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.     

System identification of muscle–joint interactions of the cat hind limb during locomotion

Neurophysiological experiments in walking cats have shown that a number of neural control mechanisms are involved in regulating the movements of the hind legs during locomotion. It is experimentally hard to isolate individual mechanisms without disrupting the natural walking pattern and we therefore introduce a different approach where we use a model to identify what control is necessary to maintain stability in the musculo-skeletal system. We developed a computer simulation model of the cat hind legs in which the movements of each leg are produced by eight limb muscles whose activations follow a centrally generated pattern with no proprioceptive feedback. All linear transfer functions, from each muscle activation to each joint angle, were identified using the response of the joint angle to an impulse in the muscle activation at 65 postures of the leg covering the entire step cycle. We analyzed the sensitivity and stability of each muscle action on the joint angles by studying the gain and pole plots of these transfer functions. We found that the actions of most of the hindlimb muscles display inherent stability during stepping, even without the involvement of any proprioceptive feedback mechanisms, and that those musculo-skeletal systems are acting in a critically damped manner, enabling them to react quickly without unnecessary oscillations. We also found that during the late swing, the activity of the posterior biceps/semitendinosus (PB/ST) muscles causes the joints to be unstable. In addition, vastus lateralis (VL), tibialis anterior (TA) and sartorius (SAT) muscle-joint systems were found to be unstable during the late stance phase, and we conclude that those muscles require neuronal feedback to maintain stable stepping, especially during late swing and late stance phases. Moreover, we could see a clear distinction in the pole distribution (along the step cycle) for the systems related to the ankle joint from that of the other two joints, hip or knee. A similar pattern, i.e., a pattern in which the poles were scattered over the s-plane with no clear clustering according to the phase of the leg position, could be seen in the systems related to soleus (SOL) and TA muscles which would indicate that these muscles depend on neural control mechanisms, which may involve supraspinal structures, over the whole step cycle.     

Limited transfer of podokinetic after-rotation from kneeling to standing

Following stepping in place on a rotating treadmill, subjects inadvertently rotate when asked to step in place without vision. This response is called podokinetic after-rotation (PKAR). The purpose of this study was to determine whether PKAR transfers across tasks with different lower limb configurations, that is, from kneeling to stepping. We hypothesized that PKAR would transfer from kneeling to stepping for two reasons. First, there have been several demonstrations of robust PKAR transfer from forward to backward walking, stepping to hopping, running to walking, and from one limb to another. Second, we thought that afferent information regarding hip rotation was likely a key source of information to guide podokinetic adaptation and since hip rotation would be preserved in both stimulation conditions we expected to see little difference between the conditions. We compared the PKAR responses recorded in standing from 13 healthy young volunteers after either standard stepping on a rotating treadmill or stepping while kneeling (kneel-stepping) on a rotating treadmill. Subjects performed two sessions of podokinetic (PK) stimulation, one stepping and one kneel-stepping on a rotating treadmill. Following the PK stimulation, subjects were blindfolded and asked to step in place in standing. Angular velocity of trunk rotation during PKAR from the two sessions was calculated and compared. The maximum angular velocities of PKAR recorded in stepping were significantly higher following the stepping session than following the kneel-stepping session (9.10 +/- 8.9 and 2.94 +/- 1.6 deg/s, respectively). This was despite the fact that hip rotation excursion during PK stimulation was significantly greater in kneel-stepping (18.7 +/- 3.6 deg) than in stepping (12.2 +/- 2.6 deg). These results indicate very little transfer from kneeling to stepping and suggest that afferent information regarding hip rotation is not the only or even the major source of limb position sense information used to drive locomotor trajectory adaptation.     

Dominance of local sensory signals over inter-segmental effects in a motor system: experiments

Legged locomotion requires that information local to one leg, and inter-segmental signals coming from the other legs are processed appropriately to establish a coordinated walking pattern. However, very little is known about the relative importance of local and inter-segmental signals when they converge upon the central pattern generators (CPGs) of different leg joints. We investigated this question on the CPG of the middle leg coxa?Ctrochanter (CTr)-joint of the stick insect which is responsible for lifting and lowering the leg. We used a semi-intact preparation with an intact front leg stepping on a treadmill, and simultaneously stimulated load sensors of the middle leg. We found that middle leg load signals induce bursts in the middle leg depressor motoneurons (MNs). The same local load signals could also elicit rhythmic activity in the CPG of the middle leg CTr-joint when the stimulation of middle leg load sensors coincided with front leg stepping. However, the influence of front leg stepping was generally weak such that front leg stepping alone was only rarely accompanied by switching between middle leg levator and depressor MN activity. We therefore conclude that the impact of the local sensory signals on the levator?Cdepressor motor system is stronger than the inter-segmental influence through front leg stepping.     

Limited transfer of podokinetic after-rotation from kneeling to standing

Following stepping in place on a rotating treadmill, subjects inadvertently rotate when asked to step in place without vision. This response is called podokinetic after-rotation (PKAR). The purpose of this study was to determine whether PKAR transfers across tasks with different lower limb configurations, that is, from kneeling to stepping. We hypothesized that PKAR would transfer from kneeling to stepping for two reasons. First, there have been several demonstrations of robust PKAR transfer from forward to backward walking, stepping to hopping, running to walking, and from one limb to another. Second, we thought that afferent information regarding hip rotation was likely a key source of information to guide podokinetic adaptation and since hip rotation would be preserved in both stimulation conditions we expected to see little difference between the conditions. We compared the PKAR responses recorded in standing from 13 healthy young volunteers after either standard stepping on a rotating treadmill or stepping while kneeling (kneel-stepping) on a rotating treadmill. Subjects performed two sessions of podokinetic (PK) stimulation, one stepping and one kneel-stepping on a rotating treadmill. Following the PK stimulation, subjects were blindfolded and asked to step in place in standing. Angular velocity of trunk rotation during PKAR from the two sessions was calculated and compared. The maximum angular velocities of PKAR recorded in stepping were significantly higher following the stepping session than following the kneel-stepping session (9.10?±?8.9 and 2.94?±?1.6?deg/s, respectively). This was despite the fact that hip rotation excursion during PK stimulation was significantly greater in kneel-stepping (18.7?±?3.6?deg) than in stepping (12.2?±?2.6?deg). These results indicate very little transfer from kneeling to stepping and suggest that afferent information regarding hip rotation is not the only or even the major source of limb position sense information used to drive locomotor trajectory adaptation.     

Walk-, run- and gallop-like gait patterns in human sideways locomotion

The purpose of this study is to examine the characteristics of gait patterns in human preferred sideways locomotion at increasing speeds. Fifteen healthy young males were asked to step sideways on a treadmill at various speeds of 1.3–6.1 km/h. The times of foot contact and take-off were analyzed. Three gait patterns were observed. At slow speeds, all of the subjects performed a walk-like pattern. When the treadmill speed exceeded approximately 3.5 km/h, the subjects preferred gait patterns with a flight phase. Most of the subjects performed an asymmetric gait pattern that was similar to a forward gallop, whereas only two out of fifteen subjects performed a run-like gait pattern. Because the left and right legs are positioned along the movement direction, it might be more efficient to divide roles between the leading and trailing limbs at high speeds: the leading limb functions to produces breaking and vertical force, and the trailing limb mainly absorbs the impact of foot contact and generates propulsive forces.     

Effects of transcutaneous electrical spinal cord stimulation on stepping patterns during walking

Effects of transcutaneous electrical spinal cord stimulation (tESCS) on the parameters of stepping movements in healthy subjects were investigated during two kinds of activity: walking on a moving treadmill belt (active treadmill) as well as pushing the treadmill belt by effort of the legs (passive treadmill). It was found that the total interference electromyogram (EMG) activity during stepping performance on a passive treadmill was 1.5–2 times higher than during stepping on an active treadmill. In addition, the amplitude of angular displacement of the hip joint and ankle was 2.5 times and 1.7 times higher, respectively, during passive vs. active treadmill, while the duration of stepping cycle decreased by 19%. Although the muscles were exposed to different load and the parameters of motion on the active and passive treadmill were different, tESCS caused an increase in the total EMG activity in 96% of cases both on the active and on the passive treadmill. In both cases, the stepping cycle period decreased by 4–43% in all subjects. These results suggest that tESCS can affect voluntary stepping patterns under conditions of different afferent control.     

Influence of walking on swimmeret beating in the lobster Homarus gammarus

Influence of walking on swimmeret beating in intact lobsters, Homarus gammarus, has been analyzed using a treadmill experimental device. Belt movement activates both leg stepping and swimmeret beating. The simultaneity of the onset of the two motor systems in this situation is demonstrated to be the result of a startle response initiated when the belt begins to move. This reaction consists of a non-specific motor activity involving several antagonist postural and dynamic muscles. Abdominal extension and vigorous swimmeret beating are the main featurs of this reaction. The main characteristics of the swimmeret beating as defined by Davis (1969) has been observed here in sequences without walking. However during long walking sequences a very different swimmeret beating pattern occurs. It is suggested that this slow swimmeret beating is completely subordinate to the walking rhythm during sequences of absolute coordination. In more rapid swimmeret beating a relative coordination with leg stepping is very common. The functional meaning of this linkage between legs and swimmerets is discussed.     

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).     

The effect of amputation and leg restraint on the free walking coordination of the stick insectCarausius morosus

Summary The stepping patterns of intact, amputated and leg restrained first instar stick insects were examined by analysing video tape records of their free walking behaviour. Amputation produced changes in the relative timing of protraction movements both along and across the body axis. Restraint of individual front or rear legs produced walking behaviour similar to that of the amputee animal but restraint of middle legs caused a breakdown in the coordination of front and rear legs. The changes in behaviour produced by leg autotomy and restraint were used to test certain assumptions of a model for generating the step pattern of these insects and to investigate how the tonic influence of proprioceptive input might be incorporated into the model.I would like to thank Professor P.N.R. Usherwood and Drs. M.D. Burns and W.J.P. Barnes for their comments and ideas on this work. A special acknowledgement goes to Dr. F. Delcomyn whose Fortran step analysis programs assisted greatly in the data reduction. I wish to thank S.R.C. for a returning scientist award and the support and equipment provided by grant B/SR/9774 to Professor Usherwood. A preliminary survey of some of the amputees was carried out at the Biology Department, Case Western Reserve University and I would like to acknowledge the support provided by a P.H.S. grant NB-06054 to Professor R.K. Josephson.     

Sex difference in the pattern of lower limb movement during treadmill walking

To evaluate the characteristics of stereo-typed movement of the lower limb during treadmill walking, the step length and duration of 200 steps were monitored consecutively and calculated by means of a computerized system, consisting of a position sensor, shoes with foot switches and a minicomputer. Eleven male and 10 female subjects walked at various constant speeds ranging from 60-130 m.min-1. Mean, standard deviation (SD) and coefficient of variation (CV) of the time-distance component at each speed were utilized for the assessment of stereotyped movement. When compared with males, females had a tendency to increase their speed by increasing their cadence. The difference of the walking pattern was specifically related to their height. The SD and CV of the time-distance component at a given speed were significantly greater in females than in males. Regression analyses revealed that in the relationship between the walking speeds and the SDs or CVs of the time-distance component, the significant quadratic equations could be fitted. The speed, at which the SD of step length was minimum, was estimated to be about 90 m.min-1 in both males and females. This was regarded as the free walking speed or as the walking speed resulting from a mechanically efficient step length which suited the subject's body size.     

Comparison of forces developed by the leg of the rock lobster when walking free or on a treadmill

Summary In the free walking rock lobster the forces developed by legs 4 and 5 were investigated during the power stroke. Two orthogonal force components lying in the horizontal plane were measured. Based on these results the diffent tasks of the two legs during walking are discussed. The forces developed by leg 4 were compared when the animal walked freely and on a treadmill. In these two situations the results differ qualitatively as in driven walking the forces are nearly identical in a long series of consecutive steps whereas in free walking the forces can vary greatly from step to step. However, similar mean values of force were measured with those on the treadmill being somewhat higher. This shows that, although the treadmill is driven by a motor, the animal does perform active walking movements. In the treadmill situation the forces increase as the speed of treadmill motor is decreased.Supported by DAAD and DFG (Cr 58) for H. Cruse and by ATP (80 119.112) INSERM for F. Clarac     

Walking speed changes in response to novel user-driven treadmill control

Implementing user-driven treadmill control in gait training programs for rehabilitation may be an effective means of enhancing motor learning and improving functional performance. This study aimed to determine the effect of a user-driven treadmill control scheme on walking speeds, anterior ground reaction forces (AGRF), and trailing limb angles (TLA) of healthy adults. Twenty-three participants completed a 10-m overground walking task to measure their overground self-selected (SS) walking speeds. Then, they walked at their SS and fastest comfortable walking speeds on an instrumented split-belt treadmill in its fixed speed and user-driven control modes. The user-driven treadmill controller combined inertial-force, gait parameter, and position based control to adjust the treadmill belt speed in real time. Walking speeds, peak AGRF, and TLA were compared among test conditions using paired t-tests (α = 0.05). Participants chose significantly faster SS and fast walking speeds in the user-driven mode than the fixed speed mode (p > 0.05). There was no significant difference between the overground SS walking speed and the SS speed from the user-driven trials (p < 0.05). Changes in AGRF and TLA were caused primarily by changes in walking speed, not the treadmill controller. Our findings show the user-driven treadmill controller allowed participants to select walking speeds faster than their chosen speeds on the fixed speed treadmill and similar to their overground speeds. Since user-driven treadmill walking increases cognitive activity and natural mobility, these results suggest user-driven treadmill control would be a beneficial addition to current gait training programs for rehabilitation.     

Basic processes of locomotor coordination in the rock lobster

Rock lobsters are able to perform long and stereotyped stepping sequences above a motor driven treadmill. Forward walking samples are estimated by mean of statistical methods to draw out the basic rules involved in the locomotor behaviour (Fig. 1).

- The spatial and temporal parameters defined in a single propulsive leg are either invariable in respect to the imposed speed, as the mean step length (L), the return stroke duration (Tr) and the pause times (T's, T'r), or speed dependent as the power stroke duration (Ts) and the whole period (Figs. 2 and 3).

- The interleg phase coupling is strong and stable in the ipsilateral rear pairs (4–5), these legs acting most of the time in absolute coordination (1:1) or in harmonic ratio (2:1). In the contralateral pairs (R4-L4, R5-L5) the legs roughly operate in antiphase, but the relationship appears much weaker and variable, with frequent episodes of relative coordination (Fig. 4).

- The time intervals between the ground contact of any leg and the swing initiation in the nearest ones appear somewhat constant and could be closely related to the mechanism of stepping synchronization. The “5 on - 4 off” delay, very stable and always positive, suggests that the rear legs could exert a predominant influence upon the rhythmical movements of the next anterior ipsilateral appendages (Fig. 5).

- To test the contralateral relationships, the treadmill belts can be decoupled in order to impose different walking speeds on each side. Such a conflicting stimulus reveals that:

1. The relative hierarchy always observed between the ipsilateral legs can be artificially created between the two sides (Fig. 6).
2. The driving influence of a given leg is closely linked to the intensity of EMG's discharges in its power stroke muscles.
3. The contralateral appendages are able to walk in absolute coordination despite a large speed difference between the two sides (up to 4 cm/s). Under such a constraint, the walking legs alter its invariable parameters (L and Tr) to reach a common step period and steadily maintain the alternating pattern (Figs. 6 and 7).

     

The Combined Effects of Body Weight Support and Gait Speed on Gait Related Muscle Activity: A Comparison between Walking in the Lokomat Exoskeleton and Regular Treadmill Walking

Background

For the development of specialized training protocols for robot assisted gait training, it is important to understand how the use of exoskeletons alters locomotor task demands, and how the nature and magnitude of these changes depend on training parameters. Therefore, the present study assessed the combined effects of gait speed and body weight support (BWS) on muscle activity, and compared these between treadmill walking and walking in the Lokomat exoskeleton.

Methods

Ten healthy participants walked on a treadmill and in the Lokomat, with varying levels of BWS (0% and 50% of the participants’ body weight) and gait speed (0.8, 1.8, and 2.8 km/h), while temporal step characteristics and muscle activity from Erector Spinae, Gluteus Medius, Vastus Lateralis, Biceps Femoris, Gastrocnemius Medialis, and Tibialis Anterior muscles were recorded.

Results

The temporal structure of the stepping pattern was altered when participants walked in the Lokomat or when BWS was provided (i.e. the relative duration of the double support phase was reduced, and the single support phase prolonged), but these differences normalized as gait speed increased. Alternations in muscle activity were characterized by complex interactions between walking conditions and training parameters: Differences between treadmill walking and walking in the exoskeleton were most prominent at low gait speeds, and speed effects were attenuated when BWS was provided.

Conclusion

Walking in the Lokomat exoskeleton without movement guidance alters the temporal step regulation and the neuromuscular control of walking, although the nature and magnitude of these effects depend on complex interactions with gait speed and BWS. If normative neuromuscular control of gait is targeted during training, it is recommended that very low speeds and high levels of BWS should be avoided when possible.     

Coupled oscillators utilised as gait rhythm generators of a two-legged walking machine

The gait of current two-legged walking machines differs from that of humans, although the kinematic structures of these machines' legs frequently imitate human limbs. This paper presents a method of generating the trajectories of hip and knee joint angles resulting in a gait pattern similar to that of a human. For this purpose the solutions of coupled van der Pol oscillator equations are utilised. There is much evidence that these equations can be treated as a good model of the central pattern generator generating functional (also locomotional) rhythms in living creatures. The oscillator equations are solved by numerical integration. The method of changing the type of gait by changing appropriate parameter values in the oscillator equations is presented (change of velocity and trajectory of leg-ends). The results obtained enable enhanced control of twolegged walking systems by including gait pattern generators which will assume a similar role to that of biological generators.     

Responses of the lower limb to load carrying in walking man

Muscle activity patterns of several lower limb muscles were examined in the left leg of normal human subjects walking at comfortable speed on a treadmill. In addition knee angular changes and the durations of the swing and stance phases of the step cycle were recorded. Data were collected during a period of normal control walking and when the subject carried a load, either in his right or left hand or on his back. Load (up to 20% of body weight) carried in either hand caused minimal changes in the kinematic parameters investigated but evoked significant prolongation of the normal ongoing electromyographic activity in the contralateral Gluteus medius and in the ipsilateral Gastrocnemius, Vastus lateralis and Semimembranosus. Load (up to 50% of body weight) carried on the back significantly shortened the swing phase and prolonged the ongoing electromyographic activity of the Vastus lateralis. These findings would seem to indicate that the activity of the leg musculature during walking is so tightly controlled that deviation from the normal kinematic pattern of the legs is largely prevented even when body posture and balance are disturbed by carrying substantial additional load.     

From swimming to walking: a single basic network for two different behaviors

 In this paper we consider the hypothesis that the spinal locomotor network controlling trunk movements has remained essentially unchanged during the evolutionary transition from aquatic to terrestrial locomotion. The wider repertoire of axial motor patterns expressed by amphibians would then be explained by the influence from separate limb pattern generators, added during this evolution. This study is based on EMG data recorded in vivo from epaxial musculature in the newt Pleurodeles waltl during unrestrained swimming and walking, and on a simplified model of the lamprey spinal pattern generator for swimming. Using computer simulations, we have examined the output generated by the lamprey model network for different input drives. Two distinct inputs were identified which reproduced the main features of the swimming and walking motor patterns in the newt. The swimming pattern is generated when the network receives tonic excitation with local intensity gradients near the neck and girdle regions. To produce the walking pattern, the network must receive (in addition to a tonic excitation at the girdles) a phasic drive which is out of phase in the neck and tail regions in relation to the middle part of the body. To fit the symmetry of the walking pattern, however, the intersegmental connectivity of the network had to be modified by reversing the direction of the crossed inhibitory pathways in the rostral part of the spinal cord. This study suggests that the input drive required for the generation of the distinct walking pattern could, at least partly, be attributed to mechanosensory feedback received by the network directly from the intraspinal stretch-receptor system. Indeed, the input drive required resembles the pattern of activity of stretch receptors sensing the lateral bending of the trunk, as expressed during walking in urodeles. Moreover, our results indicate that a nonuniform distribution of these stretch receptors along the trunk can explain the discontinuities exhibited in the swimming pattern of the newt. Thus, separate limb pattern generators can influence the original network controlling axial movements not only through a direct coupling at the central level but also via a mechanical coupling between trunk and limbs, which in turn influences the sensory signals sent back to the network. Taken together, our findings support the hypothesis of a phylogenetic conservatism of the spinal locomotor networks generating axial motor patterns from agnathans to amphibians. Received: 12 October 2001 / Accepted in revised form: 16 May 2002 Correspondence to: T. Bem (e-mail: tiaza.bem@ibib.waw.pl)     

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.     

Vibration signals from the FT joint can induce phase transitions in both directions in motoneuron pools of the stick insect walking system

The influence of vibratory signals from the femoral chordotonal organ fCO on the activities of muscles and motoneurons in the three main leg joints of the stick insect leg, i.e., the thoraco-coxal (TC) joint, the coxa-trochanteral (CT) joint, and the femur-tibia (FT) joint, was investigated when the animal was in the active behavioral state. Vibration stimuli induced a switch in motor activity (phase transition), for example, in the FT joint motor activity switched from flexor tibiae to extensor tibiae or vice versa. Similarly, fCO vibration induced phase transitions in both directions between the motoneuron pools of the TC joint and the CT joint. There was no correlation between the directions of phase transition in different joints. Vibration stimuli presented during simultaneous fCO elongation terminated the reflex reversal motor pattern in the FT joint prematurely by activating extensor and inactivating flexor tibiae motoneurons. In legs with freely moving tibia, fCO vibration promoted phase transitions in tibial movement. Furthermore, ground vibration promoted stance-swing transitions as long as the leg was not close to its anterior extreme position during stepping. Our results provide evidence that, in the active behavioral state of the stick insect, vibration signals can access the rhythm generating or bistable networks of the three main leg joints and can promote phase transitions in motor activity in both directions. The results substantiate earlier findings on the modular structure of the single-leg walking pattern generator and indicate a new mechanism of how sensory influence can contribute to the synchronization of phase transitions in adjacent leg joints independent of the walking direction.