Effect of strength-to-weight ratio on the time taken to perform a sled-towing exercise

Abstract

Sled-towing exercises are effective at developing sprint acceleration in sports. In a sled-towingexercise the time taken by an athlete to tow the sled over a given distance is affected by the weight of the sled, the frictional properties of the running surface, and the physiological capacities of the athlete. To accurately set the training intensity for an athlete, the coach needs a detailed understanding of the relationships between these factors. Our study investigated the relationship between the athlete’s strength-to-weight ratio and the rate of increase in sled-towing time with increasing sled weight. Twenty-two male athletes performed a one-repetition maximum (1RM) half-squat and sled-towing exercises over 20 m with sleds of various weights. The strength of the correlation between 1RM half-squat performance (normalized to bodyweight) and the rate of increase in sled-towing time with increasing sled weight was interpreted using the Pearson product-moment correlation coefficient. As expected, we found substantial inter-athlete differences in the rate of increase in time with increasing sled weight, with a coefficient of variation of about 21% and 17% for sled-towing times over 10 and 20 m, respectively. However, the rate of increase in sled-towing time showed no correlation with normalized 1RM half-squat performance (r = –0.11, 90% confidence interval = –0.45 to 0.26; and r = –0.02, 90% confidence interval =–0.38 to 0.34, for sled-towing times over 10 and 20 m, respectively). These results indicate that inter-athlete differences in the rate of increase in sled-towing time with increasing sled weight are not likely to be due to differences in strength-to-weight ratio. Instead, we recommend the weight of the sled be scaled according to the athlete’s power-to-weight ratio.