Differential Effects of Low versus High Amounts of Weight Supported Treadmill Training in Spinally Transected Rats

Abstract

Intensive weight-supported treadmill training (WSTT)improves locomotor function following spinal cord injury. Because of a number of factors, undergoing intensive sessions of training may not be feasible. Whether reduced amounts of training are sufficient to enhance spinal plasticity to a level that is necessary for improving function is not known. The focus of the present study was to assess differences in recovery of locomotor function and spinal plasticity as a function of the amount of steps taken during WSTT in a rodent model of spinal cord injury. Rats were spinally transected at 5 days of age. When they reached 28 days of age, a robotic system was used to implement a weight-supported treadmill training program of either 100 or 1000 steps/training session daily for 4 weeks. Antibodies for brain-derived neurotrophic factor (BDNF), TrkB, and the pre-synaptic marker, synaptophysin, were used to examine the expression of these proteins in the ventral horn of the lumbar spinal cord. Rats that received weight-supported treadmill training performed better stepping relative to untrained rats, but only the rats that received 1000 steps/training session recovered locomotor function that resembled normal patterns. Only the rats that received 1000 steps/training session recovered normal levels of synaptophysin immunoreactivity around motor neurons. Weight-supported treadmill training consisting of either 100 or 1000 steps/ training session increased BDNF immunoreactivity in the ventral horn of the lumbar spinal cord. TrkB expression in the ventral horn was not affected by spinal cord transection or weight-supported treadmill training. Synaptophysin expression, but not BDNF or TrkB expression was correlated with the recovery of stepping function. These findings suggested that a large amount of weight-supported treadmill training was necessary for restoring synaptic connections to motor neurons within the locomotor generating circuitry. Although a large amount of training was best for recovery, small amounts of training were associated with incremental gains in function and increased BDNF levels.

Locomotor training improves reciprocal and nonreciprocal inhibitory control of soleus motoneurons in human spinal cord injury

“…2F) and the weak Ib excitation during the stance phase in AIS C and D (Fig. 6, C and F) may depend on the number of training sessions, the number of steps per session (de Leon et al 2011), or even the BWS since loading can affect the net EMG output (Dietz et al 2002). The BWS during training was adjusted separately for each participant based on his/her ability to step without knee buckling or toe dragging, and thus quantification of BWS effects is not possible.…”

Delayed Intervention with Intermittent Hypoxia and Task Training Improves Forelimb Function in a Rat Model of Cervical Spinal Injury

“…Treadmill training in rodents after SCI is commonly used to investigate the role of repetitive movement training (e.g., spinal learning) with moderate to severe paralysis, or to investigate the contribution of physical exercise on recovery in animals able to walk with weight-supported steps. 16,19,[28][29][30][31][32][33] In the lesion model studied here, 1 week of daily treadmill training beginning 4 weeks post-injury did not significantly reduce footslip errors on the ladder task, nor did AIH administered at the same time as treadmill training improve ladder performance post-treatment (Fig. 5).…”

Robot-Applied Resistance Augments the Effects of Body Weight–Supported Treadmill Training on Stepping and Synaptic Plasticity in a Rodent Model of Spinal Cord Injury

“…These training parameters were based on our previous studies that showed positive effects of 4–6 weeks of training in SCI rats. 10,11,20–23 The robotic device (Rodent Robot 3000, Robomedica Inc., Irvine, California) consisted of a motorized treadmill and a body weight support (BWS) apparatus for control over hindlimb weight bearing (Fig. 1A).…”

“…10,11,20–23 All rats were tested for their ability to step without any resistive forces and at a treadmill speed of 10 cm·s −1 . The duration of testing was typically 1 minute as a precaution against any training effects, especially in the UT group.…”