Differences in run-up, take-off, and flight characteristics: successful vs. unsuccessful high jump attempts at the IAAF world championships.

Studies previously conducted on high jump have yielded important information regarding successful performance. However, analyses in competitive scenarios have often disregarded athletes' unsuccessful attempts. This study aimed to investigate the biomechanical differences between successful and unsuccessful jumps during competition. High-speed video footage (200 Hz) was obtained from 11 athletes during the 2018 Men's World Athletics Indoor Championship Final. From each athlete, one successful (SU) and one unsuccessful (UN) jump at the same bar height were included in the analysis, leaving seven athletes in total. Following whole-body 3D manual digitization, several temporal and kinematic variables were calculated for the run-up, take-off, and flight phases of each jump. During SU jumps, athletes raised the center of mass to a greater extent (p < 0.01) from take-off. Touchdown in SU jumps was characterized by a faster anteroposterior velocity (p < 0.05), lower backward lean (p < 0.05), and changes in joint angles for the stance and trail limbs (p < 0.05). Athletes also shortened the final contact time during SU jumps (p < 0.01) after producing a longer flight time in the final step of the run-up (p < 0.05). Elite-level high jumpers undertake a series of adjustments to successfully clear the bar after UN jumps. These adjustments reinforce the importance of the run-up in setting the foundations for take-off and bar clearance. Furthermore, the findings demonstrate the need for coaches to be mindful of the adjustments required in stance and trail limbs when looking to optimize feedback to athletes during training and competition.

Changes in running biomechanics during the 2017 IAAF world championships men's 1500 m final.

The aim of this study was to analyze key kinematic, spatiotemporal, and global mechanical characteristics in world-class middle-distance racing. Eight men were recorded halfway along the home straight on the second, third, and final laps in the 2017 IAAF World Championship 1500 m final. Video data (150 Hz) from three high-definition camcorders were digitized to calculate relevant variables, subsequently analyzed in relation to running speed and finishing position. Better-placed finishers had greater hip extension at initial contact and through late stance, greater knee excursion throughout stance, and longer overstriding distances. Step length did not change with faster speeds as runners relied on increasing step frequency, but the highest-finishing athletes had longer contact phases and greater fluctuations in speed through the step cycle, which were related to higher normalized peak horizontal forces. The best athletes also had lower leg stiffnesses and vertical stiffnesses. The extended contact phase and greater compression could allow for more sustained force production, enabling better acceleration and maintenance of sprinting speed, indicating a trade-off between aerobic energetic efficiency and anaerobic power capacity. Coaches should note that these factors, as well as the best athletes' greater overstriding distances, show that elite 1500 m runners might prioritize a technique that favors running speed over economy.

Feasibility of OpenPose markerless motion analysis in a real athletics competition.

This study tested the performance of OpenPose on footage collected by two cameras at 200 Hz from a real-life competitive setting by comparing it with manually analyzed data in SIMI motion. The same take-off recording from the men's Long Jump finals at the 2017 World Athletics Championships was used for both approaches (markerless and manual) to reconstruct the 3D coordinates from each of the camera's 2D coordinates. Joint angle and Centre of Mass (COM) variables during the final step and take-off phase of the jump were determined. Coefficients of Multiple Determinations (CMD) for joint angle waveforms showed large variation between athletes with the knee angle values typically being higher (take-off leg: 0.727 ± 0.242; swing leg: 0.729 ± 0.190) than those for hip (take-off leg: 0.388 ± 0.193; swing leg: 0.370 ± 0.227) and ankle angle (take-off leg: 0.247 ± 0.172; swing leg: 0.155 ± 0.228). COM data also showed considerable variation between athletes and parameters, with position (0.600 ± 0.322) and projection angle (0.658 ± 0.273) waveforms generally showing better agreement than COM velocity (0.217 ± 0.241). Agreement for discrete data was generally poor with high random error for joint kinematics and COM parameters at take-off and an average ICC across variables of 0.17. The poor agreement statistics and a range of unrealistic values returned by the pose estimation underline that OpenPose is not suitable for in-competition performance analysis in events such as the long jump, something that manual analysis still achieves with high levels of accuracy and reliability.

The Association Between Hip-Shoulder Separation Angles and Technique Characteristics in World-Class High Jumpers.

Hip-shoulder separation (H-Ssep) has been widely researched in many sporting activities (e.g., golf) to provide information on the contribution of torso rotation to performance and injury. Although it is necessary for high jumpers to generate significant long-axis rotation to successfully clear the bar, limited information exists on H-Ssep for high jump athletes. As such, this study aimed to (a) characterize the H-Ssep of world-class high jump athletes during competition, (b) determine if differences exist between male and female athletes and (c) to examine the relationship between H-Ssep and the biomechanical parameters used to describe high jump technique. Twenty-nine world-class high jumpers (17 males, 12 females) were video recorded (frame rate: 120-200 Hz) during the 2017 and 2018 World Athletics Championship finals. H-Ssep was quantified at touchdown (TD) and take-off (TO) following manual digitizing (SIMI motion) and a number of other common biomechanical parameters were computed. The observed levels of H-Ssep at TD (-46±12°) and TO (16 ±11°) were in line with those reported previously for other sports. The magnitude of H-Ssep varied between individuals and showed significant associations with other approach and take-off characteristics. Significant differences in H-Ssep were not evident between male and female athletes despite significant differences in other performance- and technique-related parameters. These findings highlight the divergent take-off characteristics of world-class performers and their reliance on hip-shoulder interactions when generating long axis rotation. Coaches should be mindful of the mechanical and physical consequences of H-Ssep when developing technical models, conditioning interventions and coaching strategies.

Kinematic and Temporal Differences Between World-Class Men's and Women's Hurdling Techniques.

This study aimed to compare joint kinematics and center of mass parameters throughout hurdle clearance between world-class men and women sprint hurdlers, who were competing in a World Championships final. This was the first study to present time-series kinematic data around hurdle clearance, and given the technical ability of the athletes analyzed, it can be used as a template when analyzing the technique of other athletes in similar competitions and training. Video data were collected of the 16 finalists at the 2017 IAAF World Championships using four high-speed cameras (150 Hz). Video files were continuously digitized manually from touchdown before hurdle clearance to toe-off after landing around the sixth hurdle for men and the fifth hurdle for women, and sex-based comparisons were made at key discrete time points using independent t-tests, and throughout the entire hurdle phase using statistical parametric mapping. When calculated relative to hurdle height, the women's center of mass height was significantly greater than the men's throughout the full analyzed sequence (p < 0.001). Men also displayed more hip flexion in the lead leg at take-off before hurdle clearance (p = 0.029) as well as a more extended knee joint at intervals during flight and upon landing (p ≤ 0.037). Women completed the hurdle phase in a significantly shorter time than men (~11% difference, p < 0.001). Finally, women seemed to be more efficient by maintaining and even exceeding their entry velocity for the first 40% of the hurdle phase. These results show a lower technical demand for the women to successfully negotiate hurdle clearance, thus providing further evidence to support the argument that the women's hurdle height is too low for their performance capabilities and should be raised in senior competition.

Biomechanics of World-Class 800 m Women at the 2017 IAAF World Championships.

The 800 m race challenges the aerobic and anaerobic energy systems, and athletes adopt a technique that allows for running efficiency as well as sprinting speeds. The aim of this novel study was to compare important kinematic variables between the two laps of the 2017 IAAF World Championships women's final. Video data (150 Hz) were collected of all eight finalists on both laps at a distance approximately 50 m from the finish line along the home straight. Running speed, step length, cadence, temporal variables, sagittal plane joint angles, and shank angle at initial contact were measured. Running speed was faster on lap 2 (p = 0.008) because of large increases in cadence (p = 0.012). These higher cadences resulted in large decreases in contact times (p = 0.031) and in flight times (p = 0.016) on lap 2. Greater knee flexion and ankle plantarflexion (p ≤ 0.039) at initial contact on lap 2 seemed partly responsible for shorter swing times (p = 0.016), and which accompanied a decrease in shank angle at initial contact from lap 1 (7°) to a more vertical position on lap 2 (4°) (p = 0.008). Coaches should note that the need for higher cadence, horizontal impulse production during shorter contact times, and the adoption of forefoot striking require strength and neural system training to allow for athletes to increase cadence during the sprint finish. Increasing cadence (and not step length) was the driving factor for faster finishing speeds in the women's 800 m.

Kinematics of the Final Approach and Take-Off Phases in World-Class Men and Women Pole Vaulters.

The pole vault is a highly technical event where the athletes must successfully convert horizontal velocity during the run-up to vertical velocity at take-off. The aim of this study was to compare the kinematics of men's and women's world-class pole vaulting. Video data were collected of the best clearances by 14 men and 11 women at the 2018 IAAF World Indoor Championships using three high-speed cameras (200 Hz). Running velocity, step lengths, step times, and pole angles were measured during the run-up; during take-off, distance from the plant box, angle and velocity of take-off, and relative positions of the foot and hands were measured. Men achieved greater clearance heights with faster run-ups, faster take-off velocities and higher hand grip positions (all p < 0.001), with each of the last three steps longer for men when expressed as absolute values (all p < 0.001), but not when expressed relative to stature. There were no differences in run-up pole angles, step times, take-off angle, take-off contact time or time from pole plant to take-off. Women differed in their approach and take-off for characteristics affected by stature and strength, such as fewer run-up steps, shorter take-off distances, and lower grip heights. These lower grips result from a shorter, lighter pole, and this disadvantage was greater than slower run-up velocities. Coaches should therefore note that sex-based differences occur in the pole vault that result from anthropometric differences, but which do not negate the adoption of similar technical models of vaulting.

Asymmetry in sprinting: An insight into sub-10 and sub-11 s men and women sprinters.

We assessed sprint mechanical asymmetry in world-class competitors and evaluated whether inter-limb sex-based differences in sprinting mechanics exist. The eight finalists in the men's and women's 100 m events at the 2017 IAAF World Championships were studied. Five high-speed cameras (150 Hz) were used to capture two consecutive steps of the whole body between 47.0 m and 55.5 m from the start, while four additional cameras (250 Hz) focussed on the lower extremities. A total of 33 spatio-temporal, touchdown and toe-off joint angles, and horizontal and vertical foot velocity parameters were extracted through three-dimensional analysis. Group mean asymmetry scores were assessed using the symmetry angle (SA) where scores of 0% and 100% represent perfect symmetry and perfect asymmetry, respectively. Although considered generally low (SA <3% for 22 out of 33 parameters), the magnitude of mechanical asymmetry varied widely between sprinters of the same sex. However, there was no mean SA scores difference between men and women for any stride mechanical parameters (all p ≥ 0.064). Asymmetry scores were inconsistent between parameters and phases (touchdown vs toe-off instants), and sprinting mechanics were generally not related to asymmetry magnitudes. In summary, low to moderate asymmetry is a natural phenomenon in elite sprinting. Asymmetry was inconsistent between parameters and competitors during near maximum velocity running, yet mean values for a given parameter generally did not differ between sexes. Sprinters' performances were not related to their SA scores.

Biomechanics of World-Class Men and Women Hurdlers.

The sprint hurdle events require athletes to cross ten hurdles between the start and finish line. The height of the hurdles, and the distances between them, differ for men and women, possibly resulting in technical differences. The aim of this study was to provide a kinematic comparison of in-competition hurdle technique for world-class men and women hurdlers. Video data were collected for the 16 finalists in the 100 m and 110 m hurdles events at the 2017 IAAF World Championships using four high-speed cameras (150 Hz), focusing on the sixth hurdle for the men and fifth for the women. Center of mass (CM) position, joint angles, step lengths and clearance times were compared between sexes at key events before, during and after hurdle clearance. The hurdle height was ~7% higher for men when calculated as a proportion of stature (p < 0.001). This discrepancy in relative hurdle height provided women with a kinematic and mechanical advantage over men as they took off farther from the hurdle (relative to hurdle height) (p < 0.001), leading to a lower and more efficient flight parabola. Women were also able to maintain longer relative step lengths after hurdle clearance and showed minimal vertical oscillation of the CM in the stance phases before and after the hurdle compared with men. The lower relative hurdle heights in the women's event provide a less demanding task, and thus these findings present preliminary evidence to those coaches who advocate revising the women's hurdle heights in competition.

Kinematic factors associated with start performance in World-class male sprinters.

The aim was to investigate the kinematic factors associated with successful performance in the initial acceleration phase of a sprint in the best male athletes in the World at the 2018 World Indoor Athletics Championships. High speed video (150 Hz) was captured for eight sprinters in the men's 60 m final. Spatio-temporal and joint kinematic variables were calculated from the set position to the end of the first ground contact post-block exit (GC1). Normalised average horizontal external power (NAHEP) defined performance and was the dependent variable for a series of regression analyses. Clear relationships were found between GC1 NAHEP and 10-m time, 60-m time, change in velocity, acceleration and contact time in the first ground contact (r = -0.74, -0.64, 0.96, 0.91 and -0.56, respectively). Stepwise multiple linear regression of joint kinematic variables in the first ground contact revealed that trunk angle at take-off and thigh separation angle at take-off explained nearly 90% of variation in GC1 NAHEP (R2 = 0.89). The athletes' projection at take-off with a forward leaning trunk and large thigh separation is characteristic therefore of excellent initial acceleration performance and this will be a good visual guide for technical coaching instruction. This was the first study of its kind to adopt such a research design in a World-class sample in a representative environment. Future studies that combine detailed kinematic and kinetic data capture and analysis in such a setting will add further insight to the findings of this investigation.

The head is an excellent proxy for the whole body center of mass when measuring running velocity in competition.

Whole body digitizing used to calculate whole body center of mass (CM) variables from competitions is particularly time-consuming, and "shortcut" methods that substitute for it could expediate the calculation of spatiotemporal variables. The aim of this study was to measure the appropriateness of using the head as a proxy for the CM when calculating running velocity in competition. Fifty-six athletes in the IAAF World Championship marathons were recorded using two high-definition cameras (50 Hz) on two laps so that 112 running sequences were analyzed. The video files were imported into SIMI Motion and manually digitized. The horizontal running velocity during one gait cycle was obtained using four methods: horizontal velocity of the CM; horizontal velocity of the head (raw data); horizontal velocity of the head (Butterworth filtered); and horizontal displacement of the head (a single measurement using SIMI Motion 3D still image measurement) divided by time taken. In comparison with the criterion CM measurements for mean horizontal velocity, the filtered head data had the best 95% confidence interval (95% CI) for intraclass correlation coefficient (ICC) (0.999 - 1.000), the least bias (-0.006 m/s), and the lowest root mean square difference (0.024 m/s). The filtered head condition also had the best 95% CI for ICC for maximum and minimum horizontal velocities during the stride (>0.988) and the lowest bias (-0.001 m/s and -0.003 m/s, respectively). With the application of an appropriate filter, the head is thus an excellent proxy for whole body CM velocity calculations.

Footstrike patterns and race performance in the 2017 IAAF World Championship men's 10,000 m final.

Midfoot- (MFS) and forefoot-striking (FFS) runners usually switch to rearfoot-striking (RFS) during marathons. However, world-class runners might resist modifications during shorter races. The purpose of this study was to analyse footstrike patterns, ground contact times and running speeds in a World Championship men's 10,000 m final. Footstrike patterns and contact times of the top 12 finishing men (24 ± 5 years) were recorded (150 Hz) during laps 1, 5, 11, 15, 20 and 25. Split times for each 100-m segment were obtained. No RFS patterns were observed; there was no difference between the number of FFS and MFS athletes at any distance (p ≥ 0.581) and no change in the proportions of FFS and MFS occurred (p = 0.383). No link between race performance and footstrike pattern appeared given the similar number who used FFS or MFS and their similar finishing times. Despite slower running speeds and longer contact times in the middle of the race (p ≤ 0.024), no effect on footstrike patterns occurred. The prevalence of anterior footstrike patterns in this world-class race reflects the capability of maintaining fast paces (>22 km/h). Changes in footstrike pattern might accompany the physiological and neuromuscular effects of fatigue over longer distances.

Men's and Women's World Championship Marathon Performances and Changes With Fatigue Are Not Explained by Kinematic Differences Between Footstrike Patterns.

World-class marathon runners make initial contact with the rearfoot, midfoot or forefoot. This novel study analyzed kinematic similarities and differences between rearfoot and non-rearfoot strikers within the men's and women's 2017 IAAF World Championship marathons across the last two laps. Twenty-eight men and 28 women, equally divided by footstrike pattern, were recorded at 29.5 and 40 km (laps 3 and 4, respectively) using two high-definition cameras (50 Hz). The videos were digitized to derive spatiotemporal and joint kinematic data, with additional footage (120 Hz) used to identify footstrike patterns. There was no difference in running speed, step length or cadence between rearfoot and non-rearfoot strikers during either lap in both races, and these three key variables decreased in athletes of either footstrike pattern to a similar extent between laps. Men slowed more than women between laps, and overall had greater reductions in step length and cadence. Rearfoot strikers landed with their foot farther in front of the center of mass (by 0.02-0.04 m), with non-rearfoot strikers relying more on flight distance for overall step length. Male rearfoot strikers had more extended knees, dorsiflexed ankles and hyperextended shoulders at initial contact than non-rearfoot strikers, whereas female rearfoot strikers had more flexed hips and extended knees at initial contact. Very few differences were found at midstance and toe-off. Rearfoot and non-rearfoot striking techniques were therefore mostly indistinguishable except at initial contact, and any differences that did occur were very small. The spatiotemporal variables that differed between footstrike patterns were not associated with faster running speeds and, ultimately, neither footstrike pattern prevented reductions in running speeds. The only joint angle measured at a specific gait event to change with fatigue was midswing knee flexion angle in men. Coaches should thus note that encouraging marathon runners to convert from rearfoot to non-rearfoot striking is unlikely to provide any performance benefits, and that training the fatigue resistance of key lower limb muscle-tendon units to avoid decreases in step length and cadence are more useful in preventing reductions in speed during the later stages of the race.

Better water jump clearances were differentiated by longer landing distances in the 2017 IAAF World Championship 3000 m steeplechase finals.

The aim of this novel study was to analyse key kinematic variables during the water jump clearance amongst world-class 3,000 m steeplechasers. Thirteen men and 13 women were recorded as they negotiated the last water jump in the 2017 IAAF World Championship finals. Video footage (100 Hz) was recorded using three high-definition camcorders to derive spatiotemporal data; spatial data were normalised to athletes' statures. The time to cover the distance from 4.5 m before the water jump barrier to 4.5 m after ("9 m time") was used to describe overall clearance success. Although men had longer approach and exit step lengths, there were no differences when the data were normalised; by contrast, men's landing distances were greater in both absolute and relative terms. Women's shorter landing distances meant negotiating deeper water when exiting, with those athletes with longer landing distances running faster 9 m times (r = - 0.87). Obtaining a high position on the barrier (clearance height) was correlated with longer landing distances (men: r = 0.75, women: r = 0.71) and could indicate better technique. Coaches should note that although technical proficiency in all aspects of the clearance is imperative, optimising the athlete's landing distance is paramount.

Most marathon runners at the 2017 IAAF World Championships were rearfoot strikers, and most did not change footstrike pattern.

The aim of this study was to analyze footstrike patterns in elite marathon runners at the 2017 IAAF World Championships. Seventy-one men and 78 women were analyzed in their respective races. Athletes' footstrike patterns were recorded (120 Hz) at approximately 8.5, 19, 29.5 and 40 km ("Laps 1 - 4") and categorized as either rearfoot (RFS), midfoot or forefoot striking; the latter two were classified together as non-rearfoot striking (NRFS). The most common footstrike pattern was RFS, with proportions never less than 54% of men or 67% of women at any distance. There were no sex-based differences for proportion of footstrike patterns, and there were no differences between footstrike proportions when comparing the top and bottom 50% of men finishers, or between women during Laps 1 and 2. A greater proportion of the top 50% of women maintained NRFS than amongst the bottom 50%. The proportion of RFS increased with distance run in the men's race, although more than 75% of athletes across both marathons had consistent footstrike patterns between laps (79 RFS and 36 NRFS). As most athletes were RFS (including the top four finishing men), there appears to be no clear advantage to NRFS in marathon running. Coaches should note that it is normal for elite marathon runners to be either RFS or NRFS; however, forefoot striking was rare. The high proportion of athletes who maintained their footstrike pattern reflected individualized preferences for a given footstrike pattern.

World-Class Male Sprinters and High Hurdlers Have Similar Start and Initial Acceleration Techniques.

The effect of the inclusion of a high hurdle 13.72 m after the start line on elite sprint start and initial acceleration technique has yet to be investigated or understood. This highly novel study addresses that lack of information in an exceptional manner, through detailed biomechanical analysis of the world's best sprint and hurdle athletes, with data collected in situ at the 2018 IAAF World Indoor Championships, held in Birmingham, UK. High speed videos (150 Hz) were compared for eight sprinters and seven hurdlers for the start and initial acceleration phase of the finals of the men's 60 m and 60 m hurdles. Temporal and kinematic data were supplemented by vector coding analysis to investigate mechanisms by which these world-class athletes translate their centres of mass (CM) up to the fourth touchdown post-block exit. The sprinters and hurdlers coordinated their lower limb and trunk movement in a similar manner throughout the start and initial acceleration phases, which contributes new conceptual understanding of the mechanisms that underpin start and initial acceleration performance. Differences between groups were initiated from block set-up, with the hurdlers utilising a larger block spacing, but with the front block nearer to the start line than sprinters. Even after accounting for stature, the biggest differences in the raising of the CM occurred during the block phase, with hurdlers greater than sprinters (difference in vertical CM displacement scaled to stature = -0.037, very large effect size). Subsequent flight phases showed the biggest differences in the translation of the CM, in part due to longer flight times in the hurdlers, whilst the techniques of the two groups generally converged during the ground contact phases of initial acceleration. In highlighting that similar techniques are used by world-class sprinters and hurdlers, despite differing task constraints, this study has provided invaluable insights for scientists, coaches, and athletes, that will inform further developments in understanding and practice across both sprints and hurdles.