Proper Bicycle Sizing
Perfect Fit: Preventing and Recovering from Bicycle Injuries
by ACE Physical Therapy and Sports Medicine Institute
Tips For Bicycle Riders.
- Seek help with injuries from a Physical Therapist.
- Purchase your bike at a “bike shop,” and ask them to if the bike is properly “fit” to your body.
- When pedaling, your knees should be almost “straight” at the bottom of the pedal stroke.
- Treat your injuries with the RICE principle.
- ALWAYS WEAR A BIKE HELMET.
Almost everyone can enjoy bicycle riding. Cycling will most likely increase over the next couple of decades as the “Baby Boomers” age and desire to stay active with non-weight bearing activities.
The most important aspect of cycling is that you have the perfect fit between your bike and your body type. Don’t attempt to fit your body onto a bike just because “it is the best model made.” A trained bike-fitting expert is the best resource available. The bike should be fit to your body based on the type of cycling (road vs. mountain) that you do most often. Fitting of your bike is not only important for comfort, but also necessary for injury prevention.
Overall Guidelines for Road Bike Sizing
1. Saddle Height and Tilt
a. Unclip your feet and place your heels on the pedals. When you get to the bottom of the pedal stroke, the knee should be fully extended (straight). You should be able to pedal comfortably with no excess hip movement while your heels barely stay in contact with the pedals. When you “clip in,” the balls of your feet are on the pedals which allows the knee to bend approximately 25 -35 degrees when performing the pedaling motion.
b. Most riders should have their saddle level with very few exceptions. Recreational riders should always have their saddle level.
2. Bike Frame Size and Handle Bar Position
a. Measure from the floor to the bottom of the crotch: multiply this measurement by 0.65. The frame is measured from the center of the bottom bracket to the top of the seat tube. (i.e. If crotch-to-floor measurement is 89cm, then 89 x 0.65 = 57.85 cm. The recreational cyclist should buy a bike fit with a frame that measures approximately 57-58 cm; however the elite cyclist should be more precise with their measurement.)
b. Recreational riders should have a more upright posture on the bike.
- Recommended measurement of the trunk angle is 40 – 80 degrees.
- Shoulder angle reach should be almost 90 degrees or less.
- Recommended torso angle of 50 – 60 degrees.
Most recreational riders will have a wider set of handlebars because this allows more control of the bike. The width for this type of rider should place the hands comfortably wider than the shoulders.
c. Elite cyclists will attempt to have their torso parallel to the road when they are competing in a time trial for better aerodynamics.
- Recommended measurement of the trunk angle is 35 degrees or less.
- Shoulder angle shoulder should measure a minimum of 90 degrees.
- Recommended torso angle of 30 – 45 degrees.
Additionally, elite cyclists use aero bars that enable them to bend at the waist and be almost parallel to the ground without putting an excess amount of stress on the back, shoulders, and upper extremities. The elite rider will have their arms and hands more narrow for better aerodynamics
c. Fitness riders should have a torso angle of 40 – 50 degrees.
3. Bike Pedals and Cleats
a. The ball of the foot should be over the centerline of the pedal axle. Most cleatless systems work best for riders with a men’s foot size of 9. If you have larger feet, you should slide the cleat backwards for stability. If you have smaller feet, you should move the cleat forward and force yourself to pedal more with your toes.
b. Rotational cleats: The goal is to have your foot positioned in the middle of the cleats arcing motion. Sit on a table and lean forward as if you were on a bike and let your feet dangle freely with the ankle flexed to 90 degrees. This will give you the angle that the cleat should be on the pedal.
c. You may need to place a “wedge” under the “knuckle” of the big toe. If the feet are angled in a way that the little toe is significantly lower than the big toe in the above position, you may have excess forefoot varus. A wedge can be purchased at most biking shops, but some people may require a custom orthotic.
d. The advent of the “floating” pedal has helped prevent injuries, but it has also decreased the amount of power generated. The usual “float” of 3-6 degrees is usually sufficient for the cyclist to avoid injury.
Injuries Associated with Improper Bicycle Sizing
Cycling injuries are common because of the repetitive nature of the cycling posture and the pedaling action. Note: This section is not about the traumatic injuries that occur if the cyclist crashes and falls off the bike!
1. Head and Neck Injuries
Cause: Improper fit on the bike or prolonged static posture during a long ride can cause neck injuries. Cyclists may experience pain and fatigue in the neck muscles when they are bent forward and have their heads up to see. This angle at the waist, although great for aerodynamics, puts the neck into a hyperextended position.
Prevention: To prevent neck pain and trauma from prolonged posture, attempt to sit with the torso more upright. The cyclist should train the rear neck muscles to build strength and endurance while stretching and strengthening the front neck muscles.
Note: Neck injuries can also occur during an accident. If you crash, you should go see a medical doctor. Head protection (a bike helmet) should be worn at all times!
2. Shoulders, Elbows, Wrists, and Hands
Cause: Shoulder injuries occur when the saddle or handlebars are in the wrong position. When the shoulder is moved to a 90-degree angle, it can put a great deal of pressure and stress on the structures of the joint.
Prevention: If the saddle is too low or the handlebars are too high, then the shoulder joint will be near the 90-degree angle. When riding, be sure that the shoulder joint is not at the 90-degree angle for a long time.
Cause: Some riders may suffer from tendinitis after extensive bike time. Excessive riding (especially on rough roads) will cause the cyclist to grip the handlebars or brake lever aggressively. The vibration from the tires and maintained grip on the handlebars can lead to tendinitis in the elbow.
Prevention: During a ride, change hand position often. Beside proper bike fit, this is the most important aspect to prevent injury.
c. Wrist and Hand
Cause: Excessive pressure on the wrists while having the wrists bent for an extended period of time can cause wrist and hand injuries. If the saddle is fit improperly, the handlebars are too low, or the frame is too small, the weight on the hands and wrists will increase significantly.
Prevention: Don’t forget! Change hand position often during a long ride. The changing of the “grip” of the handlebars alleviates the excess amount of stress and stretch that is placed on these nerves.
d. Low Back: (Second most injured body part in the cycling community)
Cause: Low back pain usually stems from a poor fitting bike. The posture of the rider is one of the most important aspects in determining the origin of the low back pain. The pain could be secondary to anatomical conditions or be tight soft tissue in the hips, abnormal angles of the bones of the lower extremities, or too much pronation in the foot/ankle complex. This could alter the biomechanics of the pedaling motion, leading to low back pain.
Prevention: The lumbar spine (low back) is to be maintained in a postural curve that is referred to as lordosis. If the spine is bent too far either way, sway back or rounded back, episodes of low back pain can occur. Soft tissue tightness can be addressed with a good stretching and strengthening program.
3. Hip, Knee, Ankle, and Foot
Cause: Hips are usually injured from the repetitive nature of the pedaling action. Improper bike fit or improper pedaling technique can lead to tendinitis in several locations in the hip.
Prevention: It is important to correct the fit of the bike and treat the tendinitis or bursitis.
b. Knees (Most injured body part in the cycling community)
Cause: The nature of the pedaling motion forces the knee to move from the straight (extended) position to the bent (flexed) position, creating an environment in which many structures in the joint are put under a tremendous amount of stress. Tendinitis is the most common problem in cycling. Quadriceps, Patella, Hamstring and IT Band tendinitis can occur due to the pedaling motion. Patella Femoral Syndrome occurs when the kneecap does not glide up and down in a groove of the Femur properly. The primary cause of this problem is a seat/saddle that is too low.
Prevention: The cyclist should check the seat height, stance on the pedals, cleat position and their own anatomy. Saddle and cleat position must be proper or it can stress the knee. Excessive training or pedaling cadence can lead to “over-use” and cause damage.
c. Foot and Ankle
Cause: Most Foot and Ankle injuries are in the form of tendinitis secondary to abnormal stress and strain placed on the tendons during the pedaling motion. Abnormal foot mechanics can place stress on the Achilles and the other ankle tendons.
Prevention: A new cycling shoe or custom orthotic can alleviate most abnormalities in the foot mechanics and make the rider’s feet very comfortable.
Responding to Bicycle Injuries
If you do get injured, don’t assume that it will get better with time. With proper treatment, most soft tissue injuries take 6-8 weeks to heal. Treatment usually includes anti-inflammatory medication prescribed by a doctor and aggressive Physical Therapy. Physical Therapy treatments should include modalities to reduce pain and inflammation and exercises that will help to re-establish the normal function within the injury site. If the injury goes untreated, it can linger for months and never fully heal.
Biking is a great low impact cardiovascular exercise. It can be performed by all ages, but if it is performed on an improperly “fit” bike, it can cause injuries to various body parts. Soft tissue injuries are the most common and respond well to Physical Therapy treatments. If you plan to begin a “riding” program get a bike that is properly fit to your body and seek help with any injuries that you may experience from your local Physical Therapist.
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