Paraspinal precontraction does not enhance isokinetic trunk extension performance.
METHODS
This study investigated the influence of isometric contraction of the trunk extensor muscles, immediately preceding maximum effort isokinetic trunk extension (precontraction), on isokinetic performance variables and activation levels of the paraspinal muscles.


OBJECTIVE
To determine whether agonist precontraction significantly improved the concentric and eccentric isokinetic trunk extension contraction.


BACKGROUND
Agonist precontraction has been reported to enhance agonist neural drive and force output of the knee and ankle joints.


METHODS
Subjects performed concentric and eccentric isokinetic trunk extension at 60, 90, and 120 deg/sec, each of which were preceded by isometric trunk extension precontraction force equal to 0%, 25%, and 50% body weight.


RESULTS
Concentric and eccentric contractions showed general, but no statistically significant performance enhancement with paraspinal precontraction. Eccentric contractions tended to improve to a greater extent than concentric contractions.


CONCLUSIONS
It is possible that the addition of agonist precontraction increased the complexity of the trunk extension task, thus requiring a learning period, as is the case with most novel motor skills. There may be meaningful rehabilitation-related implications of the qualitative tendencies observed in the data that merit further consideration.
Grabiner
M D
MD
Department of Biomedical Engineering, Cleveland Clinic Foundation, Ohio.
Kasprisin
J E
JE
D000328:Adult; D001415:Back; D001696:Biomechanical Phenomena; D004576:Electromyography; D016552:Ergometry / Q000295:instrumentation; D005260:Female; D006801:Humans; D017116:Low Back Pain / Q000534:rehabilitation; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D012815:Signal Processing, Computer-Assisted