Biomedical subjects

D Casey Kerrigan

Publications and source records attributed to D Casey Kerrigan.

20 records · Page 2Linked to original sources

PubMedDate not supplied

Reduced quadriceps activation after lumbar paraspinal fatiguing exercise.

CONTEXT: Although poor paraspinal muscle endurance has been associated with less quadriceps activation (QA) in persons with a history of low back pain, no authors have addressed the acute neuromuscular response after lumbar paraspinal fatiguing exercise. OBJECTIVE: To compare QA after lumbar paraspinal fatiguing exercise in healthy individuals and those with a history of low back pain. DESIGN: A 2 x 4 repeated-measures, time-series design. SETTING: Exercise and Sport Injury Laboratory. PATIENTS OR OTHER PARTICIPANTS: Sixteen volunteers participated (9 males, 7 females; 8 controls and 8 with a history of low back pain; age = 24.1 +/- 3.1 years, height = 173.4 +/- 7.1 cm, mass = 72.4 +/- 12.1 kg). INTERVENTION(S): Subjects performed 3 sets of isometric lumbar paraspinal fatiguing muscle contractions. Exercise sets continued until the desired shift in lumbar paraspinal electromyographic median power frequency was observed. Baseline QA was compared with QA after each exercise set. MAIN OUTCOME MEASURE(S): An electric burst was superimposed while subjects performed a maximal quadriceps contraction. We used the central activation ratio to calculate QA = (F(MVIC)/[F(MVIC) + F(Burst)])* 100, where F = force and MVIC = maximal voluntary isometric contractions. Quadriceps electromyographic activity was collected at the same time as QA measurements to permit calculation of median frequency during MVIC. RESULTS: Average QA decreased from baseline (87.4% +/- 8.2%) after the first (84.5% +/- 10.5%), second (81.4% +/- 11.0%), and third (78.2% +/- 12.7%) fatiguing exercise sets. On average, the group with a history of low back pain showed significantly more QA than controls. No significant change in quadriceps median frequency was noted during the quadriceps MVICs. CONCLUSIONS: The quadriceps muscle group was inhibited after lumbar paraspinal fatiguing exercise in the absence of quadriceps fatigue. This effect may be different for people with a history of low back pain compared with healthy controls.

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PubMedDate not supplied

Quadriceps inhibition after repetitive lumbar extension exercise in persons with a history of low back pain.

CONTEXT: A neuromuscular relationship exists between the lumbar extensor and quadriceps muscles during fatiguing exercise. However, this relationship may be different for persons with low back pain (LBP). OBJECTIVE: To compare quadriceps inhibition after isometric, fatiguing lumbar extension exercise between persons with a history of LBP and control subjects. DESIGN: A 2 x 3 factorial, repeated-measures, time-series design with independent variables of group (persons with a history of LBP, controls) and time (baseline, postexercise set 1, postexercise set 2). SETTING: University research laboratory. PATIENTS OR OTHER PARTICIPANTS: Twenty-five subjects with a history of LBP were matched by sex, height, and mass to 25 healthy control subjects. INTERVENTION(S): Electromyography median frequency indexed lumbar paraspinal muscular fatigue while subjects performed 2 sets of isometric lumbar extension exercise. Subjects exercised until a 15% downward shift in median frequency for the first set and a 25% shift for the second set were demonstrated. MAIN OUTCOME MEASURE(S): Knee extension force was measured while subjects performed an isometric maximal quadriceps contraction. During this maximal effort, a percutaneous electric stimulus was applied to the quadriceps, causing a transient, supramaximal increase in force output. We used the ratio between the 2 forces to estimate quadriceps inhibition. Quadriceps electromyographic activity was recorded during the maximal contractions to compare median frequencies over time. RESULTS: Both groups exhibited significantly increased quadriceps inhibition after the first (12.6% +/- 10.0%, P < .001) and second (15.2% +/- 9.7%, P < .001) exercise sets compared with baseline (9.6% +/- 9.3%). However, quadriceps inhibition was not different between groups. CONCLUSIONS: Persons with a history of LBP do not appear to be any more or less vulnerable to quadriceps inhibition after fatiguing lumbar extension exercise.

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