Coordination of legs during straight walking and turning in Drosophila melanogaster

Leg coordination of Drosophila melanogaster was studied using frame-by-frame film analysis. 1. For fastest walking alternating tripod coordination is observed which slightly deviates towards tetrapody as a function of step period. During acceleration or deceleration legs may transiently recover in diagonal pairs. 2. Mean step length increases with step frequency. 3. Mean recovery stroke duration increases with step period and plateaus beyond a period of about 110 ms. Middle legs recover significantly faster than others. 4. Ipsilateral footprints are transversally separated. 5. Walking is usually initiated in tripod coordination (frequently in combination with a turn), otherwise in an accelerating sequence which rapidly shifts towards tripod pattern. Flies can stop abruptly or decelerate over about one metachronal wave. 6. Short interruptions in walking are observed. Legs interrupted during swing phase stay lifted and finish recovery thereafter. 7. Slight changes in walking direction are obtained by altering step lengths only. Tight turns are composed of two or three phases with backward, zero and forward translatory components. In fast turning tripod coordination is maintained. Otherwise body sides can decouple widely. In all turns numbers of contralateral metachronal waves were equal. Results are compared to those for other walking insects and their relevance in screens for locomotor mutants is discussed.     

Effect of stable and unstable load carriage on walking gait variability,dynamic stability and muscle activity of older adults

Load carriage perturbs the neuromuscular system, which can be impaired due to ageing. The ability to counteract perturbations is an indicator of neuromuscular function but if the response is insufficient the risk of falls will increase. However, it is unknown how load carriage affects older adults. Fourteen older adults (65 ± 6 years) attended a single visit during which they performed 4 min of walking in 3 conditions, unloaded, stable backpack load and unstable backpack load. During each walking trial, 3-dimensional kinematics of the lower limb and trunk movements and electromyographic activity of 6 lower limb muscles were recorded. The local dynamic stability (local divergence exponents), joint angle variability and spatio-temporal variability were determined along with muscle activation magnitudes. Medio-lateral dynamic stability was lower (p = 0.018) and step width (p = 0.019) and step width variability (p = 0.015) were greater in unstable load walking and step width variability was greater in stable load walking (p = 0.009) compared to unloaded walking. However, there was no effect on joint angle variability. Unstable load carriage increased activity of the Rectus Femoris (p = 0.001) and Soleus (p = 0.043) and stable load carriage increased Rectus Femoris activity (p = 0.006). These results suggest that loaded walking alters the gait of older adults and that unstable load carriage reduces dynamic stability compared to unloaded walking. This can potentially increase the risk of falls, but also offers the potential to use unstable loads as part of fall prevention programmes.     

Trunk-Pelvis motions and spinal loads during upslope and downslope walking among persons with transfemoral amputation

Larger trunk and pelvic motions in persons with (vs. without) lower limb amputation during activities of daily living (ADLs) adversely affect the mechanical demands on the lower back. Building on evidence that such altered motions result in larger spinal loads during level-ground walking, here we characterize trunk-pelvic motions, trunk muscle forces, and resultant spinal loads among sixteen males with unilateral, transfemoral amputation (TFA) walking at a self-selected speed both up (“upslope”; 1.06 ± 0.14 m/s) and down (“downslope”; 0.98 ± 0.20 m/s) a 10-degree ramp. Tri-planar trunk and pelvic motions were obtained (and ranges-of-motion [ROM] computed) as inputs for a non-linear finite element model of the spine to estimate global and local muscle (i.e., trunk movers and stabilizers, respectively) forces, and resultant spinal loads. Sagittal- (p = 0.001), frontal- (p = 0.004), and transverse-plane (p < 0.001) trunk ROM, and peak mediolateral shear (p = 0.011) and local muscle forces (p = 0.010) were larger (respectively 45, 35, 98, 70, and 11%) in upslope vs. downslope walking. Peak anteroposterior shear (p = 0.33), compression (p = 0.28), and global muscle (p = 0.35) forces were similar between inclinations. Compared to previous reports of persons with TFA walking on level ground, 5–60% larger anteroposterior and mediolateral shear observed here (despite ∼0.25 m/s slower walking speeds) suggest greater mechanical demands on the low back in sloped walking, particularly upslope. Continued characterization of trunk motions and spinal loads during ADLs support the notion that repeated exposures to these larger-than-normal (i.e., vs. level-ground walking in TFA and uninjured cohorts) spinal loads contribute to an increased risk for low back injury following lower limb amputation.     

Gait Transitions in Human Infants: Coping with Extremes of Treadmill Speed

Spinal pattern generators in quadrupedal animals can coordinate different forms of locomotion, like trotting or galloping, by altering coordination between the limbs (interlimb coordination). In the human system, infants have been used to study the subcortical control of gait, since the cerebral cortex and corticospinal tract are immature early in life. Like other animals, human infants can modify interlimb coordination to jump or step. Do human infants possess functional neuronal circuitry necessary to modify coordination within a limb (intralimb coordination) in order to generate distinct forms of alternating bipedal gait, such as walking and running? We monitored twenty-eight infants (7–12 months) stepping on a treadmill at speeds ranging between 0.06–2.36 m/s, and seventeen adults (22–47 years) walking or running at speeds spanning the walk-to-run transition. Six of the adults were tested with body weight support to mimic the conditions of infant stepping. We found that infants could accommodate a wide range of speeds by altering stride length and frequency, similar to adults. Moreover, as the treadmill speed increased, we observed periods of flight during which neither foot was in ground contact in infants and in adults. However, while adults modified other aspects of intralimb coordination and the mechanics of progression to transition to a running gait, infants did not make comparable changes. The lack of evidence for distinct walking and running patterns in infants suggests that the expression of different functional, alternating gait patterns in humans may require neuromuscular maturation and a period of learning post-independent walking.     

Influence of loading parallel to the body axis on the walking coordination of an insect

It is often reported in the early literature that insects walk with the legs protacting in diagonal pairs rather than the triplet of three legs associated with the tripod step pattern. The diagonal pattern implies that legs of the same segment have a phase relationship significantly different from 0.5. Such a pattern of leg recovery has been demonstrated quantitatively for the stick insect (Graham, 1972). Such patterns occur in several insects and systematic asymmetry can even be detected in the earliest quantitative study on cockroaches (Hughes, 1957) when the animals are walking slowly. More recently Spirito and Mushrush (1979) have reported systematic deviations from a phase of 0.5 similar to those observed in stick insects. Asymmetry has also been quantitatively demonstrated in Katydids (Graham, 1978) and has recently been observed in Mantid walking (Thomson, personal communication). This phenomenon seems to be a general characteristic of slow walking coordination in insects. In stick insects asymmetry only becomes obvious in gait II at slow speeds although there can be systematic differences in ipsilateral coordination on right and left sides even at the highest speeds in this gait (Graham, 1972).     

Muscle activation profiles about the knee during Tai-Chi stepping movement compared to the normal gait step.

The purpose of this study was to investigate knee muscle activity patterns in experienced Tai-Chi (TC) practitioners during normal walking and TC stepping. The electromyographic (EMG) activity of vastus lateralis (VL), vastus medialis (VM), bicep femoris (BF), and gastrocnemius (GS) muscles of 11 subjects (five females and six males) during the stance phase of normal walking was compared to stance phase of a TC step. Knee joint motion was also monitored by using an Optotrak motion analysis system. Raw EMG was processed by root-mean-square (RMS) technique using a time constant of 50 ms, and normalized to maximum of voluntary contraction for each muscle, referred to as normalized RMS (nRMS). Peak nRMS and co-contraction (quantified by co-contraction index) during stance phase of a gait cycle and a TC step were calculated. Paired t-tests were used to compare the difference for each muscle group peak and co-contraction pair between the tasks. The results showed that only peak values of nRMS in quadriceps and co-contraction were significantly greater in TC stepping compared to normal walking (Peak values of nRMS for VL were 26.93% for normal walking and 52.14% for TC step, p=0.001; VM are 29.12% for normal walking and 51.93% for TC stepping, p=0.028). Mean co-contraction index for VL-BF muscle pairs was 13.24+/-11.02% during TC stepping and 9.47+/-7.77% in stance phase of normal walking (p=0.023). There was no significant difference in peak values of nRMS in the other two muscles during TC stepping compared to normal walking. Preliminary EMG profiles in this study demonstrated that experienced TC practitioners used relatively higher levels of knee muscle activation patterns with greater co-contraction during TC exercise compared to normal walking.     

The influence of load and leg amputation upon coordination in walking crustaceans: A model calculation

The following results were obtained by earlier authors when investigating the leg coordination of walking crustaceans (Decepoda): 1) After a leg is amputated, its stump moves in anti-phase with the next posterior intact leg. This corresponds to the coordination of intact animals. The stump, however, moves in-phase with the next anterior intact leg which contrasts with the coordination of intact animals (Clarac and Chasserat, 1979; Clarac, 1981). 2) Different results have been reported for the relation between the return stroke duration and step period: some authors found a significant dependency (e.g. MacMillan, 1975), others found none (e.g. Ayers and Davis, 1977). The calculation presented here shows, that these results can be described by a model incorporating the following assumptions: A) The forces developed by both, return stroke and power stroke muscles depend upon the load under which the leg walks. B) The influences which produce the coordinating effects found by Clarac and Chasserat for amputees also exist in intact animals and their strength depends upon the intensity of the motor output of the controlling leg. Within the model the selection of protraction or retraction is made at a “central unit” which calculates a value corresponding to the sum of graded inputs from several sources. The resulting fluctuation in this value might be considered analogous to graded oscillations recorded from central non-spiking interneurons. Qualitatively the model describes similar results obtained from insects.     

External load can alter the energy cost of prolonged exercise

The present study was undertaken to examine the energy cost of prolonged walking while carrying a backpack load. Six trained subjects were tested while walking for 120 min on a treadmill at a speed of 1.25 m.s-1 and 5% elevation with a well fitted backpack load of 25 and 40 kg alternately. Carrying 40 kg elicited a significantly higher (p less than 0.01) energy cost than 25 kg. Furthermore, whereas carrying 25 kg resulted in a constant energy cost, 40 kg yielded a highly significant (p less than 0.05) increase in energy cost over time. The study implies that increase in load causes physical fatigue, once work intensity is higher than 50% maximal work capacity. This is probably due to altered locomotion biomechanics which in turn lead to the increase in energy cost. Finally, the prediction model which estimates energy cost while carrying loads should be used with some caution when applied to heavy loads and long duration of exercise, since it might underestimate the actual energy cost.     

Increasing step width reduces the requirements for subtalar joint moments and powers

The subtalar joint (STJ) contributes to the absorption and generation of mechanical energy (and power) during walking to maintain frontal plane stability. Previous observational studies have suggested that there may be a relationship between step width and STJ supination moment. This study directly tests the hypothesis that walking with a step width greater than preferred would reduce STJ moments, energy absorption, and power generation requirements, while increasing energy absorption at the hip during initial contact. Participants (n = 12, 7 females) were asked to walk on an instrumented treadmill at a constant velocity and cadence at a range of fixed step widths ranging from 0.1 to 0.4 times leg length (L). Walking at step widths greater than preferred (0.149 ± 0.04 L) reduced peak STJ moments at initial contact and propulsion which subsequently reduced the negative and positive work performed at the STJ. There was a 43% reduction in energy absorption (negative work) and approximately 30% decrease in positive work at the STJ as step width increased from 0.1 L to 0.4 L. An increase in energy absorption at the knee and hip was evident with an increase in step width during initial contact, although minimal mechanical changes were observed at the proximal joints during propulsion. These results suggest an increase in step width reduces the forces generated by muscles at the STJ across stance and is therefore likely to be beneficial in the prevention and treatment of their injuries. In terms of rehabilitation, the increase in mechanical costs occurring due to an increase in energy absorption by the hip and knee is of minimal concern.     

The effects of railroad ballast surface and slope on rearfoot motion in walking

The purpose of this study was to investigate the effects of transversely sloped ballasted walking surface on gait and rearfoot motion (RFM) parameters. Motion analysis was performed with 20 healthy participants (15 male and 5 female) walking in six surface-slope conditions: two surfaces (solid and ballasted) by three slopes (0, 5, and 10 degrees). The gait parameters (walking velocity, step length, step rate, step width, stance time, and toe-out angle) showed significant surface effect (p = .004) and surface-slope interaction (p = .017). The RFM motion parameters (peak everted/inverted position, eversion/inversion velocity, and acceleration) revealed significant surface (p = .004) and slope (p = .024) effects. The ballasted conditions showed more cautious gait patterns with lower walk velocity, step length, and step rate and longer stance time. In the RFM parameters, the slope effect was more notable in the solid conditions due to the gait adaptations in the ballasted conditions. Ballast conditions showed reduced inversion and increased eversion and RFM range. The RFM data were comparable to other typical walking conditions but smaller than those from running.     

Measurement of spatial gait parameters from footprints of dairy cows

The variability in dairy cow gait characteristics, determined by measurements of footprints (trackway measurements), was analysed. Seven gait parameters were determined from 32 non-lame dairy cows during free-speed walking on a slatted concrete walkway. The footprints were revealed by application of a thin lime powder-slurry layer to the walkway surface. The cows were observed on two test occasions with a 3-week interval, with measurements from four consecutive strides used within each test session. The variance components for cow, test and cow-test interaction were estimated by a residual (restricted) maximum likelihood method. The percentage of each variance component was calculated to assess the relative impact of each factor on total variance. Between-test variation was generally low, suggesting that cows maintain the same average gait pattern, at least over a 3-week period. The proportion of within-test variation was considerable for most trackway measurements. Stride length, step angle, step width and tracking (overlap) showed low to moderate within-test variation (12% to 27%), whereas for mediolateral displacement of rear feet and step length it was rather high (54% and 62%, respectively). Within-test variation in step asymmetry was very high (77%), suggesting the occurrence of natural, non-systematic changes in inter-limb coordination in non-lame cows. For better understanding the gait pattern in non-lame cows, linear associations between the trackway measurements and with body size were assessed. It was concluded that trackway measurements were able to describe the gait pattern in walking cows under dairy farm conditions. However, considering the relatively high within-test variation in gait, several strides should be used to obtain a representative gait pattern.     

Motor output to the protractor and retractor coxae muscles in stick insects walking on a treadwheel

ABSTRACT. The motor output to the protractor and retractor mucles moving the coxa of the middle leg of Carausius morosus was recorded from the thoracic nerves during walking on a treadwheel. The leg movements on the wheel were generally similar to those found in free-walking animals, but tripod coordination was relatively independent of period, and the coordination of the adult animal on the wheel was most closely related to that found in free-walking first instars. The activity of a common inhibitor and four excitatory axons of the retractor and an excitatory axon of the protractor were followed for 850 steps (in six animals) to give a summary of the behaviour of the different units. The motor activity is less stereotyped than that previously reported for insects. There was strong reciprocity between the antagonists, but this was not directly correlated with the forward and backward movements of the legs. The first part of the stance phase of the leg was accompanied by a strong burst in the protractor nerve and relatively little retractor activity. This was followed by the main retractor burst which occupied the last 60% of the stance phase. The results are compared with motor output records of the locust and with earlier force-plate measurements on the stick insect. It must be concluded that the mesothoracic leg initially resists forward movement of the body by the other legs during a typical walking step.     

Fast backward steps and detachment of single kinesin molecules measured under a wide range of loads

To understand force generation under a wide range of loads, the stepping of single kinesin molecules was measured at loads from −20 to 42 pN by optical tweezers with high temporal resolution. The optical trap has been improved to halve positional noise and increase bandwidth by using 200-nm beads. The step size of the forward and backward steps was 8.2 nm even over a wide range of loads. Histograms of the dwell times of backward steps and detachment fit well to two independent exponential equations with fast (~0.4 ms) and slow (>3 ms) time constants, indicating the existence of a fast step in addition to the conventional slow step. The dwell times of the fast steps were almost independent of the load and ATP concentration, while those of the slow backward steps and detachment depended on those. We constructed the kinetic model to explain the fast and slow steps under a wide range of loads.     

Older Adults Show Preserved Equilibrium but Impaired Step Length Control in Motor-Equivalent Stabilization of Gait

Stable walking depends on the coordination of multiple biomechanical degrees of freedom to ensure the dynamic maintenance of whole-body equilibrium as well as continuous forward progression. We investigated adult age-related differences in whole-body coordination underlying stabilization of center of mass (CoM) position and step pattern during locomotion. Sixteen younger (20-30 years) and 16 healthy older men (65–80 years) walked on a motorized treadmill at 80%, 100% and 120% of their self-selected preferred speed. Preferred speeds did not differ between the age groups. Motor-equivalent stabilization of step parameters (step length and width) and CoM position relative to the support (back and front foot) was examined using a generalized covariation analysis. Across age groups, covariation indices were highest for CoM position relative to the front foot, the measure most directly related to body equilibrium. Compared to younger adults, older adults showed lower covariation indices with respect to step length, extending previous findings of age-related differences in motor-equivalent coordination. In contrast, no reliable age differences were found regarding stabilization of step width or any of the CoM parameters. The observed pattern of results may reflect robust prioritization of balance over step pattern regularity, which may be adaptive in the face of age-associated sensorimotor losses and decline of coordinative capacities.     

Resonant frequencies of arms and legs identify different walking patterns

The present study is aimed at investigating changes in the coordination of arm and leg movements in young healthy subjects. It was hypothesized that with changes in walking velocity there is a change in frequency and phase coupling between the arms and the legs. In addition, it was hypothesized that the preferred frequencies of the different coordination patterns can be predicted on the basis of the resonant frequencies of arms and legs with a simple pendulum model. The kinematics of arms and legs during treadmill walking in seven healthy subjects were recorded with accelerometers in the sagittal plane at a wide range of different velocities (i.e., 0.3-1. 3m/s). Power spectral analyses revealed a statistically significant change in the frequency relation between arms and legs, i.e., within the velocity range 0.3-0.7m/s arm movement frequencies were dominantly synchronized with the step frequency, whereas from 0.8m/s onwards arm frequencies were locked onto stride frequency. Significant effects of walking speed on mean relative phase between leg and arm movements were found. All limb pairs showed a significantly more stable coordination pattern from 0.8 to 1.0m/s onwards. Results from the pendulum modelling demonstrated that for most subjects at low-velocity preferred movement frequencies of the arms are predicted by the resonant frequencies of individual arms (about 0.98Hz), whereas at higher velocities these are predicted on the basis of the resonant frequencies of the individual legs (about 0.85Hz). The results support the above-mentioned hypotheses, and suggest that different patterns of coordination, as shown by changes in frequency coupling and phase relations, can exist within the human walking mode.     

Response time is more important than walking speed for the ability of older adults to avoid a fall after a trip.

We previously reported that the probability of an older adult recovering from a forward trip and using a "lowering" strategy increases with decreased walking velocity and faster response time. To determine the within-subject interaction of these variables we asked three questions: (1) Is the body orientation at the time that the recovery foot is lowered to the ground ("tilt angle") critical for successful recovery? (2) Can a simple inverted pendulum model, using subject-specific walking velocity and response time as input variables, predict this body orientation, and thus success of recovery? (3) Is slower walking velocity or faster response time more effective in preventing a fall after a trip? Tilt angle was a perfect predictor of a successful recovery step, indicating that the recovery foot placement must occur before the tilt angle exceeds a critical value of between 23 degrees and 26 degrees from vertical. The inverted pendulum model predicted the tilt angle from walking velocity and response time with an error of 0.4+/-2.2 degrees and a correlation coefficient of 0.93. The model predicted that faster response time was more important than slower walking velocity for successful recovery. In a typical individual who is at risk for falling, we predicted that a reduction of response time to a normal value allows a 77% increase in safe walking velocity. The mathematical model produced patient-specific recommendations for fall prevention, and suggested the importance of directing therapeutic interventions toward improving the response time of older adults.     

Vertical displacement of the centre of mass during walking in people with diabetes and diabetic neuropathy does not explain their higher metabolic cost of walking

People with diabetes display biomechanical gait alterations compared to controls and have a higher metabolic cost of walking (CoW), but it remains unknown whether differences in the vertical displacement of the body centre of mass (CoM) may play a role in this higher CoW. The aim of this study was to investigate vertical CoM displacement (and step length as a potential underpinning factor) as an explanatory factor in the previously observed increased CoW with diabetes. Thirty-one non-diabetic controls (Ctrl); 22 diabetic patients without peripheral neuropathy (DM) and 14 patients with moderate/severe Diabetic Peripheral Neuropathy (DPN), underwent gait analysis using a motion analysis system and force plates while walking at a range of matched speeds between 0.6 and 1.6 m/s. Vertical displacement of the CoM was measured over the gait cycle, and was not different in either diabetes patients with or without diabetic peripheral neuropathy compared to controls across the range of matched walking speeds examined (at 1 m/s: Ctrl: 5.59 (SD: 1.6), DM: 5.41 (1.63), DPN: 4.91 (1.66) cm; p > 0.05). The DPN group displayed significantly shorter steps (at 1 m/s: Ctrl: 69, DM: 67, DPN: 64 cm; p > 0.05) and higher cadence (at 1 m/s: Ctrl: 117 (SD1.12), DM: 119 (1.08), DPN: 122 (1.25) steps per minute; p > 0.05) across all walking speeds compared to controls. The vertical CoM displacement is therefore unlikely to be a factor in itself that contributes towards the higher CoW observed recently in people with diabetic neuropathy. The higher CoW in patients with diabetes may not be explained by the CoM displacement, but rather may be more related to shorter step lengths, increased cadence and the associated increased internal work and higher muscle forces developed by walking with more flexed joints.     

Predictive Simulation Generates Human Adaptations during Loaded and Inclined Walking

Predictive simulation is a powerful approach for analyzing human locomotion. Unlike techniques that track experimental data, predictive simulations synthesize gaits by minimizing a high-level objective such as metabolic energy expenditure while satisfying task requirements like achieving a target velocity. The fidelity of predictive gait simulations has only been systematically evaluated for locomotion data on flat ground. In this study, we construct a predictive simulation framework based on energy minimization and use it to generate normal walking, along with walking with a range of carried loads and up a range of inclines. The simulation is muscle-driven and includes controllers based on muscle force and stretch reflexes and contact state of the legs. We demonstrate how human-like locomotor strategies emerge from adapting the model to a range of environmental changes. Our simulation dynamics not only show good agreement with experimental data for normal walking on flat ground (92% of joint angle trajectories and 78% of joint torque trajectories lie within 1 standard deviation of experimental data), but also reproduce many of the salient changes in joint angles, joint moments, muscle coordination, and metabolic energy expenditure observed in experimental studies of loaded and inclined walking.     

Effects of passive Bi-axial ankle stretching while walking on uneven terrains in older adults with chronic stroke

Many people with stroke experience foot drop while walking. Further, walking on uneven surfaces is a common fall risk for these people that hinder with their daily life activities. In addition, a few years after a stroke, lower-limb exercises become less focused, especially the ankle joint movement. The objective of this study is to determine the gait performance of older adults with chronic stroke on an uneven surface in relation to ankle mobility after a four-week bi-axial ankle range of motion (ROM) exercise session. Fifteen older adults with chronic post-stroke hemiparesis (N = 15; mean age = 65 years) participated in a total of 12 bi-axial ankle ROM exercises that consisted of three 30-min training sessions per week for four weeks. Basic clinical tests and gait performance in even and uneven surfaces were evaluated before and after training. Participants with chronic post-stroke hemiparesis showed significantly improved ankle functions, decreased ankle stiffness (from 0.140 ± 0.059 to 0.128 ± 0.067 N·m/°; p = 0.025), and increased paretic ankle passive ROMs (dorsiflexion(DF)/plantarflexion(PF): from 27.3 ± 14.7° to 50.6 ± 10.3°, p < 0.001; inversion(INV)/eversion(EV): 21.7 ± 9.7° to 28.6 ± 9.9°; p = 0.033) after training. They exhibited significant improvements in the walking performance over an uneven surface, step kinematics (walking speed 0.257 ± 0.17 to 0.320 ± 0.178 m/s; p = 0.017; step length: 0.214 ± 0.109 to 0.243 ± 0.108 m; p = 0.009), and clinical balance and mobility (Berg balance scale: 47.2 ± 4.7 to 50.1 ± 3.9, p = 0.0001; timed-up and go test: 23.9 ± 10.3 to 20.2 ± 7.0 s, p = 0.0156). This study is the first research to investigate the walking performance on uneven surfaces in the elderly with chronic stroke in relation to the ankle biomechanical property changes.     

Marching to the beat of the same drummer: the spontaneous tempo of human locomotion.

Laboratory studies have suggested that the preferred cadence of walking is approximately 120 steps/min, and the vertical acceleration of the head exhibits a dominant peak at this step frequency (2 Hz). These studies have been limited to short periods of walking along a predetermined path or on a treadmill, and whether such a highly tuned frequency of movement can be generalized to all forms of locomotion in a natural setting is unknown. The aim of this study was to determine whether humans exhibit a preferred cadence during extended periods of uninhibited locomotor activity and whether this step frequency is consistent with that observed in laboratory studies. Head linear acceleration was measured over a 10-h period in 20 subjects during the course of a day, which encompassed a broad range of locomotor (walking, running, cycling) and nonlocomotor (working at a desk, driving a car, riding a bus or subway) activities. Here we show a highly tuned resonant frequency of human locomotion at 2 Hz (SD 0.13) with no evidence of correlation with gender, age, height, weight, or body mass index. This frequency did not differ significantly from the preferred step frequency observed in the seminal laboratory study of Murray et al. (Murray MP, Drought AB, and Kory RC. J Bone Joint Surg 46A: 335-360, 1964). [1.95 Hz (SD 0.19)]. On the basis of the frequency characteristics of otolith-spinal reflexes, which drive lower body movement via the lateral vestibulospinal tract, and otolith-mediated collic and ocular reflexes that maintain gaze when walking, we speculate that this spontaneous tempo of locomotion represents some form of central "resonant frequency" of human movement.