By Amanda Nayfield
A misfit bike can lead to worse things than an uncomfortable ride.
Neck and low back pain, carpal tunnel syndrome, patella-femoral pain, Achilles tendinitis and hip dysfunction can all result from riding too long on a bike that doesn’t fit you. Tailoring a bike to fit your individual needs can dramatically reduce the risk of injury and make for a more efficient and enjoyable ride.
Every individual is different, every bike is different, and the skill and style of the rider also come into play when it comes to fitting, so an in-person consultation is the best way to dial in the right fit. Many bike shops have fitting technicians to get your bike roughly where you need it. If you are interested in a more customized fit, consider seeing a physical therapist for a biomechanical assessment of your movement patterns and individual restrictions.
If you want some basic guidelines for adjusting your bike to fit you (and not the other way around), read on.
The first thing to consider when choosing a bike is the size of the frame. For road bicycles, size is typically based on the length of the seat tube (the tube that the seat comes out of), and is measured in centimeters. The rule of thumb on a road bike is that you should be able to stand over the top tube of the bike with 1 to 2 inches of clearance, while also maintaining a 45-degree angle at your torso (relative to the floor) when you are seated on the bike.
For mountain bikes, sizing parameters can vary depending on the intended use of the bike (cross country vs. gravity oriented). Most modern mountain bikes are sized “small,” “medium,” “large,” etc., and manufacturers provide intuitive guidelines to help you find the right fit. The same clearance rules apply; however, reach and other fit criterion may vary depending on the style of the bike. For example, a cross-country hardtail will have slightly different fit characteristics than an all-mountain full suspension bike. It is best to visit experts at a local bike shop for guidance on matching fit with intended ride style, then address detailed fit issues from there.
Once you have the right frame size, you can move on to adjusting the saddle. Finding the correct front to back, or fore-aft, adjustment will improve the mechanics at the knee and ankle, lowering the risk for injury and improving your ability to use the hamstrings and quadriceps effectively during a full revolution. This measurement requires a plumb line (weighted string) to measure the position of the knee over the toes. First, pedal at a steady pace with slight resistance for about a minute, then stop when the crank arm is horizontal. From that position, place the string at the bony prominence below your knee (tibial tuberosity) with the weight dangling above your foot. If the weight is not directly over the middle of the pedal, aligned with the ball of your foot (metatarsal heads), adjust the fore-aft location of your seat until it is.
Adjusting the seat height can prevent unnecessary motion in your low back and pelvis. While precisely measuring the angles at the hip, knee and ankle is the most accurate way to achieve optimal efficiency, a good rule of thumb is to shoot for a 35-degree bend of your knee at the bottom of the pedal stroke with your hip slightly flexed. For a mountain bike, the suggested knee angle is 32–40 degrees or lower for more experienced riders. Seat height adjustments are frequently made in mountain biking to account for variable terrain, so it is a good idea to make a mark on the seatpost at the ideal height for flat riding.
Saddle angle can also be adjusted for a more comfortable ride. Whether the saddle is horizontal or has a slight rise/decline, you should be able to sit on it hands-free without slipping forward or backward.
If you ride with clipless pedals, correct positioning of your cleats is essential to protect the knees. Also, the cleat position changes the lever arm at the forefoot, affecting the effort required of the calf muscles.
Most bike fitters suggest that the cleat should be positioned under the ball of the foot or slightly behind. This is an adjustment, however, that can be very different among individuals depending on foot structure. The most important thing to remember is the cleats should be set up so that the hip, knee and ankle are in a straight line. If the cleats are too far in or out, it can cause the knee to collapse inward.
Correct positioning of the handlebars helps keep the trunk elongated for comfort and is important for shoulder, wrist and neck health. Poor handlebar position can create feelings of being too compact or too stretched out. Generally speaking, the handlebars should be a few inches lower than the seat and behind the front axle. Your trunk angle should be about 45 degrees, and the shoulder angle should be around 90 degrees.
Other nuanced fit adjustments may include handlebar rotation and width, and brake lever position. When making these adjustments, aim for a neutral or slightly extended wrist angle.
Once you have the bike fitted to your body, think about form and body mechanics while you are riding. It is common for riders to elevate shoulders and extend the upper part of the neck, contributing to neck and arm pain. Remember to keep your shoulders relaxed and your neck in a neutral position (ears over shoulders with your chin slightly tucked). It is also very important to pay attention to your knee position throughout the pedal stroke. The most common movement dysfunction is allowing the knee to drop inward. Make sure your knee stays in line with the middle toe.
If you are having aches and pains with biking or want to improve your efficiency, these guidelines are a good place to start. x