Analysing the impact of Bikefit on comfort and pain – Part 2- Paul Visentini

Paul Visentini Research Review

Two recent studies investigated Bikefit parameters and how they related to comfort and pain, as well as fatigue, muscle activation, pedal force, centre of pressure (COP) and cadence. Verma (2016) was discussed in a previous blog.


Jose Ignacio Priego Quesada is a researcher at the University of Valencia who published the paper ‘Effect of bike-fit in the perception of comfort, fatigue and pain’ in 2016. He took a cohort of 20 club level cyclists and placed them on bicycle ergometers at static measures of knee angle of 20,30,40 degrees and trunk angle of 35,45,55 degrees.
After an initial fatigue protocol test they all returned on 3 separate occasions (3 different knee/trunk variables) and tested at 90RPM 50% of Po Max for 45 mins and reported on pain (VAS scale), comfort (Likert scale) and fatigue (Borg scale) . Importantly, the dynamic equivalents to static knee measures at bottom dead centre (BDC) were 30.0, 39.8 and 50.4 for the 20,30 and 40 degree static equivalents.

Results showed that limb pain generally and anterior thigh/knee pain specifically are worse in the 40deg static knee angle position than the 30deg position. The KN 30deg position is more comfortable for all trunk positions, and an upright trunk angle is most comfortable.

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KEY POINTS:

• Both studies (Verma & Quesada) are admirable using realistic valid and reliable measurement tools and protocols. Note should be taken as to the differing populations (commuter vs club cyclist) and the protocols (10’ efforts vs 45’). The Quesada protocol is closer to a clinical presentation with 45 minutes of pedalling and likely higher effort

• Also important are the small differences in pain or discomfort between experimental and control states, for both studies, which are in the range of 1-2 points on a 5 or 10 point scale.

• The findings are consistent with clinical observations that the more extreme positions of high or low knee angles show a greater level of discomfort and pain at the knee, as well as an upright trunk posture being generally more comfortable

• There were no differences for trunk pain or fatigue overall for the different knee and trunk variables, perhaps reflecting the 45 min protocol being too short

• As per Fonda (2014) static knee angle measures differ from dynamic knee angle measures.

• The protocol doesn’t identify rider’s normal position and any changes in position are ‘acute’ - this doesn’t allow for adaptation of the pedal stroke and posture to a new position

• Knee and trunk angle differences are large (10 degrees), limiting clinically relevant conclusions. The limitations of the research method are acknowledged, being that large changes in the dependent variable (knee angle) are required to find significant difference in pain and comfort. As bike fitters perhaps it shows that cyclists have a “normal” fit according to their basic body measures and kinematics, which relate to comfort. Achieving this might be step 1 in a bikefit. – the basic step.


CONCLUSION 

A cycling posture defined by a knee flexion of 30° (absolute value of 39.8 ± 4.0°) and a trunk flexion of 55° was considered the most comfortable posture. On the other hand, a posture involving 40° of knee flexion (absolute value of 50.4 ± 3.5°) and 35° of trunk flexion was reported as the most uncomfortable posture on the bike.

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