Complications of hemophilia in the elbow: current management.

INTRODUCTION: After the ankle and knee, the elbow is the most commonly impaired joint in patients with hemophilia. AREAS COVERED: A Cochrane Library and PubMed (MEDLINE) search related to elbow problems in hemophilia was conducted. Early and continuous primary hematological prophylaxis (ideally starting in infancy) is essential, given that the juvenile elbow is highly prone to the musculoskeletal complications of hemophilia. If primary hematological prophylaxis is not administered (due either to lack of affordability or lack of venous access), persistent hemarthrosis can occur in the elbow. Hemarthroses will then require aggressive treatment (through arthrocentesis under factor factor coverage) to prevent progression to synovitis (requiring prompt radiosynovectomy or arthroscopic synovectomy) and ultimately hemophilic arthropathy (requiring rehabilitation and orthopedic surgery). Between the second and fourth decade of life, many patients with hemophilia present elbow joint destruction. EXPERT OPINION: In the initial stage of joint destruction, rehabilitation and intraarticular injections of hyaluronic acid can relieve the symptoms. In the advanced stage of hemophilic arthropathy, however, surgery is necessary. The main surgical procedures currently available are arthroscopic debridement, radial head resection, and total elbow arthroplasty. Transposition of the ulnar nerve and removal of heterotopic ossifications might also be necessary.

Electromyographic and Safety Comparisons of Common Lower Limb Rehabilitation Exercises for People With Hemophilia.

BACKGROUND: Ankles and knees are commonly affected in people with hemophilia and thus are targets for prevention or rehabilitation. However, to our knowledge, no studies have evaluated muscle activity and safety during exercises targeting the lower limbs in people with hemophilia; this lack of information hinders clinical decision-making. OBJECTIVE: The aim of this study was to compare the tolerability of, safety of, and muscle activity levels obtained with external resistance (elastic or machine)-based and non-external resistance-based lower limb exercises in people with hemophilia. DESIGN: This was a cross-sectional study. METHODS: Eleven people who had severe hemophilia and were undergoing prophylactic treatment participated. In a single experimental session, participants performed knee extension and ankle plantar flexion during 3 exercise conditions in random order: elastic band-based resistance (elastic resistance), machine-based resistance (machine resistance), and no external resistance. Exercise intensities for the 2 external resistance-based conditions were matched for perceived exertion. Muscle activity was determined using surface electromyography (EMG) for the rectus femoris, biceps femoris, gastrocnemius lateralis, and tibialis anterior muscles. Participants were asked to rate exercise tolerability according to a scale ranging from "very well tolerated" to "not tolerated" and to report possible adverse effects 24 and 48 hours after the session. RESULTS: No adverse effects were reported, and exercise tolerability was generally high. In the knee extension exercise, the rectus femoris normalized EMG values during the elastic resistance and machine resistance conditions were similar; 29% to 30% higher activity was obtained during these conditions than during the non-external resistance condition. In the ankle plantar flexion exercise, the gastrocnemius lateralis normalized EMG value was 34% higher during the machine resistance condition than without external resistance, and the normalized EMG values during the elastic resistance and other conditions were similar. LIMITATIONS: The small sample size and single training session were the primary limitations of this study. CONCLUSIONS: Exercises performed both with elastic bands and with machines at moderate intensity are safe, feasible, and efficient in people with severe hemophilia, providing comparable activity levels in the agonist muscles.

HemoKinect: A Microsoft Kinect V2 Based Exergaming Software to Supervise Physical Exercise of Patients with Hemophilia.

Patients with hemophilia need to strictly follow exercise routines to minimize their risk of suffering bleeding in joints, known as hemarthrosis. This paper introduces and validates a new exergaming software tool called HemoKinect that intends to keep track of exercises using Microsoft Kinect V2's body tracking capabilities. The software has been developed in C++ and MATLAB. The Kinect SDK V2.0 libraries have been used to obtain 3D joint positions from the Kinect color and depth sensors. Performing angle calculations and center-of-mass (COM) estimations using these joint positions, HemoKinect can evaluate the following exercises: elbow flexion/extension, knee flexion/extension (squat), step climb (ankle exercise) and multi-directional balance based on COM. The software generates reports and progress graphs and is able to directly send the results to the physician via email. Exercises have been validated with 10 controls and eight patients. HemoKinect successfully registered elbow and knee exercises, while displaying real-time joint angle measurements. Additionally, steps were successfully counted in up to 78% of the cases. Regarding balance, differences were found in the scores according to the difficulty level and direction. HemoKinect supposes a significant leap forward in terms of exergaming applicability to rehabilitation of patients with hemophilia, allowing remote supervision.

Safety of fascial therapy in adult patients with hemophilic arthropathy of ankle. A cohort study.

BACKGROUND: Hemophilic arthropathy is characterized by loss of function and chronic pain. Fascial therapy mobilizes the connective tissue, intervening in the state of the injured fascial complex and the surrounding tissues. OBJECTIVES: The aim of this study is to evaluate the safety of a physiotherapy program through fascial therapy in adult patients with hemophilic ankle arthropathy. DESIGN: Prospective cohort study. METHODS: Twenty-three adult patients with hemophilia from 26 to 65 years of age were recruited. The intervention consisted of three sessions of 45-minute fascial therapy for three consecutive weeks. An evaluation was carried out before as well as after treatment. The study variables were joint status (assessed with Hemophilia Joint Health Score), joint pain (using visual analogue scale), ankle range of motion (with a universal goniometer) and bleeding frequency (administering self-registration of bleeding). The mean difference was calculated using the Student's t-test for paired samples and using the Cohen formula we calculated the effect size of the dependent variables. RESULTS: None of the patients developed muscular or articular bleeding during the treatment period. After treatment, significant improvements (p < 0.05) in plantar flexion, ankle pain under load and joint condition were observed in both ankles. Similarly, we found improvement in left ankle dorsiflexion. CONCLUSIONS: The application of physiotherapy through fascial therapy does not appear to produce muscle or joint hemorrhages. A treatment through three sessions of fascial therapy may improve joint pain, mobility and joint ankle condition in patients with hemophilic arthropathy.

Exercise for haemophilia.

BACKGROUND: Haemophilia is a bleeding disorder associated with haemorrhaging into joints and muscles. Exercise is often used to aid recovery after bleeds, and to improve joint function in the presence of arthropathy. OBJECTIVES: Our objective was to systematically review the available evidence on the safety and effectiveness of exercise for people with haemophilia. SEARCH METHODS: We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group's Coagulopathies Trials Register and electronic databases PubMed, OVID-Embase, and CINAHL. We hand searched abstracts from congresses of the World Federation of Hemophilia and the European Hematology Association, trial registries and the reference lists of relevant articles.Date of the last search of the Cochrane Cystic Fibrosis and Genetic Disorders Group's Coagulopathies Trials Register: 14 December 2016. SELECTION CRITERIA: Randomized or quasi-randomized controlled studies comparing any exercise intervention considered relevant in haemophilia management including supervised, unsupervised, aquatic, strengthening, aerobic or cardiovascular, stretching, proprioceptive and balance training exercise programs in males of any age with haemophilia A or B of any severity (those with co-morbidities were not excluded). DATA COLLECTION AND ANALYSIS: Two authors reviewed the identified abstracts to determine their eligibility. For studies meeting the inclusion criteria, full articles were obtained. The two authors extracted data and assessed the risk of bias. Any disagreements were resolved by discussion. The authors contacted study investigators to obtain any missing data. MAIN RESULTS: Eight studies were included, which represented 233 males with all severities of haemophilia A and B, ranging in age from eight years to 49 years. Study duration ranged from four to 12 weeks. Exercise interventions varied greatly and included resistance exercises, isometric exercises, bicycle ergometry, treadmill walking and hydrotherapy; therefore, comparison between studies was difficult.None of the studies measured or reported adverse effects from the interventions. None of the studies reported outcomes regarding bleed frequency, quality of life or aerobic activity. Overall risk of bias across all studies was assessed as unclear.Very few studies provided sufficient information for comparison. None of the studies reported data that favoured the control group. One study reported that six weeks of resistance training improved joint health status (Colorado score) compared to controls. The addition of pulsed electromagnetic fields also improved ankle scores compared to exercises alone, but this was not seen in the elbows or knees.Two studies reported statistically significant improvements in pain intensity after exercise interventions compared to controls. Hydrotherapy exercises produced significant decreases in pain compared to controls and land-based exercise groups.Two studies found improvement in joint motion in the exercise group compared to controls. One study compared land- and water-based exercises; there was no difference in the range of motion between the two groups; however, the water-based exercise group did show improvement over the control group.One study, comparing joint traction and proprioceptive neuromuscular facilitation for the elbow to a control group, showed no differences in biceps girth or strength after 12 weeks of intervention.Some studies reported comparisons between interventions. In one study, treadmill training significantly improved balance in children compared to bicycle ergometry. Another study added partial weight bearing exercises to quadriceps exercises and showed improved walking tolerance.Four studies evaluated quadriceps or hamstring strength (or both). The addition of bicycle ergometry and exercises with weights was more effective than static exercises and treadmill walking for strengthening knee flexors and extensors. Partial weight-bearing exercises through range were more effective than static and short arc exercises for improving knee extensor strength. The addition of treadmill walking to ultrasound, stretching and strengthening exercises showed increased peak torque of knee flexors and extensors and decrease in knee effusion.The results should be interpreted with caution due to the quality of evidence (GRADE) as outlined in the summary of findings tables, which demonstrates that all but one of the outcomes assessed were rated as low or very low due to the small sample sizes and potential bias. AUTHORS' CONCLUSIONS: These results must be considered with caution. There is a lack of confidence in the results due to the small number of included studies and the inability to pool the results due to the heterogeneity of outcome measures. Most exercise interventions produced improvement in one or more of the measured outcomes including pain, range of motion, strength and walking tolerance. Hydrotherapy may be more effective than land exercises for pain relief in adults. Functional exercises such as treadmill walking and partial weight bearing exercises seem to be more effective than static or short arc exercises for improving muscle strength. These findings are consistent with the many non-controlled intervention reports in the haemophilia literature. No adverse effects were reported as a result of any of the interventions. However, some groups used prophylactic factor prior to exercise and other groups studied only subjects with moderate haemophilia. Therefore, the safety of these techniques for persons with severe haemophilia remains unclear.

Influencing factors on the functional level of haemophilic patients assessed by FISH.

Joint destruction in early adulthood brings the patients to the orthopaedic clinics. If a haemophilic patient becomes disabled, it shows a number of factors such as timely diagnosis, availability of appropriate treatment depending on the country, access and affordability to treatments and equally importantly the responsibility of the patient in managing self care by remaining compliant by prescribed treatment regimen. We assessed the functional level by functional independence score in haemophilia (FISH). Overall, 104 patients with haemophilia A and 29 with haemophilia B were evaluated. We assessed the function of the patients by FISH. We divided the sum scores into weak (FISH score 8-16), moderate (17-24), and good (25-32). For evaluating the level of functional deficit in a 2 × 2 table, we categorized the weak and moderate levels into Disordered Group and the good level into Not-Disordered Group. The average age was 26.9 ± 14.24. Each 1 year increase in age can increase 1.07 fold the possibility of being placed in Disordered Function Group. Severe haemophilia can increase 7.34 fold, presence of inhibitor can increase 9.75 fold and home self-care increases 3.89 fold the possibility of being placed in Disordered Function Group. To decrease the burden of the cost on patient, family and the government, education plays the most important role. We suggest that we send a trained team of physician and nurses to the deprived villages and cities instead of waiting for the patient to refer to our Care Center.

The effect of neutral-cushioned running shoes on the intra-articular force in the haemophilic ankle.

BACKGROUND: The ankle continues to be one of the most affected joints in the haemophilia patient, and as cartilage damage progresses, the joint can feel unstable, painful and stiff. Anecdotally, patients often report that sports trainers can improve their pain and daily function, however the actual mechanism for this remains unclear. METHODS: Nine patients with ankle haemarthropathy and three controls were examined using 'CODAmotion' analysis and a force plate. Kinematic and kinetic variables of the hip, knee and ankle were recorded. Data was imported from CODA to Excel, where a programme using 2D modelling of the ankle joint forces was employed. This calculated intra-articular force from heel strike to toe-off. FINDINGS: The haemophilia group at midstance showed an increase in intra-articular force in the ankle when wearing the trainer compared to the shoe (P=<0.05). Overall the haemophilia cohort had an increased joint force in both the trainers and shoes, compared to controls. INTERPRETATION: The type of footwear worn by individuals with ankle arthropathy has a significant effect on the amount of force acting at the joint surface. Sports shoes, in providing better comfort and foot support, may facilitate an increased muscular activity around the ankle and therefore improved dynamic joint stability, accounting for why some patients with ankle arthropathy report less pain. Further research is needed to establish levels of acceptable force and the combined effects of orthotics and footwear.

The effect of secondary prophylaxis versus episodic treatment on the range of motion of target joints in patients with haemophilia.

This study prospectively compared the effect of secondary prophylaxis to episodic treatment on target joint (TJ) range of motion (ROM), number of joint haemorrhages and new TJ development in patients with moderate or severe haemophilia. Two-hundred and eighty-six males, 17% in prophylaxis, 83% in episodic treatment group, participating in the Centers for Disease Control and Prevention's Universal Data Collection project, fulfilled inclusion criteria: age >2 years at enrollment, free of TJs at enrollment, developed at least one TJ after enrollment, and received either prophylaxis or episodic treatment continuously for two follow-up visits after TJ development. The outcomes of interest - percentage change in TJ ROM, number of joint haemorrhages and new TJ development, were modelled using multivariate linear, Poisson and logistic regression techniques respectively. Individuals who received secondary prophylaxis in comparison to episodic treatment were younger at TJ development (P < 0.01); there was no difference in the decrease in TJ ROM between the two groups (P = 0.9). Factors significantly associated with a higher rate of haemarthroses included episodic treatment, severe haemophilia, age >5 years at TJ development, obesity and inhibitor negative status. Secondary prophylaxis significantly decreased haemarthroses but was not associated with a significant improvement in TJ ROM or with new TJ development.

The role of physical medicine and rehabilitation in haemophiliac patients.

Physical medicine and rehabilitation aim to evaluate, diagnose and treat disability in haemophiliac patients, while preventing injury or deterioration. They also aim to maintain the greatest degree of functional capacity and independence in patients with haemophilia, or to return them to that state. Rehabilitation, together with clotting factor replacement therapy, has revolutionized the management of these patients in developed countries and reduced their morbidity/mortality rates. A knowledge of the musculoskeletal signs and symptoms of haemophilia is essential for providing a treatment which is suitable and customized. Physical medicine and rehabilitation techniques, which are based on physical means, are intended to reduce the impact which these injuries and their consequences or sequelae can have on the quality of life of patients with haemophilia. Under ideal haemostatic control conditions (primary prophylaxis), people with haemophilia could achieve good physical condition which will allow them to enjoy both physical activity and a daily life without limitations. Currently, children undergoing primary prophylaxis are quite close to this ideal situation. For these physical activities to be carried out, the safest possible situations must be sought.

Clinical and functional evaluation of the joint status of hemophiliac adults at a Brazilian blood center

BACKGROUND: Hemophilia is a potentially disabling condition as hemophilic arthropathy develops early in life and is progressive, especially in patients treated in an on-demand regime. Objective: This study aimed to describe the structural joint status and the functional independence score of hemophiliac adults and correlate structural damage with the functional deficits found in these patients. METHODS: Hemophiliacs at the Juiz de Fora Regional Blood Center - HEMOMINAS Foundation, aged 18 years and over and treated in an on-demand regime, were clinically evaluated in respect to structural joint damage using the World Federation of Hemophilia Physical Examination Scale (WFH-PE) and functional deficits using the Functional Independence Score in Hemophilia (FISH). The Spearman rank test was used to evaluate the correlation between the two scores. RESULTS: Thirty-nine patients were evaluated. The mean age was 36.8 years. Target joints were detected in 69.2% of patients studied. The mean Physical Examination Scale and Functional Independence Score were 16.87 and 25.64, respectively. Patients with mild hemophilia showed no significant joint involvement. Patients with severe or moderate hemophilia had similar results regarding structural damage (p-value < 0.001) and functional deficits (p-value = 0.001). There was statistical significance in the correlation between the two scores (r = -0.850; p-value = 0.01). CONCLUSIONS: The World Federation of Hemophilia Physical Examination Scale and Functional Independence Score in Hemophilia may be useful to clinically assess structural joint damage and functional deficits in hemophiliacs as the tools are inexpensive and easy to administer and may be able to detect hemophilic arthropathy, which results from recurrent hemarthrosis and is common in the population studied.

Physiotherapy home exercise program for haemophiliacs.

BACKGROUND: Regular physiotherapy can improve the stability and flexibility of joints and decrease the bleeding risk in patients with haemophilia. To reduce the appointments for the patients and to make exercising a part of daily live, an individualized home exercise program (HEP) was designed. Retrospectively the number of bleedings during the HEP was compared to number of bleedings before. METHOD: 8 patients aged between 4 and 16 years with haemophilia A were evaluated. At start and after 13 month patients had a motion analysis via topographic ultrasound. According to the results and clinical findings an individualized HEP was created. Standardised scores for clinical evaluation and the patient based evaluation of exercises were designed. At every appointment exercises were individually adjusted. RESULTS: Patients exercised in median 1.7 times a week. No training related bleeds occurred. 7 of 8 patients showed reduced joint and/or muscle bleeds (p<0.02). Clinical scores raised slightly in every patient. However the second motion analysis of squat and gait showed a worsening in 7 of 8 patients (p>0.05). CONCLUSION: A HEP can help to advance in physical fitness and coordination and may reduce bleeding tendency, but needs to be accomplished regularly. Patients are interested but the motivation to exercise at home is low. Disorders measured by motion analysis seem not to be sufficiently influenced by our surrogate training program.

Role of exercise and physical activity on haemophilic arthropathy, fall prevention and osteoporosis.

In older men with haemophilia, arthropathy resulting from a lifetime of intra-articular bleeding contributes to the loss of independence and increased morbidity that occurs with age. A regular exercise programme that incorporates aerobics, strength training and balance and flexibility activities is a key component of successful ageing, helping to improve functional mobility and reduce the risk of falls, osteoporosis and osteoporotic fractures. Because of the special challenges associated with haemophilia, which include both the underlying coagulopathy and, in many cases, extensive joint damage, patients beginning an exercise regimen should be referred to appropriately trained physiotherapists (preferably someone associated with a haemophilia treatment centre) for evaluation, education and instruction and follow-up. Various assistive devices may make exercise easier to perform and more comfortable.

The role of the physiatrist in the haemophilia comprehensive care team in different parts of the world.

The role of the physiatrist, as a member of the multidisciplinary haemophilia comprehensive care team, is to prevent and treat activity limitations and restriction of participation on the part of the patient. . This role is threefold: (i) provide education to the patients, families and healthcare providers to detect disabling injuries and take adequate precautions; (ii) provide specialized treatment of musculoskeletal disabilities striving for the highest level of functionality and (iii) Stimulate the patient's full participation in socio-economic activities of his country. Prominent physiatrists from different parts of the world describe the situation in Armenia, China, Egypt, France, Indonesia (and the Philippines), the Netherlands and South America.

Orthopaedic management of haemophilia arthropathy of the ankle.

Joint bleeding, or haemarthrosis, is the most common type of bleeding episode experienced by individuals with haemophilia A and B. This leads to changes within the joints, including synovial proliferation, which results in further bleeding and chronic synovitis. Blood in the joint can also directly damage the cartilage, and with repeated bleeding, there is progressive destruction of both cartilage and bone. The end result is known as haemophilic arthropathy. The joints most commonly affected are the knees, elbows and ankles, although any synovial joint may be involved. In the ankle, both the tibiotalar and subtalar joints may be affected and joint bleeding and arthropathy can lead to a number of deformities. Haemophilic arthropathy can be prevented through regular factor replacement prophylaxis and implementing physiotherapy. However, when necessary, there are multiple surgical and non-surgical options available. In early ankle arthropathy with absent or minimal joint changes, both radioisotopic and chemical synoviorthesis can be used to reduce the hypertrophied synovium. These procedures can decrease the frequency of bleeding episodes, minimizing the risk of articular cartilage damage. Achilles tendon lengthening can be performed, in isolation or in combination with other surgical measures, to correct Achilles tendon contractures. Both arthroscopic and open synovectomies are available as a means to remove the friable villous layer of the synovium and are often indicated when bleeding episodes cannot be properly controlled by factor replacement therapy or synoviorthesis. In the later stages of ankle arthropathy, other surgical options may be considered. Debridement may be indicated when there are loose pieces of cartilage or anterior osteophytes, and can help to improve the joint function, even in the presence of articular cartilage damage. Supramalleolar tibial osteotomy may be indicated in patients with a valgus deformity of the hindfoot without degenerative radiographic findings. Joint fusion, or arthrodesis, is the treatment of choice in the advanced stages of ankle arthropathy although total ankle replacement is currently available. Early ankle replacement components were associated with a poor outcome, but as implant designs have improved, there have been successful outcomes achieved. As the ankle is a commonly affected joint in many individuals with haemophilia, it is important to add to the knowledge base to validate indications and timing of surgical and non-surgical interventions in ankle arthropathy.

The role of physiotherapy after total knee arthroplasty in patients with haemophilia.

With the availability of clotting factor concentrates, advances in surgical techniques, better implant design, and improvements in postoperative management, total knee arthroplasty has become the treatment of choice for haemophilia patients suffering from end-stage haemophilic knee arthropathy. The success of this surgery is also dependent on close collaborations among the orthopaedic surgeon, the haematologist and the physiotherapist. Although haemophilic patients undergoing this surgery would likely benefit from a targeted rehabilitation programme, its specificities, modalities and limitations have thus far not been extensively studied. Employing the published data of rehabilitation after knee prosthesis in patients with osteoarthritis and haemophilic arthropathy along with clinical experience, the authors present a comprehensive and original review of the role of physiotherapy for patients with haemophilia undergoing knee arthroplasty.

Domiciliary application of CryoCuff in severe haemophilia: qualitative questionnaire and clinical audit.

The acute management of haemophilic bleeding episodes in the home setting is based on the concept of immediate factor replacement therapy and the PRICE regime--an acronym representing the concepts of Protection, Rest, Ice, Compression and Elevation [1,2]. Integral to this regime is the application of cold therapy, and yet little is known regarding the safe periods of application, or the relative safety of cryotherapy devices such as the CryoCuff when used in the home setting by patients suffering from severe haemophilia and related bleeding disorders. This study examines the subjective patient response to the application of the CryoCuff device in the home setting in terms of the effect on pain, joint swelling and the return to 'pre-bleed status' of the knee, ankle or elbow in patients with severe haemophilia A/B or type III von Willebrand's disease (VWD) immediately following haemarthrosis, and any potential adverse effects related to the device or recommended duration of application as stated in the PRICE guideline (Fig. 1). Twelve patients, either with severe haemophilia A/B or with VWD were recruited and asked to use the CryoCuff device as part of the PRICE regime immediately following the onset of knee-, ankle- or elbow bleeds for the next one year. Each subject was then sent a qualitative questionnaire to determine subjective responses to the device. All patients reported that the application protocol was easy to follow, they were able to apply the device as per the PRICE regime and they were able to tolerate it for the recommended period. Whereas, all the patients felt that the device had a significant impact on alleviation of pain and return to pre-bleed status, 78% of the patients felt that the device led to a significant reduction in swelling around the affected joint. There was no conclusive evidence that the device resulted in any reduction in the amount of factor used to treat the acute bleeding episode, however, no patients reported any perceived delay in achieving haemostasis or required extra factor replacement therapy consequent to the usage of the device. No other adverse effects were reported by participants in this study.

The role of rehabilitation and sports in haemophilia patients with inhibitors.

Treatment of haemophilia patients with inhibitors against factor VIII/IX (FVIII/IX) is still challenging and recurrent haemarthroses cause arthropathy with associated restrictions on participation in physical activities and sports. Rehabilitation is a multidisciplinary approach which includes physiotherapy, occupational therapy, psychology, social work and technical applications like prostheses, orthoses (splints and braces), shoe adaptations, walking aids and adaptations in the house and work situation, but also education. The theoretical principles and practical advice regarding rehabilitation and physiotherapy for both children and adults with haemophilia without inhibitors are highly applicable for patients with inhibitors. Hydrotherapy is useful in the treatment of painful or stiff joints and/or muscles after an acute haemarthrosis, muscle bleeds and chronic arthropathy. In addition, it is of use in cases of chronic synovitis and to start mobilization after long periods of bed rest or during the weaning of a splint. In cases of bleeding and arthropathy, adequate treatment of pain is very important, as are functional exercises. Everyone should be physically active for 30-60 min day(-1). Participation in sports is recommended for people with haemophilia, the best sport being swimming. Children should participate in sports appropriate to their size and physical characteristics.