Publications by authors named "James K Richardson"

57 Publications

Characterization and clinical implications of ankle impedance during walking in chronic stroke.

Sci Rep 2021 Aug 18;11(1):16726. Epub 2021 Aug 18.

Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, USA.

Individuals post-stroke experience persisting gait deficits due to altered joint mechanics, known clinically as spasticity, hypertonia, and paresis. In engineering, these concepts are described as stiffness and damping, or collectively as joint mechanical impedance, when considered with limb inertia. Typical clinical assessments of these properties are obtained while the patient is at rest using qualitative measures, and the link between the assessments and functional outcomes and mobility is unclear. In this study we quantify ankle mechanical impedance dynamically during walking in individuals post-stroke and in age-speed matched control subjects, and examine the relationships between mechanical impedance and clinical measures of mobility and impairment. Perturbations were applied to the ankle joint during the stance phase of walking, and least-squares system identification techniques were used to estimate mechanical impedance. Stiffness of the paretic ankle was decreased during mid-stance when compared to the non-paretic side; a change independent of muscle activity. Inter-limb differences in ankle joint damping, but not joint stiffness or passive clinical assessments, strongly predicted walking speed and distance. This work provides the first insights into how stroke alters joint mechanical impedance during walking, as well as how these changes relate to existing outcome measures. Our results inform clinical care, suggesting a focus on correcting stance phase mechanics could potentially improve mobility of chronic stroke survivors.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41598-021-95737-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8373915PMC
August 2021

Chemotherapy-induced peripheral neuropathy increases nontraumatic fracture risk in breast cancer survivors.

JBMR Plus 2021 Aug 10;5(8):e10519. Epub 2021 Jun 10.

Department of Physical Medicine and Rehabilitation Michigan Medicine Ann Arbor Michigan USA.

Chemotherapy is a common treatment for breast cancer (BrCa) and can cause chemotherapy-induced peripheral neuropathy (CIPN). CIPN contributes to falls, and is thus a potential risk factor for nontraumatic fractures (NTFx); yet, the effect of CIPN on NTFx risk has not been examined for BrCa survivors. We therefore investigated the association between CIPN and NTFx in BrCa survivors. Data were extracted from Optum's Deidentified Clinformatics® Data Mart Database years 2010-2015 in this retrospective cohort study. Among women, three groups were derived based on BrCa and CIPN status: BrCa+/CIPN+ (primary group of interest), BrCa+/CIPN- (first comparison group), and BrCa-/CIPN- (second comparison group). After propensity score matching the comparison groups to BrCa+/CIPN+ at a ratio of 1:11 (BrCa:control) for demographics, osteoporosis, glucocorticoid medication, comorbidities, and cancer-related variables for BrCa+/CIPN-, 1-year incidence rate (IR) of NTFx was determined for each group. The incident rate ratio (IRR) determined if the IR for NTFx was different for BrCa+/CIPN+ compared to BrCa+/CIPN- and BrCa-/CIPN-. Cox proportional hazards regression models estimated the hazard ratios (HRs) after adjusting for covariates that were unable to be matched for. The crude IR (95% confidence interval [CI]) of NTFx was 4.54 (2.32-6.77) for BrCa+/CIPN+ ( = 359), 2.53 (2.03-3.04) for BrCa+/CIPN- ( = 3949), and 1.76 (1.35-2.18) for BrCa-/CIPN- ( = 3949). The crude IRR of NTFx was significantly elevated for BrCa+/CIPN+ as compared to BrCa+/CIPN- (IRR = 1.80; 95% CI, 1.06-3.05) and BrCa-/CIPN- (IRR = 2.58; 95% CI, 1.50-4.44). The elevated rate of NTFx for BrCa+/CIPN+ remained unchanged after adjusting for aromatase inhibitors compared to BrCa+/CIPN- (HR = 1.79; 95% CI, 1.06-3.04). Female BrCa survivors have an increased 1-year IR of NTFx after the onset of CIPN, suggesting that CIPN is an additive burden on NTFx risk among BrCa survivors. © 2021 The Authors. published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/jbm4.10519DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8328798PMC
August 2021

Rapid Inhibition Accuracy and Leg Strength Are Required for Community-Dwelling Older People to Recover Balance From Induced Trips and Slips: An Experimental Prospective Study.

J Geriatr Phys Ther 2021 Jul 26. Epub 2021 Jul 26.

Falls, Balance and Injury Research Centre, Neuroscience Research Australia, Sydney, New South Wales, Australia. UNSW Medicine, Sydney, New South Wales, Australia. Department of Human Movement Sciences, Amsterdam Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands. Department of Physical Medicine and Rehabilitation, University of Michigan, Ann Arbor.

Background And Purpose: Falls can result in bone fractures and disability, presenting a serious threat to quality of life and independence in older adults. The majority of falls in community-living older adults occur while walking and are often caused by trips and slips. The study aimed to identify the specific sensorimotor and psychological factors required for older adults to recover balance from trips and slips.

Methods: Forty-one older adults aged 65 to 87 years were assessed on sensorimotor (knee extension strength, proprioception, postural sway, and edge contrast sensitivity), reaction (simple reaction time, stepping, and catching reaction inhibition), and psychological (general anxiety and concern about falling) measures. Using a harness system, participants walked at 90% of their usual pace on a 10-m walkway that could induce trips and slips in concealed and changeable locations. Post-perturbation responses resulting in more than 30% of body weight being recorded by the harness system were defined as falls. Poisson regressions were used to test associations between the sensorimotor, reaction, and psychological measures and number of falls.

Results: Fifty-one falls occurred in 25 of 41 participants. Poisson regression revealed body mass index, lower-limb proprioception, knee extension strength, rapid inhibition accuracy, concern about falling, and anxiety were significantly associated with the rate of falls. Other measures including postural sway were not statistically significant. Using stepwise Poisson regression analyses, normalized knee extension strength (rate ratio [RR]: 0.68, 95% confidence interval [CI]: 0.47-0.98), and rapid inhibition accuracy (RR: 0.64, 95% CI: 0.46-0.87) were independently associated with falls.

Conclusion: Our findings suggest rapid inhibition accuracy and adequate leg strength are required for older adults to recover balance from trips and slips. The mechanisms for balance recovery during daily life activities are likely different from those for static balance, suggesting the need for task-specific assessments and interventions for fall prevention in older adults.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1519/JPT.0000000000000312DOI Listing
July 2021

Short-latency inhibition mitigates the relationship between conscious movement processing and overly cautious gait.

Age Ageing 2021 05;50(3):830-837

School of Sport and Health Sciences, University of Exeter, UK.

Background: Overly cautious gait is common in older adults. This is characterised by excessively slow gait, shortened steps, broadened base of support and increased double limb support. The current study sought to (1) evaluate if overly cautious gait is associated with attempts to consciously process walking movements, and (2) explore whether an individual's ability to rapidly inhibit a dominant motor response serves to mitigate this relationship.

Methods: A total of 50 older adults walked at a self-selected pace on an instrumented walkway containing two raised wooden obstacles (height = 23 cm). Trait conscious movement processing was measured with the Movement-Specific Reinvestment Scale. Short-latency inhibitory function was assessed using a validated electronic go/no-go ruler catch protocol. We used linear regressions to explore the relationship between these variables and gait parameters indicative of overly cautious gait.

Results: When controlling for general cognitive function (MoCA), and functional balance (Berg Balance Scale), the interaction between trait conscious movement processing and short-latency inhibition capacity significantly predicted gait velocity, step length and double limb support. Specifically, older adults with higher trait conscious movement processing and poorer inhibition were more likely to exhibit gait characteristics indicative of cautious gait (i.e. reduced velocity, shorter step lengths and increased double limb support). Neither conscious movement processing nor inhibition independently predicted gait performance.

Conclusion: The combination of excessive movement processing tendencies and poor short-latency inhibitory capacity was associated with dysfunctional or 'overly cautious' gait. It is therefore plausible that improvement in either factor may lead to improved gait and reduced fall risk.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1093/ageing/afaa230DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8099234PMC
May 2021

A clinical method of evaluating simple reaction time and reaction accuracy is sensitive to a single dose of lorazepam.

J Psychopharmacol 2020 08 13;34(8):920-925. Epub 2020 Jun 13.

Department of Mechanical Engineering, University of Michigan, Ann Arbor, USA.

Rationale: Benzodiazepines are useful and commonly prescribed. Unfortunately, they are associated with subtle but functionally significant neurocognitive side effects that increase the risk of motor vehicle accidents and falls.

Objective: The objective of this study was to determine whether clinically feasible measures of simple reaction time and reaction accuracy are sensitive to a single dose of lorazepam.

Methods: Using a randomized, double-blind, crossover design, 26 healthy adults (13 women; age = 26.9 ± 8.2 yr) were given 1.0 mg lorazepam or placebo 90 minutes prior to two data collection sessions. Participants completed simple and reaction accuracy tasks using a standardized "ruler drop" testing paradigm during each session. Outcomes were mean and variability of simple reaction time and reaction accuracy, which evaluates a participant's ability to catch the device solely on the random 50% of trials that lights affixed to it illuminate on release. Reaction accuracy requires a go/no-go decision within 420 ms before the falling device strikes the floor.

Results: As compared with placebo, lorazepam increased simple reaction time variability (range = 43 ± 18 vs. 60 ± 23 ms, respectively; = 0.004 and standard deviation = 14.6 ± 5.7 vs. 19.7 ± 7.3 ms, respectively; = 0.006) and decreased reaction accuracy (90 ± 7% vs. 84 ± 11%, respectively; = 0.010).

Conclusion: Given prior work demonstrating associations between simple reaction time and reaction accuracy and functional outcomes such as self-protection, response to perturbations, and fall risk, these clinically available measures may have a role in identifying subtle, functionally significant cognitive changes related to short-term benzodiazepine use.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1177/0269881120915409DOI Listing
August 2020

Primary cancer location predicts predominant level of brachial plexopathy.

Muscle Nerve 2020 09 24;62(3):386-389. Epub 2020 Jun 24.

Department of Physical Medicine and Rehabilitation, Michigan Medicine, Ann Arbor, Michigan.

Background: Changes in radiation therapy practice and cancer incidence bring into question prior evidence suggesting that radiation therapy predominantly injures the brachial plexus upper trunk, while tumor invasion typically injures the lower trunk.

Methods: We reviewed electrodiagnostic brachial plexopathy reports in cancer survivors for predominant trunk involvement, injury mechanism (tumor invasion vs radiation), and primary cancer location.

Results: Fifty-six cases of cancer-associated brachial plexopathy were identified. There was no relationship between injury mechanism and brachial plexus injury level. However, primary cancer location superior/inferior to the clavicle increased the odds of predominantly upper/lower trunk involvement by a factor of 60.0 (95% confidence interval: 7.9, 1401, respectively).

Conclusions: Cancers superior/inferior to the clavicle increase the likelihood of predominantly upper/lower trunk plexopathy, respectively, regardless plexus injury mechanism. These findings contrast with older work, possibly due to more precise radiation therapy techniques and increased incidence of radiosensitive head and neck cancers.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/mus.26994DOI Listing
September 2020

Neurocognitive and Muscular Capacities Are Associated with Frailty in Adults with Cirrhosis.

Dig Dis Sci 2020 12 25;65(12):3734-3743. Epub 2020 Jan 25.

Department of Internal Medicine, University of Michigan, Ann Arbor, USA.

Background: Frailty is common in cirrhosis and associated with mortality, hospitalization, and reduced quality of life. Interventions aimed at forestalling frailty are limited by a lack of understanding of underlying physiologic deficits.

Aims: This study's aim was to examine contributions of discrete sensorimotor and neurocognitive capacities to conventional frailty measures of unipedal stance time, chair stands, and grip strength.

Methods: This cross-sectional study enrolled 119 outpatients with cirrhosis (50% female, aged 62.9 ± 7.3 years). Capacities included sensory (lower limb sensation and visual contrast), neurocognitive (Number Connection Tests A and B, simple and recognition reaction time), and muscular (hip/core strength determined by lateral plank time (LPT)). Bivariate analyses and linear regression models were performed to identify significant contributors to each frailty measure.

Results: The average performance was 9.8 ± 3.9 chair stands, 12.7 s ±9.9 unipedal stance time, and 60.3 ± 25.6 lb grip strength. In multivariate models, factors explained 40% of variance in unipedal stance and 43% of variance in chair stands. The LPT was most strongly associated with unipedal stance and chair stands. Grip strength was associated with LPT, but did not have physiologic predictors.

Conclusions: Clinically useful measures of frailty in adults with cirrhosis can be explained by disease severity but also deficits in strength and neurocognitive function. Recognition reaction time, a novel measure in cirrhosis, had a significant contribution to frailty. These findings have implications for frailty assessment and suggest that the optimal rehabilitation approach to frailty targets neurocognitive function in addition to strengthening.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s10620-020-06099-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7814530PMC
December 2020

A potential additional diagnostic use for exercising the CMAP.

Muscle Nerve 2020 02 29;61(2):E12. Epub 2019 Nov 29.

Department of Athletic Medicine, Purdue University, Lafayette, Indiana.

View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/mus.26755DOI Listing
February 2020

Electrophysiological Changes After Human Muscle Tear: A Potential Confounder.

Am J Phys Med Rehabil 2020 07;99(7):645-648

From the Department of Physical Medicine and Rehabilitation, University of Michigan, Ann Arbor, Michigan (SLH, HMB, JKR); and Department of Neurology, University of Michigan, Ann Arbor, Michigan (AAL, JWT).

The goal of this prospective electrophysiologic study is to describe the chronological electromyographic findings observed in a human gastrocnemius muscle after a traumatic tear. A 30-yr-old man sustained a tear of the medial gastrocnemius. Needle electromyography was performed serially at 5, 15, and 26 wks after injury, with the contralateral gastrocnemius muscle serving as a control. Audiovisual recordings of the studies were analyzed in a blinded manner. Five weeks after injury, the affected gastrocnemius displayed increased insertional activity on electromyography. By 15-wk postinjury, insertional activity had diminished. However, motor unit action potentials showed chronic neurogenic morphological changes not previously observed. These changes persisted 26 wks after injury. The study findings reveal a chronological trajectory of increased insertional activity followed by reinnervation changes in a human muscle after local trauma, paralleling a course previously observed in a rat model. Electrodiagnosticians unaware of this phenomenon are at risk for making erroneous interpretations when examining patients with a history of muscle trauma.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1097/PHM.0000000000001346DOI Listing
July 2020

Motor amplitudes may predict electromyography-confirmed radiculopathy in patients referred for radiating limb pain.

Muscle Nerve 2019 05 7;59(5):561-566. Epub 2019 Mar 7.

Physical Medicine and Rehabilitation, University of Michigan, Ann Arbor, Michigan, USA.

Introduction: Radiculopathy is diagnosed by needle electromyography, with nerve conduction studies excluding alternative diagnoses.

Methods: In patients referred for electrodiagnostic evaluation of radiating limb pain, we compared ulnar motor amplitudes between those with and without electromyographically confirmed C8 radiculopathy, as well as fibular motor amplitudes between those with and without electromyographically confirmed L5 radiculopathy.

Results: Patients with electromyographically confirmed C8 or L5 radiculopathy demonstrated decreased ulnar or fibular motor amplitudes, respectively, as compared to patients without radiculopathy. Receiver operating characteristic curves demonstrated good diagnostic accuracy, with areas under the curve of 0.85 and 0.82, respectively. Optimal cut-offs for electromyographically confirmed C8 and L5 radiculopathies were 10.2 mV and 3.6 mV, respectively, with associated sensitivities/specificities of 0.86/0.74 and 0.92/0.60.

Discussion: Ulnar and fibular motor amplitudes may have clinical utility in assessing the likelihood of patients demonstrating electromyographically confirmed C8 and L5 radiculopathies with active denervation. The findings may be particularly useful in patients intolerant of needle electromyography. Muscle Nerve 59:561-561, 2019.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/mus.26442DOI Listing
May 2019

Why Do Individuals with Cirrhosis Fall? A Mechanistic Model for Fall Assessment, Treatment, and Research.

Dig Dis Sci 2019 02 16;64(2):316-323. Epub 2018 Oct 16.

Department of Physical Medicine and Rehabilitation, University of Michigan, Ann Arbor, MI, USA.

Falls are prevalent for people with cirrhosis and commonly lead to loss of independence, reduced quality of life, and mortality. Despite a critical need for fall prevention in this population, cirrhosis-specific fall-related mechanisms are not well understood. We posit that most falls in this patient population are due to a coalescence of discrete subclinical impairments that are not typically detected at the point of care. The combined effect of these subtle age- and disease-related neurocognitive and muscular impairments leads to the inability to respond successfully to a postural perturbation within the available 300 to 400 ms. This article provides a conceptual model of physiological resilience to avoid a fall that focuses on attributes that underlie the ability to withstand a postural perturbation and their clinical evaluation. Evidence supporting this model in cirrhosis and other high fall risk conditions will be synthesized and suggestions for fall assessment and treatment will be discussed.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s10620-018-5333-8DOI Listing
February 2019

Value-Added Electrodiagnostics: Targeting Interventions for Fall Risk Reduction.

Phys Med Rehabil Clin N Am 2018 11 7;29(4):645-657. Epub 2018 Sep 7.

Department of Physical Medicine and Rehabilitation, Michigan Medicine, 325 E Eisenhower Parkway Suite 100, Ann Arbor, MI 48108-3364, USA.

Walking confers numerous health benefits, particularly for middle-aged and older patients with diabetes and metabolic syndrome. Nevertheless, it brings a risk of injurious falls, especially among populations with diabetes and metabolic syndrome-related distal neuromuscular decline and frank neuropathy. Those who stand to benefit most from walking are at greatest risk. Development of practical clinical tools to more precisely quantify neuromuscular function and link it to mobility outcomes will help clinicians target interventions toward those at risk for falls. Electrodiagnosis, with inclusion of several newer techniques, serves as a promising tool for objective evaluation of distal neuromuscular function.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.pmr.2018.06.001DOI Listing
November 2018

Imbalanced: The Confusing Circular Nature of Falls Research…and a Possible Antidote.

Am J Phys Med Rehabil 2017 01;96(1):55-59

From the Department of Physical Medicine and Rehabilitation, University of Michigan Health Systems, Ann Arbor, Michigan.

View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1097/PHM.0000000000000591DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5175410PMC
January 2017

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

Am J Phys Med Rehabil 2017 01;96(1):8-16

From the Department of Physical Medicine and Rehabilitation, University of Michigan, Ann Arbor, Michigan.

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.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1097/PHM.0000000000000604DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5161564PMC
January 2017

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

PM R 2016 Apr 25;8(4):331-339. Epub 2015 Sep 25.

Department of Physical Medicine and Rehabilitation, University of Michigan Health System, 325 East Eisenhower Pkwy, Ann Arbor, MI 48108(¶). Electronic address:

Background: 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.

Objective: To evaluate the diagnostic accuracy of common clinical maneuvers in predicting laboratory-based measures of frontal plane hip rate of torque development (Hip(RTD)) and ankle proprioceptive thresholds (AnkPRO) associated with increased fall risk.

Design: Prospective, observational study.

Setting: Biomechanical research laboratory.

Participants: A total of 41 older subjects (aged 69.1 ± 8.3 years), 25 with varying degrees of diabetic distal symmetric polyneuropathy and 16 without.

Assessments: Clinical hip strength was evaluated by manual muscle testing (MMT) and lateral plank time, defined as the number of seconds that the laterally lying subject could lift the hips from the support surface. Foot/ankle evaluation included Achilles reflex and vibratory, proprioceptive, monofilament, and pinprick sensations at the great toe.

Main Outcome Measures: Hip(RTD), abduction and adduction, using a custom whole-body dynamometer. AnkPRO determined with subjects standing using a foot cradle system and a staircase series of 100 frontal plane rotational stimuli.

Results: Pearson correlation coefficients (r) and receiver operator characteristic (ROC) curves revealed that LPT correlated more strongly with Hip(RTD) (r/P = 0.61/<.001 and 0.67/<.001, for abductor/adductor, respectively) than did hip abductor MMT (r/P = 0.31/.044). Subjects with greater vibratory and proprioceptive sensation, and intact Achilles reflexes, monofilament, and pin sensation had more precise AnkPRO. LPT of <12 seconds yielded a sensitivity/specificity of 91%/80% for identifying Hip(RTD) < 0.25 (body size in Newton-meters), and vibratory perception of <8 seconds yielded a sensitivity/specificity of 94%/80% for the identification of AnkPRO >1.0°.

Conclusions: LPT is a more effective measure of Hip(RTD) than MMT. Similarly, clinical vibratory sense and monofilament testing are effective measures of AnkPRO, whereas clinical proprioceptive sense is not.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.pmrj.2015.08.017DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4808474PMC
April 2016

RELIABILITY AND CRITERION VALIDITY OF A NOVEL CLINICAL TEST OF SIMPLE AND COMPLEX REACTION TIME IN ATHLETES.

Percept Mot Skills 2015 Jun;120(3):841-59

4 Department of Mechanical Engineering and Department of Biomedical Engineering University of Michigan, Ann Arbor, Michigan.

Slowed reaction time (RT) represents both a risk factor for and a consequence of sport concussion. The purpose of this study was to determine the reliability and criterion validity of a novel clinical test of simple and complex RT, called RT(clin), in contact sport athletes. Both tasks were adapted from the well-known ruler drop test of RT and involve manually grasping a falling vertical shaft upon its release, with the complex task employing a go/no-go paradigm based on a light cue. In 46 healthy contact sport athletes (24 men; M = 16.3 yr., SD = 5.0; 22 women: M age = 15.0 yr., SD = 4.0) whose sports included soccer, ice hockey, American football, martial arts, wrestling, and lacrosse, the latency and accuracy of simple and complex RT(clin) had acceptable test-retest and inter-rater reliabilities and correlated with a computerized criterion standard, the Axon Computerized Cognitive Assessment Tool. Medium to large effect sizes were found. The novel RT(clin) tests have acceptable reliability and criterion validity for clinical use and hold promise as concussion assessment tools.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.2466/25.15.PMS.120v19x6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4704438PMC
June 2015

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.

Am J Phys Med Rehabil 2016 Feb;95(2):83-90

From the Department of Physical Medicine and Rehabilitation, University of Michigan Health System, Ann Arbor, Michigan (KZ, TKD, JKR); Department of Physiotherapy, University of Applied Sciences of Western Switzerland, Geneva, Switzerland (LA); and Department of Mechanical Engineering, Biomechanics Research Laboratory, University of Michigan, Ann Arbor, Michigan (HK, JAA-M).

Objective: The 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.

Design: Twenty-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.

Results: Seventeen 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-r = 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.

Conclusion: SW: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.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1097/PHM.0000000000000324DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4670600PMC
February 2016

Rectus abdominis denervation after subcostal open laparotomy.

Am J Phys Med Rehabil 2015 May;94(5):e43-4

From the Department of Physical Medicine and Rehabilitation, University of Michigan, Ann Arbor, Michigan.

View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1097/PHM.0000000000000256DOI Listing
May 2015

Effect of neck muscle strength and anticipatory cervical muscle activation on the kinematic response of the head to impulsive loads.

Am J Sports Med 2014 Mar 31;42(3):566-76. Epub 2014 Jan 31.

James T. Eckner, University of Michigan, Department of Physical Medicine & Rehabilitation, 325 E Eisenhower Pkwy, Ann Arbor, MI, 48108, USA.

Background: Greater neck strength and activating the neck muscles to brace for impact are both thought to reduce an athlete's risk of concussion during a collision by attenuating the head's kinematic response after impact. However, the literature reporting the neck's role in controlling postimpact head kinematics is mixed. Furthermore, these relationships have not been examined in the coronal or transverse planes or in pediatric athletes.

Hypotheses: In each anatomic plane, peak linear velocity (ΔV) and peak angular velocity (Δω) of the head are inversely related to maximal isometric cervical muscle strength in the opposing direction (H1). Under impulsive loading, ΔV and Δω will be decreased during anticipatory cervical muscle activation compared with the baseline state (H2).

Study Design: Descriptive laboratory study.

Methods: Maximum isometric neck strength was measured in each anatomic plane in 46 male and female contact sport athletes aged 8 to 30 years. A loading apparatus applied impulsive test forces to athletes' heads in flexion, extension, lateral flexion, and axial rotation during baseline and anticipatory cervical muscle activation conditions. Multivariate linear mixed models were used to determine the effects of neck strength and cervical muscle activation on head ΔV and Δω.

Results: Greater isometric neck strength and anticipatory activation were independently associated with decreased head ΔV and Δω after impulsive loading across all planes of motion (all P < .001). Inverse relationships between neck strength and head ΔV and Δω presented moderately strong effect sizes (r = 0.417 to r = 0.657), varying by direction of motion and cervical muscle activation.

Conclusion: In male and female athletes across the age spectrum, greater neck strength and anticipatory cervical muscle activation ("bracing for impact") can reduce the magnitude of the head's kinematic response. Future studies should determine whether neck strength contributes to the observed sex and age group differences in concussion incidence.

Clinical Relevance: Neck strength and impact anticipation are 2 potentially modifiable risk factors for concussion. Interventions aimed at increasing athletes' neck strength and reducing unanticipated impacts may decrease the risk of concussion associated with sport participation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1177/0363546513517869DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4344320PMC
March 2014

Exercise interventions, gait, and balance in older subjects with distal symmetric polyneuropathy: a three-group randomized clinical trial.

Am J Phys Med Rehabil 2014 Jan;93(1):1-12; quiz 13-6

From the VISN 8 Patient Safety Center of Inquiry, James A. Haley Veterans Hospital, Tampa, Florida (PAQ, TB, YF, SH-H); Department of Veterans Affairs, Washington, DC (BS); Department of Physical Medicine and Rehabilitation, University of Michigan Health Systems, Ann Arbor (JKR); and Health Services Research & Development, Center of Innovation and Disability Rehabilitation Research, James A. Haley Veterans Hospital, Tampa, Florida (SB).

Objective: Older patients with a distal symmetric polyneuropathy are at markedly increase risk for falls and fall-related injuries. Despite this, few studies have investigated the effect of exercise regimens on gait and balance in this high-risk group.

Design: One hundred older patients with distal symmetric polyneuropathy were randomized to one of three interventions: functional balance training, Tai Chi, or education-only control. The subjects in each group received instruction in ten 1-hr weekly sessions. Outcome measures were determined at baseline and the end of the 10-wk intervention. Gait, balance, and falls self-efficacy were assessed with various well established clinical (Berg Balance Scale, 8 Foot Up and Go Test, and Modified Falls Efficacy Scale) and laboratory-based measures (three-dimensional gait analysis and NeuroCom limits of stability and sensory organization tests).

Results: The Tai Chi subjects demonstrated a decreased (faster) Timed Up and Go and increased stride length and time spent in single limb support at the end of intervention as compared with baseline. The functional balance training group demonstrated a significant increase in ankle plantar flexor power and near significant decreases in step width and step width variability. No changes in the education-only control group were observed.

Conclusions: Older patients with distal symmetric polyneuropathy may benefit from Tai Chi and/or functional balance training, with the former improving functional mobility and gait and the latter possibly improving trunk stabilization and forward progression (Lythgo N, Cofré LE: Relationship between ankle plantar flexor power and EMG muscle activity during gait. 30th Annual Conference of Biomechanics in Sports [Melbourne, 2012]. Available at: https://ojs.ub.uni-konstanz.de/cap/article/viewFile/5320/4891). Whether these laudable changes can be maintained or translate into decreased risk for falls and fall-related injuries is unknown.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1097/PHM.0000000000000052DOI Listing
January 2014

Ulnar neuropathy at the elbow.

Muscle Nerve 2014 Apr 10;49(4):617-8. Epub 2014 Feb 10.

PM&R, University of Michigan, Ann Arbor, Michigan, USA.

View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/mus.24138DOI Listing
April 2014

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

Muscle Nerve 2014 Sep 20;50(3):437-42. Epub 2014 Jan 20.

University of Michigan, Physical Medicine and Rehabilitation, 325 E. Eisenhower Pkwy, Suite 400, Ann Arbor, Michigan, 48108.

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 (Hip(STR) /AnkPRO ) predicted falls (pseudo-R(2)  = .726) and injury (pseudo-R(2)  = .382). No other variable maintained significance in the presence of Hip(STR) /AnkPRO .

Conclusions: Fall and injury risk in the population studied is related inversely to Hip(STR) /AnkPRO . Increasing rapidly available hip strength in patients with neuropathic ankle sensory impairment may decrease risk of falls and related injuries.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/mus.24134DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4033700PMC
September 2014

Step length after discrete perturbation predicts accidental falls and fall-related injury in elderly people with a range of peripheral neuropathy.

J Diabetes Complications 2014 Jan-Feb;28(1):79-84. Epub 2013 Oct 31.

Department of Physical Medicine & Rehabilitation, University of Michigan, Ann Arbor, MI, USA.

Aims: Distal symmetric polyneuropathy increases fall risk due to inability to cope with perturbations. We aimed to 1) identify the frontal plane lower limb sensorimotor functions which are necessary for robustness to a discrete, underfoot perturbation during gait; and 2) determine whether changes in the post-perturbed step parameters could distinguish between fallers and non fallers.

Methods: Forty-two subjects (16 healthy old and 26 with diabetic PN) participated. Frontal plane lower limb sensorimotor functions were determined using established laboratory-based techniques. The subjects' most extreme alterations in step width or step length in response to a perturbation were measured. In addition, falls and fall-related injuries were prospectively recorded.

Results: Ankle proprioceptive threshold (APrT; p=.025) and hip abduction rate of torque generation (RTG; p=.041) independently predicted extreme step length after medial perturbation, with precise APrT and greater hip RTG allowing maintenance of step length. Injured subjects demonstrated greater extreme step length changes after medial perturbation than non-injured subjects (percent change = 18.5 ± 9.2 vs. 11.3 ± 4.57; p = .01).

Conclusions: The ability to rapidly generate frontal plane hip strength and/or precisely perceive motion at the ankle is needed to maintain a normal step length after perturbation, a parameter which distinguishes between subjects sustaining a fall-related injury and those who did not.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jdiacomp.2013.09.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3895931PMC
August 2014

Effect of age on the ability to recover from a single unexpected underfoot perturbation during gait: kinematic responses.

Gait Posture 2013 Sep 13;38(4):853-7. Epub 2013 May 13.

Department of Mechanical Engineering, University of Michigan, 3212 G.G.Brown, 2350 Hayward St, Ann Arbor, MI 48109-2125, United States. Electronic address:

A sudden underfoot perturbation can present a serious threat to balance during gait, but little is known about how humans recover from such perturbations or whether their response is affected by age. We tested the hypothesis that age would not affect the stepping responses to a nominal 10 degree inversion or eversion of the stance foot during gait. Twenty-three healthy young (22.7±3.35 yrs) and 18 healthy old adults (68.0±7.19 yrs) performed 60 walking trials along a 6-m level walkway at a normal gait speed. In 16 of these trials, a single medial (MP) or lateral (LP) perturbation was randomly administered once under the left or right foot. Recovery step width (SW), step length (SL), trunk kinematics and walking speed were measured optoelectronically. Repeated-measures analysis of variance and post hoc t-tests were used to test the hypotheses. The results show that a MP or LP altered the recovery SL (p=0.005) and age affected the number of recovery steps (p=0.017), as well as the first recovery SW and SL (p=0.013 and p=0.031, respectively). Both MP and LP caused young adults to have wider SW (p<0.02) and shorter SL (p<0.005) without changing trunk movement during their first recovery step. Older adults, however, significantly changed lateral trunk inclination during the first recovery step, decreased their fourth recovery SL (p<0.001). We conclude that young adults adjust the step kinematics of as many as four recovery steps following this perturbation, a response that was delayed and significantly weaker in older adults who instead exhibited an immediate torso inclination consistent with a hip response strategy.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.gaitpost.2013.04.013DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3795932PMC
September 2013

Effect of sport-related concussion on clinically measured simple reaction time.

Br J Sports Med 2014 Jan 11;48(2):112-8. Epub 2013 Jan 11.

Department of Physical Medicine & Rehabilitation, University of Michigan, , Ann Arbor, Michigan, USA.

Background: Reaction time (RT) is a valuable component of the sport concussion assessment battery. RT is typically measured using computers running specialised software, which limits its applicability in some athletic settings and populations. To address this, we developed a simple clinical test of RT (RTclin) that involves grasping a falling measuring stick.

Purpose: To determine the effect of concussion on RTclin and its sensitivity and specificity for concussion.

Materials And Methods: Concussed athletes (n=28) and non-concussed control team-mates (n=28) completed RTclin assessments at baseline and within 48 h of injury. Repeated measures analysis of variance compared mean baseline and follow-up RTclin values between groups. Sensitivity and specificity were calculated over a range of reliable change confidence levels.

Results: RTclin differed significantly between groups (p<0.001): there was significant prolongation from baseline to postinjury in the concussed group (p=0.003), with a trend towards improvement in the control group (p=0.058). Sensitivity and specificity were maximised when a critical change value of 0 ms was applied (ie, any increase in RTclin from baseline was interpreted as abnormal), which corresponded to a sensitivity of 75%, specificity of 68% and a 65% reliable change confidence level.

Conclusions: RTclin appears sensitive to the effects of concussion and distinguished concussed and non-concussed athletes with similar sensitivity and specificity to other commonly used concussion assessment tools. Given its simplicity, low cost and minimal time requirement, RTclin should be considered a viable component of the sports medicine provider's multifaceted concussion assessment battery.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1136/bjsports-2012-091579DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3732515PMC
January 2014

How gender and task difficulty affect a sport-protective response in young adults.

J Sports Sci 2013 13;31(7):723-30. Epub 2012 Dec 13.

University of Michigan, Biomedical Engineering, Ann Arbor, Michigan, USA.

We tested the hypotheses that gender and task difficulty affect the reaction, movement, and total response times associated with performing a head protective response. Twenty-four healthy young adults (13 females) performed a protective response by raising their hands from waist level to block a foam ball fired at their head from an air cannon. Participants initially stood 8.25 m away from the cannon ('low difficulty'), and were moved successively closer in 60 cm increments until they failed to block at least five of eight balls ('high difficulty'). Limb motion was quantified using optoelectronic markers on the participants' left wrist. Males had significantly faster total response times (P = 0.042), a trend towards faster movement times (P = 0.054), and faster peak wrist velocity (P < 0.001) and acceleration (P = 0.032) than females. Reaction time, movement time, and total response time were significantly faster under high difficulty conditions for both genders (P < 0.001). This study suggests that baseball and softball pitchers and fielders should have sufficient time to protect their head from a batted ball under optimal conditions if they are adequately prepared for the task.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1080/02640414.2012.746726DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3608833PMC
September 2013

Fibular motor nerve conduction studies and ankle sensorimotor capacities.

Muscle Nerve 2013 Apr 6;47(4):497-503. Epub 2012 Dec 6.

Department of Physical Medicine and Rehabilitation, University of Michigan, 325 East Eisenhower Parkway, Ann Arbor, Michigan 48108, USA.

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 (R(2) = 0.591, P < 0.001), moderately with ankle inversion and eversion rates of torque generation (R(2) = 0.216; P = 0.004 and R(2) = 0.200; P = 0.006, respectively), and more strongly when fibular motor amplitude was normalized for body mass index (R(2) = 0.350; P < 0.001 and R(2) = 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.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/mus.23618DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3608755PMC
April 2013

Which lower limb frontal plane sensory and motor functions predict gait speed and efficiency on uneven surfaces in older persons with diabetic neuropathy?

PM R 2012 Oct 15;4(10):726-33. Epub 2012 Jul 15.

University of Applied Sciences of Western Switzerland, Geneva, Switzerland.

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

Design: Cross-sectional observational study.

Setting: A biomechanics research laboratory.

Participants: Thirty-three subjects (14 women [42.4%]; 21 with diabetic distal symmetric peripheral neuropathy [63.6%]), with a spectrum of lower limb sensorimotor functions that ranged from normal to marked diabetic neuropathy.

Methods: Independent variables included ankle inversion-eversion proprioceptive thresholds, and normalized measures of maximum voluntary strength and maximum rate of torque development (RTD) of hip abduction-adduction and ankle inversion-eversion. Kinematic data were obtained by using an optoelectronic system as subjects walked over an uneven 10-m surface.

Main Outcome Measures: Dependent variables included gait speed and efficiency (determined by step-width-to-step-length ratio) on an uneven surface.

Results: Hip adduction RTD and ankle inversion RTD predicted 54% of gait speed, with the former predicting the majority (44%). Ankle inversion RTD was the only significant predictor of gait efficiency, which accounted for 46% of its variability. Age did not predict gait speed or efficiency.

Conclusions: The rapid generation of strength in the frontal plane at the hip and ankle is responsible for the successful negotiation of irregular surfaces in older persons. Age demonstrated no independent influence. Training regimens in older persons should include maneuvers that rapidly develop strength in hip adductors and ankle invertors if navigation of uneven surfaces is a functional goal.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.pmrj.2012.05.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3477498PMC
October 2012

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

Muscle Nerve 2012 Apr;45(4):578-85

Department of Physiotherapy, University of Applied Sciences of Western Switzerland, Geneva, Switzerland.

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 (R(2) = 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.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/mus.22325DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3313445PMC
April 2012
-->