Youth Pitching Stride Length is Associated with Lower Body Power and Balance

Fry KE, Pipkin A, Wittman K, Hetzel S, Sherry M. Youth baseball pitching stride length: Normal values and correlation with field testing. Sport Heal A Multidiscip Approach. 2017;9(3):205-209. doi:10.1177/1941738116679815.

Background

The shoulder and elbow receives the majority of attention when it comes to reducing pitching-related arm injuries.  However, the position and movement of the lower body may also contribute substantially to the incidence of arm injuries in baseball pitchers.  Most research related to pitching mechanics and injury has focused on professional, collegiate and high school pitchers. These studies have shown a pitcher’s stride length to be approximately 85% of their body height.   It is unclear if also holds true for youth baseball pitchers.

Purpose

The purpose of this study was to establish normative values for stride length in youth pitchers and to determine if a correlation exists between stride length and variables such as pitching experience, lower extremity balance, and lower extremity power.

Study Population

A convenience sample of 92 male youth baseball players between the ages of 9 and 14 years were enrolled.  Research participants were required to have pitched at least 1 season in organized games.  Participants were excluded if they were currently being treated for a musculoskeletal injury by a medical professional or they were unable to throw at maximal effort.

Methods

Stride length was recorded using a Dartfish video system over 3 maximal effort pitches from a mound.  A piece of white tape was placed on the pitching mound at the distance of the participant’s height as measured from the front of the pitching rubber.  Three maximal effort fastball pitches from the wind-up were included in the analysis.  Double-leg vertical jump, single-leg stance time (with the eyes closed), leg length, weight, age, and pitching experience were recorded for each research participant.

Key Results

  • The average stride length was 66.0% of body height.
  • Vertical jump (38, 95% CI: 0.19, 0.54) and pitching experience (0.36, 95% CI: 0.17, 0.53) were moderately correlated with stride length.
  • Single-leg balance time (28, 95% CI: 0.08, 0.46) was weakly correlated with stride length.
  • Age, leg length, and height showed no correlation with stride length.
  • The stride length assessment procedure and all other variables demonstrated excellent inter- and intra-rater reliability.

Study Limitations

  •  Use of a convenience sample of research participants (n=92) from one baseball organization in Wisconsin.
  • The 2-dimensional method of measuring stride length assessed distance from the heel of the lead leg. 3-dimensional methods analyze distance from the center of the ankle joint.  This could make comparisons between methods difficult.

Closing Thoughts & Practical Implications

The results of this study suggest youth pitchers with low levels of experience throw with a smaller stride length when compared to older more experienced pitchers.  Previous research has shown no difference in stride length between youth, high school, college, and professional baseball pitchers. However, the youth pitchers investigated by Fleisig et al. were slightly older than those enrolled by Fry et al. Also, Fleisig et al. included a very small sample of youth pitchers (10/231) compared to the other levels investigated.

The normative values reported by Fry et al. can be used when developing performance-based programs for youth pitchers. Clinicians and coaches can educate youth pitchers whose stride length falls outside the expected norm and make sure adequate balance, power, and strength are established before encouraging longer strides.  Strength coaches and trainers may consider emphasizing vertical jump and balance training in order to optimize stride length for pitchers.  However, from this research no cause and effect relationship can be established between any of these variables and pitching performance.

Pitching requires power generation from the lower body during the stride.  The trail leg is considered to generate the majority of this power.  Therefore, a double limb vertical jump may not be the optimal method to measure lower body power in pitchers.  Single-leg measures of power, such as a lateral to medial jump, may be more highly correlated with stride length and performance variables.  This hypothesis would need to be tested in a larger prospective investigation involving youth pitchers.    At this time, assessing single-leg balance and some measure of lower body power, should be considered when seeking to improve a youth pitcher’s stride length.

References

  1. Fleisig G, Chu Y, Weber A, Andrews J. Variability in baseball pitching biomechanics among various levels of competition. Sport Biomech. 2009;8(1):10-21. doi:10.1080/14763140802629958.

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