What is initial acceleration?
Success in elite sport can often be determined by the smallest of margins. In many field and court sports creating an offensive advantage can often be obtained by beating an opponent in 1-2 steps. In many instances, athletes in field and court sports do not cover distances that would allow them to attain maximum velocity.20 Throughout field sport performance, the average sprint distance is only 10-20 meters and the average sprint duration is merely 2-3 seconds.17 The ability to rapidly change speed can be a defining factor in sport performance. This skillset, known as initial acceleration, can be used as a weapon for those who possess efficiency in its performance. Training recommendations to enhance initial acceleration must include strength, power, and technique practice to maximize improvement.
Why is initial acceleration unique from max velocity?
There is a growing body of literature that is separating initial acceleration and maximum velocity sprinting as separate athletic tasks. Delecluse5 has broken the 100-meter sprint event into three separate phases, each having distinct components for successful performance.14 From a technical perspective, initial acceleration mechanics involve slightly longer ground contact times, a large forward lean,10 and a greater ratio of horizontally directed ground reaction forces,12 in comparison to the more upright posture adopted at maximum velocity. These findings have led to a powerful understanding that initial acceleration should be trained for and taught differently than maximum velocity sprint mechanics. In addition, clear differences exist in the type of strength displayed during the stance phases of initial acceleration and maximum velocity sprinting. Correlational studies have shown strength qualities that strongly predict superior initial acceleration are different than those that predict maximum velocity.1,20 From a practitioner’s point of view, different exercises and technique practice can be targeted to further develop and optimize sprint performance in the desired phase.
Building Strength and Power
General exercises create a strong neuromuscular and morphological foundation on which greater performance can be built. Compound, multi-joint exercises that focus on triple extension (hips, knees, and ankles) will accomplish the outcome of improving max strength. High force strength exercises such as squats, deadlifts, or variations of these lifts, are excellent selections.19,21 High force, high velocity exercises such as Olympic lifts, Olympic lift variations, and Jump Squats are effective choices for improving power.1 Enhancing strength characteristics and movement patterns through these exercises create a beneficial foundation leading into special exercises and the technical practice of initial acceleration.
Special exercises do not completely mimic initial acceleration, but closely replicate several strength components such as rate of force production and direction of force application. The duration of the stance phase during initial acceleration is often 0.15 – 0.2 seconds, and it becomes smaller and smaller in duration with each subsequent step. With this limited time frame, it is impossible to reach maximum force production. The goal of the special exercises is to increase the rate of force development in the same relevant direction as the competition exercise. Plyometric exercises specifically accomplish this aim. Correlational studies have shown horizontal jumping to have a stronger relationship to initial acceleration in comparison to vertical jumping.6,8 An additional benefit of the horizontal jump pattern is a similar inter-muscular coordination strategy (rotation-extension) seen in the second stance phase of sprinters.7,9 Improvement in coordination strategy could allow for greater horizontal direction of force application. Exercises such as broad jumps, single leg broad jumps, bounding, and speed bounding are outstanding selections.
Improving Acceleration Technique
The practice of initial acceleration itself is an effective means of improving speed. However, practical experience and a growing branch of literature on resisted sprinting provide a compelling argument of the benefit of special exercises in improving specific components of sprint mechanics. Several studies have shown superior acceleration created through a more horizontally oriented force vector, with the orientation of this force vector being more impactful than the total force applied.13,16 Factors such as forward lean,10 touchdown distance and ankle stiffness,2 and hip extension velocity at touchdown3 are all technique applications that could lead to a more horizontally oriented force vector and faster acceleration times.
Resisted sled towing is an effective exercise that can contribute to mastering the specific components of acceleration technique. Training programs using sled towing have been shown to have a positive effect on short distance sprint times.4 Technical benefits from sled towing include increased forward lean and coordinative changes that increase horizontal power.11,18A systematic review of the resisted sprinting literature revealed a range of 10%-30% bodyweight as an effective resistance to improve sprint acceleration performance.15 Combining unweighted and weighted sprint methods may create an ideal environment to allow mastery of short distance sprint mechanics.
Review of Recommendations
- Olympic Lifts (clean and snatch)
- Olympic Lift variations (pulls and catches)
- Jump Squats with barbell
Plyometrics (horizontal jumps)
- Broad Jumps (or multiple jumps)
- Single Leg Broad Jumps (or multiple jumps)
- Bounding (short distances)
- Speed Bounding (short distances)
Resisted Sled Towing
- 10%-30% bodyweight
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Spinks, C. D., Murphy, A. J., Spinks, W. L., & Lockie, R. G. (2007). The effects of resisted sprint training on acceleration performance and kinematics in soccer, rugby union, and Australian football players. Journal of Strength and Conditioning Research, 21(1), 77.
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