Form influences function: Anthropometry and orthostatic stability during sustained acceleration in a short arm human centrifuge

Abstract Introduction The goal of this study was to determine which anthropometric factors measured via air displacement plethysmography (ADP) play a significant role in augmenting orthostatic stability during sustained acceleration G-force (+G) exposure in a short arm human centrifuge (SAHC). The authors hypothesized that test subjects with a greater normalized fat free mass in percentage of total body mass (FFM%) would exhibit greater orthostatic stability during consecutive +G loads. Methods Twenty +G naive test subjects (10 female, 10 male), were recruited for this study, in which they underwent 2 rounds of 1/2/1 G-force profile in a SAHC. Before being exposed to +G, each subject underwent anthropometric analysis via ADP to ascertain total body mass (BM, kg), body volume (BV, L), body surface area (BSA, m 2 ), normalized fat mass/fat free mass in percentage of total body mass (FM% and FFM%). During SAHC exposure, hemodynamic parameters were continuously obtained from each test subject. The measured anthropometric parameters were compared against baseline mean arterial pressure (MAP, mmHg), heart rate (HR, bpm), stroke volume (SV, mL) cardiac output (CO, L min −1 ) and systemic vascular resistance (SVR, dyn s cm −5 ) to determine correlations. Results From the 20 subjects, 13 test subjects (5 F, 8 M) completed all phases of +G exposure, and were therefore classified as having high +G tolerance (NALOC). From the 7 remaining test subjects (5 F, 2 M); 6 aborted or reduced their +G exposure, and were therefore classified as exhibiting low +G tolerance (ALOC). One subject dropped out prior to testing, and is not included in the data. Total BM, BV, and BSA were significantly higher ( p Discussion Total BM, BV, and BSA were the anthropometric factors associated with orthostatic stability during +G. The higher these parameters, the higher the baseline SV, which combined contributed to greater orthostatic stability during +G. Male test subjects had an overall advantage over females via increased body dimensions and augmented cardiac function. Anthropometric analysis via ADP thus reveals critical information regarding how anthropometry influences hemodynamic function and further studies on this topic are warranted.