A Comparison of Three Different Start Techniques on Sprint Speed in Collegiate Linebackers

Abstract

Cusick, JL, Lund, RJ, and Ficklin, TK. A comparison of three different start techniques on sprint speed in collegiate linebackers. J Strength Cond Res 28(9): 2669–2672, 2014—The purpose of this study was to compare the track block start (BS), rhythm step (false step) (RS), and forward step (FS) on sprint start ability in male Division I collegiate football linebackers. Although the blocks are not practical in the sport of football, they were used as a gold standard for sprint acceleration. Sixteen collegiate football linebackers (age, 20.9 ± 1.1 years; height, 72 ± 3.0 in; mass, 97 ± 4 kg) performed 3 repetitions each of the BS, FS, and RS. Each sprint was videotaped through 5 m. The time from 0 to 2.5 m (t_2.5), 0 to 5 m (t₅), and 2.5 to 5 m (t_split) were calculated for each trial using all 3 different techniques, and the best times for each treatment was recorded. Block start resulted in significantly lower t_2.5 and t₅ compared with RS and FS. Rhythm step had significantly lower t_2.5 and t₅ compared with FS. There was no difference in t_split between any of the 3 treatments. The results indicate that using the blocks is optimal for sprint performance through 2.5 and 5 m. Rhythm step outperformed FS through both 2.5 and 5 m, suggesting that for collegiate football linebackers, RS is superior to FS.

Introduction

Sprint start ability in the context of using block starts (BS) in the sport of track and field has been studied previously (^3,13,15). Mechanically, the starting blocks maximize the forward-directed component of ground reaction force (GRF), which leads to greater forward horizontal acceleration. This research has provided valuable insight for the enhancement of track performance, but it is difficult to transfer the information to field sports where athletes must accelerate from a standing position, often with their feet parallel as to be able to move effectively in multiple directions.

To accelerate forward from a standing position without losing balance, the athlete must keep the body center of mass (COM) in the path of the GRF vector. Maximizing the forward component of GRF is beneficial to maximizing forward acceleration, but it also requires technique adaptations to account for the lesser angle with the ground that the GRF makes. This can be accomplished by leaning further forward or by moving the ground point of application of GRF rearward (stepping back). Previous studies have compared these 2 techniques with the intent of determining the optimal strategy for accelerating forward in field sports, such as football (^6,7).

The game of football involves a series of short sprints, typically ending in a collision between opposing players (¹⁴). Often, the margin of error for success can be measured in inches, and this maybe especially true for the linebacker position. Players at this position are frequently required to sprint distances of approximately 5 yd or less to make plays (¹). Minimizing the time it takes to reach the ball carrier through high rates of acceleration is crucial for the success of a linebacker in football. With greater acceleration, the linebacker can initiate contact sooner, resulting in less yards gained. For this reason, coaches and sports performance specialists concentrate on the technique of the first step used to initiate movement toward the developing play.

Anecdotally, many linebacker coaches teach their players to use the forward step (FS) technique with the first step being “positive” in nature. That is, the athlete initiates the sprint by leaning and stepping in the desired direction (⁷). It stands to reason that the same coaches teach their players to eliminate any “negative” motion, which is deemed as wasted movement because the initial motion is backward (⁵). This technique will be termed the rhythm step (RS) and is also known as the false step. In this technique, athlete steps backward, which displaces the base of the support behind the center of gravity before stepping in the desired direction (⁷).

This type of motion has been described as paradoxical in the sense that it seems counterproductive that an initial step backward could actually improve forward sprint speed through short distances (^7,11). However, it seems that this movement is very natural. When Kraan et al. (¹¹) asked 9 subjects to perform multiple sprints from a standing position (feet parallel), motion was initiated with a backward step 95% of the time. When the subjects performed sprint trials using the FS technique, the researchers observed that by false stepping, subjects demonstrated significantly greater horizontal impulses with subsequently faster sprint times. However, it should be noted that the subjects in this study were not familiar with the FS technique.

As previously mentioned, despite the evidence that the naturally occurring RS improves sprint performance via greater horizontal impulse, football coaches continue to teach their linebackers to eliminate the false step and use the FS technique. Although several studies have demonstrated that RS significantly improves sprint speed through short distances, no study has used subjects trained to use the FS technique. Therefore, the purpose of this study is to compare the effects of the RS and the FS techniques on sprint start ability in collegiate linebackers who have been coached to eliminate the RS technique and to use the FS technique exclusively.

Methods

Experimental Approach to the Problem

A counterbalanced, randomized, repeated measures design was used to determine the effects of the different techniques on sprint start ability. After familiarization of all techniques, and before the RS and FS trials, subjects performed 3 sprint BS through the prescribed distance. The BS trials served 2 purposes. First, they provided a gold standard of acceleration for each athlete. That is, using the blocks provide an indication of the greatest rate of acceleration of each subject under optimal conditions (¹¹). Second, it was hypothesized that the RS technique would result in greater sprint start ability compared with the FS technique. Assuming that this hypothesis was true, the BS trials maybe used to demonstrate the importance of greater horizontal forces and ultimately provide evidence of this mechanism for improving acceleration. After performing the BS trials, the subjects performed 3 sprints using the RS and FS techniques. The order in which they performed these 2 techniques was random and counterbalanced.

Subjects

Sixteen Football Championship Subdivision collegiate football players (age, 20.9 ± 1.1 years; height, 72 ± 3.0 in; mass, 97 ± 4 kg) were recruited for this study. All subjects verified that they had played the linebacker position in high school or in college and that they were coached to use the FS technique in games and in practice. The sports medicine staff cleared each subject for participation in all football-related activities. After the subjects were informed of the potential risks and benefits associated with the study, they signed an informed consent. The Internal Review Board of the University of Northern Iowa reviewed all study procedures.

Procedures

All sprint trials were videotaped at 60 Hz (JVC GCP-X1; Victor Corporation, Tokyo, Japan). The camera was placed 30 m away, with the optical axis perpendicular to the vertical plane through the middle of the running lane. All subjects were instructed to arrive to the testing facility in athletic clothing and running shoes during their scheduled day and time. Upon arrival, subjects performed 5 minutes of light jogging followed by a standardized 10-minute dynamic warm-up. After the warm-up, the subjects were provided instructions of how to perform each of the 3 sprint techniques. Subjects were then provided the opportunity to familiarize themselves with each technique. Subjects were limited to 3 practice trials of each technique.

After familiarization, each subject performed 3 BS trials, which were assumed to provide their best performance. After the BS trials, each subject performed 3 trials of either the RS or the FS technique, which was randomly assigned in a counterbalanced fashion. Subjects were provided 3 minutes of rest between repetitions and 5 minutes of rest before performing 3 trials of the remaining technique. The fastest of the 3 trials were recorded. Subjects were allowed to choose which leg to use to initiate movement, and all trials were started with an audio cue provided by the investigator. Subjects were provided no feedback regarding their performance for any of the trials because all sprint times were calculated via video analysis. All trials were performed on an indoor rubber track surface and were collected during the week following the end of their winter conditioning phase. Subjects were asked to refrain from performing any vigorous exercise during the 24 hours preceding their scheduled test time.

All videos were transferred to MaxTraq (Innovision Systems, Columbiaville, MI, USA) for digitization. For each video frame, the forward most point of the chin was manually digitized for all frames of the run, starting at the subject's first movement. The chin was chosen as the point of reference because it is a forward, leading landmark on the body's midline that is easy to locate frame to frame and moves forward similarly to the trunk, which is the reference used for sprint timing (²).

Reference points at the starting line, 2.5-m, and 5-m lines were used to accurately scale the x and y coordinates to compare video with real-life measurements. Then, location data were smoothed using a fourth-order zero-lag Butterworth filter at 12 Hz. The times at which the forward-most point of the chin crossed both the 2.5-m (t_2.5) and 5-m (t₅) marks were calculated by interpolation from time series horizontal position data. The time split between 2.5 and 5 m was also recorded (t_split). The best trial for each technique was recorded in seconds.

Statistical Analyses

Descriptive statistics (mean ± SD) were performed on all performance variables and can be found in Table 1. Repeated-measures multiple analysis of variance (MANOVA) was used to compare the 2 techniques (BS, FS, RS) on t_2.5, t₅, and t_split. When appropriate, separate repeated-measures analysis of variance (ANOVA) tests and paired samples t-tests were used for post hoc analyses. A Bonferroni correction was used to control for familywise error. Intraclass correlations were calculated to evaluate the test-retest reliability of the dependent variables. Effect size was estimated with η². Alpha was set at 0.05 for all tests.

Table 1: Descriptive statistics, ICC, and repeated-measures analysis of variance results for all dependent variables.

Results

The repeated-measures MANOVA indicated that there was a significant technique effect (F(6,58) = 7.43; p = 0.001; η² = 0.43), which prompted the 3 repeated-measures ANOVA as post hoc analysis. Mauchley's test of sphericity was rejected for each of the 3 separate repeated-measures ANOVA tests; therefore, a Greenhouse-Geisser penalty was assessed for these tests. The intra-class coefficient and separate repeated-measures ANOVA results can be found in Table 1. A significant technique effect was observed for t_2.5 and t₅ but not for t_split. Paired samples t-tests indicated that BS was significantly faster than both RS and FS and that RS was faster than FS for t_2.5. The same trend was observed for t₅. There were no differences between any of the techniques for t_split.

Discussion

Horizontal forces are extremely important for acceleration and sprint starts (³). It is unsurprising that BS resulted in the greatest horizontal forces because they maximize the forward horizontal component of GRF by allowing for normal forces with the blocks greater than those possible by friction with level ground.

Linebacker coaches may assume that the backward motion inherent to the RS technique is counterproductive; however, all subjects preformed better with RS than with FS. First, using the RS technique allows the player to lower the COM and have more forward lean. This allows for more horizontal force, similar to using BS. Additionally, using the RS technique allows the player to use the SSC for improving the ability to generate initial force during the first step (¹⁰). Any benefit of stretch shortening cycle in the FS technique is likely to be less, if it exists at all, because of the limited or eliminated range of stretching motion of the muscles.

The benefits of this technique are limited to the first few steps of the linebacker's motion (2.5 m) and are preserved through at least the 5-m mark. All subjects were faster through 2.5 m in the RS condition and through 5-m, but this benefit was realized in the first 2.5 m. After that, it seems that the subjects moved similarly in any of the conditions. In contrast, previous work (¹²) on female soccer players reported that the FS technique was superior to the RS technique during the first 3 steps. The authors reported that the FS technique resulted in greater velocity and displacement after each of the first 3 steps, but the RS technique had greater acceleration. If subjects using the FS technique have lower acceleration but greater velocities, then they must have taken more time to achieve this greater velocity. Furthermore, the study in question analyzed the kinematics of each step, whereas this study measured the time to achieve an absolute displacement. This method of analysis was selected because the role of the linebacker is to initiate contact with the ball carrier as soon as possible and not necessarily with the greatest velocity.

Previous work (^4,7–9) has also shown that the RS technique is superior for starting speed compared with FS. In the case of the linebacker position, it is a naturally occurring motion that is often “coached out” of the athlete. Assuming that it is desirable for players to reach their intended destination in less time, coaches should revisit this coaching strategy. The subjects in the current study had previously been coached to perform only FS but were able to realize immediate benefit by abandoning it.

Practical Applications

Assuming that linebacker coaches would want their players to arrive to their intended destination in less time, coaches should consider adjusting the amount of coaching time devoted to eliminating the RS technique with their athletes. The players in the current study had previously been coached to perform only the FS technique, but they were able to see immediate improvement in performance by reintroducing the RS technique. Football coaches should be encouraged to reexamine the technique taught for initiating motion at the linebacker position. It should be noted that these results only look at straight sprint starts and do not apply lateral movement. Future studies should examine any effects of start style on those movements as well.