Brad M. Johnson

Metabolic and cardiac responses to robotic-assisted locomotion in motor-complete tetraplegia: a case report.

Abstract Background/Objective: To examine acute metabolic responses to treadmill locomotion in a participant with motor—complete tetraplegia. Methods: The participant—a woman with a chronic ASIA B C3–C4 spinal cor injury—walked on a treadmill with 40% body weight support (BWS) and robotic assistance. Oxygen consumption (VO2), minute ventilation (VE),and heart rate (HR) were measured during seated resting, supported standing, and 40 minutes of walking with stepping assistance from a Lokomat-driven gait orthosis. Results: A resting VO2 equal to 50 milliliters perminutewas predictably low, and did not change after the participant assumed an upright posture. Both VO2 and V2E increased immediately upon onset of locomotion, suggesting a neuragenie rather than a humoral regulatory response to movement. VO2 averaged 2.4 metabolic units (METS) during locomotion at an average expenditure of 2.98 kilocalories per minute. HR was unaltered by standing, but du ring locomotion averaged 1 7 beats higherthan du ring resting.lncreases in V E but not vo2 upon standing, and decreases in vo2 but not V E immediately after walking, rule out changes in V2E alone as the source for increased vo2 du ring walking. Conclusion: The data collected on this single participant show that treadmilllocomotion with BWS and robotic assistance elicits a metabolic response to treadmill gaiting characterized by increased VO2 , VE HR, and caloric expenditure

Reliability Of Arm Wingate Anaerobic Testing In Persons With Complete Paraplegia

Abstract Background: Accurate, reliable assessment of upper extremity muscular power in persons with paraplegia caused by spinal cord injury (SCI) would provide an objective indication of their ability to generate the forces necessary for the performance of daily activities. Wingate Anaerobic Testing (WAnT) consists of a 30-second sprint test on a cycle ergometer and has been used widely in both athletic and research settings. Purpose: To examine test-retest reliability of arm WAnT performance in persons with complete SCI and paraplegia. Methods: Forty-three participants with thoracic-level paraplegia (T2 through T12) performed 2 trials of arm WAnT with 2 to 7 days between each trial. Testing was performed using a Monarch 834E ergometer with participants seated in their wheelchairs. Participants were directed to crank at maximal pace for 30 seconds against a resistance load equivalent to 3.5% of their body mass. The SMI OptoSensor 2000 system was used to determine values of peak power (Ppeak), mean power (Pmean), minimum power, and rate of fatigue, which were compared between trials using 1-way analysis of variance for repeated measures. Coeffi cients of determination (r2) were calculated between trials for Ppeak and Pmean. Results: No significant diffe rence was found between trials for any of the power output variables. Regression analysis ind icat ed that Ppeak and Pmean were closely associated between the 2 trials (r2= 0.92 and 0.94, respectively). Conclusion: Arm WAnT is a reliable measurement tool for the assessment of upper extremity muscular power in persons with complete paraplegia.

Physiologic responses to electrically assisted and frame-supported standing in persons with paraplegia.

Abstract Background: Systems of functional electrical stimulation (FES) have been demonstrated to enable some persons with paraplegia to stand and ambulate limited distances. However, the energy costs and acute physiologic responses associated with FES standing activities have not been well investigated. Objective: To compare the physiologic responses of persons with paraplegia to active FES-assisted standing (AS) and frame-supported passive standing (PS). Methods: Fifteen persons with paraplegia (T6-T11) previously habituated to FES ambulation, completed physiologic testing of PS and AS. The AS assessments were performed using a commercial FES system (Parastep-1; Altimed, Fresno, Calif); the PS tests used a commercial standing frame (Easy Stand 5 000; Altimed, Fresno, Calif) . Participants also performed a peak arm-cranking exercise (ACE) test using a progressive graded protocol in 3 -minute stages and 1 0-watt power output increments to exhaustion. During all assessments, metabolic activity and heart rate (HR) were measured via open-circuit spirometry and 12-lead electrocardiography, respectively. Absolute physiologic responses toPS and AS were averaged over 1-minute periods at 5-minute intervals (5 , 10, 15, 20, 25, and 30 minutes) and adjusted relative to peak values displayed during ACE to determine percentage of peak (%opk) values. Absolute and relative responses were compared between test conditions (AS and PS) and across time using two-way analysis of variance. Results: The AS produced significantly greater values of V02 (43%pk) than did PS (20%pk). The mean HR responses to PS (100-102 beats per minute [bpm] throughout) were significantly lower than during AS, which ranged from 108 bpm at 5 minutes to 132 bpm at test termination. Conclusion: Standing with FES requires significantly more energy than does AS and may provide a cardiorespiratory stress sufficient to meet minimal requirements for exercise conditioning.

Combined Hyperlipidemia In A Single Subject With Tetraplegia: Ineffective Risk Reduction After Atorvastatin Monotherapy

Abstract Background/Objective: Effects of atorvastatin (Lipitor) drug monotherapy (1 0 mg daily) on fasting blood Iipid profiles and cardiovascular disease (CVD) risks were examined for a single subject with C5-C6 tetraplegia. Routine fasting Iipid profiles were analyzed by standard biochemistry techniques for total cholesterol (TC) , triglycerides (TG) , low-density lipoprotein-cholesterol (LDL-C) , and high-density lipoprotein-cholesterol (HDL-C). Lipid profiles were analyzed on 3 occasions before drug therapy was initiated and 3 months after therapy commenced. The TC:HDL and LDL:HDL ratios were computed for all sampling times and used to assess pretreatment and post-treatment CVD risk. Results: Fasting TC, TG, and LDL-C were all significantly reduced by therapy. The pretreatment HDL-C of 3 5 mg/ dl was lowered to 21 mg/ dl. As a result, the TC:HDL risk ratiowas only marginally reduced from 6 .6 to 6.4, whereas the LDL:HDL risk ratio remained unchanged by treatment. Conclusions: In this man with tetraplegia, atorvastatin drug monotherapy rapidly lowered TC, TG, LDL-C, and HDL-C. However, the TC: HDL ratio, considered the best predictor of CVD risk, was unchanged.

Effect of variable loading in the determination of upper-limb anaerobic power in persons with tetraplegia

This article examines the effects of levels of resistance loading during arm Wingate Anaerobic Testing (WAnT) in persons with differing levels of cervical spinal cord injury (SCI). Thirty-nine persons with motor-complete SCI tetraplegia (13 each at C5, C6, and C7) performed six bouts of arm-crank WAnT with relative loads equivalent to 1.0, 1.5, 2.0, 2.5, 3.0, and 3.5 percent of body mass (BM). Power output was determined with the use of the SMI OptoSensor 2000 (Sports Medicine Industries, Inc., St. Cloud, MN, USA) hardware and software package. Values of peak power (P(peak)) and mean power (P(mean)) were examined statistically between groups (C5, C6, and C7) and across levels of resistance loading. Resistance loads that provided the greatest values of P(mean) for the three groups were as follows: C5 = 1.0 or 1.5 percent of BM; C6 = 1.5 or 2.0 percent of BM; and C7 = 2.5, 3.0, or 3.5 percent of BM. Appropriate loading for arm WAnT is specific to the level of tetraplegia and may provide a useful assessment of upper limb power production.

Reliability of upper extremity anaerobic power assessment in persons with tetraplegia.

Abstract Background/Objective: Reliable assessment of upper extremity anaerobic power in persons with cervical spinal cord injury (SCI) may indicate the ability to successfully and safely perform many daily activities. Purpose: To examine test-retest reliability of upper extremity Wingate anaerobic testing (WAnT) in persons with motor/sensory complete tetraplegia. Methods: Forty-five persons with cervical-level SCI (15 individuals each at C5, C6, and C7 levels of injury) performed 2-arm WAnT bouts, with 2 to 4 days between bouts. Subjects performed the WAnT seated in their wheelchairs using a tabletop-mounted Monarch 834E ergometer. Resistance loads were applied relative to injury level, with 1%, 2%, and 3% of body mass applied to subjects with C5, C6, and C7 level injuries, respectively. All subjects were directed to crank the ergometer at maximal velocity for a30-second period. Values of peak power (P peak) and mean power (P mean) were determined using an SMI OptoSensor 2000 system. P peak and P mean were compared between trials and between groups using 2-way analyses of variance for repeated measures. Coefficients of determination (r2) were calculated between trials. Results: There were no significant differences in P peak or P mean detected between the 2 trials of WAnT in the C5, C6, or C7 groups. Regression analyses revealed statistically significant associations between bouts for Pmean and P peak in each of the 3 groups (P < 0.05). Conclusions: Upper extremity WAnT is reliable for upper extremity anaerobic power assessment in persons with cervical SCI at or below the C5 level.