Are the ground reaction forces altered by the curve and with the increasing sprinting velocity?

In 200- and 400-m races, 58% of the total distance to cover is in the curve. In the curve, the sprinting performance is decreased in comparison to the straight. However, the reasons for this decreased performance is not well understood. Thus, the aim of this study was to identify the kinetic parameters underpinning the sprinting performance in the curve in comparison to the straight. Nineteen experienced-to-elite curve specialists performed five sprints in the straight and in the curve (radius 41.58 m): 10, 15, 20, 30, and 40 m. The left and the right vertical, anterior-posterior, medial-lateral, and resultant ground reaction forces (respectively F V $$ {F}_{\mathrm{V}} $$ , F A - P $$ {F}_{\mathrm{A}-\mathrm{P}} $$ , F M - L $$ {F}_{\mathrm{M}-\mathrm{L}} $$ , and F TOT $$ {F}_{\mathrm{TOT}} $$ ), the associated impulses (respectively IMP V $$ {IMP}_{\mathrm{V}} $$ , IMP A - P $$ {IMP}_{\mathrm{A}-\mathrm{P}} $$ , IMP M - L $$ {IMP}_{\mathrm{M}-\mathrm{L}} $$ , and IMP TOT $$ {IMP}_{\mathrm{TOT}} $$ ) and the stance times of each side were averaged over each distance. In the curve, the time to cover the 40-m sprint was longer than in the straight (5.52 ± 0.25 vs. 5.47 ± 0.23 s, respectively). Additionally, the left and the right F A - P $$ {F}_{\mathrm{A}-\mathrm{P}} $$ and IMP A - P $$ {IMP}_{\mathrm{A}-\mathrm{P}} $$ were lower than in the straight while the left and the right F M - L $$ {F}_{\mathrm{M}-\mathrm{L}} $$ increased, meaning that the F M - L $$ {F}_{\mathrm{M}-\mathrm{L}} $$ was more medial. The left F V $$ {F}_{\mathrm{V}} $$ was also lower than in the straight while the left stance times increased to keep the left IMP V $$ {IMP}_{\mathrm{V}} $$ similar to the straight to maintain the subsequent swing time. Overall, the sprinting performance was reduced in the curve due to a reduction in the left and the right F A - P $$ {F}_{\mathrm{A}-\mathrm{P}} $$ and IMP A - P $$ {IMP}_{\mathrm{A}-\mathrm{P}} $$ , that were likely attributed to the concomitant increased F M - L $$ {F}_{\mathrm{M}-\mathrm{L}} $$ to adopt a curvilinear motion.

Sprint Acceleration Mechanical Outputs Derived from Position- or Velocity-Time Data: A Multi-System Comparison Study.

To directly compare five commonly used on-field systems (motorized linear encoder, laser, radar, global positioning system, and timing gates) during sprint acceleration to (i) measure velocity−time data, (ii) compute the main associated force−velocity variables, and (iii) assess their respective inter-trial reliability. Eighteen participants performed three 40 m sprints, during which five systems were used to simultaneously and separately record the body center of the mass horizontal position or velocity over time. Horizontal force−velocity mechanical outputs for the two best trials were computed following an inverse dynamic model and based on an exponential fitting of the position- or velocity-time data. Between the five systems, the maximal running velocity was close (7.99 to 8.04 m.s−1), while the time constant showed larger differences (1.18 to 1.29 s). Concurrent validity results overall showed a relative systematic error of 0.86 to 2.28% for maximum and theoretically maximal velocity variables and 4.78 to 12.9% for early acceleration variables. The inter-trial reliability showed low coefficients of variation (all <5.74%), and was very close between all of the systems. All of the systems tested here can be considered relevant to measure the maximal velocity and compute the force−velocity mechanical outputs. Practitioners are advised to interpret the data obtained with either of these systems in light of these results.

Center of mass velocity comparison using a whole body magnetic inertial measurement unit system and force platforms in well trained sprinters in straight-line and curve sprinting.

BACKGROUND: Sprint performance can be characterized through the centre of mass (COM) velocity over time. In-field computation of the COM is key in sprint training. RESEARCH QUESTION: To compare the stance-averaged COM velocity computation from a Magneto-Inertial Measurement Units (MIMU) to a reference system: force platforms (FP), over the early acceleration phase in both straight and curve sprinting. METHODS: Nineteen experienced-to-elite track sprinters performed 1 maximal sprint on both the straight and the curve (radius = 41.58 m) in a randomized order. Utilizing a MIMU-based system (Xsens MVN Link) and compared to FP (Kistler), COM velocity was computed with both systems. Averaged stance-by-stance COM velocity over straight-line and curve sprinting following the vertical axis (respectively VzMIMU and VzFP) and the norm of the two axes lying on the horizontal plane: x and y, approximately anteroposterior and mediolateral (respectively VxyMIMU and VxyFP) over the starting-blocks (SB) and initial acceleration (IA - composed out of the first four stances following the SB) were compared using mean bias, 95 % limits of agreements and Pearson's correlation coefficients. RESULTS: 148 stances were analyzed. VxyMIMU mean bias was comprised between 0.26 % and 2.03 % (expressed in % with respect to the FP) for SB, 5.63 % and 7.29 % over IA respectively on the straight and the curve. Pearson's correlation coefficients ranged between 0.943 and 0.990 for Vxy, 0.423 and 0.938 for Vz. On the other hand, VzMIMU mean bias ranged between 2.33 % and 4.69 % for SB, between 1.44 % and 19.95 % over IA respectively on the straight and the curve SIGNIFICANCE: The present findings suggest that the MIMU-based system tested slightly underestimated VxyMIMU, though within narrow limits which supports its utilization. On the other hand, VzMIMU computation in sprint running is not fully mature yet. Therefore, this MIMU-based system represents an interesting device for in-fieldVxyMIMU computation either for straight-line and curve sprinting.