The Relationship Between Isometric Midthigh Pull Force-Time Characteristics and 2-km Load-Carrying Performance in Trained British Army Soldiers.

Nevin, JP, Bowling, K, Cousens, C, Bambrough, R, and Ramsdale, M. The relationship between isometric midthigh pull force-time characteristics and 2-km load-carrying performance in trained British army soldiers. J Strength Cond Res 38(2): 360-366, 2024-Load carriage is a fundamental military occupational task. As such, the aim of this study was to assess the relationship between isometric force-time characteristics and loaded march performance. Furthermore, this study aimed to investigate the relationship between isometric force-time characteristics and standing long jump (SLJ) performance. Thirty-nine, full-trained, male British Army infantry soldiers (age 31 ± 6.1 years; height 176 ± 7.3 cm; body mass 85.8 ± 11.5 kg) performed three isometric midthigh pull trials, three SLJ trials, and a 2-km loaded march carrying an external load of 25 kg. Both the isometric midthigh pull test (intraclass correlation coefficient [ICC] 0.965) and SLJ (ICC 0.916) demonstrated excellent reliability. Relationships between all variables were assessed using Pearson's correlation coefficient. Isometric peak force (r = -0.059), relative peak force (r = -0.135), and rate of force development (r = -0.162) displayed a small correlation with loaded march time to completion. However, isometric relative peak force displayed a large relationship with SLJ performance (r = 0.545; p = <0.01). Our data demonstrate that isometric lower-limb strength measures account for <2% of the total variance observed in 2-km loaded march performance. As such, the use of isometric lower-limb force-time characteristics as a proxy measure of load-carrying ability should be questioned. However, relative isometric strength seems to demonstrate a significant relationship with SLJ performance. As such, isometric testing may have utility in regard to assessing explosive strength, monitoring neuromuscular fatigue, and assessing training readiness in military populations.