Which of the following disabilities represents an individual that would be unable to achieve a maximal heart rate due to physiological characteristics of his or her disability?
a. Tetraplegia.
b. Amputation.
c. Post-poliomyelitis.
d. Chronic fatigue syndrome.
The correct answer and explanation is:
The correct answer is a. Tetraplegia.
Tetraplegia, also known as quadriplegia, is a condition characterized by the paralysis of all four limbs, often caused by spinal cord injury (SCI) at or above the cervical level. Individuals with tetraplegia may face several limitations in their ability to engage in physical activities, particularly those that involve the cardiovascular system.
Maximal heart rate (MHR) is generally defined as the highest heart rate a person can achieve during intense physical exertion. It is usually estimated with the formula 220 minus age. For individuals with tetraplegia, the physiological characteristics of the condition significantly impact the body’s ability to achieve its maximal heart rate.
The key issue in tetraplegia is that the spinal cord injury disrupts the sympathetic nervous system, which is responsible for the body’s “fight or flight” responses, including increasing heart rate during exercise. The injury impairs communication between the brain and the autonomic nervous system, which controls heart rate and other involuntary functions. Consequently, the heart rate response to physical exertion may be blunted or reduced. Without proper communication, the heart cannot reach the typical levels of exertion seen in individuals with intact spinal function.
Additionally, individuals with tetraplegia may experience diminished muscle mass and strength, further hindering the cardiovascular response to exercise. The lack of muscular activity in the lower body means that the heart’s workload is lessened, which means it does not need to pump as forcefully or as fast as in able-bodied individuals. This can result in a significantly lower maximal heart rate during exercise.
For individuals with other conditions listed (amputation, post-poliomyelitis, and chronic fatigue syndrome), while they may have limitations or challenges in achieving maximal heart rates, they generally still retain some sympathetic nervous system function and may achieve higher levels of exertion compared to those with tetraplegia.