Tolerance of small animals to acceleration

Area of Science:

• * Aerospace Medicine
• * Comparative Physiology
• * Biomedical Engineering

Background:

• * Understanding animal tolerance to acceleration (G-forces) is crucial for aerospace and defense applications.
• * Previous research has focused on specific species or force directions, necessitating a comparative analysis across diverse taxa and inertial vectors.
• * The impact of body weight and G-force direction on tolerance thresholds requires further elucidation.

Purpose of the Study:

• * To compare the G-force tolerance of various animal species subjected to different inertial vectors (+Gz, -Gz, -Gx).
• * To quantify species-specific tolerance curves and identify factors influencing resistance to prolonged acceleration.
• * To establish tolerance ratios between different G-force directions and assess the relationship between body weight and G-tolerance.

Main Methods:

• * Exposure of mice, rats, rabbits, finches, pigeons, and roosters to +Gz, -Gz, and -Gx inertial forces.
• * Application of G-force magnitudes up to 130 G for durations up to 20 minutes, with an average rate of change of 2.8 G/s.
• * Determination of 50% mortality thresholds and calculation of the area under the tolerance curve for each species.

Main Results:

• * Significant variations in G-tolerance were observed among the tested species.
• * The tolerance ratio of minus Gx to +Gz force was 2.12, indicating higher tolerance to -Gx.
• * Body weight was inversely related to the threshold G-value, with lighter animals showing greater resistance to prolonged acceleration.

Conclusions:

• * Species-specific differences in G-force tolerance are pronounced and influenced by the direction of applied inertial forces.
• * Minus Gx acceleration is better tolerated than +Gz acceleration across the studied species.
• * Body mass is a critical factor in determining an animal's resistance to sustained acceleration, with implications for biodynamic modeling and protective strategies.