By Jonathon Stavres MS, ACSM-EP-C
Paraplegia, characterized by paralysis of the lower half of the body, has detrimental effects on the central and peripheral circulation. This causes the heart rate and blood flow responses to exercise to be very different from a non-injured condition. One of these changes is an elevated heart rate during exercise due to an inability of vasoconstriction in the injured half of the body.
In a healthy limb with neural innervation there is an increase in sympathetic outflow to the vascular smooth muscle with increasing exercise intensity, which causes global vasoconstriction.
This vasoconstriction allows blood flow to be shunted away from the inactive muscle (i.e. the legs during arm-ergometry) and directed to the active muscle during exercise.
When vasoconstriction is absent, the heart has to pump at a higher frequency in order to continue to supply adequate blood flow to the active muscle tissue.
This is why some paraplegic athletes have resorted to “boosting,” a technique banned by the International Paralympic Committee (IPC). Boosting occurs when an athlete provokes a noxious stimulus (such as avoiding draining their bladder to cause bladder distension) that causes a reflex sympathetic vasoconstriction below the level of the injury.
Since there is no neural innervation from the brain to the lower body, there is no compensatory vasodilation of the lower body. Altogether, this physiological process is referred to as Autonomic Dysreflexia. Athletes will take this risk to increase blood flow to the active tissue with a lesser demand on the heart.
A common form of exercise training for individuals with paraplegia is functional electrical stimulation-FES for short. FES is performed by placing externally innervated electrodes over the surface of the paralyzed muscles to induce involuntary muscle contractions.
This assisted activity is often used in aided walking and more commonly in cycling. While the exercise stimulus is quite different from that in a healthy-bodied individual, there is still evidence that FES training can elicit significant physiological improvements in paraplegics.
A recent study by Kuhn et.al (2014) examined the effects of a four- week exercise program, meeting twice per week for FES training program in thirty participants with varying degrees of spinal cord injury. Following the four- week exercise program, researchers found improvements in muscle spasticity during hip- abduction and adduction, knee flexion and extension, and foot dorsiflexion. Results also indicated increases in the cross-sectional area of the rectus femoris muscle.
This data indicates that FES training can significantly improve the muscle function of the paralyzed lower limb in paraplegics.
However, this study did not discuss changes in vascular function. Other studies have begun to identify cardiovascular benefits of passive movement of the lower limbs and examine the role of nitric oxide in vascular function of paralyzed limbs. This area of research is still in its infancy.
*For more examples of other variations/exercises for paraplegics look under Multimedia-VDF Exercise Tips
**Consult with a physician and/or medical healthcare provider before starting any exercise regimen
Article’s Resources
Kuhn, D., Leichtfried, V., & Schobersberger, W. (2014). Four weeks of functional electrical stimulated cycling after spinal cord injury: a clinical cohort study. Int J Rehabil Res, 37(3), 243-250. doi: 10.1097/mrr.0000000000000062