ISSN : 2146-3123
E-ISSN : 2146-3131

What are the cutoff values for the diagnosis of hamstring shortness and related factors that affect their results?
Muhammed Şeref Yıldırım1, Filiz Tuna1, Derya Demirbağ Kabayel2, Necdet Süt3
1Department of Physical Therapy and Rehabilitation, Trakya University School of Health Science, Edirne, Turkey
2Department of Physical Medicine and Rehabilitation, Trakya University School of Medicine, Edirne, Turkey
3Department of Biostatistics, Trakya University School of Medicine, Edirne, Turkey
DOI : 10.4274/balkanmedj.2017.1517

Background: Decreased hamstring flexibility is associated with many pathological conditions. For this reason, hamstrings are one of the most frequently evaluated muscle groups for flexibility in the lower extremity. Muscle flexibility is evaluated indirectly by measuring adjacent joint range of motion. Passive and active knee extension angle values are used as an indirect indicator of hamstring flexibility. But the results of the active knee extension test are claimed to be influenced by subject’s quadriceps strength. The passive knee extension test is a modified version of the active knee extension test which eliminates the effect of quadriceps strength on flexibility results. 
Aims: In this research, our goal was to establish the normative and cut-off values of passive and active knee extension angles for healthy young adults, and determine associated factors. We also aimed to reveal whether the values of the active knee extension results were affected by quadriceps strength. 
Study Design: Cross-sectional study 
Methods: A hundred twenty-three volunteer University students, ages 18–24 years, who met inclusion criteria were involved in the research. Passive and active knee extension assessments of subjects were performed. Subsequently, on the other day, both knee extensor concentric muscle strength of the participants was measured in isokinetic system. The knee extension angles and knee extensor strength were recorded as averages of the right and left sides. 
Results: According to our data, passive knee extension angle of 17.1º±9.1º and 9.8º±5.7º; active knee extension angle of 17.8º±9.1º and 13.4º±6º, in men and women, respectively, described as normative values. The cutoff values for the diagnosis of hamstring shortness; passive knee extension angle was >32.2° for male and >19.2° for female, active knee extension angle was >33.0° for male and >23.4° for female. There was a significant positive correlation between knee extension angles and isokinetic knee extensor muscle strength in all participants. But when male and female participants were evaluated separately, there was no significant relationship between the above-mentioned parameters. 
Conclusion: The cut off values we have set to identify those with hamstring shortness will be useful for future research. In our study, we found that knee extension angle and hamstring flexibility are not affected by dominance. In addition, active knee extension test results do not decrease due to quadriceps strength increase.

Keywords : Articular, knee joint, lower extremity, muscle strength, range of motion, quadriceps muscle, young adult
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