Relevance of aerobic capacity measurements in the treatment of chronic work-related spinal disorders

Study Design. Prospective cohort study of rehab program completers, comparing aerobic capacity data of chronic lumbar spinal disorder patients (CLSD) to that of chronic cervical spinal disorder (CCSD), collected from a tertiary care facility. Objective. We evaluated whether CLSD is associated with different pre- and postrehabilitation aerobic capacity deficits than CCSD, and whether such deficits affect functional restoration outcomes. Summary of Background Data. Chronic spinal disorder patients are thought to lose aerobic fitness as a component of the deconditioning syndrome. Patients with CLSD often restrict aerobic activities because of back or leg pain, while CCSD patients generally do so to a lesser degree. We hypothesized that those with CLSD would have greater deficits in tests of aerobic fitness than patients with CCSD both before and after treatment. Methods. From a consecutive cohort of 683 patients with work-related spinal disorders, two groups were identified: patients with CLSD ( n = 504; age 40.1 years; 68% male); and patients with CCSD ( n = 179; 41.3 years; 43% male). All patients completed an intensive, medically supervised functional restoration program. Before and after the program, patients completed a submaximal bicycle ergometer aerobic capacity test and a psychosocial test battery. A structured clinical interview to determine socioeconomic outcomes was conducted 1 year after the program completion. Results. Of CLSD patients 33% and 11% of CCSD patients ( P < 0.001) either failed to produce any torque or could not complete at least 2 stages on the bicycle on preprogram tests ( invalid tests). However, all patients had valid bicycle tests at program completion. Nearly two-thirds of the subjects with initially invalid tests in the lumbar group failed to develop any torque, while only one-third of subjects with invalid tests of the cervical group had a similar result. Thus, CLSD is associated with greater prerehabiliation aerobic fitness deficits than CCSD. Overall, there was no significant change in pre to postrehab aerobic capacities for the initially valid test subjects. The initially invalid test subjects achieved similar postrehabilitation scores compared to the valid test subjects, although CLSD patients with initially valid tests performed slightly better at the posttest. Socioeconomic outcomes were the same one year after the program for valid and invalid test subjects. CLSD patients had higher preprogram self reports of disability. The subgroup of the initially invalid test subjects that produced no torque whatsoever (19.3% of CLSD and 3.9% of CCSD) did not differ from the subgroup that failed to complete 2 stages in the pretest of aerobic performance on depression. They had higher pretest self-reported disability. Conclusions. Although mean aerobic fitness levels for all patients improved during rehabilitation, the improvement is almost entirely accounted for by initially invalid tests becoming valid. Aerobic capacity testing measured with submaximal bicycle ergometry may frequently be invalid when fear-avoidance limits effort, particularly in CLSD. Psychosocial fear-avoidance, as it applies to bicycle ergometry, can be overcome in virtually all patients motivated to complete a tertiary rehabilitation program. As such, prerehabilitation aerobic capacity testing is a poor differentiator of postrehabilitation outcomes.