Regular change in spontaneous preparative behaviour on intra-abdominal pressure and breathing during dynamic lifting

Intra-abdominal pressure (IAP) and breathing behaviour are important preparative pre-lifting actions for functional stability during lifting. This study aimed to examine spontaneous changes in the peak rate of IAP development (Rate-IAP), peak IAP (Peak-IAP), the time of Rate- and Peak-IAP occurrence and respiratory volume in response to dynamic load lifting. Eleven healthy men performed quick dynamic deadlifting using 30, 45, 60 and 75 % of the isometric maximal lifting effort (iMLE). IAP was measured using an intrarectal pressure transducer. The spontaneous respiratory volume was calculated from air flow data using pneumotachography. The lifting motion onset was determined from the hip joint motion using an electrogoniometer. From 30 to 75 % of the iMLE, Rate-IAP occurred early from 2 +/- A 28 to -179 +/- A 16 ms (P < 0.01), whereas Peak-IAP occurred late from 165 +/- A 31 to 82 +/- A 23 ms (P = 0.12) relative to the lifting motion onset. Rate-IAP increased from 224 +/- A 47 to 507 +/- A 69 mmHg/s (P < 0.01), whereas Peak-IAP increased from 37 +/- A 8 to 90 +/- A 11 mmHg (P < 0.01) at 30-75 % of the iMLE. Rate-IAP strongly correlated with Peak-IAP at each lifting load (r = 0.94-0.97). Relative to the resting tidal volume, the inspiratory volume during pre-lifting significantly increased above 60 % of the iMLE, whereas expiratory volume significantly decreased at all lifting loads. Preparative pre-lifting behaviours alter IAP and breathing and are co-ordinated by the lifting load magnitude. These behaviours appear to be functionally important for dynamic lifting.