Relationship of Step Width with Sprinting Performance

and Ground Reaction Forces

Ryu Nagahara, Mirai Mizutani and Akifumi Matsuo

National Institute of Fitness and Sports, 1 Shiromizu-cho, Kanoya, Kagoshima, Japan

Keywords: Running, Foot Placement, Mediolateral, Acceleration.

Abstract: The purpose of this study was to clarify the relationship of step width with sprinting performance and

ground reaction forces in order to understand the sprinting mechanism and its relation to better sprinting

performance.

1 OBJECTIVES

Relationships between sprinting performance and

spatiotemporal variables such as step frequency and

length have broadly been investigated (Debaere et

al., 2013; Hunter et al., 2004; Nagahara et al., 2014).

However, little is known about the relationship of

step width, which is the mediolateral distance

between two consecutive steps, with sprinting

performance. For example, Ito et al. (2006) showed

step width at initial acceleration and at maximal

speed phase during 100-m race. Although they

reported no significant difference in the step width

between elite and national level sprinters, the result

was obtained with the investigation at initial

acceleration and maximal speed phase. Thus, when

considering the entire acceleration phase of sprinting,

an importance of narrower or wider step width may

be able to be found.

While a study has investigated the influence of

difference in step width on some kinetic variables

during running (Brindle et al., 2014), the influence

of step width on ground reaction force (GRF) during

sprinting has never been examined. Accordingly, it

is still unknown how difference in step width

associate with GRFs during sprinting.

The purpose of this study was to clarify the

relationship of step width with sprinting

performance and GRFs in order to understand the

sprinting mechanism and its relation to better

sprinting performance.

2 METHODS

2.1 Experiment

Seventeen male athletes (mean ± SD: age, 20.7 ± 1.2

y; stature, 1.73 ± 0.03 m; body mass, 66.5 ± 4.2 kg;

personal best 100-m race time, 11.22 ± 0.28 s)

participated in this study. After warming-up, the

participants performed 60-m maximal effort

sprinting from starting blocks. GRF over 52-m

distance was sampled with 54 force platforms (1000

Hz) connected to a single computer (TF-90100, TF-

3055, TF-32120, Tec Gihan, Uji, Japan).

2.2 Data Processing

Spatiotemporal variables were calculated at every

step during 50-m distance with following procedures.

Foot strike and toe-off instants were determined with

a threshold of vertical GRF as 20 N. Based on the

foot strike and toe-off instants, step duration from

the foot strike of one leg to the next foot strike of the

other leg was calculated. Step frequency was

computed as an inverse of step duration. Foot

placement was determined as the centre of pressure

position at the middle of the support phase. Step

length and width were calculated as anterior–

posterior and mediolateral distances between two

consecutive steps. For the step width, to standardise

the value, ratio of step width relative to the

corresponding subject stature was calculated.

Running speed was calculated as a product of step

length and frequency. Step-to-step mediolateral and

anterior–posterior impulses during the support phase

Nagahara, R., Mizutani, M. and Matsuo, A.

Relationship of Step Width with Sprinting Performance and Ground Reaction Forces.

In Extended Abstracts (icSPORTS 2016), pages 8-10

over 50-m distance were calculated from GRF

signals. Moreover, effective vertical impulse during

the support phase was computed (Weyand et al.,

2000).

2.3 Statistical Analysis

To examine the relationship among variables during

accelerated sprinting with macroscopic perspective,

each variable at all steps during 50-m distance was

averaged out. Means and standard deviations were

calculated for each variable. Pearson’s product

moment correlation coefficient was calculated to test

relationship among the average variables. The

significance level was set at 5%. All statistical

values were calculated using JMP 12 statistical

software (SAS Institute Japan Ltd, Tokyo, Japan).

3 RESULTS

Averaged running speed, step length and step

frequency over 50-m distance were 8.20 ± 0.17 m/s,

1.82 ± 0.10 m, 4.45 ± 0.22 Hz, respectively. Figure 1

shows changes in step width during the entire

acceleration phase. The step width from the first step

after block clearance decreased to the 14th step (3.43

s), and the magnitude of decrease became small

afterward during the entire acceleration phase. The

averaged step width over 50-m distance and its ratio

were 0.15 ± 0.05 m and 8.9 ± 3.0 % of stature.

Table 1 shows averaged GRF variables over 50-

m distance. The medial (inward) impulse was

greater than the lateral (outward) impulse while

running on straight line.

Figure 1: Step-to-step changes in step width during

accelerated sprinting for 50-m. Black and grey lines

indicate means and standard deviations. The value at the

first step was from block clearance to the first foot strike

on the ground.

The ratio of step width was significantly

positively correlated with running speed (r = .484, P

= .049), whereas no significant correlation was

found between the ratio of step width and step length

or frequency (r = .279 and −.066, P = .279 and .800)

(Figure 2). The ratio of step width was significantly

correlated positively with medial (r = .816, P < .001),

lateral (r = .833, P < .001), net mediolateral (r

= .880, P < .001) and propulsive impulses (r = .539,

P = .026) (Figure 2). No significant relationship was

found between the ratio of step width on the one

hand and braking impulse (r = −.447, P = .072),

anterior–posterior net impulse (r = .423, P = .091)

and effective vertical impulse (r = .015, P = .955) on

the other hand.

4 DISCUSSION

This study aimed to clarify the relationships of step

width with sprinting performance and GRFs. The

results in this study demonstrate the probable

importance of relatively wide step width for better

accelerated sprinting performance. Because the

relationship of step width with both step length and

frequency did not show significant relationship, the

benefit of wider step width may have no specific

effect on longer step length or higher step frequency.

In contrast to the results of this study, Ito et al.

(2006) reported no significant difference in the step

width between elite and national level sprinters. The

reason of this discrepancy may be the difference in

methodological approach in addition to the

difference in the performance levels between our

study and the study by Ito et al. (2006), i.e. sprinting

was investigated at initial acceleration and at

maximal speed phase in the study of Ito et al. (2006),

while it was investigated over the entire 50-m

distance in this study.

The wider step width was associated with greater

medial impulse and smaller lateral impulse, as well

as greater mediolateral net impulse, indicating that

the wide step width will be accompanied by large

mediolateral velocity of body within a step.

Although the mediolateral velocity of body is

theoretically disadvantageous for better sprinting

performance, the wide step width is interestingly

also associated with greater propulsive impulse. This

result suggests that wider step width may be feasible

to produce greater propulsive force during the

support phase of sprinting. While it is difficult to

clearly explain the mechanism of how wider step

width induces greater propulsive impulse during

sprinting, one possible reason is the difference in

Relationship of Step Width with Sprinting Performance and Ground Reaction Forces

Table 1: Averaged GRF variables over 50-m distance. ML and AP mean anterior–posterior and mediolateral, respectively.

ML and AP positive values indicate medial and propulsive GRFs. ML and AP negative values indicate lateral and braking

GRFs.

Negative Positive Net

ML impulse [Ns/kg] −0.04 ± 0.03 0.13 ± 0.05 0.09 ± 0.07

AP impulse [Ns/kg] −0.11 ± 0.02 0.52 ± 0.04 0.40 ± 0.03

Effective Vertical impulse [Ns/kg] 1.02 ± 0.09

Figure 2: Relationship of step width with spatiotemporal

and GRF variables.

adductor muscle activations during hip extension

between wide or narrow stances. In the study with

squat exercise (McCaw and Melrose, 1999), the

integrated electromyography values of adductor

muscle for the ascent phase of squat with use of a

wide stance were approximately 20% greater than

that with use of narrow stance. Wiemann and Tidow

(1995) indicated the importance of adductor muscles

to generate propulsive force together with major hip

extensor muscles. Consequently, relatively wide step

width during sprinting possibly induces greater

activity of adductor muscles and better sprinting

performance through greater propulsive force.

In conclusion, the wider step width may be

beneficial for better accelerated sprinting performan-

ce. This finding may deepen the understanding of

sprinting performance and be beneficial for athletes

and coaches, trying to improve accelerated sprinting

performance.

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icSPORTS 2016 - 4th International Congress on Sport Sciences Research and Technology Support