The most important contact point on the bike
We’re gearing up for the season for bike fitting! Late winter/early spring is the time when cyclists may purchase a new bike or look towards longer rides outside as the weather starts to change. Today I want to highlight what is arguably the most important contact point on the bike - the saddle.
Everything about bike position starts with the saddle and pelvis position. A rider’s pelvis position in relation to the crank arm and bottom bracket has a huge influence on pedaling mechanics, muscular recruitment and power output. Below are a couple important things to keep in mind when blending saddle position with a rider’s physiology, goals, and style of riding.
The higher the saddle height for a given fore/aft position, the larger quadriceps recruitment due to their mechanical advantage at higher knee extension angles vs. the hamstrings. The lower the seat, the bigger hamstring recruitment.
Higher saddle heights increase the work that the glutes need to do to stabilize the pelvis in the saddle (and even the lumbar spine). Pelvis stability directly affects power transfer into the pedal. When you put force down into the pedal and your pelvis isn’t stable, it’s going to just rock out of the way and watts can be wasted. Conversely, lower saddle heights decrease the mechanical advantage of the glutes because they are in a further lengthened position at the top of the pedal stroke (lower saddle = great hip flexion angle at the top of the pedal stroke).
The tilt of the saddle (and the ergonomic contour) can influence pelvis posture in the saddle. When a saddle is too nose-up, the pelvis rolls into more of a posterior tilt, creating more groin pressure and putting all the structures along your back on stretch. When a saddle is too nose-down, it can move the rider and force vectors more anteriorly. This can put excess load on the other two contact points of the bike - hands and feet.
The calves have a much smaller influence on power output than the glutes, quads and hamstrings (ideally). The foot and ankle should primarily be responsible for transmitting power from the upper leg into the pedal. When you have a weak or unstable forefoot, you’re putting a large amount of force through an unstable lever. Not only is this a potential risk for injury but it can also negatively impact your performance and pedaling efficiency. Low saddle positions can cause a rider to excessively drop the heel, which can lead to strain on the Achilles tendon. Higher saddle positions can lead to more toe-pointing throughout the pedal stroke and more calf recruitment.
Saddle setback (how far fore/aft the saddle is) alters muscular recruitment because the rider’s center of mass shifts either forward or behind the base of support. In general, the further forward a saddle is, the more the quadriceps are utilized (think triathlon and TT positions). A further setback saddle will bias the hamstring complex, as the leg pulls through the bottom of the pedal stroke.
These are just a couple things to keep in mind when configuring saddle position to best match the rider’s anatomy, movement preferences, riding style and goals! As always, getting in to see a good bike fitter can assure that you are set up in the most optimal position for you!
