Abstract

Background: Sleep restriction impairs memory, while high intensity interval training (HIIT) improves cognition. Our objectives were to assess the feasibility of the study and to obtain preliminary results on the effects of an evening HIIT plus sleep restriction on declarative memory.
Methods: 88 healthy adults (24.6 ± 4.2yrs), completed a sleep diary 4 days prior to and during the experimental night. Participants were randomized into either restricted (~5-6 h/night) or average (~8-9 h/night) sleep opportunity, without (S5, S8 respectively) or with HIIT (HIITS5, HIITS8).
During the experimental night (at 7 p.m.), the HIIT groups completed a 15-min HIIT session while the non-exercise groups had an equivalent period of seated rest. This was followed by face-name recall tasks: encoding and immediate recall sessions the same evening, and a delayed recall session the following morning after an average or restricted sleep opportunity.
Results: Our remote-pilot study showed that all participants in the exercise groups completed the HIIT protocol safely. We found a significant interaction between HIIT and sleep conditions on delayed recall accuracy (p = 0.042, ηp2 = 0.049). Post hoc analysis showed significant differences for delayed recall accuracy between HIITS8 and S8 (81.64±14.64 vs. 93.95±10.71, p = 0.013, respectively) and between S5 and S8 (82.87 ± 16.66 vs. 93.95 ± 10.71, p = 0.023, respectively).
Conclusion: Acute evening HIIT hindered the positive effects of sleep on memory. Additionally, HIIT did not compensate for the memory impairment of sleep restriction.