Temporal Parameters of Foot Roll-over during Walking Straight

Ahead and Stepping over Obstacles in Postmenopausal Women

David Silva

, Ronaldo Gabriel

, Maria Moreira

, João Abrantes

and Aurélio Faria

Department of Sport Sciences, Exercise and Health, Center for the Research and Technology of Agro-Environmental and

Biological Sciences (CITAB), University of Trás-os-Montes and Alto Douro, Vila Real, Portugal

Department of Sport Sciences, Exercise and Health, Research Center in Sports Sciences, Health and Human Development

(CIDESD), University of Trás-os-Montes and Alto Douro, Vila Real, Portugal

MovLab, Centre for Research in Applied Communication, Culture, and New Technologies (CICANT), University Lusófona

of Humanities and Technologies, Lisboa, Portugal

Department of Sport Science, Research Center in Sports Sciences, Health and Human Development (CIDESD), University

of Beira Interior, Covilhã, Portugal

1 OBJECTIVES

One-third of postmenopausal women experience a

fall annually (Randell et al., 2001). Stepping over

obstacles have been associated with a greater risk of

falls and injury then straight ahead tasks (Zhang et

al., 2011).

The path of locomotion usually is not perfectly

level and clear, therefore the human locomotor

system needs to be able to adapt to avoid obstacles

safely and negotiate uneven terrain (Austin et al.,

1999, Sparrow et al., 1996).

There is a lack of plantar pressure studies that

evaluate the effect of stepping over obstacles during

walking despite its frequent occurrence during daily

activities, which also induce important modifications

in foot behaviour. Therefore, the purpose of this

study was to compare, the temporal characteristics

of foot roll-over of the trailing limb between the

following tasks: straight ahead task (SAT); and

obstacle task (OT).

2 METHODS

2.1 Subjects

Thirty-one postmenopausal women (age, 58.2 ± 6.5

years; height, 156.3 ± 4.2 cm; weight, 70.8 ± 15.3

kg, and BMI, 28.9± 5.8 kg/m

) participated in the

study. A physician performed an evaluation of the

medical history before the subjects were included in

the study and informative written consent was

obtained after fully disclosure of the nature of the

study. The evaluation used the Bone Estrogen

Strength Training (BEST) Study (Center for

Physical Activity and Nutrition, 2004) and the

Greene scale (Greene, 2008). Subjects with (1)

diabetes and/or signs associated with neuropathy

were excluded, as well as subjects with (2) acute

foot pain and deformities, (3) severe lower extremity

trauma, and (4) coordination problems that resulted

of eye disorders.

2.2 Instrumentation/Procedures

Plantar pressure parameters were evaluated by the

Footscan platform (1m×0.4 m, 8192 sensors, RSscan

International, Olen, Belgium) at 250 Hz using the 2-

step protocol (Bus and Lange, 2005). Each subject

was instructed to perform barefoot two tasks: SAT

and OT (30% height of leg length) as illustrated in

Figure 1.

In the present study the right foot (trailing limb)

was the dominant foot for all of the subjects, and

was used as the supporting foot during the stepping

over the obstacle.

Figure 1: Performed Tasks. Straight ahead task (SAT) and

obstacle task (OT).

Before measurements, the individuals practiced

walking at a self-selected speed over the pressure

platform for a period of ten minutes. Five valid trials

(Bus and Lange, 2005), were collected. A trial was

discarded if foot contact with the pressure platform

was incomplete, if the participant targeted the

platform, or if the coefficient of variation of the

Silva D., Gabriel R., Moreira M., Abrantes J. and Faria A..

Temporal Parameters of Foot Roll-over during Walking Straight Ahead and Stepping over Obstacles in Postmenopausal Women.

 2014 SCITEPRESS (Science and Technology Publications, Lda.)

duration of contact was greater than 4%. This final

criterion was employed to minimize the effect of

walking speed on the data (Burnfiel et al., 2004,

Warren et al., 2004).

The initial contact time (IC), final contact time

(FC) and duration of contact (DC) was obtained for

10 anatomical pressure areas during foot roll-over.

The areas considered were: medial and lateral heel

(HM, HL), metatarsal areas (M1–M5), midfoot

(MF), hallux (T1) and toes (T2–5).

Five instants of foot roll-over (Figure 2) were

determined: (FFC-first foot contact, instant the foot

made first contact with the pressure platform; FMC-

first metatarsal contact, instant when one of the

metatarsal heads contacted the pressure platform;

FFF-forefoot flat, first instant when all the heads of

the metatarsals made contact with the pressure

platform; HO-heel off, instant the heel region lost

contact with the pressure platform and; LFC-last

foot contact, last contact of the foot on the platform).

Based on these instants four phases were established

(De Cock et al., 2005): initial contact phase (ICP;

between FFC and FMC), forefoot contact phase

(FFCP; between FMC and FFF), foot flat phase

(FFP; between FFF and HO) and forefoot push off

phase (FFPOP; between HO and LFC).

Figure 2: Instants and phases of foot roll-over.

3 RESULTS

The results were obtained and analysed between

tasks (table 1).

Table 1: Relative initial, final and duration contact, and

values of FMC, FFF, ICP and LFC between tasks.

Variables SAT OT

IC MF (%)

7,8 ± 3,3 4,1 ± 2,1

IC M5 (%)

20,2 ± 9,1 11,7 ± 9,4

IC M4 (%)

15,4 ± 5,9 7,8 ± 4,1

IC M3 (%)

15,5 ± 5,8 8,3 ± 3,5

IC M2 (%)

20,2 ± 7,6 11,8 ± 5,8

Table 1: Relative initial, final and duration contact, and

values of FMC, FFF, ICP and LFC between tasks. (cont.).

Variables SAT OT

IC M1 (%)

32,2 ± 10,5 21,7 ± 10,5

IC T2-5 (%)

60,3 ± 12,5 44,5 ± 14,7

IC T1 (%)

50,3 ± 15,6 32,2 ± 15,4

FC M5 (%)

86 ± 4,9 92,2 ± 6,4

FC M4 (%)

93,2 ± 2,1 98,4 ± 1,6

FC M3 (%)

95,5 ± 1,6 98,9 ± 1,1

FC M2 (%)

95,7 ± 1,5 98,4 ± 1

FC M1 (%)

94,1 ± 1,5 96,1 ± 1,7

FC T1 (%)

99,9 ± 0,4 98,4 ± 1,7

DC M5 (%)

65,9 ± 12,1 80,5 ± 10,2

DC M4 (%)

77,8 ± 6,5 90,6 ± 3,9

DC M3 (%)

79,9 ± 5,9 90,6 ± 3,6

DC M2 (%)

75,5 ± 7,5 86,7 ± 6

DC M1 (%)

61,8 ± 10,5 74,4 ± 10,9

DC T2-5 (%)

37,8 ± 12,9 49,4 ± 15,6

DC T1 (%)

49,4 ± 15,6 66,2 ± 15,2

FMC (%)

13,7 ± 4,6 6,9 ± 2,9

FFF (%)

33,7 ± 9,9 23,5 ± 11,1

ICP (%)

13,7 ± 4,6 6,9 ± 2,9

LFC (ms)

643 ± 60 853 ± 87

Data are mean ±SD. Independent T-Test

(T)

, Man-Whitney U test

(U)

P < 0.05.

4 DISCUSSION

The purpose of this study was to compare, the

temporal characteristics of foot roll-over of the

trailing limb between the straight ahead task SAT

and obstacle task OT.

Regarding the last foot contact, the results

showed that the foot presented a longer duration

during the OT. Such results are explained by the

decreased speed (Austin et al., 1999, Begg et al.,

1998, Sparrow et al., 1996) during stepping over

obstacles and increased duration of the step (Begg et

al., 1998, Sparrow et al., 1996).

A longer foot contact duration might be related

to the need to generate and absorb greater forces

associated with stepping over obstacles (Begg et al.,

1998).

When comparing both tasks, the results indicated

that the initial contact of the foot areas, with the

exception of the heel areas, was made earlier during

stepping over obstacles.

Begg et al. (1998), stated that during stepping

over obstacles one of the roles of trailing limb is to

arrest the body’s forward momentum. To undertake

such task, there is an increase of the anterior–

posterior maximum braking forces, that take place

earlier during the stance phase (Begg et al., 1998).

The authors (Begg et al., 1998) also indicated

that when stepping over obstacles, during the weight

acceptance phase, the trailing limb presented an

increased first vertical peak force which also take

place earlier during the stance phase. Therefore, the

earlier initial contact of several areas of the foot

could be related to the deceleration of the body’s

forward momentum and the need to control the

increased braking forces produced when stepping

over obstacles.

The final contact of the foot areas M1-M5 was

made later during the OT. Begg et al. (1998), found

that during crossing obstacles, the trailing limb

increased the second peak vertical forces and the

timing in which it takes place was more lately on the

stance phase. The authors consider that those results

could be explained by one of the trailing limb roles,

which is to generate sufficient vertical forces to

ensure adequate vertical elevation of the center of

mass, during the obstacle clearance by the leading

limb. The results obtained in the present study may

therefore indicate that the later final contact of the

M1-M5 areas may occur due to its role during the

stance phase on the OT.

A greater contact duration of the areas M1-M5,

T2-5 and T1 were also found during OT. According

to Chen and Lu (2006), Begg et al. (1998), a

successful and safe obstacle crossing requires not

only sufficient foot clearance of the swing leading

limb but also the stability of the body provided

mainly by the stance of trailing limb. The results of

the present study seem to be in accordance with the

previous statement, since several areas of the foot

presented a longer contact duration during the stance

phase, which could be a solution to the increased

balance demands during obstacle crossing.

Concerning the instants and phases of plantar

pressure of the trailing limb, the statistical outcomes

indicate that on the OT, the FMC and FFF occurred

significantly earlier and the duration of the ICP was

significantly shorter. The reason for the earlier FMC

and FFF and shorter ICP during the OT is related

with the earlier initial contact time of the metatarsal

areas previously explained.

The main findings were: the trailing limb

presented a longer foot contact duration on the OT;

during the OT the metatarsals areas showed an

earlier initial contact, a later final contact and an

increased duration contact, suggesting that these

areas play a greater role in the initial break, the

control of stability and on propulsion when

compared with the straight-ahead walking.

ACKNOWLEDGEMENTS

This work is supported by national funds by FCT -

Portuguese Foundation for Science and Technology,

under the project PEst-OE/AGR/UI4033/2014.

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