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Bill Vicenzino, PhD, MSc, BPhty, Grad Dip Sports Phty, and Thomas McPoil, PhD, PT, ATC, contributed to conception and design; acquisition and analysis and interpretation of the data; and drafting, critical revision, and final approval of the article. Susan Buckland, BPhty (Hons), contributed to analysis and interpretation of the data and drafting and final approval of the article.
Context: Taping and orthoses are frequently applied to control excessive foot pronation to treat or prevent musculoskeletal pain and injury of the lower limb. The mechanism(s) by which these devices bring about their clinical effects are at best speculative and require systematic evaluation.
Objective: To determine the initial effect of the augmented low Dye taping technique (ALD) on plantar foot pressures during walking and jogging.
Design: Within-subjects, repeated-measures randomized control trial.
Setting: Gait research laboratory.
Patients or Other Participants: Fifteen women and 7 men with an average age of 28.0 ± 7.4 years who were asymptomatic.
Intervention(s): Participants walked and jogged along a 12-m walkway before and after the application of ALD. The untaped side served as the control.
Main Outcome Measure(s): Peak and mean maximum plantar pressure data were calculated for the medial and lateral areas of the rear and midfoot and the medial, central, and lateral forefoot areas. Thus, a 3-factor model was tested: condition (ALD, control) × time (preapplication, postapplication) × area (medial and lateral rearfoot and midfoot and medial, central, and lateral forefoot).
Results: Significant 3-way interactions were present for both peak and mean maximum plantar pressure during walking (F 6,126 = 9.55, P = .006 and F 6,126 = 11.36, P = .003, respectively) and jogging (F 6,126 = 5.76, P = .026 and F 6,126 = 4.56, P = .045, respectively) tasks. The ALD predominantly increased plantar pressures in the lateral midfoot during walking and jogging. In addition, tape reduced mean maximum pressure at the medial forefoot and at the medial rearfoot during walking.
Conclusions: The ALD, which has previously been shown to reduce excessive pronation, produced significant increases in lateral midfoot plantar pressures, thereby providing additional information to be considered when the mechanism(s) of action of such a treatment are modeled.
Overuse injuries may occur as a result of repetitive stresses on musculoskeletal tissues. 1 Excessive pronation of the foot, which has been associated with an increased risk of lower limb overuse injury, is often managed as part of a comprehensive treatment program with adhesive antipronation tape, such as the augmented low Dye taping technique (ALD; Figure 1). 2–7
The mechanisms by which antipronation taping exerts its clinical effects remain largely anecdotal and untested at this stage. As a means of exploring the mechanisms by which antipronation tape brings about clinical effects, researchers have studied the tape-induced changes in foot posture 5, 6, 8, 9 and plantar pressures. 10–12 The ALD has consistently been shown to initially increase vertical navicular height or arch height ratio when assessed by static or dynamic measures. 5, 6, 8, 9 Russo and Chipchase 11 and Lange et al 12 recorded plantar pressure patterns on a platform with a sampling rate of 25 to 30 Hz and found that low Dye taping ( Figure 1A) altered pressure in all regions of the foot, specifically and consistently increasing peak and mean pressures in the lateral midfoot, with reductions in the forefoot areas. 11, 12 However, changes in rearfoot pressures were not the same in these 2 studies, with Russo and Chipchase 11 reporting increased pressure and Lange et al 12 finding reduced pressure at the forefoot. Notably, no systematic changes in the medial midfoot plantar pressures were shown. The effect of the ALD on plantar pressures remains unknown.
Our aim was to determine the effect of the ALD on plantar pressures of the foot surface contact area during walking and jogging. We hypothesized on a prima facie basis that after the application of the ALD, the peak and mean maximum plantar pressures would increase in the lateral foot (hypothesis 1) and decrease in the medial foot (hypothesis 2) during walking and jogging.
We used a repeated-measures research design because it reduces individual variability and increases internal validity. The participants served as their own controls.
Fifteen women and 7 men (age = 28.0 ± 7.4 years) qualified for inclusion in the study. We included volunteers if they performed regular physical activity (ie, were not sedentary) and exhibited an increase in vertical navicular height of at least 10 mm when their feet were moved from relaxed stance to neutral subtalar joint position. A Vernier caliper (Mitutoyo, Japan; resolution = 0.02 mm) was used to measure vertical navicular height (as outlined previously by Vicenzino et al 5). A navicular drop of greater than 10 mm is considered abnormal and may contribute to foot injuries. 13 We excluded participants if they reported any symptoms of lower limb injury in the 6 months before the start of the study, had a history of lower limb congenital or traumatic deformity, or previously had an allergic reaction to tape. The relevant institutional review boards approved the study, and all participants provided informed consent.
The EMED-SF capacitance transducer matrix platform (Novel Electronics Inc, Minneapolis, MN) was used to measure plantar pressures between the foot and the supporting surface. The platform consists of a matrix of 1944 force transducers that are uniformly distributed in an area of 23 × 44 cm. The transducers have a density of 2 sensors per cm 2 with a sampling frequency of 70 Hz. The sensors have an input pressure saturation of 1200 kPa, which was not reached by any of the subjects in the current study. The platform was positioned level with the floor at the midpoint of a 12-m walkway. The EMED-SF system has demonstrated overall reliability when 3 to 5 walking trials are used. 14
The 2 treatment conditions for this study were ALD and a no-tape control. A 38-mm–wide rigid sports tape with a zinc oxide adhesive (Leuko Premium Sportstape, Beiersdorf Pty Ltd, Sydney, Australia) was applied to all participants by the same experienced sports physiotherapist. The ALD method 5, 7, 9 involves applying a standard low Dye tape, calcaneal slings, and reverse 6s ( Figure 1A, B, and C, respectively).
Participants attended an initial session during which their suitability for the study was determined. A second session was conducted to obtain the plantar pressure measurements. Tape was applied randomly to either foot, with the untaped foot serving as a within-subjects control. The leg to be taped was cleaned with warm soapy water, and any hair in the area was removed to maximize adhesion of the tape.
In each of the tasks, the participant was instructed to ambulate at a self-selected pace over the walkway (12 m). Multiple trials of walking or jogging were permitted to allow the subjects to practice not looking at the ground to prevent targeting of the platform surface. Data were collected over 5 trials for each foot. Tape was then applied to the selected foot, and the previously described procedure was repeated. Both walking and jogging speeds were monitored to ensure consistency for all trials within each participant, especially from pretape to posttape trials. At the completion of data collection, the tape was removed with the aid of blunt-nosed scissors and the foot examined for adverse skin reactions.
The data collected were divided into 10 areas or masks using the NovelWin Automask software system (Novel USA, Inc, Minneapolis, MN). The 3 masks involving the toes (hallux, second toe, and toes 3 to 5) were omitted from analysis because of their high variability. 15 The remaining 7 regions evaluated in the study were the medial rearfoot, lateral rearfoot, medial midfoot, lateral midfoot, medial forefoot (first metatarsal), central forefoot (second metatarsal), and lateral forefoot.
Data collected were averaged across trials for each mask. Two dependent variables were investigated in this study: peak pressure and mean maximum pressure. The independent variables of interest were condition (ALD, control), time (preapplication, postapplication), and area (medial and lateral rearfoot and midfoot and medial, central, and lateral forefoot) for both walking and jogging tasks. A multivariate, repeated-measures analysis of variance (condition × time × area) was conducted using SPSS 11.0 for Windows (SPSS Inc, Chicago, IL) for both walking and jogging (α = .05). Significant interaction effects were then investigated further with tests of simple effects in the form of paired-samples t tests. We also calculated the standardized mean difference or the effect size, that is, the mean difference divided by the pooled SD.
The consistency of the stance-phase durations is an important issue because previous authors 16 have shown that force and pressure values can increase with changes in velocity. Intraclass correlation coefficients (2,1) were calculated to ensure consistency of gait velocity between repeated trials of walking and running, as represented by stance-phase duration. 17
The mean stance-phase durations were 0.623 seconds and 0.308 seconds for walking and jogging, respectively. The intraclass correlation coefficients for stance-phase duration for walking and jogging were .96 and .97, respectively, which would be “almost perfect” according to the Landis and Koch criteria. 18 Based on these findings, we concluded that the stance-phase and support-phase durations and, consequently, gait velocity were consistent among trials and that further analyses of the plantar pressure data could be conducted.
Means and SDs for mean maximum pressure and peak pressure during walking and jogging are presented in Tables 1 through 4, as are the pairwise mean differences and 95% confidence intervals. Figure 2 shows the results in pictorial format.
Statistically, a significant condition × time × area interaction effect was noted for mean maximum pressure for the walking (F 6,126 = 11.36, P = .003) and the jogging (F 6,126 = 4.56, P = .045) tasks. Tests of simple effects showed a significant increase in mean maximum pressure at the lateral midfoot during the walking task between the untaped control and the taped foot after application of the ALD ( P < .001) and a decrease in the medial forefoot ( P = .008). The effect size for the increase in pressure in the lateral midfoot (1.7) was larger than for the reduction in medial forefoot pressure (1.2). The only significant change in mean maximum pressure for the jogging task between the untaped control and the taped foot occurred in the lateral midfoot ( P < .001), with an increase after application of the ALD. The effect size for this increase was 2.0.
A significant condition × time × area interaction effect was also identified for peak pressure during walking (F 6,126 = 9.55, P = .006) and jogging (F 6,126 = 5.76, P = .026). Significant changes in peak pressure between the untaped control and the taped foot during the walking task were identified as an increase in the lateral midfoot ( P < .001) and a decrease in the medial rearfoot ( P = .009) after tape application ( Figure 2). The effect size for the increase in pressure in the lateral midfoot (1.4) was larger than for the reduction in medial forefoot pressure (1.0). In the jogging task, an increase in the lateral midfoot pressure ( P < .001) after application of tape was significant. The effect size for this increase was 2.0.
No adverse effects (eg, skin irritation, pain, injury) occurred and no subjects dropped out during the experiment.
Our first hypothesis stated that peak and mean plantar pressures would increase in the lateral aspect of the foot during walking and jogging after the application of the ALD. This hypothesis was supported in part by the increase in peak and mean pressures in the lateral midfoot during walking and jogging. A second hypothesis proposed that the ALD would reduce peak and mean plantar pressures in the medial aspect of the foot during walking and jogging. Based on the results of the walking data only, which revealed a decrease in mean maximum pressure at the medial forefoot and the medial rearfoot, limited evidence supports this suggestion. Although we did not address this in our hypotheses, it is worth noting that the increase in lateral midfoot pressure (effect sizes from 1.4 to 2) was substantially larger than the reduction in medial-side pressures (effect sizes from 1 to 1.2). Furthermore, the large effects in increased lateral midfoot pressures across 2 speeds of gait (walking, jogging) indicate that it is a very robust finding. As well as a smaller effect size, the reduction in medial-side pressures was only present in walking, not jogging.
The ALD increased plantar pressures under the lateral midfoot (our study) and increased the height of the medial longitudinal arch of the foot (other authors 5, 6, 9); the latter was inferred to be an antipronation effect. It is tempting to speculate that the altered plantar pressure pattern we observed is because of an antipronation effect of the ALD. However, such a relationship between plantar pressures and foot motion has not been established. 19 Work is now required to evaluate the relationship between ALD-induced changes in plantar pressures and joint motion so as to further our understanding of the physiologic mechanisms underpinning such taping techniques.
We could only find 2 other studies of the effects of antipronation taping (low Dye only) on plantar pressures, and those groups 11, 12 only evaluated walking, as opposed to both walking and jogging in our study. Russo and Chipchase 11 assessed the effect of the standard low Dye taping on peak plantar pressures of normal feet and found an increase in the medial and lateral rearfoot areas and lateral midfoot, with a reduction in both the medial and lateral forefoot areas as well as the medial midfoot. Lange et al 12 studied taping-induced changes in mean and peak plantar pressures before and after the application of the standard low Dye taping in subjects with pronated feet. They found an increase in mean and peak plantar pressure in the lateral midfoot. A decrease in mean pressure was found in the medial and lateral rearfoot and the medial, central, and lateral forefoot areas. Peak pressure was reduced in the medial and lateral rearfoot, medial forefoot, and central forefoot.
Comparing our data for the ALD during walking to the low Dye taping data in the previous studies 11, 12 may provide some insight into the underlying mechanisms of action of these techniques. Most notably, all studies have shown the lateral midfoot area to experience increased plantar pressures, regardless of the pressure index used. The strength of such an effect compels us to address this finding in any model that seeks to describe the underlying physiologic mechanism(s) of antipronation taping.
Additionally, comparisons of the data from our study and the previous studies 11, 12 may reflect the effect of adding reverse 6s and calcaneal slings to the low Dye technique in the ALD. Compared with the current study, changes in plantar pressures were more widely distributed in the other studies of the low Dye technique, 11, 12 indicating that the inclusion of reverse 6s and calcaneal slings in the ALD appears to counter those changes in plantar pressures at the forefoot and rearfoot. The ALD has previously been shown more effective than the low Dye technique in maintaining medial longitudinal arch height during 20 minutes of exercise. 5, 6 Perhaps this finding is associated with the observed differences in plantar pressures exerted by the ALD compared with the low Dye technique.
We also found, in walking only, changes in the untaped foot that were essentially increases in the mean and peak pressures in the midfoot and rearfoot. The relevance of these findings is not readily apparent, except to possibly indicate that the taping of 1 foot leads to body-wide alterations in motor function (eg, sensory-motor, balance, neuromotor control). Further study is required to better understand the underlying mechanisms by which this occurred.
We and Lange et al, 12 but not Russo and Chipchase, 11 selected subjects who exhibited increased pronation. An interesting response to antipronation taping in mean maximum plantar pressures was observed at the medial rearfoot that is not seen in any other area. That is, both our results and those of Lange et al 12 showed reduced mean maximum plantar pressures in the medial rearfoot area, whereas Russo and Chipchase 11 reported the opposite trend in their subjects who were not excessive pronators. Thus, it would seem that in the medial rearfoot, the antipronation taping techniques are selectively reducing pressure in pronators (defined by a change in vertical navicular height of more than 1 cm). This finding may provide grounds on which to further study the pressure changes reported herein in relation to overuse musculoskeletal injuries that are associated with excessive pronation.
An alternate explanation for differences between taping techniques (ie, ALD versus low Dye) in plantar pressure between the current study and the previous 2 studies 11, 12 may well revolve around the use of systems with different sampling frequencies. We used an EMED-SF system with a 70-Hz sampling rate, whereas the others used the EMED-AT-2 system, with a sampling frequency of 25 to 30 Hz. Sampling at a frequency of less than 45 Hz may result in less-than-optimal representation of the plantar pressure data during walking gait and potentially invalidate inferences that may be drawn from it. 20
The reader should be cognizant of the fact that we only investigated the initial effects of antipronation taping on plantar pressures in asymptomatic but pronated feet. Future research is required to assess the effect of taping on plantar pressures after exercise (eg, after 10 and 20 minutes of jogging as in previous studies 5, 6, 9) and in symptomatic populations.
In summary, plantar pressures of the foot were significantly altered after the application of the ALD, largely shown as increases in peak and mean maximum pressure in the lateral midfoot for both the walking and jogging tasks and reductions in mean maximum pressure in the medial forefoot and peak pressure in the medial rearfoot during walking.
We acknowledge the support of the following as contributions leading to the submission of this manuscript: the participants who gave freely of their time to participate in the study, the University of Queensland Staff Travel Grant for Dr Vicenzino, and the Fulbright Senior Fellowship for Dr McPoil.