"Understanding the mechanics of cycling allows the rider to position themselves for optimal comfort and efficiency with the aim to improve performance and to reduce the risk of injury"
What to assess?
- Athletes anatomical alignment
- Musculo-skeletal function
- Bike set-up
- Training history and regime
Several Studies Highlight neck and back as main source- Wilber et al 85% cyclists suffered with one or more overuse injury:
48% neck injuries
41.7% knee trouble
36.1% groin and buttock
31.1% hands
30.3% back
Study also fund female cyclists are 1.5 x more likely to develop symptoms.
Chronic injuries...why?
- Higher intensity training methods- too many miles, too many hills, use of inappropriate gear selection.
- Changes in bike set up/rider geometry- Maladjusted cleats, improper saddle height, Seat tube angle.
Biomechanics of Cycling:
Single pedal cycle = power phase from 12 o’clock- 6 o’clock. Generates forward momentum. Force produced via extensors of lower limb:
Quads Glut Max Hamstrings(act on Hip) Calves (Act on ankle)
Recovery Phase via Flexors:
Hip Flexors Hamstrings(Act on Knee)
Calves(Act on Knee)
At 12 no knee flexion but extends 75° through power phase to 35° flexion at beginning of recovery at 6 o’clock.
NB: During power phase you will see normal medial drift of the knee- STJ pronation and Internal Rotation of tibia but were looking for excessive amounts!
Biomechanics of the lower limb:
Assessment:
Leg length discrepancy
Hip position and range of motion
Foot position relative to tibia (External or Internal)
Foot Alignment – Rearfoot to Forefoot
Needs to be done non-weight bearing, stance, gait and with the patient on their bike (Bike Gait Cycle).
Most common foot pathology causing problems is a forefoot varus…Why?
 | In order to get medial ground contact- either or both the midtarsal/sub-talar joint have to excessively pronate during mid-stance, also see xs Internal tibial rotation. |
Hot foot- focal pressure on met heads forces blood from fat pad, this in turn causes heat to build up which is normally dissipated by the circulatory system.
Generalised Metatarsalgia- cycle shoes very thin and narrow also tight toe straps.
Differential Dx = Mortons neuroma.
Bike set up:
Saddle height: changing saddle height alters joint angles, muscle lengths and amount of force a muscle can produce.
Optimal saddle height = 105 –107% of leg length. This is used for long distance or moderate bike rides as exerts least amount of energy via O2 consumption.
Maximum Saddle Height= 109%. Used for track or tri-athletes to produce maximal power output.
 | Saddle height affects the activity of the muscles in the leg. As saddle height decreases amount of muscle activity in quads and hamstrings increases. Greater saddle height allows cyclists to pedal with greater ease especially at high work loads. |
With Saddle Height at 6 o’clock the optimumKnee angle 25-35°
Crank length: a change can alter distance between saddle and pedal. Increase length= greater torque production but decrease crank length increases muscular tension, lead to earlier fatigue , used for track.
Crank too long- xs hip and knee flexion – connective tissue injuries linked to too long crank length.
Seat Tube Angle (STA): between top tube and seat tube this determines rider comfort level.
Competitive road cyclists STA 72°-76° for optimum performance, Tri-athletes like STA 76°-78°.Steeper STA allows riders body weight to be positioned further forward over crank, greater comfort, efficiency and power.
A shallow STA displaces the hips posterior and will favour quad strength , tends to restrict power,due to the larger angular change of the femur. Suits riders of long distances
A steeper STA moves the hips Anterior and favours hamstring strength, it also allows higher crank speeds due to the reduction in angular change of the femur.
| Saddle Fore-Aft Position: rear of the cycle behind a vertical line down to the centre of the crank.Saddle should be positioned so a straight line from the patella to the pedal axle is achieved when the crank is at 3 o’clock.This enables hip and knee Ext and Flex muscles to be fully utilised. This minimises the strain on the knee. Saddles that are too far back cause the cyclist to reach for the pedal and stretch ITB. |  |
 | This rider shown has the saddle too far back and not getting good power transfer to the pedals. Shoe-Pedal Interface (Connects the foot to the pedal and experiences torsional forces similar to that in gait) Placing ball of foot directly over pedal helps decrease stress across knee ligaments and is most efficient. More forward foot position- with pedal either in arch or hell area increases hip extensor and flexor activity but reduces ankle ROM. |
Ball of foot slightly in-front of axle the effective lever arm from ankle to pedal is shortened = requires less force to stabilise foot and puts less strain on Achilles tendon and Gastroc. Favoured position of tri-athletes and time trial as it allows them to produce more force when using large gears but limits ability to pedal at high cadences.
 | Ball of foot slightly behind pedal axle- lengthens lever arm making it more difficult for the foot to act as rigid lever, Achilles and Gastroc have to work harder. Favoured by track cyclists allows them to pedal at high cadence during fixed gear events. |
Chronic risk injuries:
“Front of the Knee”
Patellar tendonitis
Patellofemoral syndrome / Chondromalacia patella
Causes:
pushing big gears- cadence to low
Saddle too low or too far forward
Foot to far forward on pedal
Crank arms too long
Patella Tendonitis:
Inflammation of the patella tendon originating from the tibia, usually due to overuse. With repeated irritation thus inflammation scarring and tearing can occur. Pain is usually centred on the lower tip (inferior pole) where it connects to the tendon. If the tendonitis is severe you may get localised swelling – Bump or lump just below your knee. Pain is felt in the front of the knee below the patella, when you pedal or walk upstairs, but it will probably be worse descending the stairs. It will also hurt when you palpate or press on the tendon itself.
Patellafemoral syndrome / Chondromalacia patella:
The knee is like a ball and socket joint, with the ball at the bottom of the femur and the socket at the top of the tibia. Protecting the front is a third bone the patella which is embedded in the quad tendon and which slides in shallow groove on the femur and tibia.
Chondromalacia is irritation of the cartlidge behind the knee. Pain is often felt in the front of the knee when the knee joint is bent or flexed. It can often be caused by mal-tracking patella, poor foot mechanics or musculature problems.
It is more common in women due to their wider pelvis.
“Back of the legs”
Hamstrings / Gastrocnemius
Causes:
Saddle to high or too far back
Too much pedal float
Leg length discrepancy
“Inside of the knee”- medial
Medial collateral ligaments
Medial meniscus
Causes:
Cleat position to wide so the foot is held externally rotated or like charlie chaplin!
Excessive knee frontal plane motion
Too little pedal float
“outside of the leg”- Lateral
Iliotibial band
Lateral collateral ligaments
Lateral meniscus
Causes:
Cleat position to narrow- foot is held inwards
Too little pedal float