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.     

Alterations in neuromuscular activation patterns associated with walking in short-leg walking boots

BackgroundShort-leg walking boots are a common intervention for acute and chronic lower extremity injury. Few studies have examined the neuromuscular adaptations associated with short-leg walking boots and no previous study has investigated timing characteristics of muscle activation during gait. The purpose of the current study was to examine the timing and amplitudes of muscle activation of the extrinsic ankle musculature during walking in two types of short-leg walking boots.MethodsEleven healthy young adults performed five level walking trials at a self-selected pace in each of three conditions: normal walking, Gait Walker and Equalizer short-leg walking boots. Ground reaction forces were collected from a force platform while surface electromyography (EMG) was collected from the tibialis anterior, peroneus longus and medial gastrocnemius. EMG signals were rectified and smoothed using the root mean squared with a 20-ms smoothing window and were normalized to the largest mean of the normal walking trials. A repeated measures analysis of variance was used to assess the effect of short-leg walking boots on the onset, duration and amplitude of muscle activation.ResultsShort-leg walking boots were generally associated with earlier onsets of muscle activation and longer durations of muscle activation. However, there was no reduction in EMG amplitude.ConclusionThe findings of this study show that the induced alterations in muscle activation patterns may limit the short-leg walking boots.     

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.     

Chronic participation in externally paced,but not self-paced sports is associated with the modulation of domain-general cognition

Abstract

The present study investigated the role of chronic sport participation in the modulation of vigilance and inhibitory control. We also aimed to disentangle the relative contribution of different types of sport expertise and sport-related fitness to the exercise-cognition relationship. Three groups of young adults differing in their chronic sport expertise (externally-paced sports, n?=?22, self-paced sports, n?=?22, non-athletes, n?=?22) took part in the study. Participants completed a cardiovascular fitness test, a hand-eye coordination test and two different types of vigilance tasks: (1) Psychomotor Vigilance Task (PVT) and (2) Oddball Task, which were designed to gain insight into the cognitive processes involved in sustaining attention over time and allocating selective attention by exerting inhibitory control, respectively. No differences were found in PVT performance between the two athlete groups and between self-paced sports athletes and non-athletes, whereas athletes from externally-paced sports outperformed non-athletes. Crucially, athletes from externally-paced sports also differed from those of self-paced sports and non-athletes in the Oddball task, showing less omission and commission errors. The sport expertise effect was independent of participant’s cardiovascular fitness while hand-eye coordination modulated vigilance and inhibitory control performance. Our findings add novel empirical evidence to the role of expertise in cognitively demanding sports as an important factor in the relationship between exercise and cognition.     

不同重量的铅球在教学与训练中的作用

实验显示，持不同重量的铅球对滑步推铅球有关的运动参数有显影响，高水平运动员能够延长主要阶段中第3阶段铅球投掷距离，适当的重量不但可以用来发展专项速度和力量，而且还可以进一步改进运动员的技术。     

Knee joint forces during downhill walking with hiking poles

The aim of this study was to determine external and internal loads on the knee joint during downhill walking with and without hiking poles. Kinematic, kinetic and electromyographic data were collected from eight males during downhill walking on a ramp declined at 25 degrees. Planar knee joint moments and forces were calculated using a quasi-static knee model. The results were analysed for an entire pole-cycle as well as differentiated between single and double support phases and between each step of a pole-cycle. Significant differences between downhill walking with and without hiking poles were observed for peak and average magnitudes of ground reaction force, knee joint moment, and tibiofemoral compressive and shear forces (12-25%). Similar reductions were found in patellofemoral compressive force, the quadriceps tendon force and the activity of the vastus lateralis; however, because of a high variability, these differences were not significant. The reductions seen during downhill walking with hiking poles compared with unsupported downhill walking were caused primarily by the forces applied to the hiking poles and by a change in posture to a more forward leaning position of the upper body, with the effect of reducing the knee moment arm.     

Older Adult Compendium of Physical Activities:Energy costs of human activities in adults aged 60 and older

Purpose:To describe the development of a Compendium for estimating the energy costs of activities in adults>60 years(OA Compendium).Methods:Physical activities(PAs) and their metabolic equivalent of task(MET) values were obtained from a systematic search of studies published in 4 sport and exercise databases(PubMed,Embase,SPORTDiscus(EBSCOhost),and Scopus) and a review of articles included in the 2011 Adult Compendium that measured PA in older adults.MET values were computed as the oxygen cos...     

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.     

Effect of walking speed on lower extremity joint loading in graded ramp walking

Lower extremity joint loading during walking is strongly affected by the steepness of the slope and might cause pain and injuries in lower extremity joint structures. One feasible measure to reduce joint loading is the reduction of walking speed. Positive effects have been shown for level walking, but not for graded walking or hiking conditions. The aim of the study was to quantify the effect of walking speed (separated into the two components, step length and cadence) on the joint power of the hip, knee and ankle and to determine the knee joint forces in uphill and downhill walking. Ten participants walked up and down a ramp with step lengths of 0.46, 0.575 and 0.69 m and cadences of 80, 100 and 120 steps per minute. The ramp was equipped with a force platform and the locomotion was filmed with a 60 Hz video camera. Loading of the lower extremity joints was determined using inverse dynamics. A two-dimensional knee model was used to calculate forces in the knee structures during the stance phase. Walking speed affected lower extremity joint loading substantially and significantly. Change of step length caused much greater loading changes for all joints compared with change of cadence; the effects were more distinct in downhill than in uphill walking. The results indicate that lower extremity joint loading can be effectively controlled by varying step length and cadence during graded uphill and downhill walking. Hikers can avoid or reduce pain and injuries by reducing walking speed, particularly in downhill walking.     

Correlates of change in walking for exercise: an exploratory analysis.

This study was designed to identify correlates of change in walking for exercise. Respondents to a random sample mailed exercise survey were asked to complete a follow-up questionnaire 24 months after the first. Responses were obtained from 1,739 adults, reflecting an 86.6% return rate. Nonrespondents did not differ from respondents for baseline level of walking for exercise. Respondents overrepresented Caucasian and middle to high education (or income) adults. Residualized measures of change in walking for exercise served as the dependent variable, adjusted for baseline walking. Similarly, key independent variables, subject to change over time, were included after residualization. At both baseline and 24 months follow-up, adults walked for exercise an average of just under 1 hour per week, and 23.5% of the initially active adults ceased walking for exercise at 2 years. Multiple regression analyses explained more variance in walking for exercise among women than men. Change in dynamic variables such as friend's support and vigorous physical activity accounted for most of the explained variance. Results suggest that dynamic variables may need to be sustained to maintain walking for exercise. The limited explained variance suggests that more precise measures and additional determinants of walking for exercise need to be identified.     

Implicit overcompensation: the influence of negative self-instructions on performance of a self-paced motor task

According to Wegner's (1994) theory of ironic processes of mental control, self-instructions not to perform in a certain way, together with mental loads, can induce thoughts, emotions, and behaviours that are precisely the opposite of intention. Wegner's theory was tested against the implicit overcompensation hypothesis, which states that movement direction and magnitude are implicitly dictated by self-instruction, irrespective of load, promoting overcompensation of action. Two experiments were conducted using a golf-putting task. In Experiment 1, 48 participants were randomly assigned to one of four load conditions: cognitive, visual, auditory, and self-presentation/incentive. In the experimental trials, participants were instructed to make the putt, but it was emphasized that the putt should not be left short of the target. Following the instructional strategy, putts landed significantly longer than at baseline, irrespective of load. In Experiment 2, 36 participants were divided into one of three groups, without load, in which different instructional sets (control, not putting long, and not putting short) were emphasized. A significant interaction emerged, as participants putted significantly longer or shorter than controls depending on the instructional set given. Overall, our findings support the implicit overcompensation hypothesis. Theoretical and practical considerations are discussed.     

The metabolic cost of two ranges of arm position height with and without hand weights during low impact aerobic dance.

To determine the energy cost of low impact aerobic dance while varying arm movement height and the use of hand weights, 10 adults volunteered to participate in four choreographed trials. All trials consisted of identical leg movements. Arm movements, however, were performed above shoulder level both with and without 0.9-kg hand weights and below shoulder level both with and without 0.9-kg hand weights. Open circuit spirometry was employed throughout the 10-min videotape guided trials, and heart rate was measured by telemetry. Neither the use of hand weights nor the change in arm position height significantly altered the energy cost of low impact aerobic dance. However, heart rate responses were significantly different. Caution should be observed by aerobics instructors and participants as to the use of heart rate as an indicator of intensity for low impact aerobic dance.     

An investigation of the accuracy and reliability of body composition assessed with a handheld electrical impedance myography device

The purpose of this study was to compare the body fat per cent (BF%) assessed with a unique handheld electrical impedance myography (EIM) device, along with other popular methods, to dual-energy X-ray absorptiometry (DXA). Participants included 33 males (aged 24.3?±?4.6 years) and 38 females (aged 25.3?±?8.9 years) who completed 2 visits separated by 24–72?h. The assessments included DXA, bioelectrical impedance analysis (BIA), skinfold measures (SKF), and three separate EIM measurements. No significant differences in BF% (P?>?0.05) were found between all EIM assessments when compared against DXA for both males and females for each visit. All methods showed no significant differences in BF% (P?>?0.05) between days within themselves. Across both days, the standard error of the estimate (SEE) for the EIM measurements ranged from 2.66% to 3.15%, the SEE for BIA was 2.80 and 2.85, and for SKF was 2.90 and 2.82. The 95% limits of agreement ranged from ±5.34% to ±6.38% for EIM measurements and were highest for SKF (±7.42% and ±7.47%). The total error for both days was largest for SKF (5.20% and 5.35%) and lowest for the EIM measurements (2.48–3.24%). This investigation supports use of a handheld EIM device as an accurate and reliable method of estimating BF% compared to DXA in young, apparently healthy individuals with BF% in the range of 10–22% for males and 20–32% in females and suggests this EIM device be considered a viable alternative to other established field measurements in this population.     

Implicit overcompensation: The influence of negative self-instructions on performance of a self-paced motor task

Abstract

This study sought to compare the time course changes in oxidative state and glycemic behavior when glucose or glucose plus fructose are consumed before endurance and strength exercise. After two weeks on a controlled diet, 20 physically trained males ingested an oral dose of glucose or glucose plus fructose, 15 min before starting a moderate-intensity 30-min session of endurance or strength exercise. The combination resulted in four randomized interventions: glucose or glucose plus fructose + endurance exercise and glucose or glucose plus fructose + strength exercise, which were implemented consecutively in random order at 1-week intervals. Plasma concentration of lipoperoxides, oxidized LDL, reduced glutathione, catalase and glycemia were determined at baseline, during exercise and acute recovery. Following the ingestion of glucose plus fructose, lipoperoxides, catalase and reduced glutathione depletion were significantly higher than following consumption of glucose, for both endurance and strength exercise (P < 0.05). Oxidized LDL-c was higher after glucose plus fructose than after glucose alone in endurance exercise (P < 0.05). There was no difference in the glycemic peak between glucose plus fructose and glucose ingestion in endurance exercise trials. In strength exercise, the post-absorptive glycemic peak was less when the participants ingested glucose plus fructose than glucose (P < 0.05), and a second peak was found in the recovery phase of this group (P < 0.05). In conclusion, the addition of fructose to a pre-exercise glucose supplement triggers oxidative stress.     

青年女性着高跟鞋平地行走时步态的生物力学研究

通过SIMI-MOTION录像解析系统和F-scan足底压力分布解析系统对青年女性穿高跟鞋行走时的步态进行运动学和动力学测量和分析。结果表明:青少年女性穿高跟鞋行走时的步态特征表现为:步长短,步速慢,步态周期长,重心起伏幅度大,单支撑时相占支撑时相比例低,说明青少年女性穿高跟鞋行走时下肢肌肉机能减弱;青少年女性穿跟高6.5cm以上的高跟鞋行走时,足底第一跖趾关节最大受力值是青少年女性穿球鞋行走时该点最大受力值的4倍,是青少年女性穿中跟鞋和松糕鞋行走时该点最大受力值的2倍。     

Biomechanics of stair walking and jumping

Physical activities such as stair walking and jumping result in increased dynamic loading on the human musculoskeletal system. Use of light weight, externally attached accelerometers allows for in-vivo monitoring of the shock waves invading the human musculoskeletal system during those activities. Shock waves were measured in four subjects performing stair walking up and down, jumping in place and jumping off a fixed elevation. The results obtained show that walking down a staircase induced shock waves with amplitude of 130% of that observed in walking up stairs and 250% of the shock waves experienced in level gait. The jumping test revealed levels of the shock waves nearly eight times higher than that in level walking. It was also shown that the shock waves invading the human musculoskeletal system may be generated not only by the heel strike, but also by the metatarsal strike. To moderate the risk of degenerative joint disorders four types of viscoelastic insoles were utilized to reduce the impact generated shock waves. The insoles investigated were able to reduce the amplitude of the shock wave by between 9% and 41% depending on the insole type and particular physical activity. The insoles were more effective in the reduction of the heel strike impacts than in the reduction of the metatarsal strike impacts. In all instances, the shock attenuation capacities of the insoles tested were greater in the jumping trials than in the stair walking studies. The insoles were ranked in three groups on the basis of their shock absorbing capacity.     

多学科理论研究对改进竞走技术的意义

改进竞走技术仅从动作现象上,从定义上,从适应裁判判罚上着手是不够深入的,易反复;运用运动学,运动生物力学,运动解剖学,运动心理学等基础理论学科的研究成果,服务于训练实践,提升和改进竞走技术的成效较为明显。     

穿着两种不同鞋行走时足底特征对比分析

测试相同人群穿跑鞋和板鞋行走时足底压力、压强及冲量特征,结合运动学采集分析不同速度行走时人体下肢的运动学和足底力学特征,结果显示:穿慢跑鞋和穿板鞋相比,第一趾骨与第二跖骨及足跟区存在非常显著差异;行走过程中这两个区域足底平均压力峰值板鞋组显著大于慢跑鞋组(P＜0.05).慢跑鞋较板鞋表现出跖骨区压力小、足中部压力大、足跟区压力小,均存在显著差异(P＜0.05).以期为健步走人群不同速度行走时提供可行性建议.