Author(s): WU, C.Y., LEE, H., Institution: NATIONAL TAIWAN NORMAL UNIVERSITY, Country: TAIWAN, Abstract-ID: 1518

INTRODUCTION:
Rate of force development (RFD) is crucial for explosive movements in sports and daily living. The countermovement jump (CMJ), squat jump (SJ), and isometric mid-thigh pull (IMTP) are commonly used to evaluate lower limb explosive strength. The CMJ assesses stretch-shortening capabilities while the SJ isolates concentric action. Isometric RFD assessments also provide valuable insight into an individuals capacity to generate force rapidly. Comparing isometric RFD from these tasks can provide insight into differences in maximal strength and explosive performance. This study aimed to investigate differences in isometric rate and force development during the CMJ, SJ, and IMTP.
METHODS:
Three healthy men aged 22-24 years with sports experience participated in the study. Isometric mid-thigh pull, countermovement jump, and squat jump tests were conducted using Bioware force plates. Each participant performed three maximal trials of each test. Body weight standardization scaling was applied. From the force-time curves, peak force, peak rate of force development, and force development rates at different time intervals (0-50, 50-100, 100-150, 150-200 ms) were calculated. Jump height and center of mass displacement were also obtained from the countermovement and squat jumps.
RESULTS:
The results showed jump heights were the greatest in the countermovement jump with arm swing (0.38 ± 0.02 m), followed by the countermovement jump (0.33 ± 0.05 m) and the squat jump (0.30 ± 0.02 m). Force peaks were the greatest in the isometric mid-thigh pull (1910 ± 77.2 N), followed by the countermovement jump (1510 ± 209.9 N), the countermovement jump with arm swing (1408 ± 114.1 N), and the squat jump (1135 ± 105.8 N). Rate of force development (RFD) peaks were the greatest in the countermovement jump (7765 ± 2225 N/s), followed by the countermovement jump with arm swing (7485 ± 1016 N/s), the isometric mid-thigh pull (6016 ± 4172 N/s), and the squat jump (4728 ± 1001 N/s).
CONCLUSION:
Overall, the results showed that the countermovement jump, especially with an arm swing, produced the greatest rate of force development compared to the other exercises tested. This indicates that dynamic stretch-shortening cycle movements like the countermovement jump are more effective at enhancing rapid force production than concentric-only exercises such as the squat jump or isometric exercises like the mid-thigh pull. These findings can inform training program design for athletes and sports requiring explosive force generation. However, the small sample size in this study means the accuracy and generalizability of these results need to be confirmed through additional research. Future studies should aim to replicate these findings using larger sample sizes.