Page 92 - JSOM Fall 2021

that caffeine may increase blood flow and muscle tissue sat- the condition on susceptibility to enemy fire was exceptionally
2
uration that may increase lower-body muscle function. 47–49 low (η = .001) and would have required many subjects (ap-
We found no significant effect of caffeine on fire-and-move proximately 200) to detect statistical significance. Lastly, tac-
simulation performance (i.e., repeated sprints), corroborating tical combat movements are conducted with multiple soldiers
the results of others. 24,44,50–55 It is possible that providing sub- and units. Thus, our findings may not translate when multiple
jects with a substance that potentially had an active-ingredient soldiers work together during direct-fire engagements. 8
56
elicited an ergogenic response. However, this explanation is
unlikely since nearly half of the subjects reported no perceived
effect from the placebo supplement. Alternatively, it is possible Conclusion
that the familiarization session was unsuccessful in mitigating Our investigation determined the effects of caffeinated gum on
a learning effect. marksmanship, cognition, bound duration, and susceptibility
to enemy fire during a tactical combat movement simulation.
Stressful environments are reported to cause decrements to The authors found that susceptibility to enemy fire increased,
aspects of lower cognitive function and decision-making. 10–12 and that cognitive performance decreased during the tacti-
The fire-and-move simulation deteriorated cognitive perfor- cal combat movement simulation. However, caffeine did not
mance, but not marksmanship. This is perhaps because it did change marksmanship, cognition, bound duration, or suscep-
not provide enough stress to deteriorate marksmanship. 57,58 tibility to enemy fire. Significant increases in bound duration
Stress-induced cognitive decline, such as sleep deprivation, is indicates that susceptibility to enemy fire increased during the
22
often mitigated with caffeine supplementation in soldiers. repeated bounds, which, in turn, may decrease soldier surviv-
Caffeine also improves complex soldier tasks such as marks- ability. While caffeine was not effective at maintaining bound
manship reaction time. However, the effects of caffeine on duration or changing marksmanship or cognitive performance,
marksmanship accuracy are not well documented. 59 the authors cannot discount the possibility of improvements in
performance from caffeine after sleep deprivation.
Our analysis revealed that neither cognitive performance,
marksmanship reaction time, nor marksmanship accuracy Acknowledgments
were different between placebo and caffeine conditions. Our The authors would like to thank Shea Crum, Blake Goodman,
results confirm previous reports documenting no improve- and Jason Sartor for their efforts in assisting with data collec-
ments in marksmanship accuracy after caffeine supplementa- tion, as well as Rikki Stein for helping curate Figure 1.
tion when protocols elicit a stressful environment without sleep
deprivation. 28,60–63 Additionally, this is the first study to docu- Funding
ment the effects of caffeine supplementation on marksmanship The work was supported by Kansas State University College
reaction time during a fire-and-move simulation without sleep of Health and Human Sciences Doctoral Dissertation Award
deprivation. Our findings suggest that caffeine supplemen- and the Kansas State University Arts, Humanities, and Social
tation does not improve marksmanship reaction time. Thus, Sciences Small Grant.
caffeine’s ergogenicity on marksmanship parameters may only
be revealed in sleep-deprived subjects. 29,64,65 Collectively, our Disclosure
findings suggest that caffeine was not an effective ergogenic aid The authors have indicated they have no financial relation-
during a simulated tactical combat movement in rested sub- ships relevant to this article to disclose.
jects. However, understanding the effects of caffeine on per-
formance during direct-fire engagements while sleep-deprived Author Contributions
may have implications to soldier survivability during sustained JAS, JAD, TCH, and K. M. Heinrich conceived the study con-
operations and presents an avenue for future investigations. cept. JAS and TCH obtained funding. JAS recruited partici-
pants and coordinated and collected data, JAS, JAD, CMB,
The current investigation was strengthened by a robust study CDB, K. M. Holte, and BKK acquired data. JAS analyzed data
design with subjects serving as their own controls in a dou- and wrote the first draft of the manuscript. All authors read
ble-blind, counterbalanced, crossover design that determined and approved the final manuscript.
the effects of caffeinated gum. This study also utilized a com-
bat-relevant protocol that induced both physical and cogni- References
1. USA Department of Defense. Defense causality analysis system.
tive stressors. Yet, our study does not go without limitations. https://dcas.dmdc.osd.mil/dcas/pages/main.xhtml. Accessed 26 May
Our study included research volunteers who were active-duty 2021.
military personnel with a rifle qualification or civilians. Our 2. Silk A, Billings D. Development of a valid simulation assess-
subjects, however, exceeded the US Army standards by suc- ment for a military dismounted assault task. Mil Med. 2013;178
cessfully engaging at least 75% of targets. Also, since there (3):315–320.
is no difference in combat simulation performance between 3. Billings D, Silk A, Tofari P, Hunt A. Effects of military load car-
civilians and military personnel, the authors did not feel that riage on susceptibility to enemy fire during tactical combat move-
ments. J Strength Cond Res. 2015;29(11):134–138.
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this influenced our out comes or interpretations. Our study 4. Hunt AP, Tofari PJ, Billing DC, et al. Tactical combat movements:
did not include invasive measures of plasma caffeine concen- inter-individual variation in performance due to the effects of
tration, which limited our ability to confirm that caffeine lev- load carriage effects of load carriage. Ergonomics. 2016;59(9):
els significantly increased after chewing the caffeinated gum. 1232–1241.
However, ingestion of caffeine may not be necessary to elicit 5. Barringer MAJN, Rooney M. The rush: how speed can save lives.
Infantry. 2016;(July):9–12.
an ergogenic response as evidenced by rinsing caffeinated flu- 6. Stein JA, Hepler T, Cosgrove S, Heinrich KM. Relationship be-
ids. Eight subjects did not complete the study, which, in part, tween self-reported combat-relevant task frequency, difficulty, and
25
was due to the COVID-19 outbreak. Thus, a fully powered importance. Proceedings of the 3rd conference on Physical Em-
study may have provided different results. The effect size of ployment Standards. 2018; pp. 32.

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