Combined effect of heart rate responses and the anti-G straining manoeuvre effectiveness on G tolerance in a human centrifuge

Abstract

Increased heart rate (HR) is a reaction to head-to-toe gravito-inertial (G) force. The anti-G straining manoeuvre (AGSM) is the crucial technique for withstanding a high-G load. Previous studies reported the main effects of HR only or AGSM only on G tolerance. We assessed the combined effect of HR and AGSM on the outcome of 9G profile exposure. A total of 530 attempts for the 9G profile were extracted to clarify the association of interest. Subjects with an AGSM effectiveness of less than 2.5G had a 2.14-fold higher likelihood of failing in the 9G profile. Trainees with HR increases of less than 20% in the first five seconds also had higher odds of 9G profile intolerance (adjusted OR 1.83, 95% CI 1.09–3.07). The adjusted OR of 9G profile disqualification was 2.93 (95% CI 1.19–7.20) for participants with smaller HR increases and lower AGSM effectiveness. The negative effect of a smaller HR increase on the outcome was likely to be affected by improved AGSM effectiveness (adjusted OR 1.26, 95% CI 0.65–2.42). We speculate that low AGSM effectiveness and a small HR increase were separately associated with failure of high-G challenge. Nonetheless, good AGSM performance seemed to reduce the negative effect of weak HR responses on the dependent variable.

A Cardiac Force Index Applied to the G Tolerance Test and Surveillance among Male Military Aircrew

“…After adjustment for confounders, we also identified that participants with higher WCFI had higher G tolerance during training, especially for SGT. In addition, AGSM effectiveness is one of the determinants of SGT; moreover, it compensates for the weaker cardiovascular responses against GLOC [11]. Therefore, compared to RGT, we found that the WCFI had a stronger correlation with the SGT value.…”

“…From the literature review, we also summarized that weight is positively correlated with G tolerance [10,20]. In addition, our former findings identified that there is an inverse relationship between the G tolerance and HR on the ground [10,11]. As stated above, we therefore presumed that CFI might also be connected to G tolerance during the centrifuge training.…”

“…Cardiovascular responses regulated by the autonomic nervous system play a crucial role in G tolerance. From the centrifuge training database, our team found that failed trainees had a lower proportion of increases in HR than passing trainees [10,11]. Therefore, dynamic CFI should be a much better cardiac indicator used to establish a predictive model for G tolerance.…”

“…The training target of flying jet fighters is to sustain 7.5 G for 15 s. High-performance fighter pilots are required to tolerate the challenge of 9 G for 15 s, at a very high-onset rate. Previous reports revealed that military aircrew had a higher chance of failing during the 9 G-15-s training if their RGT or SGT was less than 5 G or 8 G, respectively [11,20]. In the next step, we classified study participants into different G tolerance groups that depended on RGT (≥5 G vs. <5 G) or SGT (≥8 G vs. <8 G) and distinguished the WCFI differences between those groups.…”

“…Trainees can experience physiological impacts and perform an effective anti-G straining maneuver (AGSM) against GLOC. Activation of the cardiovascular system plays a crucial role in the tolerance of G force [9][10][11]. AGSM execution also simultaneously enhances cardiovascular performance under G load [12].…”