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Six female CFS and eight control (CON) subjects (similar in height, weight, body mass index and physical activity level) performed an incremental cycle ergometer test to exhaustion, while changes in cerebral oxy-hemoglobin (HbO(2)), deoxy-hemoglobin (HHb), total blood volume (tHb = HbO(2) + HHb) and O(2) saturation [tissue oxygenation index (TOI), %)] was monitored in the left prefrontal lobe using a near-infrared spectrophotometer.

Heart rate (HR) and rating of perceived exertion (RPE) were recorded at each workload throughout the test.

• Predicted VO(2peak) in CFS (1331 +/- 377 ml) subjects was significantly (P < /= 0.05) lower than the control group (1990 +/- 332 ml),
• And CFS subjects achieved volitional exhaustion significantly faster (CFS: 351 +/- 224 seconds; Controls: 715 +/- 176 seconds)…
• At a lower power output (CFS: 100 +/- 39 W; Controls: 163 +/- 34 W).
• CFS subjects also exhibited a significantly lower maximum heart rate (CFS: 154 +/- 13 beats per minute; Controls: 186 +/- 11 beats per minute)
• And consistently reported a higher RPE at the same absolute workload when compared with CON subjects.
• Prefrontal cortex HbO(2), HHb and tHb were significantly lower at maximal Exercise in CFS versus Controls, as was TOI during Exercise and recovery.
• The CFS subjects exhibited significant Exercise intolerance and reduced prefrontal oxygenation and tHb response when compared with CON subjects.

These data suggest that the altered cerebral oxygenation and blood volume may contribute to the reduced Exercise load in CFS, and supports the contention that CFS, in part, is mediated centrally. [In the central nervous system.]

Source: Clinical Physiology and Functional Imaging, Jul 29, 2008. [E-pub ahead of print] PMID: 18671793 by Patrick Neary J, Roberts AD, Leavins N, Harrison MF, Croll JC, Sexsmith JR. Faculty of Kinesiology & Health Studies, University of Regina, Regina, SK, Canada; Faculty of Kinesiology, University of New Brunswick, Fredericton, NB, Canada [E-mail: patrick.neary@uregina.ca]