Lower Limb Tasks Research Articles

Allocation of attention and dual-task effects on upper and lower limb task performance in healthy young adults.

Many daily activities require separate tasks of the arms and legs to be performed together, as in driving where one foot controls the accelerator, one arm steers, and the other arm and foot shift gears and clutch. Strategies and underlying mechanisms for attention allocation and task prioritization have been explored in standing and walking while performing a manual or cognitive task. These studies reveal a task-related strategy that often, but not always, prioritizes the lower limb task of walking. However, in the absence of locomotion and gait-related postural control, as in sitting, multi-limb dual-task strategies are largely unexplored. Therefore, to characterize dual-task interference of arm and leg tasks during a driving-like activity, seated participants were assessed for the interference effect on hand velocity and movement time of a three-phase reach task and on the error in tracking of a foot-pedal ramp-tracking task. We found that the dual-task cost to reaching shown as decreases in reach performance differed among the three phases, that the cost to foot-pedal tracking also differed by phase, and that the between-task trade-off and prioritization strategy varied between the steep and gradual tracking ramps. Therefore, we propose that attention to concurrent reaching and foot-pedal tracking was flexibly allocated based on phase of the tasks.

Patellofemoral osteoarthritis is prevalent and associated with worse symptoms and function after hamstring tendon autograft ACL reconstruction

ObjectivesTo evaluate the compartmental distribution of knee osteoarthritis (OA) after anterior cruciate ligament reconstruction (ACLR), to determine if patellofemoral or tibiofemoral OA is more strongly associated with knee symptoms and...

The effects of commercially available footwear on foot pain and disability in people with gout: a pilot study

BackgroundThere is limited evidence on non-pharmacological interventions for gout. The aim of the study was to determine whether a footwear intervention can reduce foot pain and musculoskeletal disability in people with gout.MethodsThirty-six people with gout participated in a prospective intervention study over 8 weeks. Participants selected one of 4 pairs of shoes and thereafter wore the shoes for 8 weeks. The primary outcome was foot pain using a 100 mm visual analogue scale. Secondary outcomes related to function and disability were also analysed.ResultsThe Cardio Zip shoe was selected by 58% of participants. Compared with baseline, overall scores for all shoes at 8-weeks demonstrated a decrease in foot pain (p = 0.03), general pain (p = 0.012), Health Assessment Questionnaire (HAQ)-II (p = 0.016) and Leeds Foot Impact Scale (LFIS) impairment subscale (p = 0.03). No significant differences were observed in other patient reported outcomes including patient global assessment, LFIS activity subscale, and Lower Limb Task Questionnaire subscales (all p > 0.10). We observed significant improvements between baseline measurements using the participants’ own shoes and the Cardio Zip for foot pain (p = 0.002), general pain (p = 0.001), HAQ-II (p = 0.002) and LFIS impairment subscale (p = 0.004) after 8 weeks. The other three shoes did not improve pain or disability.ConclusionsFootwear with good cushioning, and motion control may reduce foot pain and disability in people with gout.

The role of primary cilia in cartilage health and disease

The role of primary cilia in cartilage health and disease

Failure of normal development of central drive to ankle dorsiflexors relates to gait deficits in children with cerebral palsy

Neurophysiological markers of the central control of gait in children with cerebral palsy (CP) are used to assess developmental response to therapy. We measured the central common drive to a leg muscle in children with CP. We recorded electromyograms (EMGs) from the tibialis anterior (TA) muscle of 40 children with hemiplegic CP and 42 typically developing age-matched controls during static dorsiflexion of the ankle and during the swing phase of treadmill walking. The common drive to TA motoneurons was identified through time- and frequency-domain cross-correlation methods. In control subjects, the common drive consists of frequencies between 1 and 60 Hz with peaks at beta (15-25 Hz) and gamma (30-45 Hz) frequencies known to be caused by activity within sensorimotor cortex networks: this drive to motoneurons strengthens during childhood. Similar to this drive in control subjects, this drive to the least affected TA in the CP children tended to strengthen with age, although compared with that in the control subjects, it was slightly weaker. For CP subjects of all ages, the most affected TA muscle common drive was markedly reduced compared with that of their least affected muscle as well as that of controls. These differences between the least and most affected TA muscles were unrelated to differences in the magnitude of EMG in the two muscles but positively correlated with ankle dorsiflexion velocity and joint angle during gait. Time- and frequency-domain analysis of ongoing EMG recruited during behaviorally relevant lower limb tasks provides a noninvasive and important measure of the central drive to motoneurons in subjects with CP.

Comparing the Lower Limb Tasks Questionnaire to the Western Ontario and McMaster Universities Osteoarthritis Index: Agreement, Responsiveness, and Convergence With Physical Performance for Knee Osteoarthritis Patients

ObjectiveTo compare the Lower Limb Tasks Questionnaire (LLTQ) with the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) in terms of agreement, responsiveness, and convergence. DesignCross-sectional with an exploratory repeated-measures subsample analysis. SettingCommunity-based seniors’ centers and arthritis clinics. ParticipantsIndividuals with symptomatic knee osteoarthritis (N=76) participated, with a subsample of 18 participants contributing to the pre- and postarthroplasty subanalysis. InterventionNot applicable. Main Outcome MeasuresBland and Altman plots of agreement with 95% limits of agreement, statistical responsiveness, and standardized response mean (SRM) were calculated for LLTQ and WOMAC subscales. Both t tests and Wilcoxon rank-sum tests were used to examine changes in pre- and postarthroplasty self-reported function, 50-ft walk speed, stair ascent/descent speed, and isometric quadriceps strength. ResultsThe agreement (bias) of the LLTQ activities of daily living (ADL) subscale when compared with the WOMAC physical function (PF) subscale was 1%±10% (mean ± SD), and the 95% limits of agreement were –19% to +22%. The statistical responsiveness of the WOMAC-PF and LLTQ ADL was 1.17 and –.63, respectively. The SRMs for these scales were .90 and –.61, respectively. The WOMAC-PF scores showed a notable improvement over the first 6 weeks postarthroplasty, while LLTQ ADL scores were unchanged. The objective measures of function were all significantly worse at 6 weeks. ConclusionsThe LLTQ demonstrated adequate agreement with the WOMAC and acceptable responsiveness for use in place of the WOMAC in nonspecialized clinics. The LLTQ may more accurately represent functional status after total knee arthroplasty, but further study in larger samples is recommended.

Foot pain, impairment, and disability in patients with acute gout flares: A prospective observational study

To evaluate the impact of acute gout on foot pain, impairment, and disability. This prospective observational study recruited 20 patients with acute gout flares. Patients were recruited from emergency departments, hospital wards, and rheumatology outpatient clinics throughout Auckland, New Zealand. Patients were recruited at the time of the flare (baseline visit) and then reassessed at a followup visit once the acute flare had resolved 6-8 weeks after the initial assessment. Swollen and tender joint counts, C-reactive protein levels, and serum urate levels were recorded at both visits. General and foot-specific outcome measures were also recorded at each visit, including pain visual analog scale, Health Assessment Questionnaire II, Lower Limb Tasks Questionnaire, and Leeds Foot Impact Scale. The foot was affected by acute gout in 17 patients (85%). Objective measures of joint inflammation, including swollen and tender joint counts and C-reactive protein levels, significantly improved at the followup visit compared with the baseline visit. At baseline, high levels of foot pain, impairment, and disability were reported. All patient-reported outcome measures of general and foot-specific musculoskeletal function improved at the followup visit compared with the baseline visit. However, pain, impairment, and disability scores did not entirely normalize after resolution of the acute gout flare. Patients with acute gout flares experience severe foot pain, impairment, and disability. These data provide further support for improved management of gout to prevent the consequences of poorly controlled disease.

The effect of lumbar posture on abdominal muscle thickness during an isometric leg task in people with and without non-specific low back pain

This study investigated the effect of lumbar posture on function of transversus abdominis (TrA) and obliquus internus (OI) in people with and without non-specific low back pain (LBP) during a lower limb task. Rehabilitative ultrasound was used to measure thickness change of TrA and OI during a lower limb task that challenged the stability of the spine. Measures were taken in supine in neutral and flexed lumbar postures in 30 patients and 30 healthy subjects. Data were analysed using a two-way (groups, postures) ANOVA. Our results showed that lumbar posture influenced percent thickness change of the TRA muscle but not for OI. An interaction between group and posture was found for TrA thickness change (F1,56 = 6.818, p = 0.012). For this muscle, only healthy participants showed greater thickness change with neutral posture compared to flexed (mean difference = 6.2%; 95% CI: 3.1–9.3%; p < 0.001). Comparisons between groups for both muscles were not significant. Neutral lumbar posture can facilitate an increase in thickness of the TrA muscle while performing a leg task, however this effect was not observed for this muscle in patients with LBP. No significant difference in TrA and OI thickness change between people with and without non-specific LBP was found.

Identifying mobility heterogeneity in very frail older adults. Are frail people all the same?

Frail older adults sustain mobility limitations; however, clinical experience suggests that their mobility characteristics are far from being homogeneous. We conducted a prospective analysis to identify mobility heterogeneity in 1160 very frail older adults and we investigated the associations between mobility limitation profiles and further institutionalization and death. A cluster analysis using 11 self-reported mobility indicators was used to identify mobility profiles (MPs). At baseline, MPs varies from having mild limitations (n=370), moderate limitations (n=470), to severe limitations (n=320). Mild MP did not have mobility disability. Moderate MP had upper limb task limitations and mild lower limb task difficulties. Severe MP portrayed more deficits in lower limbs tasks functions with important mobility disability. After 2 years of follow up, the Severe MP group had a higher risk of mortality and nursing home placement when compared with Mild MP. Higher incidences of hip fracture and hospitalization were associated with the severity of MP. Even among very frail elderly, we identified different levels of mobility, cautioning against to treat them as a homogeneous group. Mobility heterogeneity predicted mortality and nursing home placement in a dose response manner. None of the mobility indicators individually predicted the outcomes as strongly as the profiles. Identification of this mobility heterogeneity may assist on planning of health programs in very frail elderly.

The Lower-Limb Tasks Questionnaire: An Assessment of Validity, Reliability, Responsiveness, and Minimal Important Differences

McNair PJ, Prapavessis H, Collier J, Bassett S, Bryant A, Larmer P. The Lower-Limb Tasks Questionnaire: an assessment of validity, reliability, responsiveness, and minimal important differences. Objectives To develop a questionnaire that focuses only on physical tasks related to lower-limb function and, within that questionnaire, to explore the psychometric properties of a series of questions that are related specifically to activities of daily living (ADLs) and a series of activities more often associated with recreation. Design Inception cohort. Setting Private practice. Participants Data were primarily from patients who had experienced a lower-limb injury that would typically involve rehabilitation up to 6 weeks. Interventions Not applicable. Main Outcome Measures Through 5 studies, the following psychometric qualities were evaluated: content and factor validity, construct and concurrent validity, test-retest reliability (intraclass correlation coefficient [ICC], typical error), responsiveness (effect size, standardized response mean, Guyatt’s responsiveness statistic), and the minimum important difference (distribution, anchor-based approaches). Results Factor analysis supported the theoretical perspective that ADLs and recreational activities can be treated as different domains within the construct of function. Internal consistency was high (Cronbach α: ADLs, .91; recreational activities, .95) and the 2 domains explained a moderate level of the response variance (61%). In the ADL domain, 7 tasks had greater than 80% of participants regarding them as having some importance. For recreational activities, 6 tasks had 79% or more of participants regarding them as having some importance. Both domains were moderately correlated to actual performance of tasks ( r = .62, r = .72), and to other questionnaires used for lower-limb injuries ( r range, .51−.86). The floor and ceiling effects of the domains followed an expected pattern that could be related to the loading forces experienced on the injured limb during activities. The reliability of the 2 domains was high (ICCs >.95), and the Bland-Altman plots showed that the distribution of error across the range of scores was random with low bias scores (<1.0 point). Typical error scores were 2 points for each domain. All measures of responsiveness were high (1.2−6.7). Measures of the minimal important difference varied (3−10 points) according to the methodologic approach used. Conclusions The questionnaire possesses good factor structure and composition, relates well with other measures of function, differentiates patients with regard to certain characteristics or processes known to occur after injury, shows high levels of reliability and responsiveness, and shows evidence of good minimal important difference scores. The findings support the use of the questionnaire in both clinical scenarios and in research.

Strength of Preference in Girls' Lower Limb Tasks

LANGUAGE NOTE | Document text in English; abstract also in Chinese.This study forms part of a larger study that investigated preference in girls' lower limb tasks. This paper reports the expression of girls' (N = 51) strength of preference over time. Strength of preference was analysed using two two-way ANOVA repeated measures designs. The first analysis had Age (4 levels) as the between subjects factor and Session (4 Sessions) as the within subjects factor while the second analysis used Task (6 tasks) as the within subjects factor. The results showed that the stability of girls' lower limb preference varied according to the task that they performed.本篇研究是一個以探討女孩在不同動作任務上其下肢動作偏向的研究之其中一部份。此篇報吿探悉五十一位女孩們在為期一對時間，對不同動作的任務，其下肢体的表現方法是否有一致性，或不一致性的現象。此研究使用雙向ANOVA 二因子重複量數變異數分析設計。第一次分析的兩個因子，分別為以"年齡"為因子(把受試者分為四個不同階段的年齡群)，和以"時段"為因子(單一受試者在四個不同動作測試的時段內)的兩因子重複量數變異數分析。第二次分析使用"任務"為因子(六種不同任務)和"每一受試者其個別下肢動作偏向"為因子，進行分析。研究結果顯示，女孩們對下肢動作的偏向，會依不同的動作任務，而有持續的不同表現方法。

Preference in Girls' Lower Limb Tasks

LANGUAGE NOTE | Document text in English; abstract also in Chinese.The research on laterality indicates that children become increasingly right preferent with age but these relate mainly to data on the upper limbs while lower limb preference is limited. This study investigated the direction of six lower limb preference tasks which included: kicking (stationary and moving ball); pick-up; step-up; balance and hopping. Fifty-one girls in the age group of 3, 4, 5 and 6 years were tested over four sessions at four monthly intervals and classified as right, left or mixed preferent after performing on two successive trials. This study hypothesized that girls would become increasingly right preferent with age and that lower limb preference would differ for each task. Data analysis used a three-way ANOVA repeated measures procedure with Age (4 levels) as the between subjects factor and Session (4 sessions) and Task (6 tasks) as the within subjects factors (N = 51). The ANOVA results showed two task groupings indicating that lower limb preference is task dependent. The authors proposed the interaction of individual differences, changing task and environmental demands influence the expression of lower limb preference.偏向的研究顯示孩童随著年齡的增長會逐漸向右邊偏向，但這些卻主要是針對上肢的研究資料，而對下肢偏向的資料卻有限。本報吿探討六種下肢偏向的動作方向測試，其中包括：踢腿(定點和滾球)、拾起、踩踏、平衡和定點彈跳。五十一位三至六歲的女童參與四次測試，每次測試相隔四個月。在連續兩次嘗試後，將她們分類為向右偏向、向左偏向和綜合偏向。這項研究假設女童隨著年齡的增長，會逐漸有向右邊的偏向，對下肢的偏向會隨著動作的不同而有所改變。報告的資料分析使用了三項ANOVA反復測量規程，以年齡(4個數值)作為物件之間的因素，測試(4次測試)和動作(6個動作)作為物件之內的因素(N = 51)。ANOVA的 結果呈現兩種動作類，顯示對於下肢的偏向是取決於動作的。作者提出看法，認為各個不同孩童的互動、動作和環境的轉換都對下肢偏向起著影響。

Interlimb Influences on Paretic Leg Function in Poststroke Hemiparesis

After stroke, paretic leg motor impairment is typically viewed as a unilateral control deficit. However, much of the neural circuitry controlling normal leg function is organized bilaterally to produce coordinated, task-specific activity in the two legs. Thus, as a result of contralesional neural control processes, paretic leg motor pattern generation may be substantially influenced by the nonparetic leg sensorimotor state during bilateral lower limb tasks. Accordingly, we investigated whether different paretic leg motor patterns are observed during mechanically equivalent bilateral and unilateral tasks and, if so, whether nonparetic leg participation improved or exacerbated paretic leg coordination deficits. A pedaling apparatus that mechanically decoupled the legs was used to present subjects with increasingly complex bi- and unilateral motor tasks: isometric force generation, discrete movement, and pedaling. Bilateral electromyographic and pedal force data were collected from 21 persons with chronic poststroke hemiparesis and 11 similarly aged controls. During isometric force generation and discrete movements, nonparetic leg influences on paretic leg coordination were similar and not markedly different from interlimb influences in controls. In bilateral pedaling, however, interlimb influences differed from controls such that paretic leg coordination deficits were exacerbated. During pedaling movements, the suppression of interlimb influences similar to those observed in isometric and discrete movement may occur in controls but may be disrupted in hemiparesis. We suggest that the coupling of pattern generation between the two legs may result in greater, albeit more impaired, paretic leg motor output during bilateral pedaling than during unilateral pedaling.

Long-term physical exercise and somatosensory event-related potentials

We have compared the occurrence patterns of somatosensory event-related potentials (ERPs) in athletes (soccer players) and non-athletes. ERPs were elicited by two oddball tasks following separate somatosensory stimulation at the median nerve (upper-limb task) and at the tibial nerve (lower-limb task). In the athlete group the N140 amplitudes were larger during upper- and lower-limb tasks and the P300 amplitude and latency were larger and shorter, respectively, during the lower-limb task compared with non-athletes. On the other hand, no significant differences in the P300 amplitude and latency during the upper-limb task were observed between the athlete and non-athlete groups. These results indicate that plastic changes in somatosensory processing might be induced by performing physical exercises that require attention and skilled movements.

Use of a Bicycle Ergometer for Limb Position Sense Testing During a Cyclic Lower Limb Task

Use of a Bicycle Ergometer for Limb Position Sense Testing During a Cyclic Lower Limb Task

The control of foot force during pushing efforts against a moving pedal.

The muscle component of the force applied to a bicycle pedal (foot force) by seated humans provided insight into the organization of the motor system. Healthy adults ( n=11) pedaled a stationary cycle ergometer while attempting to match peak foot force magnitude to visually presented force targets (200, 250,., 650 N). Pedaling cadence was maintained at 60 rpm by a motor. Measurements of the foot force, pedal angle, and crank angle were recorded. The experimental design and data analysis allowed the isolation of the muscle component of the foot force from the contributions due to gravity and inertia. A graphical representation of the muscle component of the foot force (force path) was created for each of several crank angles throughout the extension phase of the pedaling cycle. The force paths showed several highly conserved characteristics across participants and crank angles. Each force path occupied a narrow range in force space despite the ability of the participants to produce force in a wide region of force space. Three control strategies were observed in the geometry of the force paths. Eighty five percent of the force paths were linear for six of the participants, and 79% of the force paths had second-order curvature for the other five participants. The curvature was concave to the posterior for four of the participants and concave to the anterior for one participant. The linear force paths were consistent with the previously reported linear nature of the force paths for pushes against a quasi-static pedal. The observation of simple force path geometry for two tasks with dissimilar dynamic characteristics suggests that this aspect of foot force control may be common to a range of lower limb tasks and may reflect a mechanism by which the nervous system organizes the control of foot force.

Mutability of bifunctional thigh muscle activity in pedaling due to contralateral leg force generation.

Locomotion requires uninterrupted transitions between limb extension and flexion. The role of contralateral sensorimotor signals in executing smooth transitions is little understood even though their participation is crucial to bipedal walking. However, elucidating neural interlimb coordinating mechanisms in human walking is difficult because changes to contralateral sensorimotor activity also affect the ipsilateral mechanics. Pedaling, conversely, is ideal for studying bilateral coordination because ipsilateral mechanics can be independently controlled. In pedaling, the anterior and posterior bifunctional thigh muscles develop needed anterior and posterior crank forces, respectively, to dominate the flexion-to-extension and extension-to-flexion transitions. We hypothesized that contralateral sensorimotor activity substantially contributes to the appropriate activation of these bifunctional muscles during the limb transitions. Bilateral pedal forces and surface electromyograms (EMGs) from four thigh muscles were collected from 15 subjects who pedaled with their right leg against a right-crank servomotor, which emulated the mechanical load experienced in conventional two-legged coupled-crank pedaling. In one pedaling session, the contralateral (left) leg pseudo-pedaled (i.e., EMG activity and pedal forces were pedaling-like, but pedal force was not allowed to affect crank rotation). In other sessions, the mechanically decoupled contralateral leg was first relaxed and then produced rhythmic isometric force trajectories during either leg flexion or one of the two limb transitions of the pedaling leg. With contralateral force production in the extension-to-flexion transition (predominantly by the hamstrings), rectus femoris activity and work output increased in the pedaling leg during its flexion-to-extension transition, which occurs simultaneously with contralateral extension-to-flexion in conventional pedaling. Similarly, with contralateral force production in the other transition (i.e., flexion-to-extension; predominantly by rectus femoris), hamstrings activity and work output increased in the pedaling leg during its extension-to-flexion transition. Therefore rhythmic isometric force generation in the contralateral leg supported the ongoing bifunctional muscle activity and resulting work output in the pedaling leg. The results suggest that neural interlimb coordinating mechanisms fine-tune bifunctional muscle activity in rhythmic lower-limb tasks to ensure limb flexion/extension transitions are executed successfully.

Speed and Efficiency but Not Accuracy or Timing Deficits of Limb Movements in Alcoholic Men and Women

Background: Lesions of the cerebellum, a concomitant of alcoholism, can disrupt quality and regularity of movement. Whether evidence for such dysfunction lingers in patients with uncomplicated alcoholism, which is known to affect cerebellar structural integrity, is controversial. Methods: We used quantitative measures to examine component processes of five classes of movement associated with regional cerebellar function: limb ataxia (alternated finger tapping and variants of the finger-to-nose and heel-to-shin tests), paced tapping, eye-hand coordinated tracing, timed response reflecting preparation and execution time, and postural stability. The subjects examined were 39 abstinent alcoholics (13 men and 26 women) and 21 age-matched controls (9 men and 12 women). For limb ataxia, the dependent measures were the trajectory deviation from the subject's own average movement path and the speed of travel from beginning points to endpoints. Results: Repeated-measures analysis of variance comparing movement speed of finger to nose and heel to shin yielded significant interactions in all conditions (p < 0.007); this indicated that the alcoholics were relatively slower in the upper- than lower-limb tasks. Movements by the alcoholic men were significantly slower but less deviant from an ideal trajectory in all upper-limb conditions than those of the control men (p < 0.002). Although measures of lower-limb movement trajectory did not distinguish the groups, tests of ataxia of stance and gait did. The groups did not differ, however, on tests of timed tapping or sinusoid tracing. Conclusions: Alcohol-related postural instability in abstinent alcoholics is functional evidence supporting the postulated damage to the anterior superior vermis. Altered speed or accuracy trade-offs, with alcoholics moving slower to attain equivalent or even smaller trajectory deviations, are symptomatic of cerebellar hemisphere dysfunction that is characterized by deliberation of otherwise automatic movements.

Speed and Efficiency but Not Accuracy or Timing Deficits of Limb Movements in Alcoholic Men and Women

Lesions of the cerebellum, a concomitant of alcoholism, can disrupt quality and regularity of movement. Whether evidence for such dysfunction lingers in patients with uncomplicated alcoholism, which is known to affect cerebellar structural integrity, is controversial. We used quantitative measures to examine component processes of five classes of movement associated with regional cerebellar function: limb ataxia (alternated finger tapping and variants of the finger-to-nose and heel-to-shin tests), paced tapping, eye-hand coordinated tracing, timed response reflecting preparation and execution time, and postural stability. The subjects examined were 39 abstinent alcoholics (13 men and 26 women) and 21 age-matched controls (9 men and 12 women). For limb ataxia, the dependent measures were the trajectory deviation from the subject's own average movement path and the speed of travel from beginning points to endpoints. Repeated-measures analysis of variance comparing movement speed of finger to nose and heel to shin yielded significant interactions in all conditions (p < 0.007); this indicated that the alcoholics were relatively slower in the upper- than lower-limb tasks. Movements by the alcoholic men were significantly slower but less deviant from an ideal trajectory in all upper-limb conditions than those of the control men (p < 0.002). Although measures of lower-limb movement trajectory did not distinguish the groups, tests of ataxia of stance and gait did. The groups did not differ, however, on tests of timed tapping or sinusoid tracing. Alcohol-related postural instability in abstinent alcoholics is functional evidence supporting the postulated damage to the anterior superior vermis. Altered speed or accuracy trade-offs, with alcoholics moving slower to attain equivalent or even smaller trajectory deviations, are symptomatic of cerebellar hemisphere dysfunction that is characterized by deliberation of otherwise automatic movements.

Phase reversal of biomechanical functions and muscle activity in backward pedaling.

Computer simulations of pedaling have shown that a wide range of pedaling tasks can be performed if each limb has the capability of executing six biomechanical functions, which are arranged into three pairs of alternating antagonistic functions. An Ext/Flex pair accelerates the limb into extension or flexion, a Plant/Dorsi pair accelerates the foot into plantarflexion or dorsiflexion, and an Ant/Post pair accelerates the foot anteriorly or posteriorly relative to the pelvis. Because each biomechanical function (i.e., Ext, Flex, Plant, Dorsi, Ant, or Post) contributes to crank propulsion during a specific region in the cycle, phasing of a muscle is hypothesized to be a consequence of its ability to contribute to one or more of the biomechanical functions. Analysis of electromyogram (EMG) patterns has shown that this biomechanical framework assists in the interpretation of muscle activity in healthy and hemiparetic subjects during forward pedaling. Simulations show that backward pedaling can be produced with a phase shift of 180 degrees in the Ant/Post pair. No phase shifts in the Ext/Flex and Plant/Dorsi pairs are then necessary. To further test whether this simple yet biomechanically viable strategy may be used by the nervous system, EMGs from 7 muscles in 16 subjects were measured during backward as well as forward pedaling. As predicted, phasing in vastus medialis (VM), tibialis anterior (TA), medial gastrocnemius (MG), and soleus (SL) were unaffected by pedaling direction, with VM and SL contributing to Ext, MG to Plant, and TA to Dorsi. In contrast, phasing in biceps femoris (BF) and semimembranosus (SM) were affected by pedaling direction, as predicted, compatible with their contribution to the directionally sensitive Post function. Phasing of rectus femoris (RF) was also affected by pedaling direction; however, its ability to contribute to the directionally sensitive Ant function may only be expressed in forward pedaling. RF also contributed significantly to the directionally insensitive Ext function in both forward and backward pedaling. Other muscles also appear to have contributed to more than one function, which was especially evident in backward pedaling (i.e. , BF, SM, MG, and TA to Flex). We conclude that the phasing of only the Ant and Post biomechanical functions are directionally sensitive. Further, we suggest that task-dependent modulation of the expression of the functions in the motor output provides this biomechanics-based neural control scheme with the capability to execute a variety of lower limb tasks, including walking.