The effect of the bend on technique and performance during maximal effort sprinting

TLDR: The results indicate that the roles of the left and right steps may be functionally different during bend sprinting, and this specificity should be considered when designing training programmes.

Abstract: This study investigated changes in performance and technique that occur during maximal effort bend sprinting compared with straight-line sprinting under typical outdoor track conditions. Utilising a repeated measures design, three-dimensional video analysis was conducted on seven male sprinters in both conditions (bend radius: 37.72 m). Mean race velocity decreased from 9.86 to 9.39 m/s for the left step (p = 0.008) and from 9.80 to 9.33 m/s for the right step (p = 0.004) on the bend compared with the straight, a 4.7% decrease for both steps. This was mainly due to a 0.11 Hz (p = 0.022) decrease in step frequency for the left step and a 0.10 m (p = 0.005) reduction in race step length for the right step. The left hip was 4.0° (p = 0.049) more adducted at touchdown on the bend than the straight. Furthermore, the bend elicited significant differences between left and right steps in a number of variables including ground contact time, touchdown distance and hip flexion/extension and abduction/adduction angles. The results indicate that the roles of the left and right steps may be functionally different during bend sprinting. This specificity should be considered when designing training programmes.

Figures

Table I. Left and right step group mean values (± SD) and significant differences for performance descriptors on the straight and bend. 622

Table II. Left and right step group mean values (± SD) and significant differences for technique variables on the straight and bend. 625

Full text

The effect of the bend on technique and performance
during maximal effort sprinting
CHURCHILL, Sarah M. <http://orcid.org/0000-0001-9542-3812>, SALO, Aki
I.T. and TREWARTHA, Grant
Available from Sheffield Hallam University Research Archive (SHURA) at:
http://shura.shu.ac.uk/10043/
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publisher's version if you wish to cite from it.
Published version
CHURCHILL, Sarah M., SALO, Aki I.T. and TREWARTHA, Grant (2015). The effect
of the bend on technique and performance during maximal effort sprinting. Sports
Biomechanics, 14 (1), 106-121.
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1
THE EFFECT OF THE BEND ON TECHNIQUE AND PERFORMANCE
DURING MAXIMAL EFFORT SPRINTING
Sarah M. Churchill
a, b
, Aki I.T. Salo
a, 1
and Grant Trewartha
a
a)
Sport, Health and Exercise Science, University of Bath, Bath, United Kingdom
b)
Department of Sport, Sheffield Hallam University, Sheffield, United Kingdom
1
Corresponding author:
Dr Sarah M. Churchill Dr Aki I. T. Salo
Sport, Health and Exercise Science Sport, Health and Exercise Science
Applied Biomechanics Suite Applied Biomechanics Suite 1.309
University of Bath University of Bath
BATH, BA2 7AY BATH, BA2 7AY
UNITED KINGDOM UNITED KINGDOM
Tel. +44-1225-383569
Email: A.Salo@bath.ac.uk
Dr Grant Trewartha
Sport, Health and Exercise Science
Applied Biomechanics Suite 1.306
University of Bath
BATH, BA2 7AY
UNITED KINGDOM
Tel. +44-1225-383055
Email: G.Trewartha@bath.ac.uk
b) Dr Churchill has moved to Department of Sport, Collegiate Hall A115, Sheffield Hallam
University, Collegiate Crescent, SHEFFIELD, S10 2BP, UNITED KINGDOM, Tel. +44-
114-225-5921, Email: S. Churchill@shu.ac.uk

2
THE EFFECT OF THE BEND ON TECHNIQUE AND PERFORMANCE
1
DURING MAXIMAL EFFORT SPRINTING
2
3
Abstract 4
This study investigated changes in performance and technique that occur during maximal 5
effort bend sprinting compared to straight-line sprinting under typical outdoor track 6
conditions. Utilising a repeated measures design, three-dimensional video analysis was 7
conducted on seven male sprinters in both conditions (bend radius: 37.72 m). Mean race 8
velocity decreased from 9.86 m/s to 9.39 m/s for the left step (p = 0.008) and from 9.80 m/s 9
to 9.33 m/s for the right step (p = 0.004) on the bend compared to the straight, a 4.7% 10
decrease for both steps. This was due mainly to a 0.11 Hz (p = 0.022) decrease in step 11
frequency for the left step and a 0.10 m (p = 0.005) reduction in race step length for the right 12
step. The left hip was 4.0° (p = 0.049) more adducted at touchdown on the bend than the 13
straight. Furthermore, the bend elicited significant differences between left and right steps in 14
a number of variables including ground contact time, touchdown distance and hip 15
flexion/extension and abduction/adduction angles. The results indicate that the roles of the 16
left and right steps may be functionally different during bend sprinting. This specificity 17
should be considered when designing training programmes. 18
(Word count: 198) 19
20
Keywords: Three-dimensional kinematics, track and field, 200 m race, curve, lean 21
22
23

3
Introduction 24
Winning margins in athletic sprint events can be a fraction of a second.
This means that even 25
relatively small improvements in performance can have meaningful effects on an athlete’s 26
finishing position in a race. As such, numerous biomechanical analyses of sprinting have 27
focussed on understanding and improving performance during straight-line sprint running 28
(e.g. Kunz & Kaufmann, 1981: Mann, 1985; Bezodis, Kerwin & Salo, 2008). During sprint 29
events longer than 100 m on a standard outdoor track, athletes are required to run more than 30
half the race around the bend (International Association of Athletics Federations, 2008). It is 31
generally accepted that the necessity to generate centripetal acceleration in order to follow the 32
curved path on the bend has a detrimental effect on running speed (Usherwood and Wilson, 33
2006). However, bend sprinting has received relatively little attention compared with 34
straight-line sprinting in the research literature, despite the bend portion of the race being a 35
potentially important source of performance improvement. 36
37
The aim of a sprint race is for competitors to cover the given horizontal distance in the 38
shortest possible time. As such, horizontal velocity is ultimately the most important factor in 39
terms of success. Maximal effort velocity has been shown to decrease on bends of small radii 40
compared with straight-line sprinting (Chang & Kram, 2007), but bends of small radii are not 41
representative of typical outdoor tracks used in athletic sprint events. Experimental studies of 42
bend running conducted on radii specific to outdoor athletic tracks have been limited to 43
submaximal effort running (~6 m/s; Hamill, Murphy, & Sussman, 1987), to the acceleration 44
phase of sprinting (Stoner & Ben-Sira, 1979), or have been performed on surfaces dissimilar 45
to a standard track surface (Green, 1985). Thus, the effect of the bend on the maximal speed 46
phase of sprinting has not been adequately examined. 47
48

4
Horizontal velocity is the product of step length and step frequency, which are themselves 49
influenced by a number of further determinants including ground contact time and flight time 50
(Hay, 1993). Stoner and Ben-Sira (1979) reported significant decreases in step length during 51
the acceleration phase of sprinting on the bend compared with straight-line acceleration. 52
Further analysis of the results presented by Stoner and Ben-Sira (1979) demonstrate a 53
reduction in step frequency for the left step and an increase in step frequency for the right 54
step on the bend, suggesting the effect of the bend may be asymmetrical. A mathematical 55
model to predict indoor 200 m race times suggested that velocity decreases on the bend were 56
due to an increase in ground contact time which leads to a reduction in step frequency 57
(Usherwood & Wilson, 2006). However, this model did not permit changes in step length and 58
did not provide experimental data to evaluate it. Empirical studies of maximal bend sprinting 59
are needed in order to fully understand the effect of the bend on the determinants of velocity. 60
61
Previous kinematic studies of bend sprinting have generally been concerned with differences 62
in whole body performance descriptors (Stoner & Ben-Sira, 1979; Usherwood & Wilson, 63
2006), such as velocity, step length and step frequency. A number of straight-line sprint 64
studies have conducted sagittal-view two-dimensional (2D) video analyses of segment 65
kinematics (Mann & Hagy, 1980; Kunz & Kaufmann, 1981; Mann & Herman, 1985; 66
Hamilton, 1993; Bushnell & Hunter, 2007; Bezodis, Salo, & Trewartha, 2012). Although a 67
reasonable assumption for straight-line sprinting, a 2D analysis is inappropriate for bend 68
sprinting, due to the additional importance of actions in the non-sagittal planes, such as 69
inward lean. Despite the potential importance of non-sagittal motion, a three-dimensional 70
(3D) kinematic analysis is missing from the bend sprinting literature. 71
72

Frequently asked questions

Q1. What are the contributions mentioned in the paper "The effect of the bend on technique and performance during maximal effort sprinting" ?

4 This study investigated changes in performance and technique that occur during maximal 5 effort bend sprinting compared to straight-line sprinting under typical outdoor track 6 conditions. Furthermore, the bend elicited significant differences between left and right steps in 14 a number of variables including ground contact time, touchdown distance and hip 15 flexion/extension and abduction/adduction angles. 

Q2. What is the reason why the speed reductions on the bend were significant?

Since absolute speed measures 309 the actual performance of the athlete regardless of the path travelled, this is important 310 because it showed that there was a real decrease in performance on the bend and that 311 reductions in race velocities were not simply due to athletes following paths longer than the 312 race line. 

Q3. How many LED displays were placed in each camera view?

118 Two sets of synchronised 20 LED displays (Wee Beasty Electronics, UK) were placed with 119 one in each camera view during data collection. 

Q4. What is the significance of the kinematic analysis in the bend sprinting literature?

Despite the potential importance of non-sagittal motion, a three-dimensional 70 (3D) kinematic analysis is missing from the bend sprinting literature. 

Q5. What is the effect of the bend on the determinants of velocity?

Empirical studies of maximal bend sprinting 59 are needed in order to fully understand the effect of the bend on the determinants of velocity. 

Q6. Why did one athlete not complete a third trial?

Due to one athlete not completing a third trial as well as some recording and synchronisation 124 issues that were visible only after the data collection session has finished, one athlete had 125 only one usable bend trial available and two further athletes had two bend trials available for 126 further analysis. 

Q7. What is the reason for the decrease in sprinting performance on the bend?

care should be taken to ensure training does not introduce asymmetries 524 between left and right which may be detrimental to straight-line sprinting performance. 

Q8. What is the reason for the decrease in performance of the bend sprinters?

a need to increase ground contact time in order to generate centripetal 350 force during bend sprinting may not be the only explanation for the decrease in performance. 

Q9. What was the measure of the turn of the com during the bend trials?

201 Turn of the CoM during ground contact was calculated for the bend trials as a measure of 202 how much turning ‘into’ the bend an athlete achieved during each ground contact. 

Q10. What would allow athletes to experience the requirement to withstand and generate large forces while in the altered?

This would allow athletes 437 to experience the requirement to withstand and generate large forces whilst in the altered 438 frontal plane orientation, which includes a tendency towards adduction of the left hip and 439 abduction of the right hip, rather than focusing on training primarily in the sagittal plane. 

Q11. What was the digitisation of the human body?

136 137 For the running trials, a 20-point model of the human body was digitised consisting of the top 138 of the head, the joint centres of the neck (C7 level), shoulders, elbows, wrists, hips, knees, 139 ankles, second metatarsophalangeal (MTP) joints and the tips of the middle finger and 140 running spikes. 

Q12. What is the effect of reducing ground contact time on the bend?

335 Usherwood and Wilson (2006) suggested that increasing ground contact time, with swing 336 time remaining constant, reduced step frequency and thus velocity on the bend. 

Q13. What is the effect of the asymmetrical bend on sagittal plane hip angles?

it is probable that the observed asymmetrical 411 effect of the bend on sagittal plane hip angles, such as the left hip being more extended at 412 take-off and more flexed at peak flexion than the right hip on the bend (p < 0.05, Table II), 413 were caused by altered orientation in the frontal plane. 

Q14. How many segments of the foot were added to the forefoot and rearfoot?

The 151 mass of a typical spiked sprinting shoe (0.2 kg; Hunter, Marshall & McNair, 2004) was added 152 to the mass of each foot, with 15% and 85% of the shoe mass added to the forefoot and 153 rearfoot segments, respectively, in line with the ratio of the mass of the foot for these 154 segments.