Changes in core body temperature during exercise in the morning or evening and their impact upon the circadian rhythm in core body temperature in SCI

Thermoregulation is importantly impacted in individuals with spinal cord injury
(SCI). When exposed to a thermophysiological stimulus, such as extreme heat or
cold, people with a SCI adapt differently than able-bodied people, eventually
resulting in a larger increase or decrease in the core body temperature. This
thermoregulatory dysfunction is primarily due to a decrease or even a loss of
neural activity from the regions below the level of the lesion to the
thermoregulatory centre (21) as well as a disruption of both vasomotor control
and sweating capacity below the level of lesion (12). Consequently, paraplegics
and tetraplegics show a higher risk to heat illness when exposed to heat or
while exercising (2, 9), but also have problems with their thermoregulatory
functions in daily living leading to a clinically frequently reported *cold
legs*. Currently, little is known about the circadian rhythm of the core body
temperature in SCI, but also the responses and recovery of the core body
temperature to exercise are unknown. In addition, due to possible fluctuations
of the temperature throughout the day (circadian rhythms), the exercise-induced
responses of the core body temperature may vary dependent on the timing of
exercise.

Our main aim is to describe the 24-h circadian rhythm of skin and core body
temperature in people with SCI and the change in skin and core body temperature
during and after an exercise bout in SCI and controls. Secondly, we wish to
examine differences in the exercise-induced changes in skin and core body
temperature in SCI and controls when exercise is performed at different moments
of the day (8 am and 8 pm).

Observational study

The intake of this telemetry pill is non-invasive and not dangerous as it can
be swallowed similarly as any medication pill. Our department has extensive
experience with this telemetry system and has been used in previous study
protocols which were approved by the ethics committee (CMO-nr 2007/147,
2007/262). An ingestion of this pill will also cause no harm to the body and
its function due to the sophisticated elaboration of protection to its
surrounding. The pill has been proved to be reliable and valid for measuring
core body temperature at rest and during exercise, and is now being used and
registered at the *Food and Drug Administration (FDA)* for 19 years. The pill
telemetry system has also been used in SCI subjects in previous studies without
any negative side effect. Important advantages of this system is that it is
non-invasive, valid, does not have the sanitary problems when using different
techniques (such as rectal probes) and can be used without noticing by the
subject. From the >35,000 pills that have been distributed, no negative
incidents have been reported. In addition, the Department of Physiology has
experience with >200 subjects that have used the pill for 1 or multiple day
core body temperature measurements. So far, we have not noticed any negative
impact of using the pill in any of the participants.

The other techniques used in this study (exercise tests, activity monitor, skin
temperature, heart rate recording) are all techniques that have been used for
several years at the Department of Physiology. None of these measuring
techniques are invasive, painful or possible dangerous for the subject. Using
these techniques will also not influence their daily living.