Findings from the journal Sleep Health00222-4/fulltext) shed light on the importance of good sleep for people working in operational settings such as the military. Using a protocol to simulate military operational stress, the study found that military personnel performed better on physical tasks when they reported less daytime sleepiness and exhibited lower slow wave activity during sleep.
Healthy sleep habits, like longer sleep duration and less daytime sleepiness, have been linked to better physical health. As the authors of the current study point out, such findings may have implications for military personnel who work in physically demanding roles and often experience a lack of sleep.
“I am interested in understanding the relationship between sleep patterns and daytime activities,” said corresponding author Fabio Ferrarelli, an associate professor of psychiatry at the University of Pittsburgh.”I think that this is especially relevant for military personnel because they are often facing challenging conditions and scenarios and having enough, good quality sleep is an unrecognized need that commonly affects their performance.”
In their study, the researchers explored whether certain sleep features might help military personnel maintain their physical performance during sleep loss. To do this, the researchers had a group of 45 active duty or reserve status military personnel partake in a simulated military operational stress (SMOS) protocol. Nine of the participants were female and 36 were male. The protocol was 5 days long and involved caloric restriction and sleep restriction/disruption while the subjects completed daily physical and tactical tasks.
“In this study we reproduced in the lab environment some of the challenges (i.e., food restriction, spending several days in a confined environment sharing the room with up to four people) that military personnel faces while deployed and seeing how sleep restriction (i.e., two consecutive nights when they are allowed to sleep only 4 hours) affect the personnel’s performance,” Ferrarelli explained.
During the protocol, the participants had opportunities for 8 hours of sleep on three of the days. On the two other days, sleep opportunities were restricted to two 2-hour sleeps per day. Sleep was monitored each night using polysomnography and participants also completed baseline questionnaires that assessed their habitual nighttime sleep disturbance and daytime sleepiness. Finally, a Tactical Mobility Test (TMT) assessed aspects of physical performance relevant to operations, such as water can carry and loaded/unloaded shuttle runs.
The results revealed that personnel with lower habitual daytime sleepiness and lower frontal slow wave activity demonstrated better physical performance at baseline and throughout the protocol. However, these sleep measures did not predict changes in their physical performance across the protocol.
The finding that higher daytime sleepiness was linked to worse physical performance is in line with previous research. The study authors say that sleepiness during the day might make people less motivated to engage in physical movement. This reduced physical activity may then contribute to lower physical performance ability.
The study highlights “that even the most fit individuals need to sleep well in order to perform well,” Ferrarelli told PsyPost. “In other words, if you are tired or sleepy because you have not been sleeping well at night, this is going to negatively impact your performance, even for task that rely mostly on your physical fitness during the daytime.”
Notably, any improvement in physical performance has the potential to significantly improve on the job success as well as the safety of personnel. Future research could test whether it is possible to improve physical performance among operational populations through behavioral interventions that target daytime sleepiness.
According to the study authors, the finding that lower slow wave activity was associated with better physical performance seems to contradict previous findings — higher slow wave activity is said to represent a restorative sleep stage and to be associated with better fitness. An explanation for this inconsistency could be that higher slow wave activity may reflect chronic, insufficient sleep. This habitual lack of sleep could then reduce motivation to engage in physical activity and hinder physical performance.
“Contrary to what we expected, we found that less deep sleep, as reflected by less slow wave activity, was associated with better physical readiness,” Ferrarelli explained. “Usually, more deep sleep/slow wave activity is thought to reflect more restful sleep and tends to predict a better daytime performance. However, in this case we think that individuals who are more used to sleep less deeply are more resilient to sleep restriction and therefore perform better.”
The findings show that both self-report (daytime sleepiness) and objective (slow wave activity) markers of sleep health are associated with physical performance among military personnel working on tactical tasks. This points to the crucial role of good sleep for operational performance.
“The main caveat is that the study was conducted in the sleep laboratory and therefore we can’t say that the same would happen in a different environments (i.e., when deployed, at home, etc.),” Ferrarelli said. “Therefore, future studies should replicate our findings in these environments.”
The study, “Less daytime sleepiness and slow wave activity during sleep predict better physical readiness in military personnel”, was authored by Alice D. LaGoy, William R. Conkright, Felix Proessl, Aaron M. Sinnott, Meaghan E. Beckner, Leslie Jabloner, Shawn R. Eagle, Nicole M. Sekel, Peter G. Roma, Michael N. Dretsch, Shawn D. Flanagan, Qi Mi, Bradley C. Nindl, Anne Germain, Christopher Connaboy, and Fabio Ferrarelli.
