Experimental impacts to the lateral thoracic wall of anaesthetised pigs by nonpenetrating projectiles of mass range 0.069 kg to 3.0 kg within an overall velocity range 5.8 m/s to 81.2 m/s have allowed empirical models to be derived to predict the magnitude of the peak distortion of the chest wall under loading by the free-flying projectile (Pmax) and the time taken for Pmax to be attained after initial contact of the projectile upon the thoracic wall (Time-95). Pmax can be described as a function of projectile momentum, body weight and effective contact diameter;​ Time-95 is dependent upon projectile mass and body weight and is independent of projectile velocity. The severity of pulmonary contusion is dependent not only upon the peak relative thoracic wall distortion, but also upon the time taken to reach the peak distortion, Time-95. The particular projectiles used in this study resulted in peak chest wall distortions being attained within the time range 1 ms to 22 ms after contact. The short duration impacts could result in serious pulmonary injuries at very small thoracic compressions, conversely, very large chest compressions produced relatively minor lung injury if the time to peak distortion was of long duration. Biophysical phenomena that may account for these rate-dependent effects are discussed.