Page 28 - JSOM Spring 2025

FIGURE 2 Estimation plot of individual shooting scores for control the blood draw in our investigation, and that these results have
(mean 318.4 s) and blood draw (mean 348.2 s) trials. important implications for donors in battlefield situations.

We were unable to find studies that included blinding, where
subjects serve as their own control, so it is difficult to explain
the fact that participants were able to determine the conditions
in our study. Based on the individual responses, it seems that
our blinding procedures were adequate, but that they perceived
their performance as markedly worse in the draw condition.
Moreover, few studies have examined anaerobically challeng-
ing events in military samples such as the 1,200-m shuttle. Our
moderate-to-large increase in time is interesting since Nadler et
al. showed no performance effects between donors and controls
in anaerobic tasks. They used shorter duration tests including
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the standing long jump, maximum repetition pull-ups in a 7-kg
weighted vest, maximum repetition deadlifts with a 60-kg trap
∆ bar, timed 50-m walking lunges with a 60-kg trap bar, and a
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200-m sprint. However, they did not state whether there was
rest taken between events. That same study showed no dona-
tion effects on marksmanship, but the participants’ rifle-only
marksmanship task was considerably shorter and less taxing
The mean difference was 29.2 seconds between trials (p=.015, Hedges’ than the one used in our study. Other less taxing pistol shoot-
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g=0.5). One soldier scored considerably better after blood donation,
and one considerably worse. ing tests are unchanged after blood donation in a repeated-
measures design (n=12). The moderate, about 5% decrease in
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FIGURE 3 Estimation plot of individual distance run times for 8-km run performance that we observed after donation is con-
control (74.2 [SD 4.7]) and blood draw (78.1 [SD 4.7]) trials. sistent with the literature in regards to endurance performance,
but the methodological variability in outcome measures makes
comparison difficult (as reviewed by Guillotte and Schilling).
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Additionally, the training status of participants would affect
performance changes after donation. The acute decrease in red
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blood cell volume would be detrimental to oxygen delivery for
aerobic tasks and could be coupled with a decrease in plasma
volume depending on rehydration techniques and timing. We
allowed water ad libitum, which may counteract some effects of
donation by preventing larger decreases in plasma volume. Our
study is also unique in that we performed the events successively
to simulate a situation where the Soldiers had to cover a long
distance immediately after a simulated firefight engagement.
Therefore, it is reasonable to assume that the performance dec-
rements seen in the 8-km run are cumulative in nature.
∆ It is also important to note that the performance effects were
not related to changes in heart rate, hydration, estimated
core temperature, or lactate concentration. We did not expect
changes in maximum heart rate during maximal effort tests,
There was a moderate, statistically significant increase in 8-km run but it is noteworthy that, while performing at the same heart
time after blood draw (Hedges’ g=0.7). There was greater variability
in performance after blood draw. rates, performance was poorer after blood donation. Similarly,
estimated core temperature is based on heart rate, so we also
There was no interaction between event and condition for expected little change. Lactate is not a common measure in
heart rate, estimated core temperature, blood lactate, or sali- military blood donation studies, but ours is not the first study
vary osmolality (Figure 4 a–d). With the exception of salivary to see little change after blood donation. 9,13 Using a hydration
osmolality, there was a large, statistically significant main ef- measure is uncommon in the literature, but it may be prudent
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fect for time for each (p<.0001), as expected. We were unable to verify hydration status in participants. Our hydration re-
to obtain 10 of the possible 34 post-run samples for salivary sults are ambiguous because of difficulties in data collection
osmolality because an adequate saliva sample could not be and the high variability in those results. Future studies may
collected, and the values had considerable variability. want to limit fluid intake as an additional, potentially com-
mon stressor to simulated battlefield tasks.
Discussion Future work in this area should continue to concentrate on

Our results show moderate-to-large performance decrements physically and cognitively demanding battlefield-specific tasks.
in demanding simulated combat tasks (Hedges’ g=0.5–1.0), Additionally, higher volumes of blood donation may be of in-
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which are somewhat greater than those of previous studies. terest, but safety concerns must be adequately addressed.
We believe that our results are different due to the more de- Advances in markers such as compensatory reserve measure-
manding simulated battlefield tasks that were performed after ment may allow screening of donors, providing a means to

26 | JSOM Volume 25, Edition 1 / Spring 2025