Relationship Between Dynamic Strength Index and Early Force Production of Isometric Mid-Thigh Pull

Dynamic strength index (DSI) and percentage of isometric mid-thigh pull (IMTP) peak force (PF) produced during early epoch, expressed as a percentage of net PF (%PF), are useful strength assessments to evaluate an athlete’s training status. Due to the similarity in diagnosis that the DSI ratio and %PF provides, it is not known whether %PF can reflect closely to an athlete’s DSI ratio. Therefore, the aim of this study is to establish the relationship between DSI and %PF.

Thirty-seven national athletes (age = 22.9 ± 3.12 years; height = 1.73 ± 0.08 m; body mass = 69.1 ± 10.68 kg) were recruited for this study. Participants performed the countermovement jump test (CMJ) and isometric mid-thigh pull (IMTP) during both familiarisation and testing sessions. IMTP and CMJ force–time variables were collected to compute the DSI ratio and %PF for analysis.

Trivial to small correlations between DSI and %PF was observed across all epochs (50 ms: r = 0.09, 95% CI −0.241–0.402, P > 0.598; 100 ms: r =−0.021, 95% CI−0.343–0.305, P > 0.9; 150 ms: r =−0.058, 95% CI−0.375–0.271, P > 0.734; 200 ms: r = 0.126, 95% CI−0.207–0.432, P > 0.458).

DSI ratio and %PF are two distinct monitoring tools and not interchangeable. Both DSI and the percentage of IMTP net PF at early time points are useful in evaluating athletes’ previous training phases and current physical performance.