Project Walk Research

The Science Behind Project Walk
Over the past several years, Project Walk has embarked on an ambitious research agenda that is focused on determining the physiological, neurological, and functional changes that are a result of our methodologies and modalities. Through collaborating with universities and hospitals, we have been able to design and implement various projects that have led to publications in multiple peer-reviewed journals, and presentations at scientific conferences. This research allows us to refine and evolve our program in ways that other programs cannot.
Research at Project Walk is conducted through our Department of Research and Development at Project Walk Headquarters in Carlsbad, CA. If you would like further information about our current projects, previous results, or how to collaborate with Project Walk. Please visit our CONTACT US page.
Research Collaborations
Throughout the years, Project Walk has been able to collaborate with many institutions to progress the field of activity-based recovery through research. These collaborations include joint research projects/presentations with the following entities and/or representatives:
  • California State University - San Marcos
  • Center for Spinal Cord Injury Recovery at the Rehabilitation Institute of Michigan
  • Craig Hospital
  • Reeve-Irvine Research Center in Irvine California
  • Shepherd Center
  • University of California - Irvine
Research Highlights
Project Walk has published several studies on spinal cord injury in peer-reviewed journals and/or as poster presentations at conferences. Here are some of the highlights of those studies, which have been authored or co-authored by Project Walk research staff. Studies are listed chronologically.
Effect of Chronic Activity-Based Therapy on Bone Mineral Density and Bone Turnover in Persons with Spinal Cord Injury - VIEW PDF
Purpose: Osteoporosis is a severe complication of spinal cord injury. Many exercise modalities are used to slow bone loss, yet their efficacy is equivocal. This study examined the effect of activity-based therapy (ABT) targeting the lower extremities on bone health in individuals with spinal cord injury.
Methods:Thirteen men and women with spinal cord injury (age and injury duration = 29.7 ± 7.8 and 1.9 ± 2.7 years) underwent 6 months of ABT. At baseline and after 3 and 6 months of training, blood samples were obtained to assess bone formation (serum procollagen type 1 N propeptide (PINP) and bone resorption (serum C-terminal telopeptide of type I collagen (CTX), and participants underwent dual-energy X-ray absorptiometry scans to obtain total body and regional estimates of bone mineral density (BMD).
Results: Results demonstrated significant increases (p < 0.05) in spine BMD (+4.8 %; 1.27 ± 0.22–1.33 ± 0.24 g/cm2) and decreases (p < 0.01) in total hip BMD (−6.1 %; 0.98 ± 0.18–0.91 ± 0.16 g/cm2) from 0 to 6 months of training. BMD at the bilateral distal femur (−7.5 to −11.0 %) and proximal tibia (− 8.0 to −11.2 %) declined but was not different (p > 0.05) versus baseline. Neither PINP nor CTX was altered (p > 0.05) with training.
Conclusions: Chronic activity-based therapy did not reverse bone loss typically observed soon after injury, yet reductions in BMD were less than the expected magnitude of decline in lower extremity BMD in persons with recent spinal cord injury.
Neurotrophic Response to Acute Activity-based Therapy in Persons with Spinal Cord Injury
Background: Activity-based therapies focus on regaining motor and sensory function below the level of the lesion in persons with a spinal cord injury. This is accomplished through repetitive training of specific motor tasks. Research has shown that exercise after spinal cord injury may be effective to increase neuroplasticity in the rat and human spinal cord, however, the mechanisms of this neuroplasticity are still relatively unknown (Dunlop,2008). Several animal studies have suggested that neurotrophic factors released during exercise may be a contributing influence (Ying et al.,2005).
Objective: The primary aim of this study was to examine alterations in neuroplasticity-related proteins during activity-based therapy in men and women with a spinal cord injury.
Methods: Volunteers were current participants in an activity-based therapy program and consisted of 12 men and 3 women (age=31.8±10.9years) with chronic a spinal cord injury (injury duration=63.9±54.4months). Injury levels were between C4 and L1, with 11 tetraplegics and 4 paraplegics. AIS Grade A-C (5A/4B/6C). Participants completed a single 2 hour bout of activity-based therapy consisting of 30 minutes each of standing load bearing, body weight supported treadmill training (60%/0.54m/s), whole body vibration (35Hz/2mm), and functional electrical stimulation (36-140mA/250µs/33.3Hz) after a 2 hour fast. Blood samples were obtained at baseline and immediately after completion of each exercise mode to determine serum levels of brain-derived neurotrophic factor (BDNF), prolactin, and cortisol.
Results: Results revealed baseline levels of BDNF (2.37±1.41ng/mL) which were lower than previous research has demonstrated in those with a spinal cord injury. One-way ANOVA with repeated measures was used to examine differences in proteins over time during exercise. Overall no significant change in BDNF (p=0.97) or cortisol (p=0.07) was found, although prolactin was significantly reduced (p=0.001) in response to activity-based therapy. 6 of 15 subjects demonstrated increases in BDNF from baseline to post-exercise, and the mean percent change was equal to 17.8±52.7%. Univariate ANOVA revealed that overall BDNF levels were higher (p<0.05) in paraplegics versus tetraplegics. Percent change in cortisol concentration from baseline to after exercise was equal to 82.9±121.1% and ranged from -53.4–294.2%, respectively, across subjects. 8 of 15 individuals showed marked increases in cortisol during exercise.  Post hoc analyses revealed that prolactin was greater (p<0.05) in paraplegics versus tetraplegics at baseline as well as after load bearing. Within paraplegics, prolactin decreased (p<0.05) from baseline to all modalities with the exception of load bearing
Conclusion: Despite the relatively prolonged duration of this bout, its intensity may be too low to elicit significant changes in BDNF. Whether different intensities or modalities of activity-based therapy may promote acute or chronic increases in serum BDNF in individuals with a spinal cord injury remain to be determined and further study is merited.

Activity-based Therapies in Spinal Cord Injury: Clinical Focus and Empirical Evidence in Three Independent Programs
Summary: This article summarizes presentations of a symposium examining the potential impact of activity-based therapy in promoting neurological and functional recovery after spinal cord injury. The symposium addressed 3 key questions concerning activity-based therapy in spinal cord injury: (1) What clinical approaches are used? Principles and techniques used in 3 independent programs – Project Walk Spinal Cord Injury Recovery Center, the Center for SCI Recovery at the Rehabilitation Institute of Michigan, and Shepherd Center’s Beyond Therapy program – are compared and contrasted. (2) Is there empirical evidence supporting efficacy of activity-based therapy in promoting neurological recovery and improving overall function, health, and quality of life? Preliminary findings from each program are presented. (3) What are the issues related to long-term viability of activity-based therapy? Discussion focused on determining who benefits from activity-based therapy, gauging the point of diminishing return with respect to functional recovery, and strategies for maintaining any gains achieved from therapy.
Click here to review the article in PDF form
Acute Energy Cost of Multi-Modal Activity Based Therapy in Persons with Spinal Cord Injury
Objective: To examine acute energy costs of multi-modal activity-based therapy in men and women with spinal cord injury.
Setting: Project Walk Spinal Cord Injury Recovery Center
Participants: Seven men and women (age = 28.3 ± 11.6 years; duration of injury = 4.3 ± 2.5 years) with injury levels ranging from C5 to T8.
Intervention: Activity-based therapy.
Outcome measures: Oxygen uptake (VO2), energy expenditure (kcal/minute), SCI Metabolic Equivalent of Task (MET) (1 MET=2.7 ml/kg/minute).
Results: Oxygen uptake (VO2) during ABT ranged from 5.10 to 8.62 ml/kg/minute, with VO2 consistently higher during modalities involving load bearing versus non-load bearing (P=0.08). SCI MET values ranged from 1.89 to 3.24 and were significantly higher in subjects with mid-thoracic injury versus low-cervical injury (P=0.01).
Conclusion: Data reveal that multi-modal ABT increases VO2 in persons with a spinal cord injury, but energy expenditure is relatively low. Strategies must be identified to optimize energy expenditure in the spinal cord injury to reduce health risks. Modalities involving load bearing seem to be superior to non-load-bearing activities. VO2 was greater in response to load-bearing modalities than non-load-bearing modalities. It remains to be determined whether chronic activity-based therapy enhances cardiovascular fitness and reduces disease risks in this population.
A Tele-Assessment System for Monitoring Treatment Effects in Subjects with Spinal Cord Injury - VIEW PDF
Summary: We developed a method for remote measurement of balance and leg force in patients with spinal cord injury. In a group of 21 patients, both telemedicine and conventional clinical assessments were conducted at baseline and six months later. Telemedicine assessments were successfully acquired and transmitted at first attempt. The time required to set up the telemedicine equipment, position the subject, perform the measurements, and then send the data to the university laboratory was approximately 30 minutes. After six months, several motor and sensory functions showed significant changes. There were significant correlations between changes in remotely-measured leg force and changes in several of the American Spinal Injury Association (ASIA) sensory and motor scores. Changes in balance did not show any significant correlations with changes in the ASIA scores. Intra-rater reliability was better than inter-rater reliability. Use of telemedicine to remotely monitor changes in patients with spinal cord injury appears promising.
Substrate Metabolism During Exercise in the Spinal Cord Injured - VIEW PDF
Background: The primary aim of the study was to examine substrate metabolism during combined passive and active exercise in individuals with spinal cord injury.
Methods: Nine men and women with a spinal cord injury (mean age 40.6 +/- 3.4 years) completed two trials of submaximal exercise one 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 one 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 a spinal cord injury, 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 - VIEW PDF
Background: Exercise has beneficial effects on muscle and motor function after spinal cord injury. Little is known regarding effects of prolonged intense exercise (IE) in humans with chronic spinal cord injury.
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: Project Walk Spinal Cord Injury Recovery Center
Subjects: Subjects with chronic spinal cord injury (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 spinal cord injury. 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 spinal cord injury, and as an adjunct to other restorative therapies.
Efficacy of a New Rehabilitative Device for Individuals with Spinal Cord Injury - VIEW PDF
Background: Regular exercise is required in persons with spinal cord injury 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 spinal cord injury 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 spinal cord injury, is unknown.
Efficacy of Multimodal Training to Alter Bone Mineral Density and Body Composition in Persons with Spinal Cord Injury: A Case Study.
Summary: Approximately 12,000 spinal cord injuries occur annually, with 80 % of injuries occurring in men. A severe complication of acute spinal cord injury is osteoporosis, which is localized at the proximal tibia and distal femur that typically receive loading. Bone loss enhances fracture occurrence at the knee and hip in everyday activities involving little to no trauma. Because bone loss and subsequent fractures elicit severe clinical, psychological, and financial complications, early intervention to slow rate of bone loss in persons with a spinal cord injury is essential. Efficacy of exercise training to slow bone loss or promote new bone formation in this population is equivocal, as many studies have failed to provide a sufficient ‘mechanostat’ threshold to promote bone growth.

In this study, one subject participated in a preliminary investigation in which DXA scans were performed at baseline and after 6 mo to assess bone mineral density (BMD). A 21 year-old woman two months post-SCI (ASIA A complete injury at C5) underwent 6 mo of intense training 2-3 d/wk, 2-3 h/d, consisting of vibration training, body weight support treadmill training, resistance training, electrical stimulation, and load-bearing exercise. Her training program was developed and supervised by experienced personnel certified in activity-based recovery of persons with a spinal cord injury.

Results demonstrated that distal femur BMD was increased by 10 % with training, yet proximal tibia (-14%) and total body leg BMD (-10%) were reduced. Dramatic losses in BMD were observed for the right/left femoral neck (6.8 – 11.4%) and greater trochanter (19.2 – 21.9%). Body mass was increased by 6.4 kg, with the excess mass attributed to a 35% increase in fat mass (FM) and minimal decrement (-1.5%) in lean body mass (LBM). Percent body fat increased from 33.5 – 41.2%, with increased FM revealed in the arms (10%), legs (27%), and trunk (52%). LBM was increased in the legs (11%), although attenuated in the arm (-14%) and trunk (-7%). Leg LBM is typically decreased soon after SCI, and total-body and regional depots of fat mass are typically increased. The observed increase in leg LBM highlights the benefits of intense, multi-modal training to preserve muscle mass. The marked bone loss at the hip has inspired modification of her current training to increase loading at this site to potentially slow bone loss and reduce fracture risk.
San Diego, CA