Cahill, MJ, Oliver, JL, Cronin, JB, Clark, K, Cross, MR, Lloyd, RS, and Lee, JE. Influence of resisted sled-pull training on the sprint force-velocity profile of male high-school athletes. J Strength Cond Res 34(10): 2751–2759, 2020—Although resisted sled towing is a commonly used method of sprint-specific training, little uniformity exists around training guidelines for practitioners. The aim of this study was to assess the effectiveness of unresisted and resisted sled-pull training across multiple loads. Fifty-three male high-school athletes were assigned to an unresisted (n = 12) or 1 of 3 resisted groups: light (n = 15), moderate (n = 14), and heavy (n = 12) corresponding to loads of 44 ± 4 %BM, 89 ± 8 %BM, and 133 ± 12 %BM that caused a 25, 50, and 75% velocity decrement in maximum sprint speed, respectively. All subjects performed 2 sled-pull training sessions twice weekly for 8 weeks. Split times of 5, 10, and 20 m improved across all resisted groups (d = 0.40–1.04, p < 0.01) but did not improve with unresisted sprinting. However, the magnitude of the gains increased most within the heavy group, with the greatest improvement observed over the first 10 m (d ≥ 1.04). Changes in preintervention to postintervention force-velocity profiles were specific to the loading prescribed during training. Specifically, F0 increased most in moderate to heavy groups (d = 1.08–1.19); Vmax significantly decreased in the heavy group but increased in the unresisted group (d = 012–0.44); whereas, Pmax increased across all resisted groups (d = 0.39–1.03). The results of this study suggest that the greatest gains in short distance sprint performance, especially initial acceleration, are achieved using much heavier sled loads than previously studied in young athletes.

The purpose of this study was to examine the usefulness of individual load–velocity profiles and the between-athlete variation using the decrement in maximal velocity (Vdec) approach to prescribe training loads in resisted sled pulling in young athletes. Seventy high school, team sport, male athletes (age 16.7 ± 0.8 years) were recruited for the study. All participants performed one un-resisted and four resisted sled-pull sprints with incremental resistance of 20% BM. Maximal velocity was measured with a radar gun during each sprint and the load–velocity relationship established for each participant. A subset of 15 participants was used to examine the reliability of sled pulling on three separate occasions. For all individual participants, the load–velocity relationship was highly linear (r > 0.95). The slope of the load–velocity relationship was found to be reliable (coefficient of variation (CV) = 3.1%), with the loads that caused a decrement in velocity of 10, 25, 50, and 75% also found to be reliable (CVs = <5%). However, there was a large between-participant variation (95% confidence intervals (CIs)) in the load that caused a given Vdec, with loads of 14–21% body mass (% BM) causing a Vdec of 10%, 36–53% BM causing a Vdec of 25%, 71–107% BM causing a Vdec of 50%, and 107–160% BM causing a Vdec of 75%. The Vdec method can be reliably used to prescribe sled-pulling loads in young athletes, but practitioners should be aware that the load required to cause a given Vdec is highly individualized.

RESISTED SPRINTING IN THE FORM OF SLED PUSHING AND PULLING ARE POPULAR TRAINING METHODS TO IMPROVE SPEED CAPABILITY, ALTHOUGH RESEARCH HAS BEEN BIASED TOWARD INVESTIGATING THE EFFECTS OF SLED PULLING. PRACTITIONERS NEED TO UNDERSTAND WHETHER THE SLED PUSH AND PULL OFFER DIFFERENTIAL TRAINING EFFECTS, AND HENCE THEIR UTILITY IN INFLUENCING SPRINT KINEMATICS AND KINETICS FOR TARGETED ADAPTATION. FURTHERMORE, THERE ARE A NUMBER OF RECENT DEVELOPMENTS IN LOADING AND ASSESSMENT THAT WARRANT DISCUSSION, GIVEN THE IMPACT OF THESE TECHNIQUES ON UNDERSTANDING THE LOAD-VELOCITY RELATIONSHIP AND OPTIMIZING HORIZONTAL POWER OUTPUT. FINALLY, SOME THOUGHTS REGARDING LOAD PRESCRIPTION ARE SHARED WITH THE READER.

Sled pushing is a commonly used form of resisted sprint training; however, little empirical evidence exists, especially in youth populations. The aim of this study was to assess the effectiveness of unresisted and resisted sled pushing across multiple loads. Fifty high school athletes were assigned to an unresisted (n = 12), or 3 resisted groups; light (n = 14), moderate (n = 13), and heavy (n = 11) resistance that caused a 25%, 50%, and 75% velocity decrement in maximum sprint speed, respectively. All participants performed two sled‐push training sessions twice weekly for 8 weeks. Before and after the training intervention, the participants performed a series of jump, strength, and sprint testing to assess athletic performance. Split times between 5 and 20 m improved significantly across all resisted groups (all P < .05, d = 0.34‐1.16) but did not improve significantly with unresisted sprinting. For all resisted groups, gains were greatest over the first 5 m (d = 0.67‐0.84) and then diminished over each subsequent 5 m split (d = 0.08‐0.57). The magnitude of gains in split times was greatest within the heavy group. Small but non‐significant within‐group effects were found in pre to post force‐velocity profiles. There was a main effect of time but no interaction effects as all groups increased force and power, although the greatest increases were observed with the heavy load (d = 0.50‐0.51). The results of this study suggest that resisted sled pushing with any load was superior to unresisted sprint training and that heavy loads may elicit the greatest gains in sprint performance over short distances.

Resisted sled pushing is a popular method of sprint-specific training; however, little evidence exists to support the prescription of resistive loads in young athletes. The purpose of this study was to determine the reliability and linearity of the force-velocity relationship during sled pushing, as well as the amount of between-athlete variation in the load required to cause a decrement in maximal velocity (Vdec) of 25, 50 and 75%. Ninety (n=90) high school, male athletes (age 16.9 ± 0.9 years) were recruited for the study. All participants performed one unresisted and three sled-push sprints with increasing resistance. Maximal velocity was measured with a radar gun during each sprint and the load-velocity relationship established for each participant. A subset of 16 participants examined the reliability of sled pushing on three separate occasions. For all individual participants, the load-velocity relationship was highly linear (r > 0.96). The slope of the load-velocity relationship was found to be reliable (CV = 3.1%), with the loads that cause a decrement in velocity of 25, 50 and 75% also found to be reliable (CVs = <5%). However, there was large between-participant variation (95%CI) in the load that caused a given Vdec, with loads of 23-42% body mass (%BM) causing a Vdec of 25%, 45-85%BM causing a Vdec of 50% and 69-131%BM causing a Vdec of 75%. The Vdec method can be reliably used to prescribe sled-push loads in young athletes, but practitioners should be aware that the load required to cause a given Vdec is highly individualized.

Although assisted sprinting has become popular for training maximum velocity, the acute effects are not fully understood. To examine this modality, 14 developmental male sprinters (age: 18.0 6 2.5 years, 100-m personal best: 10.80 6 0.31 seconds) performed maximal trials, both unassisted and assisted with a motorized towing device using a load of 7 kg (9.9 6 0.9% body mass). Significant increases in maximum velocity (+9.4%, p # 0.001, d = 3.28) occurred due to very large increases in stride length (+8.7%, p # 0.001, d = 2.04) but not stride rate (+0.7%, p = 0.36, d = 0.11). Stride length increased due to small changes in distance traveled by the center of mass during ground contact (+3.7%, p # 0.001, d = 0.40) combined with very large changes in distance traveled by the center of mass during flight (+13.1%, p # 0.001, d = 2.62). Although stride rate did not demonstrate significant between-condition differences, the combination of contact and flight time was different. Compared to unassisted sprinting, assisted sprinting caused small but significant decreases in contact time (25.2%, p # 0.001, d = 0.49) and small but significant increases in flight time (+3.4%, p , 0.05, d = 0.58). Sprinting with motorized assistance elicited supramaximal velocities with decreased contact times, which may represent a neuromuscular stimulus for athletes attempting to enhance sprinting performance. Future research is needed to investigate the effects of this modality across various assistive loads and athletic populations, and to determine the longitudinal efficacy as a training method for improving maximum-velocity sprinting performance.

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There is a renewed interest is resisted sled training (RST); however, little uniformity exists regarding the integration of best practices in RST for young athletes. This article reviews the prescription of load, methods of RST, and the integration of sprint-specific periodized training blocks during the preparatory phase to elicit the greatest gains within different phases of sprint performance such as early acceleration, late acceleration, and the transition to maximum velocity. A targeted, long-term approach to RST may enable more effective development of speed in young athletes.