SCI

Acknowledgement of Country

  • Acknowledgment of the traditional owners of the land.

    • Respect paid to the Gadigal people of the Eora Nation.

    • Recognition of their ancestral lands where the University of Sydney is located.

    • Respect for Elders past, present, and emerging.

Exercise after Spinal Cord Injury

  • Presentation by Professor Glen Davis at The University of Sydney.

Core Knowledge

  • Section highlighting fundamental aspects relating to spinal cord injuries (SCI).

Understanding Spinal Cord Injury (SCI)

What is SCI?

  • Definition:

    • Disruption of motor pathways leads to muscle paralysis (e.g., loss of motor control to legs).

    • Disruption of sensory pathways causes inability to sense (e.g., loss of sensory feedback from legs).

    • Loss of autonomic function results in disordered reflexes (e.g., impaired sweat response, disordered bowel, bladder, and sexual functions).

    • Autonomic pathway disruption impairs organ function and affects integrated physiological processes.

  • Lesion levels:

    • C1-C8: Upper cervical lesions can impair respiratory function and all aspects of autonomic control - may also lead to hypotension, cardio-respiratory instability, and loss of thermoregulation, which contribute significantly to decreased overall health and increased complications in affected individuals.

    • T1-T6: Thoracic lesions typically impact the upper trunk and may lead to cardiovascular instability, affecting heart rate and blood pressure regulation. This can result in increased susceptibility to autonomic dysreflexia, a condition that can cause severe hypertension and other life-threatening symptoms.

    • T7-T12: Lower thoracic lesions may affect abdominal and pelvic organ functions, possibly leading to issues with bowel and bladder control, as well as impairments in lower limb movements.

    • L1-L5: Lumbar lesions can result in lower limb motor dysfunction, with potential impacts on bladder and bowel control.

    • S1-S5: Sacral lesions can lead to deficits in sexual function and further compromise bladder and bowel control, often exacerbating previous dysfunctions.

Classifying Spinal Cord Injury

(A) Neurological Level of Lesion

  • Most caudal segment where normal sensory and motor function is present.

  • Types:

    • Paraplegia: refers to injury affecting the legs.

    • Tetraplegia (also known as Quadriplegia): refers to injury affecting all four limbs.

(B) Severity of Lesion (ASIA)

  • Classification according to the American Spinal Injury Association:

    • Complete lesions: No sensory or motor function below the level of injury.

    • Incomplete lesions: Preservation of some sensory or motor function below the level of injury.

ASIA Impairment Scale Classification

  • Class A: Complete, no sensory motor function below the lesion.

  • Class B: Incomplete, sensory function preserved but no motor function below the lesion.

  • Class C: Incomplete, motor function preserved below the lesion but with weak strength.

  • Class D: Incomplete, motor function preserved below the lesion with near normal strength.

  • Class E: Normal sensory and motor functions.

Key Physiological Changes After SCI

  1. Muscle spasms: Involuntary contractions due to nerve damage.

  2. Muscle morphological adaptations: Changes in muscle structure due to disuse or decreased activation.

  3. Circulation changes: Alterations in blood flow and pressure regulation.

Secondary Medical Complications

  1. Pressure sores:

    • Caused by prolonged pressure on skin and muscle.

    • Most common in areas such as ischial tuberosities - glutes and hamstrings.

    • Treatment may be prolonged due to impaired circulation - can take 8 weeks to 4 months on stomach in hospital bed.

    • Exercise: will have to be modified to accommodate pressure sore - prone lying.

  2. Bone demineralization: Loss of bone density due to lack of weight-bearing activity.

  3. Low BP and orthostatic intolerance:

    • Impaired circulation may lead to decreased blood pressure, especially in individuals with high-level injuries.

    • Symptoms include dizziness or fainting upon standing.

    • Postural changes leading to lower blood pressure followed by impaired corrective mechanisms as the body struggles to adapt to the changes in position, resulting in insufficient blood flow to the brain and other vital organs.

  4. Autonomic Dysreflexia:

    • Symptoms:

      • High blood pressure

      • Drop in heart rate

      • Headache, sweating, nausea, gooseflesh.

    • Potential complications:

      • Myocardial failure

      • Neurological deficits (e.g., seizures)

      • Visual defects

      • Cerebral hemorrhage.

    • Management involves identifying and addressing the provoking cause.

    • Stop exercise straight away, lie person down and call triple zero.

Cardiovascular Disease Risk Factors in SCI

  1. Habitual activity and energy expenditure: Sedentary lifestyle leads to a lower basal metabolic rate - 1MET = 2-2.3 for tetraplegic & 2.3-3.5 for paraplegic. 1MET = 3.5 (normal)

  1. Changes in body composition:

    • Increased body fat percentage.

    • Decreased lean muscle mass.

  2. Disorders of carbohydrate metabolism:

    • Impaired glucose tolerance.

    • Hyperinsulinemia indicates an imbalance in insulin regulation.

Acute Responses to Exercise After SCI

Unique Differences Affecting Exercise Prescription (ExRx)

  • Impaired blood flow during upper-body ergometry (UBE).

    • Majority of blood flow directed to legs and thorax, venous pooling occurs in legs.

    • Thoraco-lumber pump: A mechanism that helps facilitate venous return from the lower body to the heart, enhancing blood circulation during exercise.

Impact on Submaximal vs Maximal Exercise

  • Findings from studies (Hopman et al, 1992):

    • Higher venous pooling due to leg paralysis leads to:

    • Lower peak capacity.

    • Using VO2peakVO2_{peak} instead of VO2maxVO2_{max}.

    • Submaximal exercise being more fatiguing and prone to exercise-induced hypotension.

Fitness, Physical Activity, and Functional Assessments After SCI

  • Multiple methods exist for assessing fitness levels post-SCI, including cardiovascular and strength assessments.

Estimation of VO2peakVO2_{peak} in SCI

  • Prediction equations utilized:

    • Based on submaximal exercise efforts, typically involving 3+ incremental workloads with rest intervals.

    • “The Toronto Protocol” study reference for assessment methodology.

Guidelines for Assessing extVO2max{ ext{VO2}}_{max}

  1. Conduct three or more submaximal steady-state arm exercises.

  2. Convert work rates into VO2VO2 estimates using specific arm cycling equations.

  3. Predict VO2peakVO2_{peak} from the linear relationship between heart rate and VO2VO2.

Normative Fitness Classifications (USA) by O'Keefe et al (2014)

  • Assessments based on a range of fitness measures across different categories for men with paraplegia (PP) and tetraplegia (TP):

    • R-VO2peakVO2_{peak} (mL·kg−1·min−1):

    • TP breakdown: Poor < 5.30, Fair 5.30–7.90, Average 7.91–9.50, Good 9.51–15.18, Excellent >15.18.

    • PP similar classifications assessed.

    • A-VO2peakVO2_{peak} (L/min):

    • Similar classifications for TP and PP under the same metrics as above.

Strength and Endurance Assessments

  • Standard of 1-Repetition Max (1-RM) should be measured instead of predicted. Important for upper body (AIS A & B) and both upper and lower bodies (AIS C & D) injury classifications.

  • Assessment metrics include active and passive range of motion and joint flexibility.

Functional Tests

  • 6-Minute Walk Test (6MWT):

    • Developed by the American Thoracic Society to measure performance capacities during wheelchair propulsion or walking within the limitations of SCI.

    • A submaximal exercise test influential in evaluating overall functional capacity including muscle strength and endurance, pulmonary and cardiovascular response, blood circulation, neuromuscular coordination, and motor control.

    • Note: Not a decisive measure for VO2peakVO2_{peak} in the SCI population.

Six-Minute Wheelchair Push Test for Aerobic Fitness

  • Study conducted with N = 40 SCI individuals assessing fitness levels based on distances achieved during the test. Metrics delineated for classification of fitness levels based on test outcomes:

    • High Fitness thresholds established: Tetraplegia > 445m, Paraplegia > 604m.

    • Overall accuracy of 70% among participants.

Physical Activity Recall Assessment for People with SCI

  • Focused assessment capturing type, frequency, and intensity of physical activity over the past week.

    • Categories classified by light, moderate, and heavy (vigorous) physical activity as well as strength training activities.

Evidence on Exercise Prescription After Spinal Cord Injury

  • Exercise prescription parameters:

    • Frequency: 3-5 times per week.

    • Intensity: 50%-80% heart rate reserve.

    • Time: 20-60 minutes per session.

    • Type of program: Individualized (I) or categorical (C).

Guidelines for Aerobic Exercise Post-SCI

  • Recommendations from the Journal of Science and Medicine in Sport (2017):

    • Moderate-intensity: Over 30 minutes/day for more than 5 days/week, totaling 150 minutes weekly.

    • Vigorous-intensity: Over 20 minutes/day for more than 3 days/week, totaling 75 minutes weekly.

    • Combination efforts aiming for an energy expenditure total greater than 500-1000 MET·min·wk−1.

Resolving the Evidence?

  • Emphasis on defining starting levels of activity for achieving fitness benefits, delineated into advanced levels that also reduce risks of diabetes and heart disease, including dynamic activities like hand cycling and swimming versus strength training for enhanced muscle strength.

Functional Electrical Stimulation (FES) Approaches

  • Various FES methods targeting enhancing function and muscle activity through electrical stimulation of specific muscle groups to promote health and physical activity.

Summary of Evidence for Outcomes Post-FES Exercise

  • Each outcome category analyzed with specific results indicating the levels of improvement:

  • Muscle health and power output showed high levels of evidence for improvement, while cardiovascular/movement effects exhibited low certainty in outcomes.

Activity-Based Therapy (ABT)

  • Definition: Interventions targeting activation of the neuromuscular system below the level of the lesion to promote motor task recovery (Behrman and Harkema, 2000).

Theories of Activity-Based Therapy

  • Relevant Theoretical Frameworks:

    • Neuroplasticity

    • Motor Control Re-learning

    • Overload Adaptation

  • Targets include spinal cord, brain, and muscles to elicit therapeutic benefits.

Benefits of Activity-Based Therapy

  • Improved outcomes reported include:

    • Functional independence

    • Enhanced physical wellbeing and confidence

    • Overall health benefits including quality of life and social interactions.

Thank You!

  • Closing remarks from The University of Sydney.