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IJSM/1951/28.3.2011/Macmillan

Orthopedics & Biomechanics

Changes in Footprint with Resistance Exercise

Authors

E. Jimenez-Ormeño1, X. Aguado2, L. Delgado-Abellan3, L. Mecerreyes4, L. M. Alegre5

Affiliations

Affiliation addresses are listed at the end of the article

Key words ▶ foot ● ▶ arch index ● ▶ weightbearing ● ▶ footwear ●

Abstract ▼ We aimed to describe the changes in footprint characteristics after 2 types of resistance training sessions performed at different intensities. 18 young subjects (8 men and 10 women) volunteered for the study. All of them performed 2 different resistance training sessions, one with light loads (LS) and the other with heavy loads (HS). Their footprint was recorded and analysed before and after exercise. Lengths, widths, and areas of the footprint (rearfoot, midfoot, and forefoot) were measured. Almost all the variables significantly increased after both sessions. The great-

Introduction ▼

accepted after revision March 01, 2011 Bibliography DOI http://dx.doi.org/ 10.1055/s-0031-1275354 Int J Sports Med 2011; 32: 1–6 © Georg Thieme Verlag KG Stuttgart · New York ISSN 0172-4622 Correspondence Dr. Luis M. Alegre, PhD University of Castilla-La Mancha Faculty of Sports Sciences Campus Tecnológico Avda. Carlos III s/n 45071 Toledo Spain Tel.: + 34/925/268 800 Ext: 5520 Fax: + 34/925/268 846 [email protected]

Footwear is designed to protect the foot and facilitate its functions in daily activities [37]. To accomplish its role, footwear has to be adjusted to the foot in terms of lengths, widths, heights and circumferences [41]. However, the foot is a dynamic structure that changes its shape depending on the imposed load and physical activity performed [28, 29, 35]. Podiatrists, physiotherapists and shoe designers need to understand these changes to adapt the footwear to the user and the type of activity performed. This is especially important in situations of high mechanical loading of the foot, such as during sport and physical activity, for example, when carrying weights. A correct footwear fitting has been associated with improved movement association between the foot and the shoe. This increased the movement efficiency and comfort in military personnel, with even decreases in their injury rate [31]. Besides, badly fitting shoes can lead to excessive foot pressures, and to impaired stability [3]. For example, workers with high foot pressures were at approximately 3 times the risk of presenting with ankle/foot disorders [39].

est changes were found in the midfoot (area, LS: 10.4 %; HS: 8.1 %, P < 0.0005; width, LS: 7.5 %, P = 0.002, and HS: 8 %, P < 0.0005). However, there were no significant differences between postexercise data from both sessions. The variable that showed the smallest changes was the foot length (LS: 0.3 %, P = 0.023; HS: − 0.4 %, P = 0.549). A resistance training session led to increases in most of the dimensions of the footprint, regardless of the magnitude of the loads handled. The greatest changes were found in the midfoot, indicating that the foot was flatter after exercise, and the foot changed more in width than in length.

Apart from one exception found in earlier investigations [5], most studies that deal with changes in foot morphology during weightbearing described significant changes in their measurements, such as foot contact area, foot length, foot and heel widths, height and angle of the arch [4, 17, 37]. In addition, most of the studies that have evaluated how the foot changes after exercise report that physical activity leads to an increase in foot volume [8, 24, 29]. McWhorter and colleagues [28] checked that high loading conditions led to greater increases in the foot volume compared to low loading conditions; on the other hand, static conditions produced a greater increase in foot volume that dynamic ones. Several studies have reported gender differences regarding the most important anatomical measures of the foot [14, 22, 23, 27, 42]; they stated that men’s feet are longer and wider in relation to their height than women’s. In addition, others [20, 43] have shown that women’s feet changed more with weightbearing because they are more flexible. Poor fitting footwear has been mentioned as the possible origin of the higher incidence of foot injuries in military women [33]. Therefore, men’s and women’s feet could differently respond to exercise.

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2 Orthopedics & Biomechanics

IJSM/1951/28.3.2011/Macmillan

The above-cited studies [5, 9, 37] on the dimensional changes of the foot in response to weightbearing provide limited information because most of them measured changes in the volume, foot length and width, whereas other dimensions were not described in detail such as the 3 contact areas of the foot (forefoot, midfoot and rearfoot) [43]. Furthermore, as far as we know, no studies have been performed to evaluate the transitory changes produced in the feet as a result of added weight. Therefore, the objective of this study was to describe the changes in the footprint after 2 types of resistance training sessions. An additional objective was to test whether there were differences between men and women responses. Our hypotheses were that exercise with loads would cause different changes, depending on the intensity, and that these changes would be different in men and women.

Methods ▼ Subjects

Procedure Overview Each participant performed 2 different resistance training sessions in a fitness room in the morning and at the same time, with a week between the 2 sessions, using the same footwear: a training session with light loads, adjusted to the subject’s body weight (maximum to 0.35 times the body weight in men and 0.25 in women) and a training session with heavy loads adjusted to the subject’s body weight (maximum 0.50 times the body weight in men and 0.40 in women). The footwear worn by the subjects were sports shoes that they usually wore during their sports activities, which can be classified as “cross training” [19]. After the footprint record of the dominant foot pre-exercise, the session began with a 5 min warm-up cycling at 60–70 W and it ended with the post-exercise footprint recorded from the same ▶ Fig. 3). This second record of the footprint was made foot (● within the first minute after finishing the last exercise. The test▶ Fig. 1. ing sessions followed the structure described in ●

Pre-exercise and post-exercise measures

Instrumentation

a

b

c

Ff W

Ff A FL

All subjects were weighed on a standing scale SECA (SECA Ltd., Germany) and their standing height was measured with a stadiometer (SECA Ltd., Germany). The measurements obtained from the footprint were taken according to the protocol described in ▶ Fig. 2a) was registered durMeana et al. [30]. The footprint (● ing bipedal stance by applying photograph developer on the foot sole with a paintbrush. Subsequently, the subjects had to place their foot on photo paper placed on the ground, and finally, the paper was immersed in a fixer solution.

Before pre-exercise measurements, the participants had to take their shoes off and lay down on a mat for 10 min, time enough for the foot dimensions to return to basal values [29]. The pre and post-exercise measures were only taken from the dominant foot. The variables studied were: ▶ Contact area of the forefoot, midfoot and rearfoot, excluding ▶ Fig. 2b). Each area was measured by dividing the toes (● length of the foot (excluding toes) into equal thirds [7]. ▶ Total contact area (TA): Sum of the forefoot, midfoot and rear▶ Fig. 2b). foot areas, excluding toes (● ▶ Arch index (AI). ▶ Foot length with toes (FL): Distance between a posterior tangent to the heel and an anterior tangent to the tip of longest ▶ Fig. 2c). toe (● ▶ Foot length without toes (FLWt): Distance between a posterior tangent to the heel and an anterior tangent to the tip of ▶ Fig. 2c). longest metatarsal [34] (● ▶ Foot widths: Maximum width of the forefoot (FfW), midfoot ▶ Fig. 2c). (MfW) and rearfoot (RfW), (● The footprint records were analysed with a custom-made software (AreaCalc v2.6) [12], which applied the protocol of Cavanagh and Rodgers [7] to analyze the footprints.

Mf A

Table 1 Sample characteristics.

women (n = 10) men (n = 8)

Age (Years)

Mass (kg)

Height (m)

BMI (kg · m − 2)

20.7 (0.5)

61.2 (8.8)

1.67 (0.08)

21.8 (3.0)

20.5 (0.9)

68.4 (4.2)

1.76 (0.04)

22.2 (1.1)

10 min rest

Footprint record PRE-exercise

Training session, 30 min

Mf W

Rf W

Rf A

Fig. 1 Weight Height

FL Wt

18 young active subjects volunteered for the study (10 women and 8 men), all of them students of sports sciences, with age ranging between 19 and 22 years. Their physical characteris▶ Table 1. 5 of the subjects had cavus feet tics are described in ● (arch index ≤ 0.21), 10 normal feet (arch index = 0.21–0.26) and 3 flat feet (arch index ≥ 0.26) [7]. The arch index (AI) is the ratio of the midfoot area to the area of the entire foot excluding the toes [7]. All the volunteers signed written informed consent to confirm their participation in the study. The participants who had any of the following conditions were excluded: recent lower limb injuries, any impingement in their feet that could be aggravated by exercise, skin infections, or any other physical reason given by a physician. The study was approved by the local Institutional Review Board, and carried out in accordance with the ethical standards of the International Journal of Sports Medicine [16].

Fig. 2 Footprint record (a) with the variables utilized in the study. Abbreviations: FfA, Forefoot area; MfA, Midfoot area; RfA, Rearfoot area; FL, Foot length with toes; FLWt, Foot length without toes; TA, Total area; FfW, Forefoot width; MfW, Midfoot width; RfW, Rearfoot width.

Testing protocol.

Footprint record POST-exercise

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IJSM/1951/28.3.2011/Macmillan

Orthopedics & Biomechanics

Fig. 3 Percent changes between pre- and post-exercise measures in the light and heavy sessions. Abbreviations: FfA, Forefoot area; MfA, Midfoot area; RfA, Rearfoot area; FL, Foot length with toes; FL Wt, Foot length without toes; TA, Total area; FfW, Forefoot width; MfW, Midfoot width; RfW, Rearfoot width; * , light pre vs. post, P < 0.05; †, light pre vs. post, P < 0.01; ‡, light pre vs. post, P < 0.001; §, heavy pre vs. post, P < 0.05; 储, heavy pre vs. post, P < 0.01; ¶, heavy pre vs. post, P < 0.001.

25 ¶

20

Change (%)

¶

15 10

10.4 ¶

5

FfA

MfA

RfA

7.5 8

§ 4

2.7 3.2

2.4

*

¶ 5.6

3.3

0

¶ 8.1

* –0.4 0.3

0.5 0.4

FL

FLWt

AI

4.5

3.9

1.4

0.6 0.7

TA

FfW

2.7

MfW

RfW

–5 Light

Heavy

Exercises

Loads (times body weight) Light day

standing row dumbbell squats dumbbell shoulder press half squat barbell curls dumbbell heel raise elbow extension

Heavy day

Men

Women

Men

Women

0.27 (0.25) 0.17 0.17 (0.15) 0.35 0.17 (0.15) 0.20 0.09 (0.10)

0.20 (0.20) 0.10 0.10 (0.10) 0.25 0.10 (0.10) 0.14 0.05 (0.05)

0.38 (0.45) 0.25 0.30 (0.31) 0.50 0.30 (0.30) 0.30 0.12 (0.21)

0.30 (0.35) 0.14 0.20 (0.22) 0.40 0.20 (0.23) 0.23 0.09 (0.12)

Sessions The sessions were performed as circuit training. The exercises were performed following the guidelines of Delavier [10]. The subjects performed a typical circuit training session because it is a type of workout widely utilized [13], and allowed the untrained volunteers to complete the whole session safely using the proper technique. These exercises were chosen because they are also widely utilized in resistance training and involve different muscle groups and in all of them the load direction was vertical. The participants performed the circuit 3 times, 12 repetitions of each exercise, with a 30 s rest between each one, and a 2 min rest between each circuit. The total training time was about 30 min in both sessions. Taking these data as reference, the loads and ▶ Table 2. Training exercises of each session are described in ● loads were taken from the study of Vrijens [38], where the intensity of a resistance exercise can be determined as the product of a subject’s body weight and a coefficient. We slightly modified these loads with the data of a pilot study with 8 subjects from the same population of this study. They were adjusted in a way that the participants were able to complete the number of repetitions proposed by Vrijens in each exercise. In the exercises which were not included in Vrijens’ study, we applied the same criteria of loads and repetitions, that is, loading of 12 repetitions that produced local muscular fatigue in the heavy session and 60–70 % of the load from the heavy session to the light one. Loading schemes similar to those of Vrijens (number of sets and repetitions) have been already proposed for resistance training for the untrained population [11, 32]. For example, the study of Harber and colleagues [15] utilized loads of 40–60 % of one repetition maximum in shoulder press, biceps curls and elbow extensions that were quite close to the ones utilized in the Heavy session of the present study when they were expressed as a percentage of their subjects’ body weight. Loads of the Light session

Table 2 Loads and exercises performed by men and women in the light and heavy sessions. The loads proposed by Vrijens (2006) are shown in parentheses.

were chosen in order to test the effect of lower loading on the footprint record.

Statistical analysis The data were analysed with the SPSS Software for Windows v17 (SPSS Inc. USA), with a level of significance of P < 0.05. From the Shapiro-Wilks test, we found all the variables normally distributed. Paired t-tests were utilized to look for differences between pre- and post-exercise measurements. As control situation, the comparison between the light and heavy pre-exercise sessions was used. These situations were compared using paired t-tests. The intraclass correlation coefficients (ICC) and coefficient of variation (CV) of each variable were computed from them. We found the Pearson’s correlation coefficients between the total loads handled in each session and the percentage changes of each variable from pre- to post-exercise measurements in both sessions, between the anthropometric measures (weight, height and BMI) and percentage changes, and between the arch index and the percentage changes. A three-way ANOVA was utilized (sex × time of measurement × session) to analyse sex differences in the response of the footprint to exercise. When a major effect or interaction was found, a post hoc analysis was made using the Scheffe test.

Results ▼ The ICCs found when comparing pre-exercise measures of the light and heavy sessions (control situation) are presented ▶ Table 3. All of them were above 0.95, except for the rearfoot in ● width, where the ICC was 0.901. The CVs ranged from 0.3 to 4.6 %. In addition, with the numbers available, t-tests showed no significant differences in the comparison of any of the measures.

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IJSM/1951/28.3.2011/Macmillan

When comparing the measurements before and after exercise, significant differences were found in both situations and in all the measures, except in the forefoot width of the light session ▶ Table 4 and foot length with toes of the heavy session (● ▶ Fig. 3). When comparing post-exercise values between and ● the light and heavy session t-tests showed no significant differences. The percentage changes were similar in both situations in ▶ Fig. 3). Midfoot area was the all dimensions of the footprint (● parameter with the greatest increases in both training sessions (10.4 % and 8.1 %, P < 0.0005, light and heavy, respectively). In addition, there were significant increases in all the areas and widths measured, except in the forefoot width in the light session (0.6 %, P = 0.083) and the foot length with toes in the heavy session ( − 0.4 %, P = 0.549). No significant correlations were found between percent changes in the measures and total load handled by the participants in each session. There were significant correlations between standing height and percent changes of the midfoot width in the light session and foot length with toes in heavy session (r = 0.48, P = 0.045 and r = 0.61, P = 0.007, respectively), between body weight and foot length with toes in the heavy session (r = 0.57, P = 0.013) and between BMI and foot length with toes in the light session (r = 0.49, P = 0.040). Also, significant correlations were found between foot type, classified by the AI, and percent changes in the midfoot area (r = − 0.50, P = 0.036) and between AI value and its own changes (r = − 0.62, P = 0.006), indicating that subjects with a flatter foot tended to change relatively less at their midfoot. In the comparison between men and women, significant differences were found in all foot dimensions except in the AI, midfoot width and rearfoot width, both before and after each training Table 3 Interday measurement reliability. Variables

ICC

Coefficient of variation ( %)

forefoot area midfoot area rearfoot area arch index foot length with toes foot length without toes total area forefoot width midfoot width rearfoot width

0.994 0.985 0.984 0.978 0.959 0.998 0.990 0.991 0.971 0.901

1.1 3.9 1.4 2.9 0.9 0.3 1.4 0.5 4.6 2.0

ICC, intraclass correlation coefficient

Variables

Discussion ▼ The results of the present study demonstrate that most of the dimensions of the footprint changed after performing a resistance training session. The midfoot area was the variable most prone to change after a period of weightbearing, making the foot flatter, which is very probably associated with the natural tendency of the foot to become deformed and increase the contact area in this part. There were no significant differences between post-exercise data from both sessions, showing that the foot print changed similarly regardless of imposed load. This was confirmed by the absence of significant correlations between the percentage changes in each measure and the absolute load handled by the participants during the 2 sessions. Nonetheless, the correlations found between AI, and the percent changes in this measure and midfoot area (r = − 0.62, P = 0.006; r = − 0.50, P = 0.036) indicate that subjects with a more cavus foot (lower arch index) tended to change more at the support area of the midfoot. Physical activity like running or walking produces increases in the foot volume [6, 18, 22, 23]. The parameters measured in the present study also suggest this, although we cannot draw direct comparisons because we only measured contact areas instead of the whole foot volume. The changes found in the variables of the footprint could be produced because of changes in the foot temperature, which also lead to modifications in the mechanical behaviour of the different tissues of the foot [7]. Some authors have also attributed the changes in foot size to exercise resulting in the increase blood flow in the muscle [2, 18, 26, 29] and an increase in transcapillary filtration of intravascular fluid [18, 36]. However, the activity performed did not include impacts such as those that occur during running, which may exceed 3 times the body weight [6]; although it is speculative we think that in our subjects the changes in the mechanical behaviour of muscles and tendons were more important than the modifications in the vascular status of the foot [25]. It is possible that the relative importance of these mechanisms changes in dynamic situations such as running [8, 29].

Pre-exercise Light

forefoot area (mm2) midfoot area (mm2) rearfoot area (mm2) arch index foot length with toes (cm) foot length without toes (cm) total area (mm2) forefoot width (cm) midfoot width (cm) rearfoot width (cm)

▶ Table 5). However, when comparing persession with loads (● cent changes in men and women, no significant differences were found in any of the variables analysed, with the numbers available. Besides, there were no interactions in the three-way ANOVA; that is, men and women showed similar changes in their footprint between the pre- and post-exercise situations in both training sessions.

4 139 (568) 2 028 (514) 2 780 (291) 0.22 (0.04) 23.6 (1.5) 20.1 (1.2) 8 946 (1 104) 8.3 (0.5) 3.2 (0.7) 5.1 (0.3)

Post-exercise Heavy

4 178 (590) 2 037 (546) 2 765 (260) 0.22 (0.04) 23.7 (1.2) 20.1 (1.2) 8 980 (1 126) 8.4 (0.5) 3.1 (0.7) 5.1 (0.3)

Light 4 276 (592)‡ 2 223 (536)‡ 2 857 (317)‡ 0.24 (0.04)† 23.7 (1.5)* 20.2 (1.2)† 9 356 (1 214)‡ 8.4 (0.5) 3.4 (0.6)† 5.2 (0.3)*

Heavy 4 279 (621)¶ 2 205 (628)¶ 2 854 (283)¶ 0.23 (0.04)¶ 23.7 (1.5) 20.2 (1.2)储 9 338 (1 249)¶ 8.4 (0.5)§ 3.4 (0.7)¶ 5.2 (0.3)储

Table 4 Measured variables for the light and heavy sessions. No significant differences were found in any of the variables studied when comparing light vs. heavy sessions, neither before nor after exercise.

* , Light pre vs. post, P < 0.05; †, Light pre vs. post, P < 0.01; ‡, Light pre vs. post, P < 0.001; §, Heavy pre vs. post, P < 0.05; 储, Heavy pre vs. post, P < 0.01; ¶, Heavy pre vs. post, P < 0.001

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IJSM/1951/28.3.2011/Macmillan

Variables

Men (n = 8) 2

forefoot area (mm ) midfoot area (mm2) rearfoot area (mm2) arch index foot length with toes (cm) foot length without toes (cm) total area (mm2) forefoot width (cm) midfoot width (cm) rearfoot width (cm)

4 638 (401) 2 386 (436) 2 962 (245) 0.24 (0.04) 24.9 (0.75) 21.1 (0.6) 9 986 (561) 8.7 (0.4) 3.6 (0.6) 5.1 (0.4)

Orthopedics & Biomechanics

Women (n = 10)

% difference

P-value

3 739 (292) 1 741 (381) 2 634 (246) 0.21 (0.04) 22.6 (1.1) 19.3 (0.9) 8 114 (570) 8.1 (0.3) 2.9 (0.6) 5.1 (0.3)

19.4 27.0 11.1 12.5 9.4 8.4 18.7 7.0 17.2 − 0.6

< 0.0005 < 0.0005 0.012 0.177 < 0.0005 < 0.0005 < 0.0005 0.002 0.051 0.854

When comparing data between men and women, there were significant differences in all the variables except for the AI, midfoot width and rearfoot width, before and after each training ▶ Table 5). However, there were no differences in the session (● percent changes of either of the 2 sessions or in the interactions in the factorial ANOVA, confirming that men and women showed similar changes in their foot morphology regardless of the load utilized. As far as we know, only McWhorter [29] has examined changes between men and women after physical exercise. They found that women’s feet were more sensitive to changes produced by low intensity exercise (12 min of walking), but both men and women underwent significant changes after 12 min of running. Accordingly, it seems that our activity exceeded the threshold of intensity at which men and women show the same changes. The results of the present investigation help to understand how and how much the foot changes after supporting loads greater than body weight. These results can be applied in the design and adaptation of footwear for sport and work environments in which supporting and carrying weight is an issue. The footwear designed for these purposes must adapt more in the transverse axis than in the longitudinal one, and this should be applied to men’s and women’s footwear. The shoes for individuals with cavus feet should be adapted specifically in the midfoot area. The fitting around the width dimensions has already been described as an issue during shoe design and development [40], because most shoe sizing systems are based on the longitudinal measures. In fact, the use of flexible materials and inserts has been proposed as a method to improve the perception of fit [40] and enhance the foot-shoe interaction [31]. A good fit will not only enhance shoe comfort but also has clinical implications, like decreases in the problems related to overuse and fatigue [1, 21, 31]. Furthermore, this knowledge of the parts that change in the area of support of the foot provides tools for podiatrists and physical therapists to design orthotics that can be adapted to the changes produced by exercise. As a limitation of our study, we can point out that the measures discussed here have not been taken directly from the foot, but from the registration of the footprint, thus the methodology utilized could not record changes in volume or size of the foot occurring outside the surface support, such as heights.

Conclusion ▼ To sum up, a training session with loads led to changes in most of the dimensions of the footprint, regardless of the magnitude of the loads handled. The greater changes were found in the midfoot, with significant increases in width and area, indicating

Table 5 Measured variables for the men and women in the light session before exercise. The rest of the measurements have been omitted because the differences were similar between sessions and before and after exercise.

that the foot was going to be flatter after exercise, and the foot changed more in width than in length. The knowledge gained about the transitory changes produced by weightbearing can help shoe designers to reduce the fitting problems during footwear development and manufacturing and therefore enhance shoe function and comfort.

Acknowledgements ▼ The present study has obtained financial support from the FEDER funds and the Counselling of Education, Science and Culture of the Junta de Comunidades de Castilla-La Mancha, Spain. Affiliations 1 Universidad de Castilla-La Mancha, Grupo de Biomecánica Humana y Deportiva, Toledo, South Georgia and the South Sandwich Islands 2 University of Castilla-La Mancha, Facultad de Ciencias del Deporte, Toledo, Spain 3 Universidad de Castilla-La Mancha, Grupo de Biomecánica Humana y Deportiva, Toledo, Spain 4 Asociación de Investigación y Desarrollo del Calzado y Afines de Toledo, ASIDCAT Laboratory, Toledo, Spain 5 University of Castilla-La Mancha, Faculty of Sports Sciences, Toledo, Spain

References 1 Asplund CA, Brown DL. The running shoe prescription: fit for performance. Phys Sportsmed 2005; 33: 17–24 2 Baker CH, Davis DL. Isolated skeletal muscle blood flow and volume changes during contractile activity. Blood Vessels 1974; 11: 32–44 3 Burns SL, Leese GP, McMurdo ME. Older people and ill fitting shoes. Postgrad Med J 2002; 78: 344–346 4 Cappaert JM, Rich B, Roberts S. Variation in foot shape under various loading conditions. In: Proceedings 8th Footwear Biomechanics Symposium. Taipei (Taiwan), 2007 5 Carlsoo S, Wetzenstein H. Change of form of the foot and the foot skeleton upon momentary weight-bearing. Acta Orthop Scand 1968; 39: 413–423 6 Cavanagh PR. Biomechanics of distance running. Champaign, IL: Human Kinetics Books; 1990 7 Cavanagh PR, Rodgers MM. The arch index: a useful measure from footprints. J Biomech 1987; 20: 547–551 8 Cloughley WB, Mawdsley RH. Effect of running on volume of the foot and ankle. J Orthop Sports Phys Ther 1995; 22: 151–154 9 Cheng JC, Leung SS, Leung AK, Guo X, Sher A, Mak AF. Change of foot size with weightbearing. A study of 2829 children 3 to 18 years of age. Clin Orthop Relat Res 1997; 342: 123–131 10 Delavier F. Strength training anatomy. 2nd ed. Champaign, IL: Human Kinetics; 2006; 144 11 Dixon CB, Robertson RJ, Goss FL, Timmer JM, Nagle EF, Evans RW. The effect of acute resistance exercise on serum malondialdehyde in resistance-trained and untrained collegiate men. J Strength Cond Res 2006; 20: 693–698 12 Elvira JL, Vera-Garcia FJ, Meana M. Subtalar joint kinematic correlations with footprint arch index in race walkers. J Sports Med Phys Fitness 2008; 48: 225–234 13 Fleck SJ, Kraemer WJ. Designing resistance training programs. 3rd ed. Champaign, IL: Human Kinetics; 2004; 377

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5

6 Orthopedics & Biomechanics 14 Frey C. Foot health and shoewear for women. Clin Orthop Relat Res 2000; 372: 32–44 15 Harber MP, Fry AC, Rubin MR, Smith JC, Weiss LW. Skeletal muscle and hormonal adaptations to circuit weight training in untrained men. Scand J Med Sci Sports 2004; 14: 176–185 16 Harriss DJ, Atkinson G. International Journal of Sports Medicine – Ethical Standards in Sport and Exercise Science Research. Int J Sports Med 2009; 30: 701–702 17 Houston VL, Luo G, Mason CP, Mussman M, Garbarini M, Beattie AC. Changes in male foot shape and size with weightbearing. J Am Podiatr Med Assoc 2006; 96: 330–343 18 Jacobsson S, Kjellmer I. Accumulation of fluid in exercising skeletal muscle. Acta Physiol Scand 1964; 60: 286–292 19 Johnson TE. Running and court shoes. In: Kreighbaum EF, Smith MA (eds) Sports and Fitness Equipment Design. Champaign, Illinois: Human Kinetics; 1995; 15–30 20 Kadambande S, Khurana A, Debnath U, Bansal M, Hariharan K. Comparative anthropometric analysis of shod and unshod feet. The Foot 2006; 16: 188–191 21 Klein NL. When a good work shoe isn’t enough. Occup Health Saf 2003; 72: 78–80 22 Krauss I, Grau S, Janssen P, Maiwald C, Mauch M, Horstmann T. Gender differences in foot shape. In: 7th Symposium on Footwear Biomechanics Cleveland, OH (USA); 2005 23 Krauss I, Valiant G, Horstmann T, Grau S. Female foot morphology – implications for last design. In: Proceedings 8th Footwear Biomechanics Symposium. Taipei, (Taiwan) 2007 24 Kunde S, Sterzing T, Milani TL. The influence of body position and physical activity on foot dimensions measured by a foot scanning system. In: Proceedings 8th Footwear Biomechanics Symposium. Taipei (Taiwan), 2007 25 Lazzarini KM, Troiano RN, Smith RC. Can running cause the appearance of marrow edema on MR images of the foot and ankle? Radiology 1997; 202: 540–542 26 Lundvall J, Mellander S, Westling H, White T. Fluid transfer between blood and tissues during exercise. Acta Physiol Scand 1972; 85: 258–269 27 Manna I, Pradhan D, Ghosh S, Kar SK, Dhara P. A comparative study of foot dimension between adult male and female and evaluation of foot hazards due to using of footwear. J Physiol Anthropol Appl Human Sci 2001; 20: 241–246 28 McWhorter JW, Landers MR, Wallmann HW, Altenburger P, Berry K, Tompkins D, Higbee C. The effects of loaded, unloaded, dynamic and static activities on foot volumetrics. Phys Ther Sport 2006; 7: 81–86

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29 McWhorter JW, Wallmann HW, Landers MR, Altenburger B, LaPortaKrum L, Alternburger P. The effects of walking, running and shoe size on foot volumetrics. Phys Ther Sport 2003; 4: 87–92 30 Meana M, Alegre LM, Elvira JL, Aguado X. Kinematics of ankle taping after a training session. Int J Sports Med 2008; 29: 70–76 31 Mundermann A, Stefanyshyn DJ, Nigg BM. Relationship between footwear comfort of shoe inserts and anthropometric and sensory factors. Med Sci Sports Exerc 2001; 33: 1939–1945 32 O’Donovan G, Blazevich AJ, Boreham C, Cooper AR, Crank H, Ekelund U, Fox KR, Gately P, Giles-Corti B, Gill JM, Hamer M, McDermott I, Murphy M, Mutrie N, Reilly JJ, Saxton JM, Stamatakis E. The ABC of Physical Activity for Health: a consensus statement from the British Association of Sport and Exercise Sciences. J Sports Sci 2010; 28: 573–591 33 Rosendal L, Langberg H, Skov-Jensen A, Kjaer M. Incidence of injury and physical performance adaptations during military training. Clin J Sport Med 2003; 13: 157–163 34 Saltzman CL, Nawoczenski DA, Talbot KD. Measurement of the medial longitudinal arch. Arch Phys Med Rehabil 1995; 76: 45–49 35 Shiang TY, Lee SH, Lee SJ, Chu WC. Evaluating different footprint parameters as a predictor of arch height. IEEE Eng Med Biol Mag 1998; 17: 62–66 36 Stick C, Stofen P, Witzleb E. On physiological edema in man’s lower extremity. Eur J Appl Physiol 1985; 54: 442–449 37 Tsung BY, Zhang M, Fan YB, Boone DA. Quantitative comparison of plantar foot shapes under different weight-bearing conditions. J Rehabil Res Dev 2003; 40: 517–526 38 Vrijens J. Entrenamiento razonado del deportista [Reasoned Sports Training]. Barcelona (Spain) 2006 39 Werner RA, Gell N, Hartigan A, Wiggermann N, Keyserling WM. Risk factors for foot and ankle disorders among assembly plant workers. Am J Ind Med 2010; 53: 1233–1239 40 Witana CP, Feng J, Goonetilleke RS. Dimensional differences for evaluating the quality of footwear fit. Ergonomics 2004; 47: 1301–1317 41 Witana CP, Xiong S, Zhao J, Goonetilleke RS. Foot measurements from three-dimensional scans: a comparison and evaluation of different methods. Int J Ind Ergon 2006; 36: 189–807 42 Wunderlich RE, Cavanagh PR. Gender differences in adult foot shape: implications for shoe design. Med Sci Sports Exerc 2001; 33: 605–611 43 Xiong S, Goonetilleke RS, Zhao J, Li W, Witana CP. Foot deformations under different load-bearing conditions and their relationships to stature and body weight. Anthropological Science 2009; 117: 77–88

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