An inverse method for deriving structural modification of a subsystem based on changes in mechanical energy to allocate multiple resonant frequencies

The purpose of this study was to investigate mechanical energy changes during treadmill running, using two biomechanical models of the human body: the multi-segment model and the center of mass model. Two university distance runners ran at 3.33 and 2.67 m/s on the treadmill, while the right side was filmed by a 16-mm high-speed movie camera (100 fps). The instantaneous mechanical energies of the multi-segment model composed of 11 rigid segments (ME total) and those of the C.M. model (ME C.M.) were calculated for two strides for each trial. The following results were obtained: the trunk segment was the major contributor to the body energy variations, compared to the four limbs; internal kinetic energy, which was the difference between the energy amounts of the two models, was found to have a phase relationship directly opposite to those of the C.M. model. These findings were contrary to the previous studies on walking and were seen to be important characteristics of running energetics.

The aim of the study was to assess energy cost and total external work (total energy) depending on the speed of race walking. Another objective was to determine the contribution of external work to total energy cost of walking at technical, threshold and racing speed in elite competitive race walkers.The study involved 12 competitive race walkers aged 24.9 4.10 years with 6 to 20 years of experience, who achieved a national or international sports level. Their aerobic endurance was determined by means of a direct method involving an incremental exercise test on the treadmill.The participants performed three tests walking each time with one of the three speeds according to the same protocol: an 8-minute walk with at steady speed was followed by a recovery phase until the oxygen debt was repaid. To measure exercise energy cost, an indirect method based on the volume of oxygen uptake was employed. The gait of the participants was recorded using the 3D Vicon opto-electronic motion capture system.Values of changes in potential energy and total kinetic energy in a gate cycle were determined based on vertical displacements of the centre of mass. Changes in mechanical energy amounted to the value of total external work of muscles needed to accelerate and lift the centre of mass during a normalised gait cycle.The values of average energy cost and of total external work standardised to body mass and distance covered calculated for technical speed, threshold and racing speeds turned out to be statistically significant (p0.001).The total energy cost ranged from 51.2 kJ.m-1 during walking at technical speed to 78.3 kJ.m-1 during walking at a racing speed. Regardless of the type of speed, the total external work of muscles accounted for around 25% of total energy cost in race walking. Total external work mainly increased because of changes in the resultant kinetic energy of the centre of mass movement.

Analysis of mechanical energy in thigh, calf and foot during gait in children with cerebral palsy

Ability of the planar spring–mass model to predict mechanical parameters in running humans

Knowing how to enhance alpine skiing performance is essential for effective coaching. The purpose of this study was to explore the role of path length- and speed-related factors for performance enhancement, while skiing on a homogeneously set/constantly inclined giant slalom course section (average gate distance: 27 m; offset: 8 m; slope inclination: 26°). During a video-based three-dimensional kinematic field-experiment, the data of six athletes who skied a two-gate section on four different types of skis were collected. The performance parameter analysed was section time. The performance predictors analysed were centre of mass (CoM), path length and the change in specific mechanical energy per entrance speed along the analysed section. Furthermore, since the current study examined alpine skiing performance within short sections, the skier’s entrance speed was also considered. Classified as a high-performance and a low-performance group based on section time, slow and fast trials significantly differed in CoM path length, the change in specific mechanical energy per entrance speed and entrance speed. The entrance speed of all trials analysed ranged between 15.25 and 17.66 m/s. In trials with both high and low entrance speed, the change in specific mechanical energy per entrance speed was found to be more relevant for the prediction of section time than CoM path length. However, further studies should investigate whether such a prioritization can be unrestrictedly generalized to other situations, such as entrance speeds, course sets, slope inclinations and competition disciplines different to those assessed in the current study.

PURPOSE: The purpose of this study was to examine the relationship between changes in total mechanical energy (ME) and oxygen consumption during treadmill running in the severe intensity domain. METHODS: Seven subjects (3 males, 4 females) volunteered for this study (mean age ±SD = 25.4 ± 2.5 yrs; mass = 66.6 ±7.0 kg). After a separate familiarization session, subjects performed an incremental treadmill test to exhaustion (1% grade, speed increment = 0.5 mph per minute) from which the ventilatory threshold, respiratory compensation threshold, and peak VO2 were determined. On a subsequent day, subjects performed a constant speed treadmill run at a speed above the respiratory compensation threshold but below the speed at VO2 peak. During this run, gas exchange data was continuously recorded. In addition, 3-D kinematic data was captured over a 10 second epoch every 30 seconds using an 8-camera Motion Analysis system at 120 Hz. The total ME was calculated using the no transfer approach for a 13 segment anthropometric model. The total ME was calculated for each epoch was normalized to J/kg/m. After removing the first minute of the run data, both VO2 and ME were regressed against time within each subject. The slopes of the individual regressions were analyzed by constructing 95% confidence intervals around the mean slopes. In addition, the correlation between the VO2 and ME slopes was calculated. RESULTS: The mean ME slope was .0093 + 0.04 J/kg/m per min (95% CI = −0.26 − 0.045) and the mean VO2 slope was 74.3 + 94.8 mlO2 per min (95% CI = −13.4 - 161.9). The correlation between the ME and VO2 slopes was negative (r=−0.75, p =0.03), although was likely driven by the leverage associated with one subject with both the largest VO2 slope and the most negative ME slope. CONCLUSIONS: The results do not support the hypothesis that increases in oxygen consumption during severe intensity running at a constant speed are driven by changes in total mechanical energy.

One of the key features that enables animals and humans to perform agile, robust, adaptive yet ef- ficient locomotion is their body’s complex muscle-tendon-ligament system. Such systems provide body and limbs with the functionality that is used to efficiently absorb external shocks and ex- change of mechanical energy, e.g. kinetic and potential energy, to exploit natural dynamics during locomotion. In biology, it has been found that animals and humans adjust their limb stiffness to ac- commodate for different speeds, gaits, and terrains. On contrary, in the field of legged robots, little has been known about how to control leg stiffness to efficiently adapt to changes of speed, terrain, and gait or stride frequency at which the leg oscillates. Therefore, this thesis aims at contributing to the primary understanding of the topic. Until today, mechanical springs with fixed spring constants are still widely used as energy sav- ing mechanisms and shock absorbers for legged robots. However, the compliance of those springs is not adjustable and manual assembly is required to make a robot leg stiffer or more compliant. Motivated by this fact, we present a systematic development and evaluation of a new variable compliance/stiffness actuator, named MESTRAN (MEchanism to vary Stiffness via Transmission ANgle) in this thesis. This actuator serves as a key tool to investigate energy efficient locomotion at various stride frequencies and on surfaces with different stiffness. MESTRAN can dynamically alter joint stiffness in an unlimited range. It is also capable of maintaining the stiffness without requiring energy and offering different types of compliance, e.g. linear, quadratic, or exponential. In this thesis, we first designed and constructed an adjustable stiffness leg based on the MES- TRAN design. We then validated the design by conducting a series of experiments by using the first leg prototype. Second, in order to investigate hopping locomotion with variable stiffness ca- pability, we designed a single-legged robot, named L-MESTRAN (Linear-MESTRAN), which is an advanced version of the MESTRAN leg. We systematically analysed and demonstrated the me- chanical performance of the legged robot using the simulations and a number of real-world hop- ping experiments. As a result, we found that a proper adjustment of leg stiffness can improve the hopping energy efficiency of the robot at various stride frequencies. Third, this finding was also investigated on surfaces with different stiffness by using the L-MESTRAN robot. The simulation and experimental results indicated that, for a particular stride frequency (3 - 6 [Hz]), the adjust- ment of the knee stiffness can accommodate for changes in surface compliance, resulting in an improvement of the energy efficiency of hopping

The purpose of the present study was to gain more insight into the contribution of the forelimbs and hindlimbs of the horse to energy changes during the push-off for a jump. For this purpose, we collected kinematic data at 240 Hz from 23 5-year-old Warmbloods (average mass: 595 kg) performing free jumps over a 1.15 m high fence. From these data, we calculated the changes in mechanical energy and the changes in limb length and joint angles. The force carried by the forelimbs and the amount of energy stored was estimated from the distance between elbow and hoof, assuming that this part of the leg behaved as a linear spring. During the forelimb push, the total energy first decreased by 3.2 J kg(-1) and then increased again by 4.2 J kg(-1) to the end of the forelimb push. At the end of the forelimb push, the kinetic energy due to horizontal velocity of the centre of mass was 1.6 J kg(-1) less than at the start, while the effective energy (energy contributing to jump height) was 2.3 J kg(-1) greater. It was investigated to what extent these changes could involve passive spring-like behaviour of the forelimbs. The amount of energy stored and re-utilized in the distal tendons during the forelimb push was estimated to be on average 0.4 J kg(-1) in the trailing forelimb and 0.23 J kg(-1) in the leading forelimb. This means that a considerable amount of energy was first dissipated and subsequently regenerated by muscles, with triceps brachii probably being the most important contributor. During the hindlimb push, the muscles of the leg were primarily producing energy. The total increase in energy was 2.5 J kg(-1) and the peak power output amounted to 71 W kg(-1).

The aim of the research was to determine the energy changes during the gait cycle for a group of healthy children and a group of patients with cerebral palsy, and to compare the value of energy expenditure (EE) with the determined values of the Gillette Gait Index (GGI) and the Gait Deviation Index (GDI). The study group consisted of 56 children with regular gait and 56 patients with diagnosed cerebral palsy (CP). The gait kinematics was determined by BTS Smart System. Based on the identified position of the body mass, the following parameters were determined: the potential energy, kinetic energy, and total energy. The values were standardized to 100% of the gait cycle. The values of the Gillette Gait Index (GGI) and the Gait Deviation Index (GDI) were calculated using the authors' own software. Values of potential, kinematic and mechanical energy changes and mean values of total energy (energy expenditure - EE) were calculated for a reference group and for patients with CP. The obtained results were standardized in relation to the body mass and stride length. Furthermore, the values of the Gillette Gait Index (GGI) and the Gait Deviation Index (GDI) were calculated. Statistical analysis of the obtained results was performed. The Spearman rank correlation coefficient was defined between the calculated GGI and GDI values and energy expenditure EE. Values of energy expenditure changes can be used as an objective comparative tool for gait results concerning children with various neurological and orthopaedic dysfunctions.

The aim of the study was to assess the influence of year-long training of race walkers on physiological cost and total energy center of mass (CoM). The assessment performed was based on indicating the differences between the resulting energy cost in a group of elite race walkers walking at technical, threshold, and racing speeds calculated by physiological and biomechanical methods before beginning and after finishing a year-long training cycle. The study involved 12 competitive race walkers who had achieved champion or international champion level. Their aerobic endurance was determined by means of a direct method, applying an incremental exercise test on the treadmill. The gait of the participants was recorded using the 3D Vicon analysis system. Changes in mechanical energy amounted to the value of the total external work of the muscles needed to accelerate and lift the center of mass during a normalized gait cycle. The highest influence on the total external work increase for increasing speeds of gait in both examinations was attributed to the changes in the kinetic energy resulting from the center of mass movement. A statistically significant decrease of the mean value of total external work for racing speed was observed in the second examination (p < 0.001). An approx. 8% decrease (NS) of EE energy cost, standardized by body mass and distance covered, was found between the first and second examinations. The energy cost and total external work were significantly differentiated by the walkers’ gait speeds (p < 0.05–0.001). The energy cost significantly differed from the total external work at p < 0.001.

Although many variables influence the melt quality of finished processed cheese, this investigation focused on mechanical and thermal energy transport involved during the creaming process. To simulate commercial processing, a pilot scale 10‐gallon (0.04m3), dual ribbon blender was equipped with a thermal control system and a 0.75 hp (559.27 W) electrical motor. An experimental design consisted of three temperatures (75, 80, 85C), three mixing rates (50, 100,150 RPM), and six durations (1, 5, 10, 15, 25, 35 min). Quantified process variables included: process strain and thermal history, and total, instantaneous, and change in mechanical energy. The Schreiber melt test was used to examine the relationship between the processing parameters and melt performance. A statistical analysis revealed significant parameter estimates (P < 0.0001) for each quantified variable in a general linear model. The process cheese industry will gain insight into controlled manufacturing conditions to deliver desired melt functionality.

BackgroundKnee replacement surgeries are used to reduce pain and enhance functionality for individuals with knee arthritis. It is predicted that the annual volume of total knee replacement surgeries conducted in the US will surge by a substantial 673% by 2030. Though a lot of studies have done gait analysis on patients with knee replacement, little research is on energy changes in the lower limbs during gait. This study aimed to investigate the mechanical energy changes in the lower limbs for patients with total knee arthroplasty (TKA) and unicondylar knee arthroplasty (UKA), and ultimately to provide a specific tool to analyze limb energy during gait in clinical practice. Methods10 TKA and 8 UKA patients were recruited for gait analysis. The control group consisted of 11 individuals without knee replacement surgery. Vicon motion capture system and Plug-in-Gait model were used to collect gait data to obtain marker coordinates and gait parameters. The kinetic energy, potential energy, and rotational energy for each segment in the lower limbs were calculated. The energies in the centre of pelvis were considered as the approximate to the centre of mass. The energy recovery coefficients were analysed for each segment during gait. SPSS was used to identify the differences between different groups. ResultsThe results showed that during walking, the upper leg had the highest recovery coefficient, approximately 40%, followed by the foot at 10%, and the lowest recovery coefficient was observed in the lower leg, approximately 1–3%. However, the energy recovery coefficients at the centre of pelvis were significantly higher in the control group than the TKA and UKA groups by roughly 12%–15%. ConclusionsThe energy difference between the operative and non-operative sides is not significant regardless of the type of surgery. The TKA and UKA groups were more active in potential energy than control group. The upper leg has the highest recovery efficiency of kinetic and potential energy exchanges when walking. The control group used the energy for whole body is better than the patient groups. This study provides a new and useful way to analyze mechanical energy in the lower limbs during gait and could be applied in clinical practice.

The relationship between the oxygen cost of running at submaximal speeds and running mechanics was investigated in a group of trained athletes by means of an energy analysis. Subjects were filmed while running on a motorized treadmill at speeds of 3.58, 4.02, 4.47, 4.92, 5.36, and 5.81 m/s. Segmental potential and kinetic energies were determined using a three-dimensional link-segmental model. Intra-stride changes in the energy of the whole body were computed with no allowance for energy transfer and with various energy transfer constraints imposed on the model. Oxygen consumption was determined by expired air analysis and used to estimate energy expenditure. For each transfer condition, net energy expenditure was more highly correlated with the magnitude of intra-stride energy changes than with running speed per se. The more economic running patterns were characterized by greater within-segment energy transfers. Given the limitations of the kinematic energy model, it is suggested that individual patterns of running are a significant factor in the determination of energy expenditure.

The efficiency of human gait has been the subject of comment and speculation for some time. Biomechanically it has been shown that there are passive energy exchanges within body segments and between adjacent segments. The purposes of this paper were to measure and calculate how much of the segment energy changes can be attributed to muscular activity versus these passive exchange mechanisms, and to calculate the mechanical efficiency of overground walking based on the internal mechanical work. Six male subjects, matched for age, height and weight, were analysed during level treadmill walking at an average velocity of 1-54 -1 and a step length of 0-79m using an 11 segment planar biomechanical model. It was determined that the rate of doing internal work, both positive and negative, was about 165 W although the total observed work rate was 500 W. The rate of passive energy exchange within and between segments was 335 W. These results indicate that about two-thirds of the observed mechanical energy changes a...

Mechanical energy generation, absorption and transfer amongst segments during walking