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Warfighter load, survivability, and shoot-and-move dynamics.

"On the field of battle man is not only a thinking animal, he is a beast of burden. He is given great weights to carry. But unlike the mule, the jeep, or any other carrier, his chief function in war does not begin until the time he delivers that burden to the appointed ground. It is this distinction that makes all the difference. For it means that the logistical limits of this human carrier should not be measured in terms of how much cargo he can haul without permanent injury to bone and muscle, but what he can endure without critical, and not more than temporary, impairment of his mental and moral powers. If he is to achieve military success and 4110 personal survival, his superiors must respect not only his intelligence but also the delicate organization of his nervous system."

--S.L.A. Marshall

The Soldier's Load and the Mobility of a Nation, 1949


The consequences of warfighter load have been discussed and debated for thousands of years, as have the trade-offs between "up-armoring" and "agility and flexibility" as the means to lethally engage and defeat the enemy in close combat. Survivability in combat is more than armor and helmets; it is also allowing the warfighter the adaptability and flexibility to perform necessary actions for lethal engagement and quickly get to cover and concealment. These actions require situational awareness to detect and discriminate targets and to quickly find what terrain supports cover and concealment. In short, it requires the optimization of a warfighter's action-perception capabilities within some level of ballistic protection and a mission-specific "fire load." A warfighter's ability to maintain situational awareness and accurately engage the enemy transfers directly to the survivability and mobility of the squad and the ability to execute collective tasks. This type of survivability can't be quantified in terms of how many bullets a plate may stop, the fragmentation protection of soft armor, or "back face deformation" measured in millimeters after shooting a plate. This type of survivability means the enemy round never reaches its intended target--the U.S. warfighter. At issue is not a debate about the need for armor or fire load but the understanding and quantification of this trade-off in operational terms (e.g. how much slower and less accurate is the warfighter in equipment configuration X vs. Y, and why?). Where is the U.S. warfighter along this continuum of the protection-lethality-mission effectiveness trade-off? How can empirical study of warfighter performance for actions on the objective provide additional insight into what senior NCOs and company commanders already know from their experience in combat? These are the questions central to this article, and I will attempt to provide initial answers in terms of operational consequences from recent research conducted on shoot-and-move dynamics.

In 1944, the U.S. Army conducted an early study of load to look at backpack positions on different-sized Soldiers while standing. Since then, research has been conducted on the consequences of load on energy expenditure during road marching, the biomechanics and forces involved in injury, and some levels of task performance (obstacle course times, limited marksmanship, etc). Most of this research addresses the consequences of load on road-marching performance, energy expenditure, and hydration requirements during locomotion, etc. Much less research has been conducted from a true operational perspective. For example, warfighters in operational conditions scan their environments for potential threats while road marching. This requires a shift in thinking from road marching as the study of "loaded locomotion" to "on-the-move threat identification and discrimination," which leads to completely different questions about the consequences of load on visual performance. It's not that energy expenditure is unimportant; the point is only that an operational mindset is required for our questions to be more relevant to warfighters and ensuring scientists have an operational "so what" to answer.

The purpose of this article is two-fold. First and foremost, it directly communicates initial results about the consequences of load on shoot-and-move dynamics to those warfighters engaged in combat and making decisions that affect the survivability and mission effectiveness of the subordinates they serve. The second purpose is to contrast "up-front" survivability with the survivability of ballistic protection, and bring to the surface an argument that requires an understanding of both aspects of survivability to optimize warfighter performance, survivability, and mission effectiveness. U.S. warfighters carry more than ever before, and much of that load has been fielded with the specific intent of increasing survivability. Common sense tells us that sometimes too much load can not only injure a warfighter, but it can make him slower, less effective, more fatigued, and less aware of his tactical surroundings. This can certainly lead to an increased likelihood of being wounded or killed by the enemy and has serious consequences for the accomplishment of collective tasks and mission success. What hasn't been quantified is how load affects warfighters' functional capabilities during shoot-and-move dynamics. In 2008, an attempt to "operationalize" science for a more relevant understanding of load during actions on the objective was initiated. Speed/ accuracy trade-offs, visual perception, head-gun-trunk coordination, and postural control were assessed to try to provide an understanding of the consequences of equipment distribution on the lethality, mobility, and situational awareness of warfighters.

Redefining Survivability

The term survivability--at least in the halls of those working material solutions (program managers, requirements generators, etc.) and Congress--is most often in terms of armor and where it should be placed. This aspect of survivability, while easily measured, isn't complete in an operational sense. In fact, this definition is best described as "after you've already been shot" survivability, as its focus is on how material solutions can stop enemy fire of all types. There is another important aspect of survivability--up-front survivability, which minimizes the chance of being shot in the first place. To understand this survivability, we must understand the consequence of load and its distribution on the ability of the warfighter to perceive threats and take efficient action given the circumstances. This type of survivability is much more closely related to an offensive operational posture and is defined within the relations between lethality, mobility, and situational awareness (Figure 1). All three are interconnected; situational awareness is necessary for mobility and lethality, and lethality allows the individual and squad to move more freely to perceive more about the ongoing situation during shoot-and-move dynamics. This requires us to conduct research in a way that does not attempt to separate the study of lethality, mobility, and situational awareness (e.g. break them apart by studying locomotion as mobility), since we are only interested in the mobility and situational awareness of lethality and vice versa. While a warfighter's common sense and personal understanding of this issue is beyond question, we do not have a good handle on how much these capabilities are degraded under load. Quantifying the reduction in operational performance and understanding why this occurs with certain loads are the purposes of the initial investigation into shoot-and-move dynamics.


Consequences of Load on Shoot-and-Move Dynamics

The following is a limited summary of three different studies used to understand the consequences of load on actions on the objective and comes from the understanding that consequences of load on the warfighter are best understood within the tenants of shoot, move, and communicate. From this perspective, marksmanship can't be studied during static range performance and must be nested in dynamic movement that warfighters are engaged in during a firefight. Marksmanship must be dynamic and must involve the transition from movement to a static upright posture that provides the foundation for quick and accurate fire on the enemy. The following efforts sought to replicate these conditions as best as possible within the laboratory environment, and while no lab conditions are the same as combat, they provide a sound basis to understand the consequences of load. If these consequences are operationally significant in the laboratory, then they can only be further degraded in real operations (difficult terrain, fatigue, stress, loss of sleep, etc.).



All configurations used real or mock equipment of the same size, weight, and shape and were loaded within general operational practices. When this study started, operational data suggested an average load of around 90 pounds for the Infantryman in theater. Load has increased since then, which can only make the findings below move in a direction of poorer performance as this will not improve with more weight in any case. All loaded configurations were compared to an unloaded baseline that included the M4 Carbine or a lighter load defined below. The unloaded configuration provides information about the overall degradation in performance "from optimal" as well as a general comparison to a relatively unloaded enemy. There were three primary loads (all with helmet):

1) Vest--Ballistic vest with soft inserts, plates and a basic fire load (six magazines, two fragmentation grenades, two 40mm grenades as distributed squad equipment, radio, battery, etc.)

2) Standard--Vest condition plus a light assault pack with additional fire load to represent extended patrols, heavier direct action missions, or operations that require any additional kit carried in an assault pack

3) Light--Same as the standard load except every piece of equipment was two-thirds the weight of standard

The vest load had the majority of weight on the front (magazines, fragmentation grenades, etc.) and less on the back, making it front heavy. The light load provided an idea of what could be gained with either advanced technology at lighter weight or unloading the warfighter in other ways (e.g. accepting greater risk because of the up-front survivability gained). Two additional smaller loads were added to the standard configuration to understand the impact of loading the head and arms/gun for visual perception and performance (target or threat identification and precision aiming). These two configurations added PVS-7 night vision goggles (NVGs) to the helmet (+1.5 pounds) or upper extremity (UE) armor to the forearms and upper arms in a way that didn't interfere with range of motion (+4.1 pounds).

Move to Shoot Transition I: Establishing Upright Posture

There are many ways to stop and establish marksmanship postures. In order to keep the type of transition consistent and the effects of load clear, a landing task was used to evaluate the consequences of load on target discrimination, head orientation and field of view (situational awareness), and the adaptability and flexibility of warfighters under different loads to perform transitions after landing (e.g. fire a weapon, change direction, etc.). This task was only meant to generalize the consequences of load on dynamic transitions and specifically get at questions involving how the human controls the weight and distribution when establishing upright posture (as in marksmanship). As weight was increased, it took the warfighters longer to discriminate the highest threat target, and head velocity increased every time the load increased. This provided direct evidence that one of the consequences of load is the delay in threat identification and discrimination (situational awareness) during dynamic movement transitions, which occur all the time in combat. Specifically, this relates to the inability of the human system to control the load when stopping to acquire targets and shoot. This uncontrolled force and shock moves up the body and reaches the head and eyes, disrupting situational awareness.

In addition to the reduction in situational awareness, load also significantly increased the downward head angles during the entire task, which reduced the total field of view for the warfighters (Figure 3). This was the first time that it was shown to occur during transitions to upright postures necessary for marksmanship, and the effect was consistent even when the final upright postures were established. Another important finding was that the vest configuration's performance was much worse (for downward head angles and field of view loss) than the heavier standard configuration, despite being 23 pounds lighter. This clearly shows that it is not just the weight that has negative effects, but that uneven loading of equipment (front loaded in this case) can be more important to situational awareness and visual performance necessary for survival. The final important measure when transitioning under different loads was the adaptability and flexibility of the warfighters--the ability to rapidly react and move based on the situation at hand. The results of these measures suggested that the vest and standard configurations were equally constraining for warfighter adaptability, further supporting the idea that all different configurations of load should (within operational realities involving access to crucial equipment) be spread as evenly as possible over the warfighter for optimal adaptability and up-front survivability.


Move to Shoot Transition II: Speed/ Accuracy Trade-offs and Coordination

To understand the consequences of load on speed/accuracy trade-offs in more realistic terms, two targets were used. One target was immediately in front of the warfighters (forward posture), and the other was an overhead target that was up and to the left of the warfighters (high posture). The high target was added for a more realistic transition, as the forward target required large gun movement but only small trunk and head movements. The high target also provided insight into the constraints of load on more difficult postures for marksmanship, like those in the mountains of Afghanistan or the urban environments in Iraq, adding the challenge of high-angle combat shooting. The simulated target distance used in this task was approximately 65 meters and a confined range target was used. Instructions were to shoot as fast and accurately as possible. Note: The accuracy measures in Figure 4--in millimeters (mm)--are not at the 65-meter distance and provide a relative loss of performance that can be extended to any distance within reason. Higher values indicate less accurate performance (farther from center of target).



Speed and accuracy were both degraded with the addition of load; the smaller extremity loads had significant impacts on lethality, and higher targets further degraded marksmanship accuracy. Specifically, accuracy was reduced by 18.1 percent when UE armor was added and an additional 31.6 percent when NVGs were added to the helmet. Firing latency (time to trigger pull) was increased by about 0.1 seconds with the standard load, and extremity armor added another 0.1 seconds. The NVGs added an additional quarter of a second. When the time to discriminate threats was added to this, warfighters appeared to lose more than a quarter of a second per individual engagement under load and more than half a second when additional weight was added to the helmet or upper extremity. The poor performance in all load configurations at all the high targets is troubling, and it is hard to tell if this is a training issue or simply what happens when very difficult postures have to be established quickly during shoot-and-move dynamics. In a different study, the standard load at the high target condition reduced accuracy by about 40 percent compared to the light and standard loads at the forward target, again showing the consequences of heavier loads on high-angle shooting. The little historical research that has been done on dynamic marksmanship has primarily been in the form of "ready up" drills similar to the forward target condition here. This is a less operationally applicable condition, as in most cases the target is not directly in front of you or is moving. Both of these scenarios require the type of significant postural transitions (head, gun, and trunk) as seen in the high target condition. Research is ongoing to better understand this, as well as the effects of weapons loading on shoot-and-move dynamics that will allow operational decisions on the technology trade-offs when added to the weapon.

The consequences of load on head-trunk-gun coordination reflected the reduction in performance of speed/accuracy, as they showed that the large loads on the trunk significantly degraded coordination of movement from the initial positions to the final marksmanship posture on target. Once this final posture was established, the large loads on the trunk did not degrade fine-aiming performance, but they did not help either. This debunks the myth that additional load may dampen vibration in the system and helps improve accuracy performance in true dynamic marksmanship performance. This may or may not be true in range studies when all the time in the world is available and static postures are easily established; however, it is certainly not true in more dynamic and realistic marksmanship performance. Equally important is the finding that smaller loads on the head and arms significantly disrupted the fine-aiming portion of dynamic marksmanship by further delaying the time it takes to re-acquire the target and fire accurately (less than accurately, given the above data). The bottom line on the head-gun-trunk coordination findings is that large loads have negative effects on large transitions and smaller loads have negative effects on fine-aiming performance, both of which are necessary for lethality. This finding shows that in each phase of dynamic marksmanship performance, the weight of the carried items "pull" the head-gun-trunk relations from their optimal performance, resulting in longer time to trigger pull and less accurate performance. This has serious implications for requirements generators as well as for developers of advanced equipment that is placed on either the gun or head (e.g. future concepts of heads-up displays and weapons technology). In case there were any questions that we should not place additional weight on the head (visual system performance for target ID and the fine skill of aiming) or arms/gun, we now have data that substantiates that this "not so common sense" approach significantly reduces the effectiveness of shoot-and-move dynamics.


This article provides initial but substantial support as to why the Army must look toward "operationalizing" science for the warfighter in its approach to lighten the load (Figure 5 summarizes all findings). This approach gives initial insight and quantifies the effects of equipment technology and employability in the hands of the warfighter, and significantly expands the understanding from only the capabilities of the technology itself. At its heart, this approach can provide insight for operational commanders and senior NCOs about the different configurations and loading of the warfighter during shoot-and-move dynamics, It can also provide specific warfighter key performance parameters (KPPs) relevant to survivability and mission effectiveness that can be traded against technical KPPs currently used in requirement documents before fielding new equipment. These findings are just a beginning but suggest that operationally and scientifically relevant metrics are both necessary to address how to best optimize warfighter lethality, mobility, and situational awareness in combat. The problem of load is not a simple one, and warfighters can't be seen as machines that must be made stronger to carry more equipment. This approach will surely fail the warfighter in terms of their immediate operational capability, probability of acute injury, and long-term consequences for permanent disability. The findings show that issues of equipment distribution on the warfighter are as significant as the weight itself, and that weight is not the only consideration for operational "so what" questions. Expansions of current efforts are underway to broaden the current paradigm to "on-the-move threat ID and discrimination" using load weights and configurations that are more current (85-125 pounds). Future efforts will incorporate fatigue effects and communication tasks so that all aspects of "shoot-move-communicate" can be combined for an operationally relevant and scientifically feasible approach.
Pre-Shoot Measure Outcome/ "So What"

Mobility Flexibility to Change Reduced flexibility to
 Posture change posture during
 transition to upright
 stance. Load makes it
 significantly harder
 to be "adaptive" to
 environment. Equal
 between vest and
 heavier standard
 condition, showing the
 negative consequences
 of front loading of
 the torso.

 Field of View Loss Loss of field of view
 reduces the ability to
 pickup targets and
 threat information.
 Greater loss in the
 lighter but more
 forward-loaded vest

Situational Head Orientation Greatest downward head
Awareness orientation in the
 vest configuration,
 better performance in
 the standard condition
 showing the value of
 equally loading the
 torso to situational

 Time to Discriminate Reduced with both
 light and standard
 greatest in the
 configuration. Reduced
 capability to
 discriminate targets,
 identify friend vs
 foe, threats, etc.

Shooting Measure Outcome/"So What"

Mobility Head-Gun-Trunk Heavier loads on the
 Coordination torso disrupted
 postural transitions
 to final shooting
 position by "pulling"
 segments away from
 their regular

Lethality Firing Latency Smaller loads on the
 head and gun further
 disrupted coordination
 during fine aiming
 phase and delayed
 trigger pull. This
 delay was extended for
 high-angle shooting

Lethality Firing Latency All increases to
 standard loads delayed
 trigger pull. The
 light load (~ 55
 pounds) did not appear
 to delay firing.
 Adding NVGs and upper
 extremity (UE) armor
 delayed trigger pull
 further. High-angle
 targets increased all

 Accuracy Accuracy was degraded
 with the addition of
 the standard load, and
 even further by the
 addition of the NVGs
 and UE armor.
 High-angle shooting
 reduced accuracy
 further in all

Figure 5--Summary of Findings

Christopher Palmer recently completed Army long-term training specifically aimed at finding a better way operationalize shoot-and-move dynamics using the science available in the fields of motor control, biomechanics, and ecological psychology. He is attempting to build an "up-front" survivability model from real warfighter data that is based on the changes in lethality, mobility, and situational awareness that accompany load. This work was partially supported by the Office of Naval Research. Palmer has served as a military performance expert and scientist, operational requirements generator, program manager, and technology developer in the Army, Navy, Marine Corps, and Special Operations Command. He is indebted to the NCOs and junior officers with whom he has served for their mentoring and guidance. He currently serves at the Natick Soldier Research Development and Engineering Command in the Human Sciences and Integrated Systems Division.
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Author:Palmer, Christopher
Publication:Infantry Magazine
Date:Apr 1, 2012
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