Title: Identifying Reliable and Relatable Force–Time Metrics in Athletes—Considerations for the Isometric Mid-Thigh Pull and Countermovement Jump
Authors: Justin J Merrigan, Jason D Stone, W Guy Hornsby and Joshua A Hagen.
Questions: Are Force-Time metrics in a Countermovement Jump (CMJ) and Isometric Mid-Thigh Pull test reliable (IMTP)? Are there Force Time metrics from each test type that are related?
Key Takeaways: In non-familiarised athletes, across 2 testing sessions in a one day, most Force-Time metrics were seen to be reliable. Some RFD metrics in both CMJ and IMTP tests along with some Net Force metrics in IMTP testing had a reliability outside predetermined levels (ICC=>0.80 & CV=<10%). There are moderate strength relationships between Concentric Mean Power, Jump Height and RSI-modified with Force at 100-200ms and Peak Force. These results should be treated with caution due the design of the study, which did not allow for familiarization and fatigue may have influenced force production capabilities of the athletes.
Summary: 112 athletes across 5 NCAA Division 1 Sports (Cheer n=18, Cross-Country n=17, Diving n=10, Rowing n=3 & T+F n=17) and Club Weightlifting (n=16) completed 2 maximal CMJ’s and then 2 Maximal IMTPs. Athletes completed this twice in a day, in different times in their competitive season to assess inter-session reliability of Force-Time metrics. Athletes also completed a standardised warm up prior to each session, that used arbitrarily assigned loads, rather than personalised prescriptions.
- In a CMJ, it seems that RFD measures, particularly in the Eccentric direction have some level of unreliability.
- In an IMTP, RFD measures in the first 150ms seem to have some level of unreliability
- Rate of Power Development may be better for monitoring than RFD
- CMJ still has a number of reliable metrics, particularly relating to Force, Power, Duration and Jump Height.