Effect of weighted sled towing on sprinting effectiveness, power and force-velocity relationship

Abstract

This study aimed to compare the components of force-velocity (F-V) and power-velocity (P-V) profiles and the mechanical effectiveness of force application (or force ratio–RF) among various sled-towing loads during the entire acceleration phase of a weighted sled sprint. Eighteen sprinters performed four 50-m sprints in various conditions: unloaded; with a load corresponding to 20% of the athlete’s body mass (BM); with a load of 30% BM; and with a load of 40% BM. Data were collected with five video cameras, and the images were digitised to obtain velocity from the derivation of the centre-of-mass position. F-V and P-V components and RF were estimated from sprinting velocity-time data for each load using a validated method that is based on an inverse dynamic approach applied to the sprinter’s centre-of-mass (it models the horizontal antero-posterior and vertical ground reaction force components) and requires only measurement of anthropometric and spatiotemporal variables (body mass, stature and instantaneous position or velocity during the acceleration phase). The theoretical maximal velocity decreased with load compared with the unloaded condition (for 20% BM: -6%, effect size (ES) = 0,38; for 30% BM: -15%, ES = 1.02; for 40% BM: -18%, ES = 1.10). The theoretical maximal horizontal force (F0) and maximal power were not different among conditions. However, power at the end of the acceleration phase increased with load (40% BM vs 0%: 72%; ES = 2.73) as well as the maximal mechanical effectiveness (12%; ES = 0.85). The linear decrease in RF was different between 30 or 40% BM and the unloaded condition (-23%; ES = 0.74 and 0.66). Better effectiveness may be developed with 40% BM load at the beginning of the acceleration and with the various load-induced changes in the components of the F-V and P-V relationships, allowing a more accurate determination of optimal loading conditions for maximizing power.

A simple method for computing sprint acceleration kinetics from running velocity data: Replication study with improved design

“…For example, previous studies used radar (Cross et al, 2015), photocells (Samozino et al, 2016;Romero-Franco et al, 2017), linear encoders (Cross et al, 2018), or high-speed video (Romero-Franco et al, 2017) after verification of the high-quality of fitting (correlation coefficient >0.99). In addition, this almost perfect fit was observed in loaded sprint conditions (Pantoja et al, 2018;Cross et al 2017b;Cross et al 2018) and for various levels of sprint performance and athletes' age and sex (Pantoja et al, 2016;Slawinski et al, 2017;Nagahara et al, 2017b), which tends to support its general validity to varying athlete's characteristics/levels and with external resistance. However, if high-quality exponential fitting of the data is not verified preceding analysis, any subsequent computations might lead to inaccurate data and conclusions (e.g.…”

Comprehensive mechanical power analysis in sprint running acceleration

“…In recent years, a simpler kinematic approach has been developed for power output computation during accelerated running . It considers the time course of a runner's velocity that can be easily measured by laser‐assisted or other time/gate devices . From the time course of BCoM velocity of our subjects, we also computed the horizontal power as proposed by Samozino et al (a) by fitting the time course of the subject's velocity with a mono‐exponential equation, which was (b) time differentiated to obtain acceleration and (c) by multiplying acceleration and velocity, mass‐specific power was obtained (W kg −1 ), (d) the mean of which was considered as horizontal power ( P horizontal ) and compared with our values (Figure ).…”

Intra and intersession reliability of the Run RocketTM in recreationally trained participants

“…The ICC for both resistance levels and both distances were very large and nearly perfect which were similar to other resisted sprint studies (range 0.79-0.98). Pantoja et al (2018) reported similar reliability values during sled towing with a group of international, national and regional sprint athletes (ICC = 0.87-0.94). Bachero-Mena and González-Badillo (2014) studied the effects of three different sled loads on acceleration in male, physically active participants (5%, 12.5% and 20% of body mass).…”

“…However, times for the sprints were measured using a stopwatch with no reported reliability. A recent study by Pantoja, Carvalho, Ribas and Peyré-Tartaruga (2018) highlighted the effect of sled towing (20, 30 and 40% of body mass) on sprint time, power and the force-velocity relationship using international, national and regional level athletes. With the greatest load, the end of the acceleration phase VOLUME --| ISSUE -| 2020 | 3 was significantly greater compared to all other loads (ES = 2.22-3.25; p<0.001).…”