ASH Test Insights on Early RFD and Peak Force in Baseball
Available in:
EN
Study Information
Ashworth, B., Hank, M., Khaiyat, O., Coyles, G., Fallon Verbruggen, F., Zemkova, E., Zahalka, F., & Maly, T. (2025). Early rate of force development and maximal strength at different positions of the Athletic Shoulder Test in baseball players. Sports, 13(9), 300.
https://doi.org/10.3390/sports13090300
Purpose of the Study
This study aimed to compare peak force and early rate of force development (RFD) at three shoulder abduction angles in the Athletic Shoulder (ASH) test in elite baseball players. The goal was to determine which position best reflects maximal and explosive strength capacity, and to assess the reliability of these metrics for performance profiling, rehabilitation and return-to-play decisions.
Methods and Key Findings
Seventeen elite male baseball players from the Czech national baseball team participated in this study. Testing was conducted using ForceDecks, which was used to collect force-time data at a sampling frequency of 1,000Hz. Each athlete performed the Athletic Shoulder (ASH) test in three standardized shoulder positions:
Each athlete completed three maximal isometric contractions in each shoulder position using their dominant arm. Athletes were tested in a prone position on the floor, and standardized instructions were provided to ensure consistent technique. The force data were filtered and analyzed to determine peak force and early RFD, which was defined as the change in force within the first 100 milliseconds (ms) of contraction (RFD 100ms).
To assess the reliability of the measurements, intraclass correlation coefficients (ICCs), coefficients of variation (CoV), standard error of measurement (SEM), smallest worthwhile change (SWC) and minimal detectable change (MDC) were calculated.
Key findings include:
- ISO-I produced significantly higher peak force (mean ± standard deviation = 182 ± 41N) and early RFD (545 N/s) compared to ISO-Y (139 ± 28 N; 305 N/s) and ISO-T (137 ± 31 N; 340 N/s).
- ISO-Y and ISO-T showed similar results, with peak forces of 139 ± 28 N and 137 ± 31 N, and early RFDs of 305 N/s and 340 N/s, with no statistically significant differences between them.
- Peak force demonstrated excellent reliability across all positions (ICC = 0.86-0.93).
- Early RFD showed moderate to good reliability (ICC = 0.75-0.81).
- SWC reached ~4% for peak force and ~14-19% for early RFD.
- MDC demonstrated ~15% for peak force and 43-75% for early RFD.
Among the tested positions, ISO-I proved the most sensitive for detecting shoulder strength and explosiveness. Early RFD also emerged as a valuable marker of fatigue and explosive capacity, although it requires consistent testing protocols due to higher variability.
VALD’s Solution
By including all three positions as preset test types, ForceDecks offers a dependable method for measuring peak force and early RFD during the ASH test, with results aligning with reliability benchmarks from previous ForceDecks research. This enables practitioners to perform repeatable upper-body isometric testing, particularly in athletes who rely on strong overhead performance.
ForceDecks helps integrate reliable upper-body testing into athlete monitoring programs, guiding training, rehabilitation and workload management.
To learn more about applying VALD’s human measurement technology to shoulder testing, rehabilitation and return-to-play decisions, download our Practitioner’s Guide to Shoulders or get in touch with our team. To explore additional ASH test research, see this study.
