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PubMed2002

Dynamic stabilization of rapid hexapedal locomotion.

To stabilize locomotion, animals must generate forces appropriate to overcome the effects of perturbations and to maintain a desired speed or direction of movement. We studied the stabilizing mechanism employed by rapidly running insects by using a novel apparatus to perturb running cockroaches (Blaberus discoidalis). The apparatus used chemical propellants to accelerate a small projectile, generating reaction force impulses of less than 10 ms duration. The apparatus was mounted onto the thorax of the insect, oriented to propel the projectile laterally and loaded with propellant sufficient to cause a nearly tenfold increase in lateral velocity relative to maxima observed during unperturbed locomotion. Cockroaches were able to recover from these perturbations in 27+/-12 ms (mean +/- S.D., N=9) when running on a high-friction substratum. Lateral velocity began to decrease 13+/-5 ms (mean +/- S.D., N=11) following the start of a perturbation, a time comparable with the fastest reflexes measured in cockroaches. Cockroaches did not require step transitions to recover from lateral perturbations. Instead, they exhibited viscoelastic behavior in the lateral direction, with spring constants similar to those observed during unperturbed locomotion. The rapid onset of recovery from lateral perturbations supports the possibility that, during fast locomotion, intrinsic properties of the musculoskeletal system augment neural stabilization by reflexes.

Animals↗
PubMed1982

Energetics and mechanics of terrestrial locomotion. IV. Total mechanical energy changes as a function of speed and body size in birds and mammals.

This is the final paper in or series examining the link between the energetics and mechanics of terrestrial locomotion. In this paper the kinetic energy of the limbs and body relative to the centre of mass (EKE, tot of paper two) is combined with the potential plus kinetic energy of the centre of mass (ECM, tot of paper three) to obtain the total mechanical energy (excluding elastic energy) of an animal during constant average-speed locomotion. The minimum mass-specific power required of the muscles and tendons to maintain the observed oscillations in total energy, Etot/Mb, can be described by one equation: Etot/Mb = 0.478 . vg 1.53 + 0.685 . vg + 0.072 where Etot/Mb is in W kg-1 and vg is in m s-1. This equation is independent of body size, applying equally as well to a chipmunk or a quail as to a horse or an ostrich. In marked contrast, the metabolic energy consumed by each gram of an animal as it moves along the ground at a constant speed increases linearly with speed and is proportional to Mb-0.3. Thus, we have found that each gram of tissue of a 30 g quail or chipmunk running at 3 m s-1 consumes metabolic energy at a rate about 15 times that of a 100 kg ostrich, horse or human running at the same speed while their muscles are performing work at the same rate. Our measurements demonstrate the importance of storage and recovery of elastic energy in larger animals, but they cannot confirm or exclude the possibility of elastic storage of energy in small animals. It seems clear that the rate at which animals consume energy during locomotion cannot be explained by assuming a constant efficiency between the energy consumed and the mechanical work performed by the muscles. It is suggested that the intrinsic velocity of shortening of the active muscle motor units (which is related to the rate of cycling of the cross bridges between actin and myosin) and the rate at which the muscles are turned on and off are the most important factors in determining the metabolic cost of constant-speed locomotion. Faster motor units are recruited as animals increase speed, and equivalent muscles of small animals have faster fibres than those of larger animals. Also, the muscles are turned on and off more quickly as an animal increases speed, and at the same speed a small animal will be turning muscles on and off at a much higher rate. These suggestions are testable, and future studies should determine if they are correct.

Animals↗
PubMed2003

Estrogen and bone--a reproductive and locomotive perspective.

UNLABELLED: The primary function of the skeleton is locomotion, and the primary function of estrogen is reproduction. When the skeleton is considered within this locomotive context, the onset of estrogen secretion at puberty leads to packing of mechanically excess mineral into female bones for reproductive needs. Accordingly, the unpacking of this reproductive safety deposit at menopause denotes the origin of type I osteoporosis. INTRODUCTION: According to the prevailing unitary model of involutional osteoporosis, female postmenopausal bone loss can be described as having an initial accelerated, transient phase (type I), followed by a gradual continuous phase (type II). Estrogen withdrawal is generally accepted as the primary cause of the type I osteoporosis. Thus, the quest to uncover the origin of type I osteoporosis has focused on the estrogen withdrawal-related skeletal changes at and around the menopause. However, considering that the cyclical secretion of estrogen normally begins in early adolescence and continues over the entire fertile period, one could argue that focusing on perimenopause alone may be too narrow. MATERIALS AND METHODS: This is not a systematic review of the literature on the skeletal function of estrogen(s), but rather, an introduction of a novel structure- and locomotion-oriented perspective to this particular issue through pertinent experimental and clinical studies. RESULTS AND CONCLUSIONS: When considering locomotion as the primary function of the skeleton and integrating the classic findings of the pubertal effects of estrogen on female bones and the more recent hypothesis-driven experimental and clinical studies on estrogen and mechanical loading on bone within this context, a novel evolution-based explanation for the role of estrogen in controlling female bone mass can be outlined: the onset of estrogen secretion at puberty induces packing of mechanically excess bone into female skeleton for needs of reproduction (pregnancy and lactation). Accordingly, the unpacking of this reproductive safety deposit of calcium at menopause denotes the accelerated phase of bone loss and thus the origin of type I osteoporosis.

Adolescent↗
PubMed2006

Intrinsic and functional differences among commissural interneurons during fictive locomotion and serotonergic modulation in the neonatal mouse.

Commissural interneurons (CINs) send their axons across the midline to innervate contralateral targets and have been implicated in the coordination of left-right limb movements during locomotion. In the neonatal mouse spinal cord, we studied the firing properties and responses to serotonin (5-HT) of two classes of CINs: those whose axons turn caudally after crossing the midline (dCINs) and those whose axons bifurcate after crossing the midline (adCINs). During NMDA and 5-HT-induced locomotor-like activity, a majority of lumbar (L2) dCINs fired rhythmically with ventral root-recorded motor activity, although their firing phase was widely distributed throughout the locomotor cycle. In contrast, none of the adCINs fired rhythmically during fictive locomotion. We studied the baseline firing and membrane properties, and responses to current injection, in dCINs and adCINs that had been partially isolated by blockade of rapid synaptic transmission (with antagonists to glutamate, GABA, and glycine). No significant baseline differences were found between the cell types. In contrast, 5-HT significantly increased the excitability of the isolated dCINs by depolarizing the membrane potential, reducing the postspike afterhyperpolarization amplitude and decreasing the action potential threshold. None of these parameters were affected by 5-HT in adCINs. These results, together with our recent study of a third class of CINs, the aCINs whose axons ascend after crossing the midline (Zhong et al., 2006), suggest that dCINs and aCINs, but not adCINs, are excited by 5-HT and are rhythmically active during fictive locomotion. Thus, they may play important roles in the coordination of left-right movements during fictive locomotion.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed2000

Mechanical and metabolic profile of locomotion in adults with childhood-onset GH deficiency.

OBJECTIVE: The aim of the present study was to evaluate the energy cost and the mechanical work of locomotion in a group of adults with childhood-onset GH deficiency (GHD). SUBJECTS: Eight males with childhood-onset GHD (mean age+/-s.d.: 31.7+/-3.6 years; mean height: 145.1+/-6.7cm) and six age-, sex- and exercise-matched normal subjects were studied. DESIGN: GHD patients and healthy controls were requested to walk and run in the speed range of 2-11km h(-1). For each condition, simultaneous mechanical and metabolic measurements were taken. METHODS: Oxygen consumption, and mechanical internal and external work of locomotion were evaluated with standard open-circuit respirometry and three-dimensional motion analysis respectively. RESULTS: External work was not significantly different between GHD patients and healthy controls, while internal work was higher for patients at all speeds. In walking, the relationships between both the mechanical energy recovery and the metabolic cost with speed were shifted towards lower speeds in patients. As a consequence, the optimal speed of walking, i.e. the speed at which the cost of locomotion is minimum, was lower for GHD patients. Stride frequency was significantly higher (11.2-11.3%) for GHD patients at all speeds of walking and running. GHD patients were unable to run at speeds higher than 8km h(-1) for the time needed to reach a metabolic steady state. CONCLUSION: It appears that both the mechanics and energetics of locomotion in short-statured adults with childhood-onset GHD are not strikingly different from those of healthy controls, thus demonstrating a substantial 'normality' in this group of GHD patients at metabolically attainable speeds. The 'harmonic' body structure and the adherence to allometric transformations in these patients do not exclude the possibility of a different metabolic role of GH in normally statured adults with childhood-onset GHD and in those with acquired GHD, taking into account the well recognized heterogeneity of the adult GHD syndrome.

Adult↗
PubMed1996

Locomotive stereotyped behavior in cynomolgus macaques, Macaca fascicularis.

Primate infants separated from their mothers and kept alone for a long period may exhibit behavioral disorders and develop stereotyped behavior according to genetic predispositions of the infants and environmental factors such as characteristics of the cage. However, it is not clear whether the locomotive and repetitive stereotyped behaviors are related to maternal separation or isolation rearing early in life. The locomotive and repetitive stereotyped behaviors and their relationship were examined with 65 juveniles of cynomolgus macaques kept under artificial conditions. All infants were separated from their mothers and kept with peers. Observations were conducted when they were about three to five years old. The monkeys exhibited locomotive and repetitive stereotyped behavior such as turning, backward somersaulting, and bouncing. Most showed both turning and backward somersaulting. Observations indicated that social interactions with peers following maternal separation at the age of 3 to 5 mo. produce the locomotive and repetitive stereotyped behavior and that turning may change to backward somersaulting for older infants. Further work with controls for several factors is needed.

Age Factors↗
PubMed1997

Morphometric description of the wandering behavior in Drosophila larvae: aberrant locomotion in Na+ and K+ channel mutants revealed by computer-assisted motion analysis.

Wandering is a simple behavior in Drosophila larvae prior to metamorphosis. Using the Dynamic Image Analysis System (DIAS) initially developed for analyzing amoeboic movements of single cells, we have analyzed videotaped behaviors of Drosophila larvae at the wandering stage. Previous studies show that mutations in the Na+ channel gene paralytic (para) cause paralysis at 29 degrees C, and mutations in the K+ channel beta subunit gene Hyperkinetic (Hk) lead to leg-shaking under ether anesthesia. The application of DIAS revealed quantifiable abnormalities in the larval locomotion of both ion channel mutants even under "permissive" conditions. Analysis of centroid movement indicates that, compared to wild type, both Hk and para larvae crawled at a slower average speed, but a similar peak instantaneous speed during a contraction cycle. Nevertheless, contraction in the body length was greater in mutants, implying a lower efficiency in conversion of muscular contraction to distance translocation. In addition, each mutant produced a characteristic crawling pattern distinct from the wild-type control. The larval crawling pattern was determined by periods of linear locomotion interposed by non-locomotive, "searching and decision-making" episodes, after which the crawling was resumed in a new direction. Our results demonstrate that mutations in single ion channel subunits resulted in stereotypic modifications in locomotion control and crawling patterns, and that DIAS is a powerful tool in revealing subtle differences in animal behavior and quantifying mutational effects on the interplay of discrete behavioral components.

Animals↗
PubMed1979

The clinical assessment of the normal and abnormal foot during locomotion.

The clinical assessment of the weight-bearing foot during locomotion is normally based on subjective judgement rather than on quantitative measurement. Although anatomical abnormalities are often apparent at examination, the accurate assessment of an abnormality of function is more difficult to assess particularly if the abnormality is only apparent under dynamic loading conditions. The many drawbacks in previous methods proposed for the clinical assessment of gait have led to the development of a novel system which allows an immediate quantitative visualization of the magnitude and point of application of the forces applied to the plantar surface of the foot during locomotion. This paper describes the technique and presents visual data on normal locomotion, on abnormal locomotion and the changes induced into a patient's abnormal gait by corrective surgery.

Biomechanical Phenomena↗
PubMed1992

Locomotion status and costs in destructive rheumatoid arthritis. A comprehensive study of 82 patients from a population of 13,000.

Clinical manifestations (locomotion score) and annual costs were studied in a population-based cohort of 82 patients with rheumatoid arthritis fulfilling five to eight American Rheumatological Association's (ARA) criteria. The total costs were SEK 4.9 million: respectively 56 and 44 percent direct and indirect costs. The costs were correlated with total, as well as subjective and objective, locomotion scores, which assess separately impairment, disability, and handicap from the disease (WHO 1980). Patients below 65 years had higher costs-predominantly as an indirect cost due to loss of work-than older patients. Elderly rheumatoid arthritis (RA) patients had a low score and high costs for medical and social services' care, but they had no indirect costs. Patients with a low locomotion score had received previous hospital treatment averaging 89 days. The need of hospital treatment was strongly correlated with low locomotion score. The mean annual patient's costs were about SEK 60,000, but above this for younger patients. When compared with patients with a mild affliction (score 91-100), patients with moderate manifestations, i.e., with a score of 70-90, had five times higher costs, whereas those with severe manifestations, with a score below 50, had 20 times higher costs.

Adult↗
PubMed1991

[Epidemiologic study on factors related to physical locomotion ability among the aged].

The present study was conducted in order to examine epidemiologic factors related to physical locomotion ability among the aged in an area with long life expectancy, a village in Okinawa Prefecture. Medical examinations and interviews were performed for 756 inhabitants aged 65 years and older, who were classified into 2 groups of physical locomotion ability, a high group and a low group. According to the results after multiple logistic regression analysis, the following factors showed positive relation to physical locomotion ability: age, working status, food intake frequencies (fish, eggs and green vegetables), skinfold thickness, grip strength and serum albumin. However, no statistical associations were observed between physical locomotion ability and other factors such as sex, smoking status, alcohol intake, hypertension, Quetelet's index, serum total cholesterol or and hemoglobin.

Aged↗
PubMed2006

Effects of roughness and compressibility of flooring on cow locomotion.

We examined the effects of roughness and degree of compressibility of flooring on the locomotion of dairy cows. We observed 16 cows walking down specially constructed walkways with materials that differed in surface roughness and degree of compressibility. Use of a commercially available soft rubber flooring material decreased slipping, number of strides, and time to traverse the corridor. These effects were most apparent at difficult sections of the corridor, such as at the start, at a right-angle turn, and across a gutter. Covering the walkway with a thin layer of slurry increased frequency of slipping, number of strides, and time taken to traverse the walkway. Effects of adding slurry were not overcome by increasing surface roughness or compressibility. Placing more compressible materials under a slip-resistant material reduced the time and number of steps needed to traverse the corridor but did not reduce slips, and the effects on cow locomotion varied nonlinearly with the degree of compressibility of the floor. Use of commercially available rubber floors improved cow locomotion compared with concrete floors. However, standard engineering measures of the floor properties may not predict effects of the floor on cow behavior well. Increasing compressibility of the flooring on which cows walk, independently of the roughness of the surface, can improve cow locomotion.

Animals↗
PubMed2000

Initiating or blocking locomotion in spinal cats by applying noradrenergic drugs to restricted lumbar spinal segments.

After an acute low thoracic spinal transection (T13), cats can be made to walk with the hindlimbs on a treadmill with clonidine, an alpha2-noradrenergic agonist. Because previous studies of neonatal rat spinal cord in vitro suggest that the most important lumbar segments for rhythmogenesis are L1-L2, we investigated the role of various lumbar segments in the initiation of walking movements on a treadmill of adult cats spinalized (T13), 5-6 d earlier. The locomotor activities were evaluated from electromyographic and video recordings. The results show that: (1) localized topical application of clonidine in restricted baths over either the L3-L4 or the L5-L7 segments was sufficient to induce walking movements. Yohimbine, an alpha2-noradrenergic antagonist, could block this locomotion when applied over L3-L4 or L5-L7; (2) microinjections of clonidine in one or two lumbar segments from L3 to L5 could also induce locomotion; (3) after an intravenous injection of clonidine, locomotion was blocked by microinjections of yohimbine in segments L3, L4, or L5 but not if the injection was in L6; (4) locomotion was also blocked in all cases by additional spinal transections at L3 or L4. These results show that it is possible to initiate walking in the adult spinal cat with a pharmacological stimulation of a restricted number of lumbar segments and also that the integrity of the L3-L4 segments is necessary to sustain the locomotor activity.

Adrenergic alpha-Agonists↗
PubMed2003

Electromyographic activity in the Rhesus monkey forelimb muscles during a goal directed movement and locomotion before, during and after spaceflight.

The aim of the present study was to analyse the effects of microgravity on i) the achievement of goal-directed arm movements and ii) the quadrupedal non-human primate locomotion. A reaching movement in weightlessness would require less muscle contraction since there is no need to oppose gravity. Consequently the electromyographic (EMG) activity of the monkey forelimb muscles should be changed during or after spaceflight. EMG activity of the biceps and triceps muscles during goal-directed arm movements were studied in Rhesus monkeys before, during and after 14 days of spaceflight and flight simulation at normal gravity. The EMG activity was also recorded during treadmill locomotion before and after spaceflight. When performing arm motor tasks, the delay values of the EMG bursts were unchanged during the flight. On the contrary, mean EMG was significantly decreased during the flight comparatively to the pre- and post-flight values, which were very similar. Compared with flight animals, the control ground monkey showed no change in the burst durations and mean EMG. After spaceflight, quadrupedal locomotion was modified. The animals had some difficulty in moving, and abnormal steps were numerous. The integrated area of triceps bursts was increased for the stance phase during locomotion. Taken together these data showed that spaceflight induces a dual adaptative process: first, the discharge of the motor pools of the forelimb musculature was modified during exposure to microgravity, and then upon return to Earth, monkeys changed their new motor strategy and re-adapt to normal gravity.

Adaptation, Physiological↗
PubMed1985

[Studies on interlimb coordination of the cat during locomotion].

Experiments were performed on cats with chronic spinal lesions, in order to decide which systems either interlimb-propriospinal systems or direct descending systems, plays important roles for coordination of overground locomotion of the cat. The phase relationships between homolateral, crossed, bilateral forelimbs and hindlimbs were analysed during locomotion. For 27 cats a single hemisection was applied at the level of C1 or T12. In 19 cats, the spinal cord was firstly hemisected at around T12, then 5-183 days after, contralateral thoracic cord around T8 was hemisected (T-T; thoracic-thoracic bilateral serial hemisection). Therefore in this group, only crossed descending propriospinal systems were preserved and all other propriospinal systems and direct descending systems were severed. In 9 cats following spinal cord hemisection at around C1, at interval of 11-71 days the second hemisection was carried out at thoracic cord about T12 (C-T; cervico-thoracic bilateral serial hemisection). In this group homolateral and crossed propriospinal systems were left intact. In the single hemisection group, the phase relationships of all the six combinations of limbs were quite similar to normal group. Hence for the control of the phase relation during locomotion, only onesided neuronal circuits were needed. In both T-T and C-T group, polar diagram analysis revealed that the phase relationships were completely disturbed in any combination of the forelimbs and hindlimbs. It was concluded that the direct descending systems rather than propriospinal systems play important roles in control of phase relationship during locomotion.

Afferent Pathways↗
PubMed1979

[Activity of interneurons of the lumbar region of the spinal cord during fictive locomotion of thalamic cats].

Impulse activity of lumbar interneurons was recorded extracellularly during fictious locomotion of thalamic cats. Neurons whose activity was modulated in the rhythm of fictitious locomotion were revealed in the lateral intermediate zone and in the lateral ventral born. 41.2% of these neurons were mainly activated at the phase of "flexion", 48.5%--at the phase of "extension" and 10.3%--at both phases. Neurons with tonically increasing or decreasing activity during rhythmic efferent discharges and neurons whose activity did not change during fictitious locomotion were also observed. All these types of neurons were similarly activated during late discharges in efferent nerves. But in this case the depth of modulation of neuronal activity was lower than during fictitious locomotion. Afferent inputs to the recorded interneurons were also investigated. The neuronal organization of the spinal locomotor generator is discussed on the basis of the obtained data.

Animals↗
PubMed1981

[Retuning of segmental responses to peripheral stimulation during fictive locomotion in cats].

Segmental reflex responses of the lumbosacral spinal cord to peripheral afferent stimulation were investigated in immobilized decorticated cats before and during fictitious locomotion. Appearance of fictitious locomotion was accompanied by an increase of the N1 component of the dorsal cord potential and of the dorsal root potential. Modulation of these responses depending on the phase of fictitious locomotion was observed against a background of their tonic increase. The N1 component and dorsal root potential had larger amplitudes when they appear at the end of the "extensor" phase and at the beginning of the "flexor" phase and smaller amplitudes when they were evoked at the end of the "flexor" phase and at the beginning of the "extensor" phase. Poly- and monosynaptic reflex responses of motoneurons revealed the same phase dependence during fictitious locomotion. Mechanisms and physiological significance of the revealed retuning of segmental reflex responses are discussed on the basis of the obtained data.

Animals↗
PubMed1983

The stride cycle of the cat: the modelling of locomotion by computerized analysis of automatic recordings.

The present study gives a general description of the locomotor patterns of the intact cat. Overground and treadmill locomotion were studied by means of automatic recordings of limb movements, ground reaction forces and electromyograms. The data processing and automatic recording techniques which were used are described; one recording technique is based on a television system, another on the Selspot I system. The data were processed and analysed interactively with a computer, which allows a statistical analysis of many strides in a fast and accurate way. The amplitudes and time course of movements in different joints and different limbs were studied at different velocities of locomotion and correlated to each other and to parameters such as the onset and termination of electromyographic activity in different muscles. No element of the stride cycle was found to be constant: The amplitudes of joint angles and limb excursions as well as the durations of the different phases of the stride cycle can be adapted to maintain an appropriate coordination between the limbs. The durations of all phases of the stride cycle decrease with increasing speed of locomotion. The durations of the support and extension phases change proportionally more than of the swing and flexion phases and they all appear to be linearly related to the stride cycle duration. The relations of the flexion duration with the stride cycle duration for the different joints are usually different from each other and after a disturbance of the movements of a forelimb the duration of knee and ankle flexion of the homolateral limb can increase and the first extension phase of knee and ankle decrease, whereas they usually increase or decrease together. This further supports the hypothesis that every joint is controlled by a flexion and extension unit pattern generator. The amplitude of the joint angle excursions during the different phases of the stride cycle are better controlled than the absolute joint angles at the onset and termination of these phases. The position of the toe at touch-down was studied at different velocities of locomotion and was found to remain comparatively constant. There is a correlation between hip, knee and ankle joint angles at touch-down, which was found to be of importance for the precise positioning of the foot.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1983

Forward locomotion elicited by electrical stimulation in the diencephalon and mesencephalon of the awake rat.

Stimulation electrodes were implanted in 63 rats at a total of 208 sites in the diencephalon and midbrain. The sites were tested for elicited forward locomotion, i.e., alternate stepping of the forelimbs and/or hindlimbs, while the rats stood on a treadmill belt in a 27 X 9 X 24-cm chamber. Current levels of 50-300 microA and pulse frequencies of 50, 100 and 154 Hz were presented as single 5-sec trains and as 20 repetitive trains of 1-sec duration with a 3-sec intertrain interval. Locomotion was elicited with low current (50 or 100 microA) single trains at 28% of the sites. Of the regions sufficiently well sampled to warrent comparisons, two showed high densities of locomotion-positive sites with single low current trains. They were the medial hypothalamus (the dorsomedial and the posterior nuclei) and the ventral tegmental area. The medial forebrain bundle and the zona incerta were generally positive but many sites in these regions required repetitive trains. Among the regions with few locomotion-positive sites were the subthalamic nucleus, the fields of Forel and the habenular complex. In the dorsal midbrain, in and around the central gray, low current single trains elicited leaping. The results are discussed in terms of the existence of a delimited subthalamic locomotor region and a ventral midbrain locomotor system independent of a dorsal midbrain system.

Animals↗