STUDY DESIGN: Longitudinal single-cohort study. OBJECTIVE: To characterize the time course of performance adaptations during a postsurgical exercise intervention following a single-level microdiscectomy. BACKGROUND: Patients with a recent history of lumbar microdiscectomy are functionally limited, weak, have compromised paraspinal musculature, and benefit from an exercise program. METHODS: Patients (n = 48) with a single-level microdiscectomy participated in a 12-week (36 sessions) comprehensive strength and endurance exercise program starting 4 to 6 weeks postsurgery. Lumbar extensor strength was quantified as the degree from horizontal on a modified Sorensen test procedure. Patients unable to assume the horizontal position were assumed to have strength deficits. Lumbar muscular endurance performance was quantified by the amount of time patients could hold the Sorensen test position at the horizontal. The time rate of lumbar muscular endurance adaptations were analyzed using longitudinal growth curve modeling. RESULTS: The adherence rate of this program was low (67%). Twenty percent of the patients were identified as having strength deficits. These deficits were corrected in all patients within 3 to 9 weeks. Linear mixed-model results suggest an improvement of 5.6 seconds in hold time per week of exercise. Both the initial level of endurance and the rates of improvements were highly individualized. CONCLUSION: The time course of musculoskeletal performance adaptations in persons with a history of lumbar surgery is highly individualized. When compared to normative endurance times, the results of this study indicate that the number of sessions and duration of therapy needed to generate meaningful adaptations of the paraspinal musculature is longer than what is typically provided in the clinic postsurgery. LEVEL OF EVIDENCE: Therapy, level 4.

J Orthop Sports Phys Ther 2010;40(6):336-344, Epub 13 May 2010. doi:10.2519/jospt.2010.3141

KEY WORDS: herniated disc, low back pain, physical endurance, rehabilitation