The effect of load and velocity on muscle activation and cutaneous reflexes during rhythmic human arm cycling

Stroke is one of the leading causes of disability in older adults. After stroke there may be deficits to movement control which typically are expressed as either too much activity in a muscle (spasticity) or too little activity in a muscle (low tone). These impairments interfere with normal movements involved in daily physical activities such as walking or reaching. Present rehabilitation programs include treadmill training with body weight support, with the focus mainly on the leg muscles. The speed and amount of body weight support required to maximize the rehabilitative benefits of treadmill training is not fully understood. It has been shown that the movement of the arms during walking can influence the walking pattern. Research has also shown that rhythmic movement such as walking is to a large degree controlled by neural circuits in the spinal cord called central pattern generators (CPG). More recently, it has been suggested that benefits to leg motor function result from retraining the CPG for the arms as well as the legs. This suggests that recovery of arm muscle activity may be important for the recovery of a normal walking pattern, and of leg muscle function as well as arm function. Sandra Hundza is exploring the most effective levels of speed and load to be used in an arm training protocol. By using harmless electrical stimulation of a nerve in the hand, she is evaluating muscle activity and reflexes elicited during rhythmic arm cycling movement. Results from Sandra’s research will determine what speed and load will best stimulate the spinal circuitry, thereby offering the best training protocol for arm cycling therapy. Her results will also have application to speed and weight bearing support for treadmill training protocols in general and help to better understand how rhythmic movement of the limbs are controlled.