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Estimation of Foot Trajectory and Stride Length during Level Ground Running Using Foot-Mounted Inertial Measurement Units
Zero-velocity assumption has been used for estimation of foot trajectory and stride length during running from the data of foot-mounted inertial measurement units (IMUs). Although the assumption provides a reasonable initialization for foot trajectory and stride length estimation, the other source of errors related to the IMU’s orientation still remains. The purpose of this study was to develop an improved foot trajectory and stride length estimation method for the level ground running based on the displacement of the foot. Seventy-nine runners performed running trials at 5 different paces and their running motions were captured using a motion capture system. The accelerations and angular velocities of left and right feet were measured with two IMUs mounted on the dorsum of each foot. In this study, foot trajectory and stride length were estimated using zero-velocity assumption with IMU data, and the orientation of IMU was estimated to calculate the mediolateral and vertical distance of the foot between two consecutive midstance events. Calculated foot trajectory and stride length were compared with motion capture data. The results show that the method used in this study can provide accurate estimation of foot trajectory and stride length for level ground running across a range of running speeds.
Journal Article
Session-to-session variations in external load measures during small-sided games in professional soccer players
The aims of this study were 1) to analyse session-to-session variations in different external load measures and 2) to examine differences in within-session intervals across different small-sided game (SSG) formats in professional players. Twenty professional soccer players (mean ± SD; age 28.1 ± 4.6 years, height 176.7 ± 4.9 cm, body mass 72.0 ± 7.8 kg, and body fat 10.3 ± 3.8%) participated in 3v3, 4v4, and 6v6 SSGs under different conditions (i.e., touch limitations and presence of goalkeepers vs. free touch and ball possession drill) over three sessions. Selected external load measures—including total distance (TD), high- intensity running (HIR, distance covered > 14.4 km.h-1), high-speed running (HSR, distance covered > 19.8 km.h-1), and mechanical work (MW, accelerations and deceleration > 2.2 m.s2)—were recorded using GPS technology during all SSG sessions. Small to large standardized typical errors were observed in session-to-session variations of selected measures across SSGs. TD.min-1 showed less variability, having a coefficient of variation (CV) of 2.2 to 4.6%, while all other selected external load measures had CV values ranging from 7.2% to 29.4%. Trivial differences were observed between intervals in TD.min-1 and HIR.min-1 for all SSGs, as well as in HSR.min-1 and MW.min-1 for most SSG formats. No reductions or incremental trends in session-to-session variations were observed when employing touch limitations or adding goalkeepers. The increased noise observed in higher speed zones (e.g., high-speed running) suggests a need for more controlled, running-based conditional drills if the aim is greater consistency in these measures.
Journal Article
Do implanted transmitters affect maximum running speed of two small marsupials?
Radiotelemetry is used to quantify behavioral, ecological, and physiological variables of animals. Because of technological limitations, relative transmitter size generally increases with decreasing body mass of the study animal, and the recommended transmitter mass of <5% of body mass often prohibits work on small mammals. We compared burst running speed, important for predator avoidance, in 2 small marsupials, Sminthopsis crassicaudata (fat-tailed dunnart) and Planigale gilesi (Giles' planigale), without and with implanted transmitters. In both species maximum running speed was not affected by the transmitters, whose mass ranged from 6.4% to 14.1% of body mass. Further, relative transmitter mass was not correlated with maximum running speed. Consequently, transmitters well above 5% of body mass need not affect locomotor performance of small terrestrial mammals.
Journal Article
Age and ultra-marathon performance - 50 to 1,000 km distances from 1969 – 2012
We investigated age and performance in distance-limited ultra-marathons held from 50 km to 1,000 km. Age of peak running speed and running speed of the fastest competitors from 1969 to 2012 in 50 km, 100 km, 200 km and 1,000 km ultra-marathons were analyzed using analysis of variance and multi-level regression analyses. The ages of the ten fastest women ever were 40 ± 4 yrs (50 km), 34 ± 7 yrs (100 km), 42 ± 6 yrs (200 km), and 41 ± 5 yrs (1,000 km). The ages were significantly different between 100 km and 200 km and between 100 km and 1,000 km. For men, the ages of the ten fastest ever were 34 ± 6 yrs (50 km), 32 ± 4 yrs (100 km), 44 ± 4 yrs (200 km), and 47 ± 9 yrs (1,000 km). The ages were significantly younger in 50 km compared to 100 km and 200 km and also significantly younger in 100 km compared to 200 km and 1,000 km. The age of the annual ten fastest women decreased in 50 km from 39 ± 8 yrs (1988) to 32 ± 4 yrs (2012) and in men from 35 ± 5 yrs (1977) to 33 ± 5 yrs (2012). In 100 km events, the age of peak running speed of the annual ten fastest women and men remained stable at 34.9 ± 3.2 and 34.5 ± 2.5 yrs, respectively. Peak running speed of top ten runners increased in 50 km and 100 km in women (10.6 ± 1.0 to 15.3 ± 0.7 km/h and 7.3 ± 1.5 to 13.0 ± 0.2 km/h, respectively) and men (14.3 ± 1.2 to 17.5 ± 0.6 km/h and 10.2 ± 1.2 to 15.1 ± 0.2 km/h, respectively). In 200 km and 1,000 km, running speed remained unchanged. In summary, the best male 1,000 km ultra-marathoners were ~15 yrs older than the best male 100 km ultra-marathoners and the best female 1,000 km ultra-marathoners were ~7 yrs older than the best female 100 km ultra-marathoners. The age of the fastest 50 km ultra-marathoners decreased across years whereas it remained unchanged in 100 km ultra-marathoners. These findings may help athletes and coaches to plan an ultra-marathoner’s career. Future studies are needed on the mechanisms by which the fastest runners in the long ultra-marathons tend to be older than those in shorter ultra-marathons.
Journal Article
The speed dynamics of different sprint and acceleration exercises applied during football training
Sprinting actions are related to decisive moments of the match and impose severe fatigue levels on football players, and are often preceded by lower intensity running patterns or walking on the field. This study aimed to compare the effects of different exercise drills on speed and acceleration dynamics. Forty Under-19 and Under-23 soccer players participated in different sprint drill conditions, quantifying their distance covered in various speed intensities covering high-speed running and sprinting patterns and their peak acceleration. The speed drills were compared across different conditions: LS30m (30 m Linear Sprint), LS40m (40 m Linear Sprint), 15BR + LS30m (15 m Bounding Run + 30 m Sprint), 15BR + LS40m (15 m Bounding Run + 40 m Sprint), and CS30m (30 m Chasing Sprint). The results of this study showed significant differences regarding maximal acceleration between the lowest value 15BR + LS30m (5.62 ± 0.83 m/s
2
) and the highest, CS30m (7.09 ± 1.25 m/s
2
;
p
= 0.001; d = − 0.88), as well as with LS30m (6.98 ± 1.43 m/s
2
;
p
= 0.003; d = − 0.59), LS40m (6.76 ± 1.60 m/s
2
;
p
= 0.002; d = − 0.69) drill. Regarding Sprint 3 distance (distance covered > 95% of maximal speed) significant differences were found between the highest, LS40m (2.42 ± 4.82 m) and the lowest 15BR + LS30m (0.0 ± 0.00;
p
= 0.057; d = − 0.52) as well LS30m (0.90 ± 3.31 m;
p
= 0.017; d = − 0.37) drill. These results suggest that the capacity to reach peak acceleration is mediated by how the athlete approaches the linear sprint. Moreover, the LS40m was observed to be a drill that successfully exposes the athlete to their peak speed compared to the LS30m and 15BR + 30 m drills. Therefore, it should be considered the use of LS40m drill for training prescriptions for developing speed or hamstring conditioning. Finally, the CS30m drill exposed the athletes to the highest peak acceleration, probably due to the visual stimulus provided by the opponent, which might have elicited higher levels of motivation for the chasing player. Briefly, in the LS40m, athletes cover more distance above 95% of maximum speed, while the CS30m seems to be more effective for achieving higher accelerations.
Journal Article