The Effect of an Essential Amino Acid Supplement on Muscle Performance and Inflammation in an Animal Model of Overtraining

Background/Objectives: Overtraining (OT) syndrome occurs when an athlete’s training load exceeds the athlete’s ability to recover, leading to a performance decrement. The use of nutritional interventions to increase resiliency to OT is a topic of interest for maximizing performance adaptations. The purpose of this study was to determine whether an essential amino acid (EAA) supplementation administered intraperitoneally and orally can mitigate performance decrements and inflammatory responses in an animal model of resistance training-induced overtraining. Methods: Thirty-two C57BL/6J mice were randomly assigned to four groups (n = 8 per group). One group served as a control (CTL), while the other three groups performed a 5-week resistance training ladder climb program. One group trained three days per week for the duration of the program (RT), while the training frequency of the other two groups doubled to six days per week to cause the OT stress. One group of animals were provided with EAA (RTOEAA), while the other received a sham (RTO). Changes (∆) in maximal carrying load (MCL) were assessed. Results: RTO experienced a greater decrease in ∆MCL than RT (p = 0.002) and RTOEAA (p = 0.029). No differences (p = 0.254) were noted between RT and RTOEAA. In addition, TNF-α expression within the plantaris muscle was significantly elevated in RTO compared to all other groups. Significant decreases in the androgen receptor were also noted for RTO in the soleus compared to RT and CTL. Conclusions: Results demonstrated that EAA supplementation was able to increase resiliency and reduce the inflammatory response to the volume overload stress.