In this area of the website you will find abstracts of studies that have been authored or co-authored by Project Walk staff. All abstracts were either presented at scientific conferences and/or published in peer reviewed journals.

Substrate metabolism during exercise in the spinal cord injured

Eur J Appl Physiol. (2009) Feb 18. [Epub ahead of print]

Astorino TA1, Harness ET2.
1California State University San Marcos, Department of Kinesiology, San Marcos, CA, USA.
2Project Walk Spinal Cord Injury Recovery, Department of Research and Development, Carlsbad, CA, USA

Background
The primary aim of the study was to examine substrate metabolism during combined passive and active exercise in individuals with spinal cord injury (SCI).

Methods
Nine men and women with SCI (mean age 40.6 +/- 3.4 years) completed two trials of submaximal exercise 1 week apart. Two maintained a complete injury and seven had an incomplete injury. Level of injury ranged from thoracic (T4-T6 and T10) to cervical (four C5-C6 and three C6-C7 injuries). During two bouts separated by 1 week, subjects completed two 30 min sessions of active lower-body and passive upper-body exercise, during which heart rate (HR) and gas exchange data were continuously assessed. One-way analysis of variance with repeated measures was used to examine differences in all variables over time.

Results
Results demonstrated significant increases (P < 0.05) in HR and oxygen uptake (VO(2)) from rest to exercise. Respiratory exchange ratio (RER) significantly increased (P < 0.05) during exercise from 0.85 +/- 0.02 at rest to 0.95 +/- 0.01 at the highest cadence, reflecting increasing reliance on carbohydrate from 50.0 to 83.0% of energy metabolism.

Conclusion
Data demonstrate a large reliance on carbohydrate utilization during 30 min of exercise in persons with SCI, with reduced contribution of lipid as exercise intensity was increased. Strategies to reduce carbohydrate utilization and increase lipid oxidation in this population should be addressed.

Effects of intense exercise in chronic spinal cord injury

Spinal Cord (2008) 46, 733–737

E T Harness1, N Yozbatiran2,3 and S C Cramer2,3
1Project Walk Spinal Cord Injury Recovery, Department of Research and Development, Carlsbad, CA, USA
2Department of Neurology, University of California, Irvine, CA, USA
3Department of Anatomy and Neurobiology, and the Reeve-Irvine Research Center, University of California, Irvine, CA, USA

Background:
Exercise has beneficial effects on muscle and motor function after spinal cord injury (SCI). Little is known regarding effects of prolonged intense exercise (IE) in humans with chronic SCI.

Design:
Prospective, non-randomized, controlled observational study. The intervention was either a multimodal IE program (n=21) or a control (CTL) intervention consisting of self-regulated exercise (n=8).

Objective:
Measure sensorimotor function over 6 months in relation to an IE program.

Setting:
Single outpatient center.

Subjects:
Subjects with chronic SCI (n=29 total), mainly ASIA Impairment Scale A and B, injury levels C4-T11.

Results:
Baseline neurological assessments (for example, ASIA motor score, 393 vs 425, IE vs CTL, P>0.5, means.e.m.) did not differ between the two groups. During the 6 months, IE subjects averaged 7.30.7 h per week exercise, not significantly different from CTL subjects (5.21.3 h per week, P>0.1). However, after 6 months, IE subjects showed significantly greater motor gains than CTL subjects in the main outcome measure, ASIA motor score (change of 4.81.0 vs -0.10.5 points, P=0.0001). The main outcome measure was calculated by ASIA motor score. These IE subject ASIA motor gains correlated with number of exercise hours per week (r=0.53, P<0.02), and with type of specific IE components, particularly load bearing.

Conclusions:
Multimodal IE can significantly improve motor function in subjects with chronic SCI. An organized program may provide greater motor benefits than a self-regulated program; load bearing might be of particular value. IE might have therapeutic value in chronic SCI, and as an adjunct to other restorative therapies.

Efficacy of a new rehabilitative device for individuals with spinal cord injury

J Spinal Cord Med (2008) 31(5), 586-91

T A Astorino1, N Tyerman1, K Wong1, E Harness2.
1California State University San Marcos, Department of Kinesiology, San Marcos, CA, USA.
2Project Walk Spinal Cord Injury Recovery, Department of Research and Development, Carlsbad, CA, USA

Backgound:
Regular exercise is required in persons with spinal cord injury (SCI) to reduce the deleterious effects of chronic paralysis. The primary aims of the study were to examine responses to passive and active exercise on a new rehabilitative device for persons with SCI and to examine reliability of these responses over 2 days of testing.

Methods:
Nine men and women with chronic SCI completed the study, 2 with a complete injury and 7 with an incomplete injury. The level of injury ranged from thoracic (T4-T6 and T10) to cervical (4 with C5-C6 and 3 with C6-C7 injuries). They completed 2 30-minute sessions of active lower-body and passive upper-body exercise, during which heart rate (HR), blood pressure (BP), gas exchange data, rating of perceived exertion (RPE), and oxygen-hemoglobin saturation were continuously assessed. Data Analysis: One-way ANOVA with repeated measures was used to examine differences in all variables over time.

Results:
Results demonstrated significant increases (P < 0.05) in HR, systolic BP, RPE, and oxygen uptake (V(O2)) from rest to exercise. No change (P > 0.05) in diastolic BP or oxygen-hemoglobin saturation was evident. Cronbach's alpha values for HR, systolic BP, and V(O2) recorded over both days of testing ranged from 0.79 to 0.97, indicating adequate consistency.

Conclusions:
Data demonstrated that exercise on this device significantly increases HR, V(O2), and systolic BP compared to rest. However, its efficacy for long-term rehabilitation, especially in regular exercisers with SCI, is unknown.