[Isokinetic trunk strength testing in chronic low back pain. The role of habituation and training to improve measures].

UNLABELLED

Isokinetic dynamometers put subjects in very different conditions from natural movement. Familiarization with the isokinetic device may therefore explain better performance without showing any improvement in strength.

OBJECTIVE

To determine the part of habituation and training in improved trunk isokinetic performance on isometric assessment after a back rehabilitation program for chronic low back pain.

METHODS

A total of 26 patients with chronic low back pain consecutively admitted to the same rehabilitation department for a 4-week rehabilitation program underwent isometric assessment of the trunk flexors and extensors on the day of admission and 2 days and 21 days after admission. The maximal torque and total work were registered at 30 degrees , 90 degrees and 120 degrees/s.

RESULTS

Values for all parameters, except flexor values at 30 degrees/s, were significantly improved between day 0 and day 2 after admission. Between day 2 and day 21 after admission, values for all parameters were improved significantly. Except for flexor values at 30 degrees/s, the parameter values at day 2 showed improvement ranging from 33% to 58% of the improvement seen at day 21.

DISCUSSION

The improvement in parameter values found on isokinetic assessment two days after a one-day rehabilitation program for low back pain is probably explained by a habituation effect. We can expect that increase in the maximal torque and total work after 3 weeks of rehabilitation is, at least in part, the consequence of the strengthening program.

CONCLUSION

We should interpret with caution the results of studies involving an isokinetic dynamometer to measure the strength of trunk muscles without a learning training.