Effects of a 30 K Military Loaded Carriage on the Neuromuscular System in Spanish Army Marines

Infantry soldiers must cover long distances carrying heavy and bulky combat equipment. Since the beginning of their training, Spanish Marines have undergone this characteristic and demanding test. However, little is known about its effects on neuromuscular function and recovery in the days following the test. Twenty-six Spanish Marines completed the test, three of whom suffered injuries and had to withdraw from the study, resulting in a final sample of twenty-three Marines. These participants underwent evaluations before (pre), immediately after (post), and 24 and 48 h post-exercise, following a 30 km endurance march carrying their 34 kg combat equipment. A repeated-measures ANOVA, paired-samples <i>t</i>-test, and effect size (ES) analysis were conducted; the results are presented as mean ± SD. The significance level was set at <i>p</i> ≤ 0.05. The variables and <i>p</i>-values of changes over time are presented. Isometric mid-thigh pull (IMTP) (<i>p</i> = 0.004), countermovement jump (CMJ) (<i>p</i> ≤ 0.001), rating of fatigue scale (ROF) (<i>p</i> ≤ 0.001), maximum pull-ups in two minutes (PUmax) (<i>p</i> ≤ 0.001), body mass (BM) (<i>p</i> ≤ 0.001), hand grip strength (HGS): dominant (<i>p</i> = 0.180) and non-dominant (<i>p</i> = 0.616), and incident reports (IRPE) showed a significant increase over time and between the first 10 km and last 5 km in fatigue, muscle pain, joint pain, shortness of breath, excessive sweating (<i>p</i> ≤ 0.001), and muscle tremors (<i>p</i> = 0.028), except for palpitations (<i>p</i> = 0.189). In conclusion, the results indicate that the test had a significant impact on neuromuscular function, with no recovery observed in overall strength and lower limb power after 48 h, even though their perceived fatigue decreased substantially. The resilient spirit of operational military units and their philosophy of always being ready for combat could increase the injury rate.