Sympathetic-Somatomotor Coupling in Human Spinal Cord Injury
Condition: Spinal Cord Injury
MeSH terms: Spinal Cord Injuries; Wounds and Injuries
Study type: Interventional

Summary: 
      Significance: The long term objective of this study is to improve physical therapy and
      fitness programs in people with spinal cord injury. The results of the study will demonstrate
      the importance of matching blood flow to a muscle with exercise of that same muscle.

      Scientific Objective: The objective of the study is to measure how the body regulates
      bloodflow to a muscle during exercise. We intend to study these effects by triggering blood
      flow changes during movement, and measuring bloodflow changes during exercise in people with
      spinal cord injury. We will also look at the long term effects of different exercise programs
      on bloodflow during exercise.

      Study Populations: This study will involve people with partial spinal cord injury and age and
      sex matched controls without injury.

      Specific Aims: Aim 1 will be to measure bloodflow during exercise of the legs (below the
      injury). This aim will examine the control of bloodflow and muscle contractions and how it
      changes after spinal cord injury. Aim 2 will then look at changes in bloodflow during
      exercise after training. Three different eight week exercise training programs will be tested
      including 1) upper body ergometry, 2) treadmill training with exertion level matched to the
      upper body ergometry and 3) treadmill training with heart rate matched to an initial test of
      upper body ergometry.
    

Detailed description: 
      The regulation of cardiovascular systems during muscle activity is poorly understood in
      people with incomplete spinal cord injury (SCI). In the past, disruptions in somatomotor and
      sympathetic control have been investigated separately in SCI. We propose to investigate the
      coupling of sympathetic and somatomotor control because it is relevant to exercise training
      paradigms that are designed to improve somatomotor function or enhance physical fitness. Our
      approach will be to measure tendon tap reflexes, voluntary muscle activation, and blood flow
      of the knee (below injury) and elbow (above injury) before and after sympathetic stimuli
      consisting of cold pressor tests, mental math and an acute bout of exercise. These data will
      provide information about sympathetic control of blood flow during muscle activity.
      Plasticity of the sympatheticsomatomotor coupling will also be investigated by making
      measurements before and after a treadmill training exercise program. These experiments will
      enable us to address three aims. Aim 1 will be to characterize coupling of sympathetic and
      somatomotor systems below the level of spinal injury. This aim will examine spinal
      sympathetic and motor reflexes and their interactions. It will also examine how descending
      somatomotor coupling is disrupted by the spinal injury. In Aim 2, we will identify changes in
      the interactions of sympathetic and somatomotor systems above a spinal injury. Because of the
      injury and the changes that occur below the injury, the sympathetic-somatomotor coupling is
      also likely to be disrupted in the arm. Aim 3 will then demonstrate plasticity of
      sympathetic-somatomotor coupling after exercise training. Three different eight week exercise
      training programs will be tested including 1) treadmill training with exertion level matched
      to 70-80% of HRR 2)treadmill training with 30-40% HRR. The exercise training will be tested
      in a randomized crossover study design with one month between exercise training paradigms. We
      anticipate that there will be plasticity of sympathetic-somatomotor coupling and that the
      exercise training effects will normalize control of these systems. However, because of the
      injury, we anticipate that adaptations will differ from non-injured controls.

      This study has implications for exercise training in human SCI. The coupling of sympathetic
      and somatomotor systems is expected to depend on whether exercise targets the upper or lower
      body. The recovery of function requires both the improvement in the control of movement as
      well as in the regulation of blood flow to active muscle groups. In addition, this study is
      important for understanding the potential impact of treadmill exercise training on
      cardiovascular fitness, a topic of increasing interest in people with limitations to physical
      activity.
    

Intervention name(s): Treadmill Training
Intervention type(s): Other
Intervention description(s): Subjects will be randomized to a high intensity and low intensity group. The high intensity group will train at 70-80% of their HRR and the low intensity group will train at 30-40% of their HRR.
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: spinal cord injury; sympathetic nervous system; locomotor training; exercise