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.
The first was by Rachita Verma , who is an Indian Physical Therapist undertaking a PHD in Denmark focussing on seat position influences on discomfort and biomechanics in cycling. Her 2016 study placed 21 commuter cyclists on an ergo in a neutral position, and she compared an initial 10min effort at 100W with 5 other 10min efforts in different seat positions then neutral again. General body discomfort was measured on a Visual Analogue Scale (VAS). Also measured was activation of the quadriceps, calf and tibialis anterior muscles, cadence, pedal force and seat pressure. Neutral position was assigned according to the 106/107% of crotch height rule (Christiaans & Bremner 1998) giving an average of 90.2+/-3.6cm seat to pedal spindle.
Image reproduced from research paper, https://linkinghub.elsevier.com/retrieve/pii/S1050-6411(16)00025-0
Key Points of the research
• The findings are consistent with clinical observations that the more aggressive positions of seat up, seat back or combined, can lead to a greater level of discomfort and pelvic movement (COP changes) in cyclists
• Just sitting and pedalling for a period of time makes the cyclist uncomfortable as all were sorer after the last 10min period regardless of the order of test positions. This is consistent with many studies especially those covering long cycling events
• Calf muscle increased activity with seat up or seat back, and a concomitant decrease with seat down, has been shown in previous studies and is also consistent with clinical practice – raising the seat can make the calf/ankle complex more active
• This lab based cross-sectional study may not represent how these cyclists really pedal as the standardised set-up doesn’t necessarily represent the usual bike set up of the cyclist. Further the cyclists haven’t had the ability to adapt to a potentially new position.
• The power output was set at 100W for all testing conditions. This was acknowledged as sub-maximal. It is my experience that most pain presentations are as a result of riding at higher levels of effort
• Visual Analogue Scale for pain or discomfort is a validated measurement tool BUT the differences whilst significant were very small being 1-2 points, which is on the lower end of minimal clinically important difference in most pain studies
• The population was ill-defined being “recreational sportsmen using a bicycle as a regular form of transport” – not very generalizable to a typical Bike Fit cohort
• The assignment of the “neutral” set-up position is an interesting discussion point. The LeMond calculation for the same cohort (Mean crotch 85.5 x 0.883 = 92.5cm) is 2+ cm higher. The many different methodologies for seat height vs leg length calculation are consistently unreliable when compared.
As per Verma’s conclusion, discomfort increases with time, discomfort and pelvic movement increases with up or back seat positions, and the calf muscle is obliged to work if the seat is up or back. The measures used were excellent tools and a great model for future research of position vs pain vs biomechanics, but perhaps the protocol might be stronger with a more realistic bikefit cohort, with their own bikes or set-up positions, and a more challenging level of effort. As a bikefit community the notion of “neutral” requires ongoing discussion.
Verma, R., Hansen, E. A., de Zee, M., & Madeleine, P. (2016). Effect of seat positions on discomfort, muscle activation, pressure distribution and pedal force during cycling. Journal of Electromyography and Kinesiology, 27, 78-86.
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