Oxygen COnsumptiOn While Standing With Unstable ShOe Design

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HUMAN MOVEMENT2014, vol. 15 (3), 160– 165Oxygen consumption while standingwith unstable shoe designdoi: 10.1515/humo-2015-0006Benedikt A. Gasser *, **, Adrian M. Stäuber **, Glenn Lurmann, fabio A. breil,Hans H. Hoppeler, Michael VogtSwiss Health & Performance Lab, Institute of Anatomy, University of Bern, Bern, SwitzerlandAbstractPurpose. This study explored the effects of unstable shoe design on oxygen consumption. Methods. Oxygen consumption(VO2) and heart rate (HR) were measured in 16 individuals while barefoot, wearing unstable shoes (Masai Barefoot Technology)and wearing conventional sport shoes while standing and walking on a treadmill and for 5 individuals while walking arounda 400 m track. Results. When wearing the MBT shoes, a significant (p 0.01) increase of 9.3 5.2% in VO2 was measuredwhile standing quietly for 6 min. No differences in VO2 and HR were observed between the MBT shoes or weight-adjustedconventional shoes (to match the weight of the MBT shoes) while walking on a treadmill. However, significant increases (p 0.01)in VO2 (4.4 8.2%) and HR (3.6 7.3%) were observed for the MBT shoes compared with being barefoot. No significant differencesin VO2 and HR were recorded while walking around a 400 m track either with MBT shoes, weight-adjusted conventional shoesor barefoot. Nonetheless, a comparison of the MBT shoes with barefoot revealed a tendency for VO2 to be higher when wearingthe MBT shoes (7.1 6.5%, p 0.1) although HR was not significantly affected. Conclusions. The unstable shoe design predominantly effects oxygen consumption while standing, most likely due to increased muscle activity of the lower extremities.source: https://doi.org/10.7892/boris.65933 downloaded: 18.11.2021Key words: oxygen consumption, heart rate, unstable shoe construction, MBT (Masai Barefoot Technology)IntroductionShoes affect both standing and walking [1]. Theyinfluence gait, muscle activity, balance and the pressure distribution in the sole of the foot [2–5]. The MasaiBarefoot Technology (MBT) shoe has been describedas a training and therapeutic shoe that can be wornduring the normal course of the day [6]. The unstablenature of these shoes (Figure 1) is credited with stimulating musculature and sensorimotor activity in the lowerextremities. Built into the heel is a rounded sole, theso-called Masai Sensor. It introduces a destabilising effectin the anterio-posterior direction, i.e. the frontal plane,causing a rocking motion as it is very soft and thusresponsible for the instability. Additional muscular reflexes and activity compensate for this instability. According to the manufacturer, whole body posture isaffected as a consequence of this design.Several research institutes (University of Calgary,Universität Freiburg im Breisgau, Universität Salzburg)have already performed a wide gamut of studies examining the effects of such unstable shoe constructionon physiological and biomechanical responses. Nigget al. [7] examined the effects of varied shoe constructions on kinetic and kinematic variables and muscleactivity using EMG while standing and walking. Theyfound that muscle activity was elevated in all muscles* Corresponding author.** Both authors contributed equally to this study.160in the distal portion of the lower extremities, however,this result was significant only for the musculus tibialisanterior. Romkes [6] examined differences in muscleactivity patterns while walking with conventional andMBT shoes. This study found changes in muscle activity patterns in the talocalcaneal joint, in particular forthe musculus gastrocnemius and musculus tibialis anterior. Analysing the ability to control balance whilewearing these shoes, Romkes [5] examined the timecourse of the foot sole’s pressure points. While standing, significant differences were observed in the abilityto control balance in the anterio-posterior as well asthe medio-lateral directions while wearing the MBTshoes compared with being barefoot.Figure 1. Construction of MBT shoewith the characteristic rounded sole, the soft sensorand harder area for balancingBereitgestellt von Universitätsbibliothek BernAngemeldetHeruntergeladen am 02.04.15 10:47

HUMAN MOVEMENTB.A. Gasser et al., Shoe sole construction and oxygen consumptionWe are unaware of any study that has looked at differences in oxygen consumption between conventionaland MBT shoes during routine everyday movementssuch as standing and walking. Therefore, our study wasundertaken in an effort to gain better insight into energyexpenditure while wearing such an unstable shoe designand formulated the following hypotheses:Increased muscle activity caused by wearing MBTshoes should lead to an increase in metabolism andheart rate when compared with conventional shoeswhile standing.Increased muscle activity caused by wearing MBTshoes should lead to an increase in metabolism andheart rate when compared with conventional shoeswhile walking.Material and methodsThe study hypotheses were tested in three experiments: 1) laboratory conditions while standing, 2) laboratory conditions while walking on a treadmill and 3) fieldconditions while walking around a 400 m running track(Figure 2) when wearing different types of shoe designs(MBT shoe, conventional shoe, weight-adjusted conventional shoe) as well as without footwear (barefoot).All participants were healthy with an average levelof fitness. Ethical permission was sought and grantedby the Bernese Ethics Commission. For measurementswhile standing, six female and ten male participantswere recruited with mean age, height, mass values of29.8 6.8 years, 178 7 cm and 72.3 11.4 kg, respectively. Measurements while walking involved five femaleand eleven male participants with mean age, height andmass values of 32.8 7.5 years, 173 7 cm and 66.4 12.4 kg, respectively. Field measurements while walkinginvolved only five male participants with mean age,height and mass values of 29.7 3.1 years, 175 4 cmand 69.4 8.4 kg, respectively.Laboratory measurements taken while standing included oxygen consumption (Oxycon Alpha metaboliccart, Jäger, Germany) and heart rate (RS300X, Polar,Switzerland) Participants stood quietly for 6 min ina relaxed position. Participants were instructed to standon two marks on the floor placed 25 cm apart with feetparallel to each other. They were told to look straightahead and keep their arms to their sides. Measurementswere made while wearing the MBT shoe and conventional shoes. The order in which the shoes were wornwas randomised. When wearing the MBT shoes participants were instructed to balance their weight onthe rounded portion of the sole.Laboratory measurements while walking were performed on a PPS Sport treadmill (Woodway, Germany)at different speeds and inclines. Oxygen concentrationand heart rate were measured continuously, with thesame equipment as described above, and included thewarm-up. The order of phases 1–4 was randomised:Warm-up: 5 km · h–1 at no incline for 3 minPhase 1: 5 km · h–1 at no incline for 6 minPhase 2: 4 km · h–1 at 10% positive incline for 6 minPhase 3: 4 km · h–1 at 10% negative incline for 6 minPhase 4: 7 km · h–1 at no incline for 6 minThe walking phases were performed wearing theMBT and conventional shoes. In this test, the weightof the conventional shoes was adjusted to equal thatof the MBT shoes ( 5 g) using metal discs fixed with tape(Figure 3). The weights were fixed close to the ankle tooptimise inertia and torque and allow for maximalfreedom of movement. Phase 1 was also performedbarefoot by all participants.Field measurements were performed on a 400 m running track (Figure 2). Analogous to Phase 1 in the walkingtest, oxygen consumption (K4b2 gas analysis system,Cosmed, Italy) and heart rate (RS300X, Polar, Switzerland) were measured during a 6 min walk at 5 km · h–1.Figure 2. Field measurements of oxygen consumption and heart rate while walking in MBT, weight-adjustedand non-weight-adjusted conventional shoes as well as barefoot on the 400 m running trackBereitgestellt von Universitätsbibliothek BernAngemeldetHeruntergeladen am 02.04.15 10:47161

HUMAN MOVEMENTB.A. Gasser et al., Shoe sole construction and oxygen consumptionFigure 3. Weight-adjustment of conventional shoesThis was performed by all participants using the MBTshoe, the weight-adjusted conventional shoe (Figure 3)and while barefoot, all in randomised order. To ensurecorrect walking speed, the running track was markedevery 10 m and the participants were provided with anacoustic signal every 10 m to pace themselves. Their speedwas subsequently verified using a GPS device. Measurement of oxygen consumption and heart rate was continuous [8].Analysis of data was conducted using 30 s averagesof oxygen consumption and heart rate. The last 2 min ofeach measurement phase was used for statistical analysisto ensure steady-state had been reached [9, 10]. To avoidcalibration mistakes, all measurements were taken withoutinterruption including when participants changed shoes.All statistical analyses were performed using Mathematica software (Wolfram Research, USA). The percentdifference in oxygen consumption and heart rate werecompared between shoe types and barefoot, when applicable, using paired two-way t tests assuming homoscedasticity. For comparisons of the MBT shoe, conventional shoe and barefoot, an analysis of variance (ANOVA)was performed and with post-hoc Scheffé tests. As mentioned, the last 2 min of each measurement phase wasSignificant difference indicated by asterisk (p 0.01), line inbox indicates medianFigure 4. Oxygen consumption while standingin conventional (354 55 mL O2 · min–1)and MBT (387 64 mL O2 · min–1) shoes (n 16)162used for comparison. Gaussian distribution of the datawas checked using the Jarque–Bera test [11]. Statisticalsignificance was accepted at p 0.05, while values between0.05 and 0.1 were considered to indicate a tendency.ResultsThe first hypothesis, assessed in laboratory conditionswhile standing, was confirmed (Table 1). An increase inthe oxygen consumption rate (Figure 4) in the order of 9.3 5.2% (p 0.01) was recorded while standing in theMBT shoes compared with conventional shoes. Heartrate (Figure 5) was not significantly different (p 0.25).The second hypothesis, examined in laboratory conditions while walking, was not confirmed. No significant differences were observed in ANOVA while walkingwith the MBT, conventional shoes or barefoot (Table 1).Similarly, the second hypothesis when tested in fieldconditions was also not confirmed. No significant differences were noted while walking with the MBT or weightadjusted conventional shoes (Table 2). However, oxygenconsumption tended to be 7.1 6.5% (p 0.1) higherwhen wearing the non-weight-adjusted conventionalshoes and 5.9 5.6% (p 0.1) when barefoot. HeartNo significant difference (p 0.25), line in boxindicates medianFigure 5. Heart rate while standing in conventional(81 11 beats · min–1) and MBT (84 14 beats · min–1)shoes (n 16)Bereitgestellt von Universitätsbibliothek BernAngemeldetHeruntergeladen am 02.04.15 10:47

HUMAN MOVEMENTB.A. Gasser et al., Shoe sole construction and oxygen consumptionTable 1. Mean values ( SD) of oxygen consumption (VO2) and heart rate (HR) in laboratory conditions while walkingin MBT shoes, conventional sports shoes and barefoot 5 km · h–1 at zero incline (Phase 1), 4 km · h–1 at 10% positive incline(Phase 2), 4 km · h–1 at 10 % negative incline (Phase 3) and 7 km · h–1 at zero incline (Phase 4)VO2 (mL O2 · min–1)MBT (n 16)Conventional (n 16)Barefoot (n 16)Phase 1Phase 2Phase 3Phase 41025 221.61497 251.4647 1131695 256.71070 156.11512 235.7650 115.61640 238.1981 176.1HR (beats · min–1)MBT (n 16)Conventional (n 16)Barefoot (n 16)99 12.7113 14.186 10.6124 19.998.1 176.1Phase 1Phase 2Phase 3Phase 499 10.3114 15.288 14.9124 18SchefféPhase 1 6730.947pConventionalBarefootBarefootSchefféPhase 1 onalBarefootBarefoot0.990.7130.631Table 2. Mean values ( SD) of oxygen consumption (VO2) and heart rate (HR) in field conditionswhile walking in MBT shoes, conventional sports shoes and barefoot on a 400 m running track at 5 km · h–1VO2 (mL O2 · min–1) n 5Test ShoeConventionalBarefoot881 87.1872 50.5823 32.2ANOVA FVO2 nalBarefootBarefoot0.9780.360.464Difference in VO2 (mL O2 · min–1)Test Shoe vs. barefootConventional vs. barefoot7.1 6.5%5.9 5.6%HR (beats min–1) n 5Test ShoeConventionalBarefoot86 1984 17.183 17.3ANOVA FHR (beats · min–1) alBarefootBarefoot0.9870.970.996Bereitgestellt von Universitätsbibliothek BernAngemeldetHeruntergeladen am 02.04.15 10:47163

HUMAN MOVEMENTB.A. Gasser et al., Shoe sole construction and oxygen consumptionrate increased when wearing the MBT shoes by 3.6 3.8% compared with the weight-adjusted conventionalshoes and by 1.0 1.6% when barefoot. However, thesedifferences were not statistically significant (p 0.55and p 0.15, respectively).DiscussionHettinger and Müller [1] quantified the effects of shoemass on oxygen consumption, finding that the additionalmass of shoes did result in increased oxygen consumption. In the present study, the increase in oxygen consumption while wearing shoes, compared with beingbarefoot, was of a similar magnitude to that measured byHettinger and Müller. Thus, any increase in VO2 seenwhile wearing the MBT shoes is more likely attributableto the sheer weight of the shoe rather than the unstablesole design.A comparison of the absolute oxygen consumptionvalues between the laboratory (1025 221.6) and field(881 87.1) measurements while walking horizontally at5 km · h–1 revealed a higher value at 144 mL O2 · min–1,or approximately 14%, for walking on the treadmill.Statistically, this result was not significant. Nonetheless,one possible explanation for this result may be that theparticipants were not familiar with walking on a movingtreadmill, thus resulting in increased muscular activity.An increase in oxygen consumption was readilyobservable when standing in the MBT shoes with theunstable sole construction. It can be surmised that thisincrease in load is a result of interplay between jointgeometry, increased muscular stabilisation and externalforces [3, 5, 6, 8]. The cumulative effects may becomemore pronounced when standing for long durations,although the changes would probably only be in therange of 20 J · h–1 [12]. Nonetheless, any increase in muscular activity is welcomed for a number of reasons, including enhanced venous return from the legs via themuscular pump and the enhanced segmental stabilisation of the spinal column through the activation of reflex arcs.The significant increase in oxygen consumption whilestanding in the MBT shoes can also be credited to increased sensorimotor activity such as muscular reflexesand the maintenance of muscle tone, tentatively asa consequence of the shoe’s design. The absolute difference between the two shoe types is small however, particularly given the high variability (see SD values inTable 1). Nevertheless, our measurements recorded a definite increase in oxygen consumption while standingin the MBT shoe (Figure 4). Our data correlate well withthe biomechanical studies of Nigg and Wakeling [7]and Romkes [6], which found increased EMG activitywhen wearing similar shoes while standing. As such,our data can be viewed to metabolically correlate theexisting biomechanical evidence. A calculation of intertest reliability resulted in a value of 0.92 for the meas164urements while standing, which, according to Bös [13],indicates exceptional reliability and supports the validityof the results.With respect to heart rate, a difference of 3 beats · min–1was found between the MBT (84 14 beats · min –1)and conventional shoes (81 11 beats · min–1) when standing, although this result was not statistically significant (Figure 5). The lack of significant changes in heart ratemay be due to the fact that, at lower heart rates, the portion of the stroke volume supplying blood to the skeletalmusculature is only very small [12] and any increaseat this intensity would go largely unnoticed. The relationship between oxygen consumption and heart ratealters with changing intensity [5], where previous studieshave shown that the relationship between oxygen consumption and heart rate at low intensity (e.g. lying,sitting, standing) is very weak [14–16]. This relationshipis much stronger and is linearly proportional at mid tohigh intensities. At low intensities, changes can occur inheart rate without any corresponding change in oxygenconsumption. At rest, Spurr et al [17] found that anincrease in heart rate from 60 to 80 beats · min–1 did notshow corresponding differences in oxygen consumption.Another reason for the discrepancies between heartrate and oxygen consumption may be the stimulationof the heart via the sympathetic nervous system dueto psychological stimulation [18]. Steady-state oxygenconsumption is relatively stable compared with heartrate, which can vary significantly due to changes in strokevolume, peripheral resistance, blood distribution andmental state. Unlike blood, oxygen cannot be storedin the vascular system. The absolute difference in VO2(33 mL O2 · min–1) measured in our study was checked using a linear regression and was equivalent to 1.13 beats· min–1. Thus, in contrast to the oxygen consumptionrate, we expect that heart rate at low intensities, i.e.when standing, is too variable and the changes due towearing the MBT shoes too small to have significantlyaffected heart rate.No significant differences were observed betweenthe MBT shoes and weight-adjusted conventional shoesin any of the walking phases on the treadmill. Thesedata were in accord with the field measurements whichalso found no significant differences between the MBTand weight-adjusted conventional shoes. Thus, we conclude that walking in shoes with an unstable sole construction or shoes with a conventional flat sole has noeffect on oxygen consumption. Walking on the treadmill with either the MBT or conventional shoes did,however, cause an increase in oxygen consumption andheart rate compared with walking barefoot. This tendency, although not statistically significant, was alsoobserved in the field measurement data, where a poweranalysis suggests that a higher number of participantscould strengthen such a conclusion.Bereitgestellt von Universitätsbibliothek BernAngemeldetHeruntergeladen am 02.04.15 10:47

HUMAN MOVEMENTB.A. Gasser et al., Shoe sole construction and oxygen consumptionConclusionsOur study allows for the suggestion that the unstableshoe sole construction of the MBT shoe could producepositive therapeutic effects in people who spend a highproportion of time standing. We expect that such a shoesole design could provide the best preventive effect whenused as early as possible. With an increased prevalenceof lifestyle diseases such as obesity and diabetes as wellas vascular diseases such as peripheral artery occlusivedisease or chronic venous insufficiency, the end manifestations of such disease states (e.g. polyneuropathy)have also increased. A consequence of this is that theever-more serious clinical manifestations of peripheralneuropathy, most particularly in the distal part of thelower extremities, are occurring more often and ata younger age, leading to increases in the number ofsurgical interventions. Regular wearing of shoes withunstable sole construction may have positive therapeutic effects by targeted activation of the lower legmuscles, in particular, the smaller foot muscles. Future studies should evaluate the usefulness of unstableshoe construction in preventing the above ledgementsWe wish to thank Dr. Dino W. Schlamp and Dr. Gregor Bäurlefor their constructive comments. The study was internallyfunded by a research grant from the University of Bern. Themanufacturer of the unstable shoes (Masai Barefoot Technology) declared bankruptcy in May 2012. The authors declareno conflict of interest. This study was conducted independently, none of the authors were in any way employed orrewarded by Masai Barefoot Technology and the presentedresults were not influenced by the manufacturer.15.References17.1. Hettinger T., Müller E.A., Der Einfluss des Schuhgewichtes auf den Energieumsatz beim Gehen und Lastentragen. Arbeitsphysiologie, 1953, 15, 33–40.2. 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Economic Letters, 1980, 6 (3), 255–259, doi:10.1016/0165-1765(80)90024-5.Silbernagel S., Taschenatlas der Physiologie. 6 Auflage.Thieme, Berlin 2000, 228–231.Bös K. (Hrsg.), Handbuch Motorische Tests: Sportmotorische Tests, Fragebogen zur körperlich-sportlichenAktivität und sportpsychologische Diagnoseverfahren(2. vollständig überarbeitete und erweiterte Auflage).Hogrefe, Göttingen 2001, 103–105.Emons H.J.G., Groenenboom D.C., Westerterp K.R.,Saris W.H.M., Comparison of heart rate monitoring combines with indirect calorimetry and the doubly labelledwater (2H 2 18O) method for the measurement of energyexpenditure in children. Eur J Appl Physiol, 1992, 65 (2),99–103, doi: 10.1007/BF00705064.Hiilloskorpi H.K., Pasanen M.E., Fogelholm M.G., Laukkanen R.M., Mänttäri A.T., Use of heartrate to predictenergy expenditure from low to high activity levels. 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Dissertationan der Fakultät für Kulturwissenschaften, UniversitätBayreuth 2005.Paper received by the Editor: June 18, 2014Paper accepted for publication: October 7, 2014Correspondence addressDr. med Benedikt GasserSwiss Health & Performance LabInstitute of AnatomyUniversity of BernBaltzerstrasse 2CH-3012 Bern, Switzerlande-mail: [email protected] von Universitätsbibliothek BernAngemeldetHeruntergeladen am 02.04.15 10:47165

2 and H r were recorded while walking around a 400 m track either with MBT shoes, weight-adjusted conventional shoes or barefoot. Nonetheless, a comparison of the MBT shoes with barefoot revealed a tendency for VO 2 to be higher when wearing the MBT shoes (7.1 6.5%, p 0.1) although Hr was not significantly affected. Conclusions.