The force-velocity relation and intra-abdominal pressure during lifting activities

Intra-abdominal pressure increases stiffness of the lumbar spine

“…When IAP was increased by 1.8-5.9 kPa, the spinal stiffness was increased by 8-31% from control values recorded at the end of a normal expiratory effort. Assuming that the relationship between IAP and stiffness is linear (although this may not be the case), extrapolation from the linear regressions calculated for each subject suggests that a large increase in stiffness may occur with IAP changes of 5-220 cm H 2 O that have been recorded during functional activities (Cresswell et al, 1993;Gandevia et al, 1990;Grillner et al, 1978;Harman et al, 1988;Hemborg et al, 1985;Marras et al, 1985). The amplitude of stiffness increase (8-31%) is similar to the 12-41% increase in stiffness observed during voluntary contraction of ES at 10-30% of a maximal voluntary contraction (Shirley et al, 1999).…”

“…It has been argued that this pressure in the abdominal cavity contributes to the stiffness and stability of the spine (Bartelink, 1957;Grillner et al, 1978). In support, several studies have identified a relationship between the magnitudes of IAP and the forces imposed on the spine in a variety of static and dynamic tasks Grillner et al, 1978;Marras et al, 1985). However, others have argued that the pressures generated during functional tasks are insufficient to provide a significant increase in spinal stability (McGill and Norman, 1987).…”

Status in Human Strength Research and Application

“…The dynamic strength peaks would otherwise be significantly lower than static strength peaks (Asmussen et al , [41]; Kumar et al, [38]; Garg et al, [16]). for higher frequencies, and 3) repentive dynamic strengths are better estimators of an individual's capability to perform tasks that require repeated heavy physical exertion.…”

“…Some applications of dynamic strength include measurement of whole body lifting strength (Pytel and Kamon,[61]; Kamon et al, [24]; Kroemer, [29], [30], [31]; Mital et al, [49], [57]); back and arm lifting strengths (Kumar et al, [38]); trunk flexion, extension, and rotation strengths (Smith et al • [66]); lifting strength in teamwork (Karwowski and Mital, [25]; Karwowski and Pongpatanasuegsa, [26]); onehanded pull-up and pull strengths (Mital and Genaidy, [52]; Mital and Faard, [51]). Marras et al, [41], [42] have used isokinetic devices to study the effects of trunk angle and speed on the torque production capability of the back and the relationship between the onset of intraabdominal pressure and torque produced by the back. Several studies have demonstrated a correlation between actual maximum lifting capability and isokinetic strengths (Pytel and Kamon,[61]; Kamon et al, [24]; Mital et al, [53]) and maximum acceptable weight of lift for repetitive tasks and repetitive isokinetic strengths (Mital et al• [49], [57]).…”

On the bending moment capability of the pressurized abdominal cavity during human lifting activity

“…(Compare the structure of the motor car tyre.) In this context it is interesting to recall the correlation found by Marras et al (1985) between IAP and the activity of the larksirnus dorsi. It also follows that people already afflicted with certain types of lower back injury could be helped if their IAP could be increased in order to unload the lumbar spine.…”