Bike Fit and Low Back Pain

luke riding bikeIf you’re looking to maintain or improve your fitness this year, cycling may be a great form of exercise for you. Cycling caters for people of all abilities and can be quite social. Best of all, cycling puts less impact through your joints than alternative exercise such as running.Although cycling is great for people of all fitness or experience levels, back pain is a common complaint among cyclists. Back pain is commonly the result of either fatigue in the muscles that stabilise your back or that your bike is not properly adjusted to your body. Although you may not think about it, minor adjustments to your bike can significantly improve your pain, comfort and enjoyment while cycling. These adjustments are referred to as your “bike fit” and should be thought of as important as getting a shoe that fits correctly. If you intend on going for a ride it is easy to make a few adjustments to improve your fit. There are four main adjustments that should be considered. They are seat height, seat set back, seat angle and reach. To adjust these you should only need a tape measure and allen keys; if you need help with these adjustments most of your local bike shops will be able to help.

Seat height

Seat height is one of the most important adjustments to be made to your bike. Seat height is measured from your foot at the bottom of your pedal stroke to the middle of the seat. A good guide that is commonly used when fitting a bike is to measure your inseam and multiply it by 0.88. It is important that you set your seat height correctly as having it too high or too low can impact your body and cause discomfort or pain. Slight variances of the optimal seat height should be made depending on the thickness of the shoes being worn and rider experience (less experienced riders should have a slightly lower seat height). When your foot is at the bottom of the pedal stroke you should have a slight bend in your knee.

Too Low

• Increased loading through the front of the knee• Increases the work of hamstrings and calf musclesToo High• decreased core stability

• decreased ability to produce power

• increased stress through hamstrings and calf muscles

Seat set back

Seat set back refers to the position of the seat forwards or backwards on the seat post. The seat set back affects the loading of the knee and is therefore an important consideration in minimising potential knee injuries. When adjusting your seat set back, the tibial tuberosity (the bony lump below the knee cap) should be vertically over or behind the centre of the pedals when the pedals are horizontal to the ground. The amount of setback should depend on your preference and will be affected by your size, flexibility and experience. This adjustment should be measured while sitting in the part of the seat that you commonly sit and would be aided with the assistance of another person to check your body position.

Seat angle

Although a lot of cyclists choose to leave their seats flat, if you are experiencing back pain or discomfort it may be a good idea to try adjusting it to a slight angle. Commonly no more than 15 degrees of anterior slope should be added to the seat. At 15 degrees or more you may constantly slide forwards on your seat. There is also no exact angle to set your seat at; it will depend on your preference and body.  Reach is the distance to the handlebars from the seat. This measurement will vary greatly between riders and there is no exact measurement to achieve the perfect reach.  To get the perfect reach, you should be able to ride with a flat back, relaxed shoulders and arms and unlocked elbows. To achieve the perfect reach for you, you may need to change components, which any of your local bike shops will be able to help you with.

While talking about reach, it is also important to look at the drop from the seat to the handlebars. As with the reach, this adjustment is all about personal preference and may require some trial and error to get the best for you. A lower drop requires more flexibility and can be uncomfortable for some people. If the drop is uncomfortable raising it up may alleviate some pain and if you are experiencing back pain an upright position may be more appropriate. A drop where the handlebars and seat are level is a good starting point.

If you are experiencing back pain, existing or from cycling, the physiotherapists at Physionorth are able to provide assessment, treatment and exercises to help you get back to your best.

Luke Sherwood

Physiotherapist