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Quantification of physical activity performed during Us Army Basic Combat Training.

Army Basic Combat Training (BCT) is a physically demanding, 10-week training program designed to develop basic soldiering skills and prepare recruits for the physical and mental rigors of military service. (1-3) Depending on their military occupational specialty, Soldiers may be required to perform a number of tasks involving a high degree of physical effort during their military careers. Therefore, developing and maintaining a high level of physical fitness among Soldiers is often regarded as a priority by the US Army. (2)

While BCT is designed to enhance the physical fitness and military performance of the recruit, it also has the potential to produce less positive outcomes. To improve physical fitness, the physical activity (PA) performed by recruits must be of the appropriate frequency, intensity, and duration. (2,4) If the volume of physical training is too low, it results in little or no change in physical performance, but if the volume is too high, it can lead to injury. (2) Previous studies show that as the amount of physical training increases, so does the risk of injuries in a number of populations, including runners, (5-12) military recruits, (3,13,14) and participants in sports and other leisure-time activities. (15,16) Injury among recruits poses a problem for the military in that it can result in significant medical expenses, decrease the number of deployable Soldiers, and ultimately compromise military readiness. (2,17,18)

To improve the physical fitness of Soldiers while also reducing the risk of injury, the Army Physical Fitness School, working with the Army Institute of Public Health, developed a training program known as Physical Readiness Training (PRT). (2) The PRT program is a precise series of calisthenics, dumbbell drills, climbing drills, running, and other activities that are performed by recruits 3-6 times per week, typically between 5 am and 7 AM. (2) One of the major principles of PRT is that exercise intensity should increase progressively over time by increasing the number of repetitions of some exercises and/or the speed at which some exercises are performed (progressive overload). Compared to traditional BCT physical training programs, PRT has been shown to result in the same or greater improvements in physical fitness while causing fewer injuries. (2,19) In addition to PRT, BCT recruits are also required to perform other physical activities such as obstacle course negotiation, rifle training, unarmed combat (combatives) training, drill and ceremony, land navigation, and road marches with rucksacks and other load-bearing equipment. (1,3)

Although knowledge of the types of activities performed is available, information regarding the exposure of new recruits to PA (ie, the actual dose) at each of the 4 BCT sites is lacking. Additionally, although the graduation requirements of BCT are identical across training sites, battalions, and companies, (20) the amount of time needed to teach specific soldiering skills may vary. Finally, although doctrine requires that PRT and training for military skill development be standardized across BCT sites, there are concerns that the standardization may not be closely followed. Therefore, the purposes of this study were to (1) characterize and quantify the amount of PA actually performed by recruits during a BCT cycle at 2 of the Army's 4 BCT sites, and (2) determine the intensity and types of physical training at the 2 locations. One of the principles of PRT is progressive overload (progressive, systematic increase in exercise intensity over days), so the average weekly intensity of physical training between 5 AM and 7 AM (when physical training was likely to be conducted) was examined.

METHODS

Subjects

Data for this study were collected from recruits in 2 training battalions during separate 10-week BCT cycles. The first iteration took place June to August 2010 at Fort Jackson, South Carolina, during which time recruits from 6 training companies were observed. The second iteration took place July to September 2011 at Fort Sill, Oklahoma, during which time recruits from 5 training companies were observed.

Prior to the start of the study, the principal investigator informed the recruits in all training companies of the requirements and potential risks of participating in the study. Those who chose to volunteer signed an informed consent document approved by the Institutional Review Board of the US Army Research Institute of Environmental Medicine (USARIEM). The investigators followed the policies for protection of human subjects as prescribed in Army Regulation 70-25, (21) as well as the provisions of 45 CFR Part 46, Protection of Human Subjects. (22) Recruits were included in the study if they were at least 18 years of age, were assigned to one of the study battalions for the 10-week BCT course, and were able to fully participate in all the activities of BCT at the start of the investigation.

Procedures

The length of a typical BCT cycle is 10 weeks. In this study, study personnel spent the first week of each BCT cycle recruiting volunteers and obtaining their consent. During the last week, recruits spent most of their time cleaning and turning in equipment, and practicing for graduation. Therefore, complete data was obtained for the majority of volunteers for the middle 8 weeks of their BCT cycle.

Physical activity was assessed by 3 methods: instrumentation with an accelerometer, direct observation, and daily PA logs.

Accelerometer

The accelerometer used in this study was the ActiGraph GT3X triaxial accelerometer (ActiGraph, LLC, Pensacola, FL). The accelerometer senses acceleration along 3 axes: vertical, anterior-posterior, and mediolateral. The accelerometer output is then recorded in "counts," which are the summation of the absolute values of the sampled changes in acceleration measured during a user-defined time period. The accelerometer has previously been shown to be a valid and reliable tool for measuring PA intensity among adults. (23,24)

At the beginning of each BCT cycle, recruits received both written and verbal instructions on how to wear the accelerometer: over their left hip in a pouch on a belt, Monday through Saturday, during most of the BCT cycle. Since Sundays were typically reserved for religious observance and rest rather than training, recruits were not asked to wear the accelerometer on this day. If a recruit who had been selected to wear the accelerometer became injured, ill, or was separated from the platoon for a portion of the day (Monday-Saturday), that recruit was replaced with another from the same training company. Research staff performed compliance checks to ensure all volunteers wore the devices properly.

Research staff distributed the accelerometers to participants before the first formation each morning and collected them near the end of training each day, usually preceding the evening meal. This allowed for equipment accountability, data downloading, and battery recharge. From the accelerometers, daily time (minutes) each recruit spent in sedentary-, light- (<3metabolic equivalent (MET)), moderate- (3-6 MET), and vigorous-intensity (>6 MET) activities was categorized by means of the Freedson categories, which define sedentary or light-intensity activity as 0 to 1,951 counts/minute, moderate PA as 1,952 to 5,724 counts/minute, and vigorous intensity PA as 5,725 or more counts/minute. (25)

Direct Observation

The direct observation portion of this study employed the continuous duration recording method. Trained observers recorded changes in a recruit's PA as the change in activity occurred. (24) A novel PA tracking software (PAtracker), designed specifically for this type of direct observation and developed jointly by L3-Communications (San Diego, CA) and the USARIEM, was used in this study. The PAtracker software was installed on smartphone devices. Trained observers logged a recruit's PA by selecting it from a predetermined menu on a touch-sensitive screen. The software automatically added a time stamp and recorded the data in each activity to a data file.

Within the PAtracker software, PA was coded by body position, intensity, activity type, and external load. Body positions included kneeling, lying, sitting, and standing. Activity types included stationary, menial tasks, walking, calisthenics, cadence marching, combatives, running, obstacles/climbing, crawling, and lifting/carrying. Physical activity was also classified by intensity (sedentary, light, moderate, vigorous) and load carried (0-10 lbs, 10-25 lbs, 25-50 lbs, 50-75 lbs, or >75 lbs).

Observers recruited from the local BCT geographic area were hired to perform the direct observation portion of this study. Prior to the start of the study, all observers completed training (10 hours over 3 consecutive days) on the use of the PAtracker device as well as the body positions, activity types, loads, and intensities they would observe during the study.

Direct observation commenced at the beginning of each training day when recruits received their accelerometers, and all activities during the day were recorded. Within each company, a single recruit who was wearing an accelerometer was followed and observed by one trained observer. If this recruit was not training that day, another recruit wearing an accelerometer was identified and followed. Although individual recruits in each company were observed, the direct observation data were treated as unit data reflective of the PA performed by the entire company.

Daily Physical Activity Log

At the end of each training day, all recruits wearing an accelerometer completed a daily PA log; they were asked to report the amount of time (hours: minutes) they spent wearing the accelerometer that day as well as the amount of time (hours: minutes) they spent sleeping during the night before. Regarding the time spent wearing the accelerometer that day, recruits were asked to account for how much of that time they spent sitting, standing, walking/marching, and running. Finally, recruits were asked to report the amount of time they spent doing chores or barracks maintenance, doing calisthenics/obstacle courses, and carrying a load. Upon the recruit's completion of the PA log, a study investigator checked the questionnaire to ensure it had been completed properly and then clarified any discrepancies by speaking with the recruit.

Statistical Analyses

Descriptive statistics (mean [+ or -] SD) were calculated for all study variables. Independent sample t-tests were performed to examine differences between training sites in PA measured by the accelerometer, direct observation, and self-report PA Logs. Repeated measures analysis of variance was used to examine weekly differences in time spent in moderate- to vigorous-intensity PA measured by the accelerometer while recruits performed PRT at each training site (between 5 AM and 7 AM). All statistical analyses were performed with IBM SPSS Statistics (V 14.0) software (IBM Corp, Chicago, IL) for Windows with P<.05 established as the level of statistical significance.

RESULTS

Within each of the 11 training companies included in this study, 24 recruits were outfitted with an accelerometer and completed a daily PA log. This resulted in a total of 144 recruits at Fort Jackson and 120 recruits at Fort Sill. From each company, 6 recruits from each of 4 platoons totaled 24 recruits from each company (6 recruits/platoon x 4 platoons/company=24 recruits/company). When possible, at least one of the 6 recruits from each platoon was a woman.

Accelerometer

The Fort Jackson recruits wore the accelerometer a total of 47 days, and the recruits at Fort Sill wore it 44 days. Table 1 lists the cumulative time as well as the number of days that recruits from both training sites spent in each intensity category measured by the accelerometer. On average, recruits at Fort Jackson wore the accelerometer for a longer period of time each day than the recruits at Fort Sill (754.0 [+ or -] 112.6 minutes/day vs 677.4 [+ or -] 102.6 minutes/day, P < .001). Therefore, all accelerometer comparisons between the two training sites in this study were made using the average daily percentage of time. The exception was time spent in moderate- to vigorous-intensity PA between 5 AM and 7 AM, which was examined using average daily minutes. This variable was an exception because weekly changes were examined at each training site as opposed to being compared between the 2 training sites.

Figure 1 shows the average daily percentage of time that recruits from each training site spent in each activity intensity over the course of the BCT cycle. Recruits at Fort Jackson spent a larger percentage of their time engaged in light-intensity activities (23.0% [+ or -] 10.4% vs 15.8% [+ or -] 2.0%, P <.001) and a smaller percentage of their time in sedentary activities (58.9% [+ or -] 10.6% vs 65.9% [+ or -] 4.9%, P <.001) when compared to recruits at Fort Sill. Additionally, recruits at both training sites spent most of their time (60% to 70%) in sedentary activities and less time (<10%) in vigorous activities.

Figure 2 shows the average daily percentage of time that recruits at both training sites spent in moderate- to vigorous-intensity activity between 5AM and 7AM, when recruits were likely participating in PRT. Over the course of BCT, recruits at Fort Jackson spent an average of 46.1 [+ or -] 4.9 minutes/day while recruits at Fort Sill spent an average of 44.4 [+ or -] 3.8 minutes/day participating in moderate- to vigorous-intensity PA between 5AM and 7AM (P = .443). Repeated measures analysis of variance indicated that time spent in moderate- to vigorous-intensity PA changed week to week at Fort Jackson (P=.009) but did not significantly change week to week at Fort Sill (P = .211).

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PAtracker

Table 2 shows the number of days trained observers followed and observed recruits using the PAtracker. Table 2 also lists the average daily time recruits from both training sites spent in each body position, activity type, intensity, and carrying various external loads, as measured with the PAtracker. Recruits were followed with the PAtracker an average of 783.4 [+ or -] 135.3 minutes/day for 47 days at Fort Jackson and 708.9 [+ or -] 128.5 minutes/day for 44 days at Fort Sill (P < .001). As was the case with the accelerometer, the recruits at Fort Jackson were observed with the PAtracker for a longer period of time each day than were the recruits at Fort Sill. Therefore, all PAtracker comparisons between the 2 training sites in this study were made using the average daily percentage of time.

The average daily percentage of time recruits at Fort Jackson and Fort Sill spent in each body position is shown in Figure 3A. Recruits at Fort Jackson spent a larger percentage of time sitting (38.6% [+ or -] 12.9% vs 30.9% [+ or -] 11.8%, P<.001) and a smaller percentage of time kneeling (1.2% [+ or -] 1.8% vs 1.9% [+ or -] 2.6%, P <.001) and standing (57.0% [+ or -] 12.6% vs 64.0% [+ or -] 12.2%, P<.001) compared with recruits at Fort Sill. Little difference was observed in the percentage of time recruits at both training sites spent lying down (2.9% [+ or -] 3.4% vs 3.1% [+ or -] 2.1%, P=.951).

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Figure 3B shows the average daily percentage of time recruits at Fort Jackson and Fort Sill spent in each activity intensity category. Recruits at Fort Jackson spent a larger percentage of time sedentary (54.5% [+ or -] 18.1% vs 48.2% [+ or -] 22.6%, P=.001) and a smaller percentage of time in light-intensity activities (36.5% [+ or -] 15.5% vs 44.1[degrees]% [+ or -] 21.8%, P<.001) when compared to recruits at Fort Sill. Little difference was observed between the 2 training sites in terms of percentage of time spent in moderate- (8.0% [+ or -] 11.9% vs 6.8% [+ or -] 7.3%, P=. 193) or vigorous-(1.1% [+ or -] 2.3% vs 0.9% [+ or -] 1.9%, P = .290) intensity activities. As was the case with the accelerometer, recruits at both training sites spent a large percentage of time (about 50%) in sedentary activities and a small percentage of time (about 1%) in vigorous-intensity activities.

Figure 4 shows the average daily percentage of time recruits at both Fort Jackson and Fort Sill spent in different types of activities. Recruits at Fort Jackson spent a larger percentage of time engaging in combatives (1.6% [+ or -] 4.0% vs 0.4% [+ or -] 2.0%, P < .001), being stationary (55.1% [+ or -] 14.3% vs 41.8% [+ or -] 16.8%, P < .001), and walking (11.6% [+ or -] 8.5% vs 8.6% [+ or -] 9.7%, P < .001), and a smaller percentage of time cadence-marching (3.3% [+ or -] 3.3% vs 4.7% [+ or -] 4.0%, P<.001), completing obstacles (0.5% [+ or -] 2.1% vs 1.1% [+ or -] 4.0%, P=.030), performing menial tasks (22.3% [+ or -] 15.0% vs 37.6% [+ or -] 17.9%, P < .001), and running (1.2% [+ or -] 1.7% vs 1.6% [+ or -] 2.0%, P = .037) when compared to recruits at Fort Sill. Little difference was observed between the 2 training sites in terms of percentage of time recruits spent in calisthenics (3.9% [+ or -] 3.6% vs 3.8% [+ or -] 3.0%, P = .700), crawling (0.2% [+ or -] 1.1% vs 0.1% [+ or -] 0.3%, P = .102), and lifting/carrying (0.2% [+ or -] 0.9% vs 0.3% [+ or -] 0.8%, P = .097).

The average daily percentage of time recruits at both training sites spent carrying various external loads over the course of a BCT cycle is shown in Figure 5. Recruits at Fort Jackson spent a larger percentage of time carrying 0-10 lbs (84.0% [+ or -] 19.0% vs 79.6% [+ or -] 19.7%, P=.011) and a smaller percentage of time carrying 25-50 lbs (3.5% [+ or -] 7.5% vs 9.7% [+ or -] 13.6%, P<.001) and 50-75 lbs (0.2% [+ or -] 1.2% vs 1.0% [+ or -] 3.2%, P<.001). Little difference was observed between the two training sites in terms of percentage of time recruits spent carrying 10-25 lbs (12.2% [+ or -] 16.6% vs 9.6% [+ or -] 14.8%, P = .066) or greater than 75 lbs (0.1% [+ or -] 0.3% vs 0.2% [+ or -] 1.3%, P = .064). Recruits at both training sites spent a large percentage of time (about 80%) carrying 0-10 lbs and a very small percentage of time ([less than or equal to] 1%) carrying over 50 lbs.

Physical Activity Log

Table 3 lists the cumulative time (hours and minutes) recruits from both training sites reported sitting, standing, walking, running, participating in calisthenics, doing chores, and carrying loads, based on their daily PA logs. Recruits at Fort Jackson accounted for an average of 601.1 [+ or -] 52.5 minutes/day for 47 days, while recruits at Fort Sill accounted for an average of 672.7 [+ or -] 28.3 minutes/day for 44 days (P<.001). Recruits at Fort Sill accounted for a longer period of time each day than recruits at Fort Jackson did. Therefore, all PA Log comparisons between the 2 training sites in this study were made using the average daily percentage of time, with the exception of time spent sleeping each night.

The average daily percentage of time recruits from both training sites reported sitting, standing, walking, and running is shown in Figure 6. Recruits at Fort Jackson reported spending a larger percentage of time sitting (48.7% [+ or -] 13.6% vs 42.2% [+ or -] 5.7%, P < .001) and walking (21.8% [+ or -] 8.7% vs 18.5% [+ or -] 2.7%, P < .001), and a smaller percentage of time standing (24.0% [+ or -] 7.3% vs 33.5% [+ or -] 4.8%, P<.001) and running (5.4% [+ or -] 3.2% vs 5.9% [+ or -] 1.5%, P=.034) than recruits at Fort Sill.

Over the course of BCT, recruits at Fort Jackson reported spending less time sleeping each night than recruits at Fort Sill (364.7 [+ or -] 41.1 minutes/night vs 376.6 [+ or -] 17.5 minutes/night, P < .001). Recruits at Fort Jackson also reported spending a larger percentage of time doing chores (4.5% [+ or -] 2.8% vs 3.8% [+ or -] 1.3%, P=.002), performing calisthenics (10.0% [+ or -] 7.7% vs 8.6% [+ or -] 2.5%, P=.006) and carrying loads (16.9% [+ or -] 12.8% vs 7.9% [+ or -] 2.4%, P <.001) than recruits at Fort Sill.

Over the course of BCT, recruits at Fort Jackson reported spending less time sleeping each night than recruits at Fort Sill (364.7 [+ or -] 41.1 minutes/night vs 376.6 [+ or -] 17.5 minutes/night, P<.001). Recruits at Fort Jackson also reported spending a larger percentage of time doing chores (4.5% [+ or -] 2.8% vs 3.8% [+ or -] 1.3%, P =.002), performing calisthenics (10.0% [+ or -] 7.7% vs 8.6% [+ or -] 2.5%, P =.006) and carrying loads (16.9% [+ or -] 12.8% vs 7.9% [+ or -] 2.4%, P<.001) than recruits at Fort Sill.

COMMENT

To the best of our knowledge, this study was the first to characterize and quantify the amount of PA recruits actually perform during BCT conducted at 2 different training sites. The results of this study revealed that although there were some differences between the 2 sites in terms of the PA performed, these differences were importance. Furthermore, it appeared that the intensity and types of PA were similar at the 2 sites.

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Quantification of Physical Activity

The major purpose of this study was to characterize and quantify the PA performed by recruits during the middle 8 weeks of BCT and determine whether or not there were differences in PA between the training sites. The PA performed by recruits was characterized and quantified using accelerometry, direct observation, and daily PA logs. Despite statistical significance, the differences in PA observed between the 2 BCT sites were small. The magnitude of the differences between sites can be appreciated by examining the range of differences (lowest and highest) in the amount of time recruits spent in various physical activities. From the accelerometer, the lowest difference was 7% (3.4 minutes) for sedentary activities, and the highest difference was 7.2% (67.8 minutes) for light-intensity activities. From the PAtracker, the lowest difference between the 2 training sites was 0.4% (2 minutes) for running, and the highest difference was 15.3% (93.7 minutes) for menial tasks. From the PA log, the lowest difference between the 2 training sites was 0.5% (7.2 minutes) for running and 9.0% (50.3 minutes) for carrying loads. This result suggests that Army BCT recruits spent similar amounts of time in each PA intensity, activity type, body position, and carrying various external loads at the 2 locations tested. Whether or not this result applies to all BCT sites will need to be determined with future studies.

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In terms of intensity, the results of this study were the same regardless of the technique used to measure PA intensity (for example, accelerometer or direct observation). Recruits at both training sites spent a very large percentage of time sedentary (about 80%) and a very small percentage of time in vigorous-intensity activities (about 5%). Between the training sites, there was little difference in the percentage of time recruits spent in moderate- or vigorous-intensity PA. These results further support the idea that the intensity of PA at each training site was similar.

External loads carried by recruits were obtained from direct observation (PAtracker). Recruits from both training sites spent a very large percentage of time (roughly 80%) either unloaded or carrying very light loads (0-10 lbs) and a very small percentage of time carrying loads weighing over 50 lbs (1%-2%). During their military service, Soldiers may be expected to carry extremely heavy loads for long distances over various types of terrain. (27) Current US Army doctrine recommends that Soldiers carry no more than 48-72 lbs (or 30%-45% of their body weight) in the fighting load and approach march loads, respectively. (28,29) Recruits at both training sites had some training in heavy loads, providing further evidence that the PA performed at each training site was similar.

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Using the daily PA log, recruits from both training sites reported getting an average of about 6 hours of sleep each night. Current Army doctrine mandates that recruits be given the opportunity to receive 7 hours of continuous sleep each night while in garrison unless they are scheduled for duty. (20) The results of this study suggest that although they may be allowed the full 7 hours, BCT recruits at both training sites reported getting slightly less than the recommended amount of sleep. Additionally, the self-reported amount of sleep in this study is similar to the results of a previously published study in which US Military Academy cadets reported receiving an average of 5 hours and 40 minutes of sleep per night during the 6 weeks of cadet basic training. (30) The current study's findings indicate that recruits received the same, or similar, amounts of recovery time regardless of the training site to which they were assigned.

Physical Training Intensity and Type

The second purpose of this study was to examine the intensity and types of physical training over the course of BCT. Intensity was examined to determine whether the principle of progressive training (progressive overload), one of the major principles of PRT, was being followed. (31) The PRT program consists of a variety of standardized exercises (such as preparatory drills, conditioning drills, movement drills, climbing drills, interval running, long distance running, and flexibility training) and is designed to progressively train Soldiers while reducing the risk of developing injuries. (2,19)

The results of this study show time spent in moderate- to vigorous-intensity PA between 5AM and 7AM (when recruits were presumably engaged in PRT) tended to increase during the first 4 weeks of BCT at Fort Jackson (Figure 2). Although there was no significant difference in the weekly moderate- to vigorous-intensity activity at Fort Sill, the graph does show a gradual increase, the slope of which is much lower than that shown for Fort Jackson. This suggests some increase in exercise intensity but perhaps not enough to be consistent with the progressive overload principle. After week 4 (Fort Jackson) or week 7 (Fort Sill), the amount of time recruits spent in moderate- to vigorous-intensity PA from 5 AM to 7 AM at both training sites tended to decrease. This decrease could be related to increased time spent in military operations (road marching, basic rifle marksmanship, land navigation, field training exercises, etc). When physically demanding activity was scheduled, physical training was either reduced or was not conducted at all in the early morning. The more physically demanding operational soldiering tasks are generally conducted later in training. Over the course of the 8-week BCT monitoring period, the average daily percentage of time recruits spent engaging in calisthenics was not significantly different between the training sites. The average daily time spent running differed slightly; however, this difference was not large. Although we cannot determine from these data if the specific drills of PRT were followed, it appears that the amount of time spent in these general activities was similar at the 2 sites.

Strengths and Limitations

This study was limited by the fact that recruits were only observed during the middle 8 weeks of training as opposed to the entire 10 weeks. Eliminated were the first week of BCT, which consists mostly of classroom training; and the final week, consisting primarily of cleaning equipment, completing paperwork, and preparing for graduation. We also did not monitor the evening activities of the recruits (after the evening meal, generally after 1800). Thus, we missed some of the activities performed by recruits, but previous observations suggested that there was little PA taking place in the evening hours. (1,3)

Due to limited personnel and resources, we were unable to instrument and observe all recruits in each training company. Therefore, the PA performed by the 24 recruits per company who were instrumented with an accelerometer and the 1 recruit per company who was followed and observed using the PAtracker was assumed to be representative of the PA performed by all recruits in each respective company.

If a recruit wearing an accelerometer or being observed using the PAtracker was sick, injured, or not training with his or her company that day for any reason, that recruit was immediately replaced with another consented volunteer. Due to study design, a limitation to this process was the number of times recruits had to be replaced, which was not tracked. However, since recruits were immediately replaced, the appropriate number of accelerometers was always distributed, and one recruit per company was observed. Therefore, data was never lost due to attrition.

This study also used multiple methods of measuring PA, including accelerometry, direct observation, and self-report questionnaires, all of which allowed study investigators to capture a good quality representation of the PA actually performed by recruits during BCT. Additionally, the standardization of activities during BCT enabled investigators to ensure that recruits filled out the daily PA log each day.

RELEVANCE TO PERFORMANCE TRIAD

The Army Surgeon General's Performance Triad initiative seeks to improve Soldier readiness and resiliency by improving the activity, sleep and nutritional aspects of Soldier health behaviors. This study examined the activity and sleep aspects of the Performance Triad. Physical activity is an important variable to support health and improve performance. It is important to document the physical demands of the training program followed during BCT in order to ensure that the activities performed are sufficient for developing the Soldier's fitness, but not so excessive that the demands lead to the development of musculoskeletal injuries, a key barrier to individual and unit readiness. Additionally, these data suggest recruits during BCT are meeting the minimum PA recommendations for healthy adults set forth by the American College of Sports Medicine. (32)

In terms of sleep, these data suggest that recruits are receiving slightly less than the recommended 7-8 hours per night during BCT, despite being allotted 7 hours each night to devote to sleep. This lack of rest and recovery during BCT may adversely impact a recruit's ability to perform his or her job sufficiently and maintain adequate health and resiliency.

ACKNOWLEDGEMENT

This study was funded by the US Army Medical Research and Materiel Command and the Defense Safety Oversight Council.

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Kathleen Simpson, MS

Jan E. Redmond, PhD

Bruce S. Cohen, PhD

Nathan R. Hendrickson, MS

Barry A. Spiering, PhD

Ryan Steelman, MS

Joseph J. Knapik, ScD

Marilyn A. Sharp, MS

AUTHORS

Ms Simpson, Dr Redmond, Dr Cohen, Mr Hendrickson, and Ms Sharp are in the Military Performance Division of the US Army Research Institute for Environmental Medicine, Natick, Massachusetts.

Dr Spiering is a Senior Physiologist for the Nike Sport Research Lab, Beaverton, Oregon.

Dr Knapik and Mr Steelman are at the US Army Institute of Public Health, US Army Public Health Command, Aberdeen Proving Ground, Maryland.
Table 1. Cumulative time recruits at both training sites spent in
each Activity Intensity category measured by the ActiGraph during a
Basic Combat Training cycle. Days represent the total number of days
recruits spent in an intensity at least once.

                                    Fort Jackson
Days Recorded                            47

Total Time          28,256.2 [+ or -] 1,458.5/5470.9 [+ or -] 24.3
Recorded
(minutes/
hours)
             Days      Time (minutes)           Time (hours)

Sedentary     47    20,847.5 [+ or -] 702.7   347.5 [+ or -] 11.7
Light         47     8,193.6 [+ or -] 512.8   136.6 [+ or -] 8.5
Moderate      47     4,799.5 [+ or -] 360.8    80.0 [+ or -] 6.0
Vigorous      47     1,602.0 [+ or -] 313.2    26.7 [+ or -] 5.2

                                     Fort Sill
Days Recorded                            44

Total Time          29,597.6 [+ or -] 596.2/493.3 [+ or -] 9.9
Recorded
(minutes/
hours)
             Days      Time (minutes)              Time (hours)

Sedentary     44    19,667.7 [+ or -] 1,558.6   327.8 [+ or -] 26.0
Light         44     4,687.6 [+ or -] 217.3      78.1 [+ or -] 3.6
Moderate      44     3,624.3 [+ or -] 357.6      60.4 [+ or -] 6.0
Vigorous      44     1,827.4 [+ or -] 207.9      30.5 [+ or -] 3.5

Table 2. Cumulative time recruits at both training sites spent in
each body position, activity type, activity intensity, and carrying
each external load, as measured by the PAtracker during a Basic
Combat Training cycle. Days represent the total number of days
recruits participated in each body position, activity type and
intensity, and carried each load at least once.

                                Fort Jackson
Days Observed                        47

Time Observed            36,463.2 [+ or -] 8,444.3/607.7
(minutes/hours)          [+ or -] 140.7

                  Days   Time (minutes)

Body Position
  Kneeling         34    409.2 [+ or -] 172.7
  Lying            37    1,071.8 [+ or -] 284.0
  Sitting          47    13,187.2 [+ or -] 1,193.8
  Standing/        47    19,216.3 [+ or -] 476.2
    On Feet
  Varying          41    2,578.6 [+ or -] 344.2

Activity Type
  Cadence March    39    1,195.6 [+ or -] 325.0
  Calisthenics     38    1,391.9 [+ or -] 146.6
  Combatives       12    559.6 [+ or -] 155.3
  Crawl             7    63.4 [+ or -] 75.2
  Lifting/         12    71.1 [+ or -] 50.4
    Carrying
  Menial Tasks     47    7925.0 [+ or -] 495.2
  Obstacle/         7    181.0 [+ or -] 55.7
    Climbing
  Run              33    427.7 [+ or -] 91.1
  Stationary       47    20,402.9 [+ or -] 1,510.9
  Walk             47    4,244.9 [+ or -] 720.9

Intensity
  Sedentary        47    19,995.7 [+ or -] 2902.8
  Light            47    13,126.8 [+ or -] 1325.2
  Moderate         44    2,975.9 [+ or -] 1333.2
  Vigorous         25    360.6 [+ or -] 105.0

External Load
  0-10 lbs         47    30,533.1 [+ or -] 2282.2
  10-25 lbs        36    4,585.4 [+ or -] 1461.4
  25-50 lbs        19    1,266.6 [+ or -] 588.3
  50-75 lbs         4    70.0 [+ or -] 57.0
  >75 lbs           3    8.0 [+ or -] 11.2

                          Fort Jackson
Days Observed                 47

Time Observed            36,463.2 [+ or -] 8,444.3/607.7
(minutes/hours)          [+ or -] 140.7

                  Days   Time (hours)

Body Position
  Kneeling         34    6.8 [+ or -] 2.9
  Lying            37    17.9 [+ or -] 4.7
  Sitting          47    219.8 [+ or -] 19.9
  Standing/        47    320.3 [+ or -] 7.9
    On Feet
  Varying          41    43.0 [+ or -] 5.7

Activity Type
  Cadence March    39    19.9 [+ or -] 5.4
  Calisthenics     38    23.2 [+ or -] 2.4
  Combatives       12    9.3 [+ or -] 2.6
  Crawl             7    1.1 [+ or -] 1.3
  Lifting/         12    1.2 [+ or -] 0.8
    Carrying
  Menial Tasks     47    132.1 [+ or -] 8.3
  Obstacle/         7    3.0 [+ or -] 0.9
    Climbing
  Run              33    7.1 [+ or -] 1.5
  Stationary       47    340.0 [+ or -] 25.2
  Walk             47    70.7 [+ or -] 12.0

Intensity
  Sedentary        47    333.3 [+ or -] 48.4
  Light            47    218.8 [+ or -] 22.1
  Moderate         44    49.6 [+ or -] 22.2
  Vigorous         25    6.0 [+ or -] 1.7

External Load
  0-10 lbs         47    508.9 [+ or -] 38.0
  10-25 lbs        36    76.4 [+ or -] 24.4
  25-50 lbs        19    21.1 [+ or -] 9.8
  50-75 lbs         4    1.2 [+ or -] 0.9
  >75 lbs           3    0.1 [+ or -] 0.2

                            Fort Sill
Days Observed                  44

Time Observed            30,367.2 [+ or -] 8,884.3/506.1
(minutes/hours)          [+ or -] 148.1

                  Days   Time (minutes)

Body Position
  Kneeling         37    602.5 [+ or -] 252.2
  Lying            37    943.0 [+ or -] 184.9
  Sitting          44    9,374.1 [+ or -] 1,056.5
  Standing/        44    19,447.6 [+ or -] 1,752.5
    On Feet
  Varying          NA    NA

Activity Type
  Cadence March    40    1,414.6 [+ or -] 210.3
  Calisthenics     39    1128.4 [+ or -] 46.5
  Combatives        4    113.5 [+ or -] 75.9
  Crawl             5    16.5 [+ or -] 7.2
  Lifting/         13    97.8 [+ or -] 62.8
    Carrying
  Menial Tasks     44    11,335.9 [+ or -] 2,180.3
  Obstacle/         8    302.4 [+ or -] 38.8
    Climbing
  Run              31    479.7 [+ or -] 58.8
  Stationary       44    12,871.7 [+ or -] 2,922.4
  Walk             44    2,606.8 [+ or -] 435.2

Intensity
  Sedentary        44    14,604.6 [+ or -] 3,835.6
  Light            44    13,506.0 [+ or -] 3,380.0
  Moderate         40    2,018.7 [+ or -] 238.1
  Vigorous         18    238.0 [+ or -] 151.3

External Load
  0-10 lbs         44    24,323.4 [+ or -] 859.1
  10-25 lbs        28    2,869.6 [+ or -] 1,416.3
  25-50 lbs        30    2,796.2 [+ or -] 628.6
  50-75 lbs         7    322.1 [+ or -] 226.8
  >75 lbs           4    55.9 [+ or -] 68.3

                           Fort Sill
Days Observed                 44

Time Observed            30,367.2 [+ or -] 8,884.3/506.1
(minutes/hours)          [+ or -] 148.1

                  Days   Time (hours)

Body Position
  Kneeling         37    10.0 [+ or -] 4.2
  Lying            37    15.7 [+ or -] 3.1
  Sitting          44    156.2 [+ or -] 17.6
  Standing/        44    324.1 [+ or -] 29.2
    On Feet
  Varying          NA    NA

Activity Type
  Cadence March    40    23.6 [+ or -] 3.5
  Calisthenics     39    18.8 [+ or -] 0.8
  Combatives        4    1.9 [+ or -] 1.3
  Crawl             5    0.3 [+ or -] 0.1
  Lifting/         13    1.6 [+ or -] 1.0
    Carrying
  Menial Tasks     44    188.9 [+ or -] 36.3
  Obstacle/         8    5.0 [+ or -] 0.6
    Climbing
  Run              31    8.0 [+ or -] 1.0
  Stationary       44    214.5 [+ or -] 48.7
  Walk             44    43.4 [+ or -] 7.3

Intensity
  Sedentary        44    243.4 [+ or -] 63.9
  Light            44    225.1 [+ or -] 56.3
  Moderate         40    33.6 [+ or -] 4.0
  Vigorous         18    4.0 [+ or -] 2.5

External Load
  0-10 lbs         44    405.4 [+ or -] 14.3
  10-25 lbs        28    47.8 [+ or -] 23.6
  25-50 lbs        30    46.6 [+ or -] 10.5
  50-75 lbs         7    5.4 [+ or -] 3.8
  >75 lbs           4    0.9 [+ or -] 1.1

Table 3. Cumulative time (mean [+ or -] SD) recruits at both
training sites spent in various physical activities, as
reported on the daily PA logs during a Basic Combat Training
cycle. Days represent the total number of days recruits
participated in each variable at least once.

                                     Fort Jackson
Days Self-reported                       47

Time Self-reported     28256.2 [+ or-] 1458.5 / 470.9 [+ or-] 24.3
(minutes/hours)

                Days   Time (minutes)             Time (hours)

Sit              47    13,672.7 [+ or-] 1,620.9   227.9 [+ or -] 27.0
Stand            47    6,848.0 [+ or-] 743.8      114.1 [+ or -] 12.4
Walk/March       47    6,204.5 [+ or-] 1,204.6    103.4 [+ or -] 20.1
Run              47    1,531.0 [+ or-] 263.6      25.5 [+ or -] 4.4
Sleeping         47    17,140.7 [+ or-] 985.7     285.7 [+ or -] 16.4
Chores/          43    1,256.7 [+ or-] 323.4      20.9 [+ or -] 5.4
Maintenance
Calisthenics/    45    2,795.5 [+ or-] 669.0      46.6 [+ or -] 11.2
  Obstacle
  Course
Carrying Load    46    4,857.8 [+ or-] 1,738.4    81.0 [+ or -] 29.0

                                           Fort Sill
Days Self-reported                            44

Time Self-reported     29597.6 [+ or -] 596.2 / 493.3 [+ or -] 9.9
(minutes/hours)

                Days   Time (minutes)              Time (hours)

Sit              44    12,430.8 [+ or -] 1,296.4   207.2 [+ or -] 21.6
Stand            44    9,907.6 [+ or -] 1,233.9    165.1 [+ or -] 20.6
Walk/March       44    5,506.4 [+ or -] 392.2      91.8 [+ or -] 6.5
Run              44    1,752.8 [+ or -] 238.9      29.2 [+ or -] 4.0
Sleeping         44    16,569.4 [+ or -] 567.7     276.2 [+ or -] 9.5
Chores/          44    1,135.4 [+ or -] 321.5      18.9 [+ or -] 5.4
Maintenance
Calisthenics/    44    2,532.8 [+ or -] 473.7      42.2 [+ or -] 7.9
  Obstacle
  Course
Carrying Load    44    2,336.0 [+ or -] 289.2      38.9 [+ or -] 4.8
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Author:Simpson, Kathleen; Redmond, Jan E.; Cohen, Bruce S.; Hendrickson, Nathan R.; Spiering, Barry A.; Ste
Publication:U.S. Army Medical Department Journal
Article Type:Report
Geographic Code:1USA
Date:Oct 1, 2013
Words:7463
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