Cardio Can BOOST Your Gains?! Do it Before Weights and be Rewarded With 28% Increased Fiber Size & VO2 Gains

It may be important that the subjects cycled, because a recent review of the potential interference of cardio w/ strength training shows that cycling is the least likely to affect your gains (Murach. 2016).

In previous articles at the SuppVersity, I have written about the still ubiquitous concern that cardio training (or aerobic training, in general) could hamper your size and strength gains - a fear that is, unless you overdo it, unwarranted (learn more about HIIT& "regular" cardio training).

Now, a recent study from the Mid Sweden University shows that the opposite could be the case, i.e. that the hypertrophy response to exercise can actually be stimulated by combining resistance training not just with "cardio", but with "cardio" (=continuous cycling) and HIIT - at least if it's done not after, but before resistance training.
The authors of the study, Zuzanna Kazior, Sarah J. Willis, Marcus Moberg, William Apró, José A. L. Calbet, Hans-Christer Holmberg, andn Eva Blomstrand were (just like you?) unhappy with the contradictory outcomes of existing studies on the effect of endurance exercise on the anabolic response to strength training. Accordingly, they designed a study to "re-investigated this issue, focusing on training effects on indicators of protein synthesis and degradation" (Kazior. 2016).

Figure 1: Overview of the resistance (top) and cardio training (bottom) protocols in the study at hand (Kazior. 2016).

In said study, two groups of previously not regularly trained male subjects performed 7 weeks of resistance exercise alone (R; n = 7) or in combination with preceding endurance exercise, including both continuous and interval cycling (ER; n = 9). You can see the exact protocols in Figure 1, with the resistance training part being on the top and the endurance / HIIT part on the bottom (the number of training sessions in the ER and R group were identical; importantly, the endurance training was performed before the resistance training and included an extra 5-min warm-up + cool-down before and after the E-part.
Biopsies were taken from the lateral part of m. quadriceps, i.e., the vastus lateralis, both before and after 7 weeks of training. To ensure the results were not messed up, ...

"[t]he subjects were instructed to refrain from training for 2 days prior to the pre-training biopsies and the post-training biopsies were taken approximately 2 to 3 days after the final session in 15 subjects, but in one subject the post-training biopsy was taken 90 hours after the final session. During this period the subjects also refrained from training" (Kazior. 2016).

All data are expressed as means ± SD and were checked for normal distribution before performing parametric statistical analyses. A two-way repeated measures ANOVA (time, group) was applied to evaluate and compare the effect of training in the R and ER groups. When the ANOVA showed a significant main effect or interaction between time and group, Fisher’s LSD post hoc test was applied to identify where the differences occurred. A P-value <0.05 was considered to be statistically significant.

Figure 2: Levels of proteins in the Akt signaling pathway before and after 7 weeks of training. (A) Akt, (B) mTOR and (C) S6K1 in skeletal muscle before (Pre) and after (Post) 7 weeks of strength training only (R) or combined endurance and resistance exercise (ER). Representative immunoblots from two subjects. *P < 0.05 for Post vs. Pre (Kazior. 2016).

While similar increases in leg-press 1 repetition maximum (30%; P<0.05) were observed in both groups, irrespective of the maximal muscle gains - a discrepancy of which the scientists say that it "suggests that the improvement in maximal strength (1RM) observed following our relatively short 7-week period of training is due largely to neuromuscular adaptation" (Kazior. 2016), the scientists observed a striking and highly significant difference between the changes of the subject's maximal oxygen uptake (a marker of cardiovascular fitness) in the two groups. As you may already have expected, the latter was elevated (8%; P<0.05) only in the ER group, while the strength training only group saw no increase in this important fitness marker.

Figure 3: Pre- vs. post changes in fiber are and capillary density in both groups (Kazior. 2016).

And what about the gains? As far as those were concerned, Kazior et al. observed significantly larger increases in the ER training group as well. More specifically, the ER group saw gains in both, the areas of both type I and type II fibers. The R protocol, on the other hand, increased only the area of the type II fibers, which is why it is not exactly surprising that the mean fiber area increased by 28% (P<0.05) in the ER group, whereas no significant increase was observed in the R group - a difference that appears to be in line with the expression of the anabolic proteins Akt and mTOR, which were both enhanced in the ER group, whereas only the level of mTOR was elevated following R training. The scientists further analyses showed that...

"[the t]raining-induced alterations in the levels of both Akt and mTOR [both anabolic] protein were correlated to changes in type I fiber area (r = 0.55–0.61, P<0.05), as well as mean fiber area (r = 0.55–0.61, P<0.05), reflecting the important role played by these proteins in connection with muscle hypertrophy. Both training regimes reduced the level of MAFbx protein (P<0.05) and tended to elevate that of MuRF-1 [both catabolic]" (Kazior. 2016).

In view of these findings, it is only logical that the authors conclude that "the present findings indicate that the larger hypertrophy observed in the ER group is due more to pronounced stimulation of anabolic rather than inhibition of catabolic processes" (Kazio. 2016) - irrespective of the fact that they cannot tell for sure what it was that triggered these practically relevant differences.
References:

• Børsheim, Elisabet, et al. "Effect of carbohydrate intake on net muscle protein synthesis during recovery from resistance exercise." Journal of Applied Physiology 96.2 (2004): 674-678.
• Kazior Z, Willis SJ, Moberg M, Apró W, Calbet JAL, Holmberg H-C, et al. "Endurance Exercise Enhances the Effect of Strength Training on Muscle Fiber Size and Protein Expression of Akt and mTOR." PLoS ONE 11.2 (2016) : e0149082. doi:10.1371/journal.pone.0149082
• Koopman, René, et al. "Coingestion of carbohydrate with protein does not further augment postexercise muscle protein synthesis." American Journal of Physiology-Endocrinology and Metabolism 293.3 (2007): E833-E842.
• Murach, Kevin A., and James R. Bagley. "Skeletal Muscle Hypertrophy with Concurrent Exercise Training: Contrary Evidence for an Interference Effect." Sports Medicine (2016): 1-11.
• Rosa C, Vilaça-Alves J, Fernandes HM, Saavedra FJ, Pinto RS, Machado Dos Reis V. "Order effects of combined strength and endurance training on testosterone, cortisol, growth hormone and IGFBP-3 in concurrent-trained men". J Strength Cond Res. (2014): Jul 15 Ahead of Print. 
• West, Daniel WD, and Stuart M. Phillips. "Associations of exercise-induced hormone profiles and gains in strength and hypertrophy in a large cohort after weight training." European journal of applied physiology 112.7 (2012): 2693-2702.