Page 81 - Journal of Special Operations Medicine - Spring 2014

pull-ups (by 61%), hang time (by 63%), and stair step- of motion decreased and trunk transverse range of mo-
ping (by 16%), but no effect was seen on grip strength. tion increased when carrying a rifle. During the walking
43
An additional finding of interest is the significant in- task, carrying the rifle decreased sagittal plane range of
crease in VO consumption in the trials with body motion. No significant effects were detected on pelvis
2
armor. Influence of protective vests on physical perfor- range of motion for the rifle condition in either the run-
43
mance was studied by Hasselquist and colleagues and ning or walking test. Since military personnel can carry
48
DeMaio and colleagues. Hasselquist et al. studied the loads upwards of 68kg, a study by Rodriguez-Soto and
impact on physical performance and exertion for four colleagues used magnetic resonance images to investi-
test conditions: wearing a 8.7kg tactical vest and three gate the changes in lumbar spine kinematics resulting
upper extremity armor configurations of similar weight, from carrying heavy loads. Significant differences were
but varying surface area coverage. Gait adaptations, detected in the “loaded” test conditions, with varying
44
decreased performance (increased completion time for responses of the superior and inferior levels of the lum-
sprints and obstacle courses and reduced number of box bar spine evident under the heavy load. These responses
lifts), and increased Vo consumption were all associ- resulted in an overall reduced lordosis of the lumbar
2
ated with the three extremity armor configurations for spine. While much of the impact of these kinematic
49
the maximal effort tasks analyzed. 44 changes on risk of injury is unknown, additional work
is needed to understand how design changes within both
DeMaio et al. investigated the effect of a protective vest PPE and combat equipment can minimize the kinematic
on physical performance during cardiopulmonary ex- adaptations of the human body under loads, thus mini-
ercise, balancing tasks, field tests, and upper extremity mizing the effect of the load on risk of injury and physi-
climbing tasks. Performance during the treadmill assess- cal performance.
ment (duration of time doing the task) was significantly
reduced in the trial run with the protective vest. Also
reported for the treadmill task was a significant decrease Effects of Operational Stressors
in Vo consumption. While this may seem to be contrary on Musculoskeletal Injuries
2
to what is expected, this finding was attributed by the Special Operators are well-rounded athletes, attaining
authors to a potential restriction of chest wall motion by high levels of strength, power, and aerobic fitness in
the protective vest. Additionally, as noted by Larsen et preparation for training and later missions. Strength,
45
al, this finding may have been due to the shortened time power, and quick movements such as jumping and sprint-
of the treadmill test with the protective vest. During ing have been shown to be important indices of fitness
42
the field assessments, a significant reduction in shuttle in combat, especially in urban operations. Aerobic en-
runs resulted from wearing the protective vest. How- durance has also been shown to be an important fitness
ever, no significant difference was detected in the box component for U.S. Army Rangers and Navy SEALs. 36,41
agility test and upper extremity climbing task. 45 Special Operators include some of the most aerobically
fit warfighters in the Armed Forces, with Vo max levels
2
To fully understand the impact of body armor on per- of (1) 57.7mL/kg/min for U.S. Navy SEALs, (2) 62.4mL/
formance, the external loads carried by military per- kg/min for BUD/S trainees, (3) 55mL/kg/min for U.S.
sonnel should also be considered when evaluating the Army Special Forces, and (4) 58.5mL/kg/min for British
influence of PPE on physical performance and exertion parachutists. High aerobic fitness is necessary for the
1,2
and heat stress. 42,46,47 Sell et al. found an increase in max- Special Operator, since SUSOPS is characterized mostly
imum knee flexion angle and maximum ground reaction by extended endurance movements. Special Operators
24
forces during two-legged drop landings while carrying are prepared for possible near-continuous daily physical
approximately 15kg of equipment (both combat and activity by their extensive training. For example, Navy
protective). Recommended countermeasures to reduce SEALs may conduct continuous combat operations in
46
the risk of injury include eccentric strengthening of the field for longer than 24 hours. Rigorous training
26
lower extremity muscles and training on proper land- while wearing heavy back pack loads may be necessary
ing techniques. Additionally, training protocols should to prepare Special Operators for combat and solidify the
include the management of external weight representa- warrior ethos, but extended durations of load carriage
tive of actual missions to ensure accurate preparation are commonly associated with stress fractures. Hen-
50
for operational scenarios. 46 ning et al. postulated that the significantly lower levels
of IGF-1 during 8 weeks of Ranger training and caloric
Other studies have focused on the kinematic changes restriction may be an important mediator of bone loss,
16
resulting from operational material handling tasks. 48,49 since IGF-1 may be vital in stimulating osteogenesis. 7,51
Seay et at. investigated the impact of carrying a rifle The operational environment of training in addition to
during operational tasks on upper body kinematics and the constant backpack load could lead to a reduction in
gait. During the running task, sagittal plane trunk range physical performance and increased injury risk. 34

Operational Stressors on Physical Performance and Countermeasures 73