Research Reports - Temperature and heart rate responses to exercise following mild traumatic brain injury
J Neurotrauma. 2012 Sep 25
Griesbach GS, Tio DL, Nair S, Hovda D
We have previously reported that mild fluid percussion injury (FPI) is associated
with a heightening of the hypothalamic-pituitary-adrenal axis response during the
first postinjury weeks. This is the same time period when rehabilitative exercise
has been strongly suggested to be ineffective. Here we explored if cardiac and
temperature autonomic function may also be compromised during this early
postinjury period. Following a FPI or sham injury, rats were exercised with
forced (fRW) or voluntary (vRW) running wheels on post-injury days 0-4 and 7-11.
Results indicated that overall activity levels were decreased and circadian
rhythm was affected after FPI. Autonomic disruptions became evident when exercise
was introduced and these disruptions were dependent on the characteristics of
exercise. Elevations in heart rate (HR) and core body temperature (CBT) were
observed as a response to vRW and fRW. FPI animals had more pronounced increases
in HR as a result of vRW. Likewise, increases in HR were observed with fRW in all
animals. A strong stress response has recently been associated with fRW exercise.
FPI rats exposed to fRW were more responsive to experimental manipulations and
had higher a CBT after the FRW session. The results suggest that subacute
exercise, particularly if linked to a strong stress response, may be
counterproductive. Here we show that cardiac and temperature autonomic function
are compromised during the subacute period following a mild TBI.