ASSOCIATION OF HORMONAL RESPONSES AND PERFORMANCE OF STUDENT
PILOTS DURING ACCELERATION TRAINING ON THE HUMAN CENTRIFUGE
D. Wirth(1), N. Rohleder(2), H. Welsch(3)
Dresden University of Technology, Department of Psychology, Biopsychology, Zellescher Weg 17, D-01069
Dresden, Germany, Email: firstname.lastname@example.org
Dresden University of Technology, Department Psychology, Biopsychology, Zellescher Weg 17, D-01069 Dresden,
Germany, Email: email@example.com
German Air Force Institute of Aviation Medicine, Division Aviation Physiology, SteinbornerStraße 43, D-01936
Königsbrück, Germany, HeikoWelsch@bundeswehr.org
individuals who are able to mount a large stress response
are better protected against loss of blood pressure during
Prediction of student pilots’ +Gz tolerance by stress acceleration and thus could be better capable of tolerating
hormone levels would be a useful tool in aviation a high +Gz load.
medicine. The aim of the present study was to analyze the Based on this assumption, the aim of the present study
relationship between neuroendocrine parameters with was to search for associations between HPA axis and
performance during acceleration training on the human SAM system parameters at rest and in response to
centrifuge (HC). acceleration with performance parameters of student
We investigated 21 student pilots during self-controlled pilots on the human centrifuge.
acceleration training on the HC. Adrenocorticotropic
hormone (ACTH), cortisol, epinephrine, and
norepinephrine were measured after individual training 3.1. Subjects and Experimental Protocol
sessions and at rest. Performance was defined by several Subjects were 21 student pilots (22.6 yrs ± 1.8 SEM;
characteristics including maximum tolerated acceleration. BMI 23.1 kg/m2 ± 0.4 SEM) enrolled in training on high-
ACTH and cortisol, were significantly higher 20 minutes performance jet aircraft. The study protocol was
after acceleration training compared to the resting approved by the local ethics committee and written
condition. Subjects tolerated a maximal acceleration of informed consent was obtained from all subjects.
+6.69 Gz. HPA hormone levels and responses were Acceleration training took place on the human centrifuge
associated with maximum tolerated acceleration +Gz. of the German Air Force Institute of Aviation Medicine,
These findings support the expectation that acceleration- Königsbrück, Germany. After a “warm-up” session, the
induced increases in stress hormones may enable the main acceleration training started. Student pilots were
organism to tolerate a higher acceleration and could instructed to reach their personal maximum +Gz tolerance
therefore be used as predictors for acceleration tolerance. by self-controlled acceleration. The goal was to achieve
2. INTRODUCTION +7 Gz and to endure it for at least 15 seconds. Blood
samples were drawn 20 minutes after cessation of the
The prediction of individual +Gz tolerance would be of training into EDTA tubes. Resting samples were taken
great use in physiological assessment of student pilots. three days after the training between 07:00 and 07:30h.
However, the predictive value of single anthropometric
3.2. Endocrine and Performance Parameters
and physiological variables has been shown to be low ,
Plasma concentrations of stress hormones were
while the combination of physiological, respiratory and
determined using commercial immunoassays (ACTH:
muscular parameters proved useful in one study .
DPC Biermann, Bad Nauheim; cortisol: Bayer Vital,
Since +Gz tolerance largely depends on the maintenance
Fernwald; epinephrine and norepinephrine: IBL-
of blood flow to the central nervous system , it could
Hamburg, all Germany). Several performance parameters
be assumed that activation of physiological stress
were recorded during each training session. (1) Mean
systems, such as the sympatho-adrenal-medullary (SAM)
segment duration (of training segments and breaks), (2)
system and the hypothalamus-pituitary-adrenal (HPA)
integrated +Gz during all acceleration periods and mean
axis should be positively associated with +Gz tolerance
+Gz, (3) maximum acceleration +Gz and time on
and their assessment could prove useful in the prediction
of +Gz tolerance.
In fact, acceleration in a human centrifuge leads to 3.3. Statistical analyses
activation of the SAM system with release of epinephrine Analyses of variance for repeated measures were
and norepinephrine, and of the HPA axis with release of calculated to test for differences between resting and post
cortisol (e.g. ). Since the activation of these stress training levels of stress hormones. Pearson correlations
systems enables the organism to better endure adverse were calculated to test for associations between hormone
environmental conditions, it could be assumed that those levels and performance parameters.
4. RESULTS the time spent on maximum +Gz (r=-.40*) and the
maximum +Gz itself (r=-.44*). The difference between
4.1. Endocrine parameters resting and post training cortisol was positively
Twenty minutes post acceleration, ACTH levels in associated with the time spent on maximum acceleration
plasma were significantly higher compared to those (r=.39*; see table 1 for all correlations). No associations
measured at rest (F1,206.67; p=0.02). Cortisol differences of SAM hormones and performance parameters were
failed significance in ANOVA (F1,20=2.63; p=0.12), but found (data not shown).
were significant in Wilcoxon Test: Z=-2.1; p<.05; Fig. 1)
We set out to test whether stress hormone levels are
useful predictors of student pilots’ performance during
acceleration training on the human centrifuge. We found
increased levels of the HPA axis hormones ACTH and
cortisol twenty minutes after acceleration training
compared to a resting condition. The SAM hormones
epinephrine and norepinephrine, however, were not
increased after acceleration training. This was most likely
caused by the fact that the blood samples were taken too
late after training to capture the peak response.
Performance characteristics and HPA axis hormones
were correlated in a way that higher resting levels and
Fig. 1: The HPA axis hormones ACTH and cortisol at rest and higher increases of ACTH and cortisol were associated
20 minutes after +Gz acceleration. with higher performance during training, i.e. higher
maximum acceleration tolerated, and longer toleration of
Epinephrine and norepinephrine levels did not differ maximum acceleration. SAM hormones, i.e. epinephrine
significantly between resting and post-acceleration and norepinephrine, were not associated with
conditions (all F<1; data not shown). performance parameters.
4.2. Performance characteristics The results obtained in this study support the hypothesis
Mean duration of the complete training session was 9 that the ability to activate the stress systems in a
min. 4:51 minutes were spent on accelerations >1.4Gz, sufficient way enables the organism to better tolerate the
total duration of breaks was 3:27 min. Individual high +Gz acceleration forces. HPA axis hormones could
segments lasted 56 s (range: 21 to 95 s). A mean of 5.67 therefore be seen as predictors of acceleration tolerance
(±2.18SD) acceleration periods were completed, during given that these preliminary results are replicated in
which a mean acceleration of +3.91 Gz (±0.46SD) was future studies.
reached. The maximum acceleration ranged from +4Gz to
+7Gz (mean: +6.69 Gz; ±0.68SD) and was tolerated for an 6. REFERENCES
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