Gait variability and symmetry in world-class senior and junior race walkers.

TLDR: Whereas there was little mean asymmetry overall, individual analyses identified asymmetry in several athletes (symmetry angle ≥ 1.2%).

Abstract: The aim of this study was to analyse gait variability and symmetry in race walkers. Eighteen senior and 17 junior athletes race walked on an instrumented treadmill (for 10 km and 5 km, respectively) at speeds equivalent to 103% of season’s best time for 20 km and 10 km, respectively. Spatio-temporal and ground reaction force (GRF) data were recorded at 2.5 km, and at 4.5, 6.5 and 8.5 km for a subsection of athletes. Gait variability was measured using median absolute deviation (MAD) whereas inter-leg symmetry was measured using the symmetry angle. Both groups showed low variability for step length (<0.9%), step frequency (<1.1%), contact time (≤1.2%) and vertical peak force values (<5%), and neither variability nor symmetry changed with distance walked. Junior athletes were more variable for both step length (P = 0.004) and loading force (P = 0.003); no differences for gait symmetry were found. Whereas there was little mean asymmetry overall, individual analyses identified asymmetry in several ath...

Figures

Table 3. Mean (± s) symmetry angles for key spatiotemporal and kinetic variables in elitestandard senior and junior race walkers. Between-group effects were significant at P < 0.05.

Table 2. Mean (± s) MAD percentages and Cohen’s d values for key spatiotemporal and kinetic variables in elite-standard senior and junior race walkers. Between-group effects were significant at P < 0.05 (shown in bold).

Table 1. Mean (± s) values and Cohen’s d values for key spatiotemporal and kinetic variables in elite-standard senior and junior race walkers. Between-group effects were significant at P < 0.05 (shown in bold).

Full text

Citation:
Tucker, CB and Hanley, B (2017) Gait variability and symmetry in world-class senior and junior
race walkers. Journal of Sports Sciences, 35 (17). pp. 1739-1744. ISSN 0264-0414 DOI:
https://doi.org/10.1080/02640414.2016.1235793
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https://eprints.leedsbeckett.ac.uk/id/eprint/3053/
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Gait variability and symmetry in world-class senior and junior race walkers
Catherine B. Tucker and Brian Hanley
School of Sport, Carnegie Faculty, Headingley Campus, Leeds Beckett University, United
Kingdom
Correspondence details:
Catherine B. Tucker,
Fairfax Hall,
Headingley Campus,
Leeds Beckett University,
LS6 3QS,
United Kingdom.
Telephone: +44 113 812 6703
Fax: +44 113 283 3170
Email: c.b.tucker@leedsbeckett.ac.uk
Running title: Variability and symmetry in race walkers
Keywords: Elite-standard athletes, gait, spatiotemporal variables, track and field

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ABSTRACT
The aim of this study was to analyse gait variability and symmetry in race walkers. Eighteen
senior and 17 junior athletes race walked on an instrumented treadmill (for 10 km and 5 km,
respectively) at speeds equivalent to 103% of season’s best time for 20 km and 10 km,
respectively. Spatiotemporal and ground reaction force data were recorded at 2.5 km, and at
4.5, 6.5 and 8.5 km for a subsection of athletes. Gait variability was measured using median
absolute deviation (MAD) whereas inter-leg symmetry was measured using the symmetry
angle. Both groups showed low variability for step length (< 0.9%), step frequency (< 1.1%),
contact time (≤ 1.2%), and vertical peak force values (< 5%), and neither variability nor
symmetry changed with distance walked. Junior athletes were more variable for both step
length (P = 0.004) and loading force (P = 0.003); no differences for gait symmetry were
found. Whereas there was little mean asymmetry overall, individual analyses identified
asymmetry in several athletes (symmetry angle ≥ 1.2%). Importantly, asymmetrical step
lengths were found in 12 athletes and could result from underlying imbalances. Coaches are
advised to observe athletes on an individual basis to monitor for both variability and
asymmetry.

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INTRODUCTION
Race walking is part of the athletics programme contested at the Olympic Games and all
other major athletics championships. Competitions are held over 10 km (junior men and
women), 20 km and 50 km (senior men and women). This competitive form of gait is dictated
by International Association of Athletics Federations (IAAF) Rule 230.2 that states that no
visible (to the human eye) loss of contact with the ground should occur and that the knee
must be fully extended from first contact with the ground until the ‘vertical upright position’
(IAAF, 2015). Race walkers therefore need to maintain consistently legal technique with both
legs as even very brief infringements of the rules by either leg can lead to disqualification. An
understanding of both gait variability and symmetry in race walkers can thus assist coaches in
developing sound techniques, particularly in terms of what values are considered acceptable
or potentially damaging.
Movement variability in normal and pathological gait has been researched extensively to date
(e.g. Heiderscheit, Hamill, & van Emmerik, 2002; White, Agouris, Selbie, & Kirkpatrick,
1999). Relevant findings have shown that expert runners can reduce variability in achieving
key performance variables (e.g. step length and frequency) (Nakayama, Kudo, & Ohtsuki,
2010), and that a function of movement variability might be to attenuate impact shocks when
running and reduce the risk of injury (Bartlett, Wheat, & Robins, 2007). For example, it has
been shown that participants who experience patellofemoral pain have reduced variability in
lower limb joint couplings compared with healthy controls (Hamill, van Emmerik,
Heiderscheit, & Li, 1999; Heiderscheit et al., 2002). Because the rules of race walking result
in very particular biomechanical and coordinative demands (Preatoni, Ferrario, Donà, Hamill,
& Rodano, 2010), it is considered a highly technical and rather stereotyped form of gait
(Donà, Preatoni, Cobelli, Rodano, & Harrison, 2009) and so the quantification of movement

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variability within elite-standard performers is crucial to understand this unique form of gait.
In addition, race walking is an unnatural and learned skill that takes time to develop (Hanley,
Bissas, & Drake, 2014) but the existence of any variability differences between junior and
senior race walkers have not yet been researched and could highlight any developmental
issues that exist in less-trained athletes.
Symmetry refers to the exact replication of one limb’s movement by the other, with
asymmetry referring to any deviation from symmetry (Exell, Irwin, Gittoes, & Kerwin,
2012). Race walk coaches believe that legal and efficient technique requires certain
symmetry of motion and therefore subjectively monitor for inter-limb discrepancies (Salvage
& Seaman, 2011). Because gait movements can be achieved in a number of ways, with
muscle groups compensating for others if necessary (e.g. for a weak muscle on the other leg)
(Levine, Richards, & Whittle, 2012), gait asymmetry can lead to increased work demands on
one side of the body. Measurements of symmetry have been previously used in both
pathological gait research and in running to highlight increased injury risk (Exell et al.,
2012); for example, inter-leg differences of 5.7° for peak knee extension during terminal
swing and 7% for vertical peak force were found in an injured Australian Rules footballer
(Schache, Wrigley, Baker, & Pandy, 2009). It has also been found that national, non-elite
standard race walkers showed asymmetry between lower limbs, which could be a possible
risk of injury, although this was not quantified (Donà et al., 2009). Race walkers with
asymmetrical gait might also attract the attention of judges to a greater extent (Wolfe, 1998).
It is thus important to quantify the degree of symmetry between lower limbs in elite-standard
race walkers because of associations with injury risk, performance and the possibility of
appearing to have non-legal technique to the judges’ eyes.

Frequently asked questions

Q1. What are the contributions in this paper?

In this paper, the authors quantify the degree of variability between lower limbs in elite-standard race walkers. 

Q2. What are the future works in this paper?

Future research is therefore recommended to examine the effects of longer distances on variability and symmetry over the senior competitive distances of 20 km and 50 km. In this study, acceptable asymmetry was found to be below 1. 2 % as calculated using the symmetry angle, and could be used as a practically useful reference for coaches and future gait studies. Future research is recommended to examine the inter-leg differences in muscle activity patterns and magnitudes, as well as the variability and symmetry in overground race walking, including during competition to take into account typical variations in pace. As step length is associated with lower limb length ( Svedenhag & Sjödin, 1994 ) and could have affected the interpretation of results, future research should measure and examine the effect of lower limb length on variability. 

Q3. What was the effect of the instrumented treadmill on the results?

Although the instrumented treadmill was limited by its inability to measure shear forces and remove systematic noise (and hence future measurements of differences and variability in anteroposterior impulses would be particularly beneficial), itsusage in this study did prevent any conscious or unconscious targeting of the force plates by the participants and allowed for predetermined race walking speeds to be set and maintained. 

Q4. What is the definition of race walking?

Race walking is a skilled endurance event where competitors train to maintain a consistent, legal technique so that it leads to both low gait variability and asymmetry. 

Q5. What is the role of the step length in the race walker?

Whereas variations in gait movements might be beneficial, for example with regard to changing the distribution of biological stresses (Hamill et al., 1999), step length is a determining factor in race walking speed (Hanley et al., 2013) and should be maintained for optimal performance, notwithstanding that this can be achieved through variable joint patterns (Heiderscheit et al., 2002). 

Q6. What is the reason for the higher variability in the junior athletes?

The higher variability in loading force in the junior athletes could be a result of less consistent patterns of muscle activity that affect the athlete’s ability to adhere to the knee straightening requirement of Rule 230.2. 

Q7. How many steps per foot were collected?

Data were collected for 30 s at 2.5 km (where 2.5 km occurred halfway through data collection), which allowed for the collection of 46 (± 2) steps per foot in the senior athletes and 45 (± 2) steps per foot in the junior athletes. 

Q8. Why is it important to understand the differences in gait movements?

Because gait movements can be achieved in a number of ways, with muscle groups compensating for others if necessary (e.g. for a weak muscle on the other leg) (Levine, Richards, & Whittle, 2012), gait asymmetry can lead to increased work demands on one side of the body. 

Q9. What is the effect of lower limb length on variability?

As step length is associated with lower limb length (Svedenhag & Sjödin, 1994) and could have affected the interpretation of results, future research should measure and examine the effect of lower limb length on variability. 

Q10. What is the way to study the variability of overground and treadmill race walking?

It is recommended that strength and conditioning programmes are developed by coaches that take into account the repetitive,consistent gait patterns of race walking alongside the need for balanced development of both sides of the body. 

Q11. Why is race walking considered a highly technical and rather stereotyped form of gait?

Because the rules of race walking result in very particular biomechanical and coordinative demands (Preatoni, Ferrario, Donà, Hamill, & Rodano, 2010), it is considered a highly technical and rather stereotyped form of gait (Donà, Preatoni, Cobelli, Rodano, & Harrison, 2009) and so the quantification of movementvariability within elite-standard performers is crucial to understand this unique form of gait. 

Q12. What is the definition of variability in race walking?

Measuring the differences in variability between different skill standards has been used previously to appreciate whether increased or decreased movement variability is an indicator of better performers (Hiley, Zuevsky, & Yeadon, 2013). 

Q13. What was the symmetry angle of the athletes?

To determine whether a participant’s symmetry angle was significant, asymmetry between legs was determined using paired-samples t-tests (Exell et al., 2012) provided the ES was also large (i.e. a Cohen’s d value greater than 1.2). 

Q14. What was the effect size of the differences between groups?

Effect sizes (ES) for differences between groups were calculated using Cohen’s d (Cohen, 1988) and considered to be either trivial (ES: ≤ 0.20), small (0.21 – 0.60), moderate (0.61 – 1.20), large (1.21 – 2.00), or very large (> 2.01) (Hopkins, Marshall, Batterham, & Hanin, 2009). 

Q15. Why is the detection of visible loss of contact considered illegal?

This is because the detection of visible loss of contact requires only a few instances of increased flight times to be considered non-legal by judges and lead to disqualification. 

Q16. What was the correlation between speed and variability in the athletes?

Variability in loading force was one of the few variables that was associated with speed (i.e. faster athletes had less variability). 

Q17. What is the main reason why the athletes were able to achieve a lower variability in step?

This fact, combined with the need to appear consistent within the rules, means that low variability in step length and step frequency is a desirable outcome of training.