#Biomechrunning:From Koroivos of Elis to Usain of Jamaica…and into the Future

Sprint running is one of the oldest athletic events that has dominated the athletics scene since the first ancient Olympic games in 776 BC. Has this happened through an evolution process where this competitive gait has managed to adapt and modernise itself to remain contemporary? If this is the case, how do the sprinters of the 21st century compare to the ancient runners competing barefoot on plain dirt surface? What does the future of sprinting look like? Having spent over two decades studying sprint running through a biomechanical lens, Professor Bissas will philosophise about this pure, uncomplicated and aesthetic mode of human locomotion that obeys unfailingly the laws of classical mechanics

#Biomechrunning:From Koroivos of Elis to Usain of Jamaica…and into the Future

Sprint running is one of the oldest athletic events that has dominated the athletics scene since the first ancient Olympic games in 776 BC. Has this happened through an evolution process where this competitive gait has managed to adapt and modernise itself to remain contemporary? If this is the case, how do the sprinters of the 21st century compare to the ancient runners competing barefoot on plain dirt surface? What does the future of sprinting look like? Having spent over two decades studying sprint running through a biomechanical lens, Professor Bissas will philosophise about this pure, uncomplicated and aesthetic mode of human locomotion that obeys unfailingly the laws of classical mechanics

MUSCLE ACTIVITY OF THE STANCE KNEE IN ELITE RACE WALKERS

The purpose of this study was to compare knee muscle activity in race walkers with different knee extension patterns. Three international athletes walked over two force plates recording at 1000 Hz. Video data were simultaneously recorded at 100 Hz; the digitised data were combined with the force data to calculate net muscle moments and joint powers. EMG testing was carried out on three muscles which cross the knee. The two walkers with legal techniques had similar moment and power patterns, whereas the non-legal walker experienced a longer period of eccentric flexor moment at the beginning of stance, which may have affected his ability to extend his knee correctly. After this, all three athletes experienced a period of isometric contraction at the knee. Achieving correct technique requires both strength endurance exercises and mobility development

GROUND REACTION FORCES OF NATIONAL LEVEL RACE WALKERS

The purpose of this study was to measure and analyse ground reaction force variables during race walking. Fourteen national level race walkers, eight men and six women, walked at race pace over two force plates recording at 1000 Hz. Men and women had comparable force trace patterns except for the magnitude of the weight-loading peak force. There were similarities with normal ground reaction force patterns, although the drop in vertical force at midstance and subsequent rise in vertical push-off force typical of normal walking were not observed. This was considered to be due to the straightened knee rule of race walking and the need to reduce vertical displacment and flight time. The medial forces were greater than those in normal walking and this may be related to the frontal plane motions of the pelvis

THE CONTRIBUTION OF THE FLIGHT PHASE IN ELITE RACE WALKING

Although race walkers are not permitted a visible flight phase, previous research has found that most competitors do experience very brief losses of contact. The purpose of this study was to assess the role of the flight phase in elite race walking. Seventeen international athletes race walked over two force plates recording at 1000 Hz. Video data were simultaneously recorded at 100 Hz and used to calculate kinematic variables such as step length. The mean flight time was 0.030 s (± .011) while the mean distance travelled during this phase was 0.12 m (± .05). It was calculated that without flight times, athletes would have slower mean velocities, particularly if mean cadence remained the same. However, the contribution of flight phases in race walking does not just allow for greater step lengths and faster speeds, but also more time for lower limb repositioning

The use of various strength-power tests as predictors of sprint running performance

Aim: The aim of the present study was to assess the relationship between various strength-power tests and maximal running velocity parameters. Methods: Nine trained males were tested on four separate occasions. On the first occasion the maximum running velocity (MRV), stride rate (SR) and stride length (SL) were measured over 35 m. On the second occasion maximal vertical jumps (squat jump [SJ], standing broad jump [SBJ], counter movement jump [CMJ] and drop jumps [DJ] from heights of 30, 50 and 80 cm) were performed on a force platform. On the third occasion the maximal bilateral isometric force (MBIF) of leg extensors and the force time characteristics (f-t 10-30%, f-t 10-60% and f-t 10-90%) were determined using a leg extension machine connected to a force plate. On the final fourth occasion peak anaerobic power was measured via repeated 6 sec maximum cycle sprints. Pearson product-moment correlation coefficients were calculated for all the aformentioned parameters. Results: The correlation coefficients showed that MRV correlated significantly with f-t 10-60% and DJ 30 (r=-0.73 and r=0.73, P<0.05 respectively). In addition, SR and SL showed significant relationships with f-t 10-60% (r=-0.82, P<0.01 and r=0.75, P<0.05 respectively). Conclusion: The present findings suggest that the ability to produce force quickly, as measured by the time to achieve 60% of maximum voluntary contraction is related to sprinting performance, with the coefficient of determination accounting for 53% of the variance in the data. These data also show that sprinting ability is linked with DJ performance, especially the drop jump from a height of 30 cm. It is suggested that the above tests may prove useful in preparing and testing the sprinting ability and sprint specific strength levels

Combined uphill and downhill sprint running training is more efficacious than horizontal

Purpose: This study examined the effects of sprint running training on sloping surfaces (3°) on selected kinematic and physiological variables. Methods: Fifty-four sport and physical education students were randomly allocated to one of two training groups (combined uphill–downhill [U+D] and horizontal (H)) and a control group (C). Pre- and post-training tests were performed to examine the effects of 8 wk of training on the maximum running speed (MRS), step rate, step length, step time, contact time, eccentric and concentric phase of contact time (EP, CP), flight time, selected posture characteristics of the step cycle, and 6-s maximal cycle sprint test. Results: MRS, step rate, contact time, and step time were improved significantly in a 35-m sprint test for the U+D group (P < .01) after training by 4.3%, 4.3%, −5.1%, and −3.9% respectively, whereas the H group showed smaller improvements, (1.7% (P < .05), 1.2% (P < .01), 1.7% (P < .01), and 1.2% (P < .01) respectively). There were no significant changes in the C group. The posture characteristics and the peak anaerobic power (AWT) performance did not change with training in any of the groups. Conclusion: The U+D training method was significantly more effective in improving MRS and the kinematic characteristics of sprint running than a traditional horizontal training method

The biomechanics of maintaining effective force application across cycling positions

Cyclists are known to change their cycling position to reduce aerodynamic drag. Research has shown that this compromises their physical capacity to perform, but there is considerable inter-individual variability present. Proposed training specificity effects by cycling position do not explain all of the observations in the literature, so a search for other influencing parameters is warranted and might help practitioners to further optimise cycling position. This study captured full-body kinematics and 2D crank forces in 19 Time-Trial (TT) and 36 Road trained cyclists. Data in preferred and standardised cycling positions were systematically evaluated and showed that, amongst other kinematic differences, TT cyclists prefer a more forwardly positioned hip joint over Road cyclists. Despite their different setup, no effects in mechanical effectiveness were seen between the groups when tested in their preferred position. Across the standardised positions, the full cohort showed lower mechanical effectiveness when lowering trunk angle. However, significant group by position interactions showed this effect to be less extreme for the TT group. Kinematic data revealed that an increased pelvic tilt resulted in increased hip flexion and induced a more dorsiflexed ankle angle. In addition, linear hip position acutely responded to positional changes by moving forwards when the trunk angle was lowered. A more forwards hip position is thus associated with maintaining a better mechanical effectiveness in aerodynamic cycling positions. This suggests that there is potential to mitigate the effect of negative crank forces in aerodynamic positions by acutely adjusting the saddle placement to facilitate linear hip movement

A machine learning approach to identify important variables for distinguishing between fallers and non-fallers in older women

Falls are a significant ongoing public health concern for older adults. At present, few studies have concurrently explored the influence of multiple measures when seeking to determine which variables are most predictive of fall risks. As such, this cross-sectional study aimed to identify those functional variables (i.e. balance, gait and clinical measures) and physical characteristics (i.e. strength and body composition) that could best distinguish between older female fallers and non-fallers, using a machine learning approach. Overall, 60 community-dwelling older women (≥65 years), retrospectively classified as fallers (n = 21) or non-fallers (n = 39), attended three data collection sessions. Data (281 variables) collected from tests in five separate domains (balance, gait, clinical measures, strength and body composition) were analysed using random forest (RF) and leave-one-variable-out partial least squares correlation analysis (LOVO PLSCA) to assess variable importance. The strongest discriminators from each domain were then aggregated into a multi-domain dataset, and RF, LOVO PLSCA, and logistic regression models were constructed to identify the important variables in distinguishing between fallers and non-fallers. These models were used to classify participants as either fallers or non-fallers, with their performance evaluated using receiver operating characteristic (ROC) analysis. The study found that it is possible to classify fallers and non-fallers with a high degree of accuracy (e.g. logistic regression: sensitivity = 90%; specificity = 87%; AUC = 0.92; leave-one-out cross-validation accuracy = 63%) using a combination of 18 variables from four domains, with the gait and strength domains being particularly informative for screening programmes aimed at assessing falls risk

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