Sage Journals: Discover world-class research

Abstract

Background and purpose:

This nationwide questionnaire survey was performed to clarify the prevalence of groin pain in unicycle athletes and to reveal the relationship between groin pain and factors such as age or athletic career.

Patients and methods:

To evaluate the prevalence of groin pain, the questionnaire was sent to 1304 unicyclists belonging to the Japan Unicycle Association. All subjects aged 6 years or older at the time they answered the questionnaire.

Results:

Overall, 17% of unicyclists complained of groin pain. Pain was more common in those aged 13–19 years and in those with a career lasting more than 6 years.

Conclusion:

The incidence of groin pain (17%) among unicyclists is higher than that among athletes participating in other sports. Unicyclists aged between 13 and 19 years old and those with an athletic career of more than 6 years often suffer from groin pain.

Keywords

adolescent groin pain nationwide questionnaire survey unicycle

Introduction

Unicycling was first introduced in Japan in 1910 by an American stunt performer. In 1978, the Japan Unicycle Club was established as a voluntary organization; it was later renamed as the Japan Unicycling Association. Unicycling has become popular among children in elementary schools as a kind of physical exercise; thus, the unicycling population in Japan exceeds 10,000. Ninety percent of elementary schools possess unicycles; moreover, unicycling improves both health and strength in juveniles. The sport is particularly effective at increasing trunk strength and stability.¹ However, it is necessary to pay attention to the sports injuries including groin pain particularly in juvenile athletes.

We experienced the case of a 16-year-old, female, high-level unicyclist with groin pain and severe radiographic changes with co-occurrence of femoroacetabular impingement (FAI) and osteoarthritis (OA), who underwent hip arthroscopic surgery. Osteochondroplasty and labrum repair led to a marked improvement of clinical symptoms; these were reflected by the postsurgical radiographic findings. Thus, hip arthroscopy possibly provides good clinical outcomes for cycling athlete with FAI.² There are similar reports of coxarthrosis caused by unicycling.^3,4 However, no epidemiological studies on the relationship between unicycling and groin pain are available in the literature. We assumed that a proportion of unicyclists, particularly those of preadolescent age, have groin pain. The primary goal of this nationwide questionnaire survey was to examine the prevalence of groin pain in unicycle athletes. The secondary aim was to identify the relationship between groin pain and factors such as age and the length of athletic career. Our hypothesis was that certain percentage of unicyclists complained groin pain, particularly in population with relatively longer athletic career.

Material and methods

This observational study was approved by the local institutional review board and ethical committee that assess medical and health research involving human subjects. The questionnaire survey was carried with complete cooperation from the Japan Unicycling Association. The questionnaire was sent to 1304 unicyclists at the Japan Unicycle Association from December 2017 to January 2018. The questionnaire requested information about sports history, practice time, symptoms other than groin pain, and groin pain (primary outcome). All subjects were aged 6 years or older at the time of filling the questionnaire. The questionnaire included 12 items and could be answered in approximately 10 min.

The 12 items in the questionnaire were as follows: ① sex and age, ② age at the time of starting unicycling and the length of athletic career, ③ type of athletic event, ④ sports experience besides unicycling, ⑤ practice time, ⑥ size of unicycle, ⑦ presence/absence of groin pain, ⑧ time when groin pain first appeared, ⑨ severity of groin pain, ⑩ site of symptoms, ⑪ cause of groin pain, and ⑫ symptoms in the absence of groin pain.

Cross-table analysis was conducted using the χ ² test. All tests were two-tailed, and p < 0.05 was considered statistically significant. All data were analyzed using the SPSS16.0 package program (IBM Corp., SPSS 16.0 Japanese) and were expressed as mean values.

Results

Questionnaires were returned by 1011 out of 1304 (78%) subjects. The answers are listed below:

① Sex: Female, 906 (89.6%); male, 99 (9.8%); nonrespondents, 6 (0.6%) (Figure 1 ①-A).

Figure 1.

Diagrammatic presentation of answers to each question.

Age: <10 years, 225 (22.3%); 10–19 years, 699 (69.1%); 20–29 years, 48 (4.7%); 30–39 years, 14 (1.4%); 40–49 years, 5 (0.5%); and >50 years, 19 (1.9%) (Figure 1 ①-B).

② Age at the time of starting unicycling: 6–9 years, 741 (73.3%); <6 years, 174 (17.2%); and 10–12 years, 62 (6.1%) (Figure 1 ②-A).

Length of athletic career: 1–2 years, 235 (23.2%); 3–5 years, 338 (33.4%); 6–10 years, 309 (30.6%); and >11 years, 119 (11.8%) (Figure 1 ②-B).

③ Type of athletic event: dance, 927 (91.7%); marathon, 298 (29.5%); and track racing, 296 (29.2%) (multiple responses allowed) (Figure 1 ③).

④ Sports experience besides unicycling: No other sports, 336 (33.2%); swimming, 129 (12.8%); track and field, 66 (6.5%); and tennis, 23 (2.3%).

⑤ Practice sessions per month for dance: 13–16 times, 209 (22.5%); 17–20 times, 198 (21.4%); and >21 times, 164 (17.7%).

Practice sessions per month for marathon: 4–5 times, 78 (26.2%); 2–3 times, 59 (19.8%); and >8 times, 36 (12.1%).

Practices sessions per month for track racing: 4–5 times, 67 (22.6%); >8 times, 47 (15.9%); and 2–3 times, 32 (10.8%).

⑥ Size of unicycle: 20 inches, 880 (87.0%); 24 inches, 119 (11.8%); and 16 inches, 84 (8.3%) (multiple responses allowed) (Figure 1 ⑥-A).

Crank length (20 inches): <89 mm, 723 (82.2%); 102 mm, 133 (15.1%); and 114 mm, 9 (1.0%) (Figure 1 ⑥-B).

⑦ Groin pain: presence, 172 (17.0%) and absence, 835 (82.6%) (Figure 1 ⑦).

⑧ Time of pain onset after taking up the unicycle: 3–4 years, 37 (21.5%); 5–6 years, 32 (18.6%); 1–2 years, 29 (16.9%); 7–9 years, 26 (15.1%); and >10 years, 22 (12.8%) (Figure 1 ⑧).

⑨ Intensity of groin pain (1–100 using visual analog scale): 20–30, 40 (23.3%); 40–60, 77 (44.8%); and 70–80, 38 (22.1%) (Figure 1 ⑨).

⑩ Site of symptoms: Anterior inguinal area: left, 83 (48.3%); right, 97 (56.4%); lateral peritrochanteric area: left, 22 (12.8%); right, 25 (14.5%); and hip area: left, 21 (12.2%); right, 21 (12.2%) (multiple responses allowed) (Figure 1 ⑩).

⑪ Cause of groin pain (closed question): Repeated practice necessary for body flexibility (e.g. the performance of Y-balance, I-balance, and Biellmann (free leg grasped from behind and pulled overhead)), 77 (44.8%); riding in a lordotic position during a race or marathon, 33 (19.2%); repeated touchdown impacts, 48 (27.9%); and other causes, 62 (36.0%).

⑫ Symptoms other than groin pain: Presence, 84 (48.8%) and absence, 76 (44.2%).

Table 1 shows age distribution according to the presence/absence of groin pain. Owing to the large number of athletes aged 19 years or younger, athletes were divided into two subgroups (6–12 years and 13–19 years). The results showed that groin pain was more common in those aged 13–19 years than in those aged 6–12 years (p < 0.01; Table 2).

Table 1.

Relationship between groin pain and age.

	Age (years)
Groin pain	≤9	10–19	20–29	30–39	40–49	≥50	N/A	Total
Presence	17 (9.9%)	130 (75.6%)	20 (11.6%)	3 (1.7%)	1 (0.6%)	1 (0.6%)	—	172
Absence	208 (24.9%)	565 (67.7%)	28 (3.4%)	11 (1.3%)	4 (0.5%)	18 (2.2%)	1 (0.1%)	835

Table 2.

Relationship between groin pain and age in athletes aged 19 years or younger.

	Age group
Groin pain	6–12	13–19
Presence	64 (11%)	83^a (25%)
Absence	530 (89%)	243 (75%)

^a p < 0.01.

When focusing on the relationship between groin pain and the length of athletic career, we found that athletes riding for >6 years had a significantly higher rate of groin pain than inexperienced athletes (p < 0.01; Table 3). However, when focusing on the type of athletic event, we found that neither practice time nor the type of unicycle showed a significant relationship with groin pain.

Table 3.

Relationship between groin pain and the length of athletic career.

	Career (years)
Groin pain	≤1	1–2	3–5	6–10	11	N/A	Total
Presence	—	13 (7.6%)	47 (27.3%)	66^a (38.4%)	45^a (26.2%)	1 (0.5%)	172
Absence	5 (0.6%)	222 (26.6%)	289 (34.6%)	241 (28.9%)	74 (8.9%)	4 (0.5%)	835

^a p < 0.01.

Discussion

The results of the questionnaire survey revealed that 17% of unicyclists complained of groin pain, particularly those aged 13–19 years and athletes with a career lasting more than 6 years.

There are three main types of unicycle events: dance, track racing, and marathon. Athletic events are held nationwide and include the unicycling world championships. During a dance competition, unicyclists dance to music alone, in pairs, or in a group and are scored on creativity, beauty, and completeness. In track racing, unicyclists compete in a short distance race or in a steeplechase race. In a marathon, unicyclists compete over long distances (42.195 km for the marathon). Thus, the characteristics of unicycle competition vary in terms of the event.

An estimated 3360 patients were treated for unicycle injuries from 1991 to 2010 in the United States emergency departments. Of the documented injuries, fractures and extremity injuries are the most common. Data from the National Electronic Injury Surveillance System suggest that of all unicycle injuries recorded, fractures represent approximately one-third (32.9%) and more than half (52.9%) involve an extremity.⁵ However, data about the other types of injuries suffered by competitive unicycle riders are limited. Previous case reports involve atypical cases of preadolescent unicyclists presenting with hip joint disorders.^3,4 These cases involved FAI and borderline developmental dysplasia of the hip (DDH). Indeed, cam deformity and DDH are the risk factors of OA of the hip, particularly in relatively young individuals.⁶ Excessive training, especially in juveniles, may cause a reactive osteochondromatous lesion; this is thought to be the origin of cam deformity.⁷ Thus, the age at which an individual takes up the unicycle (most were aged 6–9 years in our survey) is an important factor.

A systematic review reported that the specific causes of groin pain in surgically treated cases were FAI (32%), athletic pubalgia (24%), adductor-related pathology (12%), inguinal pathology (10%), and labral pathology (5%).⁸ Several studies have examined which sports activities cause groin pain^9

–12; however, few have conducted a questionnaire survey to assess prevalence in a specific sport.¹³ Results from the small number of published reports suggest that the prevalence of groin pain is as follows: 8.9% in soccer players, 1.9% in swimmers, 1.4% in marathon runners, and 1.3% in cross-country skiers. Looking at these numbers, the high rate (17%) of groin pain in unicycle athletes is striking. Moreover, our questionnaire survey revealed that the most common location of pain in unicycle athletes was the anterior inguinal area. The anterior inguinal area is often identified as a typical site of pain caused by a labrum lesion,¹⁴ while pain caused by an intra-articular lesion often presents in the central groin and lateral peritrochanteric areas. Thus, it is assumed that some unicyclists with groin pain may have a labrum lesion.

This study has several limitations. Because it is a questionnaire-based survey, we do not know the exact causes of groin pain in each individual. Groin pain may be due to causes other than the musculoskeletal system; examples include a groin hernia and the symptoms of nervous and gastrointestinal disorders.^9,15

–18 Therefore, the actual origin of groin pain remains unclear. Medical checks, including imaging, will be required. Future studies need to address the kinematic properties of unicycle activity using motion capture analysis. Better understanding of mechanical stresses experienced during unicycle activity will provide clues to the pathophysiology of groin pain.

Conclusion

This nationwide questionnaire survey was conducted to examine the prevalence of groin pain in unicyclists. Groin pain was reported by 17% of respondents. We found that unicyclists had relatively higher prevalence of groin pain compared to other sports. Unicyclists aged 13–19 years and those with an athletic career lasting more than 6 years are likely to suffer from groin pain. Therefore, we should be aware of the risk of this condition on the premise of FAI or other hip disorders, particularly in young unicycle athletes reporting groin pain. In addition, it should be considered that in unicyclists with groin pain, they need to take rest period or reduce time on training.

Footnotes

Acknowledgments

This work was supported by the Japan Unicycle Association (Tokyo, Japan). The authors thank all subjects for volunteering to participate in this study.

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Ethical approval

This project received ethical approval from the Yokohama City University ethical committee.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

ORCID iD

Daigo Kobayashi

Naomi Kobayashi

Takayuki Oishi

References

Kocjan

Sarabon

. The effect of unicycle riding course on trunk strength and trunk stability functions in children. J Strength Cond Res 2017; 24. Online ahead of print.

Frank

Ukwuani

Clapp

, et al. High rate of return to cycling after hip arthroscopy for femoroacetabular impingement syndrome. Sports Health 2018; 10: 259–265.

Baba

Shitoto

Kaneko

, et al. Premature osteoarthritis of the hip in unicyclists: two case reports. Clin J Sport Med 2011; 21: 362–364.

Nishikino

. Hip arthroscopic surgery after a diagnosis of premature osteoarthritis of the hip in three unicyclists: a case series. J Orthop Case Rep 2018; 8: 51–54.

Wang

. Unicycle injuries in the United States. J Emerg Med 2013; 45: 502–507.

Saberi Hosnijeh

Zuiderwijk

Versteeg

, et al. Cam deformity and acetabular dysplasia as risk factors for hip osteoarthritis. Arthritis Rheumatol 2017; 69: 86–93.

Matsuda

Kobayashi

Inaba

, et al.

Reactive osteochondromatous lesion of the femoral neck in a highly active preadolescent patient: Is this the pathogenesis of a cam deformity?

Clin J Sport Med 2018; 28: e95–e97.

de Sa

Holmich

Phillips

, et al. Athletic groin pain: a systematic review of surgical diagnoses, investigations and treatment. Br J Sports Med 2016; 50: 1181–1186.

Cohn

Lerebours

Strauss

. Sports hernia and extra-articular causes of groin pain in the athlete. Bull Hosp Jt Dis (2013) 2015; 73: 90–99.

10.

Leitner

. Groin pain in a young athlete. JAAPA 2013; 26: 61–62.

11.

Meyers

Foley

Garrett

, et al. Management of severe lower abdominal or inguinal pain in high-performance athletes. PAIN (Performing Athletes with Abdominal or Inguinal Neuromuscular Pain Study Group). Am J Sports Med 2000; 28: 2–8.

12.

Polglase

Frydman

Farmer

. Inguinal surgery for debilitating chronic groin pain in athletes. Med J Aust 1991; 155: 674–677.

13.

Paajanen

Ristolainen

Turunen

, et al. Prevalence and etiological factors of sport-related groin injuries in top-level soccer compared to non-contact sports. Arch Orthop Trauma Surg 2011; 131: 261–266.

14.

Philippon

Maxwell

Johnston

, et al. Clinical presentation of femoroacetabular impingement. Knee Surg Sports Traumatol Arthrosc 2007; 15: 1041–1047.

15.

Hureibi

McLatchie

. Groin pain in athletes. Scott Med J 2010; 55: 8–11.

16.

Robertson

Barker

Fahrer

, et al. The anatomy of the pubic region revisited: implications for the pathogenesis and clinical management of chronic groin pain in athletes. Sports Med 2009; 39: 225–234.

17.

Weber

Rehnitz

Ott

, et al. Groin pain in athletes. Rofo 2013; 185: 1139–1148.

18.

Yang

Nam

Kwon

, et al. Diagnosis of groin pain associated with sports hernia using dynamic ultrasound and physical examination: a case report. Ann Rehabil Med 2015; 39: 1038–1041.

Prevalence of groin pain in unicycle athletes: A nationwide questionnaire survey