established by deep learning using the data of three-axis acceleration and three-axis gyroscopes can also distinctly identify DS, US, and LW with 90.2–90.7% accuracy and 84.8% and 82.4% accuracy for DC and AC slope walking, respectively. In conclusion, inertial measurement units can be used to identify walking patterns under different conditions such as slopes and stairs with customised prediction model and deep learning prediction model.     

Ski jumping boots limit effective take-off in ski jumping

In this study, we measured the vertical and horizontal take-off forces, plantar pressures and activation patterns of four muscles (vastus lateralis, gluteus maximus, tibialis anterior, gastrocnemius) in 10 ski jumpers in simulated laboratory conditions when wearing either training shoes or ski jumping boots. We found significant differences in vertical ( P ? 0.001), horizontal ( P ? 0.05) and resultant ( P ? 0.001) take-off velocities and vertical force impulse ( P ? 0.01). We found no significant differences in the jumpers' initial take-off positions; however, the jumping boots condition resulted in a smaller displacement in the final position of the following joint angles: ankle angle ( P ? 0.001), knee angle ( P ? 0.001), hip angle ( P ? 0.01) and shank angle relative to the horizontal ( P ? 0.01). This corresponds with less electromyographic activity during take-off in both the gastrocnemius (300 to 200 ms and 200 to 100 ms before take-off) and gluteus maximus (300 to 200 ms and 100 to 0 ms before take-off). During the early take-off in the jumping boots condition, significantly more pressure was recorded under the heel ( P ? 0.001), whereas the forefoot was more highly loaded at the end of the take-off. Differences in take-off velocity (representing the final output of the take-off) can be accounted for in the main by the different use of plantar flexion, emphasizing the role of the knee and hip extensors when wearing jumping boots. We conclude that the stiffness of the structure of the jumping boots may result in a forward shift of pressure, thus limiting the effective vertical force. To avoid this pressure shift, the pattern of movement of simulated take-offs should be carefully controlled, particularly when wearing training shoes.     

Ski jumping boots limit effective take-off in ski jumping

In this study, we measured the vertical and horizontal take-off forces, plantar pressures and activation patterns of four muscles (vastus lateralis, gluteus maximus, tibialis anterior, gastrocnemius) in 10 ski jumpers in simulated laboratory conditions when wearing either training shoes or ski jumping boots. We found significant differences in vertical (P < 0.001), horizontal (P < 0.05) and resultant (P < 0.001) take-off velocities and vertical force impulse (P < 0.01). We found no significant differences in the jumpers' initial take-off positions; however, the jumping boots condition resulted in a smaller displacement in the final position of the following joint angles: ankle angle (P < 0.001), knee angle (P < 0.001), hip angle (P < 0.01) and shank angle relative to the horizontal (P < 0.01). This corresponds with less electromyographic activity during take-off in both the gastrocnemius (300 to 200 ms and 200 to 100 ms before take-off) and gluteus maximus (300 to 200 ms and 100 to 0 ms before take-off). During the early take-off in the jumping boots condition, significantly more pressure was recorded under the heel (P < 0.001), whereas the forefoot was more highly loaded at the end of the take-off. Differences in take-off velocity (representing the final output of the take-off) can be accounted for in the main by the different use of plantar flexion, emphasizing the role of the knee and hip extensors when wearing jumping boots. We conclude that the stiffness of the structure of the jumping boots may result in a forward shift of pressure, thus limiting the effective vertical force. To avoid this pressure shift, the pattern of movement of simulated take-offs should be carefully controlled, particularly when wearing training shoes.     

原地摆臂纵跳和抱头纵跳动力学特征的比较

运用三维测力台(Kistler)和红外光点自动捕捉测试系统(Qualisys-MCU500)对北京体育大学男子排球队9名运动员分别进行了摆臂纵跳和抱头纵跳的测试,结果表明:摆臂纵跳蹬伸过程中最大力值大于抱头纵跳,但是由于蹬伸后半段时间的延长使后半段蹬伸力的梯度值没有明显增加;落地时地面最大冲击力与纵跳高度无关;摆臂纵跳的冲量值大于抱头纵跳,但研究结果发现纵跳高度与冲量并没有显著性相关关系.     

短跑着地缓冲的运动生物力学分析

对短跑的动力来源问题、缓冲时相问题、缓冲距离问题等关键性的特点问题进行探讨与分析,从生物力学的角度短跑着地缓冲的动作进行分析,并探究了影响着地缓冲的若干因素,以期完善人们对该动作的认识,服务训练。     

现代科学技术与运动生物力学发展

笔者论述了现代科学技术对运动生物力学形成和发展的作用。人们思维方式的更新 ,认识事物能力水平提高 ,各学科知识相互交叉渗透 ,使运动生物从生物力学中分离出来 ,形成了一独立学科。现代科学技术的发展不断丰富、完善运动生物力学理论 ;电子技术、计算机、新材料技术的出现为运动生物力学实验研究提供了新的研究方法和测试手段。现代科学技术将与运动生物力学发展更加紧密结合 ,进一步拓展运动生物力学应用研究领域。     

运动生物力学教学改革与创新

在当前教育改革的背景下,根据体育教育所提出的对生物力学的教学安排,通过对生物力学的学习,能够使学生科学的进行体育教学。对于当前的运动生物力学教育还存在着很多的问题,本文通过文献资料法、逻辑分析法对目前各高校对生物力学的教学情况以及改革和创新状况进行分析,发现大部分学校呈现出教学方式单一、教学思维固化、教学环境与硬件落后等现象,因此针对此现象,提出了采用多方面教学方式对教师教学模式进行改革,建设相应的运动生物力学实验室等建议。     

Part I: Biomechanics

The purpose of this study was to determine whether the sequence of strength training before endurance training (ST/ET) is more or less effective than endurance training followed by strength training (ET/ST). Twenty‐three females and 11 males were assigned to one of three groups: ST/ET (n= 15), ET/ST (n= 15) or control (n = 4). The 7‐week training programme consisted of strength training using 10 exercises for two sets of 3–12 repetitions and running for 20–25 min at 60–90% of heart rate reserve. Maximal oxygen uptake (VO₂ max) was measured during a graded treadmill test, and muscular strength was assessed using one‐repetition maximum tests for the bench press (BP), shoulder press (SP), arm curl (AC) and leg press (LP). The VO₂ max significantly (P < 0.05) increased 6.7 and 6.2% for the ST/ET and ET/ST groups, respectively. There was no significant (P > 0.05) difference between the two experimental groups. Muscular strength significantly (P <0.05) improved by 15.2% (BP), 16.6% (SP), 17.2% (AC) and 11.9% (LP) for the ST/ET group and 19.9% (BP), 24.1% (SP), 20.9% (AC) and 14.0% (LP) for the ET/ST group. There were no significant (P > 0.05) differences between the two experimental groups for the BP, AC and LP; however, the ET/ST group increased (P < 0.05) SP strength more than the ST/ET group. In conclusion, adaptations to a combination of short‐term endurance and strength training as assessed by VO₂ max and BP, AC and LP strength appear to be independent of whether endurance training occurs prior to or following strength training.     

Biomechanics feedback for rowing

Factors that affect boat speed are important determinants of rowing performance and should form the basis of feedback to rowers and their coaches. Biomechanical analysis of rowing has led to variables that are causally linked to boat speed. With modern technology, these variables can be measured and feedback can be presented instantaneously on-water, or be presented simultaneously with video after the event. This paper demonstrates the links between the criterion of success in rowing, the time for completing 2000 m and the forces acting on the boat, and describes an instrumentation system for providing feedback of these variables to rowers and coaches. These feedback techniques have been used with rowers from national to Olympic competition standard. Aspects of technique have been linked to the determinants of boat speed and several examples are presented here. The motor learning literature supports the effectiveness of kinetic information feedback for the improvement of motor skill and provides a relevant conceptual framework for the improvement of rowing performance. However, although rowers and their coaches value this feedback, further research must be undertaken to establish a sound basis for comparing the effectiveness of such feedback compared with traditional styles, such as verbal feedback of performance.     

Biomechanics feedback for rowing

Factors that affect boat speed are important determinants of rowing performance and should form the basis of feedback to rowers and their coaches. Biomechanical analysis of rowing has led to variables that are causally linked to boat speed. With modern technology, these variables can be measured and feedback can be presented instantaneously on-water, or be presented simultaneously with video after the event. This paper demonstrates the links between the criterion of success in rowing, the time for completing 2000 m and the forces acting on the boat, and describes an instrumentation system for providing feedback of these variables to rowers and coaches. These feedback techniques have been used with rowers from national to Olympic competition standard. Aspects of technique have been linked to the determinants of boat speed and several examples are presented here. The motor learning literature supports the effectiveness of kinetic information feedback for the improvement of motor skill and provides a relevant conceptual framework for the improvement of rowing performance. However, although rowers and their coaches value this feedback, further research must be undertaken to establish a sound basis for comparing the effectiveness of such feedback compared with traditional styles, such as verbal feedback of performance.     

跳远踏跳教学阶段的生物力学分析

从生物力学的角度对跳远踏跳阶段的诸因素进行探讨，其中最主要的是：着板时制动点的稳定性，支撑腿踝膝关节的锁紧程度，摆动动作的效果以及蹬伸过程肌肉发力的顺序等因素，为科学制定教学计划提供了一定的理论依据。     

Perceived exertion and physiological economy of competition walking, ordinary walking and running

Four competition walkers performed competition walking, ordinary walking and running on a treadmill on two different occasions. During the two walking modes, the subjects performed maximal tests. During running, the session was terminated at a heart rate of 150 beats min-1 or an exertion rating--for either chest or leg--of 5 or higher. The tests commenced at 2.5 km h-1 and the velocity was increased by 2.5 km h-1 every 4 min. Measures of chest exertion and breathlessness, leg exertion, heart rate and blood lactate were taken every 4 min just prior to the velocity changes. The measured psychological and physiological variables were described by monotonously accelerating power functions with exponents around 2 for the perceptual variables at both walking modes. The heart rate growth for competition walking accelerated according to a function with an exponent of 1.7, which is lower than that for ordinary walking (2.0), but higher than that for running which is linear. No significant difference was found between maximal oxygen uptake when competition walking and running were compared. A second test was carried out so as to confirm the cross-over point for the heart rate curves in the two walking modes. The cross-over point for the two walking curves were determined to be at 8.6 km h-1.     

运动生物力学研究进展与展望

本文论述了运动生物力学的发展历程、研究现状和理论基础，认为运动生物力学的基础理论是：生物力学、生理学和机能解剖学。基本方法是：物理学方法、生物学方法和系统分析方法。基本技术是：电子技术、计算机技术和测量技术。展望前景．运动生物力学仍将是多学科合作，并在下列领域获得进展：①经典力学分析；②力学模型研究；③运动技术最佳化；④人体运动仿真；⑤肌肉力学研究；⑥面向全民健身的生物力学研究；⑦技术分析专家系统的研究。     

Perform kicking with or without jumping: joint coordination and kinetic differences between Taekwondo back kicks and jumping back kicks

We investigated joint coordination differences between Taekwondo back kicks and jumping back kicks, and how jumping (in performing the latter) would alter engaging ground reaction forces (GRF) in executing kicking. Ten skilful athletes volunteered to perform both kinds of kicking within the shortest time for three successful trials. Three high-speed cameras and two force platforms were used for data collection, and the trial with the shortest execution time was selected for analysis. Movements were divided into the rotation and attack phases. With comparable execution time and maximum joint linear/angular speeds, back kicks and jumping back kicks differ mainly in larger GRF in the latter, and in greater target acceleration in the former probably because the support leg prevented athletes’ rebounding after impact. In addition, more prominent antiphase and in-phase coordination between the shoulder segment and knee joint, and elongated rotation phase were found in jumping back kicks. Larger GRF values in jumping back kicks were generated for jump take-off rather than for a more powerful attack. In back kicks although the support leg remained ground contact, greatly decreased GRF in the attack phase suggested that the support leg mainly served as a rotation axis.     

运动生物力学在艺术体操运动中的应用与展望

根据艺术体操运动专项运动生物力学研究的现状、运动生物力学学科发展趋势以及艺术体操运动发展的实际需求,对运动生物力学在艺术体探运动中的应用的研究领域和研究方法的发展趋势进行展望。运用多种运动生物力学的理论力学和实验研究相结合的方法,对艺术体操运动中的多个领域进行分析和研究,是运动生物力学在艺术体操运动项目中的研究发展趋势,以期为运动生物力学如何更好地结合艺术体操专项特点为艺术体操运动实战服务提供借鉴。     

女子撑竿跳高的生物力学

通过分析女子撑竿跳高一些较为普遍的技术动作来描述女子撑竿跳高的生物力学, 以便帮助教练员、运动员更好地理解此项运动的动作技术, 使教练员能更好地鉴别动作技术的错误, 然后快速作出适当的校正。     

运动生物力学标准化问题的探讨

标准化工作是目前运动生物力学学科相对滞后的一项工作,探讨了运动生物力学标准化工作的意义及内容,并列举了2个实例,目的是引起学术界对标准化问题的关注与重视。