Abstract
To establish the load–velocity relationships during backward sled pulling and compare this to forward sled pulling and determine the reliability of running speeds and associated load–velocity regression slopes in youth athletes.
Twenty-one boys (age, 13.6 ± 0.28 years old; height, 1.72 ± 0.09 m; mass, 66.1 ± 8.2 kg; maturity, 0.57 ± 0.72 years from peak height velocity) performed backward and forward resisted running on three occasions. Load–velocity relationships were established using an un-resisted sprint and resisted sled pull with loads of 25%–81% body mass (BM) in both directions, and the reliability of sprint times at each load and the load–velocity regression slopes were examined.
The load–velocity data was reliable across multiple testing occasions for backward (CV ≤ 7.2%; ICC 0.67–0.91) and forward sled pulling (CV ≤ 7.2%; ICC 0.66–0.91). From the regression lines (R2 ≥ 0.99; P ≤ 0.01), it was observed that averaged loads across the sample of 31%, 46% and 61% BM resulted in 27%, 38% and 48% decrease in velocity during backward sled pulling and 23%, 33% and 43% during forward sled pulling. Increasing backward and forward loads by ~ 13% and ~ 15% BM respectively, reliably resulted in ~ 10% decreases in velocity.
If contractile overload of the lower limbs is a focus of training then practitioners should preferentially use backward sled pulling. Both backward and forward sled pulling can be used in a similar manner regarding loading, though backward velocity is more sensitive to load and therefore overloading backward motion should be prescribed with this in mind.
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