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Nakaizumi D1,2, Asai H3, Inaoka PT3
1Kanazawa Red Cross Hospital, Rehabilitation, Kanazawa, Japan, 2Kanazawa University, Division of Health Sciences, Graduate School of Medical Sciences, Kanazawa, Japan, 3Kanazawa University, Physical Therapy, Kanazawa, Japan
Background: Hamstring muscles are composed of the biceps femoris long head (BFlh), biceps femoris short head (BFsh), the semimembranosus (SM) and, the semitendinosus (ST). The BFlh and the SM are unipennate muscles and they are the most commonly injured component in sprinters and dancers respectively. BFsh and ST are fusiform muscles. The muscle architecture and the strain predominance differences in those muscles can also suggest differences in morphological changes of each muscle during hamstring extension. Magnetic Resonance Imaging (MRI) is generally considered the most accurate non-invasive modality to assess hamstring muscles morphology, however regular MRI scanners do not allow the scanning in hamstring muscles stretching position. This study analyzed the images scanned by a vertical open MRI which allowed the imaging of the hamstring muscles group during rest and stretching.
Purpose: To investigate the changes in cross-sectional area of each component of the hamstring muscles at rest and at stretching position.
Methods: Fifteen healthy young males (age 22.0± 1.3) volunteered for this study. A gravity MRI, which open shape allows the body scanning in varied positions, (0.4T, Hitachi Healthcare) was used to scan T1- weighted images (Scan time; 3min 20s) of right thigh. Maximum cross-sectional area of each muscle of the hamstring muscles during rest and stretching were measured using ImageJ from the obtained images. The imaging were taken
1) at rest: on supine, hip and knee flexed at 90°,
2) at stretching position: on supine, hip flexed at 90° and the knee extended at the maximal range of motion without pain.
The rate of change of the maximum cross-sectional area of each muscle relative to rest was calculated from the following formula. Rate of change = [(maximum muscle cross-sectional area at rest - maximum muscle cross-sectional area at stretching) / maximum muscle cross-sectional area at rest] × 100. Bonferroni correction was applied to investigate the difference in the rate of change of the maximum cross-sectional area per muscle. The significance level was set at 5%.
Results: The rate of change of maximum cross-sectional area of each muscle was 6.7 (3.7-8.4) % for BFsh, 8.4 (5.7-10.5) % for BFlh, 11.2 (5.4-14.0) % for ST, and 2.0 (1.7-3.0) % for SM. The rate of change of SM maximum cross-sectional area was significantly smaller than other three muscles, and no significant differences were found between those three muscles data.
Conclusion(s): The results of this study revealed that the rate of change of the maximum cross-sectional area of each hamstring muscles during stretching was smaller in the SM than in the other three muscles, and this result can be due to SM lower elasticity, what suggest a limiting factor for hamstrings extensibility. However other methods have to be introduced to confirm this hypothesis.
Implications: The investigation on morphological changes of individual muscle of hamstring muscles can clarify the strain injury mechanisms and the differences in the injury risks for each component, what can lead to a more effective Physical Therapy program for hamstring muscles strain recovery and prevention.
Keywords: hamstring, MRI, cross-sectional area
Funding acknowledgements: There is no financial support for this study.
Purpose: To investigate the changes in cross-sectional area of each component of the hamstring muscles at rest and at stretching position.
Methods: Fifteen healthy young males (age 22.0± 1.3) volunteered for this study. A gravity MRI, which open shape allows the body scanning in varied positions, (0.4T, Hitachi Healthcare) was used to scan T1- weighted images (Scan time; 3min 20s) of right thigh. Maximum cross-sectional area of each muscle of the hamstring muscles during rest and stretching were measured using ImageJ from the obtained images. The imaging were taken
1) at rest: on supine, hip and knee flexed at 90°,
2) at stretching position: on supine, hip flexed at 90° and the knee extended at the maximal range of motion without pain.
The rate of change of the maximum cross-sectional area of each muscle relative to rest was calculated from the following formula. Rate of change = [(maximum muscle cross-sectional area at rest - maximum muscle cross-sectional area at stretching) / maximum muscle cross-sectional area at rest] × 100. Bonferroni correction was applied to investigate the difference in the rate of change of the maximum cross-sectional area per muscle. The significance level was set at 5%.
Results: The rate of change of maximum cross-sectional area of each muscle was 6.7 (3.7-8.4) % for BFsh, 8.4 (5.7-10.5) % for BFlh, 11.2 (5.4-14.0) % for ST, and 2.0 (1.7-3.0) % for SM. The rate of change of SM maximum cross-sectional area was significantly smaller than other three muscles, and no significant differences were found between those three muscles data.
Conclusion(s): The results of this study revealed that the rate of change of the maximum cross-sectional area of each hamstring muscles during stretching was smaller in the SM than in the other three muscles, and this result can be due to SM lower elasticity, what suggest a limiting factor for hamstrings extensibility. However other methods have to be introduced to confirm this hypothesis.
Implications: The investigation on morphological changes of individual muscle of hamstring muscles can clarify the strain injury mechanisms and the differences in the injury risks for each component, what can lead to a more effective Physical Therapy program for hamstring muscles strain recovery and prevention.
Keywords: hamstring, MRI, cross-sectional area
Funding acknowledgements: There is no financial support for this study.
Topic: Outcome measurement; Musculoskeletal: lower limb; Human movement analysis
Ethics approval required: Yes
Institution: Kanazawa University
Ethics committee: Institutional ethics committee of Kanazawa University
Ethics number: 797-1
All authors, affiliations and abstracts have been published as submitted.
