Muscle and cerebral oxygenation during exercise in fibromyalgia: a near-infrared spectroscopy study

We studied muscle and brain oxygenation during submaximal and peak exercise in patients with fibromyalgia (FM), a condition characterized by pain and fatigue, compared with age-matched healthy controls (CON).

The participants (FM, n = 16; CON, n = 17) undertook a step incremental cycle spiroergometry until exhaustion. Changes in oxyhemoglobin (O₂Hb), deoxyhemoglobin (HHb), total hemoglobin (tHB), and tissue saturation index (TSI%) using near-infrared spectroscopy were assessed in the vastus lateralis (leg) and biceps brachii (arm) muscles as well as the brain prefrontal cortex. Vastus lateralis blood flow (Q̇_VL) was calculated from whole-body oxygen consumption (V̇O₂) and HHb values. We analyzed between-group differences at absolute workloads and relative to V̇O_2peak.

No significant between-group differences emerged in leg or arm oxygenation. Q̇_VL was lower in FM at 50% (0.066 [0.022] vs. 0.080 [0.028] a.u.), 75% (0.082 [0.020] vs. 0.106 [0.039] a.u.), and 100% (0.091 [0.036] vs. 0.111 [0.041] a.u.) of V̇O_2peak, but similar at submaximal absolute workloads. Cerebral HHb values were higher in FM at 75 (1.09 [2.23] vs. -0.18 [1.38] μM) and 100 W (2.20 [2.96] vs. 0.06 [1.92] μM) but not at relative workloads. Cerebral TSI%, O₂Hb and tHb were not significantly different between groups.

Leg oxygenation or peak exercise cerebral deoxygenation in FM do not differ from controls. Q̇_VL was lower at peak exercise in FM. These results present evidence that exercise intolerance in FM may rely on other mechanisms than muscle oxygenation. Trial registration ClinicalTrials.gov, NCT03300635. Registered 3 October 2017-retrospectively registered. https://clinicaltrials.gov/ct2/show/NCT03300635 .