Multimodal cortical and subcortical exercise compared with treadmill training for spinal cord injury

Abstract

Background and purpose: Spared fibers after spinal cord injury (SCI) tend to consist predominantly of subcortical circuits that are not under volitional (cortical) control. We aim to improve function after SCI by using targeted physical exercises designed to simultaneously stimulate cortical and spared subcortical neural circuits.

Methods: Participants with chronic motor-incomplete SCI enrolled in a single-center, prospective interventional crossover study. Participants underwent 48 sessions each of weight-supported robotic-assisted treadmill training and a novel combination of balance and fine hand exercises, in randomized order, with a 6-week washout period. Change post-intervention was measured for lower extremity motor score, soleus H-reflex facilitation; seated balance function; ambulation; spasticity; and pain.

Results: Only 9 of 21 enrolled participants completed both interventions. Thirteen participants completed at least one intervention. Although there were no statistically significant differences, multimodal training tended to increase short-interval H-reflex facilitation, whereas treadmill training tended to improve dynamic seated balance.

Discussion: The low number of participants who completed both phases of the crossover intervention limited the power of this study to detect significant effects. Other potential explanations for the lack of significant differences with multimodal training could include insufficient engagement of lower extremity motor cortex using skilled upper extremity exercises; and lack of skill transfer from upright postural stability during multimodal training to seated dynamic balance during testing. To our knowledge, this is the first published study to report seated posturography outcomes after rehabilitation interventions in individuals with SCI.

Conclusion: In participants with chronic incomplete SCI, a novel mix of multimodal exercises incorporating balance exercises with skilled upper extremity exercises showed no benefit compared to an active control program of body weight-supported treadmill training. To improve participant retention in long-term rehabilitation studies, subsequent trials would benefit from a parallel group rather than crossover study design.

Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1. CONSORT flow diagram.

Fig 2. Multimodal (MM) exercise paradigm.

MM involved balance exercises plus simultaneous fractionated hand exercises targeted at the corticospinal tract. Participants’ feet were placed on either the flat or convex side of a semi-spherical balance platform (Bosu™). To increase challenge, participants were intermittently asked to perform tandem stance (A), or study personnel applied external perturbations. During balance exercise, participants performed a variety arm or hand manipulations that involve precision or power movements, such as placing pegs into a grooved pegboard, maintaining a ping-pong ball on a small handheld plastic dish (A); and other tasks. Tasks were varied every one to three minutes to maintain participant interest. Overhead partial body weight support was provided at all times.

Fig 3. Change in Lower Extremity Motor Score (LEMS).

Pre- and post-intervention data shown for each subject. A, Multimodal; B, Treadmill. Red lines indicate subjects with baseline ASIA Impairment Scale (AIS) Grade D. Green lines indicate subjects with baseline AIS Grade C. Blue line indicates subject with baseline AIS Grade B. Black line indicates subject with baseline AIS Grade A (and significant zone of partial preservation).

Fig 4. Change in short-interval (0–20 ms) soleus H-reflex facilitation by subthreshold transcranial magnetic stimulation.

Pre- and post-intervention data shown for each subject. A, Multimodal; B, Treadmill. Red lines indicate subjects with baseline ASIA Impairment Scale (AIS) Grade D. Green lines indicate subjects with baseline AIS Grade C. Blue line indicates subject with baseline AIS Grade B. Black line indicates subject with baseline AIS Grade A (and significant zone of partial preservation).