Evaluating Arterial Blood Flow Limitation Using Muscle Oxygenation and Cycling Power

To explore the combination of measuring muscle oxygenation with near-infrared spectroscopy (NIRS) and cycling power during provocative incremental exercise for the detection of iliac arterial blood flow limitation (IAFL) in an otherwise healthy, well-trained cyclist.

Case report and methodological pilot study.

University research setting.

A well-trained amateur competitive male cyclist, aged 31 years, presenting with symptoms consistent with IAFL, but in whom diagnostic imaging was equivocal.

Four ramp incremental cycling tests performed on separate days to exercise intolerance, in a randomized order, in either typical race position (RP) or modified upright position (UP).

A novel ratio of unilateral cycling power to NIRS-derived muscle oxygenation termed "power-deoxygenation factor" was measured during provocative incremental exercise and compared with other NIRS-derived measures of vascular responsiveness and performance outcomes across the 2 body position conditions.

The power-deoxygenation factor was able to show clinically important, progressive differences between the affected and unaffected limbs, coinciding with worsening performance impairments related to the body position that were not detected with traditional measures of vascular responsiveness taken after exercise.

This method was used to detect bilateral differences consistent with IAFL in a cyclist where traditional diagnostic criteria were equivocal, but subsequent intraoperative findings confirmed the diagnosis. A similar screening test could be performed noninvasively and without requiring specialized medical care. Future work should investigate the validity and sensitivity of this methodology to improve the ability to identify and monitor athletes with IAFL.