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Okamura K1, Kanai S1, Tanaka S1, Fukuda K2, Oki S1
1Prefectural University of Hiroshima, Department of Physical Therapy, Faculty of Health and Welfare, Hiroshima, Japan, 2Innoshima Ishikai Hospital, Department of Rehabilitation, Hiroshima, Japan
Background: The intrinsic foot muscles (IFMs) have the capacity to support the medial longitudinal arch (MLA). Although exercise to strengthen the IFMs is often prescribed to correct static foot alignment, the effects of IFM exercise on MLA kinematics during dynamic activities are unclear. To confirm this research question would be valuable for preventing and/or treating lower extremity overuse injuries related to flat-foot alignment, such as plantar fasciitis and medial tibial stress syndrome.
Purpose: The purpose of this study was to determine the effects of IFM exercise on MLA deformation during gait.
Methods: Twenty flat-footed subjects (3 males, 17 females; mean age = 20.0 ± 1.3 years; BMI = 20.4 ± 1.9 kg/m2) participated in this study. Flat-footedness was defined as a score of > 5 points on a 6-item foot posture index. Following randomization, subjects were randomly assigned to an intervention group or a control group. In the intervention group, subjects performed progressive IFM exercise three times per week for 8 weeks. An investigator (KF) met with each subject once per week to assess whether the subjects performed the IFM exercise exactly and to modify the progression of the exercise. Subjects in the control group did not receive any intervention. Using a 3D motion analysis system, the minimum MLA height during the stance phase of gait and the time at which the MLA height reached its minimum value were assessed before and after intervention. In each parameter, the amount of change from before the intervention were compared. All measurements were performed by an investigator (KO) blinded to the allocation of the participants.
This study was approved by the Ethics Committee of the Prefectural University of Hiroshima, and written informed consent was obtained from all subjects. The study protocol was registered at the University Hospital Medical Information Network Clinical Trials Registry (UMIN000032761).
Results: The intervention group demonstrated significantly shortened time for the MLA height to reach its minimum value (mean difference = 4.6% stance phase duration, p 0.01). There was no significant group difference in the change of minimum MLA height.
Conclusion(s): An 8-week IFM exercise intervention changed the temporal parameter of MLA kinematics during gait. Because the IFMs have the capacity to support the MLA, the shortened time for the MLA height to reach its minimum value indicates that MLA deformation during gait was reduced by the IFM exercise. It is possible that the absence of an increase in minimum MLA height could be caused by errors in marker placement.
Implications: IFM exercise may be an effective method to prevent and/or treat lower extremity overuse injuries related to flat-foot alignment because these injuries are attributed to overload during dynamic activities. Future studies should be performed during activities with higher intensity, such as running.
Keywords: intrinsic foot muscles, strengthening exercise, randomized controlled trial
Funding acknowledgements: This work was supported by JSPS KAKENHI [Grant Number JP17K01524].
Purpose: The purpose of this study was to determine the effects of IFM exercise on MLA deformation during gait.
Methods: Twenty flat-footed subjects (3 males, 17 females; mean age = 20.0 ± 1.3 years; BMI = 20.4 ± 1.9 kg/m2) participated in this study. Flat-footedness was defined as a score of > 5 points on a 6-item foot posture index. Following randomization, subjects were randomly assigned to an intervention group or a control group. In the intervention group, subjects performed progressive IFM exercise three times per week for 8 weeks. An investigator (KF) met with each subject once per week to assess whether the subjects performed the IFM exercise exactly and to modify the progression of the exercise. Subjects in the control group did not receive any intervention. Using a 3D motion analysis system, the minimum MLA height during the stance phase of gait and the time at which the MLA height reached its minimum value were assessed before and after intervention. In each parameter, the amount of change from before the intervention were compared. All measurements were performed by an investigator (KO) blinded to the allocation of the participants.
This study was approved by the Ethics Committee of the Prefectural University of Hiroshima, and written informed consent was obtained from all subjects. The study protocol was registered at the University Hospital Medical Information Network Clinical Trials Registry (UMIN000032761).
Results: The intervention group demonstrated significantly shortened time for the MLA height to reach its minimum value (mean difference = 4.6% stance phase duration, p 0.01). There was no significant group difference in the change of minimum MLA height.
Conclusion(s): An 8-week IFM exercise intervention changed the temporal parameter of MLA kinematics during gait. Because the IFMs have the capacity to support the MLA, the shortened time for the MLA height to reach its minimum value indicates that MLA deformation during gait was reduced by the IFM exercise. It is possible that the absence of an increase in minimum MLA height could be caused by errors in marker placement.
Implications: IFM exercise may be an effective method to prevent and/or treat lower extremity overuse injuries related to flat-foot alignment because these injuries are attributed to overload during dynamic activities. Future studies should be performed during activities with higher intensity, such as running.
Keywords: intrinsic foot muscles, strengthening exercise, randomized controlled trial
Funding acknowledgements: This work was supported by JSPS KAKENHI [Grant Number JP17K01524].
Topic: Musculoskeletal: lower limb; Sport & sports injuries; Musculoskeletal
Ethics approval required: Yes
Institution: Prefectural University of Hiroshima
Ethics committee: Ethics Committee of the Prefectural University of Hiroshima
Ethics number: No. 18MH011
All authors, affiliations and abstracts have been published as submitted.
