oscillation-reaction-board-techniques-for-estimating-inertial

Oscillation and Reaction Board Techniques for Estimating Inertial Properties of a Below-knee Prosthesis

The purpose of this study was two-fold: 1) demonstrate a technique that can be used to directly estimate the inertial properties of a below-knee ...

Iowa State University

The purpose of this study was to document age-related changes in walking V(O(2)) in able-bodied boys and girls. Beginning at age 6 and ending at age 10, 23 children (14 girls, 9 boys) performed six 5-min bouts of level treadmill walking at 0.67, 0.89, 1.12, 1.34, 1.56, and 1.79 m s(-1) on an annual basis. Prior to data collection, subjects received 60 min of treadmill walking practice. During the last 2 min of each walking bout, a 2-min sample of expired air was collected in a meteorological balloon and analyzed to determine V(O(2)). Averaged across age, interindividual variation in V(O(2)) ranged from 32 to 41%. Repeated-measures analysis of variance demonstrated a speed by age interaction for V(O(2)), such that mean V(O(2)) rose (P< or = 0.05) across the five fastest speeds for 6-, 7-, 8-, and 10-year olds and increased over the entire speed range for 9-year olds. For all speeds, V(O(2)) decreased yearly from the ages of 6 to 8. When averaged across speeds, V(O(2)) was 27% higher for 6-year olds compared with 10-year olds. From a clinical perspective, access to longitudinal measurements of walking V(O(2)) in able-bodied children should be helpful in interpreting gait energy use in children with movement disorders and evaluating treatment strategies designed to reduce the aerobic demand of locomotion in youth with impaired mobility.

Longitudinal profiles of oxygen uptake during treadmill walking in able-bodied children: the locomotion energy and growth study.

The purpose of this study was to develop a generalized equation to predict VO2 during level treadmill walking in young boys and girls.

Prediction of the aerobic demand of walking in children.

A model of muscle energy expenditure was developed for predicting thermal, as well as mechanical energy liberation during simulated muscle contractions. The model was designed to yield energy (heat and work) rate predictions appropriate for human skeletal muscle contracting at normal body temperature. The basic form of the present model is similar to many previous models of muscle energy expenditure, but parameter values were based almost entirely on mammalian muscle data, with preference given to human data where possible. Nonlinear phenomena associated with submaximal activation were also incorporated. The muscle energy model was evaluated at varying levels of complexity, ranging from simulated contractions of isolated muscle, to simulations of whole body locomotion. In all cases, acceptable agreement was found between simulated and experimental energy liberation. The present model should be useful in future studies of the energetics of human movement using forward dynamic computer simulation.

A model of human muscle energy expenditure.

The HKB model (H. Haken, J. A. S. Kelso, & H. Bunz, 1985) of coordination has been predominantly applied to upper extremity stationary movements. It predicts increased variability of relative phase before a transition and a decrease after a transition. The authors of the present study extended the intralimb lower extremity locomotive research of F. J. Diedrich and W. H. Warren (1995) by conducting continuous treadmill walk-to-run and run-to-walk trials with 10 participants. Standard deviation of knee-ankle and hip-ankle relative phase did not increase before walk-to-run and run-to-walk transitions, and there was no decrease in knee-ankle relative phase variability after either transition. The results of this study did not provide strong support for application of the variability predictions of the HKB model of coordination to lower extremity intralimb coordination during gait transitions.

Gait transitions are not dependent on changes in intralimb coordination variability.

The purpose of this study was to determine if the relative ordering of locomotor oxygen consumption ( VO(2)) values remains stable as healthy children age. Beginning at age 6 and ending at age 10, VO(2) during level treadmill walking and running was quantified in 15 boys and 18 girls who were tested on an annual basis. Following 30 min of treadmill accommodation to each exercise mode, subjects walked and ran for 5 min at 1.34 m s(-1) and 2.23 m s(-1), respectively. During the last 2 min of each 5-min stage, expired gas samples were collected and analyzed to quantify VO(2). For both walking (W) and running (R), 27% of subjects showed an average yearly change in VO(2) rank order of </=2 positions, 64% (W) and 61% (R) displayed a mean annual shift in VO(2) rank order of </=4 positions, and 85% exhibited a mean yearly fluctuation in W and R VO(2) rank order of </=6 positions. Reliability analysis of VO(2) responses across the 5-year testing period also yielded high coefficient alpha values for walking ( R=0.91) and running ( R=0.94). These results suggest that the relative ordering of individual gait VO(2) values remains quite stable in young children, indicating a physiological stratification that is fairly resistant to change during a period featuring increases in physical growth and varied exposure to different types of physical activity.

Longitudinal stratification of gait economy in young boys and girls: the locomotion energy and growth study.

To investigate effects that independent alterations in limb mass and moment of inertia about a transverse axis through the hip have on metabolic and mechanical power of walking and peak electromyography (EMG) amplitude. It was hypothesized that increases in metabolic cost would parallel increases in mechanical power, and that EMG amplitude would increase with greater limb mass or limb moment of inertia.

Manipulations of leg mass and moment of inertia: effects on energy cost of walking.

Fast-twitch (FT) and slow-twitch (ST) muscle fibers vary in their mechanical and energetic properties, and it has been suggested that muscle fiber type distribution influences energy expenditure and the energetically optimal cadence during pedaling. However, it is challenging to experimentally isolate the effects of muscle fiber type on pedaling energetics. In the present study, a modeling and computer simulation approach was used to test the dependence of muscle energy expenditure on pedaling rate during submaximal cycling. Simulations were generated using a musculoskeletal model at cadences from 40 to 120 rev min(-1), and the dynamic and energetic properties of the model muscles were scaled to represent a range of muscle fiber types. Energy expenditure and the energetically optimal cadence were found to be higher in a model with more FT fibers than a model with more ST fibers, consistent with predictions from the experimental literature. At the muscle level, mechanical efficiency was lower in the model with a greater proportion of FT fibers, but peaked at a higher cadence than in the ST model. Regardless of fiber type distribution, mechanical efficiency was low at 40 rev min(-1), increased to a broad plateau between 60 and 100 rev min(-1) , and decreased substantially at 120 rev min(-1). In conclusion, muscle fiber type distribution was confirmed as an important determinant of the energetics of pedaling.

Muscle fiber type effects on energetically optimal cadences in cycling.

The purpose of this study was to determine the amount of time needed for individuals to become well accommodated to asymmetrical changes in lower extremity inertial properties. Participants walked at 1.57 m s(-1) during four separate data collection sessions over the period of eight days. On days 1 and 7, participants completed a 60 min treadmill protocol consisting of both overground (motion and ground reaction force recorded) and treadmill (vertical ground reaction force recorded) walking. On day 1, 1.95 kg was attached distally to one shank prior to the start of the 60 min treadmill protocol and was not removed until day 7. On day 7, the load was permanently removed prior to the 60 min treadmill protocol. On days 2 and 8 participants completed three overground walking trials and walked on the treadmill for approximately 5 min. Stance and swing time asymmetries appeared immediately and were complete following initial assessment after the load was attached. Net joint moments at the knee and hip were altered and continued to change beyond initial exposure to the load, but these changes were complete within 5 min. Overall, results suggest that changes in walking symmetry due to asymmetrical lower extremity loading are immediate and complete within 5 min of exposure to the load. We recommend that at least 5 min of walking or other normal activity be used to accommodate individuals to novel asymmetrical lower extremity loading.

Walking patterns change rapidly following asymmetrical lower extremity loading.

Walking humans prefer to use the stride rate that results in the lowest rate of metabolic energy expenditure. Mechanical power requirements have been suggested to underlie the metabolic response, but mechanical power is consistently reported to be minimal at stride rates 20-30% lower than preferred. This may be due to limitations in how total mechanical power has been computed, as well as a failure to account for the efficiency with which muscular work is done. We investigated how mechanical power and efficiency depend on stride rate in walking, with both quantities computed from the work done by the hip, knee and ankle joint moments. Our hypotheses were that mechanical power and efficiency are both optimized at the preferred stride rate, which would explain why metabolic energy expenditure is minimized at this rate. Contrary to our hypotheses, mechanical power curves exhibited plateaus that spanned stride rates lower than preferred (predicted optima: 11-12% below preferred), while net mechanical efficiency exhibited a plateau that spanned stride rates higher than preferred (predicted optimum: 8% above preferred). As expected, preferred stride rate (54.3 strides min(-1)) was not different from the stride rate that minimized net metabolic energy expenditure (predicted optimum: 0.2% above preferred). Given that mechanical power and mechanical efficiency exhibited plateaus on opposite sides of the preferred stride rate, the preferred rate in walking likely represents a compromise between these two factors. This may also explain the relative flatness of the curve for metabolic rate in the vicinity of the preferred stride rate.

Mechanical power and efficiency of level walking with different stride rates.

Our goal was to determine how age and walking speed affect metabolic cost of walking (C(w)), lower, extremity antagonist coactivation, and relationships between coactivation and C(w) in healthy, active, individuals. Fourteen young (25+/-3 years) and 14 older (71+/-4 years) participants walked on a treadmill at, four speeds (0.89, 1.12, 1.34, and 1.57 m s(-1)) while electromyography (EMG) and oxygen consumption, were measured. Coactivation indices were calculated for musculature about the thigh and shank. C(w), was higher in older adults across all speeds (p<0.001). Coactivation about the thigh was also higher in, older adults (p<0.001), whereas coactivation about the shank was not different between age groups (p=0.60). Total coactivation (thigh coactivation plus shank coactivation) showed significant positive, relationships to C(w) at all walking speeds (r=0.46-0.57). Higher C(w) and coactivation in older adults, along with the positive relationship between C(w) and coactivation implies coactivation contributes to, higher C(w) of older adults.

Effects of age and walking speed on coactivation and cost of walking in healthy adults.

Recent attention given to the mechanical work of the lower extremity joints, the emerging importance of the stance phase of running, and the lack of consensus regarding the biomechanical correlates to economical running were primary justifications for this study. The purpose of this experiment was to identify the correlations between metabolic power and the positive and negative mechanical work at lower extremity joints during stance. Recreational runners (n = 16) ran on a treadmill at 3.35 m s(-1) for physiological measures and overground for biomechanical measures. Inverse dynamics were used to calculate net joint moments and powers at the ankle, knee, and hip. Joint powers were then integrated over the stance phase so that positive and negative joint mechanical work were correlated with metabolic power (r = 0.60-0.69). Positive work at the hip and ankle during stance was positively correlated to metabolic power. In addition to these results, more economical runners (lower metabolic power) exhibited greater negative work at the hip, greater positive work at the knee, and less negative work at the ankle. Between the most and least economical runners, different mechanical strategies were present at the hip and knee, whereas the kinetics of the ankle joint differed only in magnitude.

Lower extremity mechanical work during stance phase of running partially explains interindividual variability of metabolic power.

Wearing high heels alters walking kinematics and kinetics and can create potentially adverse effects on the body. Our purpose was to determine how heel height affects frontal plane joint moments at the hip, knee, and ankle, with a specific focus on the knee moment due to its importance in joint loading and knee osteoarthritis. 15 women completed overground walking using three different heel heights (1, 5, and 9 cm) for fixed speed (1.3 ms(-1)) and preferred speed conditions while kinematic and force platform data were collected concurrently. For both fixed and preferred speeds, peak internal knee abduction moment increased systematically as heel height increased (fixed: 0.46, 0.48, 0.55 N m kg(-1); preferred: 0.47, 0.49, 0.53 N m kg(-1)). Heel height effects on net frontal plane moments of the hip and ankle were similar to those for the knee; peak joint moments increased as heel height increased. The higher peak internal knee abduction moment with increasing heel height suggests greater medial loading at the knee. Kinetic changes at the ankle with increasing heel height may also contribute to larger medial loads at the knee. Overall, wearing high heels, particularly those with higher heel heights, may put individuals at greater risk for joint degeneration and developing medial compartment knee osteoarthritis.

Heel height affects lower extremity frontal plane joint moments during walking.

Unilateral, transtibial amputees exhibit walking asymmetries and higher metabolic costs of walking than nonamputees walking at similar speeds. Using lightweight prostheses has previously been suggested as a contributing factor to walking asymmetries. The purpose was to investigate the effects of prosthesis mass and mass distribution on metabolic costs and walking asymmetries among six unilateral, transtibial amputees. Kinematic and temporal symmetry did not improve when mass was added at different locations on the limb. Stance and swing time asymmetries increased by 3.4% and 7.2%, respectively, with loads positioned distally on the limb. Maximum knee angular velocity asymmetries increased by 6% with mass added to the thigh, whereas maximum thigh angular velocity asymmetries increased by approximately 10% with mass positioned near the prosthetic ankle. Adding 100% of the estimated mass difference between intact and prosthetic legs to the ankle of the prosthesis increased energy costs of walking by 12%; adding the same mass to the prosthesis center of mass or thigh center of mass increased metabolic cost by approximately 7% and 5%, respectively. Unless other benefits are gained by increasing prosthesis mass, this should not be considered as a possible alternative to current lightweight prosthesis designs currently being prescribed to unilateral amputees.

Effects of prosthetic mass distribution on metabolic costs and walking symmetry.

Much of the work related to lower extremity inertia manipulations has focused on temporal, kinematic and traditional inverse dynamics assessments during locomotion. Intersegmental dynamics is an analytical technique that provides further insights into mechanisms underlying linked-segment motion. The purpose of this study was to determine how intersegmental dynamics during the swing phase of walking are altered during asymmetrical lower extremity loading. Participants walked overground at a speed of 1.57 ms(-1) with 0, 0.5, 1.0, and 2.0 kg attached to one foot. Net, interaction, gravitational, and muscle moments were computed. Moment magnitudes at joints of the loaded leg increased systematically with increasing load, whereas unloaded leg moments were unaffected by loading. With increasing load, relative contributions of interaction moments about the knee and hip and gravitational moment about the ankle increased (i.e., 21%, 8%, and 44% increases, respectively), whereas the relative contributions of muscle moments about all three joints declined (i.e., -4%, -13%, and -8% decreases for the ankle, knee, and hip, respectively for unloaded vs. 2.0 kg). These results suggest that altered inertia properties of the limb not only affected the amount of muscular effort required to swing the leg, but also changed the nature of the interaction between segments.

Philip E. Martin

Department of Kinesiology

Iowa State University

Oscillation and Reaction Board Techniques for Estimating Inertial Properties of a Below-knee Prosthesis

Philip E. Martin

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Iowa State University

Oscillation and Reaction Board Techniques for Estimating Inertial Properties of a Below-knee Prosthesis

Department of Kinesiology