Under some conditions athletes can build up more muscle mass by combining strength training with cardio training, than by doing strength training alone. Swedish sports scientists demonstrated this in a small human study, published in PLoS One.
Strength training and cardio training
If your total training volume gets too high, strength and cardio training can start to work against each other. The better trainers and sports scientists have known this for years, and meta-studies have now shown about how much cardio training strength athletes can add to their workouts without compromising their overall training results. A 20-minute cardio session three times a week should be no problem for strength athletes.
There are even a couple of studies that show that a moderate combination of strength and cardio training can help build up more lean body mass than doing strength training alone. [J Appl Physiol. 1998 Aug;85(2):695-700.] And yes: it sounds strange. But according to the human study that the Swedish sports scientists published in PLoS One, it is possible.
The researchers got sixteen healthy young men, who had never done weight training before, to work out three times a week. Over a period of seven weeks seven men did resistance training [R], while nine men did both cardio and resistance training [ER].
The strength training consisted of leg extensions only. [Yes, we agree, you can hardly call that resistance training]. The workout schedule for both groups is shown below.
The cardio schedule is shown below. The ER group did the cardio training before they started on their resistance workout. [A no doubt unnecessary warning: for most men and women who do serious resistance training, this cardio training schedule may be too much.]
Twenty minutes after completing the workout the subjects drank a shake containing 20 g whey. The ER group also got maltodextrin in their shake, to compensate for the calories burnt.
The combination of cardio and resistance training resulted in a stronger anabolic stimulus than that given by resistance training alone.
“The current investigation provides additional evidence that endurance exercise does not compromise the anabolic stimulus provided by subsequent strength training”, the Swedes concluded.
Endurance Exercise Enhances the Effect of Strength Training on Muscle Fiber Size and Protein Expression of Akt and mTOR
Reports concerning the effect of endurance exercise on the anabolic response to strength training have been contradictory. This study re-investigated this issue, focusing on training effects on indicators of protein synthesis and degradation. Two groups of 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). Muscle biopsies were taken before and after the training period. Similar increases in leg-press 1 repetition maximum (30%; P<0.05) were observed in both groups, whereas maximal oxygen uptake was elevated (8%; P<0.05) only in the ER group. The ER training enlarged the areas of both type I and type II fibers, whereas the R protocol increased only the type II fibers. The mean fiber area increased by 28% (P<0.05) in the ER group, whereas no significant increase was observed in the R group. Moreover, expression of Akt and mTOR protein was enhanced in the ER group, whereas only the level of mTOR was elevated following R training. Training-induced alterations in the levels of both Akt and mTOR 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. 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.