The Kneeling Isometric Plantar Flexor Test: Preliminary Reliability and Feasibility in Professional Youth Football

McMahon, John J.; Ripley, Nicholas J.; Comfort, Paul; Robles-Palazón, Francisco Javier; Fahey, Jack T.; Badby, Andrew J.; Bramah, Christopher

Abstract

Calf injuries are common in professional football; thus, the establishment of reliable and time-efficient methods of measuring the peak force capabilities of the plantar flexors with equipment that is accessible to football practitioners is valuable. In this study, we determined the preliminary reliability and feasibility of a new test, termed the kneeling isometric plantar flexion test (KIPFT), for footballers. Twenty-one male youth footballers (age = 17.8 ± 1.1 years, height = 182 ± 5 cm, weight = 77.6 ± 5.9 kg) from English League One football clubs completed three trials of the KIPFT on a wireless force plate at the end (2022–2023) and start (2023–2024) of the season. The within-session reliability of the peak force (relative to body weight) was good–excellent for both limbs and both occasions. On average, performance of the KIPFT took just over 1 min per limb and ~2 min to set up. The peak force values were larger for the non-dominant limbs only at the start versus the end of the season, but there were no between-limb differences. From these results, it was determined that (1) the KIPFT is feasible, (2) a minimum of 32 footballers would be required to establish its between-session reliability with ≥80% statistical power and (3) large-cohort normative data for the KIPFT may be best collected at the start of the football season.

Citation

McMahon, J. J., Ripley, N. J., Comfort, P., Robles-Palazón, F. J., Fahey, J. T., Badby, A. J., & Bramah, C. (2023). The Kneeling Isometric Plantar Flexor Test: Preliminary Reliability and Feasibility in Professional Youth Football. Journal of Functional Morphology and Kinesiology, 8(4), 164. https://doi.org/10.3390/jfmk8040164

• Journal Article Type: Article
• Acceptance Date: Nov 28, 2023
• Online Publication Date: Nov 30, 2023
• Publication Date: Nov 30, 2023
• Deposit Date: Dec 1, 2023
• Publicly Available Date: Dec 4, 2023
• Journal: Journal of Functional Morphology and Kinesiology
• Publisher: MDPI
• Peer Reviewed: Peer Reviewed
• Volume: 8
• Issue: 4
• Pages: 164
• DOI: https://doi.org/10.3390/jfmk8040164
• Keywords: soleus, maximal strength, soccer, injury, force plate, calf