Comparison between two clinical tests for evaluating the flexibility of the posterior muscles of the thigh

Abstracts

OBJETIVOS: Comparar os resultados dos testes de Dedos ao Chão e Elevação dos MMII em Extensão por meio da fotogrametria, verificar a concordância entre os achados do ângulo do quadril entre os dois testes e avaliar a confiabilidade intra e interavaliadores do procedimento de análise fotogramétrica. MÉTODO: Os testes foram aplicados em 35 sujeitos saudáveis do sexo masculino (média de 23 anos de idade ± 3, 170 cm de altura ± 4 e 68 Kg ± 11), que foram divididos em dois grupos com base na classificação dos testes. Marcadores superficiais foram colocados em referências ósseas para traçar os ângulos do quadril, tóraco-lombar, perna, joelho e tíbio-társico. Testou-se a confiabilidade do procedimento de análise fotogramétrica dos ângulos mensurados por dois avaliadores. RESULTADOS: Para o ângulo do quadril houve diferenças significativas entre os grupos de flexibilidade, nos dois testes, sendo que o ângulo foi menor nos sujeitos com flexibilidade reduzida. Houve uma diferença significativa de 22,8% entre a classificação designada pelos dois testes. Entretanto, o ângulo do quadril obteve altos índices de concordância entre os testes (ICC: 0,89 e diferença média de -0,85º). Os procedimentos de fotogrametria apresentaram altos índices de confiabilidade tanto intra quanto interavaliadores (ICC variando de 0,94 a 0,99). CONCLUSÃO: Os testes apresentaram diferenças na classificação de flexibilidade dos sujeitos. Entretanto, quando o ângulo do quadril foi considerado, houve alta concordância entre os resultados dos testes. Os procedimentos de análise fotogramétrica foram reprodutíveis tanto intra quanto interavaliadores, constituindo uma ferramenta útil de análise para os testes em questão.

Flexibilidade; amplitude passiva de movimento; exame físico; equilíbrio musculoesquelético; fotogrametria; confiabilidade

SCIENTIFIC ARTICLES

Comparison between two clinical tests for the evaluation of posterior thigh muscles flexibility

Carregaro RL; Silva LCCB; Gil Coury HJC

Physical Therapy Post-Graduation Program, São Carlos Federal University, São Carlos, SP - Brazil

^{Correspondence to}

ABSTRACT

OBJECTIVE: To compare the results from fingertip-to-floor and straight leg raise tests by means of photogrammetry, investigate the concordance of hip angle findings between the two tests and evaluate the intra and inter-examiner reliability of the photogrammetric analysis procedure.

METHOD: The tests were applied to 35 healthy male subjects (mean age 23 ± 3.4 years, height 170 ± 4 cm and weight 68 ± 11 kg). The subjects were divided into two groups on the basis of the test classifications. Surface markers were placed on bone references in order to calculate the hip, thoracolumbar, leg, knee and tibiotarsal angles. The reliability of the photogrammetric analysis procedure on the angles measured by two examiners was tested.

RESULTS: For the hip angle, there were significant differences between the flexibility groups in both tests, and subjects with reduced flexibility had lower angles. There was a significant difference (22.8%) between the classifications designated by the two tests. However, the hip angle showed high levels of concordance between the tests (ICC: 0.89 and mean difference of -0.85º). The photogrammetric procedures presented high reliability rates, both for intra and inter-examiner (ICC ranging from 0.94 to 0.99).

CONCLUSION: The tests presented differences in the classification of the subjects' flexibility. However, considering the hip angle, there was high concordance between the test results. The photogrammetric analysis procedures were reproducible, both for intra and for inter-examiner measurements, thus making this a useful analysis tool for the tests in question.

Key words: Flexibility, passive range of motion, physical examination, musculoskeletal equilibrium, photogrammetry, reliability.

INTRODUCTION

There seems to be no consensual definition for flexibility in the specialized literature. Differently from elasticity, which refers to the property of a tissue to return to its initial format¹, the term flexibility may have the simple definition of "the capacity of bending". In addition, it is found the term extensibility, defined as the range in which the joint may be moved passively, considering the influence of the muscular length^2,3. The definition adopted, in this study, considers flexibility as the capacity to move a joint through its available range of motion (ROM), without producing excessive myotendinous stress¹.

Based on the flexibility relation and joint ROM^1,4,5, clinical tests are applied to evaluate the presence of limitations in the ROM. These tests are characterized by movements that increase the distance between the origin and the muscular insertion, literally stretching the muscle in question with the objective to test it⁵.

The hamstring muscles (HM), group composed by the semi-tendinous, semi-membranous and biceps femoralis muscles, form a large muscular mass that is directly involved in the movements of the hip and knee joints^6,7. This group performs an important role in the antero-posterior pelvic tilt, indirectly affecting lumbar lordosis. Therefore, altered flexibility of the HM may produce significant postural deviations and affect the functionality of the hip joint and lumbar spine^6,8. Thus, the execution of flexibility tests becomes necessary in the process of assessment and intervention in physical therapy.

Clinically, HM length may be measured indirectly by having as possible reference the movement of the hip joint⁹. Thus, while observing diminished hip ROM , associated to the evidence of absence of neurological symptoms, it is often considered as a measurement of muscle flexibility¹⁰. Several tests are clinically used to assess HM flexibility, among them the sit-and-reach¹¹ and active or passive extension of the knee^9,12. Two tests widely used, and that were not still submitted to comparisons are the Straight Leg Raise Test (SLR)^9,13-16 and the Fingertip-to-Floor Test (FTF)^4,17,18.

An essential aspect to be considered for the choice of a clinical test is the reliability of the measures¹⁹, and this may be defined as the consistency of measurements of certain phenomenon, that is, the extent to which the measures are repeated by people and instruments leading to similar results²⁰. The fingertip-to-floor test has showed itself reliable and can be considered a valid measurement of the hamstring flexibility¹⁷. Furthermore, Tully and Stillman¹⁸ suggest it as a valid measurement of this muscle's flexibility. In the same way, the straight leg raise test can be considered as a measurement of the flexibility of the hamstrings⁹, possibly possessing clinical validity³.

An analysis technique that has been used on the last years is photogrammetry²¹. Defined as measurement of certain phenomenon by means of photography. This technique provides innumerous advantages, such as usefulness, low cost, precision²² and non-invasive characteristics²¹. Furthermore, its use should be planned in a way to prevent mistakes²². Thus, establishing the reliability of this measure becomes necessary.

Assuming that the practice of the physical therapist should be scientifically based, which, among other aspects, involves the quality and the reproducibility of the measures used in evaluation procedures, it becomes relevant to assess the reliability of two tests widely employed in the measurement of the HM's flexibility. Therefore, the objectives of the present study were to compare the results of the FTF and SLR tests by means of photogrammetry; to verify the agreement between the findings of the hip angle between both tests, and to assess intra- and inter-observer reliability of the photogrammetric analysis procedure.

MATERIALS AND METHODS

Subjects

Thirty-five healthy male individuals participated in this study (mean age 23 years ± 3.4; mean height 170 cm ± 4; and mean weight 68 kg ± 11). All subjects practiced physical activities twice or three times a week. The sample was composed of students recruited at the University, and, in order to be included, they were submitted to a postural assessment and were selected according to the Inclusion criteria: age between 18 and 35 years and height between 1.65 and 1.75 m, and according to the Exclusion criteria: Trauma history and any kind of musculoskeletal surgery in the lower limbs or spine; presence of postural asymmetries; lumbar pain on the last six months and neurological disorders, such as diagnosed disc herniation.

The individuals that fulfilled the criteria were clarified about the objectives of the research and the procedures, and were invited to participate in the study. They signed a free and clarified consent term according to Resolution 196 of the CNS and approved by the Ethics Committee of Federal University of São Carlos (report nº 059/04).

Clinical assessment of muscle flexibility

Participants were subjected to the SLR (Figure 1) and the FTF (Figure 2) tests, assessed by the same examiner. Both provide dichotomic results, that is, subjects' distribution in normal or reduced flexibility.

The following bone markers were placed on the skin: Femoral Greater Throcanter (FGT), Lateral Maleolus (LM), Femoral Lateral Epicondilus (FLE), Anterior Superior (ASIS) and Posterior Superior (PSIS) Iliac Spines, and spinal processes of T12 and C7 (Figures 1 and 2). The lines connecting PSIS-T12 and T12-C7 represented the thoracolumbar angle¹⁵ (TLº) (Figure 2). Hip angle (Hº) was based on Kapandji⁷ and measured as the angle between the ASIS-FGT and FLE-FGT lines. Knee angle⁷ (Kº) was represented by the angle between the LM-FLE and FGT-FLE, and the tibia-tarsus angle⁷ (TTº), was calculated as the crossing of the line parallel to the feet's sole with the tibia axis (FLE-LM) (Figure 2). Hip's rotation (Rº) was represented as the crossing between the horizontal line and the ASIS-FGT, and measured from subtraction of the angle during resting posture with the angle on the elevated lower limbs. Leg angle (Lº) was determined as the angle between absolute horizontal and leg's line (FGT-LM) (Figure 1).

Procedures were directed to obtain quality pictures²³. A digital MAVICA photographic camera and a tripod were placed at 2.75 m of the test area, directed at the height of the hip. The optical axis of the camera was perpendicular to the sagittal plane of the individuals.

Initially, a Thomas⁵ test was applied in order to verify the flexibility of the iliopsoas muscle. In case the result indicated a reduction in flexibility of this muscle, a pillow was placed under the thigh of the counterlateral limb, with the objective to keep a slight flexion of the hip. This procedure facilitated the support of the lumbar spine during the test application, reducing possible influences from this segment in the test results. Afterwards, the HM flexibility measuring tests were applied. The participants did not perform any kind of warm-up or stretching before each test's administration.

Straight leg raise test

The test was applied passively, based on Kendall et al.⁵ and Gajdosik et al.¹⁵. The subjects were classified into two groups according to the angle between the long axis of the leg and the horizontal line. Thus, individuals that obtained values equal or greater than 65º were classified as with normal flexibility, while the subjects that obtained values lower than 65º were classified with reduced flexibility. Precautions were taken during the test's execution: counterlateral thigh fixation of all individuals with a tape, instructions for the subject to relax and standardization of a slow raising velocity. Final leg raising position was photographed, that is, the moment in which the subjects reported a muscular tension sensation that caused great discomfort in the HM. Measured angles were the leg segment in relation to the horizontal, hip and hip rotation, which must be monitored to prevent over-estimation of results^17,24.

Fingertip-to floor

The test was applied according to Magnusson et al. ⁴. The subjects were asked to keep the knees completely extended, and, from then on, to flex the trunk towards the floor, with head and arms relaxed. Final flexion position was indicated by a sensation of muscular tension that caused great HM discomfort and, in this moment, pictures were taken. Individuals that could reach a distance smaller than 10 cm in relation to the ground were classified as with normal flexibility, and the ones who stayed beyond the distance of 10 cm from the ground were classified as with reduced flexibility. Fingertips distance from the ground (in cm) was measured based a known linear measure, placed on the same visual field from the individuals. Measured angles were the thoracolumbar, hip, knee and ankle. Only left side measurements were considered, and care was taken to remind the subjects to keep their knees extended.

Reliability procedures

In order to assess measurement reliability it was planned a parallel study with a transversal design, with two examiners. The reliability of the photogrammetric analysis procedure was assessed by means of 30 pictures selected randomly, for evaluation of the angles of the hip, thoracolumbar, leg, knee, and ankle, totalizing thirty measurements for each angle. Each examiner made analyses at two different moments, separated by a 10-day interval between them. AutoCAD^® 2000 software was used for angle photogrammetric analyses.

Statistical analysis

SPSS version 10.0 software was used and the results were analyzed adopting a 5% significance and confidence interval (CI) of 95%. Data relative to age, height, weight and angular measures were presented in relation to the mean and standard deviation.

Regarding the leg raise test, paired t-test was applied to verify differences between the elevation angles of right and left leg. In case of lack of significant difference, the mean between the right and left angles would be calculated. This value was used as reference for each subject's flexibility classification. From the results, subjects were classified into two groups: normal and reduced flexibility. Angular measurements of the thoracolumbar, hip, knee, ankle, leg elevation and hip rotation segments between both groups were compared for differences using the t-student's test. McNemar's test for dichotomous nominal variables was applied for comparing distribution of subjects according to the classification on both flexibility tests.

For intra- and inter-examiners reliability of the photogrammetric analysis procedures and agreement of the hip's angle between the tests, Intra-Classes Correlation Coefficient (ICC one-way random) and the agreement limits of Bland and Altman²⁵ were employed.

RESULTS

The result of the photogrammetric analysis for the Fingertip-to-floor test has shown that only the hip's angle was significantly different (P = 0.004) between the flexibility groups (106º ± 14 and 94º ± 13, respectively, for the groups with reduced and normal flexibility). The group with reduced flexibility presented a smaller hip flexion in comparison to the group with normal flexibility.

Regarding the leg raise test, only the leg and hip elevation angles presented significant differences between the flexibility groups (P = 0.001). Similarly, subjects with reduced flexibility (hip: 107º ± 10 and leg elevation: 54º ± 7) presented lower hip flexion and lower leg raising values in relation to the individuals with normal flexibility (hip: 88º ± 9 and leg elevation: 72º ± 6).

Comparison of the results between the SLR and FTF tests is presented in Table 1, according to the classification criteria. A significant difference of 22.8% (P < 0.02) was found in the distribution of flexibility defined by both tests. The straight leg raise test has identified a grater number of subjects with flexibility reduction than the fingertip-to-floor test.

The results Leg elevation on the flexibility groups, corrected with reference to hip's rotation, have shown that, in average, subjects with normal flexibility have reached 53º of leg elevation. On the other hand, subjects with reduced flexibility have presented in average 33º of elevation. Monitoring was relevant, as it has confirmed that the leg angle values used for flexibility classification were overestimated because of influence of the hip rotation.

Table 2 presents the ICC values and mean difference (± SD) for intra and inter-examiners reliability measures of the photogrammetric analysis procedure employed at the study. All analyzed angles presented good reproducibility, both intra and inter-observers.

Comparison of the hip's angular values of each test presented a good agreement score (ICC= 0.89, CI= 0.78-0.94). The mean difference between both tests was 0.85º ± 6.8º (CI= -1.6 3.3) and the agreements limits between 14.2 to -12.5 (mean ± 2SD).

DISCUSSION

The 22.8% significant difference found in the comparison of the tests indicates that the flexibility measurement based on the distance parameters from fingers to the floor and leg angle in relation to the horizontal line were responsible for different classifications of the assessed subjects. In fact, distance of the fingers to the floor may be influenced by anthropometrical characteristics, such as arm size and spinal range of motion¹¹. In the same way, the resulting leg angle measurement may have been influenced by the hip rotation^24,26.

On the other hand, good agreement of the hip angle measurements indicates that the tests may provide similar and consistent classifications, if the hip joint is used as reference. In fact, significant differences on the hip joint between both groups, on both flexibility tests, point out to HM shortening as a limiting factor of motion of this joint^15,17,18. Other studies support the relationship between clinical measurements and muscular stiffness. In this case, shortened HM may be responsible for changes in stretching tolerance^4,10, and constitutes an important influence in the hip ROM²⁷.

Hip angle could be the parameter for these flexibility tests based on the direct relation of the HM with the pelvis and hip's functionality^6,8. The difference found between the tests regarding flexibility distributions, supported by a good agreement, suggests a viability of studies to establish normative values for the hip angle, on both the FTF and SLR tests, which could make them more specific and comparable between one another.

Thoracolumbar angle was analyzed with the intention to detect possible compensation in this region, in response to the hip ROM restriction. As opposed to Gajdosik¹⁵, the findings did not present significant differences, despite the fact that the subjects with reduced flexibility presented higher levels of flexion (46º ± 5) when compared to normal individuals (44º ± 6). Although the angle was based in a Gajdosik¹⁵ study, maybe the inclusion of PSIS could have occasioned the lack of significance. Findings related to knee and ankle angles were positive, because both were used to monitor the position of the subjects according to the directions given. Lack of significant difference between the groups suggests that the individuals kept their knees extended, did not compensate the motion in the ankle's joint and avoided problems in the interpretation of the distance from the fingertips to the floor.

If the application of different tests in the measurement of the same parameter leads to comparable and consistent results, the quality of communication among different professionals increases, providing scientific support to clinical practice¹⁹. On the other hand, the difficulty in the comparisons of the findings in literature shows the variety of definitions and angles used. In addition, the different ways in which tests are applied confirm the problems reported by Dixon and Keating¹⁶.

The photogrammetric analysis procedure was shown to be practical and useful. However, despite the establishment of the tests' reliability, the findings must be seen with caution. The method's application, in association with the use of surface bone markers, may be prone to measurement errors due to the movement of the markers on the skin²⁸. Methodological considerations relative to the establishment of reliability and standardization of markers placement are necessary in the future, in order to offer even more reliable assessment options for clinical practice. Similarly, data obtained with hip rotation monitoring during the leg raise test effectively demonstrated overestimation of the results and reasserted the assumption that this movement may interfere with the flexibility assessment^24,26. However, these results should also be accepted with caution, since skin movement artifacts may occur, mainly in markers placed at the throcanteric region, during thigh movement²⁸.

Questionings regarding the validity of the clinical tests, despite difficulties in establishing them¹⁹, are always important. The widespread definition of validity as an evidence that a given test measures what it proposes to measure¹⁹, raises relevant discussions that may justify the HM's influence on the hip function and its consequent assessment. There are several factors than may limit the ROM of a joint (joint capsule, bone contact, ligaments, soft tissues). Among them, myotendinous tissue stretching is the most common factor²⁹.

The length-tension relationships that dictate the efficiency of a muscle refer to the position of the involved joints. Consensually, it is considered that HM are more efficient hip extensors when the knee joint is extended⁷. Both tests used in the present study were applied in such a way to reproduce the action of the HM as hip extensors, placing this muscular group in its efficient position. Both tests used are widely recommended as stretching exercise^1,8 and as a test for flexibility assessment of the posterior thigh muscles^9,13-18. Considering that stretching exercises are applied in the same way and that such exercises are the basis of kinesiotherapy teaching, it seems acceptable that the use of clinical tests that reproduce such movements may be considered valid for this finality.

CONCLUSIONS

The two muscular flexibility tests assessed in this study presented differences in the flexibility classification between the individuals. However, when the hip angle was considered on the leg raise test, there was an agreement between the results of both tests. The photogrammetric analysis procedures were reproducible both for intra- and for inter-examiners, constituting a useful tool of analysis for the tests in question, as long as cautions are taken for possible markers movement errors.

REFERENCES

Received: 09/06/2006

Revised: 27/11/2006

Accepted: 21/12/2006

• 1. Alter MJ. Science of flexibility. 2Ş ed. Champaign: Human Kinetics; 1996.
• 2. Göeken LN, Hof L. Instrumental straight-leg raising: Results in healthy subjects. Arch Phys Med Rehabil. 1993;74:194-203.
• 3. Gajdosik RL. Passive extensibility of skeletal muscle: review of the literature with clinical implications. Clin Biomech. 2001; 16:87-101.
• 4. Magnusson SP, Simonsen EB, Aagaard P, Boesen J, Johannsen F, Kjaer M. Determinants of musculoskeletal flexibility: viscoelastic properties, cross-sectional area, EMG and stretch tolerance. Scand J Med Sci Sports. 1997;7:195-202.
• 5. Kendall FP, McCreary EK, Provance PG. Músculos: Provas e funções. 4Ş ed. São Paulo: Manole; 1995.
• 6. Palastanga N, Field D, Soames R. Anatomia e movimento humano - Estrutura e função. 3Ş ed. São Paulo: Manole; 2000.
• 7. Kapandji AI. Fisiologia articular. 5Ş ed. São Paulo: Panamericana; 2000.
• 8. Hamill J, Knutzen KM. Bases biomecânicas do movimento humano. 1Ş ed. São Paulo: Manole; 1999.
• 9. Gajdosik RL, Rieck MA, Sullivan DK, Wightman SE. Com-parison of four clinical tests for assessing hamstring muscle length. J Orthop Sports Phys Ther. 1993;18(5):614-8.
• 10. Halberstma JPK, Göeken LNH, Groothoff JW, Eisma WH. Extensibility and stiffness of the hamstrings in patients with nonspecific low back pain. Arch Phys Med Rehabil. 2001; 82:232-8.
• 11. Cornbleet SL, Woolsey NB. Assessment of hamstring muscle length in school-aged children using the sit-and-reach test and the inclinometer measure of hip joint angle. Phys Ther. 1996;76(8):850-5.
• 12. Norris CM, Matthews M. Inter-tester reliability of a self-monitored active knee extension test. J Bodywork Mov Ther. 2005;9:256-9.
• 13. Polachini LO, Fuzasaki L, Tamaso M, Tellini GG, Masieiro D. Estudo comparativo entre três métodos de avaliação do encurtamento de musculatura posterior da coxa. Rev Bras Fisiot. 2005;9(2):187-93.
• 14. Cameron DM, Bohannon RW, Owen SV. Influence of hip position on measurements of the straight leg raise test. J Orthop Sports Phys Ther. 1994;19(3):168-72.
• 15. Gajdosik RL, Albert CR, Mitman JJ. Influence of hamstring length on the standing position and flexion range of motion of the pelvic angle, lumbar angle and thoracic angle. J Orthop Sports Phys Ther. 1994;20(4):213-9.
• 16. Dixon JK, Keating JL. Variability in straight leg raise measu-rements: Review. Physiotherapy. 2000;86(7):361-70.
• 17. Kippers V, Parker AW. Toe-touch test. A measure of its validity. Phys Ther. 1987;67(11):1680-4.
• 18. Tully EA, Stillman BC. Computer-aided video analysis of vertebrofemoral motion during toe touching in healthy subjects. Arch Phys Med Rehabil. 1997;78:759-66.
• 19. Rothstein JM. Measurement and clinical practice: theory and application. In Rothstein JM, editor. Measurement in Physical Therapy. New York: Churchill Livingstone; 1985. p. 1-46.
• 20. Atkinson G, Nevill AM. Statistical methods for assessing measurement error (reliability) in variables relevant to sports medicine. Sports Med. 1998;26(4):217-38.
• 21. Mitchell HL, Newton I. Medical photogrammetric measurement: Overview and prospects. ISPRS J Photogram Rem Sens. 2002; 56:286-94.
• 22. Young S. Research for medical photographers: Photographic measurement. J Audiov Media Med. 2002;25(3):94-8.
• 23. Watson AWS. Procedure for the production of high quality photographs suitable for recording and evaluation of posture. Rev Fisio USP. 1998;5(1):20-6.
• 24. Bohannon RW. Cinematographic analysis of the passive straight-leg-raising test for hamstring muscle length. Phys Ther. 1982; 62(9):1269-74.
• 25. Bland JM, Altman DG. Statistical methods for assessing agree-ment between two methods of clinical measurement. Lancet. 1986;1:307-10.
• 26. Bohannon R, Gajdosik R, LeVeau BF. Contribution of pelvic and lower limb motion to increases in the angle of passive straight leg raising. Phys Ther. 1985;65(4):474-6.
• 27. Li Y, McClure PW, Pratt N. The effect of hamstring muscle stretching on standing posture and on lumbar and hip motion during forward bending. Phys Ther. 1996;76(8):836-49.
• 28. Stagni R, Fantozzi S, Cappello A, Leardini A. Quantification of soft tissue artifact in motion analysis by combining 3D fluoroscopy and stereophotogrammetry: a study on two subjects. Clin Biomech. 2005;20:320-9.
• 29. Abernethy B, Kippers V, Mackinnon LT, Neal RJ, Hanrahan S. The biophysical foundations of human movement. Champaign: Human Kinetics; 1997.

Publication Dates

• Publication in this collection
  27 Feb 2008
• Date of issue
  Apr 2007

History

• Accepted
  21 Dec 2006
• Received
  09 June 2006