Effects of 36 Hours of Sleep Deprivation on Military-related Tasks: Can Ammonium Inhalants Maintain Performance?

Change in simple reaction time from baseline

时间窗: We were following changes in 5 identical testing sessions during 36 hours of total sleep deprivation (after 0-baseline, 12, 24, and 36 hours), and after 8 hours of recovery sleep.

A simple reaction time test was used to assess the speed of responses to visual stimuli. The evaluation of reaction time was performed using the PEBL Version 2.0 software. The test consists of instantaneous responses to a visual stimulus by pressing a spacebar key on a laptop's keyboard as quickly as possible when a visual stimulus appears. In the test, 50 trials of stimuli were presented with an interstimulus interval that randomly varied between 250 ms and 2500 ms. Each participant completed four tests (each time two, either with AI or CON, in randomized order) with 2 minutes of inter-test rest. The simple reaction time data obtained were inspected according to pre-determined criteria, which excluded trial executions that were deemed incorrect due to a reaction time shorter than 150 ms or longer than 3000 ms. The mean reaction time (measured in milliseconds) and the number of incorrect trial executions were used as the variables in the subsequent statistical analysis.

Change in Epworth sleepiness scale from baseline

时间窗: We were following changes in 5 identical testing sessions during 36 hours of total sleep deprivation (after 0-baseline, 12, 24, and 36 hours), and after 8 hours of recovery sleep.

We used Epworth Sleepiness Scale (ESS) translated into Czech. It is a self-administered eight-item questionnaire and takes two to three minutes to complete. The questionnaire presents daily lifestyle activities (i.e. reading, watching TV etc.) and participants rate their current self-perceived likelihood of dozing off in each situation, from: "would never doze" (0) to "high chance of dozing". The ESS provides a cumulative score between 0 and 24, with higher numbers indicating greater sleepiness.

Change in countermovement jump height from baseline

时间窗: We were following changes in 5 identical testing sessions during 36 hours of total sleep deprivation (after 0-baseline, 12, 24, and 36 hours), and after 8 hours of recovery sleep.

We used unloaded countermovement jump (CMJ), one of the most common and straightforward strategies to monitor short-term neuromuscular performance in tactical populations. Each CMJ session included 2 sets (AI and CON in a randomized order) of 3 maximal effort CMJs with 2 min of inter-set standing rest. The researcher verbally instructed and encouraged the participants to jump as high as possible on each jump. All CMJs were performed with wooden dowel (\~ 0.5 kg) as a mock barbell placed across the participant's upper back mimicking a regular back squat. A linear position transducer (GymAware Power Tool; Kinetic Performance Technologies, Canberra, Australia) was attached to both sides of a dowel to measure the performance. The depth of the CMJ depth was self-selected. Participants wore the same sports t-shirts, shorts and shoes during each test period. The mean of the 3 jump heights (cm) was calculated for each condition at each test session.

Change in heart rate from baseline

时间窗: We were following changes in 5 identical testing sessions during 36 hours of total sleep deprivation (after 0-baseline, 12, 24, and 36 hours), and after 8 hours of recovery sleep.

All participants wore a chest strap heart rate monitor (Polar Electro Inc., Model H10, Lake Success, NY, USA) during the shooting protocol. Baseline heart rate data were derived as a mean of heart rate from 2 minutes immediately preceding the start of the shooting trial. Heart rate (bpm) was then continuously monitored during all sessions of shooting protocol. After baseline testing, heart rate data were averaged in 15 seconds bins (0-15, 15-30, 30-45, 45-60) for one minute immediately following the AI and CON trials. The mean of these bins from each trial was used in subsequent analysis.

Change in rating of perceived exertion from baseline

时间窗: We were following changes in 5 identical testing sessions during 36 hours of total sleep deprivation (after 0-baseline, 12, 24, and 36 hours), and after 8 hours of recovery sleep.

The rating of perceived exertion (RPE) was recorded during the CMJ testing using a CR-10 scale to evaluate RPE scores after each set of CMJ. RPE is a frequently used marker of exercise intensity typically used for monitoring during exercise tests to complement other intensity measures.

Change in handgun shooting accuracy from baseline

时间窗: Performed in 5 identical testing sessions during 36 hours of total sleep deprivation (after 0, 12, 24, and 36 hours), and after 8 hours of recovery sleep.

A laser-based simulator system with an infrared laser handgun was used to assess handgun shooting accuracy. All trials were performed in the standardized isosceles high-ready stance position. For this study, a real-weight mock-up of the Czech military standard issue Glock 17/22 handgun was used (all participants were familiar with the handgun from their active service). Participants wore over-ear headphones during all testing procedures to hear the software command to start shooting and the simulated shooting blasts when pulling the trigger. A 20 cm circular target was placed on a blank wall 4 meters in front of the participants to simulate a standard-issue 50 cm target 10 meters away for the laser-based handgun shooting protocols. For the testing, participants fired 10 shots, aiming to hit the middle of the circular target (a bullseye hit was worth 10 points, and 1 point was deducted for every 1 cm region away from the bullseye, resulting in a maximum score of 100 points).

Change in rifle disassembling and reassembling from baseline

时间窗: We were following changes in 5 identical testing sessions during 36 hours of total sleep deprivation (after 0-baseline, 12, 24, and 36 hours), and after 8 hours of recovery sleep.

The protocol for disassembling and reassembling a military-standard issue assault rifle was selected to assess changes in manual dexterity as it is representative tasks that soldiers may encounter in field operations. During the protocol, participants were tasked to disassemble and reassemble a rifle consisting of 8 parts as fast as possible. Prior to the task's onset, standing participants were instructed to place their hands behind their backs and wait for the researcher's "start" command, after which they attempted to disassemble the rifle as quickly as possible. After a two-minute break, during which participants organized the rifle parts on a table, they then proceeded to reassemble the rifle under the same instruction, and the time was recorded. During the reassembling, the final step was conducting a successful "rifle function check". The time for completion of the task was measured using a handheld stopwatch and recorded on a digital camera for possible corrections.