小学阶段超重/肥胖儿童平地行走的运动学分析

目的 通过比较小学阶段超重/肥胖儿童和正常儿童平地行走时的运动学参数,探讨超重/肥胖对儿童步态的影响。方法 选取40名超重/肥胖儿童(年龄(9.6±1.72)岁;身高(142.16±12.19) cm;身体质量指数（BMI）(24.32±2.96) kg/m2)和50名正常体重儿童(年龄(10.26±0.72)岁;身高(139.0±7.50) cm; BMI(17.08±1.25) kg/m2)为研究对象,受试者赤足以自己感觉舒适的常速自然行走在长10 m的跑道,共3次;使用常速摄像机进行平面定点拍摄,采集他们平地自然行走时的图像,通过视迅录像解析系统获得步长、下肢关节角度等运动学指标;数据采用SPSS 16.0进行统计学处理,受试者各项指标左右侧的比较采用配对t检验,两组儿童的各项指标比较采用独立样本t检验,P<0.05表示结果有显著性差异。结果 （1）对于相对步长,超重/肥胖儿童（0.44±0.001)与正常儿童显著不同（0.45±0.001）(P<0.05)。（2）足跟着地阶段,左髋及左、右膝在矢状面上的角度,超重/肥胖儿童（左髋(165.36±5.29)°,左膝(178.82±5.51)°,右膝(177.84±5.25)°）与正常儿童（左髋(161.99±4.28)°,左膝(174.67±4.91)°,右膝(174.67±4.91)°）显著不同(P<0.05);足跟蹬伸阶段,矢状面上的左踝关节角,超重/肥胖儿童（(121.73±8.03)°）与正常儿童（(118.44±6.70)°）显著不同(P<0.05)。结论 自然行走过程中,超重/肥胖儿童比正常儿童相对步长显著减小;足跟着地阶段,超重/肥胖儿童在矢状面上左髋和左右膝关节角显著大于正常儿童;足蹬伸阶段,超重/肥胖儿童在矢状面上的左踝关节角显著大于正常儿童。这些变化可能会对超重/肥胖儿童的下肢功能造成一定的影响。     

Variability of gait patterns during unconstrained walking assessed by satellite positioning (GPS)

It is established that the ratio between step length (SL) and step frequency (SF) is constant over a large range of walking speed. However, few data are available about the spontaneous variability of this ratio during unconstrained outdoor walking, in particular over a sufficient number of steps. The purpose of the present study was to assess the inter- and intra-subject variability of spatio-temporal gait characteristics [SL, SF and walk ratio (WR=SL/SF)] while walking at different freely selected speeds. Twelve healthy subjects walked three times along a 100-m athletic track at: (1) a slower than preferred speed, (2) preferred speed and (3) a faster than preferred speed. Two professional GPS receivers providing 3D positions assessed the walking speed and SF with high precision (less than 0.5% error). Intra-subject variability was calculated as the variation among eight consecutive 5-s samples. WR was found to be constant at preferred and fast speeds [0.41 (0.04) m·s and 0.41 (0.05) m·s respectively] but was higher at slow speeds [0.44 (0.05) m·s]. In other words, between slow and preferred speed, the speed increase was mediated more by a change in SF than SL. The intra-subject variability of WR was low under preferred [CV, coefficient of variation = 1.9 (0.6)%] and fast [CV=1.8 (0.5)%] speed conditions, but higher under low speed condition [CV=4.1 (1.5)%]. On the other hand, the inter-subject variability of WR was 11%, 10% and 12% at slow, preferred and fast walking speeds respectively. It is concluded that the GPS method is able to capture basic gait parameters over a short period of time (5 s). A specific gait pattern for slow walking was observed. Furthermore, it seems that the walking patterns in free-living conditions exhibit low intra-individual variability, but that there is substantial variability between subjects.     

The metabolic transition speed between backward walking and running

Although the metabolic transition speed for forward exercise has already been determined, the walk–run transition speed for backward exercise has not been investigated before. The aim of this study was to determine the speed at which it becomes metabolically more efficient to run backwards than to walk backwards. Eighteen healthy volunteers, who successfully completed three backward exercise practice sessions, participated in the study. All subjects randomly performed two exercise tests: backward walking and backward running. Both protocols started at a treadmill speed of 5 km^.h^–1. Every minute the speed was increased by 0.5 km^.h^–1 until 8 km^.h^–1 was reached. Cardiorespiratory variables were continuously measured and blood lactate concentration [La] was determined every 2 min, using the Accusport lactate analyser. At each work load subjects rated their perceived exertion (RPE), using the Borg scale. There were no statistically significant differences in oxygen consumption, minute ventilation and heart rate between 6 and 7 km^.h^–1, for backward walking and backward running (P>0.05). There was no statistically significant difference in blood [La] between walking and running at 7.5 km^.h^-1 (P>0.05). According to the RPE values, subjects rated running at speeds less than 6 km^.h^–1 more difficult than walking at similar speeds. We conclude that the metabolic transition speed between backward walking and running is between 6 and 7 km^.h^–1, which is lower than the metabolic transition speed for forward locomotion (7.2–7.9 km^.h^–1).     

Determination of the oxygen cost of level walking

We have developed devices and methods for the determination of the oxygen cost of level walking. Oxygen uptake is determined with an argon dilution method. The validity of this technique is demonstrated. Walking speed is recorded and controlled by means of a speedometer cart. The reproducibility of a convenient, self-selected walking speed and of a predetermined speed was studied. Coefficients of variation were below two per cent. Corresponding values of the oxygen cost of walking at a predetermined speed were three per cent or less up to an interval between tests of six months. We conclude that the proposed methods are suited for longitudinal studies of the oxygen cost of level walking, for example in patients with walking disorders.     

Sex difference in the pattern of lower limb movement during treadmill walking

Summary To evaluate the characteristics of stereotyped movement of the lower limb during treadmill walking, the step length and duration of 200 steps were monitored consecutively and calculated by means of a computerized system, consisting of a position sensor, shoes with foot switches and a minicomputer. Eleven male and 10 female subjects walked at various constant speeds ranging from 60–130 m · min^–1. Mean, standard deviation (SD) and coefficient of variation (CV) of the time-distance component at each speed were utilized for the assessment of stereotyped movement. When compared with males, females had a tendency to increase their speed by increasing their cadence. The difference of the walking pattern was specifically related to their height. The SD and CV of the time-distance component at a given speed were significantly greater in females than in males. Regression analyses revealed that in the relationship between the walking speeds and the SDs or CVs of the time-distance component, the significant quadratic equations could be fitted. The speed, at which the SD of step length was minimum, was estimated to be about 90 m · min^–1 in both males and females. This was regarded as the free walking speed or as the walking speed resulting from a mechanically efficient step length which suited the subject's body size.     

Increased strength and decreased flexibility are related to reduced oxygen cost of walking

Purpose was determine effects resistance training/weight loss induced changes in muscular strength and flexibility have on net walking oxygen uptake (netVO₂). Sixty-seven premenopausal women lost 12 kg. Before weight loss subjects were assigned to diet (WL) or diet/3 days per week resistance training (WLRT). Resting energy expenditure, oxygen uptake while walking at 4.84 km h⁻¹ on the flat and up 2.5% grade, isometric knee extension strength, and flexibility of the knee extensors and plantar flexors were measured. Strength increased in WLRT (+36 N) but not in WL (−24 N). NetVO₂ decreased significantly while flat walking (7.3%) and 2.5% grade walking (5.7%) in WLRT, but not in WL. Delta strength was negatively while delta knee extensor and plantar flexor flexibility were positively related to delta netVO₂. Decreases in walking and grade netVO₂ were independently and positively related to increased knee extension strength and decreased knee extensor and plantar flexor flexibility.     

The energy cost of walking or running on sand

Summary Oxygen uptake ( O₂) at steady state, heart rate and perceived exertion were determined on nine subjects (six men and three women) while walking (3–7 km · h^–1) or running (7–14 km · h^–1) on sand or on a firm surface. The women performed the walking tests only. The energy cost of locomotion per unit of distance (C) was then calculated from the ratio of O₂ to speed and expressed in J · kg^–1 · m^–1 assuming an energy equivalent of 20.9 J · ml O₂ ^–1. At the highest speedsC was adjusted for the measured lactate contribution (which ranged from approximately 2% to approximately 11% of the total). It was found that, when walking on sand,C increased linearly with speed from 3.1 J · kg^–1 · m^–1 at 3 km · h^–1 to 5.5 J · kg^–1 · m^–1 at 7 km · h^–1, whereas on a firm surfaceC attained a minimum of 2.3 J · kg^–1 · m^–1 at 4.5 km · h^–1 being greater at lower or higher speeds. On average, when walking at speeds greater than 3 km · h^–1,C was about 1.8 times greater on sand than on compact terrain. When running on sandC was approximately independent of the speed, amounting to 5.3 J · kg^–1 · m^–1, i.e. about 1.2 times greater than on compact terrain. These findings could be attributed to a reduced recovery of potential and kinetic energy at each stride when walking on sand (approximately 45% to be compared to approximately 65% on a firm surface) and to a reduced recovery of elastic energy when running on sand.     

Elastic strain energy in the low back muscles during human walking

Summary A simple model of the thorax, pelvis and three columns of the intrinsic lumbar back muscles (=ILBM) was constructed. The model was used to study the length of the ILBM during the different stages of the walking cycle. The length of the right ILBM (especially the lateral column) was largest at right toe off, exactly the stage of the walking cycle in which most force was needed to prevent the torso from falling forwards and laterally.     

Energy cost of treadmill and floor walking at self-selected paces

Summary Oxygen uptake-velocity regression equations were developed for floor and level treadmill walking by having two groups of men, aged 19–29 years (n=20) and 55–66 years (n=22), walk at four self-selected paces, from “rather slowly” to “as fast as possible”. A two-variable quadratric model relating VO₂ (ml·kg⁻¹·min⁻¹) to velocity (m·s⁻¹) was adopted for prediction purposes. However, age and fatness significantly (p<0.05) interacted with treadmill walking speed, while age alone significantly interacted with floor speed. In addition, a significant difference was found between the energy cost of floor and treadmill walking. For example at the normal walking speed of 1.33 m·s⁻¹, the energy cost for the treadmill (age 55–66 years) was 10.58 ml·kg⁻¹·min⁻¹ and for the floor, 11.04 ml·kg⁻¹·min⁻¹ (p<0.05). Four quadratic equations are therefore presented, one each for floor and treadmill in each of the two age-groups. The percent variance explained was between 87 and 95% for each of these equations. Supported by a grant from the Ontario Ministry of Health (DM449)     

Carcinoembryonic antigen level can be overestimated in metabolic syndrome

Carcinoembryonic antigen (CEA) levels can be affected by many factors and metabolic syndrome is also a candidate. This study examined the relationship between CEA levels and metabolic syndrome using the data of 32,897 healthy Koreans. Fecal occult blood tests were also performed. Subjects with colorectal carcinoma were excluded. Subjects were classified by their smoking status, metabolic syndrome and its components. Prevalence of metabolic syndrome and its all components showed a significant increase according to the quartile of serum CEA concentration (P < 0.001). Increased numbers of metabolic syndrome components showed a positive association with CEA levels (P-trend < 0.001). The odds ratios for the highest CEA quartile vs the lowest serum CEA quartile significantly increased in the presence of metabolic syndrome and its components. After adjusting for age, gender and smoking status, metabolic syndrome, low high density lipoprotein cholesterol and elevated blood pressure had higher odds ratios (OR) of the highest CEA quartile compared with the lowest serum CEA quartile (OR = 1.125, 95% CI = 1.030 to 1.222, P = 0.009; OR = 1.296, 95% CI = 1.195 to 1.405, P < 0.001; OR = 1.334, 95% CI = 1.229 to 1.448, P < 0.001, respectively). These results indicate that metabolic syndrome is associated with CEA value, which may lead to a misunderstanding of the CEA levels.     

正走和倒走的膝关节生物力学特征比较

目的 比较正走和倒走两种不同行走模式时膝关节的生物力学特征。方法 采用三维运动捕捉系统Vicon T40和测力台AMTI OR6-7采集并比较13名健康青年男性志愿者正走和倒走时的时间、空间、运动学和动力学参数。结果 与正走相比,倒走时的步速、步频和步幅均显著减小,跨步周期和支撑相所占百分比显著增加;在矢状面上,倒走时膝关节活动度、最大屈伸力矩较正走小;在冠状面上,倒走时膝关节内翻外展活动范围也较正走小,内翻力矩峰值在支撑早期较正走小,但在支撑晚期较正走大;地面反作用力在支撑早期较正走大,但在支撑晚期较正走小。结论 倒走和正走膝关节生物力学特征差异明显。与正走相比倒走在支撑相早期能减轻膝关节内侧间室的负荷,而倒走在支撑相晚期对膝关节负荷的影响则尚须进一步研究。     

Serum calcium level is associated with metabolic syndrome in elderly women

Objective

To investigate the association between serum calcium level and metabolic syndrome, defined using the National Cholesterol Education Program-Adult Treatment Panel III (NCEP-ATP III) definition, in Korean elderly women.

Study design

We conducted a cross-sectional study of 1941 elderly women (mean age: 65.16 ± 4.58 years) who participated in annual health examinations at Korea university Medical Center between January 1, 2006 and December 31, 2009 and had normal serum calcium levels.

Results

Women with metabolic syndrome had higher serum calcium levels than those without metabolic syndrome (9.26 ± 0.35 vs. 9.20 ± 0.33, P < 0.001). In multiple logistic regression analysis, serum calcium level within normal range was positively associated with the risk of having metabolic syndrome (odds ratio 2.12, 95% confidence interval 1.50–2.98). With regard to components of metabolic syndrome, serum calcium level was also positively associated with the risk of having high triglyceride, and high glucose, whereas it was inversely associated with the risk of having low high density lipoprotein. However, there was no association of serum calcium level with abdominal obesity or high blood pressure.

Conclusions

The higher was the level of calcium within normal range, the greater were the odds of metabolic syndrome in healthy and elderly women. Prospective studies are needed to investigate the role of calcium in the development of metabolic syndrome in the future.     

Differentiated perceptions of exertion and energy cost of young women while carrying loads

Summary Differentiated local ratings of perceived exertion from the legs and central ratings from the chest, and oxygen consumption, were determined during load carriage in seven young women. Subjects walked for 6 min at 3.22, 4.83, 6.44, or 8.05 km·h^–1 carrying (1) no load, (2) a load equal to 7.5% of body weight (mean: 4.66 kg) or (3) a load equal to 15% of body weight (mean: 9.32 kg). Thus, each subject underwent 12 separate tests. The external loads were in the form of lead pellets carried in a plastic scuba belt worn around the waist. A differentiation threshold was found at 6.44 km·h^–1 for the 0% and 7.5% loads and at 4.83 km·h^–1 for the 15% load. At speeds below the threshold, the perception of exertion was similar in the legs, chest and overall. At higher speeds, exertion was perceived to be more intense in the legs than overall and less intense in the chest than overall, suggesting that the local legs signal was the dominant factor in shaping the overall sensation of exertion. The oxygen uptake was greater for the 15% load than for either the 0% or 7.5% loads, but was similar for the 0% and 7.5% loads. Findings suggested a critical weight limit for external loads that could be transported without increasing the metabolic cost beyond that required to move the body weight alone. This limit fell between 7.5% and 15% of the body weight. When oxygen uptake was expressed per kg of total weight transported, there was no loss of metabolic efficiency while carrying loads up to 15% of the body weight.     

Effect of load and speed on the energetic cost of human walking

It is well established that the energy cost per unit distance traveled is minimal at an intermediate walking speed in humans, defining an energetically optimal walking speed. However, little is known about the optimal walking speed while carrying a load. In this work, we studied the effect of speed and load on the energy expenditure of walking. The O₂ consumption and CO₂ production were measured in ten subjects while standing or walking at different speeds from 0.5 to 1.7 m s^–1 with loads from 0 to 75% of their body mass (M_b). The loads were carried in typical trekkers backpacks with hip support. Our results show that the mass-specific gross metabolic power increases curvilinearly with speed and is directly proportional to the load at any speed. For all loading conditions, the gross metabolic energy cost (J kg^–1 m^–1) presents a U-shaped curve with a minimum at around 1.3 m s^–1. At that optimal speed, a load up to 1/4 M_b seems appropriate for long-distance walks. In addition, the optimal speed for net cost minimization is around 1.06 m s^–1 and is independent of load.     

The transition between walking and running in humans: metabolic and mechanical aspects at different gradients

Five subjects walked and ran at overlapping speeds and different gradients on a motorized treadmill. At each gradient the speed was obtained at which walking and running have the same metabolic cost (Sm) and the speed of spontaneous (Ss) transition between the two gaits was measured. Ss was found to be statistically lower than Sm at all gradients, the difference being in the range of 0.5–0.9 km h^-1. The motion analysis of walking reveals that at all gradients and at increasing speed: (1) the percentage of recovery, an index of mechanical energy saving related to the pendulum–like characteristic of walking, decreases; (2) the lower limb spread reaches a limit in walking; and consequently (3) both the stride frequency and the internal mechanical work, due to limb acceleration in relation to the body centre of mass, increase much more in walking than in running. Switching to a run, although implying a higher frequency, makes the internal work decrease as a result of the lower limb spread. In this paper several influences, such as the ‘ratings of perceived exertion’ (RPE), on the choice of beginning to run when it is more economical to walk, are discussed. A tentative hypothesis on the determinants of Ss, which is emphasized to be a speed which has to be studied in detail but is generally avoided in locomotion, is based on a comfort criterion from peripheric afferences and is reflected by the fact that at Ss a running stride costs as much as a walking stride. A preliminary measure of the subjects' behaviour during spontaneous overground locomotion, where the progression speed can be changed freely, reveals that the running speed immediately following gait transition is approximately 2 km h^-1 higher than the ‘last’ walking speed, supporting the hypothesis of metabolic energy minimization.     

Comparison of the metabolic energy cost of overground and treadmill walking in older adults

We assessed whether the metabolic energy cost of walking was higher when measured overground or on a treadmill in a population of healthy older adults. We also assessed the association between the two testing modes. Participants (n = 20, 14 men and 6 women aged between 65 and 83 years of age) were randomly divided into two groups. Half of them went through the overground–treadmill sequence while the other half did the opposite order. A familiarization visit was held for each participant prior to the actual testing. For both modes of testing, five walking speeds were experimented (0.67, 0.89, 1.11, 1.33 and 1.67 m s⁻¹). Oxygen uptake was monitored for all walking speeds. We found a significant difference between treadmill and track metabolic energy cost of walking, whatever the walking speed. The results show that walking on the treadmill requires more metabolic energy than walking overground for all experimental speeds (P < 0.05). The association between both measures was low to moderate (0.17 < ICC < 0.65), and the standard error of measurement represented 6.9–15.7% of the average value. These data indicate that metabolic energy cost of walking results from a treadmill test does not necessarily apply in daily overground activities. Interventions aiming at reducing the metabolic energy cost of walking should be assessed with the same mode as it was proposed during the intervention. If the treadmill mode is necessary for any purposes, functional overground walking tests should be implemented to obtain a more complete and specific evaluation.     

Variations in resting metabolic rates of men in Antarctica

Summary The resting metabolic rates (RMR) of 6 men was determined monthly for 12 consecutive months, at Rothera Base, Antarctica (67°34S, 68°07W). Body weight and body composition were also recorded. Metabolic rates were within the range of those found in past polar studies, and of young men in the UK, but varied considerably from month to month. The RMR had a mean range of 30% (p<0.01), with individual ranges of up to 38%. Mean RMR was high in spring, summer and autumn, and low in winter. While these patterns appeared to be associated with a well defined annual cycle of activity, variations could not be correlated with periods of intense activity, individually or for the group.     

The influence of stroke mechanics into energy cost of elite swimmers

The purpose of this study was to analyze the relationships between energy cost (C), swimming velocity (v), stroke frequency (SF) and stroke length (SL) in top-level swimmers. Eighteen elite swimmers (four freestylers, five backstrokers, five breaststrokers and four butterflyers) performed an intermittent set of n × 200 m swims (n ≤ 8) with increasing velocity. The oxygen consumption was measured breath-by-breath by a portable metabolic cart (K4 b2, Cosmed, Rome, Italy). A respiratory snorkel and valve system with low hydrodynamic resistance was used to measure pulmonary ventilation and collect expiratory gases. Blood samples were taken from the ear lobe before and after each swim to analyze the blood lactate concentration (YSI 1500L, Yellow Springs, OH, USA). At Backstroke, Breaststroke and Butterfly strokes, increases of SF were associated to increases of C, even when controlling the v. The increases in SL only promoted significant decreases in the C in Breaststroke. There was a significant and polynomial relationship between v and SF for all competitive swimming techniques. The polynomial relationship between v and SL was significant only in Freestyle and Butterfly stroke. Partial correlations between v and SF controlling the effect of SL and between v and SL controlling the effect of SF, were positive and significant for all techniques. It is concluded that manipulation of stroke mechanics variables (SF and SL) may be one of the factors through which C in competitive swimming can be altered for a given v.     

Metabolic cost, mechanical work, and efficiency during walking in young and older men

Aim: To investigate mechanical work, efficiency, and antagonist muscle co‐activation with a view to better understand the cause of the elevated metabolic cost of walking (C_W) in older adults. Methods: Metabolic, mechanical and electromyographic measurements were made as healthy young (YOU; n = 12, age = 27 ± 3 years) and older (OLD; n = 20, age = 74 ± 3 years) men of equivalent body mass and leg length walked on a treadmill at four speeds (ranging from 0.83 to 1.67 m s^?1). Results: Net (above resting) C_W, determined by indirect calorimetry was 31% higher (average across speeds) in OLD (P < 0.05). The integrity of the passive pendulum like interchange of mechanical energies of the centre of mass (COM_B), an energy‐saving mechanism, was maintained in OLD. Furthermore, total mechanical work, determined from fluctuations in mechanical energy of COM_B and of body segments relative to COM_B, was not significantly elevated in OLD. This resulted in a lower efficiency in OLD (?17%, P < 0.05). Co‐activation, temporally quantified from electromyography recordings, was 31% higher in OLD for antagonist muscles of the thigh (P < 0.05). Thigh co‐activation was moderately correlated with C_W at three speeds (r = 0.38–0.52, P < 0.05). Conclusion: Healthy septuagenarians with no gait impairment have an elevated C_W which is not explained by an elevation in whole body mechanical work. Increased antagonist muscle co‐activation (possibly an adaptation to ensure adequate joint stability) may offer partial explanation of the elevated C_W.