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Specialized training for elite US military units is associated with high attrition due to intense psychological and physical demands. The need to graduate more service members without degrading performance standards necessitates the identification of factors to predict success or failure in targeted training interventions.
The aim of this study was to continuously quantify the mental and physical status of trainees of an elite military unit to identify novel predictors of success in training.
A total of 3 consecutive classes of a specialized training course were provided with an Apple iPhone, Watch, and specially designed mobile app. Baseline personality assessments and continuous daily measures of mental status, physical pain, heart rate, activity, sleep, hydration, and nutrition were collected from the app and Watch data.
A total of 115 trainees enrolled and completed the study (100% male; age: mean 22 years, SD 4 years) and 64 (55.7%) successfully graduated. Most training withdrawals (27/115, 23.5%) occurred by day 7 (mean 5.5 days, SD 3.4 days; range 1-22 days). Extraversion, positive affect personality traits, and daily psychological profiles were associated with course completion; key psychological factors could predict withdrawals 1-2 days in advance (
Gathering accurate and continuous mental and physical status data during elite military training is possible with early predictors of withdrawal providing an opportunity for intervention.
Owing to the nature of the US conflicts in Iraq and Afghanistan, which span nearly two decades, the US military comprised many experienced warfighters who are highly trained and specialized [
Owing to continued global threats, there is a need to graduate more highly trained Recon Marines, without degrading performance standards [
To help determine novel predictors of success or failure in training, we collected continuous mental and physical status of Recon trainees to build comprehensive models capable of identifying the collective load of Recon training and the thresholds at which trainees are most likely to remove themselves from the course. In doing so, novel insight into the mental and physical processes associated with these factors can inform the theories of human performance and improve desired outcomes in elite military training.
The University of Southern California, Center for Body Computing, a digital health and human performance research center, partnered with Reconnaissance Training Company leadership at Camp Pendleton, California, in 2016 to design and implement a human performance study aimed at obtaining continuous assessments of Recon trainees, using connected technology to garner insights and identify novel predictors of training completion. Over the course of 36 months, requirements were identified that included the need to collect (1) personality profiles, as prior military studies had identified personality traits such as grit to be predictive of training success [
The 3 successive classes of Marines and Sailors entering the 25-day Basic Reconnaissance Primer Course (BRPC) of the Reconnaissance Training Company at Camp Pendleton, California, were offered study enrollment (April 26, 2018, to August 17, 2018) on the first day of orientation (
Marine and sailor study enrollment description and completion.
Baseline demographics of study subjects.
Characteristic | Value | |
Age (years), mean (SD) | 22 (4) | |
Height (cm), mean (SD) | 175 (8) | |
Weight (kg), mean (SD) | 77 (9) | |
Participated in high school sports (N=104), n (%) | 79 (76.0) | |
Marital status: single (N=115), n (%) | 107 (93.0) | |
Time in military (months), mean (SD) | 23 (23) | |
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Marine officer | 4 (3.5) |
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Marine enlisted | 105 (91.3) |
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Navy enlisted | 12 (10.4) |
The 25-day BRPC is the initial phase of Reconnaissance training that must be successfully completed to advance to the 60-day Basic Reconnaissance Course (BRC), which is required for graduation. Marines and Sailors are accepted into the BRPC from other marine operational specialties or after enlistment and completion of entry-level infantry training.
The BRPC consists of structured daily training on land and water that embeds the cognitive and physical assessments that trainees have to complete, benchmarked to time or quality standards. The aquatics training includes various high-intensity underwater and treading drills that impose intense psychological and physical stressors. This course selectively screens and prepares trainees to acquire the mental and physical skills taught in BRC, such as land navigation, coastal piloting, and radio communications, which render them able to serve as a Reconnaissance Marine within the Fleet Marine Forces (
Photographs of trainees engaged in land exercises (a) and water exercises (b).
Trainees can drop out of training by choice on request (DOR), and medical personnel can remove trainees from the course if they have an illness or injury (medical) or instructors determine that trainees pose a safety hazard to themselves or other trainees (safety) or fail to meet one or more of the course training standards (performance). Trainees that DOR are not permitted to repeat the training course and are then assigned back to their prior unit or are assigned to a different training school to obtain another military occupational specialty. Those who are excluded from the course for medical, safety, or performance reasons may repeat the course at the next scheduled course initiation.
A specially designed software app, used for subject consent and data collection, was designed on Apple’s ResearchKit platform (Apple Inc and Thread Research) for the purposes of this study (
Sample study app screenshots: (a) initial study screen, (b) prestudy survey screen, and (c) daily survey.
Study metrics by collection method.
Method and metric | Measurement | ||
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Questionnaires: prestudy |
Demographic survey Big Five Inventory [ Psychopathic Personality Inventory-Revised [ Positive and Negative Affect Schedule [ Satisfaction with Life Scale [ Five Facet Mindfulness Questionnaire [ Grit Scale [ The Ego Resilience Scale [ |
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Daily questionnaires ( |
Mental and physical pain scale (1-5) Sleep, hydration, and nutrition (self-report) Confidence in instructors and graduation (4 questions) |
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Daily activity |
Steps Resting and active energy expenditure (calories) |
Statistical analyses were performed using R Statistical Software (Bell Laboratories) [
The summary data for the course completion of all 3 BRPC study subjects are shown in
The timing and context of DORs fell into a consistent pattern, and 93% of drops occurred before an impending aquatic event or in the training pool. The DORs that did not occur before an impending aquatic event were observed at the beginning of the training day in a waiting area outside of the training schoolhouse. There were no significant differences between course completion groups with respect to age, height, weight, history of high school sports participation, marital status, years in the Marine Corps, Marine rank, or previous BRPC attempts (
Course completion results for test standard assessments of (a) sit-ups; (b) pull-ups, timed; and (c) 3-mile run.
Mean heart rate (beats per minute) per group (course completion and all noncompletion categories) compared by time of day.
Group | 24 hour | Day | Night | |||
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Mean (SD) | Rangea | Mean (SD) | Rangea | Mean (SD) | Rangea |
Pass (BPMb) | 110 (30) | 30-210 | 112 (29) | 30-210 | 64 (16) | 36-202 |
Drop on request (BPM) | 106 (31) | 30-210 | 111 (28) | 30-210 | 64 (19) | 40-171 |
Medical (BPM) | 116 (29) | 34-210 | 118 (28) | 34-210 | 73 (19) | 43-175 |
Safety (BPM) | 111 (29) | 30-208 | 113 (27) | 30-208 | 69 (10) | 41-139 |
Performance (BPM) | 118 (28) | 32-209 | 119 (27) | 32-209 | 70 (13) | 40-137 |
aApple Watch heart rate sensor supports a range of 30-210 beats per minute [
bBPM: beats per minute.
Mean activity (daily steps) per group (course completion and all noncompletion categories).
Group | Mean (SD) | Range |
Pass (daily steps) | 10,537 (3195) | 500-15,311 |
Drop on request (daily steps) | 4491 (4541) | 239-15,057 |
Medical (daily steps) | 4585 (4899) | 456-15,537 |
Safety (daily steps) | 6569 (4677) | 780-11,787 |
Performance (daily steps) | 7660 (3395) | 2734-11,674 |
Mean energy expenditure (calories) per group (course completion and all noncompletion categories) compared by activity level.
Group | Activea | Resting | |||
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Mean (SD) | Range | Mean (SD) | Range | |
Pass (calories) | 1837 (1231) | 1-9133 | 1523 (426) | 107-4085 | |
Drop on request (calories) | 1329 (1266) | 1-4911 | 1430 (496) | 232-3851 | |
Medical (calories) | 961 (1294) | 2-6021 | 1491 (527) | 138-2652 | |
Safety (calories) | 1271 (1445) | 1-5746 | 1410 (430) | 133-1976 | |
Performance (calories) | 1450 (971) | 11-3667 | 1413 (444) | 207-1743 |
aApple Watch uses logged workouts to calculate active energy expenditure.
The compliance of the baseline personality surveys was as follows: (1) BFI: 94.0% (108/115), (2) PANAS: 93.0% (107/115), (3) PPI: 76.5% (88/115), (4) SWLS: 92.2% (106/115), (5) ERS: 90.4% (104/115), (6) Grit: 88.7% (102/115), and (7) FFMQ: 83.5% (96/115). The baseline personality traits that were most associated with course completion include extroversion and positive affect.
Subjects who had DOR reasons for course failure versus those completing the course demonstrated an increase in emotional (
There was no difference in self-reported feelings related to instructor support, adequacy of hydration, nutrition, or sleep duration between subjects completing or not completing the course. All trainees thought about quitting the course on at least one daily survey.
As the need for a modernized military grows, there is also a need to understand how best to involve larger numbers of warfighters in higher-level training and operations without degrading training and performance standards [
Previous studies of elite military training have focused on psychological and physiological factors. In a previous study of Navy Sea, Air, and Land (SEAL) warfighters, compared with the general male population, SEALs scored lower in neuroticism and agreeableness and higher in extraversion and conscientiousness [
On the basis of this prospective study, we see evidence that the standard physical fitness tests and physiological measurements provide limited information regarding a Marine’s or Sailor’s likelihood of voluntarily dropping from training. Of all 4 land training standard assessments, only pull-ups were predictive of an increased probability of a DOR. Similarly, heart rate data was not a good predictor, perhaps reflecting the fact that trainees were young and healthy, and there was limited variability in the range of heart health among the sample, suggesting that their cardiovascular health was adequate to complete training.
The mean step counts of those who successfully completed the course were significantly higher than those who failed to complete the course, most of whom were removed from the course by training day 7. Not all training days involve physical training; subjects spent training days in a classroom environment as well, hence the wide range in mean daily step counts. Still, mean daily step counts correlate to approximately 2 to 3 miles daily in those who withdrew versus a mean of over 5 miles daily in those who completed the course. This signifies that most of the work output of the training course occurred after trainees withdrew, supporting the notion that they did not withdraw for physical reasons, and this may hint at broader clues as to the importance of motivation and personal narrative in determining success.
Indirect measures of energy expenditure, such as active energy, also indicate that those who successfully completed the course expended higher activity over time, versus those who were unsuccessful at completing the course. This was true for all categories of unsuccessful course completion except performance withdrawals. Those who were unsuccessful at completing the course due to performance withdrawal also tended toward higher step counts and were dropped due to failure to complete cognitive and physical tasks. This metric is also important because it encompasses and can measure training work done in water, which is not accounted for in step counts. The energy expenditure data are also revealing in that they provide the first comprehensive data on the total mean daily energy expenditure of trainees. Although the range is considerable, the observation that in the trainees who successfully completed the course approximately 3300 calories/day are needed to maintain caloric equilibrium is important knowledge in terms of nutritional planning and avoidance of weight loss [
Although previous studies have examined the existing military training assessments, such as physical fitness scores [
We found that higher levels of self-reported positive affect and extraversion were significantly associated with successful course completion. Moreover, although all trainees entertained thoughts of quitting, those that did voluntarily or involuntarily withdraw were more introverted and had less demonstrative personality types than those that successfully completed the course. In contrast to previous research performed in military academies or in other military training [
A unique aspect of this study is that it demonstrates the feasibility of a fully comprehensive and continuously collected model of human performance research in a naturalistic military training environment. We demonstrated the ability to collect accurate and continuous physical performance and psychological data throughout a 25-day course that takes place on land and in water. The success of the model was validated across the 3 successive training classes that we enrolled. The technology platform, Apple’s ResearchKit, HealthKit, and CareKit software
Apple Watch data were collected using HealthKit, which provides the ability to collect Watch data and integrate it into the dataset collected on ResearchKit. In the future, we will leverage HealthKit to integrate other connected sensors such as weight, oxygen saturation, or temperature. The accuracy of the direct measures, such as heart rate, collected from the Watch using photoplethysmography, has been demonstrated by others to have a sensitivity and specificity of 98% and 90%, respectively [
Other benefits of this model include the ability to more quickly and efficiently translate study findings into interventions that can be tested in the subsequent classes. For example, our finding that declines in both daily self-reported emotional and physical pain scores and confidence in graduating preceded DORs from training provide an opportune target to build and test interventions. In addition, the finding that most DORs occurred in relation to an aquatic training event suggests that these events are causing significant doubt, distress, and lack of confidence. The finding that individuals who completed the course manifest more positive affect suggests that an effective intervention should instill these traits and behaviors. Ideally, an intervention targeted at cultivating confidence for these activities will heighten the probability of successful completion without changing the rigorous nature of the training itself. This could include specially designed educational or motivational video content, which is delivered to the trainee manifesting these thoughts and feelings, through the next version of the study software app. Similarly, advances in technologies, such as the real-time electrocardiogram (ECG) capability on the Apple 4 Series Watch, can be easily integrated into the study and provide another opportunity to validate the heart rate data. These ECG and heart rate capture capabilities may provide a real-time safety component for these trainees, while undergoing intense physical training. For instance, if a trainee sustained a very elevated heart rate, this could be validated by obtaining an ECG from the Watch and displayed to instructors in real time, using a CareKit-enabled data dashboard, which could then allow for timely medical assessment of that individual.
We have designed and implemented a flexible and continuous research model for military training that can easily accommodate best-in-breed sensors, allow for rapid software integration to more efficiently assess and test novel training interventions, and increase the course completion rate and quality of new Reconnaissance Marines and other military equivalents. This model can also provide important efficiencies and data flow that will help assess the medical well-being of trainees. We also found that despite the physical rigor involved in Reconnaissance Marine training, most of the attrition is due to mental deterioration rather than physical deterioration, and students who DOR often do so outside of the deepest physical stressors, that is, while on the pool deck as opposed to actually being in the pool. These signs of deterioration can be identified before trainees withdraw or are withdrawn from training, and interventions that target the reversal of these feelings as well as help to gain a deeper understanding of how to determine selection criteria can be designed.
We did not collect data on the entirety of the courses offered by the Reconnaissance Training Company, namely, the follow-on 60-day BRC that follows the 25-day BRPC, which limits our ability to draw conclusions about fully graduating into the Reconnaissance military occupational specialty. We also did not collect any data on weekends, mostly due to initial study design limitations with maintaining the study equipment inventory of iPhones, Watches, and data plans, which can be addressed through improved battery life and study design, leading to a model capable of measuring students during the entirety of trainee experience, including time off and personal time.
Daily questions (
Although the Apple Watch has been validated in other studies [
Owing to the nature of military training, another limitation is that the number of subjects per group is highly unequal. To address this, we combined data from the 3 cohorts across groups to create larger sample sizes. In the future, we will require additional cohorts to increase the sample size and validate the results.
Another possible limitation of our study is the use of self-report surveys, which can be prone to bias or misreporting. However, other studies in military populations have used the same or similar personality and behavioral self-report surveys [
This study demonstrates the feasibility and accuracy of actionable data that can be collected using a natural, continuous, and holistic model of data collection using a modern digital platform, custom-made software, and body-worn sensors. This model of innovation has the potential for rapid discovery in military training environments that may lead to better training and selection of military personnel and translate into other elite training environments. In addition, the data paint a novel picture of the mind and body processes in determining performance outcomes—findings that can generalize into any high pressure, competitive domain.
Daily survey questions.
Rates of successful course completion and failure to complete by category for all 3 classes. DOR: drop on request.
Big Five Inventory
beats per minute
Basic Reconnaissance Course
Basic Reconnaissance Primer Course
Basic Underwater Demolition/SEAL
drop on request
electrocardiogram
Ego Resilience Scale
Five Facet Mindfulness Questionnaire
Positive and Negative Affect Scale
Sea, Air, and Land
School of Infantry-West
Satisfaction with Life Scale
The authors are deeply indebted to the leadership of the Reconnaissance Training Company at the School of Infantry-West (SOI-W) at Camp Pendleton for their partnership, ideas, and numerous hours spent teaching the authors their objectives and needs. These crucial interactions enabled the authors to design a study targeted at meeting real objectives efficiently. The authors are also grateful to the leadership of the SOI-W for supporting this line of research.
None declared.