Are biomarkers associated with sensitivity to physical activity?

BACKGROUND

Activity-based treatments play an integral role in managing musculoskeletal conditions including low back pain. However, while therapeutic exercise has been shown to reduce pain in such conditions, certain individuals experience a paradoxical pain increase in response to exercise. The physiological processes underlying this sensitivity to physical activity (SPA) are not fully understood, however stress and inflammation have been shown to contribute to SPA. The present cross-sectional study investigated whether physiological indicators of stress (cortisol) and inflammation (IL-6) help explain SPA.

METHODS

Twenty-seven patients with chronic low back pain and 21 healthy controls completed a 1-h exercise session of standardized physical tasks. SPA was calculated from the difference between post- and pre-exercise pain levels. Participant's saliva was collected at several timepoints for cortisol and IL-6 levels quantification. Their waking cortisol response was calculated to reflect their cortisol regulation. Reactivity of IL-6 and cortisol was calculated to reflect changes in these measures during exercise.

RESULTS

IL-6 reactivity was significantly and positively correlated with SPA among participants with low back pain. In contrast, neither cortisol waking response nor cortisol reactivity was significantly correlated within the low back pain group. No significant differences in IL-6 reactivity, cortisol reactivity or cortisol waking response were observed.

CONCLUSION

These findings are the first to link SPA to an objective biomarker among people with low back pain. These findings help describe the physiological mechanisms of SPA and can support new clinical research that targets the inflammatory response of patients with chronic low-back pain and elevated SPA.

SIGNIFICANCE

This study reveals a correlation between SPA and an objective salivary biomarker of IL-6 in people with low back pain, improving our understanding of this clinically relevant subjective experience.

Task-based measures of sensitivity to physical activity predict daily life pain and mood among people living with back pain

BACKGROUND

Clinical interventions aim to improve the daily life experiences of patients. However, past research has highlighted important discrepancies between commonly used assessments (e.g. retrospective questionnaires) and patients' daily life experiences of pain. These gaps may contribute to flawed clinical decision-making and ineffective care. Recent work suggests that real-time, task-based clinical assessments may help reduce these discrepancies by adding predictive value in explaining daily life pain experiences. This study aimed to investigate these relationships by evaluating whether task-based measures of sensitivity to physical activity (SPA) predict daily life pain and mood, beyond traditional pain-related questionnaires.

METHODS

Adults with back pain (<6-month onset) answered pain-related questionnaires and completed a standardized lifting task. SPA-Pain, SPA-Sensory and SPA-Mood were, respectively, assessed as task-evoked changes in pain intensity, pressure pain threshold (back, hands), situational catastrophizing. Over the next 9 days, daily life pain and mood were assessed using smartphone-based ecological momentary assessment (EMA-Pain and EMA-Mood, respectively) with stratified random sampling. Data analyses estimated fixed effects (b) using multilevel linear modelling with random intercepts.

RESULTS

Median EMA completion per participant was 66.67% (n = 67 participants). After controlling for covariates, SPA-Pain was associated with EMA-Pain (b = 0.235, p = 0.002) and SPA-Psych approached significance with EMA-Mood (b = -0.159, p = 0.052).

CONCLUSIONS

Task-based assessment of SPA helps explain daily life pain and mood among adults with back pain, beyond traditional questionnaires. Adding task-based assessment of SPA may achieve a more complete picture of pain and mood in daily life, offering clinicians better guidance when prescribing activity-based interventions that are designed to modify daily life behaviour, such as graded activity.

SIGNIFICANCE

This study found that, among people with back pain, task-based measures of sensitivity to physical activity contribute additional predictive value for daily life pain and mood beyond self-report questionnaires. Findings suggest that real-time, task-based measures may help mitigate some of the shortcomings that are commonly associated with retrospective questionnaires.