Paulo H.C. Mesquita, Joshua S. Godwin, Bradley A. Ruple, Casey L. Sexton, Mason C. McIntosh, Shelby C. Osburn, Breanna J. Mueller, Nicholas Kontos, Cleiton A. Libardi, Kaelin C. Young, Michael D. Roberts, Andreas N. Kavazis, FACSM. Auburn University, Auburn, AL.

BACKGROUND: While resistance training (RT) has long been appreciated for enhancing muscle mass and strength, it is widely underappreciated and under-utilized by endurance athletes and practitioners. However, several studies have shown beneficial effects of RT on endurance performance, which is usually linked to an improvement of running economy through neuromuscular adaptations. Emerging evidence highlights that RT may also promote positive mitochondrial adaptations, which could ultimately enhance endurance performance. Even though there are several studies investigating the effects of concurrent training, to the best of our knowledge, no study to date has investigated the effects of performing a block of RT-only before initiating endurance training (ET)-only. Therefore, the goal of the present study was to investigate the effects of RT on adaptations to subsequent ET. METHODS: 23 young untrained males were recruited and divided into two groups: 1) ET-only (n=12), which performed 7 weeks of high-intensity interval training; 2) RT+ET (n=11), which performed 7 weeks of RT twice weekly before initiating 7 weeks of the same endurance training performed by ET-only. All participants performed a maximal oxygen uptake test on a treadmill for determination of VO2max and speed at onset of blood lactate accumulation (OBLA) before (PRE) and after (POST) ET. Furthermore, muscle biopsies were obtained from participants’ vastus lateralis at PRE and POST and used to determine the levels of proteins involved in mitochondrial remodeling. RESULTS: Both groups significantly increased VO2max and speed at OBLA (p<0.001) similarly. Protein levels of mitochondrial complexes I, II, and III, and Mitofusin 2 (Mfn2) increased, while Parkin decreased similarly in both groups (main effect of time, p<0.05). Significant interactions were found for complex IV (ET-only (PRE < POST), p=0.039) and PGC-1α (ETonly-POST > RT+ET-POST, p=0.001). CONCLUSIONS: Our results suggest that performing RT prior to ET had no additional benefit on mitochondrial and endurance performance adaptations to ET in young untrained males. Participant compensation as well as select reagents related to analyses presented herein were funded by a grant awarded by National Strength and Conditioning Association Foundation to Paulo H.C. Mesquita.

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