Limiting fat increase "on mass": aerobic or interval exercises?

It is a complex, controversial issue. It's impossible to give an easy clear-cut answer. Those who want to build attractive shape at the stage of increasing “mass”, have to avoid gaining fatty tissue.

Even Arnold Schwarzenegger talked about it long time ago: ”I can only say one thing: don't increase your mass, that is, don't let yourself build large amount of body fat, which you will have to lose during preparation to competition. Bodybuilders rarely do that, because the heavier they are, the “bigger” they feel – but it's just an ilusion and the additional mass is not muscles, and it brings more bad than good”. [1]

Conclusion no. 1: “highly-calorific diet is not good if you flood yourself with fat”.

Yes, but... I gained so many kilos of “mass”?! Yes, you gained a lot of kilograms, but the presence of lean body mass is insignificant! In order to check your progress, measure the circumferences of arms, thighs, calves or chest – but... don't forget about the measurement of waistline and the pockets of fat – done in the same body parts at the same hour. Also the DEXA/DXA body content analysis may be useful, especially for sports people and those with obesity. Taking photos in similar conditions may show a lot, too. The increase of body mass itself means nothing. Drink a lot of water – the body mass will increase, sit in a sauna or limit the supply of carbohydrates – the weight will decrease very fast. Neither of these changes solves the problem – the percentage of body fat stays the same, as well as that of muscles.

Excessive amount of body fat destroys muscles – why? You change the hormonal environment, which is responsible for increasing muscle mass. You decrease the level of testosterone and the amount of estrogen increases (aromatization in the fatty tissue). According to the lates theories, the decrease of the amount of testosterone is connected with the phenomenon of intensive inflammation in the body fat, which also influences the production of testosterone in testicles (pro-inflammatory adipokines in fatty tissue [3]; some scientists call these factors adipocytokines [4]). A lot of adipokines (e.g. TNF-α and leptin) are being connected with the direct influence on the production of testosterone by men. Overeating influences insulin in negative way, the tissues become insulin resistant. The nutrients go straight to fat cells instead of muscles – this way you overload your pancreas. But that's not all... the influence on SHBG (sex hormone binding globulin) makes that there is more bound inactive testosterone.

Highly-calorific diet is reserved for two types of people:

  • extremely thin ones, who intake gigantic calorific surplus without adiposity,

  • men who use pharmaceuticals in various combinations (e.g. trenbolone, masteron, winstrol, rhGH/IGF-1, insulin, T3, GHRP clenbuterol, ephedrine, salbutamol).

Conclusion no. 2: “if you gain a lot of fatty tissue in the stage of building mass – look for the reasons in you diet”.

Of course, you can try to balance the mistakes made in the kitchen with exhausting interval or aerobic workouts – but... here comes a huge problem. Aerobic exercises and intervals disturb the post-workout recovery. In one of the studies [2] the researchers measured the cooperation of running and resistance training. 16 men and 8 women were matched to the groups of collateral aerobic and resistance training (CCT) or resistance training. The CCT group was running every day and it had resistance training every other day. It was also checked how exhausting the endurance training would be without the gym.

What were the results in the resistance-aerobic training group?

  • The significant dicrease of the ability of continuing the aerobic training was observed (time to exhaustion),

  • the maximal voluntary contraction (MVC) decreased,

  • the significant increase of the RMS (muscle soreness) and RMF (muscle fatigue) was observed.


Resistance training may make the aerobic workout effectiveness worse.

Further research bring even more detailed observations – the biggest influence on worsening the time of running until exhaustion have FBW and those of the lower body. The low-intensity FBW did not influence the performance of the runners [5]. The tests were run after 6-hour rest. However, you should know, that for untrained people even the resistance and interval sessions (or aerobic ones) done on the same day of the week don't influence the muscle mass increase. Paradoxically, for untrained people, the endurance training done on the same day as resistance training seemed to increase the muscle mass! But... I have to add, that in this case interval training was used – what seems to explain the paradox well [6].

42 students were assigned to one of the 3 groups:

  • CDER (Concurrent Distinct Endurance-Resistance) – 2 resistance workouts and 2 running interval workouts on different days, i.e. 4 sessions a week,

  • CPER (Concurrent Parallel Endurance-Resistance) – 2 resistance workouts and 2 running interval workouts on the same days, i.e. 2 complex sessions a week,

  • “no training” - control group, no exercises.

The resistance training included:

  • barbell press,

  • cable lat pulldown,

  • cable biceps curl,

  • leg press,

  • leg curl,

  • seated leg extension.

The endurance training included:

  • 20-minute interval – various distances with the intensity of 70% of HR max, after 12 weeks the interval session took 45 minutes!

  • The intensity was increased, the distances of 100 and 200 m were used (three times longer rest, passive one), 400 and 600 m (400 or 600 m fast, then 800 or 1200 m at the level of 40% of HR max – active rest), and 2 and 2.4 km (passive rest 1 to 1.3).

For example, in that experiment:

  • the CDER group (2 resistance workouts and 2 running interval workouts on different days) observed the increase of body mass by averagely 0.5%,

  • the CPER group (2 resistance workouts and 2 running interval workouts on the same days) observed the increase of body mass by averagely 1.7%,

  • the lean body mass in the CDER group (resistance and running sessions on different days) increased by 1.8%, whereas, in the CPER group (resistance and running sessions on the same day) increased by 2.7%,

  • the lean body mass decreased in the control group by 0.2% (the loss of muscle mass because of doing nothing),

  • bench press – the CPER group (resistance and running sessions on the same day) increased by 12.3% (from 77.10 +/- 12.74kg to 86.60 +/- 15.92 kg), CDER (resistance and running sessions on different days) improved by 5.8% (from 78+/-20.21 kg to 82.57 +/- 18.47 kg),

  • squats – the CPER group improved by 26% (from 118.35 +/- 21.9 kg to 149.22 +/-40.89 kg), CDER +33.1% (from 107.6 +/- 28.61 kg to 143.32 +/- 35.07 kg),

  • the time of running for 60 m was similar in both training groups,

  • the improvement of pull-ups – in favour of the group with two workouts in one day.

Conclusions and practical application:

  • don't try to correct mistakes in the kitchen with workouts, look for the solution in limiting the supply of carbohydrates on the days without resistance training (e.g. rotating carbohydrates),

  • If you don't have to, don't use excessive interval or aerobic workout, it usually influences negatively building the power and muscle strength,

  • for many people large supply of carbohydrates is not a good solution, it's worth trying e.g. low-carb diet, it is especially important for the improvement of tolerance of carbohydrates (decreasing the insulin resistance),

  • limit the intake of carbohydrates, gainers (maltodextrin, glucose, fructose, dextrose) or other conditioners – it's the simple way to adipose,

  • get rid of sweetened beverages, e.g. energy drinks (more sugar than caffeine),

  • you may also limit the increase of fatty tissue efficiently by using interval training on the same days or on the days free from resistance training, however, you have to remember about worsening the results of resistance training (paradoxically, the beginners, as well as poorly-trained people will gain more from 2 sessions on the same day and they will not notice the loss of strength in squats, bench press or pull-ups, or slowing down the tempo of gaining muscle mass),

  • in one of the studies the explosive power increase (the parameter, which indicates how fast a person may produce the peak power) was observed only in the resistance training group, and because those were the poorly-trained people, during 21 weeks the circumference of thigh (quadriceps) increased more in the resistance-endurance group (+11%) comparing to men doing only resistance training (+6%) [8],

  • some studies mention about the negative influence of e.g. running on the strength training, whereas, for 44 women, independently from the fact if they used continuous running (aerobic), interval running (unaerobic), continuous ride on exercise bike, or resistance training only – including leg extension, bench press and legg pess, the local muscle endurance (max repetitions with the 70% load of maximal load) in barbell press, as well as in seated leg extension and the isometric and isokinetic peak power moment were similar in each group (workouts 2 x a week) [7],

  • when it comes to endurance, running on the days free from the gym is better (it was stated that the peak consumption of oxygen for women and men was significantly higher in the group with aerobic session on the days free from resistance training – men improved by 18 +/- 9%, women improved by 25 +/- 11%). In the group with endurance training first, then resistance training, men improved their results by 7 +/- 9%, whereas women by 12 +/- 12%. In the group of resistance training first, then endurance training, the improvement was 7 +/- 9% (men) and 10 +/- 8% (women) [9].

Try the following schemes:


  • GYM 4 sessions – up/down (e.g. MONDAY, TUESDAY, THURSDAY, FRIDAY) + 2 running sessions (e.g. after a light session for upper body on Monday and after a light session of legs on Friday, Tuesday – hard leg training, Thursday – hard upper body workout).

If it comes to the question in the title – if you train hard with resistance – aerobic exercises will be better – you may lack strength and willingness for intervals, but if you use quite light resistance training – interval sessions will be optimal – even within one workout. Light/hard – I mean the load over 90% of the maximal load in the strength-dynamic workout, or in short breaks between hard sessions in the volume training (e.g. GVT 10 x 10).

Sources: 1. Article by Ron Harris on MuscularDevelopment 2. The Acute Effect of Concurrent Training on Running Performance Over 6 Days. 3. Determinants of testosterone levels in human male obesity 4. 5. Eur J Sport Sci. 2014;14(2):107-15. doi: 10.1080/17461391.2012.726653. Epub 2012 Oct 3. The acute effects intensity and volume of strength training on running performance. 6. “Effects of concurrent exercise protocols on strength, aerobic power, flexibility and body composition” Kinesiology 43(2011) 2:155-162 7. Int J Sports Med. 2012 Aug;33(8):627-34. doi: 10.1055/s-0031-1299698. Epub 2012 May 4. Concurrent training with different aerobic exercises. 8. Int J Sports Med. 2012 Jun 15. [Epub ahead of print] Neuromuscular and Cardiovascular Adaptations During Concurrent Strength and Endurance Training in Untrained Men. 9. Cardiorespiratory Adaptations during Concurrent Aerobic and Strength Training in Men and Women