Exercise therapy and recovery after SCI: evidence that shows early intervention improves recovery of function

Abstract

Study design: This was designed as an experimental study.

Objectives: Locomotor training is one of the most effective strategies currently available for facilitating recovery of function after an incomplete spinal cord injury (SCI). However, there is still controversy regarding the timing of treatment initiation for maximal recovery benefits. To address this issue, the present study compares the effects of exercise initiated in the acute and secondary phase of SCI.

Setting: Texas A&M University, College Station, TX, USA.

Methods: Rats received a moderate spinal contusion injury and began an exercise program 1 (D1-EX) or 8 days (D8-EX) later. They were individually placed into transparent exercise balls for 60 min per day, for 14 consecutive days. Control rats were placed in exercise balls that were rendered immobile. Motor and sensory recovery was assessed for 28 days after injury.

Results: The D1-EX rats recovered significantly more locomotor function (BBB scale) than controls and D8-EX rats. Moreover, analyses revealed that rats in the D8-EX group had significantly lower tactile reactivity thresholds compared with control and D1-EX rats, and symptoms of allodynia were not reversed by exercise. Rats in the D8-EX group also had significantly larger areas of damage across spinal sections caudal to the injury center compared with the D1-EX group.

Conclusion: These results indicate that implementing an exercise regimen in the acute phase of SCI maximizes the potential for recovery of function.

Figure 1

There was a significant effect of exercise on recovery of locomotor function across the 28-day assessment period. Subjects in the D1-EX group recovered significantly more locomotor function than those in the no-EX and D8-EX groups (P<0.05). Locomotor scores reached a plateau for all groups by 16 days, after injury, which suggests that training in the exercise balls did not extend the period of spontaneous recovery, often observed after SCI.

Figure 2

There was no effect of exercise condition on the latency to tail flick, with the radiant heat stimulus at 8 or 28 days after injury (a). However, analysis of hindpaw tactile reactivity revealed a main effect of condition after injury (b). The average change reactivity (± s.e.m.) with von Frey stimulation is depicted for days 1, 8, and 28. Subjects in the D8-EX group developed significantly lower tactile reactivity thresholds than both the control and D1-EX subjects by the time of assessment at day 8. This allodynic response was not reversed by exercise. **P<0.05.

Figure 3

This figure depicts the effects of exercise on lesion indices and tissue sparing in spinal sections that were 600–1800 μm caudal to the lesion epicenter. Although relative lesion (damage + missing) areas did not differ across groups (a), subjects in the D8-EX group had significantly larger areas of damage across spinal sections that were 600–1800 μm caudal to the injury center compared with the D1-EX subjects (b). Independent analyses did not reveal significant differences among the groups for missing (c), area of gray (d) and white tissue indices (e). However, although not significant, subjects in the D1-EX condition had less missing and lesioned tissue compared with the no-EX and D8-EX groups (c and a, respectively), and had more gray and white matter remaining caudal to the lesion center (d and e, respectively).