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20081023-Cen Bike Standards
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PRACTICAL MANAGEMENT
Road Bicycle Fit Marc R. Silberman, MD,*‡ David Webner, MD,† Steven Collina, MD,‡ and Brian J. Shiple,
(Clin J Sport Med 2005;15:271–276)
P
roper roper bicycl bicyclee fit is essent essential ial for comfor comfort, t, safety safety,, injury injury preventi prevention, on, and peak performance. performance. The goal is to balance all of the issues at hand, optimize power and aerobic efficiency, and avoid injury. At an average of 80 revolutions per minute, a cyclist may complete over 5400 revolutions during an hour ride, up to 30,000 revolutions over a 100-mile course, and 81,000 revolutions in the span of 1 week. Compounded over a season, one can see how overuse injuries develop. develop. If properly fitted, the majority of cyclists training correctly will remain injury-free. Bicycle fit consists of static (measurements at rest) or dynamic (measurements while riding) evaluation. Dynamic fit also also invol involves ves video video analys analysis is with with concom concomita itant nt heart heart rate, rate, wattage, and pedal torque readings. There are 3 contact areas a rider makes with the bicycle, addressed in the following order (Fig. 1): 1. Shoe-cleat-pedal interface 2. Pelvis-saddle interface 3. Hands-handlebar interface Whether a weekend warrior or elite Olympic Olympic hopeful, all cyclis cyclists ts are positi positione oned d the same, same, with with the except exception ion of the hands-handlebar interface. A recreational rider may prefer to be positioned more upright.
STATIC FIT Shoe-Cleat-Pedal Interface For maxima maximall powe powerr and injury injury preven preventio tion, n, the cleat cleat should be positioned so the first metatarsal head lies directly over the pedal axle (Table 1; Figs. 1, 2). For leg length discrepancy, the shoe-pedal interface can
should be corrected. If a rider has excessive malalig the lower extremity, canted shims or wedges can be u lifts and most orthotics are not sufficient for cycli driving force is through the metatarsal heads. 2
Saddle Height
Histor Historica icall studie studiess on formul formulas as to determi determi height have been discussed previously by De Vey M These formulas are designed to fit a rider in the high position to produce the most power at a minimal aer without placing undue stress on the lower extremity. position is that of an almost fully extended leg wh bottom of the pedal stroke. A formula endorsed by 3-time Tour de France Greg LeMond and his coach, Cyrille Guimard, takes t inseam inseam length length in centim centimete eters rs and multip multiplie liess it equal the saddle height, measured from the center o tom bracket to the top of the saddle 4 (Fig. 3). An alternative method is to use knee angle ments. The knee should be flexed 25 ° to 30° from f sion, with the pedal in the 6-o’clock position 5,6 Cyclists who tend to pedal on their toes can a higher saddle height, whereas those who pedal b through through and dropping dropping their heels will prefer a low Achilles tendinopathy can result from excessive stre position is too high or from excessive force in the do if the saddle is too low. 1
Saddle Fore-Aft Position
When theup pedal is positioned at 3 o’clock (for Sign to vote on this title parallel to the ground), a plumb line dropped from th Useful should useful patella Not pole of the hang directly over the p (Fig. 5). Sprinters and time-trialists will adjust their sad
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Clin J Sport Med Volume 15, Number 4, J
Silberman et al
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TABLE 1. Static Fit: Order of Adjustments and Recommended Neutral Position 1. Foot-shoe-cleat-pedal interface First metatarsal head lies over pedal spindle 2. Saddle height A. Knee angle flexed 25 ° to 30° short of full extension when the pedal is at the bottom of the downstroke B. Saddle height, measured from center of bottom bracket to the top of saddle, equal to the rider’s inseam length in centimeters multiplied by 0.883 C. Leg extended fully and comfortably (without any pelvis rocking) with heel resting on back of pedal at the bottom of the downstroke (6-o’clock position) 3. Saddle fore-aft
4. Saddle tilt 5. Stem height
6. Stem length or extension
Plumb bob dropped from the inferior pole of the patella should fall directly over the pedal spindle, with the cra positioned forward and parallel to the ground (9-o’clock position) Note: Recheck saddle height after making fore-aft adjustment Level to the ground 0 to 3 inches below the height of the saddle With the hands on the brake hoods and the arms slightly flexed, the torso should flex to 45 ° in relation to the to With the hands in the drops, the torso and top tube angle should be about 30 ° With a rider comfortably in the drops with the elbows flexed about 20 degrees, and the knees at their maximal h forward position, the distance between the elbows and knees should be a small distance, up to 2 inches (make rider can stand and climb without hitting knees against bars) With the hands in the drops, looking down, the front hub should be obscured by the transverse part of the handle
flexed position, prefer a slight downward tilt to decrease saddle pressure on the perineum.
bars, for a more comfortable position at the exp aerodynamics. The rider accounts for 65% to 80% of the to dynamic drag. 9 The lower the stem, the more aero Stem and Handlebar Height a rider can be, though at the expense of comfort and Stem height is more of a subjective measurement, but is An average size male cyclist can decrease his fronta extremely important in terms of aerodynamics, power proabout 30% by moving from the upright touring pos duction, comfort, and injury prevention. With theYou're hands on Reading a Preview a racing position in the drops. If forward-flexed exce the brake hoods and the arms slightly flexed, the torso should 7 maximal sustainable power is often reduced due to dim flex to about 45° in relation to a nonsloping Unlock top tube full access with a free trial. crank torque through the top of the pedal cycle. (Fig. 5). When the hands are in the drops, the torso should Indurain (5-time Tour de France champion) and flex 60° (Fig. 1). The vertical distance between the top of Armstrong (6-time champion) are two notable cycl the saddle and the top of the stem or bars shouldDownload be 1 to 3 With Free Trial an upright time-trial position despite the total aerod inches (5–8 cm) below the saddle, depending on the athlete’s 4,8 resistance. flexibility (Fig. 3). A recreational rider may prefer to sit Handlebar tilt is a personal preference, but mos more upright, with a shorter reach and higher placed handle prefer the lower curve and brake hoods to be slightly e Too often, the bars are tilted downward or the hood low, forcing the athlete to overreach. This may result use strain, increased pressure on the hands,and loss 1 to vote on this title through theSign core.up
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Clin J Sport Med Volume 15, Number 4, July 2005
Road
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FIGURE 2. Cleat is positioned so first metatarsal head lies directly over pedal spindle.
DYNAMIC FIT
that are active in the recovery phase are firing pri reduce resistance versus the contralateral propulsive A cyclist’s performance capacity is determined by three though most athletes believe they pull up on the ped components: the athlete’s metabolism, biomechanics, and aerocycling, this is rare in road cycling during steadydynamics. A dynamic evaluation assesses all three of these and is not essential to an efficient seated pedal stroke parameters. on elite cyclists during steady-state cycling have sh Whereas the office examination of the athlete and bieven on the upstroke, the vector of forces is dow cycle is well suited for measuring geometric values, no labothe opposite direction of the pedal motion. 11,12 The ratory investigation can simulate the real-world performance, recovery phase is not lifted as fast as the crank is rota balance, and aerodynamic issues that confront the athlete out elite cyclist, however, exhibits reduced negative for on the road. Video analysis, measurement of wattage, heart rate, 10 the upstroke, in addition to decreased time in produc and pedal torque comprise a dynamic bike fit. Any adjustYou're Reading a Preview forces.13 ments to position can then be re-evaluated in terms of objective There are commercially available tools to evalu rider physiological measurements. If a stem is lowered tofull proUnlock access with a free trial. torque. Spin Scan (Racermate) provides net torque vide a more aerodynamic position, but the rider is now too color graphic depiction of one 360 ° pedal revolutio flexed to produce power effectively (demonstrated by lower wattdown intoTrial 15° segments based on the rider’s peda age, higher heart rate, and/or ineffective pedal torque numbers With Download Free nique. An efficient or optimal pedal stroke pattern is or pattern), then the position change was ineffective. one with a flatter or more even bar graph. 10 An exam Pedal Torque and Spin Analysis national team riders demonstrated that maximal torq Muscles involved in the power phase drive the crank the downstroke is what differentiated elite athletes downward in an effort to rotate the crank, whereas the muscles recreational rider.13
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Clin J Sport Med Volume 15, Number 4, J
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the most common, and by localizing where the kne sometimes all that is needed for correction is a smal adjustment (Tables 2, 3). Posterior neck pain and scapular discomfor caused by an elongated reach and can be remedied by a rider in a more upright position. Ulnar neuropathy palsy, a common ailment, results from excessive pre the handlebars. Contributing factors may be bars po too low or a saddle too far forward or tilted downwar symptoms may be rectified by increasing handlebar p changing hand position frequently, adjusting hand and/or height, and rechecking the saddle height. Lo pain may occur in riders who are overstretched on t Riding more upright, raising stem height, and shorten length may resolve back discomfort (Table 2). FIGURE 4. Saddle height set so knee angle is 25–30 degrees A saddle too high may lead to lower leg sym with pedal in 6 o’clock or dead bottom center position. Bert tibialis anterior, or Achilles tendinopathy. A saddle Webster performing bike fit. Photo by Mike Spilker. with excessive heel drop at the bottom of the pedal stro also cause Achilles pain. Correcting saddle height dress these problems. Morton’s neuroma or foot neuro In terms of bike fit, pedal torque appears most useful common in cyclists and may be due to cleat positio when evaluating injured cyclists and implementing drastic tightness, or shoe-sole irregularities (worn sole with cl position changes for those riding with aero-bars. Further re pushing through; Table 2). search needs to be conducted before a pedal torque examinaKnee pain is the most common ailment of cyc tion can be universally recommended. may be due to training error, poor bike fit, or both. A knee discomfort may be due to a saddle position too too afar forward in addition to excessive climb You're Reading Preview INJURIES AND AILMENTS big gears, or too long a crank arm. Adjusting saddle De Vey Mestdagh3 has described cycling posture based and modifying Unlock full access with a free trial.training can improve conditions suc on posture height and posture length. Complaints related to tellar tendinosis and patellofemoral pain. Posterior k the lower extremity may be addressed by adjusting the saddle may occur if the saddle is too high or too far back (posture height), whereas complaints related to Download the upper With adjustment as well as limiting pedal float can elimi Free Trial extremities, neck, and back may be addressed by adjusting the discomfort. Medial knee pain can develop from outward handlebars (posture length). The genital, pelvic, and lumbosacral region all fall in an intermediate area. Knee injuries are toes and/or excessive float in the pedals and can be ad
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Road
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TABLE 2. Overuse Injuries, Contributing Bicycle Posture, and Bicycle Adjustments Ailment
Contributing Position
Bicycle Adjustment
Posterior neck pain, scapular pain for clarity
Too great of a reach, handlebars too low, too stretched out
Hand neuropathy (cyclist’s palsy, ulnar nerve)
Too much pressure on bars, handle bars too low, saddle too far forward, excessive downward saddle tilt
Low back pain
Too stretched out
1. Ride more upright, shorten reach 2. Raise stem height 3. Shorten stem length 4. Ride with hands on hoods or tops of bars 1. Increase padding on bars and gloves 2. Avoid prolonged pressure, change hand po 3. Raise stem height 4. Move saddle back if too far forward 5. If saddle is tilted down, position it level 1. Ride more upright, shorten reach 2. Raise stem height 3. Shorten stem length
Tibialis anterior tendonopathy Achilles tendonopathy
Morton’s neuroma/foot pain/numbness
Perineal numbness
Saddle height too high Saddle height too high (excessive stretch)
Lower saddle height Lower saddle height
Saddle height too low (with concomitant dropping of heel to generate more power) Cleat position Irregular sole Shoes too tight Saddle too high Tilt angle excessively up or down
Raise saddle height Usually, move cleat back, but may be forw Check sole for inner wear or cleat bolts p Wider shoes, loosen Velcro straps/shoe bu Lower saddle height Adjust angle closer to level with the grou
by changing cleat position and limiting float. Lateral knee Perineal neuropathy is seen with saddles set pain and iliotibial band symptoms may be seen with toes tilted excessively downward or upward, or too Reading a Preview pointing in and/or excessive float in the pedals.You're Approprisupport the ischial tuberosities. Saddle height and ti ate cleat and pedal modifications can eliminate lateral pain reduced (Table 2). Unlock full access with aThe free sooner trial. (Table 3). the overuse ailment is addresse evaluation and modification of training and bike fit, t chance of rapid recovery. Download With Free Trial TABLE 3. Bicycle Adjustment Based on the Location of Knee Pain Location
Anterior
Medial
Causes
Bicycle Adjustment
Seat too low Seat too far forward Climbing too much Big gears, low rpm
Raise seat Move seat back Reduce climbing Spin more
Cranks too long Cleats: toes point out
Shorten cranks Modify cleat position: toe in Consider floating pedals Limit float to 5 °
Floating pedals
CONCLUSIONS
Proper bike fit is essential for peak performan fort, safety, and injury prevention. There is no guidelines or geometric measurements scientifically to fit an athlete properly. Each athlete must be vidually. Changes should be made during the off-se Sign up to vote on this title change at a time, in small increments. The goal is to b useful Useful Not of the issues at hand: injury prevention, aerodynam fort, and performance. The use of video analy junction with objective physiological measuremen
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Sheet Music injuries: prevention and management. Philadelphia, PA: Saunders; 1994: 187–206. 7. Hughes J. Dr. Andy Pruitt on Bike Fit . Available at: http://www. ultracycling.com/equipment/bikefit.html. Reprinted from Ultra Cycling, About Ultracycling Magazine . 8. Armstrong L, Carmichael C. The Lance Armstrong Performance Program . Emmaus: Rodale Press; 2000:35–36. 9. Gregor RJ, Conconi F, Broker JP. Biomechanics of road cycling. In Gregor RJ, Conconi F, eds. Road Cycling . Oxford, United Kingdom: Blackwell Sciences Ltd; 2000:18–39.
10. Drake S. Dynamic Bike Fit With the CompuTrainer’s Spin Scan Guesswork out of Positioning . Available at: http://www com/html/coaching_corner/dynbikefit-example.htm. 11. Faria IE, Cavanagh PR. The Physiology and Biomechanics o New York: Wiley; 1978. 12. Broker JP, Gregor RJ. Cycling biomechanics. In Burke ER, ed. Cycling . Champaign, IL: Human Kinetics; 1996:145–146. 13. Broker JP. Cycling biomechanics: road and mountain. In Burk High Tech Cycling . Champaign, IL: Human Kinetics; 2003. 14. Baker A. Bicycling Medicine. NewYork : Fireside, Simon and
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