Aerobic fitness in adolescents with chronic pain or chronic fatigue: Parallels and mechanisms

Objective: Chronic fatigue and chronic pain both deter people from participating in exercise, even though exercise is often a key component of treatment. While reasons for this may seem obvious, the extent and mechanism(s) of reduced exercise performance among affected individuals, particularly those with chronic pain, are not well described. We hypothesized that patients with chronic fatigue are more deconditioned than those with chronic pain, due to the nature of their illness or disability. Design: Retrospective chart audit June 2012 to December 2014. Subjects: Adolescents with chronic fatigue (320, 73 males) or chronic pain (158, 30 males). Methods: Maximal cardiopulmonary exercise test to determine peak oxygen uptake (VO₂) and work efficiency. Results: Mean (standard deviation (SD)) peakVO₂ was similar between patients with chronic fatigue and chronic pain: males 36.5 (SD 8.3) vs 34.2 (SD 7.3) ml/kg/min (p = 0.17); females 27.3 (SD 6.1) vs 27.6 (SD 6.6) ml/kg/min (p = 0.67). PeakVO₂ was < 90% predicted in 80% and 75% of females, or 77% and 83% of males, with chronic fatigue and chronic pain, respectively. Peak O2pulse and work efficiency were likewise similar. Conclusion: Patients in both groups manifest exercise responses typical of cardiopulmonary deconditioning and to similar extent. Failure to detect unique cardiopulmonary or muscle pathophysiology suggests a shared pathway to low aerobic work capacity.