Forward Leaning Research Articles

Love and the commitment problem in romantic relations and friendship.

On the basis of the proposition that love promotes commitment, the authors predicted that love would motivate approach, have a distinct signal, and correlate with commitment-enhancing processes when relationships are threatened. The authors studied romantic partners and adolescent opposite-sex friends during interactions that elicited love and threatened the bond. As expected, the experience of love correlated with approach-related states (desire, sympathy). Providing evidence for a nonverbal display of love, four affiliation cues (head nods, Duchenne smiles, gesticulation, forward leans) correlated with self-reports and partner estimates of love. Finally, the experience and display of love correlated with commitment-enhancing processes (e.g., constructive conflict resolution, perceived trust) when the relationship was threatened. Discussion focused on love, positive emotion, and relationships. Things base and vile, holding no quantity, Love can transform to form and dignity, Love looks not with the eyes, but with the mind, And therefore is winged Cupid painted blind. —William Shakespeare, A Midsummer Night's Dream In Shakespeare's reflection on love, one finds a poignant truth that resonates with experience: In transforming the mundane into the sublime, love can seem blind, irrational, and disconnected from what seems to be true and real. This observation dovetails with our ensuing theoretical analysis of the momentary experience of love. Yet we also take exception with what the great bard has to say about this emotion. Unlike Shakespeare, we contend that people also see love with their eyes; that love has a physical side that is evident in movements of the face and the body that prompt the mind's more sublime operations. More specifically, we propose that the momentary experience of love helps intimate partners remain committed to one another (e.g., Frank, 1988; Steinberg, 1986). This treatment of love as a commitment device leads to the following hypotheses. In terms of the experience of love, we posited that love would correlate with approach-related states. In terms of the display of love, we expected that the experience of love would be encoded in a distinct

Mechanical load on the low back and shoulders during pushing and pulling of two-wheeled waste containers compared with lifting and carrying of bags and bins

Objective. Compare the mechanical load on the low back and shoulders during pushing and pulling a two-wheeled container with the load during lifting and carrying the same amount of waste. Background. Only little is known about risk factors and mechanical loads during push/pull operations. Design. A complete 2 3 factor push/pull experiment. A two-wheeled container with 25 or 50 kg was pushed in front of and pulled behind the body by seven waste collectors. Further, the same subjects lifted and carried a paper bag and a dustbin both loaded with 7 and 25 kg. Method. All operations were video recorded and the push/pull force was measured by means of a three-dimensional force transducer. Peak Motus and Watbak software were used for digitising and calculation of torque at L4/L5 and the shoulder joints and compression and shear forces at L4/L5. Results. During pushing and pulling the compression at L4/L5 is from 605 to 1445 N. The extension torque at L4/L5 produced by the push/pull force is counteracted by the forward leaning of the upper body. The shear force is below 202 N in all situations. The torque at the shoulders is between 1 and 38 Nm. Conclusion. In the present experiments the torques at the low back and the shoulders are low during pushing and pulling. No relation exists between the size of the external force and the torque at the low back and the shoulder. Relevance Pushing and pulling are common in many workplaces and have often replaced lifting and carrying situations. This has emphasised the need for more knowledge of the internal mechanical load on the body during these activities.

Love and the commitment problem in romantic relations and friendship.

On the basis of the proposition that love promotes commitment, the authors predicted that love would motivate approach, have a distinct signal, and correlate with commitment-enhancing processes when relationships are threatened. The authors studied romantic partners and adolescent opposite-sex friends during interactions that elicited love and threatened the bond. As expected, the experience of love correlated with approach-related states (desire, sympathy). Providing evidence for a nonverbal display of love, four affiliation cues (head nods, Duchenne smiles, gesticulation, forward leans) correlated with self-reports and partner estimates of love. Finally, the experience and display of love correlated with commitment-enhancing processes (e.g., constructive conflict resolution, perceived trust) when the relationship was threatened. Discussion focused on love, positive emotion, and relationships.

Muscle activities used by young and old adults when stepping to regain balance during a forward fall

The current study was undertaken to determine if age-related differences in muscle activities might relate to older adults being significantly less able than young adults to recover balance during a forward fall. Fourteen young and twelve older healthy males were released from forward leans of various magnitudes and asked to regain standing balance by taking a single forward step. Myoelectric signals were recorded from 12 lower extremity muscles and processed to compare the muscle activation patterns of young and older adults. Young adults successfully recovered from significantly larger leans than older adults using a single step (32.2° vs. 23.5°). Muscular latency times, the time between release and activity onset, ranged from 73 to 114 ms with no significant age-related differences in the shortest muscular latency times. The overall response muscular activation patterns were similar for young and older adults. However older adults were slower to deactivate three stance leg muscles and also demonstrated delays in activating the step leg hip flexors and knee extensors prior to and during the swing phase. In the forward fall paradigm studied, age-differences in balance recovery performance do not seem due to slowness in response onset but may relate to differences in muscle activation timing during the stepping movement.

Posture-related changes in heteronymous recurrent inhibition from quadriceps to ankle muscles in humans.

The possibility was investigated that changes in heteronymous recurrent inhibition (RI) from quadriceps (Q) to soleus (Sol) and tibialis anterior (TA) motoneurons (MNs) occur during postural tasks requiring cocontraction of Q with one of these muscles. Stimulation of the femoral nerve (FN), which elicited a Q H-reflex discharge, was used to activate Renshaw cells. The resulting inhibition of TA and Sol MNs was assessed using three test responses: (1) the rectified and averaged ongoing electromyogram (EMG) activity in TA or Sol; (2) the motor-evoked potential (MEP) elicited by cortical stimulation in these muscles; and (3) the Sol H reflex. The characteristics of the depression (appearance and increase with the conditioning reflex discharge, short central delay and long duration) are consistent with a Renshaw origin. In addition, results obtained in control experiments (no change in the EMG suppression after an ischaemic blockade of group-I afferents from the leg, time course of the FN-induced depression of the MEP similar to that of the ongoing EMG) made a significant contribution from other pathways activated by FN stimulation unlikely. Posture-related heteronymous RI from Q was compared in different postural tasks at matched levels of background EMG activity: voluntary co-contraction of Q and of the relevant ankle muscle while sitting (control situation), postural co-contraction of Q and TA (while leaning backwards during stance), or contraction of Sol with (preparation for hopping) and without (standing on tip of toes and leaning forwards during stance) associated contraction of the Q. During stance, heteronymous RI from Q was reduced to TA (but not to Sol) while leaning backwards and to Sol in preparation for hopping, but not in the other situations. Thus, RI from Q to TA or Sol was specifically decreased when a co-contraction of the Q and of the relevant muscle operating at the ankle was required to maintain bipedal stance. It is argued that this control of Renshaw cells is descending in origin and contributes to selection of the appropriate synergism in various postural tasks.

Forward leaning reaching task in sitting (FLRS): a new measure for clinical evaluation of hamstring length in children.

In this study, the rotation of the pelvis was taken into account when assessing the length of hamstrings. A new measure for clinical evaluation was developed to establish reference values of hamstring length in children without movement disabilities for different age groups. Subjects (N = 60) were 3-, 6-, 10- and 14-year-old children (N = 15 for each age group). These values could be helpful in deciding treatment interventions in children with movement disabilities, for example cerebral palsy, when hamstring length is in question. The study was performed with subjects sitting and reaching for a touch control on a wall whilst voluntarily rotating the pelvis forwards. By use of digitized video frames, the spatial angles of the lumbar spine and pelvis, as well as the joint angles of hip and knee, were computed at the initial and end positions of a forward leaning reaching task in sitting (FLRS). The active forward leaning induced a forward rotation of the pelvis, causing stretch on the hamstring muscle with extended knee. The results of spatial and joint angle measurements suggest that the difference of the hip joint angle between initial erect and final forward leaned sitting may be used as reference values for hamstring length. Reference values are based on the mean (+/- SE) of means (mean of 15 children, that is, group and individual means of ten trials). The age group reference values obtained may indirectly give information as to whether the hamstring length of a child with cerebral palsy is within the normative value of age-related control subjects. The new test developed in this study provides a convenient means for measuring hamstring length and could enhance clinical evaluation.

Perceptibility of Body Position in Anteroposterior Direction While Standing with Eyes Closed

The perception of body position in the anteroposterior direction was investigated by evaluating the reproducibility of the position from a quiet standing posture to forward or backward leaning posture with eyes closed. The subjects were 10 healthy male undergraduates, aged 20 to 28 years. The standing position was represented by the pressure center of the foot, which was shown by the relative distance (%) from the heel to the length of the foot. The reference positions of the pressure center of the foot were set at 10% increments from 20 to 80% of the length of the foot. The subjects attempted to reproduce each reference position 10 times, and the absolute and constant errors of the reproduced position were analyzed. The absolute errors at reference positions of 30 to 60% were distinctly larger than those at the other reference positions. This indicated that the perception of standing positions from 30 to 60% was less accurate. The constant errors at the reference positions of 40 to 60% were significantly positive, which meant that the reproduced position was located farther forward than the reference position.

Knee joint forces during downhill walking with hiking poles

The aim of this study was to determine external and internal loads on the knee joint during downhill walking with and without hiking poles. Kinematic, kinetic and electromyographic data were collected from eight males during downhill walking on a ramp declined at 25 o . Planar knee joint moments and forces were calculated using a quasi-static knee model. The results were analysed for an entire pole-cycle as well as differentiated between single and double support phases and between each step of a pole-cycle. Significant differences between downhill walking with and without hiking poles were observed for peak and average magnitudes of ground reaction force, knee joint moment, and tibiofemoral compressive and shear forces (12-25%). Similar reductions were found in patellofemoral compressive force, the quadriceps tendon force and the activity of the vastus lateralis; however, because of a high variability, these differences were not significant. The reductions seen during downhill walking with hiking poles compared with unsupported downhill walking were caused primarily by the forces applied to the hiking poles and by a change in posture to a more forward leaning position of the upper body, with the effect of reducing the knee moment arm.

Impaired modulation of tonic muscle activities and H-reflexes in the soleus muscle during standing in patients with Parkinson's disease

The presence of postural disturbance in patients with Parkinson's disease (PD) was assessed by the displacement of the centre of foot pressure (CFP) and by changes in the amplitude of the soleus H-reflex when patients maintained an upright standing posture, followed by a forward-leaning posture. Thirteen patients and 13 age-matched normal controls (N) were studied. PD patients showed the following differences when compared to normal subjects: (1) the range of displacement of the CFP associated with forward leaning was significantly smaller ( P<0.01); (2) the ratio of the increase in the soleus EMG activity to the CFP displacement (ΔEMG/ΔCFP) was larger ( P<0.01), and the value of the ΔEMG/ΔCFP increased significantly in relation to the scale of clinical severity ( P<0.01); and (3) the ratio of the increase in the amplitude of the soleus H-reflex to the soleus muscle EMG activity (ΔH-reflex/ΔEMG) was significantly lower in PD patients ( P<0.05). The value of the ΔH-reflex/ΔEMG decreased significantly with the scale of clinical severity among the patients ( P<0.05). These results suggest that the modulation of both the tonic stretch reflex and the phasic stretch reflex in the soleus muscle during standing are impaired in PD patients, and these impairments may partly cause their disability in the maintenance of a standing posture. Abnormalities in Ib inhibition and presynaptic inhibition are considered to be possible mechanisms in the disturbed modulation of the tonic stretch reflex and the phasic stretch reflex in PD patients during standing.

Relationships between Running Mechanics and Energy Cost of Running at the End of a Triathlon and a Marathon

The purpose of the present study was to check the increase in energy cost of running at the end of a triathlon and a marathon and to link the decrease in energy cost of running with running kinematic parameters. Seven well-trained triathletes performed 3 experimental trials: a 2 h 15 min triathlon (30 min swimming, 60 min cycling and 45 min treadmill running), a 2 h 15 min marathon where the last 45 min (MR) were run at the same speed as the triathlon run (TR) (i.e. 75% of maximal aerobic speed), and a 45 min isolated run (IR) done at the same speed. Oxygen uptake (VO2), minute ventilation (VE), heart rate (HR), respiratory exchange ratio (RER) and kinematic data were recorded during the 3 exercise runs. The results confirm a higher energy cost during MR compared with TR (+ 3.2%; p <0.05) and IR (+ 11.7%; p <0.01). The triathlon and the marathon were associated with greater weight loss (1.6 +/- 0.02 kg; p <0.01) than the isolated run (0.7 +/- 0.2 kg). After cycling, the mean stride length in TR1 was lower during IR1 and increased at the end of TR. The results show that MR led to decrease in stride length compared with IR. After cycling, the triathletes adopted a more forward leaning posture and the trunk gradient was less marked during the marathon. Moreover, the extension of the knee at foot-strike and the maximal knee angle in non-support phase both increased during MR compared with TR and IR. However, it appears that no single kinematic variable can fully explain the decrease in running efficiency: it seems that running economy during a triathlon and a marathon are linked to global alterations of many different parameters.

Human stance stability improves with the repetition of the task: effect of foot position and visual condition

The effects of repetition of quiet stance trials on body sway, recorded through a stabilometric platform, were studied in 12 normal subjects. With feet together, both with eyes open (EO) and closed (EC), a progressive shift forward of the centre of foot pressure (CFP) occurred with repetition. In addition, with EC, but not with EO, a significant progressive reduction in sway area (SA) and sway path (SP) occurred. With feet 10 cm apart, initial SA and SP values were significantly smaller than with feet together, regardless of the visual condition, but repetition of trials induced no significant effects on either position of CFP or body sway under either visual condition. Results indicate the occurrence of a learning phenomenon in this simple postural task, whereby the body shifts towards a `safer' position with a minimum energy expenditure due to reduced corrections of sway. Forward leaning and decrease in sway are two independently-occurring processes, each possibly due to a better central integration of proprioceptive input with repetition of trials.

Physiologic Response to Upright and Forward Leaning Leg Cycle Ergometry in Subjects with Chronic Obstructive Pulmonary Disease: A Preliminary Study

Cycle ergometry is commonly used in pulmonary rehabilitation programs for cardiorespiratory fitness training. Patient position during cycling exercise is generally not standardized, but could affect exercise response. The purpose of this study was to assess physiologic responses in patients with chronic obstructive pulmonary disease (COPD) during upright and forward leaning cycling exercise. Seven females and three males diagnosed with COPD volunteered to participate in this study. Patients performed a submaximal cycling exercise protocol. The patients were positioned with the trunk upright or inclined 45° forward during the submaximal cycling exercise protocol. The patient returned to the laboratory within 2-4 days and repeated the same submaximal exercise protocol as the first testing day, but seated in the other position. The order of cycling position was determined randomly with a card draw for the first subject and alternated thereafter. Physiologic parameters measured included heart rate (HR), minute ventilation (VE), tidal volume (VT), respiratory rate (RR), oxygen consumption (VO2), and the ventilatory equivalent for oxygen (VE/VO2). Rating of perceived exertion (RPE) was also recorded during each minute of the submaximal exercise protocol. Data collected during the last minute of the steady state exercise was averaged and analyzed for between trial differences using a paired t-test. The RPE scores during the final minute of steady state exercise were analyzed using a Wilcoxon Signed RankTest. No significant differences were found between upright and forward inclined submaximal cycling for any of the parameters analyzed.

Effect of forward lean on postural ankle dynamics.

Previous studies investigating postural control using platform perturbations demonstrated that forward leaning occurs under certain experimental conditions. This study examined a potential benefit of forward leaning, investigating the hypothesis that forward lean acts to increase the effective stiffness of the postural ankle dynamics. A systems modeling approach was used to evaluate the effect of forward lean (4 degrees ankle flexion beyond normal stance) on dynamic postural responses to continuous random antero-posterior platform acceleration in four healthy young adults. Motion was limited to the ankle joint using a restraint device and responses were characterized in terms of center-of-pressure displacement. Also, EMG and kinematic data were used to partition measured ankle torque into impedance and activation (postural "reflex") components. The results failed to show a consistent effect, due to lean, on the ankle dynamics. A significant increase in phasic ankle torque due to increased muscle impedance during forward lean was counterbalanced by a comparable decrease in net "reflex" ankle torque. The change in "reflex" torque was apparently due to decreased phasic dorsiflexor activity in forward lean, since phasic plantarflexor activity did not change significantly. Functionally, the results suggest that forward lean occurs for reasons other than stiffening of the overall postural ankle dynamics.

Development of sitting and reaching in 5- to 6-month-old infants

Three studies are reported, investigating changes in body engagement by 5- to 6-month-old infants as they reach for objects in the environment. Infants are distinguished and compared based on their relative ability to maintain a sitting posture without any external body support. The first study demonstrates that manual reaching by sitter infants is coordinated with forward leaning of the trunk, whereas reaching by nonsitters is not. The second study demonstrates that nonsitter infants provided with hip support also show signs of a coordination between reaching of the hand and forward leaning of the trunk. The third study compares nonsitter, nearsitter, and sitter infants as they reach for multiple objects spread across their prehensile space. Results demonstrate expansion in the mapping of infants' prehensile space and hand use as a function of self-sitting ability. The reported results are discussed as expressions of the interaction between the development of postural, perceptual, and action systems in infancy.

Functional base of support decreases with age.

Poor balance in older persons increases the risk of injurious falls during daily activities. Functional base of support (FBOS), the anterior-posterior proportion of foot length used in maximal sustained forward and backward leaning, tests controlled center of mass movement, a component of balance required in daily activities. The purpose of this study was to examine the relationship between FBOS and age and establish the reliability of this measure. Subjects were 113 community-dwelling men and women, ages 20 to 91. FBOS, measured on a force platform, is the difference between mean center of pressure location during sustained forward and backward leaning, divided by foot length. Forward lean (FL), backward lean (BL), and average sway distance during normal standing (STAND SWAY) and while leaning (FBOS SWAY) were also measured. Mean FBOS was .60 +/- .07 in subjects under age 60, and .42 +/- .12 in subjects 60 and older. FBOS remained constant in younger subjects; beyond age 60, FBOS declined about 16% per decade and was more variable. FL and BL also declined with age, remaining 66% and 34% of FBOS, respectively. STAND SWAY and FBOS SWAY were significantly correlated with each other, but not with FBOS. FBOS is a reliable measure and is decreased on average in older persons. This decrease is not related to increased sway while standing or leaning. FBOS is a simple force platform test that has potential as a measure of change in this dimension of balance and as a predictor of falls risk in older persons.

The limits of equilibrium in young and elderly normal subjects and in parkinsonians

Body sway was studied at various body inclinations, voluntarily maintained for about 1 min, in young and elderly normals and in idiopathic parkinsonians. They stood on a dynamometric platform, whose output gave the instantaneous centre of foot pressure (CFP), its mean value and body sway area, with eyes open (EO) or closed (EC). Subjects held the normal upright stance, or the maximum possible inclined posture (body straight, rotated at the ankle joints) in forward or backward direction, or intermediate postures. EMG was recorded from tibialis anterior (TA), soleus (Sol), extensor digitorum brevis (EDB) and flexor digitorum brevis (FDB). The cross-correlation function between the profile of the EMG envelope and the profile of the shift of CFP along the sagittal plane was calculated. In young subjects standing with EO, the maximum extent of antero-posterior (A-P) displacement of CFP was about 60% of foot length. EC reduced this value to about 50%. In the elderly normals, the maximum A-P displacement was about 40% (EO) and 30% (EC). In both groups, sway area was minimal during normal stance with EO and increased progressively when the subjects leant forward or backward. With EC, sway area further increased during normal stance and the rate of increase in relation to inclination augmented markedly. Sol was tonically active during normal stance. Forward leaning increased Sol EMG and induced activity in FDB. TA and EDB were active during backward leaning. The peak of the cross-correlation function between Sol EMG and instantaneous CFP was higher during normal stance than forward inclination, while the reverse was true for FDB. This suggests a role of FDB in the fine-tuning of postural adjustment during forward leaning, and a weight-supporting role of Sol. During backward inclination, TA but not EDB was cross-correlated with CFP. In the parkinsonians, maximum A-P displacement of CFP was just about 30% of foot length (EO; about 20% with EC); its extent was inversely correlated with the severity of the disease. The relationship between sway area and A-P displacement was similar to the elderly, both with EO and EC, within the common range of inclination. In the patients affected by the long-term syndrome, A-P displacement was further reduced while sway area increase at the critical postures was often absent. In all patients, the relationship between muscle activity and body inclination was comparable to normal. The findings challenge the notion that the larger the sway the higher the risk of falling, and suggest that large areas of sway, whilst holding critical postures, are the expression of a deliberate action aimed at reaching further displacement, rather than a sign of instability. In parkinsonians, the limiting factor in body leaning need not be traced to a defective stabilizing feedback mechanism, or to a disordered pattern of muscle activation. Rather, the organization of the motor plan to achieve extreme inclinations seems to be impaired.

Effects of seated posture on erector spinae EMG activity during whole body vibration.

The purpose of this study was to evaluate the electromyographic (EMG) response of the erector spinae to whole body vibration in three different unsupported seated postures: neutral upright, forward lean, and posterior lean. Subjects were 11 healthy college-age men. EMG was collected using bipolar surface electrodes placed bilaterally over the erector spinae at the L4 level. A modified chair with attached accelerometer was affixed to an induction type vibrator. Subjects were vibrated vertically at 4.5 Hz and 6.21 m.s-2 RMS. Data were collected in each of the three postures for 30 s pre- and post-vibration and for 2 min during vibration. Mean EMG values were determined for each sampling period and compared using ANOVA. The mean value for anterior lean was significantly larger (p < 0.05) than that for posterior lean and neutral. EMG data analysed by triggered averaging showed a phase-dependent response to the vibratory cycle for the forward leaning and neutral upright postures. The results of this study indicate that the magnitude of the vibration synchronous response of the erector spinae musculature is dependent upon body posture. This response may be an important factor in the onset of muscular fatigue and the increased incidence of back disorders among individuals exposed to whole body vibration.

Perceiving the affordance of contact in four- and five-month-old infants.

The focus of this study was on the ability of infants to perceive whether an object is positioned at a distance that would make contact possible. As a toy was presented, sometimes within and sometimes beyond reach, the initiation of reaching and leaning forward was scored. Infants were divided into leaning and nonleaning groups. Both leaning and nonleaning 5-month-olds changed their behavior dramatically when the object was placed beyond, as opposed to within, reach. The nonleaners showed a decline in reaching when this boundary for contact was crossed. The "leaners" did not; rather, they began to lean forward. These results suggest that 5-month-olds use information for the affordance of contact. 4-month-olds provided less evidence that arm length regulates reaching. 5-month-old infants acted as if they not only had some sensitivity to the absolute distance of an object but also to the effect that leaning forward has on their ability to make contact with a distant object.

Twisting mobility of the human back in flexed postures.

The twisting mobility of the back was measured using an electromagnetic measuring device, the 3SPACE Isotrak, in ten healthy subjects in five postures: standing upright, in two forward-leaning positions, and two seated positions. In the forward-leaning positions the subjects flexed with mean values of 28 degrees and 53 degrees and had no difference in their active twisting compared with that experienced in the upright position. The two seated positions induced mean flexion values of 32 degrees and 44 degrees and were associated with statistically significant increases in active twisting compared with the upright position of 38% and 46%, respectively, at the level of P < 0.0001. These increases suggest that the wedge morphology of the zygapophysial joints permits greater twisting when the intervertebral joints flexed, but postural muscle action in forward leaning restricts active twisting. This study suggests a mechanism for increased vulnerability of the posterior anulus to injury when twisting is combined with flexion.

A motor programme for the initiation of forward‐oriented movements in humans.

1. The EMG sequence activated before the initiation of a number of fast forward-oriented voluntary movements was analysed quantitatively in normal subjects. 2. The sequence consisted of an initial inhibitory component directed to the soleus motor nucleus, followed by a second excitatory one directed to the tibialis anterior (TA). 3. The spectrum of functional utilization included motor tasks in which the prime movers are leg and thigh muscles (initiation of gait, rising on tip-toes), thigh and trunk muscles (fast-forward bending of the trunk, standing up) and upper-limb muscles (forward throw or catch). 4. In a same motor task and across the different motor tasks, performed at various speeds, the latency of soleus inhibition and TA activation with respect to the onset of movement co-varied according to a linear function, indicating a close temporal correlation between the two components. 5. In all the movements investigated, the earliest mechanical effect was a backward displacement of the centre of foot pressure in the sagittal plane. 6. Soleus inhibition alone and TA burst alone were each able to produce a backward displacement of the centre of foot pressure, but the effect was significantly slower after soleus inhibition. 7. The spatio-temporal parameters of the sequence were modulated according to the pre-existing postural conditions. For the gait initiation protocol, increasing initial forward leaning led to a decrease in the amplitude of soleus inhibition and the TA burst, and to a change in their relative time delays. Modulation was different on the two sides. We could define a postural boundary as the degree of forward leaning beyond which the full sequence is no longer called into action. 8. The spatio-temporal parameters of the sequence were pre-set according to the requirements of the forthcoming movement. In the gait initiation protocol, the amplitude and synchronization of the TA burst were directly correlated with velocity of movement, while the relative delay between soleus inhibition and TA activation was inversely correlated. Modulation on the two sides differed. We could define a velocity boundary as the velocity of movement below which the full sequence is no longer called into action. 9. We suggest that the EMG sequence described can be considered a motor programme that, through direct action on the position of the centre of foot pressure (the variable primarily controlled), will precisely adjust the configuration of forces external to the body, allowing the contraction of the prime mover(s) to interact appropriately with them for the production of a specific, forward-oriented movement.