Lower extremity kinematics and ground reaction forces after prophylactic lace-up ankle bracing

CONTEXT: Long-term effects of ankle bracing on lower extremity kinematics and kinetics are unknown. Ankle motion restriction may negatively affect the body's ability to attenuate ground reaction forces (GRFs). OBJECTIVE: To evaluate the immediate and long-term effects of ankle bracing on lower extremity kinematics and GRFs during a jump landing. DESIGN: Experimental mixed model (2 [group] x 2 [brace] x 2 [time]) with repeated measures. SETTING: Sports medicine research laboratory. PATIENTS OR OTHER PARTICIPANTS: A total of 37 healthy subjects were assigned randomly to either the intervention (n = 11 men, 8 women; age = 19.63 +/- 0.72 years, height = 176.05 +/- 10.58 cm, mass = 71.50 +/- 13.15 kg) or control group (n = 11 men, 7 women; age = 19.94 +/- 1.44 years, height = 179.15 +/- 8.81 cm, mass = 74.10 +/- 10.33 kg). INTERVENTION(S): The intervention group wore braces on both ankles and the control group did not wear braces during all recreational activities for an 8-week period. MAIN OUTCOME MEASURE(S): Initial ground contact angles, maximum joint angles, time to reach maximum joint angles, and joint range of motion for sagittal-plane knee and ankle motion were measured during a jump-landing task. Peak vertical GRF and the time to reach peak vertical GRF were assessed also. RESULTS: While participants were wearing the brace, ankle plantar flexion at initial ground contact (brace = 35 degrees +/- 13 degrees , no brace = 38 degrees +/- 15 degrees , P = .024), maximum dorsiflexion (brace = 21 degrees +/- 7 degrees , no brace = 22 degrees +/- 6 degrees , P = .04), dorsiflexion range of motion (brace = 56 degrees +/- 14 degrees , no brace = 59 degrees +/- 16 degrees , P = .001), and knee flexion range of motion (brace = 79 degrees +/- 16 degrees , no brace = 82 degrees +/- 16 degrees , P = .036) decreased, whereas knee flexion at initial ground contact increased (brace = 12 degrees +/- 9 degrees , no brace = 9 degrees +/- 9 degrees , P = .0001). Wearing the brace for 8 weeks did not affect any of the outcome measures, and the brace caused no changes in vertical GRFs (P > .05). CONCLUSIONS: Although ankle sagittal-plane motion was restricted with the brace, knee flexion upon landing increased and peak vertical GRF did not change. The type of lace-up brace used in this study appeared to restrict ankle motion without increasing knee extension or vertical GRFs and without changing kinematics or kinetics over time.     

The effect of cycling followed by running on respiratory muscle performance in elite and competition triathletes

This study investigated the possibility of there being differences in respiratory muscle strength and endurance in elite and competition triathletes who have similar maximal oxygen uptakes (VO_2max) and ventilatory thresholds (Th_vent). Five internationally-ranked elite, [mean (SD) age 23.8 (1.4) years] and six nationally- and regionally-ranked competition [age 21.1 (1.1) years] male triathletes performed two successive trials: first an incremental cycle test to assess VO_2max and Th_vent and second 20 min of cycling followed by 20 min of running (C-R) at intensities higher than 85% VO_2max. Cardioventilatory data were collected every minute during the two trials, using an automated breath-by-breath system. Maximal expiratory and inspiratory (P _Imax) strength were assessed before and 10 min after C-R from the functional residual capacity. Respiratory muscle endurance was assessed 1 day before and 30 min after C-R by measuring the time limit (t _lim). The results showed firstly that during C-R, the competition triathletes had significantly (P<0.05) higher minute ventilation [mean (SEM) 107.4 (3.1) compared to 99.8 (3.7) l·min^–1], breathing frequency [44.4 (2.0) compared to 40.2 (3.4) ·min^–1] and heart rate [166 (3) compared to 159 (4) beats·min^–1] and secondly that after C-R, they had significantly lower P _Imax [127.1 (4.2) compared to 130.7 (3.0) cmH₂O] and t_lim [2:35 (0:29) compared to 4:12 (0:20) min] than the elite triathletes. We conclude that, despite similar VO_2max and Th_vent, the competition triathletes showed less extensive adaptive mechanisms, including those in the respiratory muscles, than did the elite triathletes. This led to higher ventilation, which appeared to be the cause of the faster development of fatigue in the inspiratory muscles in this group. Electronic Publication     

The influence of prior cycling on biomechanical and cardiorespiratory response profiles during running in triathletes

The aim of the present study was to determine the effects of 40 km of cycling on the biomechanical and cardiorespiratory responses measured during the running segment of a classic triathlon, with particular emphasis on the time course of these responses. Seven male triathletes underwent four successive laboratory trials: (1) 40 km of cycling followed by a 10-km triathlon run (TR), (2) a 10-km control run (CR) at the same speed as TR, (3) an incremental treadmill test, and (4) an incremental cycle test. The following ventilatory data were collected every minute using an automated breath-by-breath system: pulmonary ventilation (V˙ _E, l · min⁻¹), oxygen uptake (V˙O₂, ml · min⁻¹ · kg⁻¹), carbon dioxide output (ml · min⁻¹), respiratory equivalents for oxygen (V˙ _E/V˙O₂) and carbon dioxide (V˙ _E/V˙CO₂), respiratory exchange ratio (R) respiratory frequency (f, breaths · min⁻¹), and tidal volume (ml). Heart rate (HR, beats · min⁻¹) was monitored using a telemetric system. Biomechanical variables included stride length (SL) and stride frequency (SF) recorded on a video tape. The results showed that the following variables were significantly higher (analysis of variance, P < 0.05) for TR than for CR: V˙O₂ [51.7 (3.4) vs 48.3 (3.9) ml · kg⁻¹ · min⁻¹, respectively], V˙ _E [100.4 (1.4) l · min⁻¹ vs 84.4 (7.0) l · min⁻¹], V˙ _E/V˙O₂ [24.2 (2.6) vs 21.5 (2.7)] V˙ _E/V˙CO₂ [25.2 (2.6) vs 22.4 (2.6)], f [55.8 (11.6) vs 49.0 (12.4) breaths · min⁻¹] and HR [175 (7) vs 168 (9) beats · min⁻¹]. Moreover, the time needed to reach steady-state was shorter for HR and V˙O₂ (1 min and 2 min, respectively) and longer for V˙ _E (7 min). In contrast, the biomechanical parameters, i.e. SL and SF, remained unchanged throughout TR versus CR. We conclude that the first minutes of the run segment after cycling in an experimental triathlon were specific in terms of V˙O₂ and cardiorespiratory variables, and nonspecific in terms of biomechanical variables. Accepted: 7 July 1997     

Effects of drafting behind a two- or a six-beat kick swimmer in elite female triathletes

The metabolic and drag responses, together with the distance between the draftee and the leader, were studied in six female triathletes swimming behind a lead swimmer who used either a two- or a six-beat kick, at an average velocity of 1.24 m · s⁻¹ (range 1.20–1.31). Drag was measured by passive towing. Oxygen consumption [49.1 (3.8) versus 50.4 (5.0) ml · min⁻¹ · kg⁻¹], blood lactate [6.7 (2.3) versus 6.8 (1.9) mM], heart rate [172 (13.6) versus 173.5 (12.5) beats · min⁻¹), rating of perceived exertion [13.7 (1.2) versus 13.5 (1.0)], stroke rate [38.3 (1.5) versus 39.5 (1.4) cycle · min⁻¹], stroke length [1.95 (0.09) versus 1.89 (0.15) m · cycle⁻¹] were not statistically different between the two-beat and the six-beat kick situations. The energy cost of swimming per unit of distance [0.65 (0.06) versus 0.67 (0.08) ml O₂ · m⁻¹] and the passive drag were similar for both kicks. The distance separating the draftee from the lead swimmer was between 14 cm and 85 cm and was inversely correlated with passive drag: r=−0.82,P < 0.05, for the two-beat kick and r=−0.82, P <  0.05, for the six-beat kick. The higher the passive drag, the closer the hand of the draftee to the feet of the lead swimmer. It was of no more benefit to triathletes to draft behind a two-beat kick swimmer than behind a six-beat kick swimmer. Accepted: 10 April 2000     

Specificity of treadmill and cycle ergometer tests in triathletes, runners and cyclists

The objective of this study was to evaluate the viability of using a single test in which cardiorespiratory variables are measured, to establish training guidelines in running and/or cycling training activities. Six triathletes (two females and four males), six runners (two females and four males) and six males cyclists, all with 5.5 years of serious training and still involved in racing, were tested on a treadmill and cycle ergometer. Cardiorespiratory variables [e.g., heart rate (HR), minute ventilation, carbon dioxide output (V˙CO₂)] were calculated relative to fixed percentages of maximal oxygen uptake (V˙O_2max; from 50 to 100%). The entire group of subjects had significantly (P < 0.05) higher values of V˙O_2max on the treadmill compared with the cycle ergometer [mean (SEM) 4.7 (0.8) and 4.4 (0.9) l · min⁻¹, respectively], and differences between tests averaged 10.5% for runners, 6.1% for triathletes and 2.8% for cyclists. A three-way analysis of variance using a 3 × 2 × 6 design (groups × tests × intensities) demonstrated that all factors yielded highly significant F-ratios (P < 0.05) for all variables between tests, even though differences in HR were only 4 beats · min⁻¹. When HR was plotted against a fixed percentage of V˙O_2max, a high correlation was found between tests. These results demonstrate that for triathletes, cyclists and runners, the relationship between HR and percentage of V˙O_2max, obtained in either a treadmill or a cycle ergometer test, may be used independently of absolute V˙O_2max to obtain reference HR values that can be used to monitor their running and/or cycling training bouts. Received: 3 November 1998 / Accepted: 29 July 1999     

Evaluation of spring-loaded cane ground reaction forces during walking using time and frequency domain analysis

Abstract

This study examined the effect of a spring-loaded cane stiffness reduction on upper and lower extremity ground reaction forces in time and frequency domain during cane-aided walking. Twenty-nine participants walked five times over two force plates with a spring-loaded cane set at four different stiffnesses and T-scope knee brace set at 30° of knee flexion to simulate a foot injury. Time–frequency domain analyses revealed an increase in ground reaction forces at the simulated injured foot and a decrease in ground reaction forces at the hand via the shaft of the cane for each spring loaded-cane stiffness reduction during walking. The results build on existing literature and highlight the use of spring-loaded canes, braking and propulsive ground reaction force measures, and frequency domain analysis to more accurately assess and monitor the rehabilitation and prevention of upper and lower extremity injuries during cane-aided walking.     

Effects of the order of running and cycling of similar intensity and duration on pulmonary diffusing capacity in triathletes

To study the pathophysiological mechanisms involved in the decrease of post-triathlon diffusing capacity (DLco), blood rheologic properties (blood viscosity: _b; changes in plasma volume: PV) and atrial natriuretic factor (ANF) were assessed in ten triathletes during cycle-run (CR) and run-cycle (RC) trials at a metabolic intensity of 75% of maximal oxygen consumption (O_2max). The DLco was measured before and 10 min after trials. ANF and PV were measured at rest, after the cycle and run of CR and RC trials, and at the end of and 10 min after exercise. RC led to a greater DLco decrease, a lower ANF concentration and a lower PV than did CR, whereas for both CR and RC _b was increased throughout exercise and 10 min after. In addition, after CR the DLco decrease was inversely correlated (r=–0.764; P<0.01) with PV. The association of decreased plasma volume, increased _b, and lower ANF concentrations after RC suggested that lower blood pulmonary volume may have caused the greater decrease in Dlco as compared with CR. The inverse correlation between PV and DLco reinforces the hypothesis that fluid shifts limit the post-exercise DLco decrease after the CR succession in triathletes. Lastly, cycling in the crouched position might increase intra-thoracic pressure, decrease thorax volume due to the forearm position on the handlebars, and weaken peripheral muscular pump efficacy, all of which would limit venous return to the heart, and thus result in low pulmonary blood volume. Compared with cycling, running appeared to induce the opposite effects.     

三种内固定方式固定胫骨平台后外侧骨折的生物力学研究

目的探讨胫骨平台后外侧骨折合理有效的内固定方式。方法制作成年男性尸体胫骨平台后外侧骨折模型12个,随机平均分为3组,分别使用前侧6.5 mm拉力螺钉、胫骨平台外侧L型4.5 mm解剖锁定钢板、后侧T型3.5 mm锁定钢板固定。对标本模型进行轴向加压250、500、750、1000 N,检测其轴向位移及应力。结果在相同应力下,前侧螺钉组轴向Y轴位移最小,分别与外侧钢板组和后侧钢板组存在显著差异,而外侧钢板组与后侧钢板组之间Y轴位移没有显著差异;前侧螺钉组在标识点的应力分布最为均衡。结论在胫骨平台后外侧骨折的固定中,前侧螺钉能够有效增加轴向稳定,骨折块周围应力分布均衡,是一种有效的力学固定方式,外侧钢板在横向的稳定性控制上具有一定优势,后侧钢板对于后方需要复位的平台骨折具有一定价值。     

The influence of lecithin on plasma choline concentrations in triathletes and adolescent runners during exercise

Summary An investigation was carried out on the effect of lecithin (phosphatidylcholine, 90%) on the plasma choline concentrations during continuous strain in 10 top level triathletes (4 women and 6 men), trial I, and 13 excellent adolescent runners (3 girls and 10 boys), trial II. Venous blood, collected before and immediately after the race, was separated and plasma was assayed by an improved high performance liquid chromatography method for choline. Each study comprised three experiments. In trial I the triathletes performed two periods of bicycle exercise each lasting 2 h at an average speed of 35 km · h^–1, and in the second study (trial II) the subjects were subjected to severe physical stress on two occasions during cross-country races of durations between 30–60 min according to their ages. The participants received either a placebo or 0.2 g lecithin · kg body mass^–1, 1 h before each exercise. As a control the same dose of lecithin was administered without any exercise (both trials I and II). Bicycle exercise without lecithin supply decreased plasma choline concentrations in all the triathletes, on average by 16.9% (P0.01). When lecithin was given before exercise, average plasma choline concentrations remained at the same level as the initial values. The supply of lecithin without exercise led to a significant increase of the plasma choline concentrations, on average by 26.9% (P0.01). In trial II, when running without a supply of lecithin, the mean plasma choline concentrations in the adolescent runners remained stable which may have been due to the duration of the physical stress. When lecithin was given before exercise, plasma choline concentrations increased, on average by 18.9% (P0.01). The administration of lecithin without exercise led in these participants to an increase in plasma choline concentrations, on average by 54% (P0.001).It was found from the present study that a combination of both lecithin intake and hard physical stress prevented in most subjects a decrease in plasma choline and this could affect performance.Presented in part at the Symposium: 29. Wissenschaftlicher Kongreß der Deutschen Gesellschaft für Ernährung (DGE), Stuttgart-Hohenheim (March 1992)     

等速肌力测试膝、踝关节及腰背肌力量的评价

背景：等速肌力测试已普遍用来作为运动员肌肉系统的机能状态和运动损伤的治疗效果评定的一种客观指标。 目的：探讨作为足球运动专项肌群的腰背肌、膝关节以及踝关节肌力特征。 方法：运用Cybex-Norm等速肌力测试与训练系统评价足球运动员在不同角速度下的膝、踝关节及腰背肌群屈伸肌峰力矩、相对峰力矩以及耐力水平。 结果与结论：运动员膝、踝关节左右两侧肌力发展较为均衡(< 5%),膝关节伸肌峰力矩和相对峰力矩偏低,屈肌峰力矩和相对峰力矩偏高,左侧膝关节表现尤为突出,不利于比赛时有效地控球、踢球和纵跳等动作的完成;腰背肌群相对峰力矩值相对较弱,容易在运动过程中发生损伤,引起下背痛类疾病;膝、踝关节以及腰背肌群的速度耐力水平均有较大提高空间。 中国组织工程研究杂志出版内容重点：组织构建;骨细胞;软骨细胞;细胞培养;成纤维细胞;血管内皮细胞;骨质疏松;组织工程     

Simulation of the influence of sports surfaces on vertical ground reaction forces during landing

In many biomechanical analyses, the vertical ground reaction force (GRF) is measured by force plates. However, if force plates are fixed on elastic surfaces, the force signals have low-frequency oscillations superimposed. The question arises, as to whether this oscillation results from the response of the athlete to the surface properties or from the fixation of the force plate on the elastic surface. For the simulation of the vertical GRF, a mechanical model was developed that combines three submodels representing the surface, the athlete and the force plate. The simulations were carried out for landings on concrete and wooden elastic surfaces, without and with the force plate, respectively. Comparison of the two surfaces showed that, on the elastic surface, the passive peak of the vertical GRF was lower and was reached later than on the concrete surface. Thus a lower force rate was possible during the landing on the elastic surface (concrete: 186 body weight per second; wooden: 164 body weight per second), which can reduce the risk of damaging the joint cartilage. The simulations also showed that the time course of the GRF was changed by a rippling effect when the force plate was fixed on the elastic surface. The rippling was not the result of a change in the athlete's movements, because the parameters of the athlete submodel were not changed. The rippling induced by the force plate hinders the analysis of the GRF time course involving the real peak force and the force rate.     

Region-specific differences in Achilles tendon cross-sectional area in runners and non-runners

The present study examined the cross-sectional area (CSA) of the Achilles tendon in subjects who repeatedly exposed their tendons to large loads (habitual runners) compared to control subjects (non-runners). Six male habitual runners [36 (7) years, 70.9 (4.4) kg and 1.84 (0.05) m, ±SD] who had performed distance running (~80 km per week) for the last 5 years were compared to six non-runners [34 (3) years, 81.2 (8.7) kg and 1.81 (0.02) m, ±SD]. Tendon CSA was obtained from MR images obtained with the ankle in a neutral position (90°). The most proximal aspect of the tuberosity of calcaneus was used as a landmark to standardize the levels of images: the most distal image (1) was obtained 10 mm above the proximal tuberosity of calcaneus, and the most proximal image (7) was obtained 70 mm above the proximal tuberosity of calcaneus. There was a significant difference in CSA along the length of the tendon both in runners (P<0.001) and non-runners (P<0.01). In non-runners and runners the CSA of the most distal part was 51% and 85% greater than the most proximal part of the tendon, respectively. Furthermore, there was a difference in tendon CSA between the groups, such that runners had a greater CSA (36%) than non-runners at the most distal part of the tendon (P<0.05). The greater CSA in the distal tendon may reflect differences in structural properties along the length of the human Achilles tendon, while the greater CSA in runners compared to non-runners may indicate a region-specific hypertrophy in response to the habitual loading of running.     

An algorithm to decompose ground reaction forces and moments from a single force platform in walking gait

In walking experimental conditions, subjects are sometimes unable to perform two steps on two different forceplates. This leads the authors to develop methods for discerning right and left ground reaction data while they are summed during the double support in walking. The aim of this study is to propose an adaptive transition function that considers the walking speed and ground reaction forces (GRF). A transition function is used to estimate left and right side GRF signals in double support. It includes a shape coefficient adjusted using single support GRF parameters. This shape coefficient is optimized by a non-linear least-square curve-fitting procedure to match the estimated signals with real GRF. A multiple regression is then performed to identify GRF parameters of major importance selected to compute the right and left GRF of the double support. Relative RMSE (RMSE_R), maximum GRF differences normalized to body mass and differences of center of pressure (CoP) are computed between real and decomposed signals. During double support, RMSE_R are 6%, 18%, 3.8%, 4.3%, 3%, and 12.3% for anterior force, lateral force, vertical force, frontal moment, sagittal moment and transverse moment, respectively. Maximum GRF differences normalized to body mass are lower than 1 N/kg and mean CoP difference is 0.0135 m, when comparing real to decomposed signals during double support. This work shows the accuracy of an adaptive transition function to decompose GRF and moment of right and left sides. This method is especially useful to accurately discern right and left GRF data in single force platform configurations.     

旋后外旋型踝关节损伤有限元模型的建立与力学分析

目的模拟旋后外旋型踝关节损伤,建立踝关节三维有限元模型。方法基于正常人体踝关节CT图像,建立包含韧带的踝关节三维数值模型;采用有限元方法对Lauge-Hanson分型4种不同程度的旋后外旋型踝关节损伤进行分析,得到踝关节应力及胫距关节面的压力分布。结果施加旋后外旋载荷时,应力最大值位于胫腓前韧带胫骨附着点;断裂胫腓前韧带后,则位于骨间膜;继续断裂骨间膜后,应力较大值位于踝关节后韧带;再断裂胫腓后韧带后,应力较大值位于三角韧带。压力较大值则位于腓骨远端、胫距下关节面后部。结论建立的踝足部三维数值模型可用于旋后外旋型踝关节损伤的的力学机理分析,计算出的踝关节应力及胫距关节面的压力分布符合临床中Lauge-Hanson分型的描述。     

可吸收螺钉与金属螺钉内固定修复踝关节骨折：生物相容性及踝关节功能比较

BACKGROUND: Previous ankle fracture surgery mainly uses the internal fixation materials such as metal screws or Kirschner wire, which can achieve a strong internal fixation, but all need to be taken out in the secondary surgery. In recent years, elastic modulus of biodegradable absorbable screw is identical to that of cancellous bone, and has been widely used in clinic.      

Withdrawal reflexes examined during human gait by ground reaction forces: site and gait phase dependency

The objective of this study was to investigate the modulation of the nociceptive withdrawal reflex during gait measured using Force Sensitive Resistors (FSR). Electrical stimulation was delivered to four locations on the sole of the foot at three different time points between heel-off and toe-off. Peak force changes were measured by FSRs attached to the big toe, distal to the first and fourth metatarsophalangeal joints, and the medial process of the calcaneus on both feet. Force changes were assessed in five gait sub-phases. The painful stimulation led to increased ipsilateral unloading (10 ± 1 N) and contralateral loading (12 ± 1 N), which were dependent on stimulation site and phase. In contrast, the hallux of the ipsilateral foot plantar flexed, thus facilitating the push-off. The highest degree of plantar flexion (23 ± 10 N; range, 8–44 N) was seen in the second double support phase following the stimulation. Site and phase modulation of the reflex were detected in the force signals from all selected anatomical landmarks. In the kinematic responses, both site and phase modulation were observed. For stimulations near toe-off, withdrawal was primarily accomplished by ankle dorsiflexion, while the strategy for stimulations at heel-off was flexion of the knee and hip joints.     

离体胫骨的有限元分析

应力骨折是士兵、运动员中很常见的骨损伤，被认为是疲劳骨折。首先测量了士兵在齐步、正步、跑步三种步态下承受的地面载荷，然后用有限元方法分析了在这几种步态下胫骨中的应力分布。结果表明：士兵三种步态下脚底的作用力从小到大依次为齐步，正步和跑步(例如，垂直作用力最大幅值分别为76kg，118kg和142kg)。在地面载荷作用下，胫骨中的应力分布是不均匀的。其最大值发生在膝下1／3处．正步和跑步时该处的应力水平分别为110MPa和115MPa。该处正是胫骨骨折临床最常见部位。这些结果给出了胫骨中的应力分布。证明了士兵胫骨应力骨折确是与其中应力水平密切相关的，载荷应力大者正是应力骨折发病率高者。     

新型胫骨交锁髓内钉对胫骨稳定性骨折治疗作用的生物力学研究

目的对新型动力加压胫骨交锁髓内钉用于胫骨稳定性骨折的生物力学性能进行对比研究,评价其在稳定性骨折治疗中的作用和力学性能优劣。方法对不同方式内固定用于胫骨稳定骨折的抗轴向压缩、抗侧弯、抗旋转生物力学性能进行测评和对比。结果新型髓内钉在轴向压缩载荷作用下表达出了优良的动力加压功能,其既有良好的抗短缩能力且应力遮挡低;各组试样的抗内→外弯曲能力较抗前→后弯曲能力强,新型髓内钉的抗侧弯性能优于髓内钉对照组,但次于加压钢板内固定;加压钢板内固定的抗旋转性能优于髓内钉内固定,新型髓内钉组较髓内钉对照组的抗旋转性能更优。结论新型胫骨髓内钉治疗稳定骨折的生物力学性能优越,可满足临床治疗需要;胫骨髓腔形态可对髓内钉抗侧弯性能表达产生重要影响。