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Effects of altering cycling technique on gluteus medius syndrome
Journal of Manipulative and Physiological Therapeutics Volume 22 • Number 2 • February 1999 0161-4754/99/$8.00 + 0 76/1/95616 © 1999 JMPT
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Effects of Altering Cycling Technique on Gluteus Medius Syndrome Bart N. Green, DC,a Claire D. Johnson, DC,b and Allan Maloney, DCc
ABSTRACT Objective: We discuss how altering the cycling technique of a cyclist receiving periodic chiropractic care helped in the management of gluteus medius syndrome. Clinical Features: A 24-year-old male amateur cyclist had numbness and tingling localized to a small region on the superior portion of the right buttock. The area involved demonstrated paresthesia to light touch sensory evaluation. The cyclist had received chiropractic adjustments 2 days before the onset of the symptoms. One week earlier, the patient began riding a new bicycle with different gearing than his previous one. Manual-resisted muscle testing created soreness in the lumbosacral area and buttocks. Trigger points were identified in the right gluteus medius. Standing lumbar spine flexion was 70 degrees, limited by tight hamstrings. Intervention and Outcome: Because the patient was already receiving periodic chiropractic care, no passive therapy was used. Patient education regarding the difference in gear selec-
INTRODUCTION Overuse hip injuries from cycling are rare and consequently not well documented in the literature.1 Solely changing postural or exercise habits as a relief for these disorders has received minimal attention. In a search of MEDLINE from 1966 to July 1997 no reported cases were found by using the search terms “bicycling injuries,” “myofascial pain syndromes,” or “gluteus medius muscle” that identified improper cycling technique as a cause of gluteus medius syndrome (GMS). In the same search no studies were identified stating that rectifying daily activities alone could provide relief for the disorder. Nor has management of GMS been published by a chiropractor in MEDLINE, when we used the same literature search parameters and included “chiropractic” as a search term. The Index to the Chiropractic Literature listed 3 case reports about nonathletes between 1983 and 1996 when the same search terms listed above were used.
a
Assistant Professor, Palmer Center for Chiropractic Research, Palmer College of Chiropractic West, San Jose, California. b Assistant Clinical Professor, Palmer Center for Chiropractic Research, Palmer College of Chiropractic West, San Jose, California. c Private practice, Morinville, Alberta, Canada. Submit reprint requests to: Dr Bart Green, Palmer College of Chiropractic West, 90 E Tasman Ave, San Jose, CA 94580. Paper submitted May 7, 1998. In revised form August 3, 1998. Supported in part by the Palmer College of Chiropractic West.
tion in bicycles of a higher quality was provided. He was instructed to train in lower gears than he had previously used and to maintain a cadence of 70 to 90 revolutions of the pedals per minute. After 2 days, the paresthesia on the right buttock resolved. The trigger points were only mildly tender with minimal residual soreness of the involved muscles. Conclusion: Management of gluteus medius syndrome by altering the cadence and gear development for a bicyclist is discussed. Either frank or cumulative injury to the gluteus medius muscle is the typical etiologic factor for this syndrome. Repetitive strain of the patient’s gluteus medius muscle as a result of poor cycling technique appeared to be the cause here. Knowledge of bicycle fitting, training techniques, and bicycle mechanics appeared necessary to resolve the problem. (J Manipulative Physiol Ther 1999;22:108-13) Key Indexing Terms: Gluteus Medius Muscle; Myofascial Pain Syndromes; Bicycling Injuries; Sports Injuries; Chiropractic
Pain and dysfunction arising from myofascial trigger points (TPs) in the gluteus medius muscle are also known as GMS.2 Pain originating from these TPs is usually present in the immediate vicinity of the muscle. Aside from pain, other symptoms of myofascial pain syndromes have been reported and are listed in Table 1. Travell and Simons3 have identified three distinct gluteus medius TPs residing in the posterior (TP1), middle (TP2), and anterior (TP3) portions of the muscle. TP1 refers pain primarily to the ipsilateral iliac crest, the sacroiliac joint, and the sacrum. TP2 refers pain to the ipsilateral posterolateral buttock and thigh. TP3 refers pain bilaterally over the sacrum and into the lower lumbar region (Fig 1). Events and activities likely to initiate TPs in the gluteus medius include sudden falls, sports injuries, aerobics, and weight-bearing on one limb for an extended period of time. Patients with GMS may complain of pain during walking or standing on one leg.3 TPs are activated by acute overload, overwork fatigue, direct trauma, and chilling. Discomfort arising from active TPs may vary from hour to hour and day to day, and TPs may exist in a latent, or asymptomatic, state. TP activity may long outlast the precipitating event and also cause stiffness and weakness of the involved muscle.4 The terms gear development (GD) and cadence as they apply to cycling are described as follows. Gearing on a road bicycle is controlled by shifting the chain between the crank set and the rear cluster. The crank set is located in the center of the bike next to the right pedal arm, and the cluster is
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Fig 1. Pain patterns (dark shaded areas) referred from TPs (X) in right gluteus medius muscle (light shaded area). Essential pain pattern is solid shaded region and spillover pattern is stippled. The most medial TP1 refers pain primarily to crest of ilium, to region of sacroiliac joint, and to sacrum. The TP2 area is located more cephalad and laterally and refers pain caudally to buttock and to upper thigh posteriorly and laterally. The most anterior TP3 occurs less often and refers pain bilaterally over sacrum and into lowest lumbar region. (Reproduced with permission from Travell JG, Simons DG. Myofascial pain and dysfunction: the trigger point manual, the lower extremities. Baltimore: Williams & Wilkins; 1992. p. 151. Copyright 1992 Janet G. Travell, MD.) Table 1. Diagnostic criteria for trigger point identification Five common signs 1. Localized tenderness* 2. Referred pain produced by digital palpation of TP* 3. Presence of a taut, palpable band in muscle* 4. Limited stretch range of muscle* 5. Twitch response* Other signs 6. Increase in pain with passive or active stretching of affected muscle† 7. Increased pain when affected muscle is strongly contracted against fixed resistance† 8. Deep tenderness and dysesthesia referred by active TPs to referral zone† 9. Tenseness of muscle in immediate vicinity of a TP† 10. Jump sign on digital palpation of TP† 11. Dermatographism or panniculitis of skin overlying an active TP† *Clinical signs 1 through 5 are from Simons DG. Muscular pain syndromes. In: Fricton JR, Awad E, editors. Advances in pain research and therapy. Vol. 17. New York: Raven Press, 1990. p. 1-41. †Clinical signs 6 through 11 are from Travell JG, Simons DG. Myofascial pain and dysfunction: the trigger point manual. Baltimore: Williams & Wilkins, 1983. p. 12-17.
located in the back of the bike on the right side of the rear wheel (Fig 2). Crank sets on road bikes are usually made up of 2 sprockets called chain rings, one being larger in diameter and having more teeth than the other. Modern clusters may consist of 6 to 8 sprockets that also gradually get larger in size (Fig 3). The number of speeds is determined by mul-
tiplying the number of chain rings (middle of the bike) by the number of sprockets in the cluster (rear of the bike). A bicycle with a double chain ring on the crank set and 6 sprockets on the cluster is a 12-speed bicycle. Notation of sprocket size is made by listing the number of teeth on the smallest sprocket and the largest sprocket, respectively. For example, the 2 sprockets in a crank set could be listed as 38-52. How far the bicycle will travel with one turn of the pedals is determined by the GD. Measured in meters, GD is determined largely by which sprocket the chain is located on the crank set and cluster simultaneously5 and is represented mathematically by the formula: GD = Wheel diameter × π × (No. teeth in chain ring/No. teeth in sprocket). The highest gear, which generates the most distance and requires the most effort to peddle, would be selected by shifting the chain to the large chain ring of the crank set and the smallest ring on the cluster. Therefore the higher the GD the cyclist can manage, the further he or she can travel. The tradeoff exists in the higher amount of force that is placed on biomechanical tissues during use of a high GD. Cadence is the speed at which the pedals are turned and is reported in revolutions per minute. On flat terrain, competitive cyclists try to maintain a cadence of 80 to 110 rpm.6,7 Cadence is usually lowered during the climbing of a hill to approximately 70 rpm because of the effects of gravity. When measuring optimum efficiency of a small sample of cyclists (n = 5), Coast et al8 found an average cadence to be 60 to 80
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Fig 2. Road bicycle drive train. Front part of bicycle is at right side of figure. Crank set, composed of two chain rings, is located in center of bike and attached to right pedal arm. The cluster, consisting of several toothed sprockets, is located in back of bike on right side of rear wheel.
rpm. Cyclists have been observed to favor a cadence of 60 to 80 rpm in 1 study8 and 72 to 102 rpm in another.6 A high cadence diminishes the time that any one biomechanical structure will be used during a pedal revolution. Consequently, a low cadence paired with a high GD would place maximal stress on body tissues over a longer duration.
Case Report A 24-year-old male amateur cyclist had numbness and tingling of 2 days duration over a portion of his right buttock. He described this as a numb, tickling sensation when touched lightly, especially when clothing brushed against the area. The patient pointed to an area on the right buttock approximately 1 in inferior to the iliac crest and in the midline of the buttock. The sensation had been present continuously for 2 days. The patient found the situation more of an annoyance than a serious problem and could do nothing to relieve the symptoms. The cyclist had been receiving bimonthly chiropractic treatment from his chiropractor for 2 years. Four days before seeking care for the current chief complaint, he had received a chiropractic treatment consisting of full-spine short-lever arm manipulative procedures. The patient had never reported any adverse reactions to prior chiropractic treatments. The patient rode a bicycle approximately 75 miles/wk, alternating difficult rides with easier ones. He reported that he had started training on a new bicycle 1 week before the onset of the chief complaint, and he thought that the bike was appropriately fit to his body and riding style. Compared with training on his old bicycle, the patient felt more fatigued after riding the new one and his low back, thighs, and buttocks felt more exerted than before. The patient did not know whether the two bicycles had different gear arrangements but reported that he was riding in the same gears that he had on his old bike. The patient denied changing any other riding equipment or clothing in the past week.
Fig 3. Close-up of drive train, viewed from above rear of bike, showing graduating gear sizes between crank set in front and cluster in rear.
He was a 150-lb, 70-in tall white man of slight build. Range of motion of the lumbar spine was 70 degrees of flexion with tight hamstrings. All other active range of motion was normal in his lumbar spine and hips. Manual-resisted muscle testing, as described by Kendall and McCreary,9 of the gluteus medius, gluteus maximus, and piriformis muscles created soreness in the lumbosacral area and in his buttocks. Gluteus medius TP1 and TP3 were identified with palpation and included a jump sign. The gluteus maximus and piriformis were only tender to deep palpation. Testing the area for light touch sensation with a cotton wisp reproduced the chief complaint. A well-circumscribed area of approximately 3 in diameter located on the superior aspect of the right buttock (Fig 4) demonstrated paresthesia to light touch only. Criteria 1, 3, 4, 7, 8, 9, and 10 from Table 1 for gluteus medius TP1 and TP3 were therefore present. The remainder of the findings of neurologic evaluation and physical examination was unremarkable. Examination of his bicycles revealed that the GDs were significantly different. The old bicycle had 10 speeds (16-25 tooth rear cluster and a 38-52 tooth crankset), whereas the new bicycle had 12 speeds (11-21 tooth rear cluster and a 42-52 tooth crankset). The new bicycle appeared to have been fit appropriately to the rider, and he demonstrated acceptable cycling gait while on the bike5 while maintaining a cadence of approximately 60 pedal strokes per minute. Education regarding the differences in gearing between various levels of competitive bicycles was offered to him. We recommended that he either purchase a new cluster with lower gearing or ride in lower gears than he did on his old bicycle.5 He was also instructed to keep his cadence between 70 and 90 pedal strokes per minute when counting one leg’s down stroke.7,8 No treatment intervention was applied to him at that time. Two days later, he reported complete resolution of the chief complaint. He had changed from riding mostly in eighth gear, on his old bike, to third gear on the new bike at 70 to 90 rpm. He reported feeling less sore and fatigued after riding. Re-examination revealed normal perception of light touch over the area of complaint. The hamstrings remained
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Table 2. Differences in gear development (meters)* between bicycles Gear 1 2 3 4 5 6 7 8 9 10 11 12
Old bike (10 speeds)
New bike (12 speeds)
GD increase (%)
3.21 3.49 3.83 4.46 5.02 4.4 4.78 5.24 6.11 6.87
4.23 4.67 5.22 5.92 6.83 8.07 5.24 5.79 6.47 7.33 8.46 9.99
31.78 33.8 36.3 32.7 36 83.4 9.62 10.5 5.9 6.7
*GD = Wheel diameter × 3.1416 × No. teeth in chain ring/No. teeth in sprocket. Numbers in bold italic indicate GD that cyclist found comfortable on both bicycles.
Fig 4. Area of patient’s paresthesia was located on superior portion of right buttock at approximately midpoint of posterior aspect of iliac crest.
tight, and the lumbar spine active range of motion for flexion was 70 degrees. Manual-resisted muscle testing of the gluteus medius, gluteus maximus, and piriformis elicited only mild soreness. The TPs previously found in the gluteus medius exhibited only localized tenderness. The gluteus maximus and piriformis were less tender to palpation, although some mild tenderness was still elicited. The patient was followed up for 1 year and the paresthesia never recurred.
DISCUSSION In 1938, Kellgren published what may be the first case report of GMS.10 Before this, early research on pain arising from myofascial components was sporadic. During the late 1930s through early 1950s, the field of myofascial pain syndromes research began to develop as various authors began to report findings of referred pain of muscular origin,11 define diagnostic criteria for referred muscular pain,12 and identify common reproducible referral patterns.13 Since 1985, research in the field of myofascial pain has developed substantially.14 Travell and Simons define a myofascial TP as “a hyperirritable locus within a taut band of skeletal muscle, located in the muscular tissue and/or its associated fascia.”4 Most practitioners are familiar with the 5 common diagnostic criteria15 of a TP listed in Table 1. However, there are several other reported findings4 that are indicative of TPs that are also listed in Table 1. Accurate location of a TP may be difficult in some muscles, particularly when they are covered by other muscles or fascia. However, palpable distinction of the gluteus medius appears to be more attainable because two thirds of the muscle is superficial.16 The interrater reliability of detecting TPs in the gluteus medius by palpation has demonstrated good reliability.16 When combining palpation with the presence of
localized tenderness, eliciting a jump sign, or the patient recognizing their chief complaint, kappa values were found to be 0.58, 0.71, and 0.58, respectively.16 Properly fitting the bicycle to the rider is an important aspect of injury prevention in cyclists because many joints, muscles, and other body parts must be used during cycling. These structures are used thousands of times in a repetitive manner during one cycling training period.17 Most often, bike fitting focuses on the measuring of the athlete to the machine, including frame size, foot position, stem length, and other factors.1 However, examination of the athlete’s gearing and cadence should not be overlooked. Average clusters for amateurs range from 16 teeth on the smallest ring to 26 on the largest, noted as 16-26. Bicycles intended for a very strong, experienced rider may have an 11-21 cluster, which requires more force to turn the gears. Table 2 illustrates that the cyclist in this report had dramatically increased his GD, and consequently the power to move the bike this extra distance, sometimes as much as 83.4%. High GD demands more strength from the athlete and increases the force placed on the knee and other working joints.18 Higher gears are generally used with a slower cadence. This combination of higher force and longer reaction time has a greater propensity to fatigue and cause overuse injuries to the cyclist.1,19,20 Because of this, it has been suggested that the use of high GD should be avoided for prolonged periods of time.17 The combination of using lower GD with a higher cadence is preferable to decrease the amount of force sustained by the joints involved and to decrease the likelihood of an overuse injury.1,21 Our patient’s history and examination findings correlated strongly with the diagnosis of GMS. Many lower body overuse injuries from cycling have been reported in the literature,1,19,22 but GMS, or any of its synonyms, is not one of them. We deduced that this athlete was unknowingly “overtraining” with his new equipment, thus causing GMS. This correlates with Travell and Simons’ assertion that TPs are ac-
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Table 3. Commonly used treatment procedures for TPs Joint manipulation23,24 Intermittent cold with stretch3,24,25 Deep massage3,25 Ischemic compression3,24 Postisometric relaxation technique25 Injection with anesthetic or steroid4,26 Injection and stretch3,27 Dry needling25 Limitation of activities3,25 Moist hot packs24,25 Ultrasonography25 Acupuncture26 Vapocoolant spray with acupressure26 Home stretching3,24
tivated by acute overload and overwork fatigue.3 Incidentally, we found it interesting that the cyclist was riding in eighth gear (GD = 5.24 m) on his old bike, and he instinctively found third gear (GD = 5.22 m) on his new bike to be a comfortable regular gear at 70 to 90 rpm once he was instructed on basic differences in GD. TPs are typically treated with a variety of procedures (Table 3). Because the patient in this report was already receiving chiropractic care on a periodic basis, we believed that increasing the treatment frequency or introducing other treatment methods would probably be ineffective. We believed that the problem would be best solved by showing the patient how to remove the cause of the repetitive injury and to train in a manner that would slowly build his fitness up to the level required by his new technology. We also entertained the thought that restricting the cyclist from riding may have led to the same relief. However, given that he was committed to maintaining his current level of training on this new bicycle and would not be compliant with activity restrictions, the possibility of spontaneous resolution seemed less likely. The question could be raised that the patient may not have been compliant at all with the recommendations and was simply reporting relief of symptoms for spurious reasons. Because he was not observed during his training rides to see whether he followed the suggestions provided by us, there is no definitive way to answer this question. He did, however, report finding a new comfortable gear, as previously described, and claimed to use the new riding techniques. When combining these two factors with the apparent resolution of the chief complaint, it is probable that he performed the procedures. Whether the observed changes arose as a sequence of the natural history of the disorder is also in question. Muscle pain can be self-resolving over a 2-day period, and that was the amount of time between the patient’s office visits. However, myofascial pain usually does not resolve spontaneously when the muscles continue to be exposed to fatiguing activity. The cyclist in this report did not discontinue activity, but allegedly modified it, yet the problem appeared to resolve. It would be improbable, given this scenario, that the GMS would be self-resolving. Regardless, given the
inherent restrictions and lack of control characteristic of a retrospective case report, the natural history question remains unanswered. Several differential diagnoses must be considered while managing this case. It is possible that the patient had an adverse reaction to the previous treatment. However, it would be expected that a detrimental manipulation would be more joint specific in nature, rather than involving the muscles of the entire gluteal region. Also, it would be likely that an adverse reaction to manipulation would demonstrate symptoms closer to the time of the treatment. This patient had no abnormal joint findings on examination and only contraction, stretching, or palpation of muscular tissue provoked the condition. Furthermore, the resolution of the complaint after cycling instruction also appears to diminish the likelihood of iatrogenesis being the causative factor, although it is impossible to draw a conclusion either way. The gluteus medius seldom causes pain as a single muscle syndrome and is usually involved with other muscles as part of a functional unit; gluteus maximus and minimus, quadratus lumborum, and piriformis TPs commonly develop when there are TPs in the gluteus medius.3 Also confounding the diagnosis is the fact that gluteus maximus and minimus3 and the quadratus lumborum23 TP referral patterns overlap with those of the gluteus medius. Sacroiliac joint dysfunction and referred pain from the posterior joints of the lumbar spine may also present similarly to GMS.2 Other less common diagnoses considered were iliac crest pain syndrome28,29 and Maigne’s syndrome.2 Although procedures were performed to exclude these possible differential diagnoses, clinically it is difficult to definitively eliminate all possibilities because most provocative tests activate several of the above tissues simultaneously. We believed that, among other inordinate negative findings, the absence of tenderness in the quadratus lumborum, mobility in the sacroiliac joints, the lack of pain with provocative loading and compressing of the thoracic and lumbar spine, and the absence of a definitive and characteristic localized area of pain on the iliac crest substantially reduced the likelihood of quadratus lumborum TPs, sacroiliac dysfunction, lumbar facet referral, Maigne’s syndrome, and iliac crest pain syndrome, respectively.
CONCLUSION Reports of overuse syndromes in the hip and buttock are rare among cyclists. This case illustrates that taking more time to elicit pertinent historical data and having a working knowledge of patient activities, including sports equipment, may play a decisive role in alleviating pain of myofascial origin. We believe that altering cycling technique had a significant role in alleviating the GMS experienced by our patient. A retrospective report such as this often serves to provoke more questions than its design can answer. More controlled investigations, such as time series designs or clinical trials, may be warranted to better understand the amount of patient activity modification and in-office care that is necessary to help patients with myofascial pain syndromes.
Journal of Manipulative and Physiological Therapeutics Volume 22 • Number 2 • February 1999 Gluteus Medius Syndrome • Green et al
ACKNOWLEDGMENTS We thank Todd Andrew and Joey Alcantara for their assistance in the preparation of this manuscript.
REFERENCES 1. Gregor RJ, Wheeler JB. Biomechanical factors associated with shoe/pedal interfaces. Sports Med 1994;17:117-31. 2. Kirkaldy-Willis WH. Managing low back pain. New York: Churchill Livingstone; 1988. p. 133-54. 3. Travell JG, Simons DG. Myofascial pain and dysfunction: the trigger point manual, the lower extremities. Baltimore: Williams & Wilkins; 1992. p. 150-67. 4. Travell JG, Simons DG. Myofascial pain and dysfunction: the trigger point manual. Baltimore: Williams & Wilkins; 1983. p. 12-7. 5. Jones C. Basic equipment. In: Sport level coaching manual. Colorado Springs (CO): USA Cycling, Inc; 1995. p. 133-9. 6. Hagberg JM, Mollin JP, Giese MD, Spitznagel E. Effect of pedaling rate on submaximal exercise responses of competitive cyclists. J Appl Physiol 1981;51:447-51. 7. Gregor RJ, Rugg SG. Effects of saddle height and pedaling cadence on power output and efficiency. In: Burke ER, editor. Science of cycling. Champaign (IL): Human Kinetics; 1986. p. 69-90. 8. Coast JR, Cox RH, Welch HG. Optimal pedaling rate in prolonged bouts of cycle ergometry. Med Sci Sports Exerc 1986;18:225-30. 9. Kendall FP, McCreary EK. Muscles: testing and function. Baltimore: Williams & Wilkins; 1983. p. 169-75. 10. Kellgren JH. A preliminary account of referred pains arising from the muscle. BMJ 1938;1:325-7. 11. Kelly M. Lumbago and abdominal pain. Med J Aust 1942;1:311-7. 12. Winter Z. Referred pain in fibrositis. Med Rec 1944;157:34-7. 13. Travell J, Rinzler SH. The myofascial genesis of pain. Postgrad Med 1952;11:425-34. 14. Schneider MJ. Tender points/fibromyalgia vs trigger points/ myofascial pain syndrome: a need for clarity in terminology and differential diagnosis. J Manipulative Physiol Ther 1995;18:398-406.
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15. Simons DG. Muscular pain syndromes. In: Fricton JR, Awad E, editors. Advances in pain research and therapy. New York: Raven Press; 1990. p. 17:1-41. 16. Njoo KH, Van der Does E. The occurrence of inter-rater reliability of myofascial trigger points in the quadratus lumborum and gluteus medius: a prospective study in non-specific low back pain patients and controls in general practice. Pain 1994;58:317-23. 17. Nichols CE. Injuries in cycling. In: Renstrom PAFH, editor. Clinical practice of sports injury prevention and care. Oxford (UK): Blackwell Scientific Publications; 1994. p. 514. 18. Ericson MB, Nisell R. Tibiofemoral joint forces during ergometer cycling. Am J Sports Med 1986;14:285-90. 19. Holmes JC, Pruitt AL, Whalen NJ. Lower extremity overuse in bicycling. Clin Sports Med 1994;13:187-205. 20. Ruby P, Hull ML. Response of intersegmental knee loads to foot/pedal platform degrees of freedom in cycling. J Biomech 1993;26:1327-40. 21. Davis RR, Hull ML. Measurements of pedal loading in bicycling. II. Analysis and results. J Biomech 1981;14:857-72. 22. Mellion MB. Neck and back pain in cycling. Clin Sports Med 1994;13:137-64. 23. De Franca GG, Levine LJ. The quadratus lumborum and low back pain. J Manipulative Physiol Ther 1991;14:142-9. 24. Sandman KB. Myofascial pain syndromes: their mechanism, diagnosis and treatment. J Manipulative Physiol Ther 1981;4:135-40. 25. Simons DG, Travell JG. Myofascial pain syndromes. In: Wall PD, Melzack R, editors. Textbook of pain. London: Churchill Livingstone; 1989. p. 379-80. 26. Garvey TA, Marks MR, Wiesel SW. A prospective, randomized, double-blind evaluation of trigger-point injection therapy for low-back pain. Spine 1989;14:962-4. 27. Travell J. Basis for the multiple uses of local block of somatic trigger areas (procaine infiltration and ethyl chloride spray). Miss Valley Med J 1949;71:13-22. 28. Fairbank JCT, O’Brien JP. The iliac crest pain syndrome: a treatable cause of low-back pain. Spine 1983;8:220-4. 29. Collee G, Dijkmans BAC, Vandenbroucke JP, Cats A. Iliac crest pain syndrome in low back pain: frequency and features. J Rheumatol 1991;18:1064-7.
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Effects of Altering Cycling Technique on Gluteus Medius Syndrome Bart N. Green, DC,a Claire D. Johnson, DC,b and Allan Maloney, DCc
ABSTRACT Objective: We discuss how altering the cycling technique of a cyclist receiving periodic chiropractic care helped in the management of gluteus medius syndrome. Clinical Features: A 24-year-old male amateur cyclist had numbness and tingling localized to a small region on the superior portion of the right buttock. The area involved demonstrated paresthesia to light touch sensory evaluation. The cyclist had received chiropractic adjustments 2 days before the onset of the symptoms. One week earlier, the patient began riding a new bicycle with different gearing than his previous one. Manual-resisted muscle testing created soreness in the lumbosacral area and buttocks. Trigger points were identified in the right gluteus medius. Standing lumbar spine flexion was 70 degrees, limited by tight hamstrings. Intervention and Outcome: Because the patient was already receiving periodic chiropractic care, no passive therapy was used. Patient education regarding the difference in gear selec-
INTRODUCTION Overuse hip injuries from cycling are rare and consequently not well documented in the literature.1 Solely changing postural or exercise habits as a relief for these disorders has received minimal attention. In a search of MEDLINE from 1966 to July 1997 no reported cases were found by using the search terms “bicycling injuries,” “myofascial pain syndromes,” or “gluteus medius muscle” that identified improper cycling technique as a cause of gluteus medius syndrome (GMS). In the same search no studies were identified stating that rectifying daily activities alone could provide relief for the disorder. Nor has management of GMS been published by a chiropractor in MEDLINE, when we used the same literature search parameters and included “chiropractic” as a search term. The Index to the Chiropractic Literature listed 3 case reports about nonathletes between 1983 and 1996 when the same search terms listed above were used.
a
Assistant Professor, Palmer Center for Chiropractic Research, Palmer College of Chiropractic West, San Jose, California. b Assistant Clinical Professor, Palmer Center for Chiropractic Research, Palmer College of Chiropractic West, San Jose, California. c Private practice, Morinville, Alberta, Canada. Submit reprint requests to: Dr Bart Green, Palmer College of Chiropractic West, 90 E Tasman Ave, San Jose, CA 94580. Paper submitted May 7, 1998. In revised form August 3, 1998. Supported in part by the Palmer College of Chiropractic West.
tion in bicycles of a higher quality was provided. He was instructed to train in lower gears than he had previously used and to maintain a cadence of 70 to 90 revolutions of the pedals per minute. After 2 days, the paresthesia on the right buttock resolved. The trigger points were only mildly tender with minimal residual soreness of the involved muscles. Conclusion: Management of gluteus medius syndrome by altering the cadence and gear development for a bicyclist is discussed. Either frank or cumulative injury to the gluteus medius muscle is the typical etiologic factor for this syndrome. Repetitive strain of the patient’s gluteus medius muscle as a result of poor cycling technique appeared to be the cause here. Knowledge of bicycle fitting, training techniques, and bicycle mechanics appeared necessary to resolve the problem. (J Manipulative Physiol Ther 1999;22:108-13) Key Indexing Terms: Gluteus Medius Muscle; Myofascial Pain Syndromes; Bicycling Injuries; Sports Injuries; Chiropractic
Pain and dysfunction arising from myofascial trigger points (TPs) in the gluteus medius muscle are also known as GMS.2 Pain originating from these TPs is usually present in the immediate vicinity of the muscle. Aside from pain, other symptoms of myofascial pain syndromes have been reported and are listed in Table 1. Travell and Simons3 have identified three distinct gluteus medius TPs residing in the posterior (TP1), middle (TP2), and anterior (TP3) portions of the muscle. TP1 refers pain primarily to the ipsilateral iliac crest, the sacroiliac joint, and the sacrum. TP2 refers pain to the ipsilateral posterolateral buttock and thigh. TP3 refers pain bilaterally over the sacrum and into the lower lumbar region (Fig 1). Events and activities likely to initiate TPs in the gluteus medius include sudden falls, sports injuries, aerobics, and weight-bearing on one limb for an extended period of time. Patients with GMS may complain of pain during walking or standing on one leg.3 TPs are activated by acute overload, overwork fatigue, direct trauma, and chilling. Discomfort arising from active TPs may vary from hour to hour and day to day, and TPs may exist in a latent, or asymptomatic, state. TP activity may long outlast the precipitating event and also cause stiffness and weakness of the involved muscle.4 The terms gear development (GD) and cadence as they apply to cycling are described as follows. Gearing on a road bicycle is controlled by shifting the chain between the crank set and the rear cluster. The crank set is located in the center of the bike next to the right pedal arm, and the cluster is
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Fig 1. Pain patterns (dark shaded areas) referred from TPs (X) in right gluteus medius muscle (light shaded area). Essential pain pattern is solid shaded region and spillover pattern is stippled. The most medial TP1 refers pain primarily to crest of ilium, to region of sacroiliac joint, and to sacrum. The TP2 area is located more cephalad and laterally and refers pain caudally to buttock and to upper thigh posteriorly and laterally. The most anterior TP3 occurs less often and refers pain bilaterally over sacrum and into lowest lumbar region. (Reproduced with permission from Travell JG, Simons DG. Myofascial pain and dysfunction: the trigger point manual, the lower extremities. Baltimore: Williams & Wilkins; 1992. p. 151. Copyright 1992 Janet G. Travell, MD.) Table 1. Diagnostic criteria for trigger point identification Five common signs 1. Localized tenderness* 2. Referred pain produced by digital palpation of TP* 3. Presence of a taut, palpable band in muscle* 4. Limited stretch range of muscle* 5. Twitch response* Other signs 6. Increase in pain with passive or active stretching of affected muscle† 7. Increased pain when affected muscle is strongly contracted against fixed resistance† 8. Deep tenderness and dysesthesia referred by active TPs to referral zone† 9. Tenseness of muscle in immediate vicinity of a TP† 10. Jump sign on digital palpation of TP† 11. Dermatographism or panniculitis of skin overlying an active TP† *Clinical signs 1 through 5 are from Simons DG. Muscular pain syndromes. In: Fricton JR, Awad E, editors. Advances in pain research and therapy. Vol. 17. New York: Raven Press, 1990. p. 1-41. †Clinical signs 6 through 11 are from Travell JG, Simons DG. Myofascial pain and dysfunction: the trigger point manual. Baltimore: Williams & Wilkins, 1983. p. 12-17.
located in the back of the bike on the right side of the rear wheel (Fig 2). Crank sets on road bikes are usually made up of 2 sprockets called chain rings, one being larger in diameter and having more teeth than the other. Modern clusters may consist of 6 to 8 sprockets that also gradually get larger in size (Fig 3). The number of speeds is determined by mul-
tiplying the number of chain rings (middle of the bike) by the number of sprockets in the cluster (rear of the bike). A bicycle with a double chain ring on the crank set and 6 sprockets on the cluster is a 12-speed bicycle. Notation of sprocket size is made by listing the number of teeth on the smallest sprocket and the largest sprocket, respectively. For example, the 2 sprockets in a crank set could be listed as 38-52. How far the bicycle will travel with one turn of the pedals is determined by the GD. Measured in meters, GD is determined largely by which sprocket the chain is located on the crank set and cluster simultaneously5 and is represented mathematically by the formula: GD = Wheel diameter × π × (No. teeth in chain ring/No. teeth in sprocket). The highest gear, which generates the most distance and requires the most effort to peddle, would be selected by shifting the chain to the large chain ring of the crank set and the smallest ring on the cluster. Therefore the higher the GD the cyclist can manage, the further he or she can travel. The tradeoff exists in the higher amount of force that is placed on biomechanical tissues during use of a high GD. Cadence is the speed at which the pedals are turned and is reported in revolutions per minute. On flat terrain, competitive cyclists try to maintain a cadence of 80 to 110 rpm.6,7 Cadence is usually lowered during the climbing of a hill to approximately 70 rpm because of the effects of gravity. When measuring optimum efficiency of a small sample of cyclists (n = 5), Coast et al8 found an average cadence to be 60 to 80
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Fig 2. Road bicycle drive train. Front part of bicycle is at right side of figure. Crank set, composed of two chain rings, is located in center of bike and attached to right pedal arm. The cluster, consisting of several toothed sprockets, is located in back of bike on right side of rear wheel.
rpm. Cyclists have been observed to favor a cadence of 60 to 80 rpm in 1 study8 and 72 to 102 rpm in another.6 A high cadence diminishes the time that any one biomechanical structure will be used during a pedal revolution. Consequently, a low cadence paired with a high GD would place maximal stress on body tissues over a longer duration.
Case Report A 24-year-old male amateur cyclist had numbness and tingling of 2 days duration over a portion of his right buttock. He described this as a numb, tickling sensation when touched lightly, especially when clothing brushed against the area. The patient pointed to an area on the right buttock approximately 1 in inferior to the iliac crest and in the midline of the buttock. The sensation had been present continuously for 2 days. The patient found the situation more of an annoyance than a serious problem and could do nothing to relieve the symptoms. The cyclist had been receiving bimonthly chiropractic treatment from his chiropractor for 2 years. Four days before seeking care for the current chief complaint, he had received a chiropractic treatment consisting of full-spine short-lever arm manipulative procedures. The patient had never reported any adverse reactions to prior chiropractic treatments. The patient rode a bicycle approximately 75 miles/wk, alternating difficult rides with easier ones. He reported that he had started training on a new bicycle 1 week before the onset of the chief complaint, and he thought that the bike was appropriately fit to his body and riding style. Compared with training on his old bicycle, the patient felt more fatigued after riding the new one and his low back, thighs, and buttocks felt more exerted than before. The patient did not know whether the two bicycles had different gear arrangements but reported that he was riding in the same gears that he had on his old bike. The patient denied changing any other riding equipment or clothing in the past week.
Fig 3. Close-up of drive train, viewed from above rear of bike, showing graduating gear sizes between crank set in front and cluster in rear.
He was a 150-lb, 70-in tall white man of slight build. Range of motion of the lumbar spine was 70 degrees of flexion with tight hamstrings. All other active range of motion was normal in his lumbar spine and hips. Manual-resisted muscle testing, as described by Kendall and McCreary,9 of the gluteus medius, gluteus maximus, and piriformis muscles created soreness in the lumbosacral area and in his buttocks. Gluteus medius TP1 and TP3 were identified with palpation and included a jump sign. The gluteus maximus and piriformis were only tender to deep palpation. Testing the area for light touch sensation with a cotton wisp reproduced the chief complaint. A well-circumscribed area of approximately 3 in diameter located on the superior aspect of the right buttock (Fig 4) demonstrated paresthesia to light touch only. Criteria 1, 3, 4, 7, 8, 9, and 10 from Table 1 for gluteus medius TP1 and TP3 were therefore present. The remainder of the findings of neurologic evaluation and physical examination was unremarkable. Examination of his bicycles revealed that the GDs were significantly different. The old bicycle had 10 speeds (16-25 tooth rear cluster and a 38-52 tooth crankset), whereas the new bicycle had 12 speeds (11-21 tooth rear cluster and a 42-52 tooth crankset). The new bicycle appeared to have been fit appropriately to the rider, and he demonstrated acceptable cycling gait while on the bike5 while maintaining a cadence of approximately 60 pedal strokes per minute. Education regarding the differences in gearing between various levels of competitive bicycles was offered to him. We recommended that he either purchase a new cluster with lower gearing or ride in lower gears than he did on his old bicycle.5 He was also instructed to keep his cadence between 70 and 90 pedal strokes per minute when counting one leg’s down stroke.7,8 No treatment intervention was applied to him at that time. Two days later, he reported complete resolution of the chief complaint. He had changed from riding mostly in eighth gear, on his old bike, to third gear on the new bike at 70 to 90 rpm. He reported feeling less sore and fatigued after riding. Re-examination revealed normal perception of light touch over the area of complaint. The hamstrings remained
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Table 2. Differences in gear development (meters)* between bicycles Gear 1 2 3 4 5 6 7 8 9 10 11 12
Old bike (10 speeds)
New bike (12 speeds)
GD increase (%)
3.21 3.49 3.83 4.46 5.02 4.4 4.78 5.24 6.11 6.87
4.23 4.67 5.22 5.92 6.83 8.07 5.24 5.79 6.47 7.33 8.46 9.99
31.78 33.8 36.3 32.7 36 83.4 9.62 10.5 5.9 6.7
*GD = Wheel diameter × 3.1416 × No. teeth in chain ring/No. teeth in sprocket. Numbers in bold italic indicate GD that cyclist found comfortable on both bicycles.
Fig 4. Area of patient’s paresthesia was located on superior portion of right buttock at approximately midpoint of posterior aspect of iliac crest.
tight, and the lumbar spine active range of motion for flexion was 70 degrees. Manual-resisted muscle testing of the gluteus medius, gluteus maximus, and piriformis elicited only mild soreness. The TPs previously found in the gluteus medius exhibited only localized tenderness. The gluteus maximus and piriformis were less tender to palpation, although some mild tenderness was still elicited. The patient was followed up for 1 year and the paresthesia never recurred.
DISCUSSION In 1938, Kellgren published what may be the first case report of GMS.10 Before this, early research on pain arising from myofascial components was sporadic. During the late 1930s through early 1950s, the field of myofascial pain syndromes research began to develop as various authors began to report findings of referred pain of muscular origin,11 define diagnostic criteria for referred muscular pain,12 and identify common reproducible referral patterns.13 Since 1985, research in the field of myofascial pain has developed substantially.14 Travell and Simons define a myofascial TP as “a hyperirritable locus within a taut band of skeletal muscle, located in the muscular tissue and/or its associated fascia.”4 Most practitioners are familiar with the 5 common diagnostic criteria15 of a TP listed in Table 1. However, there are several other reported findings4 that are indicative of TPs that are also listed in Table 1. Accurate location of a TP may be difficult in some muscles, particularly when they are covered by other muscles or fascia. However, palpable distinction of the gluteus medius appears to be more attainable because two thirds of the muscle is superficial.16 The interrater reliability of detecting TPs in the gluteus medius by palpation has demonstrated good reliability.16 When combining palpation with the presence of
localized tenderness, eliciting a jump sign, or the patient recognizing their chief complaint, kappa values were found to be 0.58, 0.71, and 0.58, respectively.16 Properly fitting the bicycle to the rider is an important aspect of injury prevention in cyclists because many joints, muscles, and other body parts must be used during cycling. These structures are used thousands of times in a repetitive manner during one cycling training period.17 Most often, bike fitting focuses on the measuring of the athlete to the machine, including frame size, foot position, stem length, and other factors.1 However, examination of the athlete’s gearing and cadence should not be overlooked. Average clusters for amateurs range from 16 teeth on the smallest ring to 26 on the largest, noted as 16-26. Bicycles intended for a very strong, experienced rider may have an 11-21 cluster, which requires more force to turn the gears. Table 2 illustrates that the cyclist in this report had dramatically increased his GD, and consequently the power to move the bike this extra distance, sometimes as much as 83.4%. High GD demands more strength from the athlete and increases the force placed on the knee and other working joints.18 Higher gears are generally used with a slower cadence. This combination of higher force and longer reaction time has a greater propensity to fatigue and cause overuse injuries to the cyclist.1,19,20 Because of this, it has been suggested that the use of high GD should be avoided for prolonged periods of time.17 The combination of using lower GD with a higher cadence is preferable to decrease the amount of force sustained by the joints involved and to decrease the likelihood of an overuse injury.1,21 Our patient’s history and examination findings correlated strongly with the diagnosis of GMS. Many lower body overuse injuries from cycling have been reported in the literature,1,19,22 but GMS, or any of its synonyms, is not one of them. We deduced that this athlete was unknowingly “overtraining” with his new equipment, thus causing GMS. This correlates with Travell and Simons’ assertion that TPs are ac-
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Table 3. Commonly used treatment procedures for TPs Joint manipulation23,24 Intermittent cold with stretch3,24,25 Deep massage3,25 Ischemic compression3,24 Postisometric relaxation technique25 Injection with anesthetic or steroid4,26 Injection and stretch3,27 Dry needling25 Limitation of activities3,25 Moist hot packs24,25 Ultrasonography25 Acupuncture26 Vapocoolant spray with acupressure26 Home stretching3,24
tivated by acute overload and overwork fatigue.3 Incidentally, we found it interesting that the cyclist was riding in eighth gear (GD = 5.24 m) on his old bike, and he instinctively found third gear (GD = 5.22 m) on his new bike to be a comfortable regular gear at 70 to 90 rpm once he was instructed on basic differences in GD. TPs are typically treated with a variety of procedures (Table 3). Because the patient in this report was already receiving chiropractic care on a periodic basis, we believed that increasing the treatment frequency or introducing other treatment methods would probably be ineffective. We believed that the problem would be best solved by showing the patient how to remove the cause of the repetitive injury and to train in a manner that would slowly build his fitness up to the level required by his new technology. We also entertained the thought that restricting the cyclist from riding may have led to the same relief. However, given that he was committed to maintaining his current level of training on this new bicycle and would not be compliant with activity restrictions, the possibility of spontaneous resolution seemed less likely. The question could be raised that the patient may not have been compliant at all with the recommendations and was simply reporting relief of symptoms for spurious reasons. Because he was not observed during his training rides to see whether he followed the suggestions provided by us, there is no definitive way to answer this question. He did, however, report finding a new comfortable gear, as previously described, and claimed to use the new riding techniques. When combining these two factors with the apparent resolution of the chief complaint, it is probable that he performed the procedures. Whether the observed changes arose as a sequence of the natural history of the disorder is also in question. Muscle pain can be self-resolving over a 2-day period, and that was the amount of time between the patient’s office visits. However, myofascial pain usually does not resolve spontaneously when the muscles continue to be exposed to fatiguing activity. The cyclist in this report did not discontinue activity, but allegedly modified it, yet the problem appeared to resolve. It would be improbable, given this scenario, that the GMS would be self-resolving. Regardless, given the
inherent restrictions and lack of control characteristic of a retrospective case report, the natural history question remains unanswered. Several differential diagnoses must be considered while managing this case. It is possible that the patient had an adverse reaction to the previous treatment. However, it would be expected that a detrimental manipulation would be more joint specific in nature, rather than involving the muscles of the entire gluteal region. Also, it would be likely that an adverse reaction to manipulation would demonstrate symptoms closer to the time of the treatment. This patient had no abnormal joint findings on examination and only contraction, stretching, or palpation of muscular tissue provoked the condition. Furthermore, the resolution of the complaint after cycling instruction also appears to diminish the likelihood of iatrogenesis being the causative factor, although it is impossible to draw a conclusion either way. The gluteus medius seldom causes pain as a single muscle syndrome and is usually involved with other muscles as part of a functional unit; gluteus maximus and minimus, quadratus lumborum, and piriformis TPs commonly develop when there are TPs in the gluteus medius.3 Also confounding the diagnosis is the fact that gluteus maximus and minimus3 and the quadratus lumborum23 TP referral patterns overlap with those of the gluteus medius. Sacroiliac joint dysfunction and referred pain from the posterior joints of the lumbar spine may also present similarly to GMS.2 Other less common diagnoses considered were iliac crest pain syndrome28,29 and Maigne’s syndrome.2 Although procedures were performed to exclude these possible differential diagnoses, clinically it is difficult to definitively eliminate all possibilities because most provocative tests activate several of the above tissues simultaneously. We believed that, among other inordinate negative findings, the absence of tenderness in the quadratus lumborum, mobility in the sacroiliac joints, the lack of pain with provocative loading and compressing of the thoracic and lumbar spine, and the absence of a definitive and characteristic localized area of pain on the iliac crest substantially reduced the likelihood of quadratus lumborum TPs, sacroiliac dysfunction, lumbar facet referral, Maigne’s syndrome, and iliac crest pain syndrome, respectively.
CONCLUSION Reports of overuse syndromes in the hip and buttock are rare among cyclists. This case illustrates that taking more time to elicit pertinent historical data and having a working knowledge of patient activities, including sports equipment, may play a decisive role in alleviating pain of myofascial origin. We believe that altering cycling technique had a significant role in alleviating the GMS experienced by our patient. A retrospective report such as this often serves to provoke more questions than its design can answer. More controlled investigations, such as time series designs or clinical trials, may be warranted to better understand the amount of patient activity modification and in-office care that is necessary to help patients with myofascial pain syndromes.
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ACKNOWLEDGMENTS We thank Todd Andrew and Joey Alcantara for their assistance in the preparation of this manuscript.
REFERENCES 1. Gregor RJ, Wheeler JB. Biomechanical factors associated with shoe/pedal interfaces. Sports Med 1994;17:117-31. 2. Kirkaldy-Willis WH. Managing low back pain. New York: Churchill Livingstone; 1988. p. 133-54. 3. Travell JG, Simons DG. Myofascial pain and dysfunction: the trigger point manual, the lower extremities. Baltimore: Williams & Wilkins; 1992. p. 150-67. 4. Travell JG, Simons DG. Myofascial pain and dysfunction: the trigger point manual. Baltimore: Williams & Wilkins; 1983. p. 12-7. 5. Jones C. Basic equipment. In: Sport level coaching manual. Colorado Springs (CO): USA Cycling, Inc; 1995. p. 133-9. 6. Hagberg JM, Mollin JP, Giese MD, Spitznagel E. Effect of pedaling rate on submaximal exercise responses of competitive cyclists. J Appl Physiol 1981;51:447-51. 7. Gregor RJ, Rugg SG. Effects of saddle height and pedaling cadence on power output and efficiency. In: Burke ER, editor. Science of cycling. Champaign (IL): Human Kinetics; 1986. p. 69-90. 8. Coast JR, Cox RH, Welch HG. Optimal pedaling rate in prolonged bouts of cycle ergometry. Med Sci Sports Exerc 1986;18:225-30. 9. Kendall FP, McCreary EK. Muscles: testing and function. Baltimore: Williams & Wilkins; 1983. p. 169-75. 10. Kellgren JH. A preliminary account of referred pains arising from the muscle. BMJ 1938;1:325-7. 11. Kelly M. Lumbago and abdominal pain. Med J Aust 1942;1:311-7. 12. Winter Z. Referred pain in fibrositis. Med Rec 1944;157:34-7. 13. Travell J, Rinzler SH. The myofascial genesis of pain. Postgrad Med 1952;11:425-34. 14. Schneider MJ. Tender points/fibromyalgia vs trigger points/ myofascial pain syndrome: a need for clarity in terminology and differential diagnosis. J Manipulative Physiol Ther 1995;18:398-406.
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15. Simons DG. Muscular pain syndromes. In: Fricton JR, Awad E, editors. Advances in pain research and therapy. New York: Raven Press; 1990. p. 17:1-41. 16. Njoo KH, Van der Does E. The occurrence of inter-rater reliability of myofascial trigger points in the quadratus lumborum and gluteus medius: a prospective study in non-specific low back pain patients and controls in general practice. Pain 1994;58:317-23. 17. Nichols CE. Injuries in cycling. In: Renstrom PAFH, editor. Clinical practice of sports injury prevention and care. Oxford (UK): Blackwell Scientific Publications; 1994. p. 514. 18. Ericson MB, Nisell R. Tibiofemoral joint forces during ergometer cycling. Am J Sports Med 1986;14:285-90. 19. Holmes JC, Pruitt AL, Whalen NJ. Lower extremity overuse in bicycling. Clin Sports Med 1994;13:187-205. 20. Ruby P, Hull ML. Response of intersegmental knee loads to foot/pedal platform degrees of freedom in cycling. J Biomech 1993;26:1327-40. 21. Davis RR, Hull ML. Measurements of pedal loading in bicycling. II. Analysis and results. J Biomech 1981;14:857-72. 22. Mellion MB. Neck and back pain in cycling. Clin Sports Med 1994;13:137-64. 23. De Franca GG, Levine LJ. The quadratus lumborum and low back pain. J Manipulative Physiol Ther 1991;14:142-9. 24. Sandman KB. Myofascial pain syndromes: their mechanism, diagnosis and treatment. J Manipulative Physiol Ther 1981;4:135-40. 25. Simons DG, Travell JG. Myofascial pain syndromes. In: Wall PD, Melzack R, editors. Textbook of pain. London: Churchill Livingstone; 1989. p. 379-80. 26. Garvey TA, Marks MR, Wiesel SW. A prospective, randomized, double-blind evaluation of trigger-point injection therapy for low-back pain. Spine 1989;14:962-4. 27. Travell J. Basis for the multiple uses of local block of somatic trigger areas (procaine infiltration and ethyl chloride spray). Miss Valley Med J 1949;71:13-22. 28. Fairbank JCT, O’Brien JP. The iliac crest pain syndrome: a treatable cause of low-back pain. Spine 1983;8:220-4. 29. Collee G, Dijkmans BAC, Vandenbroucke JP, Cats A. Iliac crest pain syndrome in low back pain: frequency and features. J Rheumatol 1991;18:1064-7.