Isokinetic Assessment and Musculoskeletal Complaints in Paralympic Athletes: A Longitudinal Study

Authors: Andressa Silva, PhD Gisele Zanca, PhD Eduardo Silva Alves, Msc Valdir de Aquino Lemos, Msc Sebastia˜o Augusto Ga´vea, Msc Ciro Winckler, PhD Stela Ma´rcia Mattiello, PhD Ronnie Peterson, Msc Roberto Vital, PhD Sergio Tufik, PhD Marco Tu´lio De Mello, PhD

Affiliations: From the Brazilian Paralympic Committee (Comiteˆ Paraolı´mpico Brasileiro) (AS, CW, RP, RV, MTDM), Brası´lia, Distrito Federal; Center of Studies on Psychobiology and Exercise (Centro de Estudos em Psicobiologia e Exercı´cio) (AS, ESA, VdAL, SAG, ST, MTDM), Sa˜o Paulo, Sa˜o Paulo; Federal University of Sa˜o Carlos (Universidade Federal de Sa˜o Carlos) (GZ, SMM), Sa˜o Carlos, Sa˜o Paulo; Federal University of Sa˜o Paulo (Universidade Federal de Sa˜o Paulo) (ESA, VdAL, CW, ST), Sa˜o Paulo, Sa˜o Paulo; Federal University of Minas Gerais (Universidade Federal de Minas Gerais) (AS, MTM).

Correspondence: All correspondence and requests for reprints should be addressed to: Marco Tu´lio de Mello, PhD, Universidade Federal de Minas Gerais, 4664, Av. Presidente Carlos Luz, Belo Horizonte/MG, Campus Pampulha, CEP: 31310-250, Brasil.

Disclosures: Financial disclosure statements have been obtained, and no conflicts of interest have been reported by the authors or by any individuals in control of the content of this article.

0894-9115/15/0000-0000 American Journal of Physical Medicine & Rehabilitation Copyright * 2015 Wolters Kluwer Health, Inc. All rights reserved. DOI: 10.1097/PHM.0000000000000244

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Paralympic Athletes

ORIGINAL RESEARCH ARTICLE

Isokinetic Assessment and Musculoskeletal Complaints in Paralympic Athletes A Longitudinal Study ABSTRACT Silva A, Zanca G, Alves ES, de Aquino Lemos V, Ga´vea SA, Winckler C, Mattiello SM, Peterson R, Vital R, Tufik S, De Mello MT: Isokinetic assessment and musculoskeletal complaints in paralympic athletes: a longitudinal study. Am J Phys Med Rehabil 2015;00:00Y00.

Objective: The aim of this study was to assess and monitor the peak torque of the knee extensor and flexor muscles in flexion and extension and the reports of musculoskeletal complaints in members of the main Brazilian Paralympic athletics team through 1 yr. Design: Fourteen healthy athletes from both sexes were assessed three times in 1 yr. The volunteers were assessed for the presence of musculoskeletal complaints and muscle strength at three time points: (1) at the onset of the preparatory phase on December 2009, (2) at a follow-up assessment on June 2010, and (3) before actual competition on December 2010. The athletes’ self-reported musculoskeletal complaints were assessed in structured interviews, and the muscle strength was assessed by means of isokinetic dynamometry.

Results: The knee flexor and extensor muscle strength exhibited significant increase in both the right and left lower limbs at the second and third assessments compared with the first one (P G 0.05). Muscle imbalance was associated with knee and thigh complaints at all three assessments (P G 0.05).

Conclusions: The knee flexor and extensor muscle strength exhibited a gradual increase in both lower limbs during the course of the three assessments. In parallel, muscle imbalance was associated with the occurrence of knee and thigh complaints. Key Words:

Isokinetic Assessment, Injury Reports, Para-Athletics, Paralympic Athletes

Isokinetic Assessment in Paralympic Athletes

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Procedures

P

articipation in sports activities for people with impairments continues to increase in popularity. The Paralympic Games are the primary sporting event involving athletes with impairments and afford them an opportunity to practice high-level sports.1 In addition to the physical skills and muscle strength required to achieve satisfactory performance in competitions,2Y4 eventual musculoskeletal complaints should also be considered, as they might interfere directly in the athletes’ performance.5 The study conducted by Willick et al.1 on the 2012 Paralympic Games in London found an incidence of 12.7 injuries/1000 athletes. Magno et al.6 assessed visually impaired athletes in five international competitions from 2004 to 2008 and found a prevalence of 78% of injuries with a clinical incidence of 1.93 injuries per athlete, where overuse injuries accounted for 82% and traumatic injuries accounted for 18%. Ferrara and Peterson7 found that the location of injuries in disabled athletes seems to be impairments and sport dependent. For instance, lower extremity injuries are more common in ambulatory athletes (e.g., visually impaired, limb deficiency, cerebral palsy), whereas upper extremity injuries are more frequent in athletes who use a wheelchair. In addition,8,9 studies showed that muscle imbalances between knee flexor and extensor assessed by isokinetic dynamometry increase the chance of lower limb injuries in people without impairments. To the best of the authors’ knowledge, this study was the first study that simultaneously assessed the musculoskeletal complaints and peak torque (PT) values of the knee extensor and flexor muscles in Paralympic athletes for 1 yr. This subject is highly relevant in sports medicine, as it could lead to novel strategies to minimize the occurrence of injuries and muscle pain, enabling Paralympic athletes to improve their performance in high-level competitions as well as their overall quality of life.

METHODS Study Population This longitudinal study was composed of 14 healthy athletes from the Brazilian para-athletic team, 10 men and 4 women, with a mean (Tstandard deviation) age of 28.9 T 6.3 yrs, with weight of 66.1 T 9.4 kg and height of 171.7 T 10.2 cm. Six participants were visually impaired athletes, three were with limb deficiencyVupper limb and distal lower limbVand five were athlete guides. All participate in national and international events.

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Following a thorough explanation of the risks involved in the study, all the volunteers signed an informed consent form before enrollment. The study was approved by the research ethics committee of the Federal University of Sa˜o Paulo (CEP 0294/11). The volunteers were assessed for the presence of musxculoskeletal complaints and muscle strength at three time points: (1) at the onset of the preparatory phase on December 2009, (2) at a follow-up assessment on June 2010, and (3) before actual competition on December 2010. All three assessments were part of the process of preparation for the 2011 IPC Athletics World Championships in Christchurch, conducted at the Center of Studies on Psychobiology and Exercise (Centro de Estudos em Psicobiologia e Exercı´cio), Sa˜o Paulo, Brazil. The athletes of the main Brazilian para-athletic team were followed up throughout the preceding year, and all the musculoskeletal complaints reported by the athletes at medical and physical therapy assessments were recorded. Only the complaints reported at such assessments were included for analysis in this study.

Physical Assessment The participants’ muscle strength was assessed using an isokinetic dynamometer (Biodex MultiJoint System 3; Biodex Medical Inc, NY). The device was calibrated following the manufacturer’s instructions. Warm-up was performed before each assessment on a cycle ergometer at 75 W and constant speed of 20 km/hr for 5 mins, followed by overall lower limb elongation. For the assessment, the volunteers sat on the device chair with the knees at 90-degree flexion; their position was fixed by means of belts across the trunk and pelvic area. The dynamometer mechanical axis of rotation was aligned with the femoral lateral epicondyle, and the resistance was distally applied to the ankle joint 5 cm above the medial malleolus. The participants were instructed to keep the arms crossed over the chest all along the test to avoid compensatory movements and were verbally encouraged to achieve maximum torque during the muscle contractions.10 The amplitude of movement assessed was 90 degrees, that is, between full knee extension and 90-degree flexion. The assessments were performed in concentric/concentric mode at three different velocities in increasing order. First, the volunteers performed three submaximal repetitions at each assessed velocity to acquaint themselves with the device, and after resting for 1 min, they were requested to perform 5, 10, and 15 maximal flexion

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and extension repetitions at velocities of 60, 180, and 300 degrees/sec, respectively, with 1-min intervals in between. Both lower limbs were assessed, and the order of assessment was random. The muscle strength of the knee flexors and extensors was assessed based on the PT values. The athletes’ muscle balance was assessed based on the hamstring-to-quadriceps (H/Q) PT ratio and the bilateral deficit (percent PT difference between the right and left lower limbs). Muscle imbalance was defined as a bilateral deficit greater than 20%11and an H/Q ratio lower than 47% at a velocity of 60 degrees/sec.12

Statistical Analysis The results were expressed as means T standard deviation. The data distribution was investigated using

the Shapiro-Wilk normality test. Repeated measures analysis of variance was used to compare the normal continuous variables among the three time points of assessment. The analysis was performed using software Statistica.13 The significance level was established as P G 0.05.

RESULTS Figure 1 depicts the PT values of the left and right knee extension and flexion at 60, 180, and 300 degrees/sec at the three assessments. The right and left knee extension PT values at 60 degrees/sec were significantly higher at the second (Ps = 0.001 and 0.003, respectively) and third (Ps = 0.001 and 0.004, respectively) assessments compared with the first (Fig. 1A).

FIGURE 1 Peak quadriceps extensor torque of the right and left lower limbs at 60, 180, and 300 degrees/sec at three assessment time points, expressed as mean T standard deviation. *, differs from the first assessment. www.ajpmr.com

Isokinetic Assessment in Paralympic Athletes

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The right and left knee extension PT values at 180 degrees/sec were significantly higher at the second (Ps = 0.001 and 0.003, respectively) and third (Ps = 0.001 and 0.004, respectively) assessments compared with the first (Fig. 1B). The right and left knee extension PT values at 300 degrees/sec were also significantly higher at the second (Ps = 0.001 and 0.003, respectively) and third (Ps = 0.001 and 0.002, respectively) assessments compared with the first (Fig. 1C). Figure 2 depicts the right and left knee flexion PT values at 60, 180, and 300 degrees/sec at the three assessments. The right and left knee flexion PT values at 60 degrees/sec were significantly higher at the second (Ps = 0.003 and 0.005, respectively) and

third (Ps = 0.001 and 0.002, respectively) assessments compared with the first (Fig. 2A). The right and left knee flexion PT values at 180 degrees/sec were significantly higher at the second (Ps = 0.005 and 0.003, respectively) and third (Ps = 0.001 and 0.021, respectively) assessments compared with the first (Fig. 2B). The right knee flexion PT values at 300 degrees/sec were also significantly higher at the third (P = 0.001) and second (P = 0.001) assessments compared with the first one (Fig. 2C). Table 1 describes the results of the H/Q ratio imbalance corresponding to the right and left lower limbs at the three assessments. The mean H/Q values for both the right and left lower limbs at 60

FIGURE 2 Peak quadriceps flexor torque of the right and left lower limbs at 60, 180, and 300 degrees/sec at three assessment time points, expressed as mean T standard deviation. *, differs significantly from the first assessment.

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TABLE 1 H/Q ratio values at the three assessments First Assessment

H/Q, 60 degrees/sec H/Q, 180 degrees/sec H/Q, 300 degrees/sec a

Second Assessment

Third Assessment

Right

Left

Right

Left

Right

Left

56.3 T 12.7 68.0 T 11.2 80.8 T 11.6

52.5 T 6.9 66.2 T 8.6 75.9 T 8.4

53.1 T 7.1 65.7 T 8.4 74.4 T 11.2a

53.2 T 3.4 65.5 T 6.3 73.8 T 6.6

56.0 T 10.1 66.3 T 9.2 76.7 T 9.9

53.9 T 6.7 64.6 T 7.3 74.0 T 6.6

P = 0.01, significant difference relative to the first assessment.

and 180 degrees/sec exhibited no significant difference among the three assessments. However, the H/Q ratio at 300 degrees/sec corresponding to the right knee exhibited significant reduction at the second assessment compared with the first one (P = 0.017). The numbers of athletes who did and did not exhibit a H/Q ratio imbalance (G47%) at 60 degrees/sec, associated or not with knee and thigh complaints, at each of the three assessments are shown in Table 2. Table 3 shows the musculoskeletal complaints of athletes during the three assessments.

In this study, the isokinetic assessments performed throughout 1 yr found an increase in the knee flexor and extensor muscles’ strength associated with a reduced incidence of muscle imbalance and occurrence of musculoskeletal complaints, corroborating the initial hypothesis. The maximum PT during isokinetic movement is a measure of the muscle strength under dynamic conditions.4 The assessments performed in this study showed that the athletes’ muscle strength increased independently of the velocity of movement. These results are most likely related to the time points selected for assessment, as the first was conducted at the onset of the training cycle, immediately after the end of vacation, when athletes are not in their best physical shape,16 as required during the competition phase.17 The second assessment was performed immediately after the end of the preparatory phase, when the athletes’ coaches most likely sought to achieve gains in strength and velocity. Despite that reduction, no significant differences were found relative to the first assessment.18 These results deserve attention, as they indicate that athletes might exhibit greater strength at the beginning of a subsequent training cycle as well as greater gains in strength throughout the competitive phase compared with the corresponding phases of the previous cycle. Through the analysis of bilateral strength differences and the antagonist/agonist ratio, isokinetic

DISCUSSION The results of this study show that the knee flexion and extension muscle strength exhibited a gradual increase in both the right and left lower limbs for the three assessments. In addition, muscle imbalance exhibited an association with knee and thigh complaints at all three assessments. A meta-analysis performed by Granacher et al.14 and the review study conducted by Hrysomallis15 found that muscle strength is one of the most relevant factors associated with physical performance in sports, regarding both high-level performance and injury prevention. In addition, assessment of muscle strength might contribute to the development of therapeutic procedures for the rehabilitation of injuries affecting the musculoskeletal system as well as to the identification of muscle strength deficits.2,4

TABLE 2 Number of athletes who presented imbalance in relation to H/Q (G47%) at 60 degrees/sec and the number of complaints related to the knee and thigh Imbalance

First assessment (n = 14) Second assessment (n = 14) Third assessment (n = 11)

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Without Imbalance

With Complaints

No Complaints

With Complaints

No Complaints

4 4 5

2 1 1

1 1 0

7 8 5

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TABLE 3 Types of musculoskeletal complaints at the three assessments Complaints at First Assessment (N = 14) Pubalgia (n = 1) Bilateral tibial periostitis (n = 2) Patellar tendonitis (n = 1) Thigh adductors (n = 1) Posterior thigh strain (n = 1) Achilles tendon (n = 1)

Complaints at Second Assessment (N = 14)

Complaints at Third Assessment (N = 11)

Bilateral tibial periostitis (n = 2) Thigh flexor tendonitis (n = 1) Posterior thigh strain (n = 1) Achilles tendon (n = 1) V V

Patellar chondromalacia (n = 2) Posterior thigh strain (n = 1) Achilles tendon (n = 1) V V V

assessment provides information relevant to the detection of injuries.8,9 In this study, analyzing the H/Q ratio mean values independently of the velocity of movement did not indicate differences among the three assessments performed, which suggests that the muscle balance of the sample as a whole was adequate in comparison with the reference values.12 Nevertheless, individual analysis found H/Q ratio values lower than 47% in six volunteers at the first and second assessments and in four participants at the third assessment. Two hypotheses might be proposed to account for these findings: (1) greater training overload and use of the knee extensor compared with the flexor muscles could result from the particular demands of the specific sports/ disciplines,19 and (2) the validity of the H/Q ratio as indicative of predisposition for injuries is still controversial.20 Therefore, the relationship between H/Q ratio and injuries should be analyzed cautiously. In the assessment of the bilateral relationship between the left and right lower limb muscle groups, the amount of muscle imbalance measured by the H/Q ratio is reduced, eventually reaching a value of zero in knee extension at a velocity of 60 degrees/sec. The preparation of the athletes assessed in this study included strength training protocols that, in addition to pursuing strength gains, also sought to achieve an appropriate muscle balance to reduce the occurrence of injuries. To equate the strength of the muscle groups in one limb to the contralateral ones, the training protocol included one-sided exercises that are commonly indicated for rehabilitation purposes in sports medicine.21,22 Many athletes complain of muscle injuries and discomfort during the training phase. An inverse correlation was observed between pain and the PT achieved in an isokinetic strength test of knee extension by individuals subjected to arthroscopy.23 A study found an inverse correlation between PT and pain in conditions such as osteoarthritis.24 This study did not identify any specific period of greater vulnerability to injury as a function of

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muscle imbalance. Corroborating the observations made by Silva et al.25 on the relevance of recording the musculoskeletal complaints reported by athletes, such complaints must be observed and recorded by a multiprofessional staff. In fact, the continuous care provided by a multiprofessional staff had a significant influence on the results achieved by the Brazilian team at the 2011 IPC World Athletic Championships held in Christchurch (New Zealand), which ranked third in the number of medals after China and England.26 This achievement is indicative of the development undergone by Brazilian athletes as well as of their improved performance at the competitive level and thus demonstrates the relevance of the efforts of the Brazilian Paralympic Committee to improve the training conditions and the athletes’ medical, physical therapy, and physiologic assessments.25 In summary, the strength of the right and left knee flexor and extensor muscles exhibited a gradual increase among the assessments. In parallel, a relationship between muscle imbalance and knee and thigh complaints was found at all three assessments after 1 yr. This type of assessment might be useful for healthcare professionals involved in the preparation of athletes to achieve a satisfactory musculoskeletal development. The authors suggest that the simultaneous investigation of athletes’ complaints and isokinetic assessment might contribute to the identification and treatment of injuries in Paralympic athletes. ACKNOWLEDGMENTS

The authors thank the Associac¸a˜o Fundo de Incentivo a Psicofarmacologia, Conselho Nacional de Desenvolvimento Cientifico e Tecnolo´gico, Centro Multidisciplinar em Sonoleˆncia e Acidentes, Centros de Pesquisa Expansa˜o e Difusa˜o do Instituto do Sono, Fundac¸a˜o de Amparo a Pesquisa do Estado de Sao Paulo, and the Centro de Estudos em Psicobiologia e Exercı´cio.

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24. Serra˜o PR, Gramani-Say K, Lessi GC, et al: Knee extensor torque of men with early degrees of osteoarthritis is associated with pain, stiffness and function. Rev Bras Fisioter 2012;16:289Y94

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25. Silva A, Mattiello SM, Peterson R, et al: Queixas musculoesquele´ticas e procedimentos fisioterapeˆuticos na Delegac¸a˜o Brasileira Paralı´mpica durante o Mundial Paralı´mpico de Atletismo em 2011. Rev Bras Med Esporte 2013;19:256Y9 26. International Paralympic Committee (IPC). Available at: http://www.paralympic.org. Accessed on June 18, 2011

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