The acute effects of heavy sled towing on subsequent sprint acceleration performance

Objectives: The purpose of this study was to assess the practical use of heavy sled towing and its acute implications on subsequent sprint acceleration performance. Design and Methods: Eight healthy male varsity team sport athletes (age: 21.8±1.8years, height: 185.5±5.0cm, weight: 88.8±15.7kg, 15m sprint time: 2.66±0.13s) performed sprints under three separate weighted sled towing conditions in a randomized order. Each condition consisted of one baseline unweighted sprint (4-min pre), the sled towing sprint protocol: (1) 1x50% body mass, (2) 2x50% body mass, (3) 3x50% body mass (multiple sprints interspersed with 90s recovery), and 3 post-testing unweighted sprints thereafter (4, 8, 12-min post). All sprints were conducted over a 15m distance. Results: Significantly faster sprint times for the 3x sled towing protocol were identified following 8-min of rest (p=0.025, d=0.46, 2.64±0.15s to 2.57±0.17s). When individual best sprint times were analyzed against baseline data, significantly faster sprint times were identified following both 1x (p=0.007, d=0.69, 2.69±0.07s to 2.64±0.07s) and 3x (p=0.001, d=0.62, 2.64±0.15s to 2.55±0.14s) sled towing protocols. Within the 3x condition, all athletes achieved fastest sprint times following 8–12 min of rest. Conclusions: The findings from the present study indicate that a repeated bout of sled towing (3x50% body mass) leads to the enhancement in subsequent sprint acceleration performance, following adequate, and individualized recovery periods

Considerations for selecting field-based strength and power fitness tests to measure asymmetries

The prevalence of lower limb asymmetries has been reported in numerous studies; however, methodological differences exist in the way they can be detected. Strength and jumping-based tasks have been most commonly used to examine these differences across both athlete and non-athlete populations. The aim of this review was to critically analyze the utility of strength and jumping tests that are frequently used to measure asymmetry. Reliability, validity, and considerations for assessment are examined to enhance test accuracy and effectiveness in the quantification of asymmetries during strength and jumping-based tasks. Medline and SPORT Discus databases were used with specific search terms to identify relevant articles in both athlete and non-athlete populations. The findings of the current review indicate that assessing inter-limb differences during strength and jumping-based tasks may result in different levels of asymmetry; thus, inter-limb differences appear to be task-dependent. Consequently, quantification during both types of assessment is warranted and a selection of tests has been suggested to measure asymmetries in both strength and jumping-based tasks