A male recreational cyclist in his mid-50s — we’ll call him Billy — was gearing up for a long charity ride over beautiful mountain terrain. He arrived at the University of Colorado Sports Medicine and Performance Center complaining of hand numbness, shoulder tightness, which sometimes led to arm numbness, and soreness occurring across multiple saddle options.
He had undergone multiple knee surgeries on both knees, including meniscus and patella repair. His ankle had also been repaired, resulting in a loss of range of motion.
The center’s cycling biomechanist, Charles Van Atta, worked with Billy to adjust his position in an effort to alleviate each of the issues.
Using the Specialized Body Geometry saddle fit system (casually known as the Ass-O-Meter), in which a patient sits with knees elevated on a memory foam pad, Van Atta discovered that Billy had wider than average sit bones (ischial tuberosities) for a male. His existing saddle was also wider than average. Billy did not exhibit a difference in leg length, and his pelvic shift was only mild. Billy’s hamstrings and hips were somewhat tight. He exhibited mild “scapular winging,” indicating there was room for shoulder strengthening. He also had mildly limited range of motion in his neck.
Van Atta mapped the saddle’s pressure points using the Gebiomized system. Using this method, a sensor pad is wrapped around the saddle and the rider is brought up to a moderate workload (either in the lab or on the road). A live version of the mapping captures data, and then a recording is replayed to determine pressure relief and any rhythmic weighting and unweighting of each side. Areas that do not see pressure relief are at risk for ischemia and saddle sores. A static version of the mapping illustrates any centers of pressure, indicating how a rider is transferring pressure from side to side. For example, riders stuck on the nose of the saddle will see very minimal weight shifts. Unstable hips can produce very large and/or random tracings.
In Billy, the test determined that he experienced left-sided pressure on the ischial tuberosity extending toward the pubic rami, a thin, flat portion of the pelvis bone.
Van Atta used the Retül system to acquire Billy’s biomechanical data and adjust his fit accordingly. “It is very important to us that we balance the influence of data with the knowledge we have acquired in the evaluation of the subject, and our assessment of their behavior on the bike through the filter of years of experience,” says Van Atta, who has conducted fittings for 15 years.
At the Performance Center, a smart trainer is used to deliver a subjectively moderate load during data capture, and is held consistent before and after positional changes are made.
“Attempting to adjust fit specifically based on power output can be a bit dubious, since you would need to control for heart rate and fatigue level, and would not have allowed any time for adaptation to occur on the altered position,” Van Atta cautions.
Billy habitually kept his heel low and was accustomed to riding a relatively high saddle height, producing eight to 12 degrees of knee overextension. In the interest of protecting his knees from excessive pressure, or making the pedaling feel unfamiliar, Van Atta lowered the saddle 34 millimeters to the point where his knee was only two degrees overextended with the heels still low.
“We are often balancing multiple priorities in our fits, such as his knee history and his concerns about saddle pressure,” Van Atta says.
Other specific changes included swapping Billy from a wide comfort saddle to a moderately padded medium-width women’s saddle, shortening his stem by 10 millimeters, and increasing its angle from +6 to +30 degrees. This raised his handlebars 20 millimeters and decreased reach by 30 millimeters.
Billy’s torso was now more upright by four degrees. His saddle pressure distribution went from a pattern of near full left-sided support throughout the pedal stroke to a significantly more balanced pressure transfer during pedaling.
Though his peak pressures increased slightly, the loaded area changed from the pubic rami to his ischial tuberosities, structures that are more tolerant of loading.
Billy’s posture also improved from a slightly forward flexed position to a more aligned spinal posture, which reduced pressure on the hands.
Billy left the session feeling immediately more comfortable on the bike.
“Diagnosis” is a collaboration between VeloNews and the University of Colorado Sports Medicine and Performance Center. Subscribe to VeloNews >>