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Comparison of Pelvic Complex Kinematics During Treadmill and Overground Walking

Published:February 27, 2012DOI:https://doi.org/10.1016/j.apmr.2011.10.022

      Abstract

      Chockalingam N, Chatterley F, Healy AC, Greenhalgh A, Branthwaite HR. Comparison of pelvic complex kinematics during treadmill and overground walking.

      Objectives

      To determine if there are changes in temporal gait parameters with a focus on pelvis when comparing overground and treadmill ambulation, and to assess the effect of sex.

      Design

      An observational study employing motion analysis techniques to evaluate pelvic movement during gait.

      Setting

      University biomechanics laboratory.

      Participants

      Men (n=8; 22.5±3.0y) and women (n=6; 23.8±4.1y).

      Interventions

      Not applicable.

      Main Outcome Measures

      Cadence, stride time, stance phase percent, and pelvic tilt, obliquity, and rotation parameters throughout the gait cycle were assessed during overground and treadmill walking. Kinematic data were recorded using a passive full body marker based motion analysis system. While an independent sample t test was used to determine if differences in walking speed were evident between sexes, a 2-way, repeated-measures analysis of variance was performed to examine the effect of walking mode and sex on each dependent variable.

      Results

      Significant differences (P<.05) between overground and treadmill walking for the temporal parameters analyzed were evident for both sexes. A lower pelvic obliquity motion for treadmill walking when compared with overground walking was evident for both sexes, and the pelvic rotation movement pattern showed the greatest difference between walking modes. The majority of the significant differences between sexes were of a magnitude greater than the differences between overground and treadmill walking.

      Conclusions

      The differences in temporal and angular kinematics identified in the present study should be considered when treadmills are used in a rehabilitation program.

      Key Words

      PATHOLOGIC GAIT relates to deviation from the normative patterns of movement. Abnormal gait patterns could be the result of disorders of the brain, spinal cord, nerves, muscles, joints, and skeleton.
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      Gait analysis is an important aspect of assessment in clinical evaluation of gait disturbances and in rehabilitation. Gait analysis protocol within a clinical setting commonly employs a treadmill. The proposed benefits of using treadmills instead of overground walking include less space being required, control over speed and gradient, fewer cameras needed for motion analysis, the capacity to use controlled protocol to assess ability to adapt to changes in speed and surface slope, less data collection time, the ability to use harnesses to support body weight, and simultaneous recording of other data such as an electromyogram and metabolic costs.
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      Many studies have compared the biomechanics of gait when walking overground and on a treadmill; however, with inconsistent findings, the relationship between the 2 modes is not clear. Temporospatial parameters commonly used in gait analysis include walking speed, stride time and length, step time and length, and finally durations of stance and swing phase.
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      However, Matsas et al
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      Knee joint kinematics from familiarised treadmill walking can be generalised to overground walking in young unimpaired subjects.
      only found significant differences between the 2 modes of walking for the first 4 minutes of data collection; at 6 minutes no significant differences were evident. Additionally, Greig,
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      and colleagues reported no differences in gait parameters. Conflicting findings for differences in electromyogram recordings between overground and treadmill walking also exist within the literature.
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      The introduction of the instrumented treadmill has allowed researchers to compare ground reaction forces for treadmill and overground walking.
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      Although Riley et al
      • Riley P.O.
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      • Paylo K.W.
      • Kerrigan D.C.
      A kinematic and kinetic comparison of overground and treadmill walking in healthy subjects.
      found significant differences in ground reaction force maxima, because these differences were comparable with the variability in normative gait parameters, they concluded that the mechanics of both modes were similar. Conversely, White et al
      • White S.C.
      • Yack H.
      • Tucker C.A.
      • Lin H.Y.
      Comparison of vertical ground reaction forces during overground and treadmill walking.
      reported differences in force magnitude between overground and treadmill walking during mid and late stance, and Lee and Hidler
      • Lee S.J.
      • Hidler J.
      Biomechanics of overground vs. treadmill walking in healthy individuals.
      reported differences in sagittal plane joint moments.
      Previous research on gait kinematics has also found conflicting results, with some reporting differences
      • Alton F.
      • Baldey L.
      • Caplan S.
      • Morrissey M.
      A kinematic comparison of overground and treadmill walking.
      • Riley P.O.
      • Paolini G.
      • Della Croce U.
      • Paylo K.W.
      • Kerrigan D.C.
      A kinematic and kinetic comparison of overground and treadmill walking in healthy subjects.
      • Murray M.
      • Spurr G.
      • Sepic S.
      • Gardner G.
      • Mollinger L.
      Treadmill vs. floor walking: kinematics, electromyogram, and heart rate.
      • Tulchin K.
      • Orendurff M.
      • Karol L.
      A comparison of multi-segment foot kinematics during level overground and treadmill walking.
      and others not.
      • Parvataneni K.
      • Ploeg L.
      • Olney S.J.
      • Brouwer B.
      Kinematic, kinetic and metabolic parameters of treadmill versus overground walking in healthy older adults.
      • Matsas A.
      • Taylor N.
      • McBurney H.
      Knee joint kinematics from familiarised treadmill walking can be generalised to overground walking in young unimpaired subjects.
      • Lee S.J.
      • Hidler J.
      Biomechanics of overground vs. treadmill walking in healthy individuals.
      • Nymark J.R.
      • Balmer S.J.
      • Melis E.H.
      • Lemaire E.D.
      • Millar S.
      Electromyographic and kinematic nondisabled gait differences at extremely slow overground and treadmill walking speeds.
      While some researchers have found significant differences in joint angles they considered these irrelevant in their reports due to their magnitude (<3°).
      • Riley P.O.
      • Paolini G.
      • Della Croce U.
      • Paylo K.W.
      • Kerrigan D.C.
      A kinematic and kinetic comparison of overground and treadmill walking in healthy subjects.
      • Tulchin K.
      • Orendurff M.
      • Karol L.
      A comparison of multi-segment foot kinematics during level overground and treadmill walking.
      On the contrary, Watt et al
      • Watt J.R.
      • Franz J.R.
      • Jackson K.
      • Dicharry J.
      • Riley P.O.
      • Kerrigan D.C.
      A three-dimensional kinematic and kinetic comparison of overground and treadmill walking in healthy elderly subjects.
      reported reductions in the majority of joint angles during treadmill walking; however, of the 12 parameters where significant differences were evident, only 2 were of a magnitude greater than 3°. These conflicting interpretations of results among researchers make it difficult to conclude whether differences between the 2 modes are present or not.
      Another confounding factor that may affect the identification of differences between treadmill and overground walking is the age of study participants. While Riley et al
      • Riley P.O.
      • Paolini G.
      • Della Croce U.
      • Paylo K.W.
      • Kerrigan D.C.
      A kinematic and kinetic comparison of overground and treadmill walking in healthy subjects.
      found no differences between the conditions for young participants, Wass et al
      • Wass E.
      • Taylor N.F.
      • Matsas A.
      Familiarisation to treadmill walking in unimpaired older people.
      found that older people were unsuccessful in familiarizing themselves with treadmill walking after 15 minutes. In addition, Greig et al
      • Greig C.
      • Butler F.
      • Skelton D.
      • Mahmud S.
      • Young A.
      Treadmill walking in old age may not reproduce the real life situation.
      reported higher heart rates in older adults when they walked on treadmills than when they walked overground, even after they had undertaken familiarization sessions, and no difference in young people.
      Although there are a number of studies that have examined differences in joint kinematics between overground and treadmill walking, the majority of these have focused on the ankle, hip, and knee joints with few assessing the role of the pelvis,
      • Riley P.O.
      • Paolini G.
      • Della Croce U.
      • Paylo K.W.
      • Kerrigan D.C.
      A kinematic and kinetic comparison of overground and treadmill walking in healthy subjects.
      • Watt J.R.
      • Franz J.R.
      • Jackson K.
      • Dicharry J.
      • Riley P.O.
      • Kerrigan D.C.
      A three-dimensional kinematic and kinetic comparison of overground and treadmill walking in healthy elderly subjects.
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      A comparison of overground and treadmill running for measuring the three-dimensional kinematics of the lumbo-pelvic-hip complex.
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      Comparison of angular lumbar spine and pelvis kinematics during treadmill and overground locomotion.
      which plays an important role in walking. The movement pattern of the pelvis can be affected by conditions such as leg length inequality, increased lumbar lordosis, and trunk bending (lateral, anterior, and posterior).
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      The effect of leg length discrepancy on spinal motion during gait: three-dimensional analysis in healthy volunteers.
      The pelvis is an important element in human locomotion, which not only influences the pathomechanics of the low back and the hip but also contributes to postural stability.
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      • Banzer W.
      Lumbar corsets: their effect on three-dimensional kinematics of the pelvis.
      Furthermore, the pelvis plays an important role in the control of walking velocity. While it is beyond the scope of this article to describe the fundamental pelvic movement during gait and it is described elsewhere,
      • Whittle M.
      Gait analysis: an introduction.
      a previous study examined the effects of a lumbar corset on pelvic kinematics using a treadmill with results indicating significant differences in the frontal plane.
      • Vogt L.
      • Portscher M.
      • Banzer W.
      Lumbar corsets: their effect on three-dimensional kinematics of the pelvis.
      Of the limited research to date that has examined pelvic movement, none has examined whether sex has an effect on pelvic movement, even though pelvic range of motion has been shown to be affected by sex.
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      Age, gender and speed effects on spinal kinematics during walking.
      Additionally, because Alton et al
      • Alton F.
      • Baldey L.
      • Caplan S.
      • Morrissey M.
      A kinematic comparison of overground and treadmill walking.
      found that sex had an effect on hip and knee kinematics during treadmill and overground walking, it is necessary to quantify whether differences occur at the pelvis.
      While looking at the sex differences in the variability of gait parameters at 4 different speeds, a previous study
      • Barrett R.
      • Noordegraaf M.V.
      • Morrison S.
      Gender differences in the variability of lower extremity kinematics during treadmill locomotion.
      indicated that there are no differences in basic gait parameters such as stride length and stride time. In general, the women exhibited lower variability than men for various joint rotations. This was more evident in higher gait speed. However, Barrett et al
      • Barrett R.
      • Noordegraaf M.V.
      • Morrison S.
      Gender differences in the variability of lower extremity kinematics during treadmill locomotion.
      suggest that the sex differences in variability may not be consistent across different levels of the motor system. Therefore, the purpose of the present preliminary study was to determine if differences in temporal values and angular parameters in the pelvic complex occur, when comparing overground and treadmill ambulation. This information will provide data that can be used in designing protocols for clinical intervention, as well as baseline normative data for future research. Additionally, this study will investigate if sex differences are evident in basic temporal gait parameters and/or in pelvic complex parameters.
      It was hypothesized that there would be differences in angular parameters between men and women in the 2 modes of walking, but that there would be no differences in temporal measures.

      Methods

      Participants

      A convenience sample consisting of 8 men and 6 women were recruited from a group of university students (participant demographics shown in table 1). Ethical approval was sought and received from the university ethics committee. All participants signed an informed consent form before participating in the study. All participants were familiar with treadmill walking and reported no known musculoskeletal pathologies. All participants wore their own gym shoes and appropriate clothing to allow for marker placements on anatomical landmarks.
      Table 1Participant Demographics
      DemographicsMen (n=8)Women (n=6)
      Age (y)22.5±3.023.8±4.1
      Mass (kg)75.0±6.059.2±4.4
      Height (cm)183.7±6.9168.0±5.7
      NOTE. Values are expressed as mean ± SD.

      Equipment

      The study was conducted in a gait laboratory with a walkway of 9m. Timing gates were used to establish overground walking speed, with this speed then used to set the speed for the treadmill.a Kinematic data were recorded using a motion analysis systemb with 8 cameras viewing a calibrated space of 4.0×4.0×1.8m, operating at a sampling rate of 200Hz.

      Data Collection

      Anthropometric data were recorded for each participant, and reflective markers were positioned by the same researcher (F.C.), using a whole body marker set (Plug-in gaitb). Calibration was undertaken for each participant using a static trial. A 9-m-long walkway with the 4- to 8-m section used for data collection was set up overground, and participants were instructed to walk with normal cadence. Timing gatesc were used to record the participants' preferred walking speeds and were subsequently used to control for speed between trials. Kinematic data were recorded over 3 seconds to allow for capture of 1 full gait cycle, and 10 trials for each participant were recorded. Each participant performed first overground and then treadmill walking on the same day to avoid reapplication of markers. The treadmill was positioned in the same direction as the walkway. For each participant, the treadmill was set to his/her personal average speed calculated from the overground walking. The participants walked for a minimum of 1 minute before each trial, and 10 trials of 3-second duration were captured for analysis. For the purpose of clarity, the following terminology was employed: forward or backward tilting of the pelvis was described as pelvic tilt, lateral tilting of the pelvis was described as pelvic obliquity, and turning of the pelvis was described as rotation.

      Data Processing and Analysis

      Gait parameters for heel strike and toe off were identified for both left and right feet by frame analysis. When identifying foot contacts, the downward velocity of the heel marker and the footwear and skeletal loading were taken into account.
      • Schache A.G.
      • Blanch P.D.
      • Rath D.A.
      • Wrigley T.V.
      • Starr R.
      • Bennell K.L.
      A comparison of overground and treadmill running for measuring the three-dimensional kinematics of the lumbo-pelvic-hip complex.
      Similarly, toe off was identified by analysis of the vertical displacement of the toe marker. Mean values for cadence, stride time, stance phase (% of gait cycle), and various pelvic angles (table 2 lists the angular parameters) were calculated for all the participants in both overground and treadmill conditions. The angular parameters used were adapted from previous related studies.
      • Schache A.G.
      • Blanch P.D.
      • Rath D.A.
      • Wrigley T.V.
      • Starr R.
      • Bennell K.L.
      A comparison of overground and treadmill running for measuring the three-dimensional kinematics of the lumbo-pelvic-hip complex.
      • Benedetti M.
      • Catani F.
      • Leardini A.
      • Pignotti E.
      • Giannini S.
      Data management in gait analysis for clinical applications.
      Table 2Angular Parameters Measured
      Pelvic MovementParameter (degrees)
      TiltInitial contact angle
      Toe-off angle
      ObliquityInitial contact angle
      First maximum upward angle
      Toe-off angle
      Second maximum downward angle
      RotationInitial contact angle
      Toe-off angle
      Data were entered into SPSS version 17.0d for statistical analysis. An independent samples t test was used to determine if walking speed was affected by sex. A 2-way analysis of variance was performed to examine the effect of walking mode (overground and treadmill) and sex on each dependent variable (gait and angular parameters).

      Results

      Table 3 provides values and statistical results for the temporal parameters, and table 4 details the results of pelvic angle differences. Fig 1, Fig 2, Fig 3 represent the movement of the pelvis in the 3 planes for women and men during overground and treadmill walking. Any sex differences in temporal and kinematic parameters were not affected by the participant's self-selected walking speed because no significant difference between sexes for walking speed was evident (t12=1,12; P=.285).
      Table 3Temporal Parameter Values and Results for Statistical Comparisons
      VariableGroupOvergroundTreadmillComparison (P)
      Men vs WomenOverground vs TreadmillSex × Walking Mode
      Cadence (steps/min)Women115.82±5.88101.74±5.65.081<.001
      Significant difference (P<.05).
      .100
      Men114.24±5.8296.42±5.63
      Stride time (s)Women1.03±0.051.18±0.07.037
      Significant difference (P<.05).
      <.001
      Significant difference (P<.05).
      .115
      Men1.05±0.051.25±0.08
      Stance phase (% of gait cycle)Women62.17±1.2068.81±1.28.833<.001
      Significant difference (P<.05).
      .020
      Significant difference (P<.05).
      Men62.94±2.0067.85±0.92
      NOTE. Values are mean ± SD or as otherwise indicated.
      low asterisk Significant difference (P<.05).
      Table 4Pelvic Angle Parameter Values and Results for Statistical Comparisons
      Pelvic MovementParameter (degrees)GroupOvergroundTreadmillComparison (P)
      Men vs WomenOverground vs TreadmillSex × Walking Mode
      TiltInitial contact angleWomen10.73±4.659.62±5.06.194.767.006
      Significant difference (P<.05).
      Men7.50±3.538.85±3.30
      Toe-off angleWomen9.67±4.418.65±5.10.046
      Significant difference (P<.05).
      .629.025
      Significant difference (P<.05).
      Men5.88±2.836.55±2.90
      ObliquityInitial contact angleWomen0.80±1.630.06±1.67.893.097.087
      Men−0.49±1.880.46±1.77
      First maximum upward angleWomen6.84±2.284.35±2.09.001
      Significant difference (P<.05).
      <.001
      Significant difference (P<.05).
      .236
      Men3.64±1.751.99±2.13
      Toe-off angleWomen−4.58±2.57−4.29±2.04.004
      Significant difference (P<.05).
      .858.521
      Men−2.14±1.83−2.30±1.80
      Second maximum downward angleWomen−6.58±2.15−4.35±2.06.001
      Significant difference (P<.05).
      <.001
      Significant difference (P<.05).
      .027
      Significant difference (P<.05).
      Men−3.49±1.80−2.56±1.78
      RotationInitial contact angleWomen5.01±2.380.91±2.81.138<.001
      Significant difference (P<.05).
      .548
      Men4.05±2.36−0.66±2.57
      Toe-off angleWomen−2.89±1.89−2.32±1.88.783.010
      Significant difference (P<.05).
      .175
      Men−3.27±1.98−1.55±2.57
      NOTE. Values are mean ± SD or as otherwise indicated.
      low asterisk Significant difference (P<.05).
      Figure thumbnail gr1
      Fig 1Gait cycle pattern for men and women's pelvic tilt when walking overground and on a treadmill for the (A) left and (B) right sides.
      Figure thumbnail gr2
      Fig 2Gait cycle pattern for men and women's pelvic obliquity when walking overground and on a treadmill for the (A) left and (B) right sides.
      Figure thumbnail gr3
      Fig 3Gait cycle pattern for men and women's pelvic rotation when walking overground and on a treadmill for the (A) left and (B) right sides.

      Temporal Parameters

      A significant difference (P<.05) was evident between sexes for stride time only, with women exhibiting a shorter stride time when compared with men. When comparing overground with treadmill walking, significant differences were identified for the mean temporal parameter conditions, with a lower cadence and longer stride time and stance phase. Additionally, the interaction between sex and walking mode for stance phase reached significance, with women spending a smaller proportion of the gait cycle in stance phase when compared with men for the overground condition and a larger proportion for the treadmill condition.

      Pelvic Angle Parameters

      Women generated a significantly greater pelvic tilt angle at toe off than men. The interaction between sex and walking mode for this parameter also reached significance, with women reducing this angle when treadmill walking and men increasing this angle. Furthermore, an interaction effect for pelvic angle at initial contact was evident with the same findings as toe off (ie, women reduced this angle when treadmill walking whereas men increased it). Although the general movement pattern for pelvic tilt did not appear to change a great deal for women between walking modes, for men, while the magnitude of the range of movement remained constant, there was an increase in anterior tilt of approximately 2° throughout the gait cycle for treadmill walking (see fig 1).
      Significant differences (P<.05) were evident between sexes for 3 of the 4 pelvic obliquity angles, with women generating greater pelvic obliquity motion. When walking mode was compared, significantly lower maximum upward and downward obliquity were evident when participants walked on a treadmill. A significant interaction effect for the second maximum downward angle indicated that sex had a greater effect on overground walking than on treadmill walking. Additionally, men were found to have their pelvis in a slightly upward pelvic obliquity position at initial contact for treadmill walking but a slightly downward pelvic obliquity position for overground walking (see fig 2).
      For both pelvic rotation parameters, there was a significant effect for walking mode but no effect for sex. At initial contact the internal rotation was lower during treadmill walking than during overground walking, with the women approaching a more neutral rotation position and the men a slight externally rotated position. Furthermore, a lower external rotation at toe off during treadmill walking was evident. The general pelvic rotation movement pattern employed by both sexes for overground walking appears to be considerably different than the movement pattern for treadmill walking (see fig 3). After initial contact the pelvis remained in internal rotation for a greater percentage of the gait cycle in treadmill walking, and the maximum external rotation angle also occurred later in the gait cycle.

      Discussion

      With the overall objective of determining the differences in temporal and angular parameters in the pelvic complex when comparing overground and treadmill ambulation, this study also examined the temporal gait parameter differences between men and women. The reported results provide normative data to inform further studies in this area and will help in designing protocols for clinical intervention.

      Temporal Parameters

      While previous research has found sex differences in temporal gait parameters,
      • Blanc Y.
      • Balmer C.
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      • Vingerhoets F.
      Temporal parameters and patterns of the foot roll over during walking: normative data for healthy adults.
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      • Karsznia A.
      • Öberg K.
      Basic gait parameters: reference data for normal subjects, 10-79 years of age.
      with women tending to have a higher cadence than men, in the present study sex differences were only evident for stride time. Treadmill cadence was found to be less (12% for women and 16% for men) than the cadence performed overground. This is in conflict with previous research, in which the cadence values were found to increase while walking on the treadmill
      • Alton F.
      • Baldey L.
      • Caplan S.
      • Morrissey M.
      A kinematic comparison of overground and treadmill walking.
      • Warabi T.
      • Kato M.
      • Kiriyama K.
      • Yoshida T.
      • Kobayashi N.
      Treadmill walking and overground walking of human subjects compared by recording sole-floor reaction force.
      ; however, no change in cadence between these walking modes has also been reported.
      • Riley P.O.
      • Paolini G.
      • Della Croce U.
      • Paylo K.W.
      • Kerrigan D.C.
      A kinematic and kinetic comparison of overground and treadmill walking in healthy subjects.
      A possible reason for these conflicting reports could be the ability of treadmills to maintain a constant belt velocity, because body mass has been found to affect belt velocity.
      • Savelberg H.H.
      • Vorstenbosch M.A.
      • Kamman E.H.
      • van de Weijer J.G.
      • Schambardt H.C.
      Intra-stride belt-speed variation affects treadmill locomotion.
      Stride time was found to increase (15% for women and 19% for men) during treadmill walking in comparison with overground walking, with both within the normative range previously reported.
      • Craik R.L.
      • Dutterer L.
      Spatial and temporal characteristics of foot fall patterns.
      For stance phase, treadmill values were significantly greater (11% for women and 8% for men) than overground values. This finding in the present study adds to the inconsistent results for stance phase in the literature, with some researchers reporting no difference in stance phase between treadmill and overground walking
      • Murray M.
      • Spurr G.
      • Sepic S.
      • Gardner G.
      • Mollinger L.
      Treadmill vs. floor walking: kinematics, electromyogram, and heart rate.
      and others reporting a decrease in stance phase with treadmill walking.
      • Alton F.
      • Baldey L.
      • Caplan S.
      • Morrissey M.
      A kinematic comparison of overground and treadmill walking.
      • Warabi T.
      • Kato M.
      • Kiriyama K.
      • Yoshida T.
      • Kobayashi N.
      Treadmill walking and overground walking of human subjects compared by recording sole-floor reaction force.
      However, the values reported within the current study concur with a previous study that recorded stance phase as being 69% of the gait cycle for an age range of 20 to 29 years for a group of women and men during treadmill walking.
      • Jansen E.C.
      • Vittas D.
      • Hellberg S.
      • Hansen J.
      Normal gait of young and old men and women: ground reaction force measurement on a treadmill.
      Moreover, the stance phase percentage values reported in the present study follow other research evaluating running on a treadmill, where treadmill running is associated with an increased stance period.
      • Schache A.G.
      • Blanch P.D.
      • Rath D.A.
      • Wrigley T.V.
      • Starr R.
      • Bennell K.L.
      A comparison of overground and treadmill running for measuring the three-dimensional kinematics of the lumbo-pelvic-hip complex.
      The variation in the temporal values could possibly be attributed to differences in heel contact and toe-off identification. The current study looked at the displacement of the heel and toe markers using frame-by-frame analysis to identify stance phase. Although this was performed by just one experienced researcher (F.C.), this may have been a source of error. However, previous research has found the reliability of visual identification when compared with footswitches and force plates to be high.
      • Wall J.
      • Crosbie J.
      Accuracy and reliability of temporal gait measurement.
      The results also demonstrate that the stance phase component of the overall gait cycle in women is lower than that in men for the overground condition. However, it is shown to be higher while walking on the treadmill. When compared with previous research,
      • Barrett R.
      • Noordegraaf M.V.
      • Morrison S.
      Gender differences in the variability of lower extremity kinematics during treadmill locomotion.
      which indicated no significant differences in treadmill locomotion between the sexes, the current study shows differences, which warrant further detailed investigation. This will be particularly relevant while planning treadmill-based treatment intervention.

      Pelvic Angle Parameters

      Sex comparisons highlighted that women's anterior pelvic tilt angle was greater during toe off than men's anterior pelvic tilt angle. Examination of the pelvic tilt movement pattern during gait (see fig 1) indicated the diverse adaptation to the modes of walking undertaken by men and women. Similarly, the toe-off pelvic downward obliquity angle was greater in women than men. These differences in the pelvic movement during the toe-off phase have not been reported previously. The maximum upward and downward obliquity of the pelvis during gait was significantly reduced during treadmill walking, which is in accordance with previous research.
      • Vogt L.
      • Pfeifer K.
      • Banzer W.
      Comparison of angular lumbar spine and pelvis kinematics during treadmill and overground locomotion.
      Clinically, excessive pelvic obliquity is caused by leg length inequality, among other things.
      • Winter R.B.
      • Carvalho P.
      Pelvic obliquity: its causes and its treatment.
      The reported reduction in obliquity might favor the use of treadmill in treatment interventions in which reduced obliquity is desirable.
      Women's pelvic obliquity maximum upward and second maximum downward angles were significantly greater than the men's. While the values reported in the present study for pelvic range of motion are similar to those presented by Crosbie et al,
      • Crosbie J.
      • Vachalathiti R.
      • Smith R.
      Age, gender and speed effects on spinal kinematics during walking.
      they reported no significant difference between sexes at self-selected walking speed. A possible reason for this difference is the age range of the study participants, because age has been shown to affect pelvic movement.
      • Thurston A.
      • Harris J.
      Normal kinematics of the lumbar spine and pelvis.
      Crosbie
      • Crosbie J.
      • Vachalathiti R.
      • Smith R.
      Age, gender and speed effects on spinal kinematics during walking.
      used a much wider age range of participants (range, 20–50y) than the present study (range, 18–28y).
      Pelvic rotation angles were most affected by the walking condition with the greatest difference in both movement magnitude and pattern. Pelvic rotation at initial contact was significantly less with walking on the treadmill than with overground walking for both sexes, with this decrease being of the greatest magnitude of all the significant differences (4.7° for men and 4.1° for women). In addition, a lower pelvic rotation was evident at toe off for treadmill walking. There was a large decrease (46% for men and 48% for women) in the pelvic rotation range of motion during gait for overground (8.9° for men and 10.1° for women) and treadmill (4.8° for men and 5.3° for women) walking, which is again consistent with research carried out by Vogt et al.
      • Vogt L.
      • Pfeifer K.
      • Banzer W.
      Comparison of angular lumbar spine and pelvis kinematics during treadmill and overground locomotion.
      Vogt
      • Vogt L.
      • Pfeifer K.
      • Banzer W.
      Comparison of angular lumbar spine and pelvis kinematics during treadmill and overground locomotion.
      suggested that this reduction in pelvic movement during treadmill walking may be attributed to stiffness in the kinematic chain.
      In a group of low back pain patients, a previous study,
      • Gombatto S.P.
      • Collins D.R.
      • Sahrmann S.A.
      • Engsberg J.R.
      • Van Dillen L.R.
      Gender differences in pattern of hip and lumbopelvic rotation in people with low back pain.
      looking at lumbopelvic rotation in a static condition, demonstrated that the rotation in the early part of hip lateral rotation is higher in men than in women. The authors postulated that this difference might make men more vulnerable to low back pain associated with hip lateral rotation. Although the current study did not look at a patient population and it reports results from a dynamic upright postural condition, the results could be compared with other previously published studies, and the overall results contribute to further understanding of pelvic motion. This understanding will contribute to designing exercise interventions in patients with conditions such as low back pain. Furthermore, the results highlight the need for further scientific research into new running based exercise programs such as Chirunning or Barefoot running.
      In summary, wherever significant differences were evident in the results, the magnitude of the difference between sexes was generally greater than the difference between overground and treadmill walking, apart from pelvic rotation angles. The magnitudes of all the significant differences were small (1°–4.7°). On one hand, these differences could be viewed as being too small to be clinically significant when measurement error is considered, while on the other, given the limited range of motion that occurs at the pelvis, these changes may indicate a change in the gait pattern.

      Study Limitations

      Although there are no available data to support the thought that an alteration in pelvic movement is directly related to the resonant frequency of the combined system or its individual components (the participant and the treadmill), this is an area of further investigation.
      One of the limitations involved in the study was the manual identification of gait events discussed. However, this would have had little effect on the kinematic pattern or the peak magnitudes. The other limitation could be from the variety of footwear, which has an influence on movement. All participants wore their own gym shoes, which had varying designs and material properties.

      Conclusions

      The present study identified differences in temporal and angular kinematics when comparing overground and treadmill locomotion and between sexes. The use of treadmill for rehabilitation is becoming increasingly popular, because it is a convenient and controlled piece of equipment. However, this study has presented differences the treadmill produces when compared with overground walking. When treadmills are used in assessment and rehabilitation, these differences should be considered.
      • a
        Model T9700HRT; Vision Fitness, 1600 Landmark Dr, Cottage Grove, WI 53527.
      • b
        Vicon, 14 Minns Business Park, West Way, Oxford OX2 0JB, UK.
      • c
        Brower Timing Systems, 12660 S Fort St, Ste 102, Draper, UT 84020.
      • d
        SPSS Inc, 233 S Wacker Dr, 11th Fl, Chicago, IL 60606.

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