Cardiorespiratory Fitness Predicts EEG-Based Somatosensory Responses Following Noxious Mechanical Stimulation in a...

Existing literature indicates that physical fitness affects endogenous pain modulation capacity, potentially impacting populations with impaired pain modulation ability. However, current evidence remains inconsistent, and there is a lack of studies employing objective measures to examine this relationship. The objective of this study was to assess whether individual physical performance levels can predict endogenous pain modulation variables in the electroencephalogram (EEG).

The EEG-based somatosensory response following noxious mechanical stimulation was recorded as pinprick-evoked potentials during conditioned pain modulation (CPM) in 32 healthy adults. To analyze physical fitness, cardiorespiratory fitness (CRF) was measured by using spiroergometric analysis, and strength was tested using isokinetic strength testing. Bivariate linear regressions were calculated to analyze a potential relationship between physical performance parameters and CPM variables.

Subjects with higher CRF exhibited a greater decrease in the event-related spectral perturbations in the CPM paradigm in the EEG and a correspondingly lower activation during a conditioning stimulus. The CRF predicted 14.0% of the variance in the activation during the conditioning stimulus (large effect) and 10.2% of the decrease in the event-related spectral perturbations in the CPM paradigm (moderate effect). No such relationship was observed between strength and EEG-based variables. When the groups were separated according to their physical fitness levels, no differences were observed between the groups during isolated mechanical stimulation.

The results indicate that CRF is associated with altered somatosensory responses during the CPM paradigm in our EEG-based pattern. Higher CRF appears to facilitate pain modulation processes without affecting central sensitivity to noxious mechanical stimulation, highlighting the potential benefits of higher levels of endurance exercise, but not strength levels.