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ORIGINAL ARTICLE
Year : 2016  |  Volume : 16  |  Issue : 1  |  Page : 68-73

An analysis of physical performance between backward and forward walking training in young healthy individuals


1 Department of Rehabilitation Health Sciences, Collage of Applied Medical Sciences, King Saud University, Riyadh, Kingdom of Saudi Arabia
2 Department of Physiotherapy, Faculty of Applied Medical Sciences, Manav Rachna International University, Faridabad, Haryana, India
3 Department of Physiotherapy, Cairo University Hospital, Cairo, Egypt

Date of Web Publication7-Jan-2016

Correspondence Address:
Shaji John Kachanathu
Department of Rehabilitation Health Sciences, College of Applied Medical Sciences, King Saud University, Office No. 2083, Building No. 24, P.O Box: 10219, Riyadh 11433
Kingdom of Saudi Arabia
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/1319-6308.165112

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  Abstract 

Objective: Walking on a treadmill is a common tool for lower extremity rehabilitation in the clinical setting. Backward walking (BW) shows significant differences with forward walking (FW) and these differences are potentially useful in rehabilitation. The aim of this study was to evaluate the effect of BW and FW on sports performance variables such as functional strength, balance, aerobic and anaerobic capacities of young healthy adults. Materials and Methods: Totally, 30 young healthy male subjects with a mean age of 26.1 ± 4.3 years participated in this study. Subjects were divided into two groups, forward walking group (FWG) and backward walking group (BWG) (n = 15) and performed forward and backward directions walking on a treadmill at consistent speed and 10% inclination, respectively, for duration of 6 weeks. Study outcomes such as functional strength, balance, aerobic and anaerobic capacities were measured on pre- and post-intervention. Results: The results of the study observed that lower limb functional strength, aerobic and anaerobic capacities were improved with BWG than FWG. However, the static and dynamic balances were showed no significant improvement between both walking groups. Conclusion: Backward walking training has been proved to be effective in improving the lower limb functional strength, aerobic and anaerobic capacities of the normal healthy individuals, whereas the balance components has to be studied in future in an extensive ways in BW.

  Abstract in Arabic 

الهدف: المشي على السير الكهربائي هو وسيلة شائعة لإعادة تأهيل الأطراف السفلية في العيادة. المشي للخلف (BW) يظهر اختلافات كبيرة عن المشي إلى الأمام (FW) وهذه الاختلافات يمكن أن يكون مفيدا في إعادة التأهيل. وكان الهدف من هذه الدراسة إلى تقييم تأثير BW وFW على متغيرات الأداء الرياضي مثل القوة الوظيفية، والتوازن، والقدرات الهوائية واللاهوائية من الشباب البالغين الأصحاء.
المواد وطرق: عدد، 30 من الشاب الذكور الأصحاء بمتوسط ​​عمر 26.1 ± 4.3 سنوات شاركو في هذه الدراسة. تم تقسيم العينة إلى مجموعتين، مجموعة المشي إلى الأمام (FWG) ومجموعة المشي للخلف (BWG) (ن = 15)، وأجرى الإختبار على جهاز السير الكهربائي للمجموعتين بإرتفاع 10٪ ، على التوالي، لمدة 6 أسابيع . ومن ثم تم قياس نتائج الدراسة في القوة الوظيفية، والتوازن، والقدرات الهوائية واللاهوائية قبل وبعد التدخل.
النتائج: أضهرت نتائج الدراسة تطور في قوة و وظيفة الأطراف السفلية ، والقدرات الهوائية واللاهوائية وتحسنت مع المشي للخلف (BWG) أكثر من تحسنها في المشي للأمام من (FWG). ولم يتم ملاحضة اي تحسن ملموس بين المجموعتين المشي للتواتزن.
الاستنتاج: أثبت التدريب على المشي الى الوراء فعاليته في تحسين قدرات الأطراف السفلية في القوة الوظيفية، و القدرات الهوائية واللاهوائية للأفراد الأصحاء ، في حين أن التوازن لابد من دراسته في المستقبل بشكل أوسع في (BW)

Keywords: Backward walking, running addiction scale, shuttle run, single leg hop, standing stork, star excursion balance test


How to cite this article:
Kachanathu SJ, Alabdulwahab SS, Negi N, Anand P, Hafeez AR. An analysis of physical performance between backward and forward walking training in young healthy individuals. Saudi J Sports Med 2016;16:68-73

How to cite this URL:
Kachanathu SJ, Alabdulwahab SS, Negi N, Anand P, Hafeez AR. An analysis of physical performance between backward and forward walking training in young healthy individuals. Saudi J Sports Med [serial online] 2016 [cited 2023 Dec 4];16:68-73. Available from: https://www.sjosm.org/text.asp?2016/16/1/68/165112


  Introduction Top


Humans have been looking for ways to enhance the sports performance and increase the chances of victory. Forward walking (FW) has benefited from a great deal of investigation, because, as a form of locomotion, it is the basis for a number of competitive sports as well as health and fitness activities however backward walking (BW) on the other hand, has not received this kind of attention. Although walking in the backward direction is a relatively novel task for most people, there are several situations during everyday life activities that include BW as stepping away from the kitchen and also various sports such as soccer, football, basketball and tennis all incorporate BW during competition. Various studies on forward and BW have determined the effect of these trainings. Walking has been established as one form of endurance training for preventive purposes. Sufficient training effects with little risk of overstrain has been suggested.[1] Walking is a popular, convenient, and relatively safe form of exercise that holds great promise for weight management.[2]

Walking has long been used by both rehabilitation and fitness professionals to help improve cardiovascular fitness and to rehabilitate musculoskeletal injuries. Humans generally learn to walk and run in a forward direction with little difficulty. This is inherently logical since our field of view is in the forward direction. Because of its functionality, most walking studies and clinical protocols have involved FW. However, since the early 1980s, there has been increased interest in studying the benefits of BW, also referred to as retropulsion.[3] BW reversing leg movement trajectories and the leg not only reverses its direction of movement, but it travels in the opposite direction along virtually the same path as in walking forward.[4] Vilensky et al. (1987) concluded that BW was different from FW, observed walking backward was associated with increased cadence and decreased stride length when compared with FW.[5]

It has been investigated on motor control/learning and rehabilitation bases, but no investigations have been conducted with sports performance variables in mind. The purpose of this paper is to design to compare forward and BW and its effects on physical performance components such lower limb functional strength, aerobic and anaerobic capacities.

Backward walking/running technique prevalent in football, basketball, and tennis has recently gained popularity as a method for treating patella-femoral pain syndrome.[6] Various studies on forward and BW have determined the effect of these trainings on biomechanical and kinesiological aspects [4],[6],[7] however the basic sports performance components have not been looked upon.

Although BW training may seem a reasonable alternative than FW/running, in sports performance enhancement little is known about in the lower limb functional strength, balance, aerobic capacity, and anaerobic capacity in young healthy individual's response to forward and backward mode of locomotion training protocols. This study aims to find out the differences in the lower limb functional strength, balance, aerobic capacity, and anaerobic capacity in young healthy individuals between these two training protocols.


  Materials and Methods Top


Totally, 30 young healthy male subjects with a mean age of 26.1 ± 4.3 years participated in this study as per the inclusion and exclusion criteria. Subjects were free from any musculoskeletal problems and had no recent or remote history of significant lower extremity injuries that might have affected their gait. In addition, subjects were excluded from the study in case of any type of the visual or vestibular deficiency. Prior to study obtained informed consent from each participant, and also obtained the study protocol approval from the institution's ethical committee.

Subjects were divided into two groups, forward walking group (FWG) and backward walking group (BWG) (n = 15) and performed forward and backward directions walking respectively on a treadmill. BW and FW were demonstrated, and subjects were given sufficient practice to become confident. We allowed the subject to habituate to walking on the treadmill respective to their group either FW with one practice session or BW with two or more sessions. Prior to intervention, all subjects were given 5 min for warm up and familiarize with treadmill using a self-selected pace [8] and to make them familiar with the task and decrease the chances of falls on the treadmill. Once the subjects were comfortable walking on the treadmill, participants walked both forward and backward on an instrumented dual-belt treadmill (ForceLink, Culemborg, The Netherlands), for ~ 15 min. For each condition, we set both belts speed to 1.1 m/s (4.0 km/h), and the order of FW and BW conditions was randomized across the participants. All participants wore sports shoe during the intervention.

Study outcomes such as functional strength, balance, aerobic, and anaerobic capacities were measured at pretest (0 week), at the end of 2nd week, posttest (4th week), and 6th week (follow-up). Functional strength was done with the help of single leg hop test, the static and dynamic balance were assessed with the help of Stork standing test and star excursion balance test. The aerobic and anaerobic capacities were measured by 20-m shuttle run test and running-based anaerobic sprint test.[9]


  Results Top


Software SPSS 17.0 from IBM Corporation was employed for statistical analysis. Analysis of variance was used to compare the means between the two groups. Repeated measures ANOVA was done for the difference in variables within both the groups. The results of this study demonstrate that lower limb functional strength as well as aerobic and anaerobic capacity was improved with BWG than FWG. The Static and dynamic balance were improved within both the groups, but there was no statistically significant difference between BWG and FWG. The means and standard deviations of sports performance variables between FWG and BWG are shown in [Table 1] and [Table 2]. Whereas, [Graph 1],[Graph 2],[Graph 3],[Graph 4],[Graph 5] showed the changes in the variables at different durations such as pretraining (0 week), at the end of 2nd week, at the end of 4th week, and at the end of 6th week (as follow-up).
Table 1: Strength, aerobic and anaerobic capacities at 0 week and at 4th week

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Table 2: Static and dynamic balances at 0 week and at 4th week

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Pretraining (0 week), according to the one-way ANOVA, for both groups, the variables such as lower limb strength, static balance, dynamic balance, aerobic capacity, and anaerobic capacity were not significant.

At the end of the 2nd week, in BWG, functional strength and aerobic capacity were improved significantly P = 0.012; P = 0.028, respectively, as compared to FWG. Whereas, the anaerobic capacity (P = 0.10); the static balance (P = 0.38) and dynamic balance (P = 0.43) were not found to be statistically significantly different.

At the end of 4th week, the strength (P = 0.01); the aerobic capacity (P = 0.02) and anaerobic capacity (P = 0.04) were also found to be statistically significant. The static balance and dynamic balance were found to be insignificantly different (P > 0.05).


  Discussion Top


The results of this study demonstrated improvement in both the groups for strength, aerobic capacity and anaerobic capacity, however, the subjects in BWG who underwent 15 min of BW at 10° inclination showed significant improvement than FWG. Although no significant improvement was found in static or dynamic balance in both the groups, however within each group difference in the balance was present. Moreover no significant decrease was seen in the variables in follow-up (at the end of 6th week) and a carryover effect was found in all study variables except the aerobic capacity, which was significantly reduced at 6th week.

The significant improvement in functional strength in BWG is in accordance with various earlier studies have been observed the increases in lower limb muscle strength with retro walking.[6],[10] In a systematic review, it has been observed that when walking backward the knee extensor musculature plays a major role in generating the force necessary for propulsion. In fact, electromyographic (EMG) activity for rectus femoris and vastus medialis was considerably higher while walking backwards.[11] Kinetic analysis of backward running suggests that compressive forces at the patellofemoral joint are lower when compared with forward running.[6],[12],[13] This was caused by an increased knee moment, due to differences in magnitude and location of the ground reaction forces vector relative to the knee.[12] Thus, it is a good alternative for FW training rehabilitation; additionally BW training program using 10° inclination technique also increases quadriceps power and strength. The changes of muscles strength at lower limbs may contributed by the contraction modes of lower limb muscles are reversed in BW conditions. For example, eccentric contraction of the quadriceps muscle during the loading phase of the FW gait is replaced by a concentric contraction during BW.[4] Previous studies indicate that strengths of quadriceps and hamstring muscles are increased after BW exercise.[13],[14],[15]

There was a significant difference in static and dynamic balance within FW and BW groups, however; there was no statistical significance difference when compared between FW and BW groups. This may be because inclined walking was incorporated in both the groups and a strenuous bout of eccentric exercise stimulates the nervous system to better control and distribute the forces that are acting on particular muscles. Therefore, it may be assumed that the motor learning and balance strategies developed in the subjects were nearly similar due to the inclusion of downhill running in both groups. Hao and Chen, (2011) in his study indicated that the balance of the boys (aged 7.19 ± 0.40 years) had been significantly improved after 12 weeks of BW training program.[16] The exact mechanism through which BW exercise causes an improvement of balance is yet to be fully elucidated. However in our study the age group was 26.1 ± 4.3 years and study duration was for 4 weeks. This study differences in balance emphasizes the importance of duration of BW training must be more than 4 weeks in case of balance component enhancement. Body balance is believed to be controlled by the visual, vestibular and proprioceptive systems.[17] It has been generally assumed that there are many systems within the body that work in concert to move the center of mass in relation to the base of support in a controlled manner when engaged in dynamic tasks.[18] In our study between BW and FW not shown significant changes in balance whatever changes seen within each group may be associated with the improvement of balance involvement of three systems, that is, visual, vestibular and proprioceptive systems played equal role in both study groups.

Muscle reflex activity plays an important role in the regulation of stable locomotion,[19] during human locomotion, cutaneous reflexes have been suggested to function to preserve the balance. Furthermore, the reflex amplitude can change between different phases of the movement cycle depends on types of task. Hoogkamer et al. (2012), observed that the instability related to BW, but no support was found for the reason for the observed increased crossed responses in TA during BW.[20] Hence, one would expect that BW is a good model for unstable gait. In line with earlier observations that BW is more variable than FW,[21] we observed that BW is less locally stable than FW.

The aerobic capacity of BWG was significantly higher as compared to FWG because the backward movement places more stress on the body systems thereby increasing energy demands. It has been supported by the observation that for a given speed, backward locomotion elicits a greater metabolic demand and cardiopulmonary response than forward locomotion.[22] BW results in the mean EMG activity of the lower extremities over the gait cycle,[23] which suggests a greater level of energy expenditure during BW than FW. In fact, it has been found that, during BW, oxygen consumption and heart rate (HR) are much greater than during matched speed FW,[13],[24] suggesting that BW need more metabolic cost and provide more stimulus to maintain fitness of cardiovascular system. BW has been considered an attractive exercise alternative for aerobic training. The higher physiological stress resulting from backward locomotion is advantageous for both fitness training and rehabilitation.

Cortical input is responsible for the reconfiguration of the spinal networks controlling forward and backward locomotion. This modulation of cortical neurons would allow that the same spinal signals address different muscles in different modes of locomotion or to change the timing of the spinal signals.[25] During BW, an increase in stride frequency is needed to maintain the predefined walking speed in the presence of a shorter stride length. Shorter stride lengths in BW compared with FW were previously reported for both treadmill [5] and for overground BW.[26] Previous studies have shown that stride frequency influences joint kinematics and kinetics.[27] Hence, it can be expected that it will also have an effect on the calculated muscle contributions. In the present study, we evaluated the relative percent contribution rather than the absolute muscle contributions. Therefore, we feel that the influence of stride frequency on the interpretation of our results is negligible. Besides individual biomechanical factors, propulsive mechanisms of BW and FW might also explain differences in strength/anaerobic components.

The electromyographical activity for the biceps femoris and semitendinosus muscles has been found to be considerably higher during BW rather than FW.[3] In BW, the role of the hamstrings is to initiate the swing phase by contracting concentrically.[4] Specifically, during the early swing phase of BW the main function of the hamstring muscles is to initiate hip extension and knee flexion, thus resulting in greater hamstring activation.[4] Muscle activities from the paraspinal muscles, vastus medialis, and tibialis anterior while walking backward was significantly greater than when walking forward.[28]

Ratings of perceived exertion were higher during BW at 0% compared with FW at 5% elevation; moreover at both 0 and 5% elevation, ratings of perceived exertion were higher during BW than FW.[29] BW on a treadmill at 67.0 m/min (2.5 mph) and grades of 5%, 7.5%, and 10% elicits a greater percent HRmax and percent VO2 max than does FW,[24] this would be the reason to expected to improvement in aerobic endurance.

The aerobic capacity was significantly decreased in follow-ups between the BW and FW groups. This may be due to the fact that the training protocol included patterns of interval training leading to the removal of the lactic acid produced in the body.[30] Our study subjects were not under interval training. This indicates that training-induced adaptations include a lower blood lactate concentration at any given workload and higher blood lactate concentration during maximal exercise.[31] Therefore confirming the suggestions made by Chen et al. 2008 based on the blood lactate concentration BW group showed more improvement than FWG.


  Conclusion Top


Inclined BW has been proved to be effective in improving the lower limb overall functional strength, aerobic capacity and anaerobic capacity of the normal healthy individuals, as there is an increased demand on all body systems during backward locomotion. Thus, retro running or walking can be incorporated in fitness programs to maintain and can be used as a part of rehabilitation program to improve aerobic and anaerobic capacities, as well as lower extremity functional strength.


  Acknowledgments Top


The authors would like to extend their appreciation deanship of research, Research Center of College of Applied Medical Sciences at King Saud University for scientific support during this research.



 
  References Top

1.
Adesola AM, Azeez OM. Comparison of cardio-pulmonary responses to forward and backward walking and running. Afr J Biomed Res 2009;12:95-100.  Back to cited text no. 1
    
2.
Toubekis AG, Douda HT, Tokmakidis SP. Influence of different rest intervals during active or passive recovery on repeated sprint swimming performance. Eur J Appl Physiol 2005;93:694-700.  Back to cited text no. 2
    
3.
Browning RC, Kram R. Energetic cost and preferred speed of walking in obese vs. normal weight women. Obes Res 2005;13:891-9.  Back to cited text no. 3
    
4.
Chaloupka EC, Kang J, Mastrangelo MA, Donnelly MS. Cardiorespiratory and metabolic responses during forward and backward walking. J Orthop Sports Phys Ther 1997;25:302-6.  Back to cited text no. 4
    
5.
Chen TC, Nosaka K, Wu CC. Effects of a 30-min running performed daily after downhill running on recovery of muscle function and running economy. J Sci Med Sport 2008;11:271-9.  Back to cited text no. 5
    
6.
Cipriani DJ, Armstrong CW, Gaul S. Backward walking at three levels of treadmill inclination: An electromyographic and kinematic analysis. J Orthop Sports Phys Ther 1995;22:95-102.  Back to cited text no. 6
    
7.
DeVita P, Stribling J. Lower extremity joint kinetics and energetics during backward running. Med Sci Sports Exerc 1991;23:602-10.  Back to cited text no. 7
    
8.
Eisner WD, Bode SD, Nyland J, Caborn DN. Electromyographic timing analysis of forward and backward cycling. Med Sci Sports Exerc 1999;31:449-55.  Back to cited text no. 8
    
9.
Emery CA. Does decreased muscle strength cause acute muscle strain injury in sport? A systematic review of the evidence. Phys Ther Rev 1999;4:141-51.  Back to cited text no. 9
    
10.
Fitzpatrick R, McCloskey DI. Proprioceptive, visual and vestibular thresholds for the perception of sway during standing in humans. J Physiol 1994;478:173-86.  Back to cited text no. 10
    
11.
Flynn TW, Connery SM, Smutok MA, Zeballos RJ, Weisman IM. Comparison of cardiopulmonary responses to forward and backward walking and running. Med Sci Sports Exerc 1994;26:89-94.  Back to cited text no. 11
    
12.
Flynn TW, Soutas-Little RW. Patellofemoral joint compressive forces in forward and backward running. Med Sci Sports Exerc 1991;23:32.  Back to cited text no. 12
    
13.
Grasso R, Bianchi L, Lacquaniti F. Motor patterns for human gait: Backward versus forward locomotion. J Neurophysiol 1998;80:1868-85.  Back to cited text no. 13
    
14.
Hao WY, Chen Y. Backward walking training improves balance in school-aged boys. Sports Med Arthrosc Rehabil Ther Technol 2011;3:24.  Back to cited text no. 14
    
15.
Hicheur H, Terekhov AV, Berthoz A. Intersegmental coordination during human locomotion: Does planar covariation of elevation angles reflect central constraints? J Neurophysiol 2006;96:1406-19.  Back to cited text no. 15
    
16.
Hoogkamer W, Massaad F, Jansen K, Bruijn SM, Duysens J. Selective bilateral activation of leg muscles after cutaneous nerve stimulation during backward walking. J Neurophysiol 2012;108:1933-41.  Back to cited text no. 16
    
17.
Hooper TL, Dunn DM, Props JE, Bruce BA, Sawyer SF, Daniel JA. The effects of graded forward and backward walking on heart rate and oxygen consumption. J Orthop Sports Phys Ther 2004;34:65-71.  Back to cited text no. 17
    
18.
Jordan K, Challis JH, Newell KM. Walking speed influences on gait cycle variability. Gait Posture 2007;26:128-34.  Back to cited text no. 18
[PUBMED]    
19.
Kurz MJ, Wilson TW, Arpin DJ. Stride-time variability and sensorimotor cortical activation during walking. Neuroimage 2012;59:1602-7.  Back to cited text no. 19
    
20.
Maimone J, Mead C, Strong K, Umstot T, Besser M, Mount J, et al. Comparison of the electromyographic activity of the vastus medialis oblique during retrowalking on level and inclined treadmill surfaces. Gait Posture 1996;4:182-3.  Back to cited text no. 20
    
21.
Masumoto K, Takasugi S, Hotta N, Fujishima K, Iwamoto Y. A comparison of muscle activity and heart rate response during backward and forward walking on an underwater treadmill. Gait Posture 2007;25:222-8.  Back to cited text no. 21
    
22.
Roos PE, Barton N, van Deursen RW. Patellofemoral joint compression forces in backward and forward running. J Biomech 2012;45:1656-60.  Back to cited text no. 22
    
23.
Schwarz M, Urhausen A, Schwarz L, Meyer T, Kindermann W. Cardiocirculatory and metabolic responses at different walking intensities. Br J Sports Med 2006;40:64-7.  Back to cited text no. 23
    
24.
Thorstensson A. How is the normal locomotor program modified to produce backward walking? Exp Brain Res 1986;61:664-8.  Back to cited text no. 24
[PUBMED]    
25.
Umberger BR, Martin PE. Mechanical power and efficiency of level walking with different stride rates. J Exp Biol 2007;210:3255-65.  Back to cited text no. 25
    
26.
Vilensky JA, Banckiewicz E, Gehlsen G. A kinematic comparison of backward and forward walking in humans. Hum Mov Stud 1987;13:29-50.  Back to cited text no. 26
    
27.
Westcott SL, Lowes LP, Richardson PK. Evaluation of postural stability in children: Current theories and assessment tools. Phys Ther 1997;77:629-45.  Back to cited text no. 27
    
28.
Winter DA, Pluck N, Yang JF. Backward walking: A simple reversal of forward walking? J Mot Behav 1989;21:291-305.  Back to cited text no. 28
    
29.
Zagatto AM, Beck WR, Gobatto CA. Validity of the running anaerobic sprint test for assessing anaerobic power and predicting short-distance performances. J Strength Cond Res 2009;23:1820-7.  Back to cited text no. 29
    
30.
Zehr EP, Duysens J. Regulation of arm and leg movement during human locomotion. Neuroscientist 2004;10:347-61.  Back to cited text no. 30
    
31.
Zelenin PV, Deliagina TG, Orlovsky GN, Karayannidou A, Stout EE, Sirota MG, et al. Activity of motor cortex neurons during backward locomotion. J Neurophysiol 2011;105:2698-714.  Back to cited text no. 31
    



 
 
    Tables

  [Table 1], [Table 2]


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