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Table of Contents
ORIGINAL ARTICLE
Year : 2022  |  Volume : 4  |  Issue : 2  |  Page : 133-140

Acute kinematic changes as a response to barefoot habituation training program: A randomized, parallel arm, trial


1 Department of Kinesiotherapy and Movement Sciences, Dr. D.Y. Patil College of Physiotherapy, Dr. D.Y. Patil Vidyapeeth, Pune, Maharashtra, India
2 Dean, Faculty of Medicine, Director, School of Physiotherapy, RK University, Rajkot, Gujarat, India
3 Principal, Dr. D.Y. Patil College of Physiotherapy, Dr. D.Y. Patil Vidyapeeth, Pune, Maharashtra, India

Date of Submission03-Apr-2022
Date of Decision10-Dec-2022
Date of Acceptance13-Dec-2022
Date of Web Publication19-Jan-2023

Correspondence Address:
Dr. Zafar Azeem
Department of Kinesiotherapy and Movement Sciences, Dr. D.Y. Patil College of Physiotherapy, Dr. D.Y. Patil Vidyapeeth, Pune, Maharashtra
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijptr.ijptr_182_22

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  Abstract 


Context: Barefoot running has seen a lot of scientific interest in the running community over the last decade. However, there are conflicting claims to its efficacy in improving acute adaptations in the form of joint kinematics. Interventions to transition from shod running to barefoot running are limited in scope and implementation.
Aim: The study investigated the kinematic differences between barefoot and habitually shod runners following 8 weeks of habituation training. It was hypothesized that the habituation phase with gradual increments in time spent barefoot would result in better kinematic changes in barefoot runners compared to habitual shod (in-shoe).
Setting and Design: Randomized parallel arm trial conducted on professional runners.
Methods and Materials: Thirty-two (n = 32) professional runners with a mean age of 21.5 ± 2.04 years with standing height measuring 1.69 ± 0.04 m and weighing 69 ± 3.55 kg were selected for the study. Participants were randomly allocated to experimental barefoot and control shod groups using computer-generated sequencing. The barefoot group received an transition plan in which the participants progressed from average time spent in walking and running barefoot. The control shod group was not required to do any changes to their traditional in-shoe training.
Statistical analysis used: The primary outcome measures were joint kinematics at trunk, hip, knee and foot during the treadmill walk analyzed thorough independent T test and paired t test. The level of significance was set at P < 0.05.
Results: The results indicated that the experimental barefoot group showed statistically significant (P < 0.01) changes to trunk flexion-extension during the preswing phase of running. Similarly, hip flexion-extension ranges were statistically significant (P < 0.01) in the habitual shod (in-shoe) group during the preswing to the terminal swing of running. Hip and knee flexion-extension ranges improved in the barefoot group with a statistical difference of P = 0.00 following 8 weeks of barefoot training. The mean difference for the change in hip and knee flexion ranges was of a higher magnitude for the barefoot group (26.88°) than the shod group (13.23°). Similarly, foot pronation-supination ranges improved for the barefoot group with P = 0.00.
Conclusion: In conclusion, running barefoot was no different from shod running, although habitually in-shoe athletes, when transitioning to barefoot condition, were essentially better at adopting the natural running style for certain variables.

Keywords: Footwear, Habituation, Running, Shod running, Transition


How to cite this article:
Azeem Z, Rathod PV, Palekar TJ. Acute kinematic changes as a response to barefoot habituation training program: A randomized, parallel arm, trial. Indian J Phys Ther Res 2022;4:133-40

How to cite this URL:
Azeem Z, Rathod PV, Palekar TJ. Acute kinematic changes as a response to barefoot habituation training program: A randomized, parallel arm, trial. Indian J Phys Ther Res [serial online] 2022 [cited 2023 Feb 1];4:133-40. Available from: https://www.ijptr.org/text.asp?2022/4/2/133/368049




  Introduction Top


Running or walking barefoot is a primitive form of human locomotion, going back to the homosapiens' era. The evolution from barefoot to running with shoes happened in the 1970s. The initial design of the shoe consisted of an elevated and cushioned heel which allowed the foot to strike in dorsiflexed position on initial contact resulting in a comfortable rearfoot strike (RFS) pattern.[1] Differences in strike patterns between habitually shod (shoe) and barefoot runners have been reported in the literature.[1],[2],[3],[4] In addition, it is also found that foot strike pattern is dependent on the speed of running among various other factors.[5]

Shod running and training have been shown to reduce cadence, lengthen stride and increase contact time compared to barefoot.[6] Forefoot strike (FFS) is often associated with increased knee flexion at touchdown during barefoot running.[1],[6] In walking literature, kinematic, kinetic, and muscle activity differences have reported flat foot position, increased knee flexion, and reduced peak vertical force at initial contact.[7] Muscle activity patterns in FFS have shown early and extended plantar flexor contractions before ground contact when compared with RFSs.[8] Scientific interest into barefoot running may encourage runners to attempt to run barefoot. Habitually in-shoe runners may experiment with barefoot training to improve performance. Mechanical changes at knee and ankle joints are seen in trained shod runners.[9] Thus, it may be advised to take a guided and cautious approach to transition from shoe-based running to barefoot.[10] With a concomitant rise in the domains and subdomains of barefoot biomechanics, literature on understanding the effects of transition training for habitually shod runners toward barefoot has been limited. Therefore the objective of the study was to analyze changes to joint kinematics following barefoot adaptation training on habitually shod (in shoe), endurance runners. This was done by studying the adaptations during 8-week habituation or transition training following an incremental increase in the time spent running, walking, and training barefoot.


  Subjects and Methods Top


This was single-centric, single-blinded, parallel-group randomized study conducted in the city of Pune, Maharashtra, India. Following an initial screening, participants were selected if they were males or females aged between 18 and 30 years, had participated in Zonal, State or National level running competitions from minimum participation of 2 years to maximum participation of 6 years, and were using conventional athletic shoes for their running and training purposes. Participants with any self-reported history of musculoskeletal or neurological injury, which may compromise participation in the study, presence of any congenital deformities such as flatfoot, hallux valgus, and/or club foot, and had a 6-month history of recurrent ankle sprains at the start of the study. The study was performed in accordance with the principles of the Declaration of Helsinki (Seoul, 2008) and ethical approval obtained from the Institutional Ethics Committee of RK University, Gujarat (SPT/IEC/2019/2). The trial was registered prospectively at the Clinical Trials Registry of India (CTRI/2019/08/020567).

Participants

A total of 61 participants were screened, of which 21 participants did not meet the inclusion criteria. Initially screened for any musculoskeletal injuries within 3 months before the study and participant in regular training schedules for a minimum of 20 km/week and were familiar with treadmill running. An informed consent form was signed by the participants if they agreed to participate in the study. The study was a single-blind study, in which the Investigator was blinded to group allocation. However, it was not possible for participants blinding to group concealment or the intervention due to the nature of the testing and training protocol.

Randomization and group allocation

Simple randomization for participant allocation was carried out for 41 selected participants who met the inclusion criteria of the study. This was carried out by the personnel not involved in the study who had no background of the study to reduce allocation. All participants were allotted a participant code after screening for eligibility criteria.

Sample size estimation

An a priori power analysis with α = 0.05, Power (1-β) = 0.80, and effect size = 0.40 was used to calculate the sample size based on data from a study by Squadrone et al.[11] This study reported the difference in various footstrike, spatio-temporal stride, and kinematic variables between footwear (barefoot, minimalist, and shod) conditions. Calculations for sample size estimation were done using G-Power Statistical software, whereby an independent t-test was used to evaluate for any group differences. Based on this estimation, the standard deviation for the primary outcome measures of the trunk, hip, and knee joint angles was found to be 0.3°. At 85% confidence interval and margin of to be 5, the sample size was found to be 26. We expected a higher dropout for the study due to the novelty of the training program and the involvement of professional runners in the study. Keeping this in mind, a total of 61 participants were screened.

The experimental group received 20 participants, and the control shod group received 21 participants, who were then tested for pretraining measurements of joint kinematics. Three participants from the experimental barefoot group and five participants from the control shod group dropped out of the study due to noncompliance with the protocol. The CONSORT flowchart for participant selection and recruitment is given in [Figure 1].
Figure 1: CONSORT flow chart for participant selection and allocation

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Progression criteria

During the 1st week of training, a 10-min barefoot session was given and participants who normally were running for 45 min, were asked to run for 35 min with the addition of 35 min of barefoot session. This was done to minimize the effects or damage that may happen due to a new training regime. The program was progressed to maintain the conditioning status of participants as all participants were from professional backgrounds from Zonal, State, and National Level participation.

Instructions to participants

There were no formal instructions given to the participants on either changing patterns or running in any specific way to maximize their efforts. As a means of understanding their injury concerns, if occurred any, a training log was also given to the participants.

Pre- and post-training assessment of outcome measures

Sagittal, frontal, and horizontal plane kinematics were captured using high-resolution 3D camera embedded in the Walker View Platform. This was done in consultation with and in the presence of Physiotherapy Consultant at the testing facility who was experienced in handling the Platform.

The primary outcome measures of interest were joint angles of trunk sway, including flexion-extension and lateral flexion, hip flexion-extension, knee flexion-extension, and foot flexion-extension during a 10 min treadmill walking and running at self-selected pace for 5 min followed by automatically adjusted speed for the next 5 min. Joint angles were captured during this time and analyzed for the changes in joint angles. For the purpose of reference, the right extremity was analyzed for all joint angle measurements.

Training surfaces

As participants were from Zonal, State, and National Levels, it was not feasible to standardize the training surface. However, the training surface on which athletes regularly performed their training sessions were the Astroturf athletic track, over the ground on grass and a regular wooden and matte flooring in the training gym facility of the respective athletes.

At any given time, the participants in both groups were asked to report any injuries related to or not related to training.

Experimental barefoot group

Being a transition protocol, it was necessary that the habitually shoe runners are progressively trained to adjust to the new “barefoot” form of training. For this to happen, during the 1st week of the training, a 10-min barefoot session was given. To follow the typical habituation training module, participants in the barefoot group, who typically run 45 min with shoes, were asked to run 35 min with an addition of 10 min under barefoot conditions. This was a conservative approach to minimize any injury risk that may happen due to change in the training plan. The entire training was phased to maintain conventional volumes and avoid any phases of deconditioning. Details of the barefoot training plan are given in [Figure 2].
Figure 2: Experimental barefoot group training plan

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Control shod group

The participants in the control shod group were asked to continue their regular training drills in the shoe and report back for posttraining testing at 8 weeks.

At any given time, the participants in both the groups were asked to report any injuries related to or not related to training being given.

Statistical analysis

All the outcome measures were analyzed using SPSS Version 22 for IBM. Group comparisons for joint kinematic changes at the trunk, hip, knee, and foot were analyzed through Independent t-tests and paired t-tests using IBM SPSS statistics for windows version 22.4, Armonk, New York.


  Results Top


The demographic information of 32 participants who were formally enrolled and participated in the study is presented in [Table 1]. An appropriate test of normality distribution and homogeneity of variance of samples was carried, and the data were found to be normally distributed.
Table 1: Demographic information

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The barefoot group showed statistically significant changes to hip kinematics during the treadmill running performance following habitation training with P = 0.00. However, changes to other joints remained statistically nonsignificant [Table 2].
Table 2: Changes to joint kinematics in the barefoot group

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The shod group showed statistically significant changes to hip kinematics during the treadmill running performance following habitation training with P = 0.00. However, changes to other joints remained statistically nonsignificant [Table 3].
Table 3: Changes to joint kinematics in control shod

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Joint kinematics for hip flexion-extension improved significantly at the end of 8 weeks of habituation training in the barefoot group (P = 0.00). Similar changes were also observed for knee flexion-extension (P = 0.00). Changes to other joint interactions were not observed [Table 4].
Table 4: Between-group comparisons for joint kinematics

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  Discussion Top


The study was conceptualized to study the biomechanical implications of barefoot training following a phase of habituation and compared habitually shod runners with trained barefoot runners. There was no difference in joint kinematics in the barefoot group compared to habitually shod running. However, there are some interesting that we would like to describe.

The findings from our study is in partial agreement to studies on lower limb kinematics at ground contact and vertical ground reaction forces between habitually shod, minimalist, and barefoot running.[12],[13] Even though there were no restrictions on the type of shoe used by the runners in our study, running shoes have shown reduced kinesthesia, reduced loading rate, and tibial acceleration.[14] It can be inferred that prolonged usage of shoe as a means of protection may also lead to reduced balance and foot-to-surface interaction and renders the body at loss for its potential shock-absorbing function.

However, the newer forms of minimalist shoes are reported to have similar adaptive mechanics to habitual and barefoot running.[9],[15],[16]

Risk mitigation factors for running-related injuries involve foot strike patterns and foot pressures.[17] Runners prefer toward favorable Forefoot strike (FFS) patterns while running in the minimalist shoe and while progressing to running barefoot. In our study, we did not find any such changes, mostly due to the relatively small sample size and perhaps.

The previous researchers' brief instructions on changes in gait. Intentionally, we did not give any specific instructions to our participants because we wanted to know the effect of barefoot or footwear without any conscious changes to the running form or technique.

The extensive literature on habitually shod runners specifies using Rare foot strike (RFS) and barefoot runners to adopt FFS or mid-foot strike.[1] On closer evaluation, it is observed that 89% of habitually shod runners run with RFS.[18] Overall, our study revealed that barefoot runners following an 8-week habituation phase did not change kinematically at foot pronation-supination while running at self-selected treadmill running. We did not find any differences at foot placements after the habituation phase, which may also be due to the fact that the runners in our group may have inherent lower ankle stiffness, thereby a small foot strike angle.[19] However, biomechanical research regarding long-term effects and chronic adaptations needs to be done to claim this finding in the future.

The motor learning process is liable to take more time to show true adaptations at local and systemic levels. Acutely changing footwear or switching to the barefoot condition may also have higher variability in ankle kinematics due to the motor learning process being in progress.[20]

Moving up the kinetic chain, we found significant differences in knee flexion angles between barefoot and shod runners. Our findings contrast with several authors reporting no major changes in knee flexion angles following short-duration in-shoe or barefoot training.[9],[21],[22],[23],[24] In addition, as the body tends to adapt over time, increments in knee flexion at ground contact are expected.[11]

Less knee flexion range of motion is shown to favor reducing the risk of Run related injuries (RRIs) like patellofemoral pain and iliotibial band friction as the stress on the patellofemoral joint are reduced.[25] However, this also adds to the risk of sustaining more ankle injuries as the load shifts from the knee to the ankle.[26] It is worth mentioning that with controlled, graded introduction to the barefoot form of running, we may, in fact, achieve better knee flexion angles, thus reducing the possibility of sustaining more RRIs and improving running kinematics as a whole. Nevertheless, evidence from prospective studies is needed to confirm this.

Although it was beyond the scope of our work, we found that skeletal maturity seems to influence motor performance irrespective of being habitually shod or barefoot.[27] With extended usage and prescription of different footwear over the past so many years, it may be inferred that shoes have influenced the natural form of running gait, thus offsetting the effects of maturity of soft connective tissues such as muscles, tendons, and ligaments on protection and stability. With time, it has shown detrimental effects as running-related injuries continue to rise even as the shoe underwent a change in its fabrication, design, and function.

Limitations of the study

In addition, our study has some limitations. First, it was not feasible to standardize the type of shoes used by the runners in the shod group due to the practical implications of professional runners not being able to choose different shoes for study purposes. In fact, runners were encouraged to use the regular shoe to minimize the effect of changing shoe type on running mechanics. Differences in structural properties of the shoe, like mass, cushioning and heel-to-toe drop, may have existed in the footwear. With the findings of the study, larger standard deviations noted within the shod conditions may have led to higher variability, a similar study design with standardization of the shoe is recommended. Furthermore, treadmill running is seen to be close to the ground running but is not necessarily identical. We did not take into account the surfaces on which athletes were training as it may implicate toward different training surfaces to show any adaptive running patterns. Therefore, the acute adaptions noted with a change in footwear may not apply to runners when running on different surfaces.


  Conclusion Top


The study findings reflected that barefoot training with a phase of habituation does not give any additional benefits on the whole of biomechanical characteristics. However, there are important findings in response to acute adaptations to this novel training. Running with the shoes does not give any added advantage in running mechanics; however, its role in protection due to cushioning properties cannot be ruled out. Sway on the trunk was reduced with the barefoot group, which also resulted in improved knee flexion ranges without affecting the degree of foot flexion to pronation ranges.

Clinical implications

The findings from the study may impact on various training and rehabilitation methodologies adopted to manage common musculoskeletal conditions in athletic settings. It is worth mentioning that footwear par SE may not account for the reduction of running-related injuries. Therefore, its role is fairly restrictive for protection from injuries. The aspect of training barefoot is most likely to influence the ground-to-foot contact by increasing the natural kinesthetic sense of the planted foot, which is otherwise found to be inhibited due to the constant use of shoes during training and competition. The premise of training barefoot with a safer transition period will help athletes for a better acclimatization to a new training intervention and ensure their safe participation for sports and games.

Acknowledgments

We acknowledge the support of all the participants who consented to participate in the study. We would like to thank Dr. Sachin Sarode, Director (Research), and Dr. D.Y. Patil Vidyapeeth, Pune, for proofreading of the manuscript and suggestions given for the same.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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  [Table 1], [Table 2], [Table 3], [Table 4]



 

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