Plasma ammonium, blood lactate, and RPE as indicators of fatigue for three squat training protocols

Abstract

No accepted method for monitoring resistance exercise fatigue exists. Ammonium, lactate, and rating of perceived exertion (RPE) were measured for their utility in monitoring resistance exercise. Sixteen men (18-24 yrs.) participated in the study. Muscular endurance (ME), strength (STR), and hypertrophy (HYP) squat workouts were based on a one-repetition maximum squat. Protocols were performed at least 72 hours apart in random order. Work volume was equalized among protocols. Subjects reported RPE based on last set difficulty. Venous blood was obtained for ammonium and lactate analysis after five minutes of rest both before and after each workout. Differences among protocols were assessed by univariate ANOVA with Tukey post-hoc comparisons. Post exercise ammonium (p<.01) and lactate (p<.01) both increased from resting levels. However, no difference existed among protocols for post-exercise lactate (p=.10). A difference in post-exercise ammonium was found between the STR and ME protocols only (p=.01). Reported RPE differed between the HYP protocol and the STR (p=.04) and ME (p=.02) protocols, with no difference found between STR and ME (p=.97). Lactate levels appeared to correspond with total work volume whereas ammonium levels appeared to correspond with work density. Reported RPE appeared to be associated with both nervous system and metabolic stress.