Does Cardio Prevent Muscle Growth?

Does Cardio Prevent Muscle Growth?

For years there has been talk that doing both cardio and resistance exercise at the same time will halt your muscle growth gains. It has been previously thought by researchers that combining cardio and resistance exercise into a concurrent training program leads to suboptimal adaptations. For example, a previous research study found that the gains in lean muscle mass were less when combined resistance exercise and cardio were performed, whereas the group that did resistance exercise only gained greater strength and lean muscle mass1.

Some researchers have proposed that the excessive volume of training when both aerobic exercise and resistance training are employed together causes this interference effect. The researchers wanted to investigate whether a moderate volume of aerobic exercise and resistance training combined into the same training session is sufficient to lead to significant changes in physical fitness, body composition, and blood lipids. They also wanted to investigate whether there was an order effect in these variables. Researchers had 42 males participate in the 24-week study. The participants performed either supervised cardio, immediately followed by strength training, or vice versa (two to three combined cardio and resistance sessions per week). The researchers investigated whether the immediate anabolic effects of one single exercise session would differ between the two training orders and whether these differences would be reflected in the physiological adaptations induced by six months of training. Before and after the trial, the researchers measured physical fitness and body composition. The aerobic exercise program involved a cycle ergometer, and the resistance-training program included exercises for all major muscle groups but had a focus on the lower body. The overall duration of the strength workout within each concurrent training session was 30–50 minutes, and the overall training session involving both endurance and strength training sessions was 60–100 minutes.

Despite differences in recovery time, training order did not affect long-term adaptations.

The anabolic responses of one single training session seemed to be less favorable in the training group starting with cardio. This was especially indicated by reduced concentrations of serum testosterone during recovery for up to two days, which may possibly be detrimental to optimal muscle growth and strength development.

However, this initial difference between the recovery times was no longer observed after the 24-week training period, and both groups actually increased physical performance and muscle size to about a similar extent. 1RM strength, total lean mass, and muscle cross-sectional area increased similarly in both groups at Week 24 to a similar extent. The amount and/or frequency of training may play a key role.

Based on these findings, the training order of combined cardio and resistance training does not seem to have an effect on biological adaptations. Performing two to three combined cardio- and resistance training sessions per week, of 90–120 minutes each, does not lead to differences in the adaptations of overall fitness and body composition between the two training orders. However, whether the present results may be ultimately applied to fitness enthusiasts with a longer training history or athletes, typically training a much greater amount, remains to be investigated.

The most recent study examined whether aerobic exercise combined with resistance exercise suppressed myostatin levles. This study compared the effects of concurrent training, strength training, and interval training on the muscle fiber cross-sectional area response, and on the expression of selected genes involved in the myostatin (MSTN) signaling mRNA levels. Thirty-seven physically active men were randomly divided into 4 groups: concurrent training, strength training, and interval training and control group and underwent an 8-week training period. Vastus lateralis biopsy muscle samples were obtained at baseline and 48 hours after the last training session. Muscle fiber CSA, selected genes expression, and maximum dynamic ST (1 repetition maximum) were evaluated before and after training. At the end of the study, myostatin genes levels remained unchanged across time and groups.

These findings are suggestive that myostatin and their regulatory genes are not affected by concurrent aerobic and strenght training, so it seesm that doing cardio and strength training together is not going to impact changes in muscle mass.

1. Babcock, L, Escano, M, D’Lugos, A, Todd, K, Murach, K, and Luden, N. Concurrent aerobic exercise interferes with the satellite cell response to acute resistance exercise. Am. J. Physiol. Regul. Integr. Comp. Physiol. 302: 2012.

2. Wilson JM, Marin PJ, Rhea MR, Wilson SM, Loenneke JP, Anderson JC. Concurrent training: a meta-analysis examining interference of aerobic and resistance exercises. J Strength Cond Res. 2012 Aug;26(8):2293-307.

3.) de Souza EO, Tricoli V, Aoki MS, Roschel H, Brum PC, Bacurau AV, Silva-Batista C, Wilson JM, Neves M Jr, Soares AG, Ugrinowitsch C. Effects of concurrent strength and endurance training on genes related to myostatin signaling pathway and muscle fiber responses. J Strength Cond Res. 2014 Nov;28(11):3215-23.