Acute molecular responses in untrained and trained muscle subjected to aerobic and resistance exercise training versus resistance training alone R. Fernandez-Gonzalo, 1,2 T. R. Lundberg 3 and P. A. Tesch 1,3 1 Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden 2 Department of Laboratory Medicine, Division of Clinical Physiology, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden 3 Department of Health Sciences, Mid Sweden University, O ¨ stersund, Sweden Received 27 July 2013, revision requested 22 August 2013, revision received 2 September 2013, accepted 23 September 2013 Correspondence: R. Fernandez- Gonzalo, PhD, Department of Physiology & Pharmacology, Karolinska Institutet, 171 77 Stockholm, Sweden. E-mail: rodrigo.fernandez.gonzalo @ki.se Abstract Aim: This study assessed and compared acute muscle molecular responses before and after 5-week training, employing either aerobic (AE) and resis- tance exercise (RE) or RE only. Methods: Ten men performed one-legged RE, while the contralateral limb performed AE followed by RE 6 h later (AE+RE). Before (untrained) and after (trained) the intervention, acute bouts of RE were performed with or without preceding AE. Biopsies were obtained from m. vastus lateralis of each leg pre- and 3 h post-RE to determine mRNA levels of VEGF, PGC- 1a, MuRF-1, atrogin-1, myostatin and phosphorylation of mTOR, p70S6K, rpS6 and eEF2. Results: PGC-1a and VEGF expression increased (P < 0.05) after acute RE in the untrained, but not the trained state. These markers showed greater response after AE+RE than RE in either condition. Myostatin was lower after AE+RE than RE, both before and after training. AE+RE showed higher MuRF-1 and atrogin-1 expression than RE in the untrained, not the trained state. Exercise increased (P < 0.05) p70S6K phosphorylation both before and after training, yet this increase tended to be more prominent for AE+RE than RE before training. Phosphorylation of p70S6K was greater in trained muscle. Changes in these markers did not correlate with exercise-induced alterations in strength or muscle size. Conclusion: Concurrent exercise in untrained skeletal muscle prompts global molecular responses consistent with resulting whole muscle adapta- tions. Yet, training blunts the more robust anabolic response shown after AE+RE compared with RE. This study challenges the concept that single molecular markers could predict training-induced changes in muscle size or strength. Keywords concurrent exercise, gene expression, human skeletal muscle, mammalian target of rapamycin, p70S6 kinase. It is generally held resistance (RE), but not aerobic (AE) exercise augments myofibrillar protein accretion to result in muscle hypertrophy consequent to chronic training (Kraemer et al. 1995, Coffey & Hawley 2007). However, we recently reported that an acute AE+RE insult prompted greater molecular ‘anabolic’ © 2013 Scandinavian Physiological Society. Published by John Wiley & Sons Ltd, doi: 10.1111/apha.12174 283 Acta Physiol 2013, 209, 283–294