Hogene Kim

Frontal plane hip and ankle sensorimotor function, not age, predicts unipedal stance time

Introduction: Changes occur in muscles and nerves with aging. In this study we explore the relationship between unipedal stance time (UST) and frontal plane hip and ankle sensorimotor function in subjects with diabetic neuropathy. Methods: UST, quantitative measures of frontal plane ankle proprioceptive thresholds, and ankle and hip motor function were tested in 41 subjects with a spectrum of lower limb sensorimotor function ranging from healthy to moderately severe diabetic neuropathy. Results: Frontal plane hip and ankle sensorimotor function demonstrated significant relationships with UST. Multivariate analysis identified only composite hip strength, ankle proprioceptive threshold, and age to be significant predictors of UST (R2 = 0.73), explaining 46%, 24%, and 3% of the variance, respectively. Conclusions: Frontal plane hip strength was the single best predictor of UST and appeared to compensate for less precise ankle proprioceptive thresholds. This finding is clinically relevant given the possibility of strengthening the hip, even in patients with significant peripheral neuropathy. Muscle Nerve, 2012

Can a clinical test of reaction time predict a functional head-protective response?

PURPOSE Reaction time is commonly prolonged after a sport-related concussion. Besides being a marker for injury, a rapid reaction time is necessary for protective maneuvers that can reduce the frequency and severity of additional head impacts. The purpose of this study was to determine whether a clinical test of simple visuomotor reaction time predicted the time taken to raise the hands to protect the head from a rapidly approaching ball. METHODS Twenty-six healthy adult participants recruited from campus and community recreation and exercise facilities completed two experimental protocols during a single session: a manual visuomotor simple reaction time test (RT(clin)) and a sport-related head-protective response (RT(sprt)). RT(clin) measured the time required to catch a thin vertically oriented device on its release by the tester and was calculated from the distance the device fell before being arrested. RT(sprt) measured the time required to raise the hands from waist level to block a foam tennis ball fired toward the subjects face from an air cannon and was determined using an optoelectronic camera system. A correlation coefficient was calculated between RT(clin) and RT(sprt), with linear regression used to assess for effect modification by other covariates. RESULTS A strong positive correlation was found between RT(clin) and RT(sprt) (r = 0.725, P < 0.001) independent of age, gender, height, or weight. CONCLUSIONS RT(clin) is predictive of a functional sport-related head-protective response. To our knowledge, this is the first demonstration of a clinical test predicting the ability to protect the head in a simulated sport environment. This correlation with a functional head-protective response is a relevant consideration for the potential use of RT(clin) as part of a multifaceted concussion assessment program.

Hip strength: Ankle proprioceptive threshold ratio predicts falls and injury in diabetic neuropathy

Introduction: We determined lower limb neuromuscular capacities associated with falls and fall‐related injuries in older people with declining peripheral nerve function. Methods: Thirty‐two subjects (67.4 ± 13.4 years; 19 with type 2 diabetes), representing a spectrum of peripheral neurologic function, were evaluated with frontal plane proprioceptive thresholds at the ankle, frontal plane motor function at the ankle and hip, and prospective follow‐up for 1 year. Results: Falls and fall‐related injuries were reported by 20 (62.5%) and 14 (43.8%) subjects, respectively. The ratio of hip adductor rate of torque development to ankle proprioceptive threshold (HipSTR/AnkPRO) predicted falls (pseudo‐R2 = .726) and injury (pseudo‐R2 = .382). No other variable maintained significance in the presence of HipSTR/AnkPRO. Conclusions: Fall and injury risk in the population studied is related inversely to HipSTR/AnkPRO. Increasing rapidly available hip strength in patients with neuropathic ankle sensory impairment may decrease risk of falls and related injuries. Muscle Nerve 50: 437–442, 2014

Which Lower Limb Frontal Plane Sensory and Motor Functions Predict Gait Speed and Efficiency on Uneven Surfaces in Older Persons With Diabetic Neuropathy

To identify which frontal plane lower limb sensorimotor functions predict gait speed and efficiency (step‐width‐to‐step‐length ratio) on an uneven surface.

Fibular motor nerve conduction studies and ankle sensorimotor capacities.

Introduction: Nerve conduction studies provide information regarding the status of peripheral nerves, but relationships with sensorimotor capacities that influence mobility have not been defined. Methods: A secondary analysis was conducted on data from 41 older subjects (20 women and 21 men, age 69.1 ± 8.3 years), including 25 with diabetic neuropathy of varying severity and 16 without diabetes or neuropathy. Measurements included routine fibular motor nerve conduction studies and laboratory‐based determination of ankle inversion/eversion proprioceptive thresholds and ankle inversion/eversion motor function. Results: Independent of age, fibular amplitude correlated robustly with ankle inversion/eversion proprioceptive thresholds (R2 = 0.591, P < 0.001), moderately with ankle inversion and eversion rates of torque generation (R2 = 0.216; P = 0.004 and R2 = 0.200; P = 0.006, respectively), and more strongly when fibular motor amplitude was normalized for body mass index (R2 = 0.350; P < 0.001 and R2 = 0.275; P = 0.001). Conclusions: Fibular motor amplitude was strongly associated with ankle sensorimotor capacities that influence lateral balance and recovery from perturbations during gait. The results suggest that nerve conduction study measures have potential for an expanded clinical role in evaluating mobility function in the population studied. Muscle Nerve 47: 497–503, 2013

A shoe sole-based apparatus and method for randomly perturbing the stance phase of gait: Test–retest reliability in young adults

Walking on an irregular surface is associated with an elevated risk for a fall at any age. Yet, relatively little is known about how a human responds to an unexpected underfoot perturbation during gait. This is partly due to the difficulty of generating an intermittent but repeatable, unexpected, underfoot perturbation whose size and location are precisely known. So we developed a shoe sole-embedded apparatus for randomly perturbing the stance phase of gait. Medial and lateral flaps were concealed in the soles of pairs of sandals, along with their actuators. Either flap could be deployed within 400ms in the parasagittal plane under a swing foot; this altered the resulting sagittal and frontal plane orientations of the foot during the next stance phase, whereafter the flap was retracted following toe-off for the rest of that gait trial. We tested six healthy young subjects by randomly presenting a single medial or lateral perturbation in 12 of 30 gait trials. Traditional step kinematic measures were used to evaluate the test-retest reliability of the response to the stimulus at two different walking speeds in 60 randomized trials conducted 1 week apart. The method was effective in systematically inducing an alteration in gait, reproducible across visits, as evidenced by acceptable intraclass correlation coefficients for step width, time and length. We conclude that the apparatus and method has potential for measuring the ability of humans to reject one or more unexpected underfoot perturbations during gait.

Complex and Simple Clinical Reaction Times Are Associated with Gait, Balance, and Major Fall Injury in Older Subjects with Diabetic Peripheral Neuropathy

Objective The aim of this work was to identify relationships between complex and simple clinical measures of reaction time (RTclin) and indicators of balance in older subjects with and without diabetic peripheral neuropathy (DPN). Design Prospective cohort design. Complex RTclin accuracy, simple RTclin latency, and their ratio were determined using a novel device in 42 subjects (mean ± SD age, 69.1 ± 8.3 yrs), 26 with DPN and 16 without. Dependent variables included unipedal stance time (UST), step width variability and range on an uneven surface, and major fall-related injury over 12 months. Results In the DPN subjects, the ratio of complex RTclin accuracy to simple RTclin latency was strongly associated with longer UST (R/P = 0.653/0.004), and decreased step width variability and range (R/P = −0.696/0.001 and −0.782/<0.001, respectively) on an uneven surface. Additionally, the 2 DPN subjects sustaining major injuries had lower complex RTclin accuracy:simple RTclin latency than those without. Conclusions The ratio of complex RTclin accuracy:simple RTclin latency is a potent predictor of UST and frontal plane gait variability in response to perturbations and may predict major fall injury in older subjects with DPN. These short latency neurocognitive measures may compensate for lower limb neuromuscular impairments and provide a more comprehensive understanding of balance and fall risk.

Gait Efficiency on an Uneven Surface Is Associated with Falls and Injury in Older Subjects with a Spectrum of Lower Limb Neuromuscular Function: A Prospective Study.

ObjectiveThe objective of this study was to determine which gait measures on smooth and uneven surfaces predict falls and fall-related injuries in older subjects with diabetic peripheral neuropathy. DesignTwenty-seven subjects (12 women) with a spectrum of peripheral nerve function ranging from normal to moderately severe diabetic peripheral neuropathy walked on smooth and uneven surfaces, with gait parameters determined by optoelectronic kinematic techniques. Falls and injuries were then determined prospectively over the following year. ResultsSeventeen subjects (62.9%) fell and 12 (44.4%) sustained a fall-related injury. As compared with nonfallers, the subject group reporting any fall, as well as the subject group reporting fall-related injury, demonstrated decreased speed, greater step width (SW), shorter step length (SL), and greater SW-to-SL ratio (SW:SL) on both surfaces. Uneven surface SW:SL was the strongest predictor of falls (pseudo-r2 = 0.65; P = 0.012) and remained so with inclusion of other relevant variables into the model. Post hoc analysis comparing injured with noninjured fallers showed no difference in any gait parameter. ConclusionSW:SL on an uneven surface is the strongest predictor of falls and injuries in older subjects with a spectrum of peripheral neurologic function. Given the relationship between SW:SL and efficiency, older neuropathic patients at increased fall risk appear to sacrifice efficiency for stability on uneven surfaces. To Claim CME Credits:Complete the self-assessment activity and evaluation online at http://www.physiatry.org/JournalCME CME Objectives:Uponcompletion of this article, thereader should be able to: (1) Identify health-related outcomes associated with walking for exercise in older populations; (2) Describe the gait pattern, most strongly associated with falls and injuries in the older population with diabetic peripheral neuropathy (DPN); and (3) Incorporate the assessment and treatment of gait abnormalities known to increase fall risk in older patient with DPN into the patients care plan. Level:Advanced Accreditation:The Association of Academic Physiatrists is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians. The Association of Academic Physiatrists designates this activity for a maximum of 1.5 AMA PRA Category 1 Credit(s)™. Physicians should only claim credit commensurate with the extent of their participation in the activity.

Accuracy of Clinical Techniques for Evaluating Lower Limb Sensorimotor Functions Associated With Increased Fall Risk

In prior work, laboratory‐based measures of hip motor function and ankle proprioceptive precision were critical to maintaining unipedal stance and fall/fall‐related injury risk. However, the optimal clinical evaluation techniques for predicting these measures are unknown.

Effect of a Vocal Choice Reaction Time Task on the Kinematics of the First Recovery Step after a Sudden Underfoot Perturbation during Gait

Thirty-two healthy young adults (15 women) were tested for their ability to maintain their comfortable step pattern following an unpredictable underfoot perturbation in the presence and absence of a concurrent vocal choice reaction time task. Custom instrumented shoes were used to randomly deliver an unexpected medial or lateral forefoot perturbation that inverted the mid-foot an average of 10° or everted the midfoot an average of 9° during one stance phase of a gait trial. Medial and lateral perturbations were randomized between left and right feet in 12 of 30 gait trials. The results of the repeated measures analyses of variance show that, compared to the step parameters of unperturbed gait, the administration of the unexpected underfoot perturbation did not significantly lead to alterations in the step length or width of the first recovery step. In addition, the simultaneous administration of a vocal choice reaction time task with the underfoot perturbation did not significantly affect the kinematics of the first recovery step. We conclude that in young healthy adults an unexpected 9-10° underfoot perturbation, with or without a vocal reaction time task, will not affect their recovery step kinematics when walking at a comfortable gait speed.