Introduction: Endurance athletes, especially speed skaters and cyclists, may suffer from  pain, early fatigue and a powerless feeling in the legs when cycling above specific 
exercise intensities. These complaints are associated with a disturbed balance between  the required and the actual blood flow. The causes of a disturbed balance are iliac 
vascular diseases, such as stenosis and kinkings. These abnormalities cause, amongst  others, a relative decrease in blood supply to the active tissues.  

Aim: This study investigates whether the pain, powerless feeling and early fatigue can be measured by use of independent pedal force measurements during an incremental 
maximal cycling exercise test. Beside that, this study investigates whether the location of the iliac artery can be determined. 
 
Materials and Methods: In total, n=28 cycling related patients with a left unilateral iliac artery disease and n=9 control subjects participate in this retrospective study. The 
patients were subdivided in respect to the affected common iliac artery (LC), external iliac artery (LE) and the combination of both (LCE). The group sizes were respectively 
n=5, n=16 and n=7. All performed a maximum voluntary incremental exercise test on a bicycle ergometer (LODE ® Excalibur Sport (925900)). Pedal force was measured for both 
legs using strain gauges, implemented in the crank of the cycle ergometer.  
 
Two types of (derivative) parameters were assessed: parameters as a function of the 
pedal revolution (1) and parameters as a function of the ergometer load (2). The 
parameters were:  

1. Maximum-, minimum and Δpedal force and as a function of a revolution
2. Maximum-, minimum pedal force, crank angle of maximum and minimum force, the mean power of revolution, mean power of 90-degree crank angle phase, the 
   mean power of cycling-related-muscle phases and the mean power of muscle phases nourished by the internal and external iliac arteries. 

The pedal force parameters as a function of the revolution were analysed by determination of the proportion of patients with the healthiest leg as the strongest leg, in 
relation to the patients with the abnormal leg as the strongest leg. All pedal force parameters as a function of the ergometer load were post-processed by a algorithm based upon a least summed square fitting technique, in order to asses the data by two linear fits with a forced intersection at the inflection point. The slopes of both linear fits were analysed for all study groups. 
 
Results: The results of (1) reveal a suspicious tendency; affected legs perform better at low intensities, and the healthy legs pull by at higher exercise intensity levels. The 
results of (2) reveal significant different slopes for low and high exercise intensities for the patients’ left leg exerted mean power of two phases of the pedal revolution, namely 
the 90-180°-phase and the 180-270°-phase (CI=[.134,.668] & p=0.004 and CI=[-.067, -.222] & p<0.001).  For patients with an abnormal left common iliac artery (LC and LCE), the slope of the difference between the mean power of the left and right leg during the 341-128°-phase at high exercise intensities is significantly lower than this slope at low exercise intensities (LC: CI=[.003,.859] & p=0.049, and LCE: CI=[.059,.434] & p=0.011). For controls and patients with a left singular abnormality in the external iliac artery, this significance is not observed.