Abstract Roberts, BM, Mantua, J, Naylor, JA, and Ritland, BM. A narrative review of performance and health research in US army rangers. J Strength Cond Res 37(5): 1157–1161, 2023—The 75th Ranger Regiment (75RR) is an elite airborne infantry unit that is prepared to deploy on short notice and is resourced to maintain exceptional proficiency and readiness through prolonged deployments. Soldiers must be airborne qualified and pass a number of physical and psychological tests during training to become a member of 75RR. Rangers must maintain a level of physical performance comparable to high-level athletes while also handling operational stressors that include a negative-energy balance, high-energy expenditure, sleep restriction, and completing missions in extreme environments, all of which increase their chance of illness or infection. There are also situations of heighted injury risk, such as parachuting and repelling, which are routinely required in combat operations. Thus far, only one screening tool to assess injury risk has been developed. There are also physical training programs to enhance performance for Rangers in 75RR. This narrative review aims to evaluate the body of literature surrounding performance and health-related research in US Army Rangers to understand how Rangers are impacted during training or operations, to inform future training recommendations, and to identify areas of future research that are warranted and could potentially optimize the health and performance of Rangers during future training or operation events.

INTRODUCTION:Musculoskeletal injuries and insufficient sleep are common among U.S. Army Rangers. There has been limited research into whether indices of sleep differ between injured and uninjured Rangers. The purpose of this study was to investigate the association between self-reported sleep and musculoskeletal injury in Rangers. MATERIALS AND METHODS:A total of 82 Army Rangers (male, 25.4 ± 4.0 years) were asked if they currently have any musculoskeletal injuries; completed the Pittsburgh Sleep Quality Index (PSQI), the Insomnia Severity Index (ISI), and the Stanford Sleepiness Scale; and were asked about their average sleep quality/sleep duration over the preceding week. Rangers were then dichotomized into groups, one that reported a current musculoskeletal injury and another that did not. RESULTS:The reported musculoskeletal injury prevalence was 15.9% (n = 13). The Rangers that reported an injury, compared to those that did not, had a significantly higher Global PSQI score (6.7 ± 3.7 versus 4.5 ± 2.7, P = .012) and ISI score (10.9 ± 3.7 versus 7.2 ± 4.1, P = .003), both indicative of poorer sleep. The group reporting an injury rated their average sleep quality over the preceding week significantly lower compared to those that did not report an injury (50.8 ± 17.5 versus 68.9 ± 18.3, P = .001). There was no significant group difference in the average nightly sleep duration (6.1 ± 1.0 hours versus 6.5 ± 0.9 hours, P = .099). CONCLUSION:In this cohort of male Army Rangers, In this cohort of male Army Rangers, those with a musculoskeletal injury reported poorer sleep quality than uninjured Rangers. Sleep duration was not associated with reported injuries; however, both the injured group and uninjured group averaged less than the recommended amounts of sleep. Further investigation into the relationship between musculoskeletal injury and sleep in military personnel is warranted.

There are replicable inter-individual differences in cognitive responsivity to sleep loss. Genetic allele variations have been linked with behavioral differences in cognitive performance under these conditions, yet less burdensome tests or screeners are not available. This study tested whether a survey can classify U.S. Army Soldiers as cognitively vulnerable or resilient to sleep loss and whether Soldiers in these differentiated groups have the expected allele variants. Six genetic targets were sequenced from 75 Soldiers. Cognition was tested after a night of total sleep deprivation during a military exercise. The Iowa Resilience to Sleeplessness Test (iREST) was administered. A Wilcoxon Rank Sum test showed the iREST score of 2.5/5 differentiated groups behaviorally on all cognitive tests. Chi-squared tests showed that for the Catechol-O-Methyltransferase (COMT) gene, 82% of behaviorally vulnerable soldiers had alleles linked with vulnerability, compared with 41% of behaviorally genetic soldiers. If these findings are replicated, the iREST could be used to help military leaders make decisions about personnel placement when sleep loss is unavoidable.

PURPOSE: Musculoskeletal injuries, pain, and insufficient sleep are common health issues that affect U.S. Army Soldiers. There has been limited research into whether indices of sleep and pain differ between injured and uninjured Soldiers. The purpose of this study was to investigate whether injured Soldiers had worse sleep and pain indices compared to uninjured Soldiers. METHODS: Soldiers (n = 308; 26.8 ± 6.5 y, 82% male) from the 2nd Infantry Division, Joint Base Lewis-McChord, WA and 101st Airborne Division, Fort Campbell, KY completed the Pittsburgh Sleep Quality Index (PSQI), Epworth Sleepiness Scale (ESS), and questionnaires about current musculoskeletal injuries and pain levels (0 = no pain to 10 = worst imaginable pain). Participants were then dichotomized into groups, one that reported a current musculoskeletal injury and another that did not. Differences in sleep and pain between injured and uninjured participants were determined using independent sample t-tests. Age and time in service were different between groups, therefore, analyses of covariance were also performed to determine if age and time in service affected sleep and pain across groups. RESULTS: The prevalence of self-reported musculoskeletal injuries was 37.7% (n = 116). Injured participants had higher global PSQI scores (9.0 ± 4.1 vs 6.4 ± 3.4, p < 0.001), including each of the seven PSQI components (all p < 0.05), and reported sleeping less per night than uninjured participants (5.7 ± 1.3 h vs 6.1 ± 1.2 h, p < 0.001). Injured participants also reported greater levels of pain (3.7 ± 2.5 vs 1.3 ± 1.9, p < 0.001), were older (28.5 ± 7.4 y vs 25.8 ± 5.7 y, p = 0.001), and in the service longer (6.3 ± 6.3 y vs 4.6 ± 4.7 y, p = 0.013) than uninjured participants. There were no group differences in mean ESS scores (8.8 ± 5.6 vs 7.9 ± 4.8, p = 0.136). Co-varying for age and time in service did not change the results. CONCLUSION: These data demonstrate that active duty Army Soldiers that report a musculoskeletal injury, regardless of age and time in service, report poorer sleep quality, shorter sleep durations, and greater levels of pain than uninjured Soldiers. The views expressed herein are those of the authors and do not reflect the official policy of the Department of Army, Department of Defense, or the U.S. Government.

Abstract Introduction Sleep loss that is inherent to military operations can lead to cognitive errors and potential mission failure. Single Nucleotide Polymorphisms (SNPs) allele variations of several genes (COMT, ADORA2A, TNFa, CLOCK, DAT1) have been linked with inter-individual cognitive resilience to sleep loss through various mechanisms. U.S. Army Soldiers with resilience-related alleles may be better-suited to perform cognitively-arduous duties under conditions of sleep loss than those without these alleles. However, military-wide genetic screening is costly, arduous, and infeasible. This study tested whether a brief survey of subjective resilience to sleep loss (1) can demarcate soldiers with and without resilience-related alleles, and, if so, (2) can predict cognitive performance under conditions of sleep loss. Methods Six SNPs from the aforementioned genes were sequenced from 75 male U.S. Army special operations Soldiers (age 25.7±4.1). Psychomotor vigilance, response inhibition, and decision-making were tested after a night of mission-driven total sleep deprivation. The Iowa Resilience to Sleeplessness Test (iREST) Cognitive Subscale, which measures subjective cognitive resilience to sleep loss, was administered after a week of recovery sleep. A receiver operating characteristic (ROC) curve was used to determine whether the iREST Cognitive Subscale can discriminate between gene carriers, and a cutoff score was determined. Cognitive performance after sleep deprivation was compared between those below/above the cutoff score using t-tests or Mann-Whitney U tests. Results The iREST discriminated between allele variations for COMT (ROC=.65,SE=.07,p=.03), with an optimal cutoff score of 3.03 out of 5, with 90% sensitivity and 51.4% specificity. Soldiers below the cutoff score had significantly poorer for psychomotor vigilance reaction time (t=-2.39,p=.02), response inhibition errors of commission (U=155.00,W=246.00,p=.04), and decision-making reaction time (t=2.13,p=.04) than Soldiers above the cutoff score. Conclusion The iREST Cognitive Subscale can discriminate between those with and without specific vulnerability/resilience-related genotypes. If these findings are replicated, the iREST Cognitive Subscale could be used to help military leaders make decisions about proper personnel placement when sleep loss is unavoidable. This would likely result in increased safety and improved performance during military missions. Support (if any) Support for this study came from the Military Operational Medicine Research Program of the United States Army Medical Research and Development Command.

Abstract Introduction Insufficient sleep is ubiquitous among active duty service members in operational settings. Although insufficient sleep has been linked to poor cognitive, psychological, and physiological outcomes in military populations, little research has investigated the impact of insufficient sleep on Soldier occupational wellbeing. This study examined the longitudinal association between sleep quality and occupational functioning in a population of active duty U.S. Army Soldiers. Methods Sixty male Soldiers (age 25.41±3.74 years) participated. Sleep quality and occupational outcomes were assessed four weeks apart (before and after an annual training mission). Sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI). Occupational outcome measures included the Emotional Exhaustion Scale, Walter Reed Functional Impairment Short Scale, Role Overload Scale, and Perceived Stress Scale. Linear regressions assessed the prediction of PSQI Global Score on occupational outcome scores. Student’s t-tests compared occupational outcomes between “good” and “poor” sleepers (PSQI Global Score > 5 = poor sleeper). Results Poorer sleep quality at baseline broadly predicted poor occupational outcomes post-training. Specifically, higher PSQI Global Scores predicted higher emotional exhaustion (B = 1.6, p < 0.001, R2 = 0.25), functional impairment (B = 0.29, p < 0.03, R2 = 0.14), role overload (B = 28, p < 0.008, R2 = 0.12), and perceived stress (B = 0.34, p < 0.004, R2 = 0.2). Furthermore, occupational outcome scores were significantly higher in poor sleepers than good sleepers: emotional exhaustion: (t(58) = -4.18, p < .001); functional impairment: (t(59) = -3.68, p = .001); role overload (t(58) = -3.20, p = .002); and perceived stress (t(58) = -2.43, p = .02). Conclusion This study identified a longitudinal relationship between sleep quality and occupational outcomes, suggesting that service members with poor sleep may be at risk for experiencing poor workplace wellbeing. Given the association between service member wellbeing and likelihood to re-enlist, insufficient sleep may negatively impact Soldier attrition. Future studies should aim to augment sleep quality and track occupational outcomes in this population. Support (if any) This work was funded by the Military Operational Medicine Research Program of the United States Army Medical Research and Development Command.

Objective: To assess the relationship between sleep quality and occupational well-being in active duty military Service Members. Design: Longitudinal prospective analysis. Setting: An annual military training event. Participants: US Army special operations Soldiers (n = 60; 100% male; age 25.41 +/- 3.74). Intervention: None. Measurements: The Pittsburgh Sleep Quality Index (PSQI) was administered prior to the training event, and the Emotional Exhaustion Scale, the Role Overload Scale, the Walter Reed Army Institute of Research Soldier-Specific Functional Impairment Scale, and the Perceived Stress Scale were administered after the event. Linear regression models were used to assess the relationship between sleep and occupational wellness measures, and the outcome measures of "good" and "poor" sleepers (per the PSQI scoring criteria) were compared with Student's t tests. Results: Higher (poorer) PSQI Global Scores predicted poorer occupational wellness of all measures (emotional exhaustion: B = 1.60, P < .001, R-2 = 0.25; functional impairment: B = 0.29, P = .03, R-2 = 0.14; role overload: B = 0.28, P = .008, R-2 = 0.12; and perceived stress: B = 0.34, P = .004, R-2 = 0.20). There were additional relationships between specific PSQI component scores and occupational wellness measures, which is a replication of This team's previous work. Furthermore, emotional exhaustion (t(58) = -4.18, P < .001), functional impairment (t(59)= -3.68, P = .001), role overload (t(58) = -3.20, P = .002), and perceived stress (t (58) = -2.43, P = .02) were all higher in poor sleepers. Conclusions: The findings of this study suggest that US Army special operations Soldiers who have poorer sleep quality may be at increased risk for having poorer occupational well-being. Published by Elsevier Inc. on behalf of National Sleep Foundation.

OBJECTIVES:Explore the impact transitioning from daytime to nighttime operations has on performance in U.S. Army Rangers.METHODS:Fifty-four male Rangers (age 26.1±4.0 years) completed the Y-Balance Test (YBT), a vertical jump assessment, and a grip strength test at three time points. Baseline testing occurred while the Rangers were on daytime operations; post-test occurred after the first night into the nighttime operation training (after full night of sleep loss), and follow-up testing occurred six days later (end of nighttime training).RESULTS:On the YBT, performance was significantly worse at post-test compared to baseline during right posteromedial reach (104.1±7.2cm vs 106.5±6.7cm, p=.014), left posteromedial reach (105.4±7.5cm vs 108.5±6.6cm, p=.003), right composite score (274.8±19.3cm vs 279.7±18.1cm, p=.043), left composite score (277.9±18.1cm vs 283.3±16.7cm, p=.016), and leg asymmetry was significantly worse in the posterolateral direction (4.8±4.0cm vs 3.7±3.1cm, p=.030) and the anterior direction (5.0±4.0cm vs 3.6±2.6cm, p=.040). The average vertical jump height was significantly lower at post-test compared to baseline (20.6±3.4 in vs 21.8±3.0 in, p=.004). Baseline performance on YBT and vertical jump did not differ from follow-up.CONCLUSIONS:Army Rangers experienced an immediate, but temporary, drop in dynamic balance and vertical jump performance when transitioning from daytime to nighttime operations. When feasible, Rangers should consider adjusting their sleep cycles prior to anticipating nighttime operations in order to maintain their performance levels. Investigating strategies that may limit impairments during this transition is warranted.

PURPOSE: Investigate the association between musculoskeletal injuries and self-reported sleep quality in U.S. Army Rangers. METHODS: This study was part of a larger study investigating the impact of sleep and circadian desynchrony on the health of U.S. Army Rangers. At baseline, the Rangers were asked if they currently have any musculoskeletal injuries. They also completed a modified Pittsburgh Sleep Quality Index (PSQI), the Insomnia Severity Index (ISI), and were asked to rate their average sleep quality (0 equating to “Poor Quality” and 100 equating to “Best Quality”) and specify their average sleep duration over the preceding week. A total of 82 Rangers (male, 25.4 ± 4.0 years) completed all of these questionnaires. RESULTS: The reported musculoskeletal injury prevalence of the Rangers was 15.9% (n = 13). The Rangers that reported an injury, compared to those that did not, had a significantly higher Global PQSI score (6.7 ± 3.7 versus 4.5 ± 2.7, p = .012) and ISI score (10.9 ± 3.7 versus 7.2 ± 4.1, p = .003), both indicative of poorer sleep. In addition, the group reporting an injury rated their average sleep quality over the preceding week significantly lower compared to those that did not report an injury (50.8 ± 17.5 versus 68.9 ± 18.3, p = .001). There was no significant difference in the reported average nightly sleep duration between the injured group (6.1 ± 1.0 hours) and uninjured group (6.5 ± 0.9 hours). CONCLUSIONS: In this cohort of elite male Army Soldiers, having a musculoskeletal injury was associated with poorer sleep quality. Sleep duration was not associated with reported injuries; however, both the injured group and uninjured group averaged less than the recommended amounts of sleep. Future research should further investigate the relationship between injury and sleep, including in other military populations, to ascertain whether improving sleep quality has any positive impact on subsequent injury rates and to better understand how injuries may negatively impact sleep. The views expressed in this abstract are those of the authors and do not reflect the official policy of the Department of Army, Department of Defense, or the U.S. Government.

U.S. Army Rangers must maintain a high level of physical fitness in order to be successful during training and deployment missions. The hormone testosterone increases muscle growth and strength, which leads to better physical fitness and performance. Therefore, maintaining high testosterone levels is of critical importance to this unit.

Background: Sleep loss negatively impacts stationary balance in a laboratory setting, but few studies have examined this link in a naturalistic environment. We tested this relationship in U.S. Army soldiers that often undergo mission-driven sleep loss and who conduct high-risk operations on precarious terrain. Methods: Stationary balance was tested before and after a mission night. Results: After mission-driven sleep loss, in more difficult conditions (but not easy conditions) balance was more unstable and more variable than a rested baseline condition. Furthermore, habitual sleep quality prior to sleep loss predicted the balance decrement after sleep loss. Conclusions: Therefore, mission-driven sleep loss may negatively impact soldier balance, but better sleep prior to the mission may mitigate these negative effects. Published by Elsevier B.V.

PURPOSE: Investigate the impact transitioning from daytime to nighttime operations during military training has on dynamic balance and vertical jump performance in elite Army Soldiers. METHODS: This study was part of a larger study investigating the impact sleep loss and circadian desynchrony during military training have on the health and performance of elite Army Soldiers. Elite Army Soldiers (all male) performed a cognitive/motor battery (pre-test), including the Y-Balance Test (YBT) and a vertical jump assessment, approximately 2 weeks prior to switching from daytime to nighttime operations during military training (getting on a “reverse sleep cycle”). After the first night into the nighttime operation training (after a full night of sleep loss), the Soldiers were reassessed (post-test) on the YBT (n=74, 26.0 ± 4.1 years) and vertical jump (n=75, 26.2 ± 3.9 years). RESULTS: Compared to pre-test, the elite Army Soldiers demonstrated a significant decrease during the posteromedial reach bilaterally (Right = -2.4 ± 6.5 cm, p = .003; Left = -2.9 ± 7.1 cm, p = .001), and a significantly lower composite score bilaterally (Right = -4.4 ± 15.8 cm, p = .018; Left = -4.6 ± 14.7 cm, p = .009) on the YBT at post-test. In addition, at post-test, asymmetry in the posterolateral direction was significantly worse (1.3 ± 3.9 cm, p = .004) compared to pre-test. No other significant pre- to post-test differences were noted on the YBT. The vertical jump height was also significantly lower (-1.0 ± 3.0 inches, p = .004) at post-test, compared to pre-test. CONCLUSION: Transitioning from daytime to nighttime operations during military training negatively impacts dynamic balance and vertical jump performance in elite male Army Soldiers. Considering the post-test was conducted after the first night into the nighttime operation training, where Soldiers missed their normal sleep opportunity, sleep loss and fatigue were likely contributing factors to the decreased performance. Investigating strategies that may limit these physical impairments during the transition from daytime to nighttime operations is warranted. Future research should also to investigate whether the noted impairments have any impact on this population’s injury risk considering impaired dynamic balance has been associated with injury risk in other athletic populations.