Intensity Monitoring for Adaptive Aerobics

Physiological effects of disabilities can affect the ability of the athlete to self-monitor the intensity level of his/her exercise. Several effects of the disability, depending on the nature of the disability, can actually change the numerical basis of the intensity charts that we have all learned to use, that we probably have posted on the walls of our aerobics studio. Group exercise leaders need to be aware of the constraints that physical disabilities impose on monitoring exercise intensity and you need to be able to inform the athletes in your class of the proper way to interpret the intensity monitoring that you use.

Constraints in Monitoring Method

Athletes may not have the tactile sense to properly check their own heart rate; if their disability is a spinal cord injury above the upper thoracic area, their sense of touch may be impaired. This means that the instructor or another athlete or a second instructor must check the athlete's pulse at the proper time in the class. For those of you who work at facilities that prohibit you actually touching the athletes, this may cause administrative problems; I would suggest that you discuss this with your immediate superior.

Some athletes in wheelchairs also wear gloves to protect their hands while pushing their chair and these could impair checking a pulse at the radial artery, which is the recommended heartrate monitoring site. I would suggest in this case and for those athletes who can't pick up an radial pulse, that they check their heart rate at the brachial artery, since the carotid artery location has started to be discouraged as a pulse check site.

Factors Affecting Heart Rate as Exercise Intensity Indicator

While heart rate monitoring has problems in application for some disabled athletes, it is still the most widely used technique for monitoring exercise intensity in all populations, and it should be included in the programming for adaptive aerobics classes, as well as for disabled athletes within mainstream studio aerobics. Several limiting factors on the heart rate being used with standard ranges must be acknowledged; the disabled athlete may have a disability that limits the trainable, usable muscle mass, the disabled athlete may have impaired cardiovascular or autonomic function, the disabled athlete's anaerobic threshold may differ from an athlete without disability and the athlete may be influenced by drugs that alter physiologic responses to exercise.

Limited Trainable Mass

Many of the physical disabilities we described previously prevent or partially limit the use of a large part of the skeletal muscle mass during exercise due to impaired or absent motor control. Spinal cord injury, Multiple Sclerosis, and head injury are three examples of this absence of control. Cerebral Palsy and head injury limit or impair movement coordination of large muscles. In the case of amputees, the muscle mass is absent. Stroke, MS and polio may cause paralysis that again limits the amount of muscle that can be used in exercise.

Impaired Cardiovascular or Autonomic Function

Spinal cord injury above T-5 will limit the maximal heart rate to between 110 and 130 beats per minute, which in most people using standard heart rate monitoring methods or charts would be the low end of the "fat-burning" aerobic range.

Anaerobic Threshold Difference

Again, due to reduced muscle mass, the threshold of lactic acid production may be reduced; more lactic acid is produced for exercise using a smaller muscle mass. This causes an increase in heart rate, blood pressure and breathing rate for an absolute work load. Exercise with spastic muscle contraction can also induce greater increases in lactic acid accumulation, with corresponding increases in blood pressure and heart rate.

Medicinal (Pharmacological) Agents

As with the general population, disabled athletes may be taking prescription or over the counter drugs that affect the level of intensity of their aerobics performance. Not being a pharmacist or an M.D., I am not qualified to list what drugs produce what effects. For instance, you don't have to be disabled to have a prescription for beta blockers, which can effectively limit exercise heart rate to well under the traditional "fat burning" range.