Elsevier

Physical Therapy in Sport

Volume 29, January 2018, Pages 101-107
Physical Therapy in Sport

Original Research
Adaptations of lumbar biomechanics after four weeks of running training with minimalist footwear and technique guidance: Implications for running-related lower back pain

https://doi.org/10.1016/j.ptsp.2016.11.004Get rights and content

Highlights

  • A 4-week minimalist style running training was conducted in recreational runners.

  • After training, runners exhibited reduced lumbar extension angle during stance.

  • After training, runners exhibited reduced lumbar paraspinal muscle activation.

  • Changes in lumbar kinematics and muscle activation transferred to normal running.

  • No runner reported any adverse effect during the 4-week training.

Abstract

Objectives

To investigate the changes in lumbar kinematic and paraspinal muscle activation before, during, and after a 4-week minimalist running training.

Setting

University research laboratory.

Participants

Seventeen habitually shod recreational runners who run 10–50 km per week.

Main outcome measures

During stance phases of running, sagittal lumbar kinematics was recorded using an electrogoniometer, and activities of the lumbar paraspinal muscles were assessed by electromyography. Runners were asked to run at a prescribed speed (3.1 m/s) and a self-selected speed.

Results

For the 3.1 m/s running speed, significant differences were found in the calculated mean lumbar posture (p = 0.001) during the stance phase, including a more extended lumbar posture after minimalist running training. A significant reduction in the contralateral lumbar paraspinal muscle activation was also observed (p = 0.039). For the preferred running speed, similar findings of a more extended lumbar posture (p = 0.002) and a reduction in contralateral lumbar paraspinal muscle activation (p = 0.047) were observed.

Conclusion

A 4-week minimalist running training program produced significant changes in lumbar biomechanics during running. Specifically, runners adopted a more extended lumbar posture and reduced lumbar paraspinal muscle activation. These findings may have clinical implications for treating individuals with running-related lower back pain.

Introduction

Running is one of the fastest expanding participation segments of sports and exercise. In the United States, it was estimated that 19 million people ran more than 100 times in 2011, a 9.3% increase from 2010 (NSGA., 2011). The number of marathon finishers has increased by more than 75.5% in the last decade (Lamppa, 2014). However, the drastic increase in the popularity of running is accompanied by an increase in the number of injured runners. Nielsen et al. reported that over the course of 1 year, 23.1% of novice runners sustained running-related injuries to the lower extremity or back (Nielsen et al., 2014). According to a 2013 survey of running event participants, 10.1% of the runners reported experiencing a running-related lower back injury within the last 12 months (Yoder, 2013). Walter et al. showed that injuries pertaining to the back and pelvis account for approximately 25–35% of all running-related injuries (Walter, Hart, McIntosh, & Sutton, 1989). In addition, preliminary data showed that running more than 20 miles per week can increase the odds of persistent lower back pain (LBP) by five-fold (Gonzalez, Akuthota, Min, & Sullivan, 2006).

The repetitive impact loading during running is a possible mechanism for developing lower back structural changes and pain in runners (Cavanagh and Lafortune, 1980, Dimitriadis et al., 2011, Hamill et al., 2014, Hamill et al., 2009). Dimitriadis et al. reported transient disc height reduction following 1 h of running measured by MRI in a static posture. Furthermore, the disc height reduction was greatest in the lumbosacral region, thus identifying a location of higher load absorption (Dimitriadis et al., 2011). Garbutt et al. also observed that running speed is positively related to the extent of stature shrinkage measured immediately after running (Garbutt, Boocock, Reilly, & Troup, 1990). While acute structural changes in the spine are not directly indicative of pain, with the progression in time, the mechanical stress associated with running's repetitive loading can potentially lead to changes in spinal structure and possibly musculoskeletal overuse symptoms including running-related LBP.

The recent interest in the body's natural ability to attenuate impact loads during running has led to a resurgence of barefoot and minimalist style running as a means to reduce the risk of running-related injuries (Perkins et al., 2014, Rixe et al., 2012, Tam et al., 2014). This running style typically focuses on running barefoot or wearing shoes with minimal heel cushion. Because of the reduced impact attenuation normally provided by footwear, runners typically adapt a change in foot strike pattern from the rear foot to the mid or forefoot and a reduction of peak vertical impact force. In essence, the proposed benefits from running with the minimalist footwear were based on the theory that it promotes a movement pattern that is conducive to lower shock loading during running (De Wit et al., 2000, Derrick and Mercer, 2004, Divert et al., 2005, Mercer et al., 2002, Robbins and Hanna, 1987).

It has been postulated that the biomechanical adaptations (i.e., foot strike pattern) associated with running barefoot or in minimalist footwear can lead to kinematic changes in the lumbo-pelvic region. For example, Delgado et al. reported decreased overall lumbar range of motion and peak leg impact measured through leg acceleration following an acute foot strike pattern shift from the rearfoot to the forefoot (Delgado et al., 2013). However, this study had a number of important limitations: first, the effects of foot strike pattern on the lumbar range of motion were examined in a single data collection session. The participants were acutely instructed to run using specific foot strike patterns, which may or may not translate to a more permanent movement pattern change. Second, the effect of minimalist running on paraspinal muscle activation was not examined. Excessive paraspinal muscle activation is hypothesized to contribute to increased lumbar spinal loading. Third, in practice, it may be unrealistic and ill-advised to suggest drastic changes in foot strike and running mechanics to injured or at-risk runners. It is clinically more meaningful to understand the progression of responses in lumbar biomechanics to minimalist style running over a longer duration of training.

The purpose of the present study was to investigate the effects of a 4-week running training for transitioning runners to minimalist footwear combined with technique guidance on the lumbar kinematics and paraspinal muscle activation in habitually shod runners. We hypothesized that the runners would exhibit a reduction in the lumbar range of motion and paraspinal muscle activation during the stance phase of running after training.

Section snippets

Subjects

Seventeen volunteers from the local running population were recruited. This sample size was determined a priori from a previous investigation on how change in foot strike pattern affects lumbar posture (Delgado et al., 2013). To achieve an 80% power, with α level of 0.05, we calculated that a sample size of 13 is needed to detect a difference in a repeated measures study design. Additional 4 subjects were recruited to account for potential attrition. The participants were included if they were:

Results

The reported weekly mileage per footwear condition during the 4-week protocol is presented in Table 3. The percentage of total running distance in the minimalist shoes gradually increased from 18.8% to 54.9% during the 4 weeks of training. A significant difference was detected in the preferred running speed (p = 0.007); the preferred running speed at MID was significantly slower than that at PRE (PRE vs. MID, 3.25 ± 0.33 vs. 3.13 ± 0.31 m/s, p = 0.016). No other differences in running speed

Discussion

Biomechanical evaluations aimed at identifying risk factors, prevention, and treatment strategies pertinent to running-related injuries have traditionally focused on the more common injuries such as knee pain and tendinopathy. In comparison, research regarding the biomechanics of lumbar spine during running is lacking. This is an important void in the current knowledge base that needs to be addressed, because lower back dysfunctions are relatively common in distance runners (Gonzalez et al.,

Conclusion

Our results demonstrated that a 4-week running training with minimalist footwear and technique guidance can induce significance changes in lumbar spine biomechanics during running. Specifically, the participants ran with a less flexed and more upright lumbar posture after training. Correspondingly, we observed a trend of reduction in the contralateral lumbar paraspinal muscle activation. These effects were observed when the runners ran wearing their regular running footwear. Our findings

Ethical statement

The authors declare that the procedure of the experiment meets the ethical requirement of Physical Therapy in Sport. The research procedure was approved by the University of Nevada, Las Vegas, Institutional Review Board for Biomedical Research.

Funding statement

This research was supported by the Faculty Opportunity Award from the Provost's Office and the Student Opportunity Research Grant from the Department of Physical Therapy, University of Nevada, Las Vegas. The funding sources were not involved in the study design, collection, analysis, and interpretation of the data in this research. The authors were fully responsible for the writing of the report and the decision to submit the article for publication.

Conflict of interest statement

The authors declare no conflicts of interest.

Acknowledgements

The authors would like to acknowledge the support provided by the University of Nevada, Las Vegas Sports Injury Research Center, and the Clinical Locomotion Neuromechanics Laboratory.

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