Weighted-Ball Velocity Enhancement Programs for Baseball Pitchers: A Systematic Review

BACKGROUND: Weighted-implement training utilizing over- or underweight baseballs has increased in popularity at all levels in competitive baseball. However, there is no consensus on the efficacy or safety of these training methods. HYPOTHESIS: This systematic review was intended to answer the following questions: Does weighted-ball training improve pitching velocity? Does weighted-ball training increase the risk of injury? STUDY DESIGN: Systematic review; Level of evidence, 4. METHODS: Searches were conducted with MEDLINE, EMBASE, and the ProQuest Physical Education Index. Articles were included if the study population consisted of adult, adolescent, or youth baseball pitchers training with under- or overweight baseballs, with velocity as a measured outcome. Articles were excluded if they were review articles, examined sports other than baseball, utilized weighted implements other than baseballs, or were not published in peer-reviewed journals. Included articles were at least level 4 evidence. Data extracted for qualitative analysis included training protocol parameters (such as ball weight, number of pitches, duration of training), velocity change, and injuries or complications reported. RESULTS: A total of 4119 article titles were retrieved, of which 156 were selected for abstract review. After manual removal of duplicates, 128 abstracts were reviewed. Of these, 17 met the inclusion criteria, and the full text was obtained. After full-text review, 7 additional articles were excluded, leaving 10 articles that met inclusion criteria and were included for analysis. CONCLUSION: Weighted-implement training increased pitching velocity in the majority of the included studies. However, the quality of available evidence was determined to be very poor, and there was marked heterogeneity in training protocols, ball weights, and study populations. There was inadequate evidence reported to determine the risk of injury with this type of training.