Biomedical subjects

Judith M Burnfield

Publications and source records attributed to Judith M Burnfield.

10 recordsLinked to original sources

PubMed2006

The neuromuscular demands of toe walking: a forward dynamics simulation analysis.

Toe walking is a gait deviation with multiple etiologies and often associated with premature and prolonged ankle plantar flexor electromyographic activity. The goal of this study was to use a detailed musculoskeletal model and forward dynamical simulations that emulate able-bodied toe and heel-toe walking to understand why, despite an increase in muscle activity in the ankle plantar flexors during toe walking, the internal ankle joint moment decreases relative to heel-toe walking. The simulations were analyzed to assess the force generating capacity of the plantar flexors by examining each muscle's contractile state (i.e., the muscle fiber length, velocity and activation). Consistent with experimental measurements, the simulation data showed that despite a 122% increase in soleus muscle activity and a 76% increase in gastrocnemius activity, the peak internal ankle moment in late stance decreased. The decrease was attributed to non-optimal contractile conditions for the plantar flexors (primarily the force-length relationship) that reduced their ability to generate force. As a result, greater muscle activity is needed during toe walking to produce a given muscle force level. In addition, toe walking requires greater sustained plantar flexor force and moment generation during stance. Thus, even though toe walking requires lower peak plantar flexor forces that might suggest a compensatory advantage for those with plantar flexor weakness, greater neuromuscular demand is placed on those muscles. Therefore, medical decisions concerning whether to reduce equinus should consider not only the impact on the ankle moment, but also the expected change to the plantar flexor's force generating capacity.

Adult↗

PubMed2006

Non-operative management of posterior tibialis tendon dysfunction: design of a randomized clinical trial [NCT00279630].

BACKGROUND: Posterior tibialis tendon dysfunction (PTTD) is a common cause of foot pain and dysfunction in adults. Clinical observations strongly suggest that the condition is progressive. There are currently no controlled studies evaluating the effectiveness of exercise, orthoses, or orthoses and exercise on Stage I or IIA PTTD. Our study will explore the effectiveness of an eccentric versus concentric strengthening intervention to results obtained with the use of orthoses alone. Findings from this study will guide the development of more efficacious PTTD intervention programs and contribute to enhanced function and quality of life in persons with posterior tibialis tendon dysfunction. METHODS/DESIGN: This paper presents the rationale and design for a randomized clinical trial evaluating the effectiveness of a treatment regime for the non-operative management of Stage I or IIA PTTD. DISCUSSION: We have presented the rationale and design for an RCT evaluating the effectiveness of a treatment regimen for the non-operative management of Stage I or IIA PTTD. The results of this trial will be presented as soon as they are available.

Adult↗

PubMed2005

Comparison of utilized coefficient of friction during different walking tasks in persons with and without a disability.

The purpose of this study was to determine if older persons with a disability have greater utilized coefficient of friction requirements than healthy older and younger adults during various walking conditions. Forty-eight community-dwelling adults were divided into five groups based on medical diagnosis and age: CVA (unilateral stroke; mean age 63 years), DM (diabetes mellitus; mean age 70 years), ARTH (lower extremity arthritis; mean age 69 years), SENIOR (healthy; mean age 73 years), and YOUNG (healthy; mean age 29 years). Ground reaction forces (GRF) were recorded as subjects walked across a walkway, ascended and descended stairs, and negotiated a turn. The utilized coefficient of friction (COF(U)) throughout stance was calculated as the ratio of shear to vertical GRFs, and the peak COF(U) resulting from a shear force that would contribute to a forward foot slip was identified. Separate one-way ANOVAs were used to identify differences in peak COF(U) across subject groups for each walking task. The results of this study found that for all conditions evaluated, those with a disability did not demonstrate greater friction requirements then adults without a disability. Friction requirements for the YOUNG group were significantly greater than all disability groups while negotiating a turn, and were greater than the DM group during level walking. These results indicated that the diagnostic groups evaluated in this study are not at any greater risk for slip initiation than the healthy older or younger adults during the tasks evaluated.

Accidental Falls↗

PubMed2005

Effect of foot orthoses on tibialis posterior activation in persons with pes planus.

PURPOSE: To examine the influence of footwear on tibialis posterior (TP) activation in persons with pes planus. METHODS: Six asymptomatic adults with pes planus (arch index of < or =0.16) participated. Subjects performed a resisted foot adduction with plantar flexion exercise (3 sets of 30 repetitions). The exercise was performed barefoot and shod with foot orthoses. The two testing conditions were separated by a week. Magnetic resonance image signal intensity of the tibialis posterior, tibialis anterior, soleus, medial gastrocnemius, and peroneus longus was measured immediately before and after each exercise. Multivariate analyses of variance followed by paired Student's t-test were performed for the signal intensity of each muscle assessed to determine whether TP was selectively activated during the barefoot and shod exercises. RESULTS: When barefoot, five of the six subjects activated other lower-leg muscles in addition to TP. When wearing the foot orthoses and shoes, all five participants activated only TP. Additionally, activation of TP was higher when exercises were performed in shoes with orthoses than when barefoot (P = 0.019). CONCLUSION: Wearing the foot orthoses and shoes improved selective activation of the TP in persons with flat feet. In cases where selective activation of TP is desirable, such as persons with flat feet or TP tendon dysfunction, use of shoes and an arch supporting foot orthoses may enhance selective activation of the muscle.

Adult↗

PubMed2004

The supine hip extensor manual muscle test: a reliability and validity study.

OBJECTIVES: To define the relative hip extensor muscle strengths values identified by the 4 grades obtained with a supine manual muscle test (MMT) and to compare these values with those indicated by the traditional prone test. DESIGN: Comparison of 4 manual supine strength grades with isometric hip extension joint torque; kappa statistic-determined interrater reliability, and analyses of variance identified between grade differences in torque. SETTING: Pathokinesiology laboratory. PARTICIPANTS: Adult volunteers recruited from local community and outpatient clinics. Reliability testing: 16 adults with postpolio (31 limbs). Validity testing (2 groups): 18 subjects without pathology (18 limbs), and 26 people with clinical signs of hip extensor weakness (51 limbs). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Supine hip extensor manual muscle grade and isometric hip extension torque. RESULTS: Reliability testing showed excellent agreement (82%). Subjects with pathology had significant differences in mean torque (P<.01) for the assigned grade 5 (176 Nm), grade 4 (103 Nm), grade 3 (67 Nm), and grade 2 (19 Nm). Healthy adults showed significant differences between grade 5 (212 Nm) and grade 4 (120 Nm) in mean torque (P<.05). CONCLUSIONS: The supine MMT is a reliable and valid method with which to assess hip extension strength.

Activities of Daily Living↗

PubMed2004

Energy expenditure and gait characteristics of a bilateral amputee walking with C-leg prostheses compared with stubby and conventional articulating prostheses.

OBJECTIVE: To compare energy cost and stride characteristics during walking with 3 different types of prostheses in a person with bilateral knee disarticulations. DESIGN: Single-case study. Setting Pathokinesiology laboratory. PARTICIPANT: A subject with bilateral knee disarticulations and bilateral transradial amputations secondary to meningococcemia with purpura fulminans. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Energy cost, stride characteristics, and motion analysis. RESULTS: When wearing the C-Leg prostheses, the subject walked the farthest and fastest, with an overall lower rate of oxygen consumption and oxygen cost compared with walking with either of the other prostheses. Gait analysis while the patient was wearing the C-Leg prostheses revealed premature hip extension, absence of knee flexion during loading response, and a rate of swing in the referent range. CONCLUSIONS: Walking in a C-leg was the most efficient method of ambulation for our subject.

Adult↗

PubMed2004

The influence of walking speed and footwear on plantar pressures in older adults.

OBJECTIVE: To identify the influence of walking velocity and footwear condition on plantar pressure variables in healthy older adults. DESIGN: Single session data collection during varying speed and footwear conditions. BACKGROUND: Elevated plantar pressures are concerning due to the risk of tissue injury, ulceration, and pain. In young adults, increases in plantar pressure have been documented with faster walking speeds and when walking barefoot compared to wearing shoes. These relationships have not been systematically explored in older adults. METHODS: Key plantar pressure factors were recorded as subjects walked barefoot and in comfortable walking shoes across a 10 m walkway at three predetermined velocities (57, 80, 97 m/min). Separate 3x2 analyses of variance with repeated measures identified significant differences in pressure, force, and contact area in eight anatomically defined foot regions across walking speeds and between footwear conditions. RESULTS: Faster walking resulted in higher pressures under all foot regions except for the arch and lateral metatarsal (P</=0.001), due primarily to greater forces under the heel, medial metatarsal and toes (P</=0.001). Compared to wearing shoes, barefoot heel pressure was elevated (P</=0.001) due to reduced heel contact area (P<0.001); pressure under the central metatarsals was higher (P</=0.001) owing to greater central metatarsals force (P<0.001). CONCLUSIONS: Two conditions were associated with higher plantar pressures in the older adults studied: faster speeds and barefoot walking.

Aged↗

PubMed2004

Selective activation of tibialis posterior: evaluation by magnetic resonance imaging.

PURPOSE: To determine which exercise most selectively and effectively activates tibialis posterior. METHODS: Five healthy adults (two men, three women; mean age 31 yr) with an Arch Index (AI) within 1 SD from norm performed three exercises, separated by 1-wk intervals. The exercises were: 1) closed chain resisted foot adduction (foot adduction), 2) unilateral heel raise (heel raise), and 3) open chain resisted foot supination (foot supination). Magnetic resonance transaxial images were obtained immediately before and after exercise using a 1.5-T MRI system. Changes in pre-to postexercise signal intensity were compared across five muscles: tibialis posterior, tibialis anterior, medial gastrocnemius, soleus, and peroneus longus. Postexercise signal intensity was normalized to baseline preexercise signal intensity. RESULTS: Tibialis posterior signal intensity increased after each exercise. The greatest TP increase (50 +/- 6%) occurred after foot adduction, whereas the mean increase in the other muscles was less than 5%. After the heel raise exercise, the signal intensity increase in TP was 27% (+/- 11%), soleus 39% (+/- 8%), peroneus longus 57% (+/- 14%), and medial gastrocnemius 99% (+/- 12%). The signal intensity of tibialis anterior decreased 4% (+/- 2%). After foot supination, the TP signal intensity increased 26% (+/- 7%), whereas the mean change in the other muscles was less than 10%. Multivariate analyses of variance revealed a significant difference in muscle activation between exercises. Posthoc analysis showed greater activation of TP during foot adduction than foot supination (P = 0.021). CONCLUSION: In individuals with a normal AI, TP was activated selectively and most effectively during foot adduction. Knowledge of selective activation of a muscle is necessary to provide an optimal environment for muscle strengthening and/or tendon rehabilitation.

Adult↗

PubMed2003

Toe walking: muscular demands at the ankle and knee.

OBJECTIVE: To compare the relationship between electromyographic activity and internal moment in heel-toe and toe walking. DESIGN: Simultaneous recording of stride characteristics and kinematic, kinetic, and intramuscular electromyographic data; paired t tests identified significant between-condition differences. SETTING: Gait laboratory. PARTICIPANTS: Ten able-bodied subjects. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Kinematic, moment, power, and electromyographic variables (ankle, knee). RESULTS: Compared with heel-toe walking, toe walking showed greater plantarflexion during stance (P<.001), higher plantarflexor moments (peak, mean) during loading response (P<.001) and midstance (P<.001), lower mean plantarflexor moments during terminal stance (P=.002), premature soleus (P=.001) and gastrocnemius (P<.001) activity, and higher levels of mean soleus and gastrocnemius activity during stance. During toe walking, the peak internal knee extensor moment was lower in midstance (P=.002), and power absorption was reduced in loading response; however, vastus intermedius electromyographic activity was not reduced. CONCLUSIONS: During toe walking, terminal stance soleus and gastrocnemius activity was greater, despite a lower mean internal plantarflexor moment. The dichotomy between internal moments and muscle effort (ie, electromyographic activity) was consistent with the reduction in force-generation capacity of the calf muscles when the ankle was in a plantarflexed position.

Adult↗

PubMed2002

Utilized coefficient of friction during walking: static estimates exceed measured values.

This study compared utilized coefficient of friction (COF) measured during nonslip pedestrian gait to estimated utilized COF values calculated using anthropometric (i.e., leg length) and stride characteristic data (i.e., impact angle, step length). Twenty healthy adults walked at slow, medium, and fast speeds with kinematic and kinetic data recorded simultaneously. Estimated and measured impact angle varied with walking speed, with greater angles evident with faster speeds (p < 0.001 and p < 0.05, respectively). The estimated impact angle was greater than the measured impact angle (p < 0.05). Estimated and measured peak utilized COF values varied with walking speed, with higher utilized COF values evident with faster speeds (p < 0.001 and p = 0.001, respectively). Estimated utilized COF values were 86, 118, and 131% greater than measured peak utilized COF values for slow, medium, and fast speeds, respectively (p < 0.001). Higher estimated utilized COF values varied moderately with increased measured peak utilized COF values (r = 0.522; p < 0.001). These data suggest that impact angle and step length alone cannot be used to accurately assess the utilized COF on level walking surfaces.

Accidental Falls↗