Effect of Weighted Vest at 0%, 5% and 10% of Body Mass on Gasometry Biomarkers and Performance during a Rectangular Test in Trained Trail Runners

Trail runners (TRs) must carry an extra load of equipment, food (bars and gels) and liquids, to delay the anticipation of fatigue and dehydration during their competitions. Therefore, we aimed to evaluate how an extra load can influence the metabolic level. Thirteen well-trained trail runners performed a randomized crossover study (total <i>n</i> = 39), completing three treadmill running sessions with a weighted vest of 0%, 5% and 10% of their body mass during a combined test (rectangular test + ramp test). In addition, biomarkers of oxygen metabolism, acid-base and electrolyte status pre-, during and post-test, as well as the rectangular from capillary blood of the finger and time to exhaustion, were analyzed. Repeated-measures ANOVA showed no significant difference between conditions for any of the analyzed biomarkers of blood gas. However, one-way ANOVA showed a significant difference in trial duration between conditions (<i>p</i> ≤ 0.001). Tukey's post hoc analysis observed a significant decrease in time to exhaustion in the weighted vest of 10% compared to 0% (<i>p</i> ≤ 0.001) and 5% (<i>p</i> ≤ 0.01) and 5% compared to 0% (<i>p</i> = 0.030). In addition, repeated-measures ANOVA detected a significant difference in pH in the group x time interaction (<i>p</i> = 0.035). Our results show that increasing the weighted vest (5% and 10%) anticipates fatigue in runners trained in TR. In addition, increasing the load decreased pH by a smaller magnitude at 10% compared to 0% and 5% at the end of the exercise protocol.