Walking Biomechanics Research Articles

Familiarization with Carrying Backpack Loads Affects Biomechanics and Oxygen Consumption During Treadmill Walking

The time required for load bearing individuals to habituate to treadmill walking and achieve stable biomechanics and oxygen consumption has not been largely studied. PURPOSE: To investigate the effects on walking biomechanics and oxygen consumption of repeated exposures to carrying backpack loads. METHODS: 14 male U.S. Army Soldier volunteers (means: 21.3 yrs; 1.79 m; 82.3 kg) with about 12 months service experience participated over a two-week period. The volunteers had some exposure to carrying backpack loads. 7 performed three treadmill walking trials at each of two sessions one week and familiarization activities at each of two sessions the next week (TM1). The other 7 performed familiarization activities first (TM2). One of 6 backpacks was carried on each walking trial. The packs had the same mass (35 kg) and mass center, but different moments of inertia. The order of exposure to the packs was Latin square based. On walking trials (10 min at 4.8 km/h, 0% grade), the rate of oxygen consumption (VO2) and kinematic data were collected at minutes 5 and 6, respectively. Familiarization activities included zigzag runs, wall climbs, and standing to prone to standing movements with all 6 packs. VO2 scaled to body mass was averaged over 90-s periods for analysis. Kinematic data averaged over 5 strides were also analyzed. ANOVAs (a=.05) had one between-(Order: TM1-TM2) and two within-subjects factors (Day: 1-2; Trial: 1-3). Two volunteers' data were excluded; n= 5 for TM1. RESULTS: Mean mass specific VO yielded a significant Order × Day interaction (p< .05). Follow-up comparisons revealed that TM1's mean VO2 was significantly lower on Day 2 (15.30 ml/kg/min) than on Day 1 (17.02 ml/kg/min), improving 11%; TM2's mean VO2 was unchanged (15.55 ml/kg/min). A significant Order main effect was found for a number of the kinematic measures (p< .05): TM1 compared to TM2 revealed increased cycle time, stance time, step time, swing time and stride length. CONCLUSION: Repeated exposure to carrying backpack loads resulted in more efficient energy usage during treadmill walking. Carrying loads while performing physical activities other than treadmill walking affected walking biomechanics during subsequent load carriage on a treadmill. A familiarization and treadmill habituation effect may be even more pronounced with novice load carriers.

Effect of speed on kinematic, kinetic, electromyographic and energetic reference values during treadmill walking

Evaluation of normal and pathological gait on the level ground has drawbacks that could be overcome by walking on a treadmill. The present work was designed to assess the feasibility of extended gait analysis on a treadmill allowing multiple steps recording at a constant speed in young healthy subjects. It also aimed to provide speed-specific kinematic, kinetic, electromyographic and energetic reference values. Twelve healthy volunteers (23 +/- two years) walked on a force measuring treadmill at six speeds (1-6 k mh(-1)). Kinematics and kinetics were analysed at the hip, knee and ankle. Electromyographic muscle activity timing of quadriceps femoris, biceps femoris, tibialis anterior and lateral gastrocnemius was recorded. The energy cost was computed from oxygen consumption measurement. All variables were speed-dependent. Kinematics and kinetics peaks amplitude increased and occurred earlier during the walking cycle with increasing walking speed. Muscle activity timing also changed with speed, although the number of bursts remained constant. The energetic cost presented a U-shaped curve, with minimal values around 4 km h(-1). Data were compared to overground walking data obtained by several authors: all results, except kinetic ones, were similar, turning down the thought that biomechanics of treadmill and overground walking could be different. This study provides reference values for normal and pathological walking on treadmill and allows speed-dependent comparison between subjects.

A computer simulation study on the causal relationship between walking and physical malfunctions in older adults

The purpose of the present study was to investigate the causal relationship between walking pattern and physical malfunction using a computer simulation method with a biomechanical walking model. In this computer simulation, the musculoskeletal system was represented by a three-dimensional 14-rigid-link model and 60 muscle models. Muscular forces were controlled by a neuronal system model consisting of 16 pairs of neural oscillators. In the computational experiment, five types of walking models were constructed: an intact model, a delayed response model, a weak muscle model, an inclined posture model, and a joint contracture model. These malfunction factors were hypothesized to have a causal relationship with walking characteristics in older adults. The simulation revealed that the delayed response in the neuronal system was primarily related to walking stability. In addition, the weakening of muscles was strongly related to the reduction of the walking step length. The inclined posture and joint contracture also influenced the walking pattern, but not significantly. The use of such a computer simulation method is essential in order to clarify the causal relationship between body function and walking pattern in older adults.

Biomechanics of overground vs. treadmill walking in healthy individuals

The goal of this study was to compare treadmill walking with overground walking in healthy subjects with no known gait disorders. Nineteen subjects were tested, where each subject walked on a split-belt instrumented treadmill as well as over a smooth, flat surface. Comparisons between walking conditions were made for temporal gait parameters such as step length and cadence, leg kinematics, joint moments and powers, and muscle activity. Overall, very few differences were found in temporal gait parameters or leg kinematics between treadmill and overground walking. Conversely, sagittal plane joint moments were found to be quite different, where during treadmill walking trials, subjects demonstrated less dorsiflexor moments, less knee extensor moments, and greater hip extensor moments. Joint powers in the sagittal plane were found to be similar at the ankle but quite different at the knee and hip joints. Differences in muscle activity were observed between the two walking modalities, particularly in the tibialis anterior throughout stance, and in the hamstrings, vastus medialis and adductor longus during swing. While differences were observed in muscle activation patterns, joint moments and joint powers between the two walking modalities, the overall patterns in these behaviors were quite similar. From a therapeutic perspective, this suggests that training individuals with neurological injuries on a treadmill appears to be justified.

Effects of Obesity on the Biomechanics of Walking at Different Speeds

Walking is a recommended form of exercise for the treatment of obesity, but walking may be a critical source of biomechanical loads that link obesity and musculoskeletal pathology, particularly knee osteoarthritis. We hypothesized that compared with normal-weight adults 1) obese adults would have greater absolute ground-reaction forces (GRF) during walking, but their GRF would be reduced at slower walking speeds; and 2) obese adults would have greater sagittal-plane absolute leg-joint moments at a given walking speed, but these moments would be reduced at slower walking speeds. We measured GRF and recorded sagittal-plane kinematics of 20 adults (10 obese and 10 normal weight) as they walked on a level, force-measuring treadmill at six speeds (0.5-1.75 m.s(-1)). We calculated sagittal-plane net muscle moments at the hip, knee, and ankle. Compared with their normal-weight peers, obese adults had much greater absolute GRF (N), stance-phase sagittal-plane net muscle moments (N.m) and step width (m). Greater sagittal-plane knee moments in the obese subjects suggest that they walked with greater knee-joint loads than normal-weight adults. Walking slower reduced GRF and net muscle moments and may be a risk-lowering strategy for obese adults who wish to walk for exercise. When obese subjects walked at 1.0 versus 1.5 m.s(-1), peak sagittal-plane knee moments were 45% less. Obese subjects walking at approximately 1.1 m.s(-1) would have the same absolute peak sagittal-plane knee net muscle moment as normal-weight subjects when they walk at their typical preferred speed of 1.4 m.s(-1).

Just drop it and run: the effect of limb autotomy on running distance and locomotion energetics of field crickets (Gryllus bimaculatus)

This is the first study to examine the direct metabolic costs of autotomy, the voluntary shedding of an appendage as an escape mechanism, in invertebrates. We investigated the effects of limb autotomy upon endurance and metabolic cost of locomotion in the field cricket Gryllus bimaculatus. Compared with control (intact) crickets, animals that had autotomised a single hindlimb were slower, stopped more often, moved a shorter distance and expended more energy doing so. Both the cost of locomotion (COT) and minimal cost of locomotion (MCOT) were significantly higher for autotomised animals. We compare these data with locomotion energetics of 36 other invertebrate species, and discuss the results in terms of the biomechanics of walking in crickets.

The Effects of Adding Mass to the Legs on the Energetics and Biomechanics of Walking

The metabolic cost of walking increases when mass is added to the legs, but the effects of load magnitude and location on the energetics and biomechanics of walking are unclear. We hypothesized that with leg loading 1) net metabolic rate would be related to the moment of inertia of the leg (I(leg)), 2) kinematics would be conserved, except for heavy foot loads, and 3) swing-phase sagittal-plane net muscle moments and swing-phase leg-muscle electromyography (EMG) would increase. Five adult males walked on a force-measuring treadmill at 1.25 m.s(-1) with no load and with loads of 2 and 4 kg per foot and shank, 4 and 8 kg per thigh, and 4, 8, and 16 kg on the waist. We recorded metabolic rate and sagittal-plane kinematics and net muscle moments about the hip, knee, and ankle during the single-stance and swing phases, and EMG of key leg muscles. Net metabolic rate during walking increased with load mass and more distal location and was correlated with I(leg) (r2 = 0.43). Thigh loading was relatively inexpensive, helping to explain why the metabolic rate during walking is not strongly affected by body mass distribution. Kinematics, single-stance and swing-phase muscle moments, and EMG were similar while walking with no load or with waist, thigh, or shank loads. The increase in net metabolic rate with foot loading was associated with greater EMG of muscles that initiate leg swing and greater swing-phase muscle moments. Distal leg loads increase the metabolic rate required for swinging the leg. The increase in metabolic rate with more proximal loads may be attributable to a combination of supporting (via hip abduction muscles) and propagating the swing leg.

Effects of Obesity on the Biomechanics of Walking at different speeds

Effects of Obesity on the Biomechanics of Walking at different speeds

Harvesting Energy by Improving the Economy of Human Walking

Mobile power sources such as batteries often add great additional weight to a backpacker9s load. As a result, there is great interest in harvesting electrical power from the energy expended during walking in a variety of situations. In his Perspective, Kuo discusses results reported in the same issue by Rome et al., in which a backpack with a spring-loaded weight was found to permit generation of electrical power with unexpected efficiency. Analysis of the biomechanics of walking indicates that the oscillating payload enables generation of useful amounts of power while costing less metabolic energy than expected.

An improved powered ankle–foot orthosis using proportional myoelectric control

We constructed a powered ankle-foot orthosis for human walking with a novel myoelectric controller. The orthosis included a carbon fiber and polypropylene shell, a metal hinge joint, and two artificial pneumatic muscles. Soleus electromyography (EMG) activated the artificial plantar flexor and inhibited the artificial dorsiflexor. Tibialis anterior EMG activated the artificial dorsiflexor. We collected kinematic, kinetic, and electromyographic data for a naive healthy subject walking with the orthosis. The current design improves upon a previous prototype by being easier to don and doff and simpler to use. The novel controller allows naive wearers to quickly adapt to the orthosis without artificial muscle co-contraction. The orthosis may be helpful in studying human walking biomechanics and assisting patients during gait rehabilitation after neurological injury.

The Effects of Obesity on the Energetics and Biomechanics of Walking

The Effects of Obesity on the Energetics and Biomechanics of Walking

The Effects of Obesity on the Energetics and Biomechanics of Walking

The Effects of Obesity on the Energetics and Biomechanics of Walking

Comparison Of Habitual Physical Activity Measured By Heart Rate And By Accelerometry In Cerebral Palsy

Physical activity (PA) has physiologic, mechanical and behavioral components. We have previously shown that for children and adolescents with mild spastic cerebral palsy (CP), their habitual PA measured physiologically with monitored heart rate (HR) is related to their physiologic walking economy (oxygen cost of walking). We have also shown for this population that their habitual PA measured mechanically with tri-axial accelerometry is related to their biomechanical walking economy (vertical excursion of the center of mass relative to that expected in normal gait). In both instances, those with the higher levels of PA were the more economical walkers. The relationship between physiologic and mechanical measures of PA in this population, however, is unknown. PURPOSE To determine, in children and adolescents with cerebral palsy (CP), the relationship between; 1) habitual PA as measured by monitored HR and by tri-axial accelerometry and 2) habitual PA and gross motor function related to walking (GMF-W). METHODS Ten subjects (10.6–16.3 yr) with mild spastic CP, simultaneously wore a HR monitor and a tri-axial accelerometer for two weekdays and one weekend day. PAL, the ratio of total energy expenditure to resting energy expenditure, was determined from the monitored HR data, with individual HR-oxygen uptake calibrations and resting measures done in the lab. From the accelerometry data, total vector magnitude movement counts ± d−1 (TMC) and the number of minutes ± d−1 TMC were above the 90th percentile for the group (TMC90) were determined. GMF-W was measured in the lab using the Walking, Running and Jumping Dimension of the Gross Motor Function Measure. Relationships were analyzed using linear regression techniques. Alpha was set at .05. RESULTS PAL (1.33 ± .04) was significantly related (r=.75) to TMC (1.53 ± 105 ± 1.4 ± 104 counts) and (r=.78) to TMC90 (59.8 ± 8.1 minutes). PAL was also significantly related (r=.82) to GMF-W (82.1 ± 5.6%) as were TMC (r=.89) and TMC90 (r=.90). There was no significant relationship for PAL, TMC, TMC90 or GMF-W with age (r=.00001 to .21, P=.60 to 1.0). CONCLUSIONS For older children and adolescents with mild CP, those with higher levels of the physiologic component of PA, may also have higher levels of the mechanical component. Those with higher levels of either component of habitual PA, may also have the better gross motor function related to walking. Further research is needed to determine if, and to what extent, this gross motor function is related to metabolic and mechanical walking economy.

Comparison Of Habitual Physical Activity Measured By Heart Rate And By Accelerometry In Cerebral Palsy

Physical activity (PA) has physiologic, mechanical and behavioral components. We have previously shown that for children and adolescents with mild spastic cerebral palsy (CP), their habitual PA measured physiologically with monitored heart rate (HR) is related to their physiologic walking economy (oxygen cost of walking). We have also shown for this population that their habitual PA measured mechanically with tri-axial accelerometry is related to their biomechanical walking economy (vertical excursion of the center of mass relative to that expected in normal gait). In both instances, those with the higher levels of PA were the more economical walkers. The relationship between physiologic and mechanical measures of PA in this population, however, is unknown. PURPOSE To determine, in children and adolescents with cerebral palsy (CP), the relationship between; 1) habitual PA as measured by monitored HR and by tri-axial accelerometry and 2) habitual PA and gross motor function related to walking (GMF-W). METHODS Ten subjects (10.6–16.3 yr) with mild spastic CP, simultaneously wore a HR monitor and a tri-axial accelerometer for two weekdays and one weekend day. PAL, the ratio of total energy expenditure to resting energy expenditure, was determined from the monitored HR data, with individual HR-oxygen uptake calibrations and resting measures done in the lab. From the accelerometry data, total vector magnitude movement counts ± d−1 (TMC) and the number of minutes ± d−1 TMC were above the 90th percentile for the group (TMC90) were determined. GMF-W was measured in the lab using the Walking, Running and Jumping Dimension of the Gross Motor Function Measure. Relationships were analyzed using linear regression techniques. Alpha was set at .05. RESULTS PAL (1.33 ± .04) was significantly related (r=.75) to TMC (1.53 ± 105 ± 1.4 ± 104 counts) and (r=.78) to TMC90 (59.8 ± 8.1 minutes). PAL was also significantly related (r=.82) to GMF-W (82.1 ± 5.6%) as were TMC (r=.89) and TMC90 (r=.90). There was no significant relationship for PAL, TMC, TMC90 or GMF-W with age (r=.00001 to .21, P=.60 to 1.0). CONCLUSIONS For older children and adolescents with mild CP, those with higher levels of the physiologic component of PA, may also have higher levels of the mechanical component. Those with higher levels of either component of habitual PA, may also have the better gross motor function related to walking. Further research is needed to determine if, and to what extent, this gross motor function is related to metabolic and mechanical walking economy.

Habitual Physical Activity Levels Are Associated with Biomechanical Walking Economy in Children with Cerebral Palsy

To evaluate in children and adolescents with cerebral palsy the relationship between habitual physical activity and biomechanical treadmill walking economy and whether treadmill belt speed or walking time affect economy. Physical activity was measured in 11 subjects (10.6-16.3 yrs) with mild cerebral palsy using a triaxial accelerometer. To determine biomechanical walking economy, subjects' stride lengths and vertical sacral excursions were measured during each minute of three 3-min walks on a treadmill (at 60%, 75%, and 90% of individually determined fastest treadmill walking speed). Biomechanical walking economy at 60%, 75%, and 90% of (their) fastest speed each explained about half of the intersubject variance in daily physical activity (movement counts). A similar relationship was found between these biomechanical walking economy variables and movement counts at or above the 80th and 90th percentile (total minutes per day, number of 5-min bouts per day). Walking economy was 23.9% higher when subjects walked at 90% than when they walked at 60% of their fastest walking speed. No other speed-related effects on economy were found, nor did time affect economy. Within this population, those with high biomechanical treadmill walking economy are the more habitually physically active. Treadmill belt speed, but not walking time, affects biomechanical walking economy.

Biomechanics and muscle coordination of human walking: part II: lessons from dynamical simulations and clinical implications.

Principles of muscle coordination in gait have been based largely on analyses of body motion, ground reaction force and EMG measurements. However, data from dynamical simulations provide a cause-effect framework for analyzing these measurements; for example, Part I (Gait Posture, in press) of this two-part review described how force generation in a muscle affects the acceleration and energy flow among the segments. This Part II reviews the mechanical and coordination concepts arising from analyses of simulations of walking. Simple models have elucidated the basic multisegmented ballistic and passive mechanics of walking. Dynamical models driven by net joint moments have provided clues about coordination in healthy and pathological gait. Simulations driven by muscle excitations have highlighted the partial stability afforded by muscles with their viscoelastic-like properties and the predictability of walking performance when minimization of metabolic energy per unit distance is assumed. When combined with neural control models for exciting motoneuronal pools, simulations have shown how the integrative properties of the neuro-musculo-skeletal systems maintain a stable gait. Other analyses of walking simulations have revealed how individual muscles contribute to trunk support and progression. Finally, we discuss how biomechanical models and simulations may enhance our understanding of the mechanics and muscle function of walking in individuals with gait impairments.

Biomechanics and muscle coordination of human walking. Part I: introduction to concepts, power transfer, dynamics and simulations.

Current understanding of how muscles coordinate walking in humans is derived from analyses of body motion, ground reaction force and EMG measurements. This is Part I of a two-part review that emphasizes how muscle-driven dynamics-based simulations assist in the understanding of individual muscle function in walking, especially the causal relationships between muscle force generation and walking kinematics and kinetics. Part I reviews the strengths and limitations of Newton-Euler inverse dynamics and dynamical simulations, including the ability of each to find the contributions of individual muscles to the acceleration/deceleration of the body segments. We caution against using the concept of biarticular muscles transferring power from one joint to another to infer muscle coordination principles because energy flow among segments, even the adjacent segments associated with the joints, cannot be inferred from computation of joint powers and segmental angular velocities alone. Rather, we encourage the use of dynamical simulations to perform muscle-induced segmental acceleration and power analyses. Such analyses have shown that the exchange of segmental energy caused by the forces or accelerations induced by a muscle can be fundamentally invariant to whether the muscle is shortening, lengthening, or neither. How simulation analyses lead to understanding the coordination of seated pedaling, rather than walking, is discussed in this first part because the dynamics of pedaling are much simpler, allowing important concepts to be revealed. We elucidate how energy produced by muscles is delivered to the crank through the synergistic action of other non-energy producing muscles; specifically, that a major function performed by a muscle arises from the instantaneous segmental accelerations and redistribution of segmental energy throughout the body caused by its force generation. Part II reviews how dynamical simulations provide insight into muscle coordination of walking.

H reflexes recorded during locomotion.

We recorded H reflexes and the biomechanics of movement during locomotion. The soleus H reflex was strongly modulated during normal walking, depressed during the swing phase and modulated with the EMG in the stance phase. The amplitude of the H reflex increased with the EMG activity and was larger during running than walking. There were individual differences in the modulation pattern covariant with the biomechanics of walking. Interpretation of the results requires knowledge of the method used and assessment of the stimulus and recording conditions.

Gait analysis of poultry

Lameness is a major problem in the UK poultry industry, however, relatively few objective studies have been undertaken into the biomechanics of normal walking in these birds. In this study, the use of a pedobarograph as a novel method of gait analysis in poultry was investigated. Unlike most systems, the pedobarograph has a recording surface with a high degree of spatial resolution, allowing pressure patterns to be established for various regions of the foot. The highest pressures were found to act on the medial toe (149·4–218 kN m −2) and back toe (146·1–195-· kN m −2). The metatarsal pad, a region often associated with lesions, was subject to lower pressures (16·3–131·2 kN m −2). Maximum net forces of 116–145 per cent of bodyweight were found during normal walking, an order of the same magnitude as human bipeds. Routine spatial parameters were also measured, allowing further characterisation of the gait patterns.

10 Biomechanics of Walking and Running

10 Biomechanics of Walking and Running