Cardio performed after resistance exercise increased genes for muscle tissue breakdown. Muscle breakdown genes were elevated (atrogin, 21 percent and MuRF mRNA, 53 percent) when cycling was performed subsequent to circuit training workouts. Previous studies showed that following a single bout of endurance exercise, atrogin and MuRF mRNA (genes for muscle tissue breakdown) were elevated. Thus, the results indicate that endurance activity after resistance training may have the capacity to exacerbate genes for catabolism and subsequent protein degradation.
Consequently, when resistance exercise is undertaken after endurance exercise, up regulation of ubiquitin ligase expression may be suppressed. Moreover, PGC-1-alpha mRNA— a gene that turns ‘on’ an aerobic phenotype— was elevated when cycling preceded resistance exercise.
The results indicate that endurance activity prior to lifting weights exercise may diminish anabolic response, while endurance activity after resistance exercise may exacerbate inflammation and protein degradation. AMPK has beentermed a metabolic ‘master controller’ activated by exercise and changes in glycogen content in skeletal muscle. AMPKactivation was not different 15 minutes after each successive exercise bout.
However, AMPK aboveresting baseline was higher 3 hours after cycling was done after resistanc eexercise, indicating metabolic stress may have been exacerbated when endurance exercise was performed subsequent to resistance exercise. Build and burn at the same time.
The results provide support for the contention that (acute) combination of cardio and resistance exercise training back-to-back does not promote optimal activation of anabolic pathways. Thus, undertaking both resistance exercise/cardio together in close proximity influences the acute molecular profile and likely exacerbates acute ‘interference’ of key anabolic-signaling pathways.