Award Date

5-2015

Degree Type

Thesis

Degree Name

Doctor of Physical Therapy (DPT)

Department

Physical Therapy

First Committee Member

Kai Yu Ho

Second Committee Member

Szu-Ping Lee

Third Committee Member

Merrill Landers

Fourth Committee Member

Kathryn Hausbeck Korgan

Number of Pages

37

Abstract

Background and Purpose: Research has shown that the risk of low back dysfunctions in runners is related to the increased mileage of distance running. Repetitive shock loading of the spinal structures during running has been indicated as one of the important biomechanical mechanisms underlying such injury. Acute changes in foot strike pattern, like those seen during minimalist style running, have been shown to lead to modifications in lumbar range of motion. Minimalist style running could lead to changes in lumbar biomechanics and muscle activation, potentially reducing the loading on the musculoskeletal structures of the lower back. However, the long term effects of minimalist style running on lumbar biomechanics have not been evaluated. The purpose of this study was to investigate the effects a 4-week training program aimed at transitioning recreational runners to minimalist style footwear would have on lower back kinematics and lumbar paraspinal muscle activation.

Subjects: 17 volunteers between the ages of 18-45 years who were habitually shod runners and averaged running 10-50 km per week participated in the study. Data from 15 volunteers was used in the analysis of the biomechanics. Inclusion and exclusion criteria were used to determine the appropriateness of each volunteer for this study.

Methods: Subjects participated in three data collection sessions at the beginning, during (2-week), and at the end of a 4-week training program. The training consists of progressively increasing the distance each runner ran in the minimalist shoes up to 30-50% of their regular running distance while maintaining the overall distance (minimalist + normal shoes) comparable to before training. Running trials were collected with the subject wearing their normal running shoes. Subjects were asked to run at a prescribed speed (11.2 km/h), and a blinded self-selected speed. During running, kinematics of the lower back in the sagittal plane was recorded using an electro-goniometer. Surface EMG was used to monitor the activation of the lower back (L3 level) paraspinal muscles. Data collected during 10 stance phases were averaged and used for analysis. One-way repeated measures ANOVA tests were used to analyze the effect of training on lumbar kinematics and lumbar paraspinal muscle activation.

Results: For the 11.2 km/h running speed, statistically significant differences were found in mean lower back posture (PRE = 1.9 ± 15.3 degrees, MID = 0.4 ± 13.0 degrees, POST = -6.0 ± 13.3 degrees, p = 0.001) and contralateral lumbar paraspinal muscle activation (PRE = 47.0 ± 34.0%, MID = 24.9 ± 8.2%, POST = 29.4 ± 11.3%, p = 0.039) after training. For the self-selected running speed, statistically significant differences were found in mean lower back posture (PRE = 2.3 ± 15.5 degrees, MID = 0.9 ± 13.9 degrees, POST = -5.7 ± 14.2 degrees, p = 0.002) and contralateral lumbar paraspinal muscle activation (PRE = 41.6 ± 28.6%, MID = 23.4 ± 6.2%, POST = 30.3 ± 11.6%, p = 0.047) after training. During both speeds, lower back posture became more extended and contralateral lumbar paraspinal muscle activation decreased. No significant differences were noted in overall lower back range of motion or ipsilateral paraspinal muscle activation over the training period at either speed.

Conclusions: Including minimalist running shoes and barefoot exercises into a runners’ training regime can alter the lumbar spinal kinematics and muscle activation. Specifically the runners adapted a more extended lumbar posture and reduced the lumbar paraspinal muscle activation after training. This effect carried over to shod running.

Keywords

Backache; Long-distance runners; Physical therapy; Runners (Sports); Running injuries

Disciplines

Applied Statistics | Physical Therapy | Rehabilitation and Therapy | Statistics and Probability

Language

English


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