The Effects of Acute Exercise and a Nap on Heart Rate Variability and
Memory in Young Sedentary Adults
Recent evidence suggests that the autonomic nervous system can
contribute to memory consolidation during sleep. Whether fluctuations in
cardiac autonomic activity during sleep following physical exercise
contribute to the process of memory consolidation has not been studied.
We assessed the effects of a non-rapid eye movement (NREM) nap following
acute exercise on cardiac autonomic regulation assessed with heart rate
variability (HRV) to examine if HRV influences memory processes.
Fifty-six (59% female) healthy young adults (23.14 ± 3.74 years) were
randomly allocated to either the exercise plus nap (ExNap, n = 27) or
nap alone (NoExNap, n = 29) groups. The ExNap group performed a
40-minute moderate-intensity cycling, while the NoExNap group was
sedentary prior to learning 45 neutral pictures for a later test.
Subsequently, participants underwent a 60-minute NREM nap while
measuring EKG, followed by a visual recognition test. Our results
indicated that heart rate did not significantly differ between the
groups (p = 0.302); whereas vagally-mediated HRV indices were lower in
the ExNap group compared to the NoExNap group (p < 0.05).
There were no significant differences in sleep variables (p
> 0.05). Recognition accuracy was significantly higher in
the ExNap group than in the NoExNap group (p = 0.027). In addition, the
recognition accuracy of the ExNap group was negatively associated with
vagally-mediated HRV (p < 0.05). Pre-nap acute exercise
attenuated parasympathetic activity and appears to alter the
relationship between memory and cardiac autonomic activity, suggesting
that post-exercise memory enhancement may be based on other mechanisms.