Maximal cardiopulmonary exercise test in patients with chronic low back pain: feasibility, tolerance and relation with central sensitization. An observational study

Abstract

Purpose

To analyze the feasibility of and pain-related tolerance to a maximal cardiopulmonary exercise test (CPET), and the relationship between the aerobic capacity and central sensitization (CS) in patients with chronic low back pain (CLBP).

Methods

An observational study, combining a cross-sectional and a prospective 24-hour follow-up was performed. Participants underwent a maximal CPET on a cycle ergometer and were assessed with three measures of CS (CS Inventory, quantitative sensory testing and heart rate variability). Before the CPET, immediately afterwards and 24 h after, the Pain Response Questionnaire (PRQ) was filled out. The CPET was considered feasible when >80% performed maximally, and tolerable when <20% reported relevant pain increase, body reactions and additional pain medication use in the PRQ. Multiple regression analyses were applied to assess the relationship between the aerobic capacity (VO2max) and CS measures, corrected for confounders.

Results

74 patients with CLBP participated of which 30 were male, mean age was 40.4 years (SD: 12.4) and median VO2max was 23.9 ml/kg/min (IQR: 18.2–29.4). CPET was completed by 92%. No serious adverse events occurred. A relevant pain increase was reported in the upper legs by 40% immediately after CPET and by 28% 24 h afterwards, 27% reported body reactions after 24 h, and 22% increased pain medication use 24 h after CPET. Very weak and not significant relations (r_partial=−0.21 to 0.05; p > 0.10) were observed between aerobic capacity and CS measures.

Conclusions

A maximal CPET is feasible in patients with CLBP. Most, but not all, tolerated it well. CS was not related to aerobic capacity.

Implications for rehabilitation

• Maximal CPET is feasible in patients with CLBP and well tolerated by most patients.

• Maximal CPET can be safely applied to assess the aerobic capacity of patients with CLBP.

• Aerobic capacity is unrelated to central sensitization.

• Outcomes of a maximal CPET and the pain response to straining activity can be used to provide valid information for the decision-making of exercise therapy.

Keywords:

• Deconditioning
• cardiorespiratory fitness
• cycle ergometry
• pain response
• hypersensitivity

Acknowledgments

The authors wish to express their gratitude to the patients who participated and the personnel of the CvR-UMCG who collaborated in the study. In particular, to the Pain Rehabilitation Team and the Central Exercise Lab team during patient data collection process.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Notes

1 The respiratory exchange ratio (RER) can reflect the metabolic rate. Its value is the ratio of carbon dioxide production (VCO₂) to the oxygen consumption (VO₂) [28].

Additional information

Funding

Internal funding from the Rehabilitation department UMCG was obtained for this study.