An integrated biomechanical analysis of high speed incline and level treadmill running

PURPOSE: Recent sprint training regimens have used high-speed incline treadmill running to provide enhanced loading of muscles responsible for increasing forward running speed. The goal of this study was to document the joint kinematics, EMG, and swing-phase kinetics of incline treadmill running at 4.5 m x s(-1) with a 30% grade, and compare these data to that of level running under similar conditions. METHODS: Sagittal plane video (200 Hz) and EMG from eight lower extremity muscles were recorded during each of three locomotion conditions: incline running at 4.5 m x s(-1) and 30% grade (INC), level running at 4.5 m x s(-1) (LSS), and level running at the same stride frequency as INC (LSSF). A rigid body model was used to estimate net muscle power and work values at the hip, knee, and ankle during swing. Timing and amplitude of EMG signals for each muscle relative to footstrike were compared between conditions. RESULTS: Stride frequency and percentage of stride spent in stance were significantly higher during INC (1.78 Hz; 32.8%) than in the LSS (1.39 Hz; 28.8%) condition. Stride frequency played an important role, as most measures were more similar between INC and LSSF. Extensor range of motion of all joints during push-off was higher for INC. During INC, average EMG amplitude of the gastrocnemius, soleus, rectus femoris, vastus lateralis, and gluteus maximus were higher during stance, whereas the hamstrings activity amplitudes were lower. Average power and energy generated during hip flexion and extension in the swing phase were greatest during INC. CONCLUSIONS: These data suggest that compared with LSSF and LSS, INC provides enhanced muscular loading of key mono- and bi-articular muscles during both swing and stance phases.     

Running economy is impaired following a single bout of resistance exercise

The purpose of this study was to determine whether a low-volume high-intensity resistance training session influenced running economy during a subsequent aerobic treadmill run. Nine well trained distance runners (mean +/- SD; VO2max, 66.6 +/- 10.2 ml x kg(-1) x min(-1); weight, 65.8 +/- 10.2 kg; height, 173.4 +/- 7.8 cm; age 20 +/- 1.1 years) with resistance training experience performed treadmill running at two different speeds (0.56 m x sec(-1) and 0.20 m x sec(-1) below speed corresponding to lactate equilibrium) either rested or 1, 8 or 24 hours after a 50-minute whole body resistance training session. Running economy was assessed using open circuit spirometry while heart rate was recorded telemetrically. The contractile properties of the quadriceps femoris were also determined following each resistance training session and prior to each treadmill run using percutaneous electrical stimulation. Submaximal oxygen consumption was significantly increased one hour (2.6 +/- 2.3%, p= 0.007), and eight hours (1.6 +/- 2.5%, p= 0.032), but not 24 hours after resistance training. No significant differences were found in exercising heart rate, ventilation, respiratory exchange ratio, ratings of perceived exertion, or running mechanics. Peak twitch torque, time to peak torque, and half relaxation time of the quadriceps femoris were significantly reduced immediately following resistance training while peak twitch torque was also lower one hour following resistance training. Running economy following a resistance training session is impaired for up to 8 hours. This change was not paralleled by a concomitant change in exercising heart rate. The mechanism responsible for increased oxygen consumption following resistance training may be related to impairment of the force generating capacity of skeletal muscle, as there was a significant decrement in the contractile properties of the quadriceps femoris following resistance training.     

Submaximal aerobic running economy and treadmill performance in prepubertal boys

Although the determinants of running economy and its relationship to endurance performance have been evaluated in adults, little data are available in pediatric subjects. Twenty-eight prepubertal boys with diverse athletic abilities underwent progressive maximal treadmill testing. Running economy was defined as (1) VO2 at 9.6 kph and (2) VO2 expenditure for increasing running speed 1.6 kph (delta VO2). Treadmill running times ranged from 12.6 to 23.0 min. Mean VO2 at 6 mph was 48.7 m.kg-1.min-1 (SD 4.3) and delta VO2 averaged 6.8 m.kg-1.min-1 (SD 1.7). VO2max correlated closely to treadmill time. Treadmill endurance times were significantly related to running economy by both definitions; submaximal VO2 levels did not, however, correlate with maximal aerobic power. Delta VO2 was associated with stride frequency, but no other relationships were observed between economy and height, age, respiratory exchange ratio, ventilatory equivalent for oxygen, stride length: leg length ratio, or body surface area: mass ratio. These findings suggest that among older prepubertal boys, greater running economy is associated with superior treadmill endurance performance and that stride frequency may influence submaximal VO2 expenditure in children.     

Patterns of muscle coordination vary with stride frequency during weight assisted treadmill walking

Partial body weight-supported treadmill training is an approach for gait rehabilitation. Variables such as stepping frequency and the amount of body weight support are key parameters manipulated during training. The purpose of this study was to quantify the extent to which body weight support and stride frequency contribute and interact to produce the coordination patterns of the leg muscles. Principal components analysis was used to provide insight into the interaction effects of these factors on electromyographical (EMG) activity during treadmill locomotion. Eight healthy subjects walked on a treadmill at 15 different combinations of weight support (0%, 20%, 40%, 60%, 100%), and stride frequency (0.40, 0.49, 0.57 Hz). Treadmill walking was performed with the Lokomat robotic gait orthosis to constrain leg kinematics. Surface EMG data were collected from several lower limb muscles. Results indicate that much of the variance in EMG activity during treadmill locomotion can be attributed to the mechanics of the locomotor task imposed by the level of body weight support and stride frequency. We also showed that body weight support and stride frequency interact in different ways to affect muscle coordination patterns. EMG coordination patterns are similar between conditions of high levels of body weight support and faster stride frequencies vs. lower levels of body weight support and slower stride frequency. Our data suggest that the interaction of body weight support and stride frequency should be taken into consideration for optimizing motor output during locomotor training.     

The effect of wearing the complete Lenox Hill Derotation Brace on energy expenditure during horizontal treadmill running at 161 meters per minute

Ten volunteer subjects (means age = 26.6 +/- 4.9 years, means height = 177.9 +/- 5.6 cm, and means weight = 76.9 +/- 11.2 kg) who had been wearing the Lenox Hill Derotation Brace (LHB) for a mean time of 23.9 +/- 28.0 months were familiarized with horizontal treadmill running at 161 m/min with and without the LHB. They were then tested randomly for four runs, two with the LHB and two without the LHB. Metabolic measurements using a device that counted footstrikes on the treadmill were taken during the 3rd and 6th minutes of each run. Regardless of sampling time, wearing the LHB produced significantly higher values for VO2 (4.58%, P less than 0.025) and heart rate (5.10%, P less than 0.004) compared to the no brace condition. Regardless of whether or not the subjects were wearing the LHB, 6 minute values were significantly higher than 3 minute values for VO2 (5.89%, P less than 0.0004), VE (10.8%, P less than 0.004), heart rate (5.35%, P less than 0.0000), and R (2.17%, P less than 0.038). The mean 6 minute values of VO2 with (37.42 +/- 3.55 ml/kg/min) and without (35.54 +/- 2.17 ml/kg/min) the brace fall within the range of expected values of 28.1 to 39.3 ml/kg/min derived from regression equations from the literature which predict VO2 response to horizontal treadmill running. Mean stride lengths while wearing the LHB (97.85 cm) were not significantly different from mean stride lengths without the LHB (98.56 cm). It is concluded that wearing the LHB produces a 4.58% increase in energy expenditure during horizontal treadmill running at 161 m/min which cannot be attributed to changes in stride length or to time of sampling during the run.     

Effects of a capacitive-resistive electric transfer therapy on physiological and biomechanical parameters in recreational runners: A randomized controlled crossover trial

ObjectivesThis study compared the effects of a capacitive-resistive electric transfer therapy (Tecar) and passive rest on physiological and biomechanical parameters in recreational runners when performed shortly after an exhausting training session.DesignRandomized controlled crossover trial.SettingUniversity biomechanical research laboratory.ParticipantsFourteen trained male runnersMain outcome measuresPhysiological (running economy, oxygen uptake, respiratory exchange ratio, ventilation, heart rate, blood lactate concentration) and biomechanical (step length; stride angle, height, frequency, and contact time; swing time; contact phase; support phase; push-off phase) parameters were measured during two incremental treadmill running tests performed two days apart after an exhaustive training session.ResultsWhen running at 14 km/h and 16 km/h, the Tecar treatment group presented greater increases in stride length (p < 0.001), angle (p < 0.05) and height (p < 0.001) between the first and second tests than the control group and, accordingly, greater decreases in stride frequency (p < 0.05). Physiological parameters were similar between groups.ConclusionsThe present study suggests that a Tecar therapy intervention enhances biomechanical parameters in recreational runners after an exhaustive training session more than passive rest, generating a more efficient running pattern without affecting selected physiological parameters.     

Stride frequency and ventilation at constant carbon dioxide output.

To determine the consequences of two different stride frequencies on ventilation (VE) at similar levels of carbon dioxide production (VCO2), eleven male subjects performed two work tests on the treadmill. One test involved walking at a speed of 5 km/hr on a 15% grade while the other consisted of running on the treadmill at 9 km/hr on a 0% grade. Running increased stride frequency by 47%. The running and walking tests resulted in similar VCO2 levels, 1.85 +/- .18 and 1.9 +/- .20 l/min respectively, a non-significant difference. Ventilation during running was 43.73 +/- 6.51 l/min and during walking was 43.26 +/- 6.79 l/min, a non-significant difference. In addition the time constants for oxygen consumption (VCO2), VE and VCO2 were measured. The time constants for VCO2 and VE were not found to differ significantly during either the running or walking test. From our results, it can be seen that VE is more closely aligned to the metabolic state rather than stride frequency. In addition, the coupling of VE and VCO2 during the non-steady state is further indicative that ventilation is linked to the metabolic demands of the body.     

Effect of overground vs treadmill running on plantar pressure: Influence of fatigue

The differences produced when running on a treadmill vs overground may call into question the use and validity of the treadmill as a piece of equipment commonly used in research, training, and rehabilitation.The aim of the present study was to analyze under pre/post fatigue conditions the effect of treadmill vs overground on plantar pressures. Twenty-seven recreational runners (17 men and 10 women) ran on a treadmill and overground at two speeds: S₁ = 3.33 m/s and S₂ = 4.00 m/s, before and after a fatigue protocol consisting of a 30-min run at 85% of their individual maximal aerobic speed (MAS). Contact time (CT in seconds), peak pressure (PP in kPa), and relative load (RL in %) were analyzed under nine foot zones of the left foot using an in-shoe plantar pressure device.A two-way repeated measures ANOVA showed that running on a treadmill increases CT (7.70% S₁ and 9.91% S₂), modifies the pressure distribution and reduces PP (25.98% S₁ and 31.76% S₂), especially under the heel, medial metatarsals, and hallux, compared to running overground. Moreover, on both surfaces, fatigue (S₂) led to a reduced stride frequency (2.78%) and reduced PP on the lateral heel and hallux (15.96% and 16.35%, respectively), and (S₁) increased relative load on the medial arch (9.53%). There was no significant interaction between the two factors analyzed (surface and fatigue). Therefore, the aforementioned surface effect, which occurs independently of the fatigue state, should be taken into account when interpreting the results of studies that use the treadmill in their experimental protocols, and when prescribing physical exercise on a treadmill.     

The effects of resisted sled-pulling sprint training on acceleration and maximum speed performance

AIM: The purpose of the present study was to examine the effects of resisted (RS) and un-resisted (US) sprint training programs on acceleration and maximum speed performance. METHODS: Twenty-two male students (age 20.1+/-1.9 y, height 1.78+/-7 cm, and weight 73+/-2 kg) completed RS (n=11) or US (n=11) sprint training programs. The RS group followed a sprint-training program with 5 kg sled pulling and the US group followed a similar sprint-training program without sled pulling. The training program consisted of 4x20 m and 4x50 m maximal runs, and was applied 3 times/week for 8 weeks. Before and after the training programs the subjects performed a 50 m run and the running velocity of 0(-1)0 m, 10(-2)0 m, 20-40 m and 40-50 m was measured. In addition, stride length and stride frequency were evaluated at the 3(rd) stride in acceleration phase and between 42-47 m in maximum speed phase. RESULTS: The RS improved running velocity in the run sections 0(-1)0 m and 0(-2)0 m, while in US group the running velocity in all run sections in acceleration phase remained unchanged (p>0.05). In contrast, RS training had no effect on running velocity in maximum speed phase, whereas US improved running velocity in 20-40 m, 40-50 m, and 20-50 m run sections (p<0.05). Stride rate increased only after RS in acceleration phase (+7.1+/-2.9%; p<0.05), whereas stride length increased only after US in maximum speed phase (+5.5+/-2.5%; p<0.05). CONCLUSION: Sprint training with 5 kg sled pulling for 8 weeks improves acceleration performance (0(-2)0), while un-resisted sprint training improves performance in maximum speed phase (20-40) in non-elite athletes. It appears that each phase of sprint run demands a specific training approach.     

The effects of treadmill or overground walking training program on gait in Parkinson's disease

BackgroundGait impairment in Parkinson's disease (PD) patients is characterized by the inability to generate appropriate stride length. Treadmill training has been proposed as a therapeutic tool for PD patients. However, it remains unknown whether treadmill training effects are different from overground walking training. Thus, our goal was to explore the effects of two training programs, walking on a treadmill and walking overground, in PD patients.Methods22 PD patients were randomly assigned to a treadmill or overground training group. The training program consisted of 5 weeks (3 sessions/week). Before and after the program we evaluated gait kinematics during walking at preferred and maximal speed; Timed Up and Go (TUG); static posturography and knee extensors strength. Gait parameters were reevaluated in the treadmill training group one month after the cessation of the training.ResultsPreferred speed walking improved in both groups after the training program. The treadmill training program, but not the overground, led to an improvement in the stride length at the preferred and maximal walking speed in the PD patients. In addition, the treadmill training group showed improvement of the TUG and static posturography tests. The improvement in gait parameters was maintained one month after the cessation of the treadmill training.ConclusionsThis study provides evidence of a specific therapeutic effect of treadmill training on Parkinsonian gait and balance. Walking on a treadmill may be used as an easy, effective and accessible way to improve the stride length and balance in PD patients.     

Reliability of the fluctuations within the stride time series measured in runners during treadmill running to exhaustion

BackgroundThe fluctuations within stride time series (i.e., stride time variability and complexity) during running exhibit long-range correlation. Detecting the breakdown of the long-range correlation was proposed for monitoring the occurrence of running-related injuries during running. However, the stride time fluctuations were only measured from the unilateral side. In addition, the reliability of the stride time fluctuations of within-subject repeated measures remains largely unknown, particularly during exhaustive running.PurposesThis study investigated between-side and between-day reliabilities of the stride time variability and complexity of right and left sides during an exhaustive running.MethodsThe stride time variability and complexity of bilateral sides were obtained while 24 healthy participants performed a 31-minute treadmill running at their individual anaerobic threshold speed. Seven of the 24 participants performed the treadmill running test twice at two different days 5–7 days apart. Limits of agreement (LoA) and intraclass correlation coefficient (ICC) were respectively used to assess the absolute and relative between-side and between-day reliabilities.ResultsThe stride time variability and complexity of right and left sides were highly symmetrical (LoA: (-0.500%, 0.459%) and (-0.052, 0.051), respectively; ICC: 0.94 (0.87, 0.97) and 0.98 (0.95, 0.99), respectively). The overall stride time variability and complexity revealed good between-day reliability (LoA: (-1.044%, 0.724%) and (-0.067, 0.115), respectively; ICC: 0.78 (0.45, 0.92) and 0.81 (0.48, 0.93), respectively). However, the segmented stride time complexity showed poor between-day reliability (ICCs<0.40).ConclusionThe findings demonstrated that the stride time series showed equivalent fluctuations between right and left sides and good between-day reliability in fluctuations during exhaustive running. Given the poor between-day reliability in the segmented stride time series, stride time series during exhaustive running could be collected from either right or left side and should be processed as an overall in the future.     

Treadmill walking alters stride time dynamics in Parkinson’s disease

BackgroundTreadmill training may be used to improve gait rhythmicity in people with Parkinson’s disease. Treadmills, however, alter dynamical stride time fluctuations in healthy adults in a manner that mimics pathologic states, indicating the stride-to-stride fluctuations that characterize healthy gait are constrained. It is unclear if treadmills similarly alter dynamic gait properties in Parkinson’s disease.Research questionDo stride time fractal dynamics in individuals with Parkinson’s disease differ between treadmill and overground walking?MethodsFifteen participants with Parkinson’s disease and 15 healthy age-similar adults walked for 6 min in a conventional overground condition and on a treadmill while wearing inertial measurement units. Gait speed, stride times and stride time variability were measured. Fractal exponents (α) were computed with adaptive fractal analysis. Inferential statistics were analyzed with mixed model analyses of variance and post hoc simple effects tests.ResultsMean gait speeds decreased and stride times increased on the treadmill but did not differ between the Parkinson’s and control groups. Stride time variability was greater in the Parkinson’s than control group in both conditions. Most relevant to our research question, stride time fractal exponents were greater on the treadmill (mean α = .910) than overground (mean α = .797) in individuals with Parkinson’s disease, but not in healthy controls.SignificanceThe fractal scaling exponent α emanating from stride time fluctuations during treadmill walking increased toward a 1/f signal of α = 1.0 that has been interpreted as an optimal structural variability for gait. The clinical implication is that treadmill training may promote more efficient walking dynamics in people with Parkinson’s disease than conventional overground training.     

Kinematical Analysis of Underwater Walking and Running

The purpose of this study was to determine kinematical characteristics of underwater locomotion and to compare them with those of land locomotion. Six male subjects performed walking and running on both conventional and underwater treadmills. Both treadmill speeds increased incrementally starting from 0.56 m s 1 to 3.33 m s 1, the maximum speed of the underwater treadmill. The motion analysis showed that underwater locomotion is characterized by the following points: (a) A transition from walking (1.11 m s 1) to running occurs at a lower speed in water; (b) stride frequency is significantly lower in water; (c) in order to reduce the hydrodynamic resistance of water, a greater knee joint flexion is used to reduce the trajectory area enclosed by the legs as the treadmill speed is increased; and (d) many kinematical differences were observed above a walking speed of 1.11 m s 1, also above this speed oxygen uptake was significantly higher in water. In water, the strategy of locomotion is quite different from that on land.     

不同跑步速度训练大鼠肌肉细胞凋亡的初步实验研究

本研究旨在观察运动训练中肌肉细胞是否会出现细胞凋亡 ,并为进一步开展细胞凋亡在运动训练导致运动疲劳与运动损伤中的应用研究而建立动物速度训练模型。雄性 2月龄SD大鼠随机分为 6组 ,在经历两个月的训练后 ,分别按 0m/min(安静 )、1 8m/min、3 0m/min、42m/min、5 4m/min和 66m/min的速度在跑台上跑步 3min ,即刻断头取股四头肌 ,做冰冻切片处理。股四头肌冰冻切片进行能对凋亡细胞特异染色的脱氧核糖核苷酸末端转移酶介导的缺口末端标记 (TUNEL)法染色和组织学之苏木精—伊红(HE)染色。在荧光显微镜下观察TUNEL染色的股四头肌冰冻切片 ,发现在运动各组均有散在的标记细胞核 ;在HE染色片中 ,可以观察到与TUNEL染色呈阳性核之肌细胞的显微结构未发生明显变化 ,但出现细胞核染色质浓缩、靠近核膜、核膜增厚等现象。这些结果表明在运动训练中出现了肌肉细胞凋亡的现象。此外 ,在本实验设计的 5个速度组中 ,凋亡的肌细胞出现率略呈随跑速增加而增高的趋势。用膜脂质过氧化的最终产物丙二醛 (MDA)作为指标 ,检测氧自由基的作用 ,发现各运动组MDA值均比安静组略有增加 ,各运动组之间MDA值接近 ,但无统计学差异 ;另一方面 ,MDA值与细胞凋亡出现率一样有随运动强度增加而增高的趋势。结果提示 ,运动训练可以     

Reproducibility of electromyography and ground reaction force during various running techniques

This study examined the validity of the assumption of electromyographic (EMG) and vertical ground reaction force (GRF) parameter reproducibility during running at different velocities and stride frequencies. Each of 12 female long distance runners ran on a treadmill in combinations of three velocities (2.5, 3.0 and 3.5 m/s) and three stride frequencies (preferred, +/-10% from preferred). Seven parameters from the GRF and five parameters from the EMG signals from five muscles of the lower extremity were evaluated (1000 Hz). The GRF was analysed by a pressure measuring insoles. A total number of three trials for each running condition were recorded. GRF parameters during all running conditions showed high intraclass correlation coefficients (ICC average 0.87). The ICC of the EMG parameters of gastrocnemius medialis and lateralis were high (r>0.69 in 73% of the data), while those for vastus lateralis (22%), hamstrings (42%) and tibialis anterior (51%) were clearly lower. The results revealed that GRF parameters were reproducible during all running techniques indicating that a single trial would provide reproducible GRF-data. The reproducibility of the EMG parameters was not influenced by the running technique but dependent on the parameter itself and on the muscle studied.     

Difference in mechanical and energy cost between highly, well, and nontrained runners

INTRODUCTION: Recently it has been shown that endurance training decreases the variability in stride rate. This decrease would lead to a reduction in the mechanical and the energy cost of running. PURPOSE: This study therefore aimed to compare the mechanical and the energy cost of running according to the training status of the runner (highly, well, and nontrained endurance runners). METHODS: The kinetic, potential, and internal mechanical costs (Cke, Cpe, and Cint) were measured with a 3D motion analysis system (ANIMAN3D). The energy cost of running (C) was measured from pulmonary gas exchange using a breath-by-breath portable gas analyser (Cosmed K4b2, Rome, Italy). All the parameters were measured on track, for a speed of 4.84 +/- 0.36 m x s(-1). RESULTS: Highly trained runners did not exhibit significantly lower C compared with well or nontrained runners (4.46 +/- 0.38; 4.33 +/- 0.32; 4.46 +/- 0.46 J x kg(-1) x m(-1), respectively; P = 0.75). However, Cpe was significantly lower in highly and well-trained runners compared with nontrained runners (0.43 +/- 0.07; 0.45 +/- 0.05; 0.54 +/- 0.08 J x kg(-1) x m(-1), respectively; P < 0.05). In contrast, Cint was significantly higher in highly trained runners compared with well and nontrained runners (respectively, 0.80 +/- 0.12; 0.60 +/- 0.09; 0.59 +/- 0.10 J x kg(-1) x m(-1); P < 0.05). CONCLUSION: Although there is a significant difference in Cpe and in Cint between runners of various training status, there is no difference in C. Differences in Cpe and Cint may be associated with the same self-optimizing mechanism that contributes to a reduction in the impact loads during the initial portion of the support phase of the stride.     

Biomechanical analysis of sprinting: decathletes versus champions.

The purpose of this study was to compare some biomechanical variables of decathletes and world class sprinters while running the 100 metre race. Sixteen Swiss national decathletes and three world class American sprinters were filmed by a 16 mm Locam (100 fps) camera at the 70 m mark of the race. The co-ordinates for a 26-point stick figure were digitised and then submitted to analysis by a computer programme which produced quantitative data for 12 biomechanical variables. The data indicated that world-class sprinters differed from decathletes in running the 100 m dash by having (1) an optimal combination of a larger stride length and higher stride frequency (2) a smaller thigh angle at contact which shortens the contact time (3) a larger stride landing angle (4) a greater average acceleration of the thigh angle was (5) a larger trunk angle which contributes to a larger trunk/thigh angle. Although other factors such as culture, training, physique and racial differences may influence differences in performance between American world-class sprinters and Swiss decathletes, these data do indicate that biomechanical variables may contribute to differences in 100 m dash performance.     

Running economy: changes with age during childhood and adolescence.

The purpose of this study was to synthesize work directed at describing and understanding changes in running economy (the steady-state demand for oxygen at a set running speed) that occur with increased age during childhood and adolescence. Although the data are limited, a number of tentative conclusions were drawn. Children are less economical than adults. Running economy improves steadily with age in normally active children and adolescents, even in the absence of formal running training. Running economy in later childhood fails to respond to either short-term instruction on the techniques of running or short-term participation in running training. Long-term participation in running training may augment improvements in running economy that occur naturally with age. In a group of heterogeneous subjects of the same age, running economy is not strongly related to performance. Within a subject over a period of years, running economy is strongly related to performance. Children are less economical than adults because when compared with adults, children exhibit (a) higher resting metabolic rates, (b) greater ventilatory equivalents for oxygen, and (c) disadvantageous stride rates and stride lengths.